Commonwealth Edison 10-Q 30 Oct 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information	9 Months Ended
	Sep. 30, 2015shares
Entity Registrant Name	EXELON CORP
Entity Central Index Key	1,109,357
Document Type	10-Q
Document Period End Date	Sep. 30, 2015
Amendment Flag	false
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock Shares Outstanding	919,564,380
Exelon Generation Co L L C [Member]
Entity Registrant Name	EXELON GENERATION CO LLC
Entity Central Index Key	1,168,165
Entity Filer Category	Non-accelerated Filer
Commonwealth Edison Co [Member]
Entity Registrant Name	COMMONWEALTH EDISON CO
Entity Central Index Key	22,606
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	127,016,973
PECO Energy Co [Member]
Entity Registrant Name	PECO ENERGY CO
Entity Central Index Key	78,100
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	170,478,507
Baltimore Gas and Electric Company [Member]
Entity Registrant Name	BALTIMORE GAS AND ELECTRIC
Entity Central Index Key	9,466
Entity Filer Category	Non-accelerated Filer
Entity Common Stock Shares Outstanding	1,000

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Income (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014
Operating revenues [Abstract]
Operating revenues from affiliates	$ 2	[1]	$ 0	[1]	$ 3		$ 0
Total Revenues	7,401	[2]	6,912	[2]	22,746	[3]	20,173	[3]
Operating expenses
Purchased power and fuel	3,291		2,591		10,210		8,943
Purchased power and fuel from affiliates	0		57		0		456
Operating and maintenance	1,996		1,982		6,119		6,005
Depreciation and amortization	606		577		1,818		1,732
Taxes other than income	310		306		908		887
Total operating expenses	6,203		5,513		19,055		18,023
Equity in losses of unconsolidated affiliates			0		(3)		(20)
Gain (Loss) on Sale of Assets and Asset Impairment Charges	2		339		10		356
Gain on consolidation and acquisition of businesses	0		0				261
Operating income	1,200		1,738		3,701		2,747
Other income and (deductions)
Interest expense, net	(243)		(247)		(724)		(691)
Interest expense to affiliates	(10)		(11)		(31)		(31)
Other, net	(244)		16		(179)		346
Total other income and (deductions)	(497)		(242)		(934)		(376)
Income before income taxes	703		1,496		2,767		2,371
Income taxes	115		422		805		646
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions	(1)				(3)
Net income	587		1,074		1,959		1,725
Net income (loss) attributable to noncontrolling interest and preference stock dividends	(42)		81		0		121
Net income attributable to common shareholders	629		993		1,959		1,604
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost	(11)		(11)		(35)		(18)
Actuarial loss reclassified to periodic cost	55		38		165		109
Pension and non-pension postretirement benefit plans valuation adjustment	0		(8)		(29)		240
Unrealized gain (loss) on cash flow hedges	(3)		(19)		4		(92)
Unrealized gain (loss) on equity investments	0		(3)		0		8
Unrealized gain (loss) on foreign currency translation	(8)		(5)		(17)		(6)
Unrealized loss on marketable securities	(1)		(3)		0		(2)
Reversal of CENG equity method AOCI	0		0		0		(116)
Other comprehensive income (loss)	32		(11)		88	[4]	123	[4]
Comprehensive income	$ 619		$ 1,063		$ 2,047		$ 1,848
Average shares of common stock outstanding:
Average common shares outstanding — basic	913		861		879		860
Average common shares outstanding — diluted	915		863		883		863
Earnings per average common share:
Earnings per share - basic (in usd per share)	$ 0.69		$ 1.15		$ 2.23		$ 1.87
Earnings per average common share - diluted
Earnings per share - diluted (in usd per share)	0.69		1.15		2.22		1.86
Dividends per common share (in usd per share)	$ 0.31		$ 0.31		$ 0.93		$ 0.93
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Operating revenues	$ 4,562		$ 4,300		$ 14,270		$ 11,944
Operating revenues from affiliates	206		112		571		647
Total Revenues	4,768		4,412		14,841		12,591
Operating expenses
Purchased power and fuel from affiliates	3		59		11		476
Purchased power and fuel	2,516		1,821		7,789		6,595
Operating and maintenance	1,088		1,114		3,399		3,308
Operating and maintenance from affiliates	153		152		461		457
Depreciation and amortization	264		253		774		719
Taxes other than income	123		127		369		350
Total operating expenses	4,147		3,526		12,803		11,905
Equity in losses of unconsolidated affiliates			1		(4)		(20)
Gain (Loss) on Sale of Assets and Asset Impairment Charges	1		338		7		355
Gain on consolidation and acquisition of businesses	0		0		0		261
Operating income	622		1,225		2,045		1,282
Other income and (deductions)
Interest expense, net	(56)		(77)		(236)		(224)
Interest expense to affiliates	(12)		(12)		(33)		(37)
Other, net	(257)		4		(193)		306
Total other income and (deductions)	(325)		(85)		(462)		45
Income before income taxes	297		1,140		1,583		1,327
Income taxes	(36)		291		371		290
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions	(1)				(4)
Net income	332		849		1,208		1,037
Net income (loss) attributable to noncontrolling interests	(45)		78		(10)		111
Net income attributable to membership interest	377		771		1,218		926
Pension and non-pension postretirement benefit plans:
Unrealized gain (loss) on cash flow hedges	(3)		(16)		(7)		(86)
Unrealized gain (loss) on equity investments	0		(3)		0		8
Unrealized gain (loss) on foreign currency translation	(8)		(5)		(17)		(6)
Unrealized loss on marketable securities	(2)		(2)		0		(3)
Reversal of CENG equity method AOCI	0		0		0		(116)
Other comprehensive income (loss)	(13)		(26)		(24)	[4]	(203)	[4]
Comprehensive income	319		823		1,184		834
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Operating revenues	1,375		1,221		3,706		3,482
Operating revenues from affiliates	1		1		3		2
Total Revenues	1,376		1,222		3,709		3,484
Operating expenses
Purchased power and fuel	388		325		974		741
Purchased power and fuel from affiliates	2		1		17		174
Operating and maintenance	353		320		1,023		923
Operating and maintenance from affiliates	51		39		143		117
Depreciation and amortization	176		174		528		521
Taxes other than income	79		76		225		225
Total operating expenses	1,049		935		2,910		2,701
Operating income	327		287		799		783
Other income and (deductions)
Interest expense, net	(80)		(78)		(238)		(231)
Interest expense to affiliates	(3)		(3)		(10)		(10)
Other, net	4		4		14		14
Total other income and (deductions)	(79)		(77)		(234)		(227)
Income before income taxes	248		210		565		556
Income taxes	99		84		226		221
Net income	149		126		339		335
Pension and non-pension postretirement benefit plans:
Comprehensive income	149		126		339		335
PECO Energy Co [Member]
Operating revenues [Abstract]
Operating revenues	739		693		2,385		2,342
Operating revenues from affiliates	1		0		1		1
Total Revenues	740		693		2,386		2,343
Operating expenses
Purchased power and fuel	217		228		782		798
Purchased power and fuel from affiliates	61		27		171		162
Operating and maintenance	166		181		529		597
Operating and maintenance from affiliates	30		23		80		71
Depreciation and amortization	68		59		198		176
Taxes other than income	44		42		125		122
Total operating expenses	586		560		1,885		1,926
Equity in losses of unconsolidated affiliates					0		0
Gain (Loss) on Sale of Assets and Asset Impairment Charges							0
Gain (Loss) on Disposition of Assets	0		0		1
Operating income	154		133		502		417
Other income and (deductions)
Interest expense, net	(25)		(26)		(75)		(76)
Interest expense to affiliates	(3)		(3)		(9)		(9)
Other, net	1		2		3		5
Total other income and (deductions)	(27)		(27)		(81)		(80)
Income before income taxes	127		106		421		337
Income taxes	37		25		122		82
Net income					299		255
Net income attributable to common shareholders	90		81		299		255
Pension and non-pension postretirement benefit plans:
Comprehensive income	90		81		299		255
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Operating revenues	722		694		2,378		2,383
Operating revenues from affiliates	3		3		10		21
Total Revenues	725		697		2,388		2,404
Operating expenses
Purchased power and fuel	170		216		664		808
Purchased power and fuel from affiliates	141		81		373		286
Operating and maintenance	138		142		412		468
Operating and maintenance from affiliates	31		23		87		73
Depreciation and amortization	79		78		271		275
Taxes other than income	57		55		169		168
Total operating expenses	616		595		1,976		2,078
Equity in losses of unconsolidated affiliates							0
Gain (Loss) on Disposition of Assets	1				1
Operating income	110		102		413		326
Other income and (deductions)
Interest expense, net	(21)		(22)		(62)		(69)
Interest expense to affiliates	(4)		(4)		(11)		(12)
Other, net	4		4		13		14
Total other income and (deductions)	(21)		(22)		(60)		(67)
Income before income taxes	89		80		353		259
Income taxes	35		31		141		103
Net income	54		49		212		156
Preferred security dividends and redemption	3		3		10		10
Net income attributable to common shareholders	51		46		202		146
Pension and non-pension postretirement benefit plans:
Comprehensive income	$ 54		$ 49		$ 212		$ 156
[1]	(d)Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.
[2]	(c)For the three months ended September 30, 2015 and 2014, utility taxes of $28 million and $22 million, respectively, are included in revenues and expenses for Generation. For the three months ended September 30, 2015 and 2014, utility taxes of $63 million and $61 million, respectively, are included in revenues and expenses for ComEd. For the three months ended September 30, 2015 and 2014, utility taxes of $37 million and $34 million, respectively, are included in revenues and expenses for PECO. For the three months ended September 30, 2015 and 2014, utility taxes of $23 million and $21 million, respectively, are included in revenues and expenses for BGE.
[3]	(d)Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.
[4]	All amounts are net of tax. Amounts in parentheses represent a decrease in accumulated other comprehensive income.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	$ 1,959	$ 1,725
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	2,930	2,856
Impairment of long-lived assets	25	162
Gain on consolidation and acquisition of businesses	0	(268)
Gain on sales of assets	(10)	(356)
Deferred income taxes and amortization of investment tax credits	241	459
Net fair value changes related to derivatives	(363)	522
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	221	(141)
Other non-cash operating activities	856	698
Changes in assets and liabilities:
Accounts receivable	175	198
Inventories	65	(316)
Accounts payable, accrued expenses and other current liabilities	(147)	(322)
Option premiums received, net	27	21
Counterparty collateral received (posted), net	305	(615)
Income taxes	300	72
Pension and non-pension postretirement benefit contributions	(430)	(516)
Other assets and liabilities	(480)	(536)
Net cash flows provided by operating activities	5,674	3,643
Cash flows from investing activities
Capital expenditures	(5,443)	(4,114)
Proceeds from nuclear decommissioning trust fund sales	4,551	5,464
Investment in nuclear decommissioning trust funds	(4,737)	(5,550)
Acquisition of businesses	(28)	(67)
Proceeds from sale of long-lived assets	145	660
Proceeds from termination of direct financing lease investment	0	335
Proceeds from sales of investments	0	7
Change in restricted cash	(70)	(151)
Cash and restricted cash acquired from consolidations and acquisitions	0	129
Other investing activities	(107)	(89)
Net cash flows used in investing activities	(5,689)	(3,376)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	230	236
Issuance of long-term debt	5,909	3,212
Retirement of long-term debt	(1,745)	(1,214)
Distributions to noncontrolling interest of consolidated VIE	0
Payments to Noncontrolling Interests		(415)
Dividends paid on common stock	(819)	(799)
Proceeds from employee stock plans	24	25
Other financing activities	(65)	(158)
Proceeds from Issuance of Common Stock	1,868
Net cash flows provided by financing activities	5,402	887
Increase in cash and cash equivalents	5,387	1,154
Cash and cash equivalents at beginning of period	1,878	1,609
Cash and cash equivalents at end of period	7,265	2,763
Exelon Generation Co L L C [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	1,208	1,037
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	1,887	1,853
Impairment of long-lived assets	1	138
Gain on consolidation and acquisition of businesses	0	(268)
Gain on sales of assets	(7)	(355)
Deferred income taxes and amortization of investment tax credits	21	154
Net fair value changes related to derivatives	(252)	509
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	221	(141)
Other non-cash operating activities	227	251
Changes in assets and liabilities:
Accounts receivable	252	153
Receivables from and payables to affiliates, net	16	72
Inventories	69	(286)
Accounts payable, accrued expenses and other current liabilities	(156)	(311)
Option premiums received, net	27	21
Counterparty collateral received (posted), net	376	(634)
Income taxes	(70)	172
Pension and non-pension postretirement benefit contributions	(189)	(214)
Other assets and liabilities	(425)	(367)
Net cash flows provided by operating activities	3,206	1,784
Cash flows from investing activities
Capital expenditures	(2,774)	(1,961)
Proceeds from nuclear decommissioning trust fund sales	4,551	5,464
Investment in nuclear decommissioning trust funds	(4,737)	(5,550)
Proceeds from nuclear decommissioning trust fund sales	0
Acquisition of businesses	(28)	(67)
Proceeds from sale of long-lived assets	144	660
Change in restricted cash	(84)	(116)
Cash and restricted cash acquired from consolidations and acquisitions	0	129
Other investing activities	(92)	(34)
Changes in Exelon intercompany money pool	1,205	0
Funding of Exelon intercompany money pool		44
Net cash flows used in investing activities	(3,020)	(1,431)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	0	7
Issuance of long-term debt	1,307	1,112
Retirement of long-term debt	(64)	(552)
Repayments of Related Party Debt	(550)	0
Distributions to noncontrolling interest of consolidated VIE	0
Payments to Noncontrolling Interests		(415)
Other financing activities	(6)	(67)
Distribution to member	(2,368)	(440)
Changes in Exelon intercompany money pool	1,205	0
Contribution from member	55	55
Net cash flows provided by financing activities	(421)	(300)
Increase in cash and cash equivalents	(235)	53
Cash and cash equivalents at beginning of period	780	1,258
Cash and cash equivalents at end of period	545	1,311
Commonwealth Edison Co [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	339	335
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	528	521
Deferred income taxes and amortization of investment tax credits	107	154
Other non-cash operating activities	312	116
Changes in assets and liabilities:
Accounts receivable	(114)	(109)
Receivables from and payables to affiliates, net	(23)	(55)
Inventories	(23)	(12)
Accounts payable, accrued expenses and other current liabilities	(20)	59
Income taxes	389	15
Pension and non-pension postretirement benefit contributions	(142)	(237)
Other assets and liabilities	(7)	62
Net cash flows provided by operating activities	1,346	849
Cash flows from investing activities
Capital expenditures	(1,670)	(1,173)
Proceeds from sales of investments	0	7
Change in restricted cash	2	(2)
Other investing activities	22	20
Net cash flows used in investing activities	(1,646)	(1,148)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	300	344
Issuance of long-term debt	400	650
Retirement of long-term debt	(260)	(617)
Dividends paid on common stock	(226)	(230)
Other financing activities	(4)	(8)
Contributions from parent	75	168
Net cash flows provided by financing activities	285	307
Increase in cash and cash equivalents	(15)	8
Cash and cash equivalents at beginning of period	66	36
Cash and cash equivalents at end of period	51	44
PECO Energy Co [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	299	255
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	198	176
Gain on sales of assets		0
Deferred income taxes and amortization of investment tax credits	11	7
Other non-cash operating activities	69	70
Changes in assets and liabilities:
Accounts receivable	(15)	63
Receivables from and payables to affiliates, net	0	(20)
Inventories	8	5
Accounts payable, accrued expenses and other current liabilities	(17)	19
Income taxes	69	16
Pension and non-pension postretirement benefit contributions	(37)	(12)
Other assets and liabilities	(18)	(75)
Net cash flows provided by operating activities	567	504
Cash flows from investing activities
Capital expenditures	(435)	(461)
Change in restricted cash	(1)	0
Other investing activities	11	9
Changes in Exelon intercompany money pool	55	0
Net cash flows used in investing activities	(425)	(452)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Issuance of long-term debt	0	300
Dividends paid on common stock	(209)	(240)
Other financing activities	(2)	(7)
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	(16)	(24)
Changes in Exelon intercompany money pool	55	0
Net cash flows provided by financing activities	(140)	77
Increase in cash and cash equivalents	2	129
Cash and cash equivalents at beginning of period	30	217
Cash and cash equivalents at end of period	32	346
Baltimore Gas and Electric Company [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	212	156
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	271	275
Deferred income taxes and amortization of investment tax credits	79	57
Other non-cash operating activities	111	129
Changes in assets and liabilities:
Accounts receivable	62	101
Receivables from and payables to affiliates, net	(8)	(11)
Inventories	10	(21)
Accounts payable, accrued expenses and other current liabilities	49	(50)
Counterparty collateral received (posted), net	(27)	16
Income taxes	(6)	53
Pension and non-pension postretirement benefit contributions	(14)	(13)
Other assets and liabilities	(43)	(67)
Net cash flows provided by operating activities	696	625
Cash flows from investing activities
Capital expenditures	(506)	(458)
Change in restricted cash	2	(37)
Other investing activities	13	15
Net cash flows used in investing activities	(491)	(480)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	(70)	(115)
Retirement of long-term debt	(37)	(35)
Dividends paid on common stock	(116)	0
Other financing activities	(15)	11
Contributions from parent	6
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	(10)	(10)
Net cash flows provided by financing activities	(242)	(149)
Increase in cash and cash equivalents	(37)	(4)
Cash and cash equivalents at beginning of period	64	31
Cash and cash equivalents at end of period	$ 27	$ 27

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Assets, Current [Abstract]
Cash and cash equivalents		$ 7,265	$ 1,878
Restricted cash and cash equivalents		341	271
Accounts receivable, net
Customer		3,215	3,482
Other		1,107	1,227
Mark-to-market derivative assets		1,116	1,279
Unamortized energy contract assets		135	254
Inventories, net
Fossil fuel and emission allowances		442	579
Materials and supplies		1,074	1,024
Deferred income taxes		211	244
Regulatory assets		779	847
Disposal Group, Including Discontinued Operation, Assets, Current		4	147
Other		1,178	865
Total current assets		16,867	12,097
Property, plant and equipment, net		55,814	52,087
Deferred debits and other assets
Regulatory assets		6,000	6,076
Nuclear decommissioning trust funds		10,103	10,537
Investments		620	544
Goodwill		2,672	2,672
Mark-to-market derivative assets		801	773
Unamortized energy contracts assets		513	549
Deferred Tax Assets, Net, Noncurrent		2	0
Pledged assets for Zion Station decommissioning		237	319
Other		1,499	1,160
Total deferred debits and other assets		22,447	22,630
Total assets		95,128	86,814
Liabilities, Current [Abstract]
Short-term borrowings		675	460
Long-term debt due within one year		897	1,802
Accounts payable		2,987	3,048
Accrued expenses		1,576	1,539
Regulatory liabilities		365	310
Mark-to-market derivative liabilities (current liabilities)		204	234
Unamortized energy contract liabilities		118	238
Other Liabilities, Current		1,017	1,123
Due to Affiliate, Current		8	8
Total current liabilities		7,847	8,762
Long-term debt		24,541	19,362
Long-term debt to financing trusts		648	648
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		13,480	13,019
Asset retirement obligations		8,405	7,295
Pension obligations		3,014	3,366
Non-pension postretirement benefit obligations		1,877	1,742
Spent nuclear fuel obligation		1,021	1,021
Regulatory liabilities		4,180	4,550
Mark-to-market derivative liabilities (noncurrent liabilities)		360	403
Unamortized energy contract liabilities		136	211
Payable for Zion Station decommissioning		99	155
Other		2,231	2,147
Total deferred credits and other liabilities		34,803	33,909
Total liabilities	[1]	$ 67,839	$ 62,681
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		$ 18,647	$ 16,709
Treasury stock, at cost (35 shares at both September 30, 2015 and December 31, 2014)		(2,327)	(2,327)
Retained earnings		12,046	10,910
Accumulated other comprehensive loss, net	[2]	(2,596)	(2,684)
Total shareholders’ equity		25,770	22,608
BGE preference stock not subject to mandatory redemption		193	193
Noncontrolling interest		1,326	1,332
Total equity		27,289	24,133
Total liabilities and shareholders’ equity		95,128	86,814
Member’s equity
Accumulated other comprehensive loss, net	[2]	(2,596)	(2,684)
Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		8,190	8,160
Deferred credits and other liabilities
Total liabilities		3,242	2,723
Exelon Generation Co L L C [Member]
Assets, Current [Abstract]
Cash and cash equivalents		545	780
Restricted cash and cash equivalents		242	158
Accounts receivable, net
Customer		2,056	2,295
Other		487	318
Mark-to-market derivative assets		1,116	1,276
Unamortized energy contract assets		135	254
Receivables from affiliates		84	113
Inventories, net
Fossil fuel and emission allowances		357	465
Materials and supplies		863	847
Deferred income taxes		201	327
Disposal Group, Including Discontinued Operation, Assets, Current		4	147
Other		960	658
Total current assets		7,050	7,638
Property, plant and equipment, net		24,982	22,945
Deferred debits and other assets
Nuclear decommissioning trust funds		10,103	10,537
Investments		197	104
Goodwill		47	47
Mark-to-market derivative assets		764	771
Unamortized energy contracts assets		513	549
Deferred Tax Assets, Net, Noncurrent		2	3
Pledged assets for Zion Station decommissioning		237	319
Other		881	731
Prepaid pension asset		1,703	1,704
Total deferred debits and other assets		14,447	14,765
Total assets	[3]	46,479	45,348
Liabilities, Current [Abstract]
Short-term borrowings		21	36
Long-term debt due within one year		97	58
Accounts payable		1,676	1,759
Accrued expenses		835	886
Mark-to-market derivative liabilities (current liabilities)		182	214
Unamortized energy contract liabilities		118	238
Other Liabilities, Current		546	605
Payables to affiliates		106	107
Related Party Transaction, Due from (to) Related Party		1,205	0
Due to Affiliate, Current		0	556
Total current liabilities		4,786	4,459
Long-term debt		7,964	6,709
Long-term debt to affiliate		935	943
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		6,030	6,034
Asset retirement obligations		8,254	7,146
Non-pension postretirement benefit obligations		926	915
Spent nuclear fuel obligation		1,021	1,021
Mark-to-market derivative liabilities (noncurrent liabilities)		139	105
Unamortized energy contract liabilities		136	211
Payable for Zion Station decommissioning		99	155
Other		727	719
Payables to affiliates		2,538	2,880
Total deferred credits and other liabilities		19,870	19,186
Total liabilities	[3]	33,555	31,297
Stockholders' Equity Attributable to Parent [Abstract]
Accumulated other comprehensive loss, net	[2]	(60)	(36)
Noncontrolling interest		1,325	1,333
Total equity		12,924	14,051
Member’s equity
Membership interest		9,006	8,951
Undistributed earnings		2,653	3,803
Accumulated other comprehensive loss, net	[2]	(60)	(36)
Total member's equity		11,599	12,718
Total equity		12,924	14,051
Total liabilities and equity		46,479	45,348
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		8,130	8,119
Deferred credits and other liabilities
Total liabilities		3,070	2,507
Commonwealth Edison Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents		51	66
Restricted cash and cash equivalents		2	4
Accounts receivable, net
Customer		557	477
Other		334	648
Receivables from affiliates		14	14
Inventories, net
Regulatory assets		232	349
Other		84	40
Inventories, net		148	125
Total current assets		1,422	1,723
Property, plant and equipment, net		17,001	15,793
Deferred debits and other assets
Regulatory assets		913	852
Goodwill		2,625	2,625
Other		295	277
Receivable from affiliate		2,336	2,571
Prepaid pension asset		1,537	1,551
Total deferred debits and other assets		7,706	7,876
Total assets		26,129	25,392
Liabilities, Current [Abstract]
Short-term borrowings		604	304
Long-term debt due within one year		665	260
Accounts payable		693	598
Accrued expenses		337	331
Deferred income taxes		0	63
Regulatory liabilities		144	125
Mark-to-market derivative liabilities (current liabilities)		22	20
Other Liabilities, Current		68	73
Customer deposits		130	128
Due to Affiliate, Current		60	84
Total current liabilities		2,723	1,986
Long-term debt		5,435	5,698
Long-term debt to financing trusts		206	206
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		4,677	4,498
Asset retirement obligations		110	103
Non-pension postretirement benefit obligations		262	263
Regulatory liabilities		3,441	3,655
Mark-to-market derivative liabilities (noncurrent liabilities)		221	187
Other		954	889
Total deferred credits and other liabilities		9,665	9,595
Total liabilities		$ 18,029	$ 17,485
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		$ 1,588	$ 1,588
Retained earnings		964	851
Other paid-in capital		5,548	5,468
Total shareholders’ equity		8,100	7,907
Total equity		8,100	7,907
Total liabilities and shareholders’ equity		26,129	25,392
PECO Energy Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents		32	30
Restricted cash and cash equivalents		3	2
Accounts receivable, net
Customer		283	320
Other		122	141
Receivables from affiliates		4	3
Inventories, net
Fossil fuel and emission allowances		43	57
Materials and supplies		28	22
Deferred income taxes		69	69
Regulatory assets		32	29
Other		25	31
Prepaid utility taxes		42	10
Total current assets		683	714
Property, plant and equipment, net		7,027	6,801
Deferred debits and other assets
Regulatory assets		1,557	1,529
Investments		28	31
Other		36	34
Receivable from affiliate		388	490
Prepaid pension asset		353	344
Total deferred debits and other assets		2,362	2,428
Total assets		10,072	9,943
Liabilities, Current [Abstract]
Accounts payable		298	337
Accrued expenses		123	91
Regulatory liabilities		104	90
Other Liabilities, Current		30	31
Payables to affiliates		55	0
Customer deposits		56	52
Due to Affiliate, Current		53	52
Total current liabilities		719	653
Long-term debt		2,246	2,246
Long-term debt to financing trusts		184	184
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,752	2,671
Asset retirement obligations		26	29
Non-pension postretirement benefit obligations		288	287
Regulatory liabilities		536	657
Other		94	95
Total deferred credits and other liabilities		3,696	3,739
Total liabilities		$ 6,845	$ 6,822
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		$ 2,455	$ 2,439
Retained earnings		771	681
Accumulated other comprehensive loss, net	[2]	1	1
Total shareholders’ equity		3,227	3,121
Total equity		3,227	3,121
Total liabilities and shareholders’ equity		10,072	9,943
Member’s equity
Accumulated other comprehensive loss, net	[2]	1	1
Baltimore Gas and Electric Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		27	64
Restricted cash and cash equivalents		48	50
Accounts receivable, net
Customer		318	390
Other		77	82
Receivables from affiliates		1
Inventories, net
Fossil fuel and emission allowances		42	57
Materials and supplies		35	30
Deferred income taxes		8	6
Regulatory assets		257	214
Other		5	5
Prepaid utility taxes		4	59
Total current assets		822	957
Property, plant and equipment, net		6,459	6,204
Deferred debits and other assets
Regulatory assets		485	510
Investments		12	12
Other		25	25
Prepaid pension asset		331	370
Total deferred debits and other assets		853	917
Total assets	[4]	8,134	8,078
Liabilities, Current [Abstract]
Short-term borrowings		50	120
Long-term debt due within one year		77	75
Accounts payable		201	215
Accrued expenses		159	131
Deferred income taxes		63	52
Regulatory liabilities		69	44
Other Liabilities, Current		32	51
Customer deposits		99	92
Due to Affiliate, Current		47	66
Total current liabilities		797	846
Long-term debt		1,828	1,867
Long-term debt to financing trusts		258	258
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		1,937	1,865
Asset retirement obligations		15	17
Non-pension postretirement benefit obligations		209	212
Regulatory liabilities		186	200
Other		59	60
Total deferred credits and other liabilities		2,406	2,354
Total liabilities	[4]	5,289	5,325
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		1,366	1,360
Retained earnings		1,289	1,203
Total shareholders’ equity		2,655	2,563
BGE preference stock not subject to mandatory redemption		190	190
Total equity		2,845	2,753
Total liabilities and shareholders' equity		8,134	8,078
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		49	24
Deferred credits and other liabilities
Total liabilities		$ 162	$ 197	[4]
[1]	Exelon’s consolidated assets include $8,190 million and $8,160 million at September 30, 2015 and December 31, 2014, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,242 million and $2,723 million at September 30, 2015 and December 31, 2014, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 3 — Variable Interest Entities.
[2]	All amounts are net of tax. Amounts in parentheses represent a decrease in accumulated other comprehensive income.
[3]	Generation’s consolidated assets include $8,130 million and $8,119 million at September 30, 2015 and December 31, 2014, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,070 million and $2,507 million at September 30, 2015 and December 31, 2014, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 3 — Variable Interest Entities.
[4]	BGE’s consolidated assets include $49 million and $24 million at September 30, 2015 and December 31, 2014, respectively, of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $162 million and $197 million at September 30, 2015 and December 31, 2014, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 3 — Variable Interest Entities.

Consolidated Balance Sheets (U5

Consolidated Balance Sheets (Unaudited) (Parenthetical) - shares	Sep. 30, 2015	Dec. 31, 2014
Stockholders' Equity Attributable to Parent [Abstract]
Common Stock, Shares Authorized	2,000,000,000	2,000,000,000
Common Stock, Shares, Outstanding		859,825,013
Treasury Stock, Shares held	35,000,000	35,000,000

Consolidated Statement of Chang

Consolidated Statement of Changes in Shareholders Equity (Unaudited) - 9 months ended Sep. 30, 2015 - USD ($) shares in Thousands, $ in Millions		Total	Common Stock [Member]	Treasury Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]	Preference Stock Not Subject To Mandatory Redemption [Member]	Commonwealth Edison Co [Member]	Commonwealth Edison Co [Member]Common Stock [Member]	Commonwealth Edison Co [Member]Other Additional Capital [Member]	Commonwealth Edison Co [Member]Retained Earnings, Unappropriated [Member]	Commonwealth Edison Co [Member]Retained Earnings, Appropriated [Member]	Exelon Generation Co L L C [Member]	Exelon Generation Co L L C [Member]Undistributed Earnings [Member]	Exelon Generation Co L L C [Member]Membership Interest [Member]	Exelon Generation Co L L C [Member]Accumulated Other Comprehensive Income (Loss) [Member]	Exelon Generation Co L L C [Member]Noncontrolling Interest [Member]	PECO Energy Co [Member]	PECO Energy Co [Member]Common Stock [Member]	PECO Energy Co [Member]Retained Earnings [Member]	PECO Energy Co [Member]Accumulated Other Comprehensive Income (Loss) [Member]	Baltimore Gas and Electric Company [Member]	Baltimore Gas and Electric Company [Member]Common Stock [Member]	Baltimore Gas and Electric Company [Member]Membership Interest [Member]	Baltimore Gas and Electric Company [Member]Retained Earnings [Member]	Baltimore Gas and Electric Company [Member]Preference Stock Not Subject To Mandatory Redemption [Member]
Beginning Balance (in shares) at Dec. 31, 2014		894,568
Beginning Balance at Dec. 31, 2014		$ 24,133	$ 16,709	$ (2,327)	$ 10,910	$ (2,684)	$ 1,332	$ 193	$ 7,907	$ 1,588	$ 5,468	$ (1,639)	$ 2,490	$ 14,051	$ 3,803	$ 8,951	$ (36)	$ 1,333	$ 3,121	$ 2,439	$ 681	$ 1	$ 2,753	$ 1,360	$ 2,563	$ 1,203	$ 190
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		1,959			1,959		(10)	10	339			339		1,208	1,218		0	(10)	299	0			212		212	212
Net income attributable to common shareholders		$ 1,959																	299		299	0	202
Noncontrolling Interest, Increase from Sale of Parent Equity Interest														2	0		0	2
Long-term incentive plan activity (in shares)		1,394
Long-term incentive plan activity		$ 47	47
Employee stock purchase plan issuances (in shares)		1,083
Employee stock purchase plan issuances		$ 24	24
Appropriation of retained earnings for future dividends									0			(339)	339
Tax benefit on stock compensation		(1)	(1)
Common stock dividends		(823)			(823)			(10)	(226)				(226)							0	(209)	0	(116)		(116)	(116)
Contribution from parent									75		75
Distribution to members														(2,368)	(2,368)		0	0
Allocation of tax benefit from members																			16	16	0	0	6	6	6
Allocation of tax benefit from parent									5		5
Consolidated VIE dividend to non-controlling interest		0												0
Minority Interest Increase From Acquisition		4					4
Reversal of CENG equity method AOCI		0												0
Preferred security dividends		$ (10)																					(10)		(10)	(10)
Stock Issued During Period, Shares, New Issues		57,500
Stock Issued During Period, Value, New Issues		$ 1,868	1,868
Other comprehensive loss, net of income taxes of $53		88				88								(24)	0		(24)	0
Other comprehensive income (loss), net of tax	[1]	88												(24)
Ending Balance at Sep. 30, 2015		$ 27,289	$ 18,647	$ (2,327)	$ 12,046	$ (2,596)	$ 1,326	$ 193	$ 8,100	$ 1,588	$ 5,548	$ (1,639)	$ 2,603	$ 12,924	$ 2,653	$ 9,006	$ (60)	$ 1,325	$ 3,227	$ 2,455	$ 771	$ 1	$ 2,845	$ 1,366	$ 2,655	$ 1,289	$ 190
Ending Balance (in shares) at Sep. 30, 2015		954,545
[1]	All amounts are net of tax. Amounts in parentheses represent a decrease in accumulated other comprehensive income.

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation (Exelon, Generation, ComEd, PECO and BGE)	Index to Combined Notes to Consolidated Financial Statements The notes to the consolidated financial statements that follow are a combined presentation. The following list indicates the registrants to which the footnotes apply: Applicable Notes Registrant 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Exelon Corporation . . . . . . . . . . . . . . . . . . . . . Exelon Generation Company, LLC . . . . . . . . . . . . . . . . . . Commonwealth Edison Company . . . . . . . . . . . . PECO Energy Company . . . . . . . . . . . . . Baltimore Gas And Electric Company . . . . . . . . . . . . Basis of Presentation (Exelon, Generation, ComEd, PECO and BGE) Exelon is a utility services holding company engaged through its principal subsidiaries in the energy generation and energy distribution businesses. The energy generation business includes: • Generation : Physical delivery and marketing of owned and contracted electric generation capacity and provision of renewable and other energy-related products and services, and natural gas exploration and production activities. Generation has six reportable segments consisting of the Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. The energy delivery businesses include: • ComEd : Purchase and regulated retail sale of electricity and the provision of distribution and transmission services in northern Illinois, including the City of Chicago. • PECO : Purchase and regulated retail sale of electricity and the provision of distribution and transmission services in southeastern Pennsylvania, including the City of Philadelphia, and the purchase and regulated retail sale of natural gas and the provision of distribution services in the Pennsylvania counties surrounding the City of Philadelphia. • BGE : Purchase and regulated retail sale of electricity and the provision of distribution and transmission services in central Maryland, including the City of Baltimore, and the purchase and regulated retail sale of natural gas and the provision of distribution services in central Maryland, including the City of Baltimore. Each of the Registrant’s consolidated financial statements includes the accounts of its subsidiaries. All intercompany transactions have been eliminated. As a result of the Registrants' 2014 divestiture of certain unconsolidated affiliates considered integral to their operations and the consolidation of CENG during 2014, all Equity in earnings (losses) from unconsolidated affiliates have been presented below Income taxes in the Registrants' Consolidated Statements of Operations and Comprehensive Income starting in the first quarter of 2015. For the three months ended September 30, 2015, Generation recorded a $52 million (pre-tax) correcting adjustment to decrease mark-to-market income level 3 derivative contract valuations, of which $12 million (pre-tax) was originally recorded during 2014 and $40 million (pre-tax) was originally recorded during the first and second quarter of 2015. Exelon and Generation have concluded that this correcting adjustment is not material to their respective results of operations for the three and nine months ended September 30, 2015 or cash flows for the nine months ended September 30, 2015 or any prior period presented. Exelon and Generation do not expect this correcting adjustment to have a material impact on their respective results of operations or cash flows for the year ended December 31, 2015. The accompanying consolidated financial statements as of September 30, 2015 and 2014 and for the nine months then ended are unaudited but, in the opinion of the management of each Registrant include all adjustments that are considered necessary for a fair statement of the Registrants’ respective financial statements in accordance with GAAP. All adjustments are of a normal, recurring nature, except as otherwise disclosed. The December 31, 2014 Consolidated Balance Sheets were obtained from audited financial statements. Financial results for interim periods are not necessarily indicative of results that may be expected for any other interim period or for the fiscal year ending December 31, 2015 . These Combined Notes to Consolidated Financial Statements have been prepared pursuant to the rules and regulations of the SEC for Quarterly Reports on Form 10-Q. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. These notes should be read in conjunction with the Combined Notes to Consolidated Financial Statements of all Registrants included in ITEM 8. FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA of their respective 2014 Form 10-K Reports.

Accounting Policy (Exelon, Gene

Accounting Policy (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Significant Accounting Policies [Text Block]	New Accounting Pronouncements (Exelon, Generation, ComEd, PECO and BGE) The following recently issued accounting standard was effective for the Registrants during 2015. Application of Normal Purchases Normal Sales Exception to Power Contracts in Nodal Energy Markets In August 2015, the FASB issued authoritative guidance addressing the ability of entities to elect the normal purchase normal sales (NPNS) scope exception when the contract for the purchase or sale of electricity on a forward basis is delivered to a nodal energy market or transmitted through a nodal energy market. The NPNS scope exception allows entities to treat certain contracts that qualify as derivatives as contracts that do not require recognition at fair value. The guidance specifies that the use of locational marginal pricing by an independent system operator in such transactions does not constitute net settlement of a contract for the purchase or sale of electricity, even in scenarios in which legal title to the associated electricity is conveyed to the independent system operator during transmission. Consequently, the use of locational marginal pricing by the independent system operator does not cause that contract to fail to meet the physical delivery criterion of the NPNS scope exception. If the physical delivery criterion is met, along with all of the other criteria of the NPNS scope exception, an entity may elect to designate that contract as NPNS. The guidance is effective upon issuance and should be applied prospectively. The adoption of this guidance had no impact on the Registrants’ financial positions, results of operations, cash flows and disclosures. The following recently issued accounting standards are not yet required to be reflected in the combined financial statements of the Registrants. Simplifying the Accounting for Measurement-Period Adjustments In September 2015, the FASB issued authoritative guidance that requires an acquirer in a business combination to recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined and to record, in the same period’s financial statements, the effect on earnings of changes in depreciation, amortization, or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date . The guidance is effective for periods beginning after December 15, 2015. The guidance is required to be applied prospectively to adjustments to provisional amounts that occur after the effective date with earlier application permitted for financial statements that have not been issued. The Registrants expect to early adopt the standard in the fourth quarter of 2015. The adoption of this guidance will have no impact on the Registrants’ financial positions, results of operations, cash flows and disclosures. Simplifying the Measurement of Inventory In July 2015, the FASB issued authoritative guidance that requires inventory to be measured at the lower of cost or net realizable value. The new guidance defines net realizable value as the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal and transportation. This definition is consistent with existing authoritative guidance. Current guidance requires inventory to be measured at the lower of cost or market where market could be replacement cost, net realizable value or net realizable value less an approximately normal profit margin. The guidance is effective for periods beginning after December 15, 2016 with early adoption permitted. The guidance is required to be applied prospectively. The Registrants are currently assessing the impacts this guidance may have on their financial positions, results of operations, cash flows and disclosures as well as the potential to early adopt the guidance. Disclosures for Investments in Certain Entities that Calculate Net Asset Value per Share In May 2015, FASB issued authoritative guidance that removes the requirement to categorize within the fair value hierarchy all investments for which fair value is measured using the net asset value per share practical expedient. Investments measured at net asset value per share using the practical expedient will be presented as a reconciling item between the fair value hierarchy disclosure and the investment line item on the statement of financial position. The guidance also removes the requirement to make certain disclosures for all investments that are eligible to be measured at fair value using the net asset value per share practical expedient. Rather, those disclosures are limited to investments for which the entity has elected to measure the fair value using the practical expedient. The guidance is effective for the Registrants for fiscal years beginning after December 15, 2015 with early adoption permitted. The guidance is required to be applied retrospectively to all prior periods presented. The Registrants are currently assessing the impacts this guidance may have on their disclosures as well as the potential to early adopt the guidance. There will be no impact to their financial position, results of operations or cash flows. Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement In April 2015, the FASB issued authoritative guidance that clarifies the circumstances under which a cloud computing customer would account for the arrangement as a license of internal-use software. A cloud computing arrangement would include a software license if (1) the customer has a contractual right to take possession of the software at any time during the hosting period without significant penalty and (2) it is feasible for the customer to either run the software on its own hardware or contract with another party unrelated to the vendor to host the software. If the arrangement does not contain a software license, it would be accounted for as a service contract. The guidance is effective for the Registrants for fiscal years beginning after December 15, 2015. Early adoption is permitted. The guidance can be applied retrospectively to each prior reporting period presented or prospectively to arrangements entered into, or materially modified, after the effective date. The Registrants do not expect that this guidance will have a significant impact on their financial positions, results of operations, cash flows and disclosures. The Registrants expect to apply the standard prospectively to arrangements entered into, or materially modified, after the standard becomes effective for the Registrants on January 1, 2016. The Registrants do not plan to early adopt the standard. Simplifying the Presentation of Debt Issuance Costs In April 2015, the FASB issued authoritative guidance that changes the presentation of debt issuance costs in financial statements. The new guidance requires entities to present such costs in the balance sheet as a direct reduction to the related debt liability rather than as a deferred cost (i.e., an asset) as required by current guidance. The new standard does not change the recognition or measurement of debt issuance costs. The guidance is effective for the Registrants for fiscal years beginning after December 15, 2015. Early adoption is permitted for financial statements that have not been previously issued. The guidance is required to be applied retrospectively to all prior periods presented. The Registrants are currently assessing the impact this guidance may have on their financial positions and disclosures. The standard will not impact the results of operations and cash flows of the Registrants. The Registrants expect to complete their assessment by the fourth quarter of 2015 and early adopt the standard at that time. In August 2015, the FASB issued clarifying authoritative guidance for debt issuance costs incurred in connection with line-of-credit arrangements as such costs were not addressed within the guidance simplifying the presentation of debt issuance costs issued in April 2015. The guidance clarifies that an entity can defer and present debt issuance costs as an asset and subsequently amortize the deferred debt issuance costs ratably over the term of the line-of-credit arrangement. The adoption of this guidance will have no impact on the Registrants’ financial positions, results of operations, cash flows and disclosures . Amendments to the Consolidation Analysis In February 2015, the FASB issued authoritative guidance that amends the consolidation analysis for variable interest entities (VIEs) as well as voting interest entities. The new guidance primarily (1) changes the assessment of limited partnerships as VIEs, (2) amends the effect that fees paid to a decision maker or service provider have on the VIE analysis, (3) amends how variable interests held by a reporting entity’s related parties and de facto agents impact its consolidation conclusion, (4) clarifies how to determine whether equity holders (as a group) have power over an entity and (5) provides a scope exception for registered and similar unregistered money market funds. The guidance is effective for the Registrants for the first interim period beginning on or after December 15, 2015. Early adoption is permitted. The guidance can be applied retrospectively to each prior reporting period presented (full retrospective method) or retrospectively with a cumulative effect adjustment to retained earnings for initial application of the guidance at the date of adoption (modified retrospective method). The Registrants are currently assessing the impact this guidance may have on their financial positions, results of operations, cash flows and disclosures as well as the transition method that they will use to adopt the guidance. The Registrants do not plan to early adopt the standard. Revenue from Contracts with Customers In May 2014, the FASB issued authoritative guidance that changes the criteria for recognizing revenue from a contract with a customer. The new guidance replaces existing guidance on revenue recognition, including most industry specific guidance, with a five step model for recognizing and measuring revenue from contracts with customers. The objective of the new standard is to provide a single, comprehensive revenue recognition model for all contracts with customers to improve comparability within industries, across industries and across capital markets. The underlying principle is that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The guidance also requires a number of disclosures regarding the nature, amount, timing and uncertainty of revenue and the related cash flows. The guidance can be applied retrospectively to each prior reporting period presented (full retrospective method) or retrospectively with a cumulative effect adjustment to retained earnings for initial application of the guidance at the date of initial adoption (modified retrospective method). The Registrants are currently assessing the impacts this guidance may have on their financial positions, results of operations, cash flows and disclosures as well as the transition method that they will use to adopt the guidance. In August 2015, the FASB issued an amendment to provide a one year deferral of the effective date to annual reporting periods beginning on or after December 15, 2017, as well as an option to early adopt the standard for annual periods beginning on or after December 15, 2016. The Registrants do not plan to early adopt the standard.

Variable Interest Entities (Exe

Variable Interest Entities (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Variable Interest Entity [Abstract]
Variable Interest Entities (Exelon, Generation, ComEd, PECO and BGE)	Variable Interest Entities (Exelon, Generation, ComEd, PECO and BGE) A VIE is a legal entity that possesses any of the following characteristics: an insufficient amount of equity at risk to finance its activities, equity owners who do not have the power to direct the significant activities of the entity (or have voting rights that are disproportionate to their ownership interest), or equity owners who do not have the obligation to absorb expected losses or the right to receive the expected residual returns of the entity. Companies are required to consolidate a VIE if they are its primary beneficiary, which is the enterprise that has the power to direct the activities that most significantly affect the entity’s economic performance. At September 30, 2015 and December 31, 2014 , Exelon, Generation, and BGE collectively consolidated seven and six VIEs or VIE groups, respectively, for which the applicable Registrant was the primary beneficiary (see Consolidated Variable Interest Entities below) . As of September 30, 2015 and December 31, 2014 , the Registrants had significant interests in eight and six other VIEs, respectively, for which the Registrants do not have the power to direct the entities’ activities and, accordingly, were not the primary beneficiary (see Unconsolidated Variable Interest Entities below). During the second quarter of 2015 Generation added a new group of consolidated VIEs named “a group of companies formed by Generation to build, own, and operate other generating facilities.” The new group is comprised of a biomass fueled, combined heat and power facility and a backup generator company for which Generation is the primary beneficiary. Generation provides parental guarantees for up to $275 million in support of the payment obligations related to the Engineering, Procurement and Construction contract for Albany Green Energy, LLC (see Note 11 — Debt and Credit Agreements for additional details). Consolidated Variable Interest Entities Exelon, Generation and BGE’s consolidated VIEs consist of: • BondCo, a special purpose bankruptcy remote limited liability company formed by BGE to acquire, hold, issue and service bonds secured by rate stabilization property, • a retail gas group formed by Generation to enter into a collateralized gas supply agreement with a third-party gas supplier • a group of solar project limited liability companies formed by Generation to build, own and operate solar power facilities, • several wind project companies designed by Generation to develop, construct and operate wind generation facilities, • a group of companies formed by Generation to build, own and operate other generating facilities, • certain retail power and gas companies for which Generation is the sole supplier of energy, and • CENG. As of September 30, 2015 and December 31, 2014 , ComEd and PECO do not have any material consolidated VIEs. As of September 30, 2015 and December 31, 2014 , Exelon, Generation, and BGE provided the following support to their respective consolidated VIEs: • In the case of BondCo, BGE is required to remit all payments it receives from all residential customers through non-bypassable, rate stabilization charges to BondCo. During the three and nine months ended September 30, 2015 , BGE remitted $21 million and $63 million to BondCo, respectively. During the three and nine months ended September 30, 2014 , BGE remitted $21 million and $63 million to BondCo, respectively. • Generation provides operating and capital funding to the solar and wind entities for ongoing construction, operations and maintenance of the solar and wind power facilities and there is limited recourse to Generation related to the Antelope Valley project. • Generation and Exelon, where indicated, provide the following support to CENG (see Note 6 — Investment in Constellation Energy Nuclear Group, LLC , and Note 25 — Related Party Transactions , of the Exelon 2014 Form 10-K for additional information regarding Generation's and Exelon’s transactions with CENG): • under the NOSA, Generation conducts all activities related to the operation of the CENG nuclear generation fleet owned by CENG subsidiaries (the CENG fleet) and provides corporate and administrative services for the remaining life and decommissioning of the CENG nuclear plants as if they were a part of the Generation nuclear fleet, subject to the CENG member rights of EDF Inc. (EDFI) (a subsidiary of EDF), • under the Power Services Agency Agreement (PSAA), Generation provides scheduling, asset management, and billing services to the CENG fleet for the remaining operating life of the CENG nuclear plants, • under power purchase agreements with CENG, Generation will purchase 50.01% of the available output generated by the CENG nuclear plants not subject to other contractual agreements from January 2015 through the end of the operating life of each respective plant. However, pursuant to amendments dated March 31, 2015, the energy obligations under the Ginna Nuclear Power Plant (Ginna) PPAs have been suspended during the term of the expected Reliability Support Services Agreement (RSSA). Ginna originally entered into an agreement with Rochester Gas and Electric Corporation (RG&E) on February 13, 2015; however, final terms and conditions are currently under negotiation. The obligations under the RSSA are expected to commence retroactive back to April 1, 2015 and run through March 31, 2017 (see Note 5 — Regulatory Matters for additional details), • Generation provided a $400 million loan to CENG. As of September 30, 2015 , the remaining obligation is $296 million including accrued interest, which reflects the principal payment made in January 2015 (see Note 5 — Investment in Constellation Energy Nuclear Group, LLC of the Exelon 2014 Form 10-K for additional details), • Generation executed an Indemnity Agreement pursuant to which Generation agreed to indemnify EDF and its affiliates against third-party claims that may arise from any future nuclear incident (as defined in the Price-Anderson Act) in connection with the CENG nuclear plants or their operations. Exelon guarantees Generation’s obligations under this Indemnity Agreement. (See Note 19 — Commitments and Contingencies for more details), • in connection with CENG’s severance obligations, Generation has agreed to reimburse CENG for a total of approximately $6 million of the severance benefits paid or to be paid in 2014 through 2016 . As of September 30, 2015 , the remaining obligation is approximately $1 million , • Generation and EDFI share in the $637 million of contingent payment obligations for the payment of contingent retrospective premium adjustments for the nuclear liability insurance (see Note 19 — Commitments and Contingencies for more details), • Generation provides a guarantee of approximately $7 million associated with hazardous waste management facilities and underground storage tanks. In addition, EDFI executed a reimbursement agreement that provides reimbursement to Exelon for 49.99% of any amounts paid by Generation under this guarantee, • Generation and EDFI are the members-insured with Nuclear Electric Insurance Limited (NEIL) and have assigned the loss benefits under the insurance and the NEIL premium costs to CENG and guarantee the obligations of CENG under these insurance programs in proportion to their respective member interests (see Note 19 — Commitments and Contingencies for more details), and • Exelon has executed an agreement to provide up to $245 million to support the operations of CENG as well as a $165 million guarantee of CENG’s cash pooling agreement with its subsidiaries. • Generation provides approximately $11 million in credit support for the retail power and gas companies for which Generation is the sole supplier of energy, and • Generation provides a $75 million parental guarantee to the third-party gas supplier in support of its retail gas group. For each of the consolidated VIEs, except as otherwise noted: • the assets of the VIEs are restricted and can only be used to settle obligations of the respective VIE; • Exelon, Generation and BGE did not provide any additional material financial support to the VIEs; • Exelon, Generation and BGE did not have any material contractual commitments or obligations to provide financial support to the VIEs; and • the creditors of the VIEs did not have recourse to Exelon’s, Generation’s or BGE’s general credit. The carrying amounts and classification of the consolidated VIEs’ assets and liabilities included in Exelon’s, Generation’s, and BGE’s consolidated financial statements at September 30, 2015 and December 31, 2014 are as follows: September 30, 2015 December 31, 2014 Exelon (a) Generation BGE Exelon (a) Generation BGE Current assets $ 1,108 $ 1,057 $ 46 $ 1,271 $ 1,242 $ 21 Noncurrent assets 7,736 7,728 3 7,580 7,566 3 Total assets $ 8,844 $ 8,785 $ 49 $ 8,851 $ 8,808 $ 24 Current liabilities $ 494 $ 408 $ 81 $ 611 $ 526 $ 77 Noncurrent liabilities 2,859 2,773 81 2,730 2,600 120 Total liabilities $ 3,353 $ 3,181 $ 162 $ 3,341 $ 3,126 $ 197 _______________________ (a) Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity. Assets and Liabilities of Consolidated VIEs Included within the balances above are assets and liabilities of certain consolidated VIEs for which the assets can only be used to settle obligations of those VIEs, and liabilities that creditors, or beneficiaries, do not have recourse to the general credit of the Registrants. As of September 30, 2015 and December 31, 2014 , these assets and liabilities primarily consisted of the following: September 30, 2015 December 31, 2014 Exelon Generation BGE Exelon Generation BGE Cash and cash equivalents $ 330 $ 330 $ — $ 392 $ 392 $ — Restricted cash 193 146 46 117 96 21 Accounts receivable, net Customer 186 186 — 297 297 — Other 32 32 — 57 57 — Mark-to-market derivatives assets 116 116 — 171 171 — Inventory Materials and supplies 180 180 — 172 172 — Other current assets 48 43 — 33 26 — Total current assets 1,085 1,033 46 1,239 1,211 21 Property, plant and equipment, net 4,932 4,932 — 4,638 4,638 — Nuclear decommissioning trust funds 1,973 1,973 — 2,097 2,097 — Goodwill 47 47 — 47 47 — Mark-to-market derivatives assets 53 53 — 44 44 — Other noncurrent assets 100 92 3 95 82 3 Total noncurrent assets 7,105 7,097 3 6,921 6,908 3 Total assets $ 8,190 $ 8,130 $ 49 $ 8,160 $ 8,119 $ 24 Long-term debt due within one year $ 108 $ 26 $ 77 $ 87 $ 5 $ 75 Accounts payable 266 266 — 292 292 — Accrued expenses 92 88 4 111 108 2 Mark-to-market derivative liabilities — — — 24 24 — Unamortized energy contract liabilities 10 10 — 22 22 — Other current liabilities 15 15 — 25 25 — Total current liabilities 491 405 81 561 476 77 Long-term debt 729 643 81 212 81 120 Asset retirement obligations 1,906 1,906 — 1,763 1,763 — Pension obligation (a) 9 9 — 9 9 — Unamortized energy contract liabilities 42 42 — 51 51 — Other noncurrent liabilities 65 65 — 127 127 — Noncurrent liabilities 2,751 2,665 81 2,162 2,031 120 Total liabilities $ 3,242 $ 3,070 $ 162 $ 2,723 $ 2,507 $ 197 ______________ (a) Includes CNEG retail gas pension obligation, which is presented as a net asset balance within the Prepaid Pension asset line item on Generation’s balance sheet. See Note 14 — Retirement Benefits for additional details. Unconsolidated Variable Interest Entities Exelon’s and Generation’s variable interests in unconsolidated VIEs generally include equity investments and energy purchase and sale contracts. For the equity investments, the carrying amount of the investments is reflected on Exelon’s and Generation’s Consolidated Balance Sheets in Investments. For the energy purchase and sale contracts and the fuel purchase commitments (commercial agreements), the carrying amount of assets and liabilities in Exelon’s and Generation’s Consolidated Balance Sheets that relate to their involvement with the VIEs are predominately related to working capital accounts and generally represent the amounts owed by, or owed to, Exelon and Generation for the deliveries associated with the current billing cycles under the commercial agreements. Further, Exelon and Generation have not provided material debt or equity support, liquidity arrangements or performance guarantees associated with these commercial agreements. The Registrants’ unconsolidated VIEs consist of: • Energy purchase and sale agreements with VIEs for which Generation has concluded that consolidation is not required. • Asset sale agreement with ZionSolutions, LLC and EnergySolutions, Inc. in which Generation has a variable interest but has concluded that consolidation is not required. • Equity investments in energy development projects, distributed energy companies, and energy generating facilities for which Generation has concluded that consolidation is not required. As of September 30, 2015 and December 31, 2014 , Exelon and Generation had significant unconsolidated variable interests in eight and six VIEs, respectively, for which Exelon or Generation, as applicable, was not the primary beneficiary; including certain equity investments and certain commercial agreements. The increase in the number of unconsolidated VIEs is due to the execution of an energy purchase and sale agreement with a new unconsolidated VIE and an equity investment in a new unconsolidated VIE. In June 2015, 2015 ESA Investco, LLC, a wholly owned subsidiary of Generation, entered into an arrangement to purchase a 90% equity interest and 99% of the tax attributes of a distributed energy company. Equity will be contributed incrementally over an eighteen month period and will total approximately $250 million (see Note 19 — Commitments and Contingencies for additional details). Generation provides a parental guarantee of up to $275 million in support of 2015 ESA Investco, LLC's obligation to make equity contributions to the VIE. The investment was evaluated and it was determined to be a VIE for which Generation is not the primary beneficiary. Separate from the equity investment, Generation provided $27 million in cash to the other (10%) equity holder in the distributed energy company in exchange for a convertible promissory note. In July 2014, Generation entered into another arrangement with the same equity holder for the purchase of a 90% equity interest and 90% of the tax attributes of another distributed energy company. Generation’s total equity commitment in this arrangement was $91 million and is paid incrementally over an approximate two year period (see Note 19 — Commitments and Contingencies for additional details). This arrangement did not meet the definition of a VIE and is recorded as an equity method investment. Both distributed energy companies are considered related parties. The following tables present summary information about Exelon and Generation’s significant unconsolidated VIE entities: September 30, 2015 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 253 $ 131 $ 384 Total liabilities (a) 10 66 76 Exelon's ownership interest in VIE (a) — 19 19 Other ownership interests in VIE (a) 243 46 289 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 27 27 Contract intangible asset 9 — 9 Debt and payment guarantees — 3 3 Net assets pledged for Zion Station decommissioning (b) 20 — 20 December 31, 2014 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 114 $ 91 $ 205 Total liabilities (a) 3 49 52 Exelon's ownership interest in VIE (a) — 9 9 Other ownership interests in VIE (a) 111 33 144 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 13 13 Contract intangible asset 9 — 9 Debt and payment guarantees — 3 3 Net assets pledged for Zion Station decommissioning (b) 27 — 27 ___________________ (a) These items represent amounts on the unconsolidated VIE balance sheets, not on Exelon’s or Generation’s Consolidated Balance Sheets. These items are included to provide information regarding the relative size of the unconsolidated VIEs. Exelon corrected an error in the December 31, 2014 balances within Commercial Agreement VIEs for an overstatement of Total assets, Total liabilities and Other ownership interests in VIE of $392 million , $234 million and $158 million , respectively. The error is not considered material to any prior period. (b) These items represent amounts on Exelon’s and Generation’s Consolidated Balance Sheets related to the asset sale agreement with ZionSolutions, LLC. The net assets pledged for Zion Station decommissioning include, gross pledged assets of $237 million and $319 million as of September 30, 2015 and December 31, 2014 , respectively; offset by payables to ZionSolutions, LLC of $217 million and $292 million as of September 30, 2015 and December 31, 2014 , respectively. These items are included to provide information regarding the relative size of the ZionSolutions, LLC unconsolidated VIE. For each of the unconsolidated VIEs, Exelon and Generation has assessed the risk of a loss equal to their maximum exposure to be remote and, accordingly, Exelon and Generation have not recognized a liability associated with any portion of the maximum exposure to loss. In addition, there are no material agreements with, or commitments by, third parties that would affect the fair value or risk of their variable interests in these VIEs.

Mergers, Acquisitions, and Disp

Mergers, Acquisitions, and Dispositions	9 Months Ended
	Sep. 30, 2015
Business Combinations [Abstract]
Mergers, Acquisitions and Dispositions	Mergers, Acquisitions, and Dispositions (Exelon and Generation) Proposed Merger with Pepco Holdings, Inc. (Exelon) Description of Transaction On April 29, 2014, Exelon and Pepco Holdings, Inc. (PHI) signed an agreement and plan of merger (as subsequently amended and restated as of July 18, 2014, the Merger Agreement) to combine the two companies in an all cash transaction. The resulting company will retain the Exelon name and be headquartered in Chicago. Under the Merger Agreement, PHI’s shareholders will receive $27.25 of cash in exchange for each share of PHI common stock. Based on the outstanding shares of PHI’s common stock as of September 30, 2015, PHI shareholders would receive $6.9 billion in total cash. In addition, in connection with the Merger Agreement, Exelon entered into a subscription agreement under which it has purchased $180 million of a class of nonvoting, nonconvertible and nontransferable preferred securities of PHI. The preferred securities are included in Other non-current assets on Exelon’s Consolidated Balance Sheet. PHI has the right to redeem the preferred securities at its option for the purchase price paid plus accrued dividends, if any. On September 9, 2014, Exelon and PHI filed a Notification and Report Form with DOJ under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 (HSR Act). The HSR Act waiting period expired on December 22, 2014, and the HSR Act no longer precludes completion of the merger. Although the DOJ allowed the waiting period under the HSR Act to expire without taking any action with respect to the merger, the DOJ has not advised Exelon or PHI that it has concluded its investigation. Under the HSR Act, if the merger is not completed before December 23, 2015, Exelon and PHI are required to file again under the HSR Act and observe the required waiting period, which is 30 days from the new filing (and longer if the DOJ requests additional information), unless the DOJ terminates the waiting period earlier. Exelon and PHI intend to withdraw our pending HSR application and refile under the HSR Act on November 2, 2015. This will trigger a new 30-day waiting period. Unless a request for additional information is issued by DOJ during that waiting period, the waiting period will expire on December 2, 2015, and the parties will be free to close on or after December 2. To date, the PHI stockholders, the Virginia State Corporation Commission, the New Jersey Board of Public Utilities (NJBPU), the Delaware Public Service Commission (DPSC), the Maryland Public Service Commission (MDPSC) and the FERC have approved the merger of PHI and Exelon. The Federal Communications Commission has also approved the transfer of certain PHI communications licenses. On February 11, 2015, the NJBPU approved the proposed merger and the previously filed settlement signed and filed by Exelon, PHI, Atlantic City Electric (ACE), NJBPU staff, and the Independent Energy Coalition. The settlement provides a package of benefits to ACE customers and the state of New Jersey. This package of benefits includes the establishment of customer rate credit programs, with an aggregate value of $62 million for ACE customers and energy efficiency programs that will provide savings for ACE customers of $15 million . The March 6, 2015, order by the NJBPU approving the merger required that the consummation of the merger must take place no later than November 1, 2015 unless otherwise extended by the Board. On October 15, 2015, the NJBPU extended the November 1, 2015 date to June 30, 2016. On February 13, 2015, Exelon and PHI announced that they had reached a settlement agreement in the proceeding before the DPSC to review the proposed merger. The settlement, which was amended on April 7, 2015, was signed and filed by Exelon, PHI, Delmarva Power & Light Company (DPL), the DPSC Staff, the Delaware Public Advocate, the Delaware Department of Natural Resources and Environment Control, the Delaware Sustainable Energy Utility, the Mid-Atlantic Renewable Energy Coalition and the Clean Air Council. As part of this settlement, Exelon and PHI proposed a package of benefits to DPL customers and the state of Delaware including the establishment of customer rate credits of $40 million for DPL customers in Delaware, $2 million of funding for energy efficiency programs for DPL low income customers, and $2 million of funding for workforce development. On June 2, 2015, the DPSC issued an order accepting the settlement and approving the merger between Exelon and PHI. On March 17, 2015, Exelon and PHI announced that they had reached settlements with multiple parties in the Maryland proceeding to review the proposed merger after filing a Request for Adoption of Settlements with the MDPSC. The settlements were signed and filed by Exelon, PHI, Montgomery County, Prince George’s County, The Alliance for Solar Choice, the National Consumer Law Center, National Housing Trust, the Maryland Affordable Housing Coalition, the Housing Association of Nonprofit Developers, and a consortium of recreational trail advocacy organizations led by the Mid-Atlantic Off-Road Enthusiasts. On May 15, 2015, the MDPSC approved the merger after modifying a number of the conditions in the settlements, resulting in total rate credits of $66 million , funding for energy efficiency programs of $43.2 million , a Green Sustainability Fund of $14.4 million , 20 MWs of renewable generation development, ring-fencing, financial reporting conditions and increased penalties related to reliability commitments. On May 18, 2015, Exelon and PHI accepted and committed to fulfill the conditions. On June 11, 2015, the Maryland Office of People’s Counsel (OPC), the Sierra Club, and the Chesapeake Climate Action Network filed Petitions for Judicial Review of the MDPSC’s approval of the merger with the Circuit Court for Queen Anne’s County. On June 23, 2015, Public Citizen, Inc. filed its Petition for Judicial Review with the Circuit Court for Queen Anne’s County. On July 10, 2015, Exelon and PHI filed a response in opposition to the Petitions for Review. On July 21, 2015, the OPC filed a motion to stay the MDPSC order approving the merger and to set a schedule for discovery and presentation of new evidence. On July 29, 2015, Public Citizen, Inc. filed a response supporting OPC’s motion to stay, and on July 31, 2015 the Sierra Club and the Chesapeake Climate Action Network filed a joint motion to stay. In July and August, Exelon, PHI, the MDPSC, Prince George’s County and Montgomery County filed responses opposing the motions to stay. The presiding judge issued an order denying the motions for stay on August 12, 2015. A hearing on the underlying Petitions for Review is scheduled for December 8, 2015. On August 27, 2015, the District of Columbia Public Service Commission (DCPSC) issued an Opinion and Order denying approval of the merger, asserting that the merger was not in the public’s interest. Exelon and PHI filed an Application for Reconsideration with the DCPSC on September 28, 2015. On October 6, 2015, Exelon, PHI, the District of Columbia Government, the Office of Peoples Counsel, the District of Columbia Water and Sewer Authority, the National Consumer Law Center, National Housing Trust and National Housing Trust - Enterprise Preservation Corporation, and the Apartment and Office Building Association of Metropolitan Washington (collectively, Settling Parties) entered into a Nonunanimous Full Settlement Agreement and Stipulation (Settlement Agreement) with respect to the merger. Exelon and PHI subsequently filed a motion of joint applicants requesting the DCPSC to reopen the approval application to allow for consideration of the Settlement Agreement and granting additional requested relief. The new package of benefits totals $78 million and includes commitments to provide relief of residential customer base rate increases of $26 million , one-time direct bill credits of $14 million , low-income energy assistance of $16 million , improved reliability, a cleaner and greener D.C. through funding energy efficiency programs and development of renewable energy, and investment in local jobs and the local economy through workforce development of $5 million . It also guarantees charitable contributions totaling $19 million over 10 years. On October 28, 2015, the DCPSC at a public meeting agreed to reopen the approval application to allow for consideration of the Settlement Agreement and set a procedural schedule which would allow for completion of the merger in the first quarter of 2016. If the DCPSC does not approve the Settlement Agreement within the 150 day period after it was filed, either Exelon or PHI may terminate the Settlement Agreement. The settlements reached and commission orders received to date in Delaware, Maryland and New Jersey include a “most favored nation” provision which, generally speaking, requires allocation of merger benefits proportionately across all the jurisdictions. When applying the most favored nation provision to the settlement terms and other conditions established in the merger approvals received to date, and as proposed in the Settlement Agreement filed with the DCPSC, Exelon and PHI currently estimate direct benefits of $430 million or more on a net present value basis (excluding charitable contributions and renewable generation commitments) will be provided, including rate credits, funding for energy efficiency programs, sustainability funds and other required commitments. Exelon and PHI anticipate substantially all of such amounts will be charged to earnings at the time of merger close and will be paid by the end of 2017. An additional $50 million will be charged to earnings for charitable contributions, which are required to be paid over a period of 10 years. Commitments to develop renewable generation, which are expected to be primarily capital in nature, will be recognized as incurred. Upon completion of the merger, the actual nature, amount, timing and financial reporting treatment for these commitments may be materially different from the current projection. Exelon has been named in suits filed in the Delaware Chancery Court alleging that individual directors of PHI breached their fiduciary duties by entering into the proposed merger transaction and Exelon aided and abetted the individual directors’ breaches. The suits seek to enjoin PHI from completing the merger or seek rescission of the merger if completed. In addition, they also seek unspecified damages and costs. Exelon was also named in a federal court suit making similar claims. In September 2014, the parties reached a proposed settlement that would resolve all claims, which is subject to court approval. Final court approval of the proposed settlement is not anticipated until approximately 90 days after merger close. Exelon does not believe these suits will impact the completion of the transaction, and they are not expected to have a material impact on Exelon’s results of operations. Including 2014 and through September 30, 2015 , Exelon has incurred approximately $226 million of expense associated with the proposed merger. Of the total costs incurred, $110 million is primarily related to acquisition and integration costs and $116 million is for costs incurred to finance the transaction. The financing costs include a net loss of $64 million related to the settlement of forward-starting interest-rate swaps. These swaps were terminated in connection with the $4.2 billion issuance of debt; refer to Note 10 — Derivative Financial Instruments and Note 11 — Debt and Credit Agreements for more information. The financing costs exclude costs to issue debt and equity. During the three months ended September 30, 2015 , Exelon, Generation, ComEd, PECO and BGE incurred acquisition and integration costs, including financing costs, of $21 million , $9 million , $3 million , $2 million and $2 million , respectively. During the nine months ended September 30, 2015 , Exelon, Generation, ComEd, PECO and BGE incurred acquisition and integration costs of $47 million , $24 million , $10 million , $4 million and $5 million , respectively. During the three months ended September 30, 2014 , Exelon, Generation, ComEd, PECO and BGE incurred acquisition and integration costs, including financing costs, of $32 million , $3 million , $1 million , $1 million and $1 million , respectively. During the nine months ended September 30, 2014 , Exelon, Generation, ComEd, PECO and BGE incurred acquisition and integration costs of $57 million , $4 million , $1 million , $1 million and $1 million , respectively. The costs incurred are classified primarily within Operating and maintenance expense in the Registrants’ respective Consolidated Statement of Operations and Comprehensive Income, with the exception of the financing costs, which are included within Interest expense. The Merger Agreement also provides for termination rights for both parties. Exelon and PHI have entered into a Letter Agreement related to the Settlement Agreement which has the practical effect of suspending their rights to terminate the Merger Agreement until November 20, 2015 if no schedule has been set by the DCPSC allowing for approval of the settlement by March 4, 2016, or until March 4, 2016, if a schedule is set for approval by March 4, 2016, but approval does not occur by that date . Under certain circumstances, if the Merger Agreement is terminated, PHI may be required to pay Exelon a termination fee ranging from $259 million to $293 million plus certain expenses. If the Merger Agreement is terminated due to a regulatory failure, Exelon may be required to pay PHI a termination fee equal to $180 million (the amount of purchased nonvoting preferred securities of PHI described above), through the redemption by PHI of the outstanding nonvoting preferred securities for no consideration other than the nominal par value of the stock, plus reimbursement of PHIs documented out-of-pocket expenses up to a maximum of $40 million . Merger Financing As of September 30, 2015 , through the issuance of $5.4 billion of debt (including $1.15 billion of junior subordinated notes in the form of 23 million equity units), the issuance of $1.9 billion of common stock, and cash proceeds of $1.8 billion from asset sales primarily at Generation (after-tax proceeds of approximately $1.4 billion ), Exelon has sufficient cash to fund the all-cash purchase price, acquisition and integration related costs, and merger commitments. See Note 11 — Debt and Credit Agreements and Note 17 — Common Stock for further information on the debt and equity issuances. See Note 4 — Merger and Acquisitions of the Exelon 2014 Form 10-K for further information on the asset sales. Asset Divestitures (Exelon and Generation) On January 21, 2015, Generation closed on the sale of the Quail Run generating facility. Generation has sold generating assets for total pre-tax proceeds of $1.8 billion (after-tax proceeds of $1.4 billion ), including Quail Run and Safe Harbor, which are expected to be used primarily to finance a portion of the acquisition and related costs and expenses of PHI. On August 8, 2014 Generation closed on the sale of its 67% economic equity interest in the 417 MW Safe Harbor Water Power Corporation hydroelectric facility on the Susquehanna River in Pennsylvania for a purchase price of approximately $615 million . Generation recorded a pre-tax gain on the sale of approximately $329 million within Gain on sales of assets on Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income.

Regulatory Matters (Exelon, Gen

Regulatory Matters (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Regulated Operations [Abstract]
Regulatory Matters (Exelon, Generation, ComEd, PECO and BGE)	Regulatory Matters (Exelon, Generation, ComEd, PECO and BGE) Regulatory and Legislative Proceedings (Exelon, Generation, ComEd, PECO and BGE) Except for the matters noted below, the disclosures set forth in Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K appropriately represent, in all material respects, the current status of regulatory and legislative proceedings of the Registrants. The following is an update to that discussion. Illinois Regulatory Matters Energy Infrastructure Modernization Act (Exelon and ComEd). Since 2011, ComEd’s distribution rates are established through a performance-based rate formula, pursuant to EIMA. EIMA also provides a structure for substantial capital investment by utilities to modernize Illinois’ electric utility infrastructure. EIMA was scheduled to sunset, ending ComEd’s performance based rate formula and investment commitment, at December 31, 2017, unless approved to continue through 2022 by the Illinois General Assembly. On April 3, 2015, the Governor signed legislation extending the EIMA sunset from 2017 to 2019. Participating utilities are required to file an annual update to the performance-based formula rate tariff on or before May 1, with resulting rates effective in January of the following year. This annual formula rate update is based on prior year actual costs and current year projected capital additions. The update also reconciles any differences between the revenue requirement(s) in effect for the prior year and actual costs incurred for that year. Throughout each year, ComEd records regulatory assets or regulatory liabilities and corresponding increases or decreases to operating revenues for any differences between the revenue requirement(s) in effect and ComEd’s best estimate of the revenue requirement expected to be approved by the ICC for that year’s reconciliation. As of September 30, 2015 , and December 31, 2014 , ComEd had recorded a net regulatory asset associated with the distribution formula rate of $240 million and $371 million , respectively. The regulatory asset associated with distribution true-up is amortized to Operating revenues as the associated amounts are recovered through rates. On April 15, 2015, ComEd filed its annual distribution formula rate with the ICC. The filing establishes the revenue requirement used to set the rates that will take effect in January 2016 after the ICC’s review and approval, which is due by December 2015. The revenue requirement requested is based on 2014 actual costs plus projected 2015 capital additions as well as an annual reconciliation of the revenue requirement in effect in 2014 to the actual costs incurred that year. ComEd's 2015 filing request includes a total decrease to the revenue requirement of $50 million , reflecting an increase of $92 million for the initial revenue requirement for 2016 and a decrease of $142 million related to the annual reconciliation for 2014. The revenue requirement for 2016 provides for a weighted average debt and equity return on distribution rate base of 7.05% inclusive of an allowed ROE of 9.14% , reflecting the average rate on 30 -year treasury notes plus 580 basis points. The annual reconciliation for 2014 provided for a weighted average debt and equity return on distribution rate base of 7.02% inclusive of an allowed ROE of 9.09% , reflecting the average rate on 30 -year treasury notes plus 580 basis points less a performance metrics penalty of 5 basis points. On October 19, 2015, the ALJ issued its proposed order in ComEd's current distribution formula rate proceeding, recommending a total decrease to the revenue requirement of $ 68 million as compared to ComEd's requested decrease of $ 50 million discussed above. The $ 18 million reduction consisted of a $ 8 million decrease to the initial 2016 revenue requirement and a decrease of $ 10 million related to the 2014 annual reconciliation. The ALJs proposed order has no independent legal effect as the ICC must vote on a final order by mid December 2015, which may materially vary from the findings and conclusions in the proposed order. If the ICC provides significant changes to ComEd's filed revenue requirement request, it could have a material impact on ComEd's current and future results of operations and cash flows. Participating utilities are also required to file an annual update on their AMI implementation progress. On April 1, 2015, ComEd filed an annual progress report on its AMI Implementation Plan with the ICC, which allows for the installation of more than 4 million smart meters throughout ComEd's service territory by 2018. To date, over 1.6 million smart meters have been installed in the Chicago area. Grand Prairie Gateway Transmission Line (Exelon and ComEd). On December 2, 2013, ComEd filed a request to obtain the ICC’s approval to construct a 60-mile overhead 345kV transmission line that traverses Ogle, DeKalb, Kane and DuPage Counties in Northern Illinois. On May 28, 2014, in a separate proceeding, FERC issued an order granting ComEd’s request to include 100% of the capital costs recorded to construction work in progress during construction of the line in ComEd’s transmission rate base. If the project is cancelled or abandoned for reasons beyond ComEd’s control, FERC approved the ability for ComEd to recover 100% of its prudent costs incurred after May 21, 2014 and 50% of its costs incurred prior to May 21, 2014 in ComEd’s transmission rate base. The costs incurred for the project prior to May 21, 2014 were immaterial. On October 22, 2014, the ICC issued an order approving ComEd’s Grand Prairie Gateway Project over the objection of numerous landowners and the City of Elgin. On January 15, 2015, the City of Elgin and other parties filed a Notice of Appeal in the Illinois Appellate Court. On April 8, 2015, the ICC issued a rehearing order denying the proposals filed by certain landowners to consider an alternate route for a three-mile segment of the transmission line. The rehearing order affirmed the route approved within the ICC’s October 22, 2014 order. On July 8, 2015, the ICC approved ComEd's request for eminent domain to involuntarily acquire easements across 28 land parcels. On September 28, 2015, ComEd filed a petition with the ICC to acquire an additional eight parcels through eminent domain. ComEd began construction of the line during the second quarter of 2015 with an in-service date expected in the second quarter of 2017. Pennsylvania Regulatory Matters 2015 Pennsylvania Electric Distribution Rate Case (Exelon and PECO). On March 27, 2015, PECO filed a petition with the PAPUC requesting an increase of $190 million to its annual service revenues for electric delivery, which requested an ROE of 10.95% . On September 10, 2015, PECO and interested parties filed with the PAPUC a petition for joint settlement for an increase of $127 million in annual distribution service revenue. No overall ROE was specified in the settlement. On October 28, 2015, the ALJ issued a Recommended Decision to the PAPUC that the joint settlement be approved. A final ruling from the PAPUC is expected by December 2015, and if approved, the new electric delivery rates will take effect on January 1, 2016. Pennsylvania Procurement Proceedings (Exelon and PECO). On October 12, 2012, the PAPUC issued its Opinion and Order approving PECO’s second DSP Program, which was filed with the PAPUC in January 2012. The program, which had a 24-month term from June 1, 2013 through May 31, 2015, complies with electric generation procurement guidelines set forth in Act 129. In the second DSP Program, PECO entered into contracts with PAPUC-approved bidders, including Generation, to procure electric supply for its default electric customers through five competitive procurements. In addition, the second DSP Program included a number of retail market enhancements recommended by the PAPUC in its previously issued Retail Markets Intermediate Work Plan Order. PECO was also directed to submit a plan to allow its low-income Customer Assistance Program (CAP) customers to purchase their generation supply from EGSs beginning in April 2014. In May 2013, PECO filed its CAP Shopping Plan with the PAPUC. By Order entered on January 24, 2014, the PAPUC approved PECO’s plan, with modifications, to make CAP shopping available beginning April 15, 2014. On March 20, 2014, the Office of Consumer Advocate (OCA) and low-income advocacy groups filed an appeal and emergency request for a stay with the Pennsylvania Commonwealth Court (the Court), claiming that the PAPUC-ordered CAP Shopping plan does not contain sufficient protections for low-income customers. On July 14, 2015, the Court issued opinions on the OCA and low-income advocacy group appeal. Specifically, the Court remanded the issue to the PAPUC with instructions that it approve a rule revision to the PECO CAP Shopping Plan that would prohibit CAP customers from entering into contracts with an EGS that would impose early cancellation/termination fees. PECO does not have information at this time as to what action it may be required to take following remand to the PAPUC. On December 4, 2014, the PAPUC approved PECO's third DSP Program. The program has a 24-month term from June 1, 2015 through May 31, 2017, and complies with electric generation procurement guidelines set forth in Act 129. Under the program, PECO is procuring electric supply through four competitive procurements for fixed price full requirements contracts of two years or less for the residential classes and small and medium commercial classes and spot market price full requirement contracts for the large commercial and industrial class load. As of September 30, 2015, PECO entered into contracts with PAPUC-approved bidders, including Generation, resulting from the first two of its four scheduled procurements. Charges incurred for electric supply procured through contracts with Generation are included in purchased power from affiliates on PECO’s Statement of Operations and Comprehensive Income. On March 12, 2015, PECO settled the CAP Design with the Office of Consumer Advocates (OCA) and Low Income Advocates, and filed the proposed plan with the PAPUC on March 20, 2015. The program design changes the rate structure of PECO's CAP to make the bills more affordable to customers enrolled in the assistance program. The CAP discounts continue to be recovered through PECO’s universal service fund cost. On July 8, 2015, the CAP Design was approved by the PAPUC. PECO plans to implement the program changes in October 2016. Smart Meter and Smart Grid Investments (Exelon and PECO). In April 2010, pursuant to Act 129 and the follow-on Implementation Order of 2009, the PAPUC approved PECO’s Smart Meter Procurement and Installation Plan (SMPIP). PECO is currently in the second phase of the SMPIP, under which PECO will deploy substantially all remaining smart meters, for a total of 1.7 million smart meters, on an accelerated basis by the end of 2015. In total, PECO currently expects to spend up to $591 million , excluding the cost of the original meters, on its smart meter infrastructure and approximately $155 million on smart grid investments through final deployment of which $200 million was primarily funded by SGIG. As of September 30, 2015 , PECO has spent $579 million and $155 million on smart meter and smart grid infrastructure, respectively, not including the DOE reimbursements received. For further information on the SGIG and Smart Meter and Smart Grid program, see Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K. Pennsylvania Act 11 of 2012 (Exelon and PECO). In February 2012, Act 11 was signed into law, which seeks to clarify the PAPUC’s authority to approve alternative ratemaking mechanisms, allowing for the implementation of a distribution system improvement charge (DSIC) in rates designed to recover capital project costs incurred to repair, improve or replace utilities’ aging electric and natural gas distribution systems in Pennsylvania. Prior to recovering costs pursuant to a DSIC, the PAPUC's implementation order requires a utility to have a Long Term Infrastructure Improvement Plan (LTIIP) approved by the Commission, which outlines how the utility is planning to increase its investment for repairing, improving, or replacing aging infrastructure. On May 7, 2015, the PAPUC approved PECO's modified natural gas LTIIP. In accordance with the approved LTIIP, PECO plans to spend $534 million through 2022 to further accelerate the replacement of existing gas mains and to relocate meters from indoors to outside in accordance with recent PAPUC rulemaking. In addition, on March 20, 2015, PECO filed a petition with the PAPUC for approval of its gas DSIC mechanism for recovery of gas LTIIP expenditures. On September 11, 2015, the PAPUC entered its Opinion and Order approving PECO’s petition for a gas DSIC. On March 27, 2015, PECO filed a petition with the PAPUC for approval of its proposed electric DSIC and LTIIP. In accordance with the LTIIP (System 2020 plan), PECO plans to spend $275 million over the next five years to modernize and storm-harden its electric distribution system, making it more weather resistant and less vulnerable to damage. The DSIC will allow PECO the opportunity to recover the costs, subject to certain criteria, incurred to repair, improve or replace its electric distribution property between rate cases. On October 22, 2015, the PAPUC entered its Opinion and Order approving PECO’s proposed petition for its electric LTIIP and DSIC. Maryland Regulatory Matters 2013 Maryland Electric and Gas Distribution Rate Case (Exelon and BGE). On May 17, 2013, and as amended on August 23, 2013, BGE filed for electric and gas base increases with the MDPSC, ultimately requesting increases of $83 million and $24 million , respectively. In addition to these requested rate increases, BGE’s application included a request for recovery of incremental capital expenditures and operating costs associated with BGE’s proposed short-term reliability improvement plan (the ERI initiative) in response to a MDPSC order through a surcharge separate from base rates. On December 13, 2013, the MDPSC issued an order in BGE’s 2013 electric and natural gas distribution rate case for increases in annual distribution service revenue of $34 million and $12 million , respectively, and an allowed return on equity of 9.75% and 9.60% , respectively. Rates became effective for services rendered on or after December 13, 2013. The MDPSC also authorized BGE to recover through a surcharge mechanism costs associated with five ERI initiative programs designed to accelerate electric reliability improvements premised upon the condition that the MDPSC approve specific projects in advance of cost recovery. On March 31, 2014, after reviewing comments filed by the parties and conducting a hearing on the matter, the MDPSC approved all but one project proposed for completion in 2014 as part of the ERI initiative. The ERI initiative surcharge became effective June 1, 2014. On November 3, 2014, BGE filed a surcharge update including a true-up of cost estimates included in the 2014 surcharge, along with its work plan and cost estimates for 2015, to be included in the 2015 surcharge. At its December 17, 2014 weekly Administrative Meeting, the MDPSC approved BGE's 2014 annual report, 2015 work plan and the 2015 surcharge. In January 2014, the residential consumer advocate in Maryland filed an appeal to the order issued by the MDPSC on December 13, 2013 in BGE's 2013 electric and gas distribution rate cases. The residential consumer advocate filed its related legal memorandum on August 22, 2014, challenging the MDPSC's approval of the ERI initiative surcharge. BGE submitted a response to the appeal on October 15, 2014, and a hearing was held on November 17, 2014. BGE cannot predict the outcome of this appeal. If the residential consumer advocate's appeal is successful, BGE could recover ERI expenditures through other regulatory mechanisms. Smart Meter and Smart Grid Investments (Exelon and BGE). In August 2010, the MDPSC approved a comprehensive smart grid initiative for BGE that included the planned installation of 2 million residential and commercial electric and gas smart meters at an expected total cost of $480 million of which $200 million was funded by SGIG. The MDPSC’s approval ordered BGE to defer the associated incremental costs, depreciation and amortization, and an appropriate return, in a regulatory asset until such time as a cost-effective advanced metering system is implemented. As of September 30, 2015 and December 31, 2014 , BGE recorded a regulatory asset of $179 million and $128 million , respectively, representing incremental costs, depreciation and amortization, and a debt return on fixed assets related to its AMI program. As part of the settlement in BGE's 2014 electric and gas distribution rate case, the cost of the retired non-AMI meters will be amortized over 10 years. The Maryland Strategic Infrastructure Development and Enhancement Program (Exelon and BGE) . In February 2013, the Maryland General Assembly passed legislation intended to accelerate gas infrastructure replacements in Maryland by establishing a mechanism for gas companies to recover promptly reasonable and prudent costs of eligible infrastructure replacement projects separate from base rate proceedings. On May 2, 2013, the Governor of Maryland signed the legislation into law; which took effect June 1, 2013. Under the new law, following a proceeding before the MDPSC and with the MDPSC’s approval of the eligible infrastructure replacement projects along with a corresponding surcharge, BGE could begin charging gas customers a monthly surcharge for infrastructure costs incurred after June 1, 2013. The legislation includes caps on the monthly surcharges to residential and non-residential customers, and would require an annual true-up of the surcharge revenues against actual expenditures. Investment levels in excess of the cap would be recoverable in a subsequent gas base rate proceeding at which time all costs for the infrastructure replacement projects would be rolled into gas distribution rates. Irrespective of the cap, BGE is required to file a gas rate case every five years under this legislation. On August 2, 2013, BGE filed its infrastructure replacement plan and associated surcharge. On January 29, 2014, the MDPSC issued a decision conditionally approving the first five years of BGE’s plan and surcharge. On March 26, 2014, the MDPSC approved as filed BGE’s proposed 2014 project list, tariff and associated surcharge amounts, with a surcharge that became effective April 1, 2014. On November 17, 2014, BGE filed a surcharge update to be effective January 1, 2015 including a true-up of cost estimates included in the 2014 surcharge, along with its 2015 project list and projected capital estimates of $78 million to be included in the 2015 surcharge calculation. At its December 17, 2014 weekly Administrative Meeting, the MDPSC approved BGE's 2015 project list and the proposed surcharge for 2015, which included the true-up of the 2014 charge. As of September 30, 2015 , BGE recorded a regulatory liability of $1 million , representing the difference between the surcharge revenues and program costs. In February 2014, the residential consumer advocate in Maryland filed an appeal with the Baltimore City Circuit Court to the decision issued by the MDPSC on BGE’s infrastructure replacement plan. On September 5, 2014, the Baltimore City Circuit Court affirmed the MDPSC decision on BGE's infrastructure replacement plan and associated surcharge. On October 10, 2014, the residential consumer advocate noticed its appeal to the Maryland Court of Special Appeals from the judgment entered by the Baltimore City Circuit Court. During the third quarter of 2015, the residential consumer advocate, MDPSC and BGE filed briefs. The Court of Special Appeals has set oral argument in this matter for November 3, 2015. BGE cannot predict the outcome of this appeal. However, if the consumer advocates appeal is successful, BGE could seek recovery of infrastructure replacement costs through other regulatory mechanisms. New York Regulatory Matters Ginna Nuclear Power Plant Reliability Support Services Agreement (Exelon and Generation). Ginna Nuclear Power Plant's (Ginna) prior period fixed-price PPA contract with Rochester Gas & Electric Company (RG&E) expired in June 2014. In light of the expiration of the agreement, Ginna advised the New York Public Service Commission (NYPSC) and ISO-NY that in absence of a reliability need, Ginna management would make a recommendation, subject to approval by the CENG board, that Ginna be retired as soon as practicable. A formal study conducted by the ISO-NY and RG&E concluded that the Ginna nuclear plant needs to remain in operation to maintain the reliability of the transmission grid in the Rochester region through 2018 when planned transmission system upgrades are expected to be completed. In November 2014, in response to a petition filed by Ginna, the NYPSC directed Ginna and RG&E to negotiate a Reliability Support Services Agreement (RSSA). On February 13, 2015, regulatory filings, including RSSA terms negotiated between Ginna and RG&E, to support the continued operation of Ginna for reliability purposes were made with the NYPSC and with FERC for their approval. Although the RSSA contract is still subject to regulatory approvals, on April 1, 2015, Ginna began delivering power and capacity into ISO-NY consistent with the provisions of the proposed RSSA contract. In the event that Ginna continues to operate beyond the RSSA term, Ginna would be required to make a specified refund payment to RG&E. The FERC issued an order on April 14, 2015, directing Ginna to make a compliance filing to ensure that the RSSA does not allow Ginna to receive revenues above its full cost-of-service and rejecting any extension of the RSSA beyond its initial term, rather requiring any extension be subject to the rules currently being developed by ISO-NY. The FERC order also set the RSSA for hearing and settlement procedures. In response to the FERC's April 14, 2015 order, on May 14, 2015, Ginna submitted a compliance filing to FERC containing proposed revisions to the RSSA addressing FERC's requirements and maintaining the April 1, 2015 proposed effective date. On July 13, 2015, FERC accepted Ginna’s compliance filing effective April 1, 2015. The FERC accepted Ginna's proposal for market revenue sharing subject to a cap effective April 1, 2015, and rejected requests for rehearing by parties on a number of matters related to jurisdiction, the reliability need, RSSA term, and possible price suppression. In late August, Ginna reached a settlement in principle with interested parties modifying certain terms and conditions in the originally negotiated agreement. The proposed RSSA under the settlement preserves the value of the contract originally negotiated with RG&E, but shortens the term to March 31, 2017 and requires RG&E to complete a new transmission reliability study to determine if an interim reliability solution is required beyond March 31, 2017. The reliability study is expected to be completed by the end of 2015. If there continues to be a reliability need beyond March 31, 2017, RG&E has the right until June 30, 2016 to select Ginna as an ongoing reliability solution. If Ginna is not selected for continued reliability service and does not plan to retire shortly after RSSA expiration, Ginna is required to file a notice with the NYPSC no later than September 30, 2016. The settlement was filed at the NYPSC and at FERC on October 21, 2015 and remains subject to review and approval by both agencies, which do not expect to be completed until the first quarter of 2016. Until final regulatory approvals are received, Generation will recognize revenue based on market prices for energy and capacity delivered by Ginna into ISO-NY. Upon receiving regulatory approvals, under the RSSA contract terms, Generation would record an adjustment to recognize revenue based on the final approved pricing contained in the contract as of the April 1, 2015 effective date. While the RSSA is expected to receive regulatory approvals and, therefore, permit Ginna to continue operating through the RSSA term, there is still a risk that, for economic reasons, including adjustments to the revenue Ginna would be entitled to under the RSSA, Ginna could be retired before the end of its operating license period. In absence of such an agreement and in the event the plant is retired before the current license term ends in 2029, Exelon's and Generation's results of operations could be adversely affected by increased depreciation rates, impairment charges, severance costs, and accelerated future decommissioning costs, among other items. However, it is not expected that such impacts would be material to Exelon's or Generation's results of operations. Federal Regulatory Matters Transmission Formula Rate (Exelon, ComEd and BGE). ComEd’s and BGE’s transmission rates are each established based on a FERC-approved formula. ComEd and BGE are required to file an annual update to the FERC-approved formula on or before May 15, with the resulting rates effective on June 1 of the same year. The annual formula rate update is based on prior year actual costs and current year projected capital additions. The update also reconciles any differences between the revenue requirement in effect beginning June 1 of the prior year and actual costs incurred for that year. ComEd and BGE record regulatory assets or regulatory liabilities and corresponding increases or decreases to operating revenues for any differences between the revenue requirement in effect and ComEd’s and BGE’s best estimate of the revenue requirement expected to be approved by the FERC for that year’s reconciliation. As of September 30, 2015 and December 31, 2014 , ComEd had recorded a net regulatory asset associated with the transmission formula rate of $26 million and $21 million , respectively. As of September 30, 2015 and December 31, 2014 , BGE recorded a net regulatory asset associated with the transmission formula rate of $5 million and $1 million , respectively. The regulatory asset associated with the transmission true-up is amortized to Operating revenues as the associated amounts are recovered through rates. On April 15, 2015 (and revised on May 19) , ComEd filed its annual transmission formula rate update with the FERC. The filing establishes the revenue requirement used to set rates that took effect in June 2015, subject to review by the FERC and other parties, which is due by fourth quarter 2015. ComEd's 2015 annual update includes a total increase to the revenue requirement of $86 million , reflecting an increase of $68 million for the initial revenue requirement and an increase of $18 million related to the annual reconciliation . The revenue requirement provides for a weighted average debt and equity return on transmission rate base of 8.61% , inclusive of an allowed ROE of 11.50% , a decrease from the 8.62% average debt and equity return previously authorized. In April 2015, BGE filed its annual transmission formula rate update with the FERC. The filing establishes the revenue requirement used to set rates that took effect in June 2015, subject to review by other parties, which is due by October 2015. BGE's 2015 annual update includes a total increase to the revenue requirement of $10 million , reflecting an increase of $13 million for the initial revenue requirement and a decrease of $3 million related to the annual reconciliation. The revenue requirement provides for a weighted average debt and equity return on transmission rate base of 8.46% , inclusive of an allowed ROE of 11.30% , a decrease from the 8.53% average debt and equity return previously authorized. FERC Transmission Complaint (Exelon and BGE). On February 27, 2013, consumer advocates and regulators from the District of Columbia, New Jersey, Delaware and Maryland, and the Delaware Electric Municipal Cooperatives (the parties), filed a complaint at FERC against BGE and PHI companies relating to their respective transmission formula rates. BGE’s formula rate includes a 10.8% base rate of ROE and a 50 basis point incentive for participating in PJM (the latter of which is conditioned upon crediting the first 50 basis points of any incentive ROE adders). The parties seek a reduction in the base ROE to 8.7% and changes to the formula rate process. FERC docketed the matter and set April 3, 2013 as the deadline for interventions, protests and answers. Under FERC rules, the revenues subject to refund are limited to a fifteen month period and the earliest date from which the base ROE could be adjusted and refunds required is the date of the complaint. On March 19, 2013, BGE filed a motion to dismiss or sever the complaint. On August 21, 2014, FERC issued an order in the BGE and PHI companies' proceeding, which established hearing and settlement judge procedures for the complaint, and set a refund effective date of February 27, 2013. BGE, the PHI companies and the parties began settlement discussions under the guidance of a FERC administrative law judge on September 23, 2014. On November 24, 2014, the Settlement Judge informed FERC and the Chief Judge that the parties had reached an impasse and determined that a settlement was not possible. On November 26, 2014, the Chief Judge issued an order terminating the settlement proceeding, designating a presiding judge at the hearings and directing that an initial decision be issued by November 25, 2015. On December 8, 2014, various state agencies in Delaware, Maryland, New Jersey, and D.C. filed a second complaint against BGE regarding the base ROE of the transmission business seeking a reduction from 10.8% to 8.8% . The filing of the second complaint creates a second refund window. By order issued on February 9, 2015, FERC established a hearing on the second complaint with the complainants' requested refund effective date of December 8, 2014. On February 20, 2015, the Chief Judge issued an order consolidating the two complaint proceedings and established an Initial Decision issuance deadline of February 29, 2016. On March 2, 2015, the Presiding Administrative Law Judge issued an order establishing a procedural schedule for the consolidated proceedings that provides for the hearing to commence on October 20, 2015. On September 14, 2015, the complainants and respondents filed a joint motion to suspend the hearing schedule because they have reached a settlement in principle to resolve the ROE issue. On September 15, 2015, the Chief Administrative Law Judge issued an order granting the motion, and setting October 15, 2015 as the date for the moving parties to either file a settlement or file a status report detailing the timetable for filing a settlement, which was subsequently extended to October 30, 2015. On October 30, 2015, the parties filed a status report stating their intent to either file a settlement or file another status report during the fourth quarter of 2015. Based on the current status of the complaint filings, BGE believes it is probable that BGE's base ROE rate will be adjusted, and that a refund to customers of transmission revenue for the two maximum fifteen month periods will be required. BGE has established a reserve, which management believes is adequate for what it considers to be the most likely outcome. The estimated annual ongoing reduction in revenues if FERC approves the ROEs as originally requested by the parties in their initial filings is approximately $11 million . If FERC were to order a reduction of BGE’s base ROE to 8.7% and 8.8% as sought in the first and second complaints, respectively (while retaining the 50 basis points of any incentives that were credited to the base ROE for certain new transmission investment), the result would be a refund to customers of approximately $13 million and $14 million , for the first and second fifteen month refund windows, respectively, for a total refund to customers of approximately $ 27 million . PJM Transmission Rate Design and Operating Agreements (Exelon, ComEd, PECO and BGE). PJM Transmission Rate Design specifies the rates for transmission service charged to customers within PJM. Currently, ComEd, PECO and BGE incur costs based on the existing rate design, which charges customers based on the cost of the existing transmission facilities within their load zone and the cost of new transmission facilities based on those who benefit from those facilities. In April

Investment in Constellation Ene

Investment in Constellation Energy Nuclear Group, LLC (Exelon and Generation)	9 Months Ended
	Sep. 30, 2015
Equity Method Investments and Joint Ventures [Abstract]
Investment in Constellation Energy Nuclear Group, LLC (Exelon and Generation)	Investment in Constellation Energy Nuclear Group, LLC (Exelon and Generation) As a result of the Constellation merger, Generation owns a 50.01% interest in CENG, a nuclear generation business. Generation has historically had various agreements with CENG to purchase power and to provide certain services. For further information regarding these agreements, see Note 25 — Related Party Transactions of the Exelon 2014 Form 10-K. As a result of the consolidation of CENG on April 1, 2014, there are several additional transactions included in Exelon’s and Generation’s consolidated financial statements between CENG and Exelon's affiliates that are considered related party transactions to Generation. As further described in Note 25 — Related Party Transactions of the Exelon 2014 Form 10-K, EDF and Generation had a PPA with CENG under which they purchased 15% and 85% , respectively, of the nuclear output owned by CENG that was not sold to third parties under pre-existing PPAs through December 31, 2014. Beginning January 1, 2015 and continuing through the life of the respective plants, EDF and Generation will purchase 49.99% and 50.01% , respectively, of the nuclear output owned by CENG not subject to other contractual agreements. Beginning April 1, 2014, CENG's sales to Generation have been eliminated in consolidation. For the three and nine months ended September 30, 2015 , Generation had sales to EDF of $108 million and $395 million , respectively. See Note 3 — Variable Interest Entities for additional information regarding other transactions between CENG and EDF included within Exelon's and Generation’s consolidated financial statements and for additional information about the Registrant's VIEs. Accounting for the Consolidation of CENG Prior to April 1, 2014, Exelon and Generation accounted for their investment in CENG under the equity method of accounting. From January 1, 2014, through March 31, 2014, Generation recorded $19 million of equity in earnings of unconsolidated affiliates related to its investment in CENG and $17 million of revenues from CENG. The book value of Generation’s investment in CENG prior to the consolidation was $ 1.9 billion , and the book value of the AOCI related to CENG prior to consolidation was $116 million , net of taxes of $77 million . The transfer of the nuclear operating licenses and the execution of the NOSA on April 1, 2014 resulted in the derecognition of the equity method investment in CENG and the recording of all assets, liabilities and EDF’s noncontrolling interest in CENG at fair value on Exelon’s and Generation’s Consolidated Balance Sheets. Generation and EDFI also entered into a Put Option Agreement on April 1, 2014, pursuant to which EDFI has the option, exercisable beginning on January 1, 2016 and thereafter until June 30, 2022, to sell its 49.99% interest in CENG to Generation for a fair market value price determined by agreement of the parties, or absent agreement, a third-party arbitration process. The appraisers determining fair market value of EDF’s 49.99% interest in CENG under the Put Option Agreement are instructed to take into account all rights and obligations under the CENG Operating Agreement, including Generation’s rights with respect to any unpaid aggregate preferred distributions and the related return and the value of Generation’s rights to other distributions. The beginning of the exercise period will be accelerated if Exelon’s affiliates cease to own a majority of CENG and exercise a related right to terminate the NOSA. In addition, under limited circumstances, the period for exercise of the put option may be extended for 18 months. Due to the Preferred Distribution Rights that Generation has on CENG’s available cash, the earnings attributable to the noncontrolling interest on the Consolidated Statements of Operations and Comprehensive Income as well as the corresponding adjustment to Noncontrolling interest on the Consolidated Balance Sheets will not be in proportion to Generation’s and EDF’s equity ownership interests. Rather, the attribution considers Generation’s Preferred Distribution Rights and allocates net income based on each owner’s rights to CENG’s net assets. For the three and nine months ended September 30, 2015 , Generation reduced by $5 million and $13 million , respectively, the amount of Net income attributable to noncontrolling interests on Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. As a result of the consolidation, Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income includes CENG’s incremental operating revenues of $110 million and $416 million and CENG’s net income (loss), prior to any intercompany eliminations and any adjustments for noncontrolling interest, of $(75) million and $18 million during the three and nine months ended September 30, 2015 , respectively.

Impairment of Long-lived Assets

Impairment of Long-lived Assets (Exelon and Generation)	9 Months Ended
	Sep. 30, 2015
Property, Plant and Equipment [Abstract]
Impairment of Long-Lived Assets (Exelon and Generation)	7 . Impairment of Long-Lived Assets (Exelon and Generation) Long-Lived Assets (Exelon and Generation) Generation evaluates long-lived assets for recoverability whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. In the second quarter of each year, Generation updates the long-term fundamental energy prices, which includes a thorough evaluation of key assumptions including gas prices, load growth, environmental policy, plant retirements and renewable growth. In 2015, the year over year change in fundamentals did not indicate any impairments. In 2014, the year over year change in fundamentals suggested that the carrying value of certain merchant wind assets may be impaired. Generation concluded that the estimated undiscounted future cash flows and fair value of twelve wind projects, primarily located in West Texas, were less than their respective carrying values at May 31, 2014. As a result, long-lived assets held and used with a carrying amount of approximately $151 million were written down to their fair value of $65 million and a pre-tax impairment charge of $86 million was recorded during the second quarter of 2014 in Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. The fair value analysis was primarily based on the income approach using significant unobservable inputs (Level 3) including revenue and generation forecasts, projected capital and maintenance expenditures and discount rates. Changes in the assumptions described above could potentially result in future impairments of Exelon’s long-lived assets, which could be material. During the third quarter of 2014, certain non-nuclear generating assets were identified as assets held for sale on Exelon's and Generation's Consolidated Balance Sheets. When long-lived assets are held for sale, an impairment loss is recognized to the extent that the asset's carrying value exceeds its estimated fair value less costs to sell. At September 30, 2014, in connection with the approved asset sales agreements, a $50 million pre-tax impairment loss was recorded within Operating and maintenance expense on Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. Like-Kind Exchange Transaction (Exelon) Prior to the PECO/Unicom Merger in October 2000, UII, LLC (formerly Unicom Investments, Inc.) (UII), a wholly owned subsidiary of Exelon, entered into a like-kind exchange transaction pursuant to which approximately $1.6 billion was invested in coal-fired generating station leases located in Georgia and Texas with two separate entities unrelated to Exelon. The generating stations were leased back to such entities as part of the transaction. See Note 12 — Income Taxes for further information. The leases for the generating stations located in Texas were terminated in 2014. For financial accounting purposes, the investments are accounted for as direct financing lease investments. UII holds the leasehold interests in the generating stations in several separate bankruptcy remote, special purpose companies it directly or indirectly wholly owns. The lease agreements provide the lessees with fixed purchase options at the end of the lease terms. If the lessees do not exercise the fixed purchase options, Exelon has the ability to operate the stations and keep or market the power itself or require the lessees to arrange for a third-party to bid on a service contract for a period following the lease term. In any event, Exelon will be subject to residual value risk if the lessees do not exercise the fixed purchase options. This risk is partially mitigated by the fair value of the scheduled payments under the service contract. However, such payments are not guaranteed. Further, the term of the service contract is less than the expected remaining useful life of the plants and, therefore, Exelon’s exposure to residual value risk will not be mitigated by payments under the service contract in this remaining period. In the fourth quarter of 2000, under the terms of the lease agreements, UII received a prepayment of $1.2 billion for all rent, which reduced the investment in the leases. There are no minimum scheduled lease payments to be received over the remaining term of the leases. Pursuant to the applicable accounting guidance, Exelon is required to review the estimated residual values of its direct financing lease investments at least annually and record an impairment charge if the review indicates an other than temporary decline in the fair value of the residual values below their carrying values. Exelon estimates the fair value of the residual values of its direct financing lease investments under the income approach, which uses a discounted cash flow analysis, which takes into consideration significant unobservable inputs (Level 3) including the expected revenues to be generated and costs to be incurred to operate the plants over their remaining useful lives subsequent to the lease end dates. Significant assumptions used in estimating the fair value include fundamental energy and capacity prices, fixed and variable costs, capital expenditure requirements, discount rates, tax rates, and the estimated remaining useful lives of the plants. The estimated fair values also reflect the cash flows associated with the service contract option discussed above given that a market participant would take into consideration all of the terms and conditions contained in the lease agreements. Based on the annual reviews performed in the second quarters of 2015 and 2014 , the estimated residual value of Exelon’s direct financing leases for the Georgia generating stations experienced other than temporary declines given increases in estimated long-term operating and maintenance costs in the 2015 annual review and reduced long-term energy and capacity price expectations in the 2014 annual review. As a result, Exelon recorded $24 million pre-tax impairment charges in each of the second quarters of 2015 and 2014 for these stations. These impairment charges were recorded in Investments and Operating and maintenance expense in Exelon’s Consolidated Balance Sheets and the Consolidated Statements of Operations and Comprehensive Income, respectively. Changes in the assumptions described above could potentially result in future impairments of Exelon’s direct financing lease investments, which could be material. At September 30, 2015 and December 31, 2014 , the components of the net investment in long-term leases were as follows: September 30, 2015 December 31, 2014 Estimated residual value of leased assets $ 639 $ 685 Less: unearned income 291 324 Net investment in long-term leases $ 348 $ 361

Implications of Potential Early

Implications of Potential Early Plant Retirements Implications of Potential Early Plant Retirements (Exelon, Generation)	9 Months Ended
	Sep. 30, 2015
Implications of Potential Early Plant Retirements [Abstract]
Implications Of Potential Early Retirement Disclosure [Text Block]	8 . Implications of Potential Early Plant Retirements (Exelon and Generation) Exelon and Generation continue to evaluate the current and expected economic value of each of Generation’s nuclear plants. Factors that will continue to affect the economic value of Generation’s nuclear plants include, but are not limited to: market power prices, results of capacity auctions, potential legislative solutions in Illinois such as the proposed Low Carbon Portfolio Standard (LCPS) legislation, the impact of final rules from the U.S. EPA requiring reduction of carbon and other emissions and the efforts of the states to implement those final rules, and the outcome of the Ginna RSSA hearing and settlement procedures and the resulting contractual terms and conditions. On September 10, 2015, after considering the results of the recent PJM capacity auctions, Exelon and Generation decided to defer for one year any decisions about the future operations of its Quad Cities and Byron nuclear plants and will offer both plants in the 2019/2020 auction in May 2016. As a result of clearing the other PJM capacity auction in September 2015 for the 2017/2018 transitional capacity auction, Exelon and Generation will continue to operate its Quad Cities nuclear power plant through at least May 2018. The Byron plant is already obligated to operate through May 2019. In addition, on October 29, 2015, Exelon and Generation decided to defer any decision about the future operations of its Clinton nuclear plant for one year and plan to bid the plant into the MISO capacity auction for the 2016/2017 planning year in March 2016. MISO’s announcement on October 27, 2015 acknowledging the need for market design changes in southern Illinois was a key factor in Exelon’s and Generation’s decision to defer for an additional year, among other factors such as positive results from the Illinois Power Agency’s capacity procurement for 2016 and the long-term impact of the EPA’s Clean Power Plan. The Clinton plant is currently obligated to operate through May 2016. Exelon and Generation previously committed to cease operation of the Oyster Creek nuclear plant by the end of 2019. Exelon and Generation have not made any decisions regarding potential nuclear plant closures at other sites at this time. As a result of a decision to early retire one or more other nuclear plants, certain changes in accounting treatment would be triggered and Exelon’s and Generation’s results of operations and cash flows could be materially affected by a number of items including, among other items: accelerated depreciation expense, impairment charges related to inventory that cannot be used at other nuclear units and cancellation of in-flight capital projects, accelerated amortization of plant specific nuclear fuel costs, severance costs, accelerated asset retirement obligation expense related to future decommissioning activities, and additional funding of decommissioning costs. In addition, any early plant retirement would also result in reduced operating costs, lower fuel expense, and lower capital expenditures in the periods beyond shutdown. While there are a number of Generation’s nuclear plants that are at risk of early retirement, the following table provides the balance sheet amounts as of September 30, 2015 for significant assets and liabilities associated with the three nuclear plants currently considered by management to be at the greatest risk of early retirement due to their current economic valuations and other factors: (in millions) Quad Cities Clinton Ginna Total Asset Balances Materials and supplies inventory $ 49 $ 56 $ 30 $ 135 Nuclear fuel inventory, net 186 122 65 373 Completed plant, net 1,027 582 111 1,720 Construction work in progress 29 8 23 60 Liability Balances Asset retirement obligation (696 ) (396 ) (637 ) (1,729 ) NRC License Renewal Term 2032 2046 (a) 2029 ________ (a) Assumes Clinton seeks and receives a 20-year operating license renewal extension. In the event a decision is made to early retire one or more nuclear plants, the precise timing of the retirement date, and resulting financial statement impact, is uncertain and would be influenced by a number of factors such as the results of any transmission system reliability study assessments, the nature of any co-owner requirements and stipulations, and decommissioning trust fund requirements, among other factors. However, the earliest retirement date for any plant would usually be the first year in which the unit does not have capacity obligations and just prior to its next scheduled nuclear refueling outage date in that year.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities (Exelon, Generation, ComEd, PECO and BGE)	Fair Value of Financial Assets and Liabilities (Exelon, Generation, ComEd, PECO and BGE) Fair Value of Financial Liabilities Recorded at the Carrying Amount The following tables present the carrying amounts and fair values of the Registrants’ short-term liabilities, long-term debt, SNF obligation, and trust preferred securities (long-term debt to financing trusts or junior subordinated debentures) as of September 30, 2015 and December 31, 2014 : Exelon September 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 678 $ 3 $ 675 $ — $ 678 Long-term debt (including amounts due within one year) 25,438 1,004 24,181 1,335 26,520 Long-term debt to financing trusts 648 — — 663 663 SNF obligation 1,021 — 820 — 820 December 31, 2014 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 463 $ 3 $ 448 $ 12 $ 463 Long-term debt (including amounts due within one year) 21,164 1,208 20,417 1,311 22,936 Long-term debt to financing trusts 648 — — 648 648 SNF obligation 1,021 — 833 — 833 Generation September 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 21 $ — $ 21 $ — $ 21 Long-term debt (including amounts due within one year) 8,996 — 7,978 1,335 9,313 SNF obligation 1,021 — 820 — 820 December 31, 2014 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 36 $ — $ 24 $ 12 $ 36 Long-term debt (including amounts due within one year) 8,266 — 7,511 1,311 8,822 SNF obligation 1,021 — 833 — 833 ComEd September 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 604 $ — $ 604 $ — $ 604 Long-term debt (including amounts due within one year) 6,100 — 6,731 — 6,731 Long-term debt to financing trust 206 — — 206 206 December 31, 2014 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 304 $ — $ 304 $ — $ 304 Long-term debt (including amounts due within one year) 5,958 — 6,788 — 6,788 Long-term debt to financing trust 206 — — 213 213 PECO September 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) $ 2,246 $ — $ 2,472 $ — $ 2,472 Long-term debt to financing trusts 184 — — 196 196 December 31, 2014 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) $ 2,246 $ — $ 2,537 $ — $ 2,537 Long-term debt to financing trusts 184 — — 199 199 BGE September 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 53 $ 3 $ 50 $ — $ 53 Long-term debt (including amounts due within one year) 1,905 — 2,118 — 2,118 Long-term debt to financing trusts 258 — — 261 261 December 31, 2014 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 123 $ 3 $ 120 $ — $ 123 Long-term debt (including amounts due within one year) 1,942 — 2,178 — 2,178 Long-term debt to financing trusts 258 — — 236 236 Short-Term Liabilities. The short-term liabilities included in the tables above are comprised of dividends payable (included in other current liabilities) (Level 1), short-term borrowings (Level 2) and third party financing (Level 3). The Registrants’ carrying amounts of the short-term liabilities are representative of fair value because of the short-term nature of these instruments. Long-Term Debt. The fair value amounts of Exelon’s taxable debt securities (Level 2) are determined by a valuation model that is based on a conventional discounted cash flow methodology and utilizes assumptions of current market pricing curves. In order to incorporate the credit risk of the Registrants into the discount rates, Exelon obtains pricing (i.e., U.S. Treasury rate plus credit spread) based on trades of existing Exelon debt securities as well as debt securities of other issuers in the electric utility sector with similar credit ratings in both the primary and secondary market, across the Registrants’ debt maturity spectrum. The credit spreads of various tenors obtained from this information are added to the appropriate benchmark U.S. Treasury rates in order to determine the current market yields for the various tenors. The yields are then converted into discount rates of various tenors that are used for discounting the respective cash flows of the same tenor for each bond or note. The fair value of Exelon's equity units (Level 1) are valued based on publicly traded securities issued by Exelon. The fair value of Generation’s non-government-backed fixed rate project financing debt, including nuclear fuel procurement contracts, (Level 3) is based on market and quoted prices for its own and other project financing debt with similar risk profiles. Given the low trading volume in the project financing debt market, the price quotes used to determine fair value will reflect certain qualitative factors, such as market conditions, investor demand, new developments that might significantly impact the project cash flows or off-taker credit, and other circumstances related to the project (e.g., political and regulatory environment). The fair value of Generation’s government-backed fixed rate project financing debt (Level 3) is largely based on a discounted cash flow methodology that is similar to the taxable debt securities methodology described above. Due to the lack of market trading data on similar debt, the discount rates are derived based on the original loan interest rate spread to the applicable Treasury rate as well as a current market curve derived from government-backed securities. Variable rate project financing debt resets on a quarterly basis and the carrying value approximates fair value (Level 2). Generation also has tax-exempt debt (Level 2). Due to low trading volume in this market, qualitative factors, such as market conditions, investor demand, and circumstances related to the issuer (e.g., conduit issuer political and regulatory environment), may be incorporated into the credit spreads that are used to obtain the fair value as described above. SNF Obligation. The carrying amount of Generation’s SNF obligation (Level 2) is derived from a contract with the DOE to provide for disposal of SNF from Generation’s nuclear generating stations. When determining the fair value of the obligation, the future carrying amount of the SNF obligation estimated to be settled in 2025 is calculated by compounding the current book value of the SNF obligation at the 13-week Treasury rate. The compounded obligation amount is discounted back to present value using Generation’s discount rate, which is calculated using the same methodology as described above for the taxable debt securities, and an estimated maturity date of 2025. Long-Term Debt to Financing Trusts. Exelon’s long-term debt to financing trusts is valued based on publicly traded securities issued by the financing trusts. Due to low trading volume of these securities, qualitative factors, such as market conditions, investor demand, and circumstances related to each issue, this debt is classified as Level 3. Recurring Fair Value Measurements Exelon records the fair value of assets and liabilities in accordance with the hierarchy established by the authoritative guidance for fair value measurements. The hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels as follows: • Level 1 — quoted prices (unadjusted) in active markets for identical assets or liabilities that the Registrants have the ability to liquidate as of the reporting date. • Level 2 — inputs other than quoted prices included within Level 1 that are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. • Level 3 — unobservable inputs, such as internally developed pricing models or third-party valuations for the asset or liability due to little or no market activity for the asset or liability. Transfers in and out of levels are recognized as of the end of the reporting period when the transfer occurred. Given derivatives categorized within Level 1 are valued using exchange-based quoted prices within observable periods, transfers between Level 2 and Level 1 were not material. Transfers into Level 2 from Level 3 generally occur when the contract tenure becomes more observable. Transfers into Level 3 from Level 2 generally occur due to changes in market liquidity or assumptions for certain commodity contracts. There were no transfers between Level 1 and Level 2 during the nine months ended September 30, 2015 for cash equivalents, nuclear decommissioning trust fund investments, pledged assets for Zion Station decommissioning, Rabbi trust investments, and deferred compensation obligations. Exelon and Generation The following tables present assets and liabilities measured and recorded at fair value on Exelon's and Generation’s Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of September 30, 2015 and December 31, 2014 : Generation Exelon As of September 30, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 225 $ — $ — $ 225 $ 6,545 $ — $ — $ 6,545 Nuclear decommissioning trust fund investments Cash equivalents 301 67 — 368 301 67 — 368 Equity Domestic 2,274 1,829 — 4,103 2,274 1,829 — 4,103 Foreign 598 — — 598 598 — — 598 Equity funds subtotal 2,872 1,829 — 4,701 2,872 1,829 — 4,701 Fixed income Corporate debt — 1,831 245 2,076 — 1,831 245 2,076 Generation Exelon As of September 30, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total U.S. Treasury and agencies 1,142 — — 1,142 1,142 — — 1,142 Foreign governments — 77 — 77 — 77 — 77 State and municipal debt — 407 — 407 — 407 — 407 Other — 468 — 468 — — 468 — — — 468 Fixed income subtotal 1,142 2,783 245 4,170 1,142 2,783 245 4,170 Middle market lending — — 423 423 — — 423 423 Private equity — — 116 116 — — 116 116 Real estate — — 30 30 — — — — 30 30 Other — 329 — 329 — 329 — 329 Nuclear decommissioning trust fund investments subtotal (b) 4,315 5,008 814 10,137 4,315 5,008 814 10,137 Pledged assets for Zion Station decommissioning Cash equivalents — 11 — 11 — 11 — 11 Equities 5 1 — 6 5 1 — 6 Fixed income U.S. Treasury and agencies 5 2 — 7 5 2 — 7 Corporate debt — 57 — 57 — 57 — 57 State and municipal debt — 10 — 10 — 10 — 10 Other — 1 — 1 — — 1 — — 1 Fixed income subtotal 5 70 — 75 5 70 — 75 Middle market lending — — 144 144 — — 144 144 Pledged assets for Zion Station decommissioning subtotal (c) 10 82 144 236 10 82 144 236 Rabbi trust investments in mutual funds (d)(e) 16 — — 16 46 — — 46 Commodity derivative assets Economic hedges 1,625 2,561 2,144 6,330 1,625 2,561 2,144 6,330 Proprietary trading 85 140 38 263 85 140 38 263 Effect of netting and allocation of collateral (f) (1,865 ) (2,037 ) (835 ) (4,737 ) (1,865 ) (2,037 ) (835 ) (4,737 ) Commodity derivative assets subtotal (155 ) 664 1,347 1,856 (155 ) 664 1,347 1,856 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — 37 — 37 Economic hedges — 21 — 21 — 21 — 21 Proprietary trading 14 3 — 17 14 3 — 17 Effect of netting and allocation of collateral (8 ) (6 ) — (14 ) (8 ) (6 ) — (14 ) Interest rate and foreign currency derivative assets subtotal 6 18 — 24 6 55 — 61 Other investments — — 32 32 — — 32 32 Total assets 4,417 5,772 2,337 12,526 10,767 5,809 2,337 18,913 Generation Exelon As of September 30, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Liabilities Commodity derivative liabilities Economic hedges (2,120 ) (2,478 ) (1,209 ) (5,807 ) (2,120 ) (2,478 ) (1,452 ) (6,050 ) Proprietary trading (79 ) (140 ) (44 ) (263 ) (79 ) (140 ) (44 ) (263 ) Effect of netting and allocation of collateral (f) 2,218 2,472 1,080 5,770 2,218 2,472 1,080 5,770 Commodity derivative liabilities subtotal 19 (146 ) (173 ) (300 ) 19 (146 ) (416 ) (543 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (21 ) — (21 ) — (21 ) — (21 ) Economic hedges — (6 ) — (6 ) — (6 ) — (6 ) Proprietary trading (15 ) — — (15 ) (15 ) — — (15 ) Effect of netting and allocation of collateral 15 6 — 21 15 6 — 21 Interest rate and foreign currency derivative liabilities subtotal — (21 ) — (21 ) — (21 ) — (21 ) Deferred compensation obligation — (29 ) — (29 ) — (95 ) — (95 ) Total liabilities 19 (196 ) (173 ) (350 ) 19 (262 ) (416 ) (659 ) Total net assets $ 4,436 $ 5,576 $ 2,164 $ 12,176 $ 10,786 $ 5,547 $ 1,921 $ 18,254 Generation Exelon As of December 31, 2014 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 405 $ — $ — $ 405 $ 1,119 $ — $ — $ 1,119 Nuclear decommissioning trust fund investments Cash equivalents 208 37 — 245 208 37 — 245 Equity Domestic 2,423 2,207 — 4,630 2,423 2,207 — 4,630 Foreign 612 — — 612 612 — — 612 Equity funds subtotal 3,035 2,207 — 5,242 3,035 2,207 — 5,242 Fixed income Corporate debt — 2,023 239 2,262 — 2,023 239 2,262 U.S. Treasury and agencies 996 — — 996 996 — — 996 Foreign governments — 95 — 95 — 95 — 95 State and municipal debt — 438 — 438 — 438 — 438 Other — 511 — 511 — — 511 — — 511 Fixed income subtotal 996 3,067 239 4,302 996 3,067 239 4,302 Middle market lending — — 366 366 — — 366 366 Private equity — — 83 83 — — 83 83 Real estate — — 3 3 — — — — 3 3 Other — 301 — 301 — 301 — 301 Nuclear decommissioning trust fund investments subtotal (b) 4,239 5,612 691 10,542 4,239 5,612 691 10,542 Pledged assets for Zion Station decommissioning Cash equivalents — 15 — 15 — 15 — 15 Equities 6 1 — 7 6 1 — 7 Fixed income U.S. Treasury and agencies 5 3 — 8 5 3 — 8 Corporate debt — 89 — 89 — 89 — 89 State and municipal debt — 10 — 10 — 10 — 10 Other — 3 — 3 — — 3 — — 3 Fixed income subtotal 5 105 — 110 5 105 — 110 Middle market lending — — 184 184 — — 184 184 Generation Exelon As of December 31, 2014 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Pledged assets for Zion Station decommissioning subtotal (c) 11 121 184 316 11 121 184 316 Rabbi trust investments (d) Cash equivalents — — — — 1 — — 1 Mutual funds (e) 16 — — 16 46 — — 46 Rabbi trust investments subtotal 16 — — 16 47 — — 47 Commodity derivative assets Economic hedges 1,667 3,465 1,681 6,813 1,667 3,465 1,681 6,813 Proprietary trading 201 284 27 512 201 284 27 512 Effect of netting and allocation of collateral (f) (1,982 ) (2,757 ) (557 ) (5,296 ) (1,982 ) (2,757 ) (557 ) (5,296 ) Commodity derivative assets subtotal (114 ) 992 1,151 2,029 (114 ) 992 1,151 2,029 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — 8 — 8 — 31 — 31 Economic hedges — 12 — 12 — 13 — 13 Proprietary trading 18 9 — 27 18 9 — 27 Effect of netting and allocation of collateral (17 ) (12 ) — (29 ) (17 ) (31 ) — (48 ) Interest rate and foreign currency derivative assets subtotal 1 17 — 18 1 22 — 23 Other investments — — 3 3 2 — 3 5 Total assets 4,558 6,742 2,029 13,329 5,305 6,747 2,029 14,081 Liabilities Commodity derivative liabilities Economic hedges (2,241 ) (3,458 ) (788 ) (6,487 ) (2,241 ) (3,458 ) (995 ) (6,694 ) Proprietary trading (195 ) (295 ) (42 ) (532 ) (195 ) (295 ) (42 ) (532 ) Effect of netting and allocation of collateral (f) 2,416 3,557 729 6,702 2,416 3,557 729 6,702 Commodity derivative liabilities subtotal (20 ) (196 ) (101 ) (317 ) (20 ) (196 ) (308 ) (524 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (12 ) — (12 ) — (41 ) — (41 ) Economic hedges — (2 ) — (2 ) — (103 ) — (103 ) Proprietary trading (14 ) (9 ) — (23 ) (14 ) (9 ) — (23 ) Effect of netting and allocation of collateral 25 10 — 35 25 29 — 54 Interest rate and foreign currency derivative liabilities subtotal 11 (13 ) — (2 ) 11 (124 ) — (113 ) Deferred compensation obligation — (31 ) — (31 ) — (107 ) — (107 ) Total liabilities (9 ) (240 ) (101 ) (350 ) (9 ) (427 ) (308 ) (744 ) Total net assets $ 4,549 $ 6,502 $ 1,928 $ 12,979 $ 5,296 $ 6,320 $ 1,721 $ 13,337 ______________ (a) Excludes certain cash equivalents considered to be held-to-maturity and not reported at fair value. (b) Excludes net liabilities of $(34) million and $(5) million at September 30, 2015 and December 31, 2014 , respectively. These items consist of net receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases. (c) Excludes net assets of $1 million and $3 million at September 30, 2015 and December 31, 2014 , respectively. These items consist of net receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases. (d) Excludes $34 million and $35 million of cash surrender value of life insurance investment at September 30, 2015 and December 31, 2014 , respectively, at Exelon Consolidated. Excludes $12 million and $11 million and of cash surrender value of life insurance investment at September 30, 2015 and December 31, 2014 , respectively, at Generation. (e) The mutual funds held by the Rabbi trusts at Exelon include $45 million related to deferred compensation and $1 million related to Supplemental Executive Retirement Plan at September 30, 2015 , and $45 million related to deferred compensation and $1 million related to Supplemental Executive Retirement Plan at December 31, 2014 . (f) Collateral posted to/(received from) counterparties totaled $353 million , $435 million and $245 million allocated to Level 1, Level 2 and Level 3 commodity mark-to-market derivatives, respectively, as of September 30, 2015 . Collateral posted to/(received from) counterparties totaled $434 million , $800 million and $172 million allocated to Level 1, Level 2 and Level 3 commodity mark-to-market derivatives, respectively, as of December 31, 2014 . ComEd, PECO and BGE The following tables present assets and liabilities measured and recorded at fair value on the utility Registrants' Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of September 30, 2015 and December 31, 2014 : ComEd PECO BGE As of September 30, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents $ — $ — $ — $ — $ 4 $ — $ — $ 4 $ 68 $ — $ — $ 68 Rabbi trust investments in mutual funds (a) — — — — 8 — — 8 5 — — 5 Total assets — — — — 12 — — 12 73 — — 73 Liabilities Deferred compensation obligation — (7 ) — (7 ) — (11 ) — (11 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (243 ) (243 ) — — — — — — — — Total liabilities — (7 ) (243 ) (250 ) — (11 ) — (11 ) — (4 ) — (4 ) Total net assets (liabilities) $ — $ (7 ) $ (243 ) $ (250 ) $ 12 $ (11 ) $ — $ 1 $ 73 $ (4 ) $ — $ 69 ComEd PECO BGE As of December 31, 2014 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents $ 25 $ — $ — $ 25 $ 12 $ — $ — $ 12 $ 103 $ — $ — $ 103 Rabbi trust investments in mutual funds (a) — — — — 9 — — 9 5 — — $ 5 Total assets 25 — — 25 21 — — 21 108 — — 108 Liabilities Deferred compensation obligation — (8 ) — (8 ) — (15 ) — (15 ) — (5 ) — (5 ) Mark-to-market derivative liabilities (b) — — (207 ) (207 ) — — — — — — — — Total liabilities — (8 ) (207 ) (215 ) — (15 ) — (15 ) — (5 ) — (5 ) Total net assets (liabilities) $ 25 $ (8 ) $ (207 ) $ (190 ) $ 21 $ (15 ) $ — $ 6 $ 108 $ (5 ) $ — $ 103 ______________ (a) At PECO, excludes $12 million and $14 million of the cash surrender value of life insurance investments at September 30, 2015 and December 31, 2014 , respectively. (b) The Level 3 balance includes the current and noncurrent liability of $ 22 million and $ 221 million at September 30, 2015 , respectively, and $20 million and $187 million at December 31, 2014 , respectively, related to floating-to-fixed energy swap contracts with unaffiliated suppliers. The following table presents the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2015 and 2014 : Generation ComEd Exelon Three Months Ended September 30, 2015 Nuclear Decommissioning Trust Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives (b) Eliminated in Consolidation Total Balance as of June 30, 2015 $ 786 $ 156 $ 1,021 $ 30 $ 1,993 $ (223 ) $ — $ 1,770 Total realized / unrealized gains (losses) Included in net income — — (48 ) (a) — (48 ) — — (48 ) Included in noncurrent payables to affiliates 5 — — — 5 — (5 ) — Included in payable for Zion Station decommissioning — 1 — — 1 — — 1 Included in regulatory assets — — — — — (20 ) 5 (15 ) Change in collateral — — 90 — 90 — — 90 Purchases, sales, issuances and settlements Purchases 40 5 50 2 97 — — 97 Sales — (18 ) (5 ) — (23 ) — — (23 ) Settlements (17 ) — — — (17 ) — — (17 ) Transfers into Level 3 — — 69 — 69 — — 69 Transfers out of Level 3 — — (3 ) — (3 ) — — (3 ) Balance as of September 30, 2015 $ 814 $ 144 $ 1,174 $ 32 $ 2,164 $ (243 ) $ — $ 1,921 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held for the three months ended September 30, 2015 $ (1 ) $ — $ 181 $ — $ 180 $ — $ — $ 180 Generation ComEd Exelon Nine Months Ended September 30, 2015 Nuclear Decommissioning Trust Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives (b) Eliminated in Consolidation Total Balance as of December 31, 2014 $ 691 $ 184 $ 1,050 $ 3 $ 1,928 $ (207 ) $ — $ 1,721 Total realized / unrealized gains (losses) Included in net income 4 — (87 ) (a) — (83 ) — — (83 ) Included in noncurrent payables to affiliates 20 — — — 20 — (20 ) — Included in payable for Zion Station decommissioning — 2 — — 2 — — 2 Included in regulatory assets — — — — — (36 ) 20 (16 ) Change in collateral — — 72 — 72 — — 72 Purchases, sales, issuances and settlements Purchases 186 16 107 29 338 — — 338 Sales (8 ) (58 ) (10 ) — (76 ) — — (76 ) Settlements (83 ) — — — (83 ) — — (83 ) Transfers into Level 3 4 — 80 — 84 — — 84 Transfers out of Level 3 — — (38 ) — (38 ) — — (38 ) Balance as of September 30, 2015 $ 814 $ 144 $ 1,174 $ 32 $ 2,164 $ (243 ) $ — $ 1,921 The amount of total gains included in income attributed to the change in unrealized gains related to assets and liabilities held for the nine months ended September 30, 2015 $ 4 $ — $ 536 $ — $ 540 $ — $ — $ 540 ______________ (a) Includes a reduction for the reclassification of $229 million and $623 million of realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2015 , respectively. (b) Includes $19 million of decreases in fair value and a reduction for realized gains due to settlements of $1 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2015 . Includes $44 million of decreases in fair value and an increase for realized losses due to settlements of $8 million for the nine months ended September 30, 2015 . Generation ComEd Exelon Three Months Ended September 30, 2014 Nuclear Decommissioning Trust Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives (b) Eliminated in Consolidation Total Balance as of June 30, 2014 $ 592 $ 133 $ 242 $ 10 $ 977 $ (134 ) $ — $ 843 Total realized / unrealized gains (losses) Included in net income 1 — 76 (a) — 77 — — 77 Included in noncurrent payables to affiliates 3 — — — 3 — (3 ) — Included in payable for Zion Station decommissioning — (2 ) — — (2 ) — — (2 ) Included in regulatory assets — — — — — (44 ) 3 (41 ) Change in collateral — — 79 — 79 — — 79 Purchases, sales, issuances and settlements Purchases 83 53 12 — 148 — — 148 Sales (8 ) (18 ) — (7 ) (33 ) — — (33 ) Settlements (27 ) — — — (27 ) — — (27 ) Transfers into Level 3 — — 21 — 21 — — 21 Transfers out of Level 3 — — 1 — 1 — — 1 Balance as of September 30, 2014 $ 644 $ 166 $ 431 $ 3 $ 1,244 $ (178 ) $ — $ 1,066 The amount of total gains included in income attributed to the change in unrealized gains related to assets and liabilities held for the three months ended September 30, 2014 $ 1 $ — $ 163 $ — $ 164 $ — $ — $ 164 Generation ComEd Exelon Nine Months Ended September 30, 2014 Nuclear Decommissioning Trust Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to- Market Derivatives (b) Eliminated in Consolidation Total Balance as of December 31, 2013 $ 350 $ 112 $ 465 $ 15 $ 942 $ (193 ) $ — $ 749 Total realized / unrealized gains (losses) Included in net income 5 — (284 ) (a) — (279 ) — — $ (279 ) Included in noncurrent payables to affiliates 14 — — — 14 — (14 ) $ — Included in payable for Zion Station decommissioning — 2 — — 2 — — $ 2 Included in regulatory assets — — — — — 15 14 $ 29 Change in collateral — — 257 — 257 — — $ 257 Purchases, sales, issuances and settlements Purchases 331 95 27 2 455 — — $ 455 Sales (10 ) (43 ) (6 ) (7 ) (66 ) — — $ (66 ) Settlements (46 ) — — — (46 ) — — $ (46 ) Transfers into Level 3 — — (9 ) — (9 ) — — $ (9 ) Transfers out of Level 3 — — (19 ) (7 ) (26 ) — — $ (26 ) Balance as of September 30, 2014 $ 644 $ 166 $ 431 $ 3 $ 1,244 $ (178 ) $ — $ 1,066 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held for the nine months ended September 30, 2014 $ 3 $ — $ (264 ) $ — $ (261 ) $ — $ — $ (261 ) ______________ (a) Includes a reduction for the reclassification of $ 87 million and $20 million of realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2014. (b) Includes $45 million of decreases in fair value and an increase for realized losses due to settlements of $1 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2014 . Includes $19 million of increases in fair value and a reduction for realized gains due to settlements of $4 million for the nine months ended September 30, 2014 . The following tables present the income statement classification of the total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2015 and 2014 : Generation Exelon Operating Revenues Purchased Power and Fuel Other, net (a) Operating Revenues Purchased Power and Fuel Other, net (a) Total gains (losses) included in net income for the three months ended September 30, 2015 $ (4 ) $ (44 ) $ — $ (4 ) $ (44 ) $ — Total gains (losses) included in net income for the nine months ended September 30, 2015 (31 ) (56 ) 4 (31 ) (56 ) 4 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended September 30, 2015 198 (17 ) (1 ) 198 (17 ) (1 ) Change in the unrealized gains (losses) relating to assets and liabilities held for the nine months ended September 30, 2015 538 (2 ) 4 538 (2 ) 4 Generation Exelon Operating Revenues Purchased Power and Fuel Other, net (a) Operating Revenues Purchased Power and Fuel Other, net (a) Total gains (losses) included in net income for the three months ended September 30, 2014 $ 70 $ 6 $ 1 $ 70 $ 6 $ 1 Total gains (losses) included in net income for the nine months ended September 30, 2014 (260 ) (24 ) 5 (260 ) (24 ) 5 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended September 30, 2014 142 21 1 142 21 1 Change in the unrealized gains (losses) relating to assets and liabilities held for the nine months ended September 30, 2014 (293 ) 29 3 (293 ) 29 3 ______________ (a) Other, net activity consists of realized and unrealized gains (losses) included in income for the NDT funds held by Generation. Valuation Techniques Used to Determine Fair Value The following describes the valuation techniques used to measure the fair value of the assets and liabilities shown in the tables above. Cash Equivalents (Exelon, Generation, ComEd, PECO and BGE). The Registrants’ cash equivalents include investments with maturities of three months or less when purchased. The cash equivalents shown in the fair value tables are comprised of investments in mutual and money market funds. The fair values of the shares of these funds are based on observable market prices and, therefore, have been categorized in Level 1 in the fair value hierarchy. Nuclear Decommissioning Trust Fund Investments and Pledged Assets for Zion Station Decommissioning (Exelon and Generation). The trust fund investments have been established to satisfy Generation’s and CENG's nuclear decommissioning obligations as required by the NRC. The NDT funds hold debt and equity securities directly and indirectly through commingled funds and mutual funds, which are included in Equities, Fixed Income and Other. Generation’s and CENG's NDT fund investments policies outline investment guidelines for the trusts and limit the trust funds’ exposures to investments in highly illiquid markets and other alternative investments. Investments with maturities of three months or less when purchased, including certain short-term fixed income securities are considered cash equivalents and included in the recurring fair value measurements hierarchy as Level 1 or Level 2. With respect to individually held equity securities, which are included in Domestic or Foreign equities, the trustees obtain prices from pricing services, whose prices are obtained from direct feeds from market exchanges, which Generation is able to independently corroborate. The fair values of equity securities held directly by the trust funds are based on quoted prices in active markets and are categorized in Level 1. Equity securities held individually are primarily traded on the New York Stock Exchange and NASDAQ-Global Select Market, which contain only actively traded securities due to the volume trading requirements imposed by these exchanges. For fixed income securities, multiple prices from pricing services are obtained whenever possible, which enables cross-provider validations in addition to checks for unusual daily movements. A primary price source is identified based on asset type, class or issue for each security. The trustees monitor prices supplied by pricing services and may use a supplemental price source or change the primary price source of a given security if the portfolio managers challenge an assigned price and the trustees determine that another price source is considered to be preferable. Generation has obtained an understanding of how these prices are derived, including the nature and observability of the inputs used in deriving such prices. Additionally, Generation selectively corroborates the fair values of securities by comparison to other market-based price sources. U.S. Treasury securities are categorized as Level 1 because they trade in a highly liquid and transparent market. The fair values of fixed income securities, excluding U.S. Treasury securities, are based on evaluated prices that reflect observable market information, such as actual trade information or similar securities, adjusted for observable differences and are categorized in Level 2. The fair values of private placement fixed income securities, which are included in Corporate debt, are determined using a third party valuation that contains significant unobservable inputs and are categorized in Level 3. Equity, balanced and fixed income commingled funds and fixed income mutual funds are maintained by investment companies and hold certain investments in accordance with a stated set of fund objectives. The fair values of fixed income commingled and mutual funds held within the trust funds, which generally hold fixed income securities and are not subject to restrictions regarding the purchase or sale of shares, are derived from observable prices. The objectives of the remaining equity commingled funds in which Exelon, Generation, and CENG invest primarily seek to track the performance of certain equity indices by purchasing equity securities to replicate the capitalization and characteristics of the indices. Commingled and mutual funds are categorized i

Derivative Financial Instrument

Derivative Financial Instruments (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments (Exelon, Generation, ComEd, PECO and BGE)	Derivative Financial Instruments (Exelon, Generation, ComEd, PECO and BGE) The Registrants use derivative instruments to manage commodity price risk, foreign currency exchange rate risk, and interest rate risk related to ongoing business operations. Commodity Price Risk (Exelon, Generation, ComEd, PECO and BGE) To the extent the amount of energy Generation produces differs from the amount of energy it has contracted to sell, Exelon and Generation are exposed to market fluctuations in the prices of electricity, fossil fuels and other commodities. Each of the Registrants employ established policies and procedures to manage their risks associated with market fluctuations in commodity prices by entering into physical and financial derivative contracts, including swaps, futures, forwards, options and short-term and long-term commitments to purchase and sell energy and energy-related products. The Registrants believe these instruments, which are classified as either economic hedges or non-derivatives, mitigate exposure to fluctuations in commodity prices. Derivative accounting guidance requires that derivative instruments be recognized as either assets or liabilities at fair value, with changes in fair value of the derivative recognized in earnings each period. Other accounting treatments are available through special election and designation, provided they meet specific, restrictive criteria both at the time of designation and on an ongoing basis. These alternative permissible accounting treatments include normal purchase normal sale (NPNS), cash flow hedge, and fair value hedge. For commodity transactions, Generation no longer utilizes the special election provided for by the cash flow hedge designation and de-designated all of its existing cash flow hedges prior to the Constellation merger. Because the underlying forecasted transactions remained probable, the fair value of the effective portion of these cash flow hedges was frozen in Accumulated OCI and was reclassified to results of operations when the forecasted purchase or sale of the energy commodity occurred. The effect of this decision is that all derivative economic hedges related to commodities are recorded at fair value through earnings for the combined company, referred to as economic hedges in the following tables. The Registrants have applied the NPNS scope exception to certain derivative contracts for the forward sale of generation, power procurement agreements, and natural gas supply agreements. Non-derivative contracts for access to additional generation and certain sales to load-serving entities are accounted for primarily under the accrual method of accounting, which is further discussed in Note 22 — Commitments and Contingencies of the Exelon 2014 Form 10-K. Additionally, Generation is exposed to certain market risks through its proprietary trading activities. The proprietary trading activities are a complement to Generation’s energy marketing portfolio but represent a small portion of Generation’s overall energy marketing activities. Economic Hedging. The Registrants are exposed to commodity price risk primarily relating to changes in the market price of electricity, fossil fuels, and other commodities associated with price movements resulting from changes in supply and demand, fuel costs, market liquidity, weather conditions, governmental regulatory and environmental policies, and other factors. Within Exelon, Generation has the most exposure to commodity price risk. As such, Generation uses a variety of derivative and non-derivative instruments to manage the commodity price risk of its electric generation facilities, including power and gas sales, fuel and energy purchases, natural gas transportation and pipeline capacity agreements and other energy-related products marketed and purchased. In order to manage these risks, Generation may enter into fixed-price derivative or non-derivative contracts to hedge the variability in future cash flows from forecasted sales of energy and gas and purchases of fuel and energy. The objectives for entering into such hedges include fixing the price for a portion of anticipated future electricity sales at a level that provides an acceptable return on electric generation operations, fixing the price of a portion of anticipated fuel purchases for the operation of power plants, and fixing the price for a portion of anticipated energy purchases to supply load-serving customers. The portion of forecasted transactions hedged may vary based upon management’s policies and hedging objectives, the market, weather conditions, operational and other factors. Generation is also exposed to differences between the locational settlement prices of certain economic hedges and the hedged generating units. This price difference is actively managed through other instruments which include derivative congestion products, whose changes in fair value are recognized in earnings each period, and auction revenue rights, which are accounted for on an accrual basis. In general, increases and decreases in forward market prices have a positive and negative impact, respectively, on Generation’s owned and contracted generation positions that have not been hedged. Generation hedges commodity price risk on a ratable basis over three-year periods. As of September 30, 2015 , the proportion of expected generation hedged for the major reportable segments was 97% - 100% , 81% - 84% , and 51% - 54% for 2015, 2016, and 2017, respectively. The percentage of expected generation hedged is the amount of equivalent sales divided by the expected generation. Expected generation is the volume of energy that best represents our commodity position in energy markets from owned or contracted for capacity based upon a simulated dispatch model that makes assumptions regarding future market conditions, which are calibrated to market quotes for power, fuel, load following products, and options. Equivalent sales represent all hedging products, which include economic hedges and certain non-derivative contracts including Generation’s sales to ComEd, PECO and BGE to serve their retail load. On December 17, 2010, ComEd entered into several 20 -year floating-to-fixed energy swap contracts with unaffiliated suppliers for the procurement of long-term renewable energy and associated RECs. Delivery under the contracts began in June 2012. Pursuant to the ICC’s Order on December 19, 2012, ComEd’s commitments under the existing long-term contracts for energy and associated RECs were reduced for the June 2013 through May 2014 procurement period. In addition, the ICC’s December 18, 2013 Order approved the reduction of ComEd’s commitments under those contracts for the June 2014 through May 2015 procurement period, and the amount of the reductions was approved in March 2014. These contracts are designed to lock in a portion of the long-term commodity price risk resulting from the renewable energy resource procurement requirements in the Illinois Settlement Legislation. ComEd has not elected hedge accounting for these derivative financial instruments. ComEd records the fair value of the swap contracts on its balance sheet. Because ComEd receives full cost recovery for energy procurement and related costs from retail customers, the change in fair value each period is recorded by ComEd as a regulatory asset or liability. See Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K for additional information. PECO has contracts to procure electric supply that were executed through the competitive procurement process outlined in its PAPUC-approved DSP Programs, which are further discussed in Note 5 — Regulatory Matters . Based on Pennsylvania legislation and the DSP Programs permitting PECO to recover its electric supply procurement costs from retail customers with no mark-up, PECO’s price risk related to electric supply procurement is limited. PECO locked in fixed prices for a significant portion of its commodity price risk through full requirements contracts and block contracts. PECO has certain full requirements contracts and block contracts that are considered derivatives and qualify for the NPNS scope exception under current derivative authoritative guidance. PECO’s natural gas procurement policy is designed to achieve a reasonable balance of long-term and short-term gas purchases under different pricing approaches in order to achieve system supply reliability at the least cost. PECO’s reliability strategy is two-fold. First, PECO must assure that there is sufficient transportation capacity to satisfy delivery requirements. Second, PECO must ensure that a firm source of supply exists to utilize the capacity resources. All of PECO’s natural gas supply and asset management agreements that are derivatives either qualify for the NPNS scope exception and have been designated as such, or have no mark-to-market balances because the derivatives are index priced. Additionally, in accordance with the 2015 PAPUC PGC settlement and to reduce the exposure of PECO and its customers to natural gas price volatility, PECO has continued its program to purchase natural gas for both winter and summer supplies using a layered approach of locking-in prices ahead of each season with long-term gas purchase agreements (those with primary terms of at least twelve months). Under the terms of the 2015 PGC settlement, PECO is required to lock in (i.e., economically hedge) the price of a minimum volume of its long-term gas commodity purchases. PECO’s gas-hedging program is designed to cover about 30% of planned natural gas purchases in support of projected firm sales. The hedging program for natural gas procurement has no direct impact on PECO’s financial position or results of operations as natural gas costs are fully recovered from customers under the PGC. BGE has contracts to procure SOS electric supply that are executed through a competitive procurement process approved by the MDPSC. The SOS rates charged recover BGE's wholesale power supply costs and include an administrative fee. The administrative fee includes an incremental cost component and a shareholder return component for commercial and industrial rate classes. BGE’s price risk related to electric supply procurement is limited. BGE locks in fixed prices for all of its SOS requirements through full requirements contracts. Certain of BGE’s full requirements contracts, which are considered derivatives, qualify for the NPNS scope exception under current derivative authoritative guidance. Other BGE full requirements contracts are not derivatives. BGE provides natural gas to its customers under a MBR mechanism approved by the MDPSC. Under this mechanism, BGE’s actual cost of gas is compared to a market index (a measure of the market price of gas in a given period). The difference between BGE’s actual cost and the market index is shared equally between shareholders and customers. BGE must also secure fixed price contracts for at least 10% , but not more than 20% , of forecasted system supply requirements for flowing (i.e., non-storage) gas for the November through March period. These fixed-price contracts are not subject to sharing under the MBR mechanism. BGE also ensures it has sufficient pipeline transportation capacity to meet customer requirements. All of BGE’s natural gas supply and asset management agreements qualify for the NPNS scope exception and result in physical delivery. Proprietary Trading. Generation also enters into certain energy-related derivatives for proprietary trading purposes. Proprietary trading includes all contracts entered into with the intent of benefiting from shifts or changes in market prices as opposed to those entered into with the intent of hedging or managing risk. Proprietary trading activities are subject to limits established by Exelon’s RMC. The proprietary trading activities, which included settled physical sales volumes of 1,913 GWhs and 5,378 GWhs for the three and nine months ended September 30, 2015 , respectively, and 3,006 GWhs and 8,129 GWhs for the three and nine months ended September 30, 2014 , respectively, are a complement to Generation’s energy marketing portfolio but represent a small portion of Generation’s revenue from energy marketing activities. ComEd, PECO and BGE do not enter into derivatives for proprietary trading purposes. Interest Rate and Foreign Exchange Risk (Exelon, Generation, ComEd, PECO and BGE) The Registrants use a combination of fixed-rate and variable-rate debt to manage interest rate exposure. The Registrants utilize fixed-to-floating interest rate swaps, which are typically designated as fair value hedges, as a means to manage their interest rate exposure. In addition, the Registrants may utilize interest rate derivatives to lock in rate levels in anticipation of future financings, which are typically designated as cash flow hedges. These strategies are employed to manage interest rate risks. At September 30, 2015 , Exelon had $800 million of notional amounts of fixed-to-floating hedges outstanding and Exelon and Generation had $752 million of notional amounts of floating-to-fixed hedges outstanding. Assuming the fair value and cash flow interest rate hedges are 100% effective, a hypothetical 50 bps increase in the interest rates associated with unhedged variable-rate debt (excluding Commercial Paper) and fixed-to-floating swaps would result in an approximately $3 million decrease in Exelon Consolidated pre-tax income for the nine months ended September 30, 2015 . To manage foreign exchange rate exposure associated with international energy purchases in currencies other than U.S. dollars, Generation utilizes foreign currency derivatives, which are typically designated as economic hedges. Below is a summary of the interest rate and foreign currency hedges as of September 30, 2015 . Generation Other Exelon Description Derivatives Designated as Hedging Instruments Economic Hedges Proprietary Trading (a) Collateral and Netting (b) Subtotal Derivatives Economic Collateral (b) Subtotal Total Mark-to-market derivative assets $ — $ 11 $ 10 $ (12 ) $ 9 $ — $ — $ — $ — $ 9 Mark-to-market derivative assets assets) — 10 7 (2 ) 15 37 — — 37 52 Total mark-to-market derivative — 21 17 (14 ) 24 37 — — 37 61 Mark-to-market derivative liabilities (current liabilities) (9 ) (6 ) (10 ) 16 (9 ) — — — — (9 ) Mark-to-market derivative liabilities (noncurrent liabilities) (12 ) — (5 ) 5 (12 ) — — — — (12 ) Total mark-to-market derivative (21 ) (6 ) (15 ) 21 (21 ) — — — — (21 ) Total mark-to-market derivative (liabilities) $ (21 ) $ 15 $ 2 $ 7 $ 3 $ 37 $ — $ — $ 37 $ 40 _____________ (a) Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts within the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates. (b) Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as accrued interest, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above. The following table provides a summary of the interest rate and foreign exchange hedge balances recorded by the Registrants as of December 31, 2014 : Generation Other Exelon Description Derivatives Designated as Hedging Instruments Economic Hedges Proprietary Trading (a) Collateral and Netting (b) Subtotal Derivatives Designated as Hedging Instruments Economic Collateral (b) Subtotal Total Mark-to-market $ 7 $ 7 $ 20 $ (22 ) $ 12 $ 3 $ — $ — $ 3 $ 15 Mark-to-market 1 5 7 (7 ) 6 20 1 (19 ) 2 8 Total mark-to-market 8 12 27 (29 ) 18 23 1 (19 ) 5 23 Mark-to-market (8 ) (2 ) (14 ) 25 1 — — — — 1 Mark-to-market (4 ) — (9 ) 10 (3 ) (29 ) (101 ) 19 (111 ) (114 ) Total mark-to-market derivative (12 ) (2 ) (23 ) 35 (2 ) (29 ) (101 ) 19 (111 ) (113 ) Total mark-to-market $ (4 ) $ 10 $ 4 $ 6 $ 16 $ (6 ) $ (100 ) $ — $ (106 ) $ (90 ) _______________ (a) Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts within the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates. (b) Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as accrued interest, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above. Fair Value Hedges . For derivative instruments that are designated and qualify as fair value hedges, the gain or loss on the derivative as well as the offsetting loss or gain on the hedged item attributable to the hedged risk are recognized in current earnings. Exelon includes the gain or loss on the hedged items and the offsetting loss or gain on the related interest rate swaps in interest expense as follows: Three Months Ended September 30, Income Statement Location 2015 2014 2015 2014 Gain (Loss) on Swaps Gain (Loss) on Borrowings Generation Interest expense (a) $ — $ (4 ) $ — $ 1 Exelon Interest expense 16 (8 ) 13 (6 ) Nine Months Ended September 30, Income Statement Location 2015 2014 2015 2014 Gain (Loss) on Swaps Gain (Loss) on Borrowings Generation Interest expense (a) $ (1 ) $ (12 ) $ — $ 1 Exelon Interest expense 13 (3 ) 8 6 __________ (a) For the three and nine months ended September 30, 2015 , the loss on Generation swaps included $0 million and $1 million realized in earnings, respectively, with an immaterial amount excluded from hedge effectiveness testing. For the three and nine months ended September 30, 2014 , the loss on Generation swaps included $4 million and $12 million realized in earnings, respectively, with an $2 million amount excluded from hedge effectiveness testing. At September 30, 2015 , Exelon had total outstanding fixed-to-floating fair value hedges related to interest rate swaps of $800 million , with a derivative asset of $37 million . At December 31, 2014 , Exelon and Generation had outstanding fixed-to-floating fair value hedges related to interest rate swaps of $1,450 million and $550 million , with a derivative asset of $29 million and $7 million , respectively. During the three and nine months ended September 30, 2015 , the impact on the results of operations as a result of the ineffectiveness from fair value hedges was a $3 million and $11 million gain, respectively. During the three and nine months ended September 30, 2014 , the impact on the results of operations as a result of the ineffectiveness from fair value hedges was a $6 million and $14 million gain, respectively. Cash Flow Hedges . During 2014, Exelon entered into $400 million of floating-to-fixed forward starting interest rate swaps to manage a portion of the interest rate exposure associated with the anticipated refinancing of existing debt. The swaps are designated as cash flow hedges. In January 2015, in connection with Generation's $750 million issuance of five-year Senior Unsecured Notes, Exelon terminated these swaps. As the original forecasted transactions were a series of future interest payments over a ten year period, a portion of the anticipated interest payments are probable not to occur. As a result, $26 million of anticipated payments were reclassified from Accumulated OCI to Other, net in Exelon's Consolidated Statement of Operations and Comprehensive Income. During the third quarter of 2014, ExGen Texas Power, LLC, a subsidiary of Generation, entered into a floating-to-fixed interest rate swap to manage a portion of its interest rate exposure in connection with a long-term borrowing. See Note 13 — Debt and Credit Agreements of the Exelon 2014 Form 10-K for additional information regarding the financing. The swaps have a notional amount of $501 million as of September 30, 2015 and expire in 2019. The swap was designated as a cash flow hedge in the fourth quarter of 2014. At September 30, 2015 , the subsidiary had a $16 million derivative liability related to the swap. During the first quarter of 2014, ExGen Renewables I, LLC, a subsidiary of Exelon Generation, entered into floating-to-fixed interest rate swaps to manage a portion its interest rate exposure in connection with long-term borrowings. See Note 13 — Debt and Credit Agreements of the Exelon 2014 Form 10-K for additional information regarding the financing. The swaps have a notional amount of $200 million as of September 30, 2015 and expire in 2020. The swaps are designated as cash flow hedges. At September 30, 2015 , the subsidiary had a $ 4 million derivative liability related to the swaps. During the three and nine months ended September 30, 2015 and 2014 , the impact on the results of operations as a result of ineffectiveness from cash flow hedges in continuing designated hedge relationships were immaterial. Economic Hedges . During the third quarter of 2011, Sacramento PV Energy, a subsidiary of Generation entered into floating-to-fixed interest rate swaps to manage a portion of its interest rate exposure in connection with the long-term borrowings. See Note 13 — Debt and Credit Agreements of the Exelon 2014 Form 10-K for additional information regarding the financing. The swaps have a total notional amount of $26 million as of September 30, 2015 and expire in 2027. After the closing of the Constellation merger, the swaps were re-designated as cash flow hedges. During the first quarter of 2015, the swaps were de-designated as the forecasted transaction was no longer probable of occurring. All future changes in fair value are reflected in Interest expense. At September 30, 2015 , the subsidiary had a $3 million derivative liability related to these swaps, which included an immaterial amount that was amortized to Interest expense after de-designation. During the third quarter of 2012, Constellation Solar Horizon, a subsidiary of Exelon Generation, entered into a floating-to-fixed interest rate swap to manage a portion of its interest rate exposure in connection with the long-term borrowings. See Note 13 — Debt and Credit Agreements of the Exelon 2014 Form 10-K for additional information regarding the financing. The swap has a notional amount of $25 million as of September 30, 2015 and expires in 2030. This swap was designated as a cash flow hedge. During the first quarter of 2015, the swaps were de-designated as the forecasted transaction was no longer probable of occurring. All future changes in fair value are reflected in Interest expense. At September 30, 2015 , the subsidiary had an immaterial derivative liability related to the swap. During the second quarter 2015, upon the issuance of debt, Exelon terminated $ 2,400 million of floating-to-fixed forward starting interest rate swaps. As a result of the termination of the swaps, Exelon realized a $64 million loss during the second quarter of 2015. At September 30, 2015 , Generation had immaterial notional amounts of interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions and $ 99 million in notional amounts of foreign currency exchange rate swaps that are marked-to-market to manage the exposure associated with international purchases of commodities in currencies other than U.S. dollars. Fair Value Measurement and Accounting for the Offsetting of Amounts Related to Certain Contracts (Exelon, Generation, ComEd, PECO and BGE) Fair value accounting guidance and disclosures about offsetting assets and liabilities requires the fair value of derivative instruments to be shown in the Notes to the Consolidated Financial Statements on a gross basis, even when the derivative instruments are subject to legally enforceable master netting agreements and qualify for net presentation in the Consolidated Balance Sheet. A master netting agreement is an agreement between two counterparties that may have derivative and non-derivative contracts with each other providing for the net settlement of all referencing contracts via one payment stream, which takes place as the contracts deliver, when collateral is requested or in the event of default. Generation’s use of cash collateral is generally unrestricted, unless Generation is downgraded below investment grade (i.e., to BB+ or Ba1). In the table below, Generation’s energy related economic hedges and proprietary trading derivatives are shown gross. The impact of the netting of fair value balances with the same counterparty that are subject to legally enforceable master netting agreements, as well as netting of cash collateral, including initial margin on exchange positions, is aggregated in the collateral and netting column. As of September 30, 2015 and December 31, 2014 , $4 million and $8 million of cash collateral posted, respectively, was not offset against derivative positions because such collateral was not associated with any energy-related derivatives, were associated with accrual positions, or as of the balance sheet date there were no positions to offset. Excluded from the tables below are economic hedges that qualify for the NPNS scope exception and other non-derivative contracts that are accounted for under the accrual method of accounting. ComEd’s use of cash collateral is generally unrestricted, unless ComEd is downgraded below investment grade (i.e., to BB+ or Ba1). Cash collateral held by PECO and BGE must be deposited in a non-affiliate major U.S. commercial bank or foreign bank with a U.S. branch office that meet certain qualifications. The following table provides a summary of the derivative fair value balances recorded by the Registrants as of September 30, 2015 : Generation ComEd Exelon Derivatives Economic Hedges Proprietary Trading Collateral and Netting (a) Subtotal (b) Economic Hedges (c) Total Derivatives Mark-to-market derivative assets (current assets) $ 3,958 $ 221 $ (3,072 ) $ 1,107 $ — $ 1,107 Mark-to-market derivative assets (noncurrent assets) 2,372 42 (1,665 ) 749 — 749 Total mark-to-market derivative assets 6,330 263 (4,737 ) 1,856 — 1,856 Mark-to-market derivative liabilities (current liabilities) (3,719 ) (213 ) 3,759 (173 ) (22 ) (195 ) Mark-to-market derivative liabilities (noncurrent liabilities) (2,088 ) (50 ) 2,011 (127 ) (221 ) (348 ) Total mark-to-market derivative liabilities (5,807 ) (263 ) 5,770 (300 ) (243 ) (543 ) Total mark-to-market derivative net assets (liabilities) $ 523 $ — $ 1,033 $ 1,556 $ (243 ) $ 1,313 _________ (a) Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as trade receivables and payables, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above. (b) Current and noncurrent assets are shown net of collateral of $281 million and $150 million , respectively, and current and noncurrent liabilities are shown net of collateral of $405 million and $197 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $1,033 million at September 30, 2015 . (c) Includes current and noncurrent liabilities relating to floating-to-fixed energy swap contracts with unaffiliated suppliers. The following table provides a summary of the derivative fair value balances recorded by the Registrants as of December 31, 2014 : Generation ComEd Exelon Description Economic Hedges Proprietary Trading Collateral and Netting (a) Subtotal (b) Economic Hedges (c) Total Derivatives Mark-to-market derivative assets (current assets) $ 4,992 $ 456 $ (4,184 ) $ 1,264 $ — $ 1,264 Mark-to-market derivative assets (noncurrent assets) 1,821 56 (1,112 ) 765 — 765 Total mark-to-market derivative assets 6,813 512 (5,296 ) 2,029 — 2,029 Mark-to-market derivative liabilities (current liabilities) (4,947 ) (468 ) 5,200 (215 ) (20 ) (235 ) Mark-to-market derivative liabilities (noncurrent liabilities) (1,540 ) (64 ) 1,502 (102 ) (187 ) (289 ) Total mark-to-market derivative liabilities (6,487 ) (532 ) 6,702 (317 ) (207 ) (524 ) Total mark-to-market derivative net assets (liabilities) $ 326 $ (20 ) $ 1,406 $ 1,712 $ (207 ) $ 1,505 ________ (a) Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as trade receivables and payables, transactions that do not qualify as derivatives, and letters of credit. These are not reflected in the table above. (b) Current and noncurrent assets are shown net of collateral of $416 million and $171 million , respectively, and current and noncurrent liabilities are shown net of collateral of $599 million and $220 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $1,406 million at December 31, 2014 . (c) Includes current and noncurrent liabilities relating to floating-to-fixed energy swap contracts with unaffiliated suppliers. Cash Flow Hedges (Exelon, Generation and ComEd). As discussed previously, effective prior to the Constellation merger, Generation de-designated all of its cash flow hedges relating to commodity price risk. Because the underlying forecasted transactions remain at least reasonably probable, the fair value of the effective portion of these cash flow hedges was frozen in Accumulated OCI and is reclassified to results of operations when the forecasted purchase or sale of the energy commodity occurs, or becomes probable of not occurring. Generation began recording prospective changes in the fair value of these instruments through current earnings from the date of de-designation. As of September 30, 2015 , no unrealized balance remains in accumulated OCI to be reclassified by Generation. The tables below provide the activity of accumulated OCI related to cash flow hedges for the three and nine months ended September 30, 2015 and 2014 , containing information about the changes in the fair value of cash flow hedges and the reclassification from accumulated OCI into results of operations. The amounts reclassified from accumulated OCI, when combined with the impacts of the hedged transactions, result in the ultimate recognition of net revenues or expenses at the contractual price. Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Three Months Ended September 30, 2015 Income Statement Location Total Cash Flow Hedges Total Cash Flow Hedges Accumulated OCI derivative gain at June 30, 2015 $ (21 ) $ (19 ) Effective portion of changes in fair value (7 ) (8 ) Reclassifications from accumulated OCI to net income Interest Expense 3 3 Accumulated OCI derivative gain at September 30, 2015 $ (25 ) $ (24 ) Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Nine Months Ended Sept

Debt and Credit Agreements (Exe

Debt and Credit Agreements (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Debt and Credit Agreements (Exelon, Generation, ComEd, PECO and BGE)	Debt and Credit Agreements (Exelon, Generation, ComEd, PECO and BGE) Short-Term Borrowings Exelon, ComEd and BGE meet their short-term liquidity requirements primarily through the issuance of commercial paper. Generation and PECO meet their short-term liquidity requirements primarily through the issuance of commercial paper and borrowings from the intercompany money pool. The Registrants had the following amounts of commercial paper borrowings outstanding as of September 30, 2015 and December 31, 2014 : Commercial Paper Borrowings September 30, 2015 December 31, 2014 Exelon Corporate $ — $ — Generation — — ComEd 604 304 PECO — — BGE 50 120 Credit Facilities Exelon had bank lines of credit under committed credit facilities at September 30, 2015 for short-term financial needs, as follows: Type of Credit Facility Amount (a) Expiration Dates Capacity Type (In billions) Exelon Corporate Syndicated Revolver (b) $ 0.5 May 2019 Letters of credit and cash Generation Syndicated Revolver 5.1 May 2019 Letters of credit and cash Syndicated Revolver 0.2 August 2018 Letters of credit and cash Bilateral 0.3 December 2015 and March 2016 Letters of credit and cash Bilateral 0.1 January 2017 Letters of credit Bilateral 0.1 October 2015 Letters of credit and cash ComEd Syndicated Revolver 1.0 March 2019 Letters of credit and cash PECO Syndicated Revolver (b) 0.6 May 2019 Letters of credit and cash BGE Syndicated Revolver (b) 0.6 May 2019 Letters of credit and cash Total $ 8.5 (a) Excludes additional credit facility agreements for Generation, ComEd, PECO and BGE with aggregate commitments of $50 million , $34 million , $34 million and $5 million , respectively, arranged with minority and community banks located primarily within ComEd’s, PECO’s and BGE’s service territories. These facilities expire d on October 16, 2015 and were renewed at the same amount through October 14, 2016. These facilities are solely utilized to issue letters of credit. As of September 30, 2015 , letters of credit issued under these agreements for Generation, ComEd, PECO and BGE totaled $7 million , $16 million , $21 million and $1 million , respectively. (b) Syndicated revolvers include credit facility commitments of $22 million , $27 million and $27 million for Exelon Corporate, PECO and BGE, respectively, which expire in August 2018. As of September 30, 2015 , there were no borrowings under the Registrants’ credit facilities. On October 23, 2015, a $100 million bilateral CENG credit facility was amended and extended for an additional two years. This facility has been utilized by CENG to fund working capital and capital projects. This facility does not back Generation's commercial paper program. Borrowings under Exelon Corporate’s, Generation’s, ComEd’s, PECO’s and BGE’s credit agreements bear interest at a rate based upon either the prime rate or a LIBOR-based rate, plus an adder based upon the particular Registrant’s credit rating. Exelon Corporate, Generation, ComEd, PECO and BGE have adders of 27.5 , 27.5 , 7.5 , 0.0 and 0.0 basis points for prime based borrowings and 127.5 , 127.5 , 107.5 , 90.0 and 100.0 basis points for LIBOR-based borrowings. The maximum adders for prime rate borrowings and LIBOR-based rate borrowings are 65 basis points and 165 basis points, respectively. The credit agreements also require the borrower to pay a facility fee based upon the aggregate commitments under the agreement. The fee varies depending upon the respective credit ratings of the borrower. Long-Term Debt Issuance of Long-Term Debt During the nine months ended September 30, 2015 , the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Exelon Corporate Senior Unsecured Notes (a) 1.55 % June 9, 2017 $ 550 Finance a portion of the pending acquisition of PHI and related costs and expenses, and for general corporate purposes Exelon Corporate Senior Unsecured Notes (a) 2.85 % June 15, 2020 $ 900 Finance a portion of the pending acquisition of PHI and related costs and expenses, and for general corporate purposes Exelon Corporate Senior Unsecured Notes (a) 3.95 % June 15, 2025 $ 1,250 Finance a portion of the pending acquisition of PHI and related costs and expenses, and for general corporate purposes Exelon Corporate Senior Unsecured Notes (a) 4.95 % June 15, 2035 $ 500 Finance a portion of the pending acquisition of PHI and related costs and expenses, and for general corporate purposes Exelon Corporate Senior Unsecured Notes (a) 5.10 % June 15, 2045 $ 1,000 Finance a portion of the pending acquisition of PHI and related costs and expenses, and for general corporate purposes Exelon Corporate Long Term Software License Agreement 3.95 % May 1, 2024 $ 111 Procurement of software licenses Generation Senior Unsecured Notes (b) 2.95 % January 15, 2020 $ 750 Fund the optional redemption of Exelon's $550 million, 4.550% Senior Notes and for general corporate purposes Generation AVSR DOE Nonrecourse Debt 2.29 - 2.96% January 5, 2037 $ 39 Antelope Valley solar development Generation Energy Efficiency Project Financing 3.71 % October 1, 2035 $ 42 Funding to install energy conservation measures in Coleman, Florida Generation Energy Efficiency Project Financing 3.55 % November 15, 2016 $ 19 Funding to install energy conservation measures in Frederick, Maryland Generation Tax Exempt Pollution Control Revenue Bonds (c) 2.50 - 2.70% 2019 - 2020 $ 435 General corporate purposes Generation Albany Green Energy Project Financing LIBOR + 1.25% November 17, 2017 $ 74 Albany Green Energy biomass generation development ComEd Mortgage Bonds Series 118 3.70 % March 1, 2045 $ 400 Refinance maturing mortgage bonds, repay a portion of ComEd's outstanding commercial paper obligations and for general corporate purposes _____________ (a) In connection with the issuance of PHI acquisition financing, Exelon terminated its interest rate swaps that had been designated as cash flow hedges. See Note 10 — Derivative Financial Instruments for further information. (b) In connection with the issuance of Senior Unsecured Notes, Exelon terminated floating-to-fixed interest rate swaps that had been designated as cash flow hedges. See Note 10 — Derivative Financial Instruments for further information on the swap termination. (c) The Tax Exempt Pollution Control Revenue Bonds have a mandatory put date that ranges from March 1, 2019 - September 1, 2020. On October 5, 2015, PECO issued $350 million aggregate principal amount of its First and Refunding Mortgage Bonds, 3.15% Series, maturing on October 15, 2025. The proceeds will be used for general corporate purposes. Merger Financing In May 2014, concurrently and in connection with entering into the agreement to acquire PHI, Exelon entered into a credit facility to which the lenders committed to provide Exelon a 364-day senior unsecured bridge credit facility of $7.2 billion to support the contemplated transaction and provide flexibility for timing of permanent financing. In June 2015, the remaining $3.2 billion bridge credit facility was terminated as a result of Exelon's issuance of $4.2 billion of long-term debt to fund a portion of the purchase price and related costs and expenses of the merger between Exelon and PHI and for general corporate purposes. In connection with the $4.2 billion issuance of Senior Unsecured Notes in 2015, the tranches due in 2025, 2035 and 2045 must be redeemed at the principal amount plus a 1% premium of principal upon the earlier of (1) December 31, 2015, if the PHI acquisition is not consummated on or prior to such date, or (2) the date on which the Merger Agreement relating to the PHI acquisition is terminated. Exelon also has the option to redeem those notes earlier at a 1% premium of principal, if Exelon determines that the merger will not be completed before December 31, 2015. On October 29, 2015, Exelon commenced a private exchange offer (Exchange Offer) to certain eligible holders whereby, for those that take part, the outstanding notes in the 2025, 2035 and 2045 tranches will be exchanged for new notes. The new notes will have substantially the same terms as the outstanding notes, except the outside date with regard to the special redemption provisions is June 30, 2016, rather than December 31, 2015, and under certain circumstances, can be further extended to August 31, 2016. The Exchange Offer's early participation period terminates on November 13, 2015 and its expiration date is November 30, 2015, unless extended. Following the completion of the Exchange Offer, any remaining notes not exchanged are expected to be redeemed pursuant to the terms of such remaining notes. Upon redemption, Exelon will accelerate amortization of previously capitalized debt issuance costs on such notes. As of September 30, 2015 , the total unamortized debt issuance costs for the 2025, 2035 and 2045 notes is $22 million . Albany Green Energy Project Financing (AGE) Generation owns 90% of Albany Green Energy, LLC (AGE), which is a consolidated variable interest entity (see Note 3 - Variable Interest Entities for additional information). In the second quarter of 2015, AGE closed the construction financing and executed an Engineering, Procurement and Construction (EPC) contract to construct a biomass-fueled, combined heat and power facility in Albany, GA. The financing will accumulate and accrue interest throughout construction and is due upon substantial completion of the facility, but no later than November 17, 2017. During the nine months ended September 30, 2014 , the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Exelon Junior Subordinated Notes 2.50 % June 1, 2024 $ 1,150 Finance a portion of the acquisition of PHI and for general corporate purposes Generation Nuclear Fuel Purchase Contract 3.25 - 3.35% June 30, 2018 $ 70 Procurement of uranium Generation ExGen Renewables I Nonrecourse Debt LIBOR + 4.25% February 6, 2021 $ 300 General corporate purposes Generation ExGen Texas Power Nonrecourse Debt LIBOR + 4.75% September 18, 2021 $ 675 General corporate purposes Generation Energy Efficiency Project Financing 4.12 % December 31, 2015 $ 12 Funding to install energy conservation measures in Washington, DC Generation AVSR DOE Nonrecourse Debt 3.06 - 3.14% January 5, 2037 $ 125 Antelope Valley solar development ComEd First Mortgage Bonds Series 115 2.15 % January 15, 2019 $ 300 Refinance maturing mortgage bonds and general corporate purposes ComEd First Mortgage Bonds Series 116 4.70 % January 15, 2044 $ 350 Refinance maturing mortgage bonds and general corporate purposes PECO First and Refunding Mortgage Bonds 4.15 % October 1, 2044 $ 300 Refinance existing mortgage bonds and general corporate purposes Retirement and Redemptions of Current and Long-Term Debt During the nine months ended September 30, 2015 , the following long-term debt was retired and/or redeemed: Company Type Interest Rate Maturity Amount Exelon Corporate (a) Senior Unsecured Notes 4.55 % June 15, 2015 $ 550 Exelon Corporate Senior Notes 4.90 % June 15, 2015 $ 800 Exelon Corporate Long Term Software License Agreement 3.95 % May 1, 2024 $ 1 Generation (a) Senior Unsecured Notes 4.55 % June 15, 2015 $ 550 Generation CEU Upstream Nonrecourse Debt LIBOR + 2.25% January 14, 2019 $ 9 Generation AVSR DOE Nonrecourse Debt 2.29%-3.56% January 5, 2037 $ 12 Generation Kennett Square Capital Lease 7.83 % September 20, 2020 $ 3 Generation Continental Wind Nonrecourse Debt 6.00 % February 28, 2033 $ 20 Generation ExGen Texas Power Nonrecourse Debt LIBOR + 4.75% September 8, 2021 $ 5 Generation ExGen Renewables I Nonrecourse Debt LIBOR + 4.25% February 6, 2021 $ 14 Generation Constellation Solar Horizons Nonrecourse Debt 2.56 % September 7, 2030 $ 1 Generation Sacramento PV Energy Nonrecourse Debt 2.58 % December 31, 2030 $ 1 ComEd FMB Series 101 4.70 % April 15, 2015 $ 260 BGE Rate Stabilization Bonds 5.72 % April 1, 2016 $ 37 ____________ (a) As part of the 2012 Constellation merger, Exelon and subsidiaries of Generation assumed intercompany loan agreements that mirrored the terms and amounts of external obligations held by Exelon, resulting in intercompany notes payable at Generation and Exelon Corporate. On October 5, 2015, Generation paid down $10 million of principal of its 2.29-3.56% AVSR DOE Nonrecourse debt. On October 15, 2015, Generation paid down $10 million of principal of its LIBOR + 4.25% ExGen Renewables I Nonrecourse debt. During the nine months ended September 30, 2014 , the following long-term debt was retired and/or redeemed: Company Type Interest Rate Maturity Amount Generation Senior Unsecured Notes 5.35 % January 15, 2014 $ 500 Generation Pollution Control Notes 4.10 % July 1, 2014 $ 20 Generation Continental Wind Nonrecourse Debt 6.00 % February 28, 2033 $ 20 Generation Kennett Square Capital Lease 7.83 % September 20, 2020 $ 2 Generation ExGen Renewables I Nonrecourse Debt 3mL + 4.25% February 6, 2021 $ 3 Generation AVSR DOE Nonrecourse Debt 2.33% - 3.55% January 5, 2037 $ 4 Generation Clean Horizons Solar Nonrecourse Debt 2.56 % September 7, 2030 $ 1 Generation Sacramento Solar Nonrecourse Debt 2.56 % December 31, 2030 $ 1 Generation Energy Efficiency Project Financing 4.40 % August 31, 2014 $ 9 ComEd Mortgage Bonds Series 110 1.63 % January 15, 2014 $ 600 ComEd Pollution Control Series 1994C 5.85 % January 15, 2014 $ 17 BGE Rate Stabilization Bonds 5.72 % April 1, 2016 $ 35 Junior Subordinated Notes In June 2014, Exelon issued $1.15 billion of junior subordinated notes in the form of 23 million equity units at a stated amount of $50.00 per unit. Net proceeds from the issuance were $1.11 billion , net of a $ 35 million underwriter fee. The net proceeds are being used to finance a portion of the acquisition and related costs and expenses for PHI and for general corporate purposes. Each equity unit represents an undivided beneficial ownership interest in Exelon’s 2.50% junior subordinated notes due in 2024 and a forward equity purchase contract which settles in 2017. The junior subordinated notes are expected to be remarketed in 2017. At the time of issuance, Exelon determined that the forward equity purchase contract had no value and therefore the entire $1.15 billion of junior subordinated notes were allocated to debt and recorded within Long-term debt on Exelon’s Consolidated Balance Sheet. Additionally, at the time of issuance, the present value of the contract payments of $131 million ("Contract Payment Obligation") were recorded to Long-term debt, representing the obligation to make contract payments, with an offsetting reduction to Common stock. The obligation for the contract payments will be accreted to interest expense over the 3 year period ending in 2017 in Exelon’s Consolidated Statement of Operations and Comprehensive Income. During 2015, contract payments of $33 million related to the Contract Payment Obligation were included within Retirements of long-term debt in Exelon's Consolidated Statements of Cash Flows. During 2014, the Contract Payment Obligation was considered a non-cash financing transaction that was excluded from Exelon’s Consolidated Statements of Cash Flows. Until settlement of the equity purchase contract, earnings per share dilution resulting from the equity unit issuance will be determined under the treasury stock method. For further information about the terms of the remarketing of the junior subordinated notes, see Note 13 — Debt and Credit Agreements and Note 23 - Supplemental Financial Information of the Exelon 2014 Form 10-K.

Income Taxes (Exelon, Generatio

Income Taxes (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes (Exelon, Generation, ComEd, PECO and BGE)	Income Taxes (Exelon, Generation, ComEd, PECO and BGE) The effective income tax rate from continuing operations varies from the U.S. Federal statutory rate principally due to the following: For the Three Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit 2.7 2.1 5.0 1.2 5.3 Qualified nuclear decommissioning trust fund income (5.4 ) (12.5 ) — — — Domestic production activities deduction (4.9 ) (11.6 ) — — — Health care reform legislation — — — — 0.2 Amortization of investment tax credit, net deferred taxes (2.3 ) (5.2 ) (0.3 ) (0.1 ) (0.2 ) Plant basis differences (1.4 ) — (0.1 ) (7.0 ) (0.6 ) Production tax credits and other credits (3.8 ) (9.0 ) — — — Noncontrolling interest 1.7 3.9 — — — Statute of limitations expiration (6.4 ) (15.2 ) — — — Other 1.2 0.4 0.3 — (0.4 ) Effective income tax rate 16.4 % (12.1 )% 39.9 % 29.1 % 39.3 % For the Nine Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit 3.1 2.8 5.2 1.2 5.3 Qualified nuclear decommissioning trust fund income (0.9 ) (1.6 ) — — — Domestic production activities deduction (2.8 ) (4.9 ) — — — Health care reform legislation — — — — 0.2 Amortization of investment tax credit, net deferred taxes (1.2 ) (1.9 ) (0.3 ) (0.1 ) (0.1 ) Plant basis differences (1.2 ) — (0.1 ) (7.3 ) (0.4 ) Production tax credits and other credits (2.2 ) (3.8 ) — — — Noncontrolling interest — 0.1 — — — Statute of limitations expiration (1.6 ) (2.9 ) — — — Other 0.9 0.6 0.2 0.2 (0.1 ) Effective income tax rate 29.1 % 23.4 % 40.0 % 29.0 % 39.9 % For the Three Months Ended September 30, 2014 Exelon Generation ComEd PECO BGE U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit 3.4 3.7 5.0 0.1 4.6 Qualified nuclear decommissioning trust fund income (0.3 ) (0.4 ) — — — Domestic production activities deduction (2.4 ) (3.2 ) — — — Health care reform legislation — — 0.2 — 0.2 Amortization of investment tax credit, net deferred taxes (1.0 ) (1.2 ) (0.3 ) (0.1 ) (0.3 ) Plant basis differences (0.8 ) — — (11.3 ) 0.5 Production tax credits and other credits (1.9 ) (2.4 ) — — — Noncontrolling interest (1.2 ) (1.6 ) — — — Statute of limitations expiration (3.8 ) (5.0 ) — — — Other 1.2 0.6 0.1 (0.1 ) (1.2 ) Effective income tax rate 28.2 % 25.5 % 40.0 % 23.6 % 38.8 % For the Nine Months Ended September 30, 2014 Exelon Generation ComEd PECO BGE U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit 2.0 1.2 5.0 0.3 4.9 Qualified nuclear decommissioning trust fund income 2.0 3.6 — — — Domestic production activities deduction (2.7 ) (4.8 ) — — — Health care reform legislation 0.1 — 0.2 — 0.2 Amortization of investment tax credit, net deferred taxes (1.1 ) (1.7 ) (0.3 ) (0.1 ) (0.3 ) Plant basis differences (1.6 ) — (0.3 ) (11.0 ) 0.5 Production tax credits and other credits (2.1 ) (3.7 ) — — — Noncontrolling interest (1.4 ) (2.6 ) — — — Statute of limitations expiration (2.5 ) (4.4 ) — — — Other (0.5 ) (0.7 ) 0.1 0.1 (0.5 ) Effective income tax rate 27.2 % 21.9 % 39.7 % 24.3 % 39.8 % Accounting for Uncertainty in Income Taxes Exelon, Generation, ComEd, PECO, and BGE have $1,204 million , $660 million , $144 million , $0 million , and $120 million , of unrecognized tax benefits as of September 30, 2015 , respectively, and $1,829 million , $1,357 million , $149 million , $44 million , and $0 million , of unrecognized tax benefits as of December 31, 2014 , respectively. The unrecognized tax benefits as of September 30, 2015 reflect a decrease at Exelon, Generation, and PECO primarily attributable to the disallowed AmerGen claims discussed below and the resolution of state income tax positions at Generation. The unrecognized tax benefits as of September 30, 2015 reflect an increase at BGE and Generation attributable to a state income tax opportunity. A portion of the benefits associated with uncertain tax positions for utilities, if recognized, may be included in future base rates. Nuclear Decommissioning Liabilities AmerGen filed income tax refund claims taking the position that nuclear decommissioning liabilities assumed as part of its acquisition of nuclear power plants are taken into account in determining the tax basis in the assets it acquired. The additional basis results primarily in reduced capital gains or increased capital losses on the sale of assets in nonqualified decommissioning funds and increased tax depreciation and amortization deductions. The IRS disagrees with this position and disallowed AmerGen's claims. In early 2009, Generation filed a complaint in the United States Court of Federal Claims to contest this determination. On September 17, 2013, the Court granted the government’s motion denying AmerGen’s claims for refund. In the first quarter of 2014, Exelon filed an appeal of the decision to the United States Court of Appeals for the Federal Circuit. On March 11, 2015, the Federal Circuit affirmed the lower court’s decision to deny AmerGen’s claims for refund. Exelon will not be pursuing further appeals with respect to this issue and, as a result, reduced Generation and PECO's unrecognized tax benefits by $ 661 million and $43 million , respectively, in the first quarter of 2015. This change in unrecognized tax benefits had no impact on Exelon, Generation, or PECO's effective tax rate. Reasonably possible the total amount of unrecognized tax benefits could significantly increase or decrease within 12 months after the reporting date Like-Kind Exchange As of September 30, 2015 , Exelon and ComEd have approximately $ 394 million and $ 144 million of unrecognized tax benefits that could significantly decrease within the 12 months after the reporting date as a result of a decision in the like-kind exchange litigation described below. Exelon and ComEd have unrecognized tax benefits that, if recognized, would decrease Exelon's effective tax rate by $ 71 million and increase ComEd's effective tax rate by $ 11 million . Settlement of Income Tax Audits As of September 30, 2015 , Exelon, Generation, and BGE have approximately $261 million , $ 141 million , and $ 120 million of unrecognized state tax benefits that could significantly decrease within the 12 months after the reporting date as a result of completing audits, potential settlements, and expected statute of limitation expirations. Of the above unrecognized tax benefits, Exelon and Generation have $ 141 million that, if recognized, would decrease the effective tax rate. The unrecognized tax benefit related to BGE, if recognized, may be included in future base rates and that portion would have no impact to the effective tax rate. Other Income Tax Matters Like-Kind Exchange Exelon, through its ComEd subsidiary, took a position on its 1999 income tax return to defer approximately $1.2 billion of tax gain on the sale of ComEd’s fossil generating assets. The gain was deferred by reinvesting a portion of the proceeds from the sale in qualifying replacement property under the like-kind exchange provisions of the IRC. The like-kind exchange replacement property purchased by Exelon included interests in three municipal-owned electric generation facilities which were properly leased back to the municipalities. The IRS disagreed with this position and asserted that the entire gain of approximately $1.2 billion was taxable in 1999. Exelon has been unable to reach agreement with the IRS regarding the dispute over the like-kind exchange position. The IRS has asserted that the Exelon purchase and leaseback transaction is substantially similar to a leasing transaction, known as a SILO, which the IRS does not respect as the acquisition of an ownership interest in property. A SILO is a “listed transaction” that the IRS has identified as a potentially abusive tax shelter under guidance issued in 2005. Accordingly, the IRS has asserted that the sale of the fossil plants followed by the purchase and leaseback of the municipal owned generation facilities does not qualify as a like-kind exchange and the gain on the sale is fully subject to tax. The IRS has also asserted a penalty of approximately $90 million for a substantial understatement of tax. Exelon disagrees with the IRS and continues to believe that its like-kind exchange transaction is not the same as or substantially similar to a SILO. Although Exelon has been and remains willing to settle the disagreement on terms commensurate with the hazards of litigation, Exelon does not believe a settlement is possible. Because Exelon believed, as of December 31, 2012, that it was more-likely-than-not that Exelon would prevail in litigation, Exelon and ComEd had no liability for unrecognized tax benefits with respect to the like-kind exchange position. On January 9, 2013, the U.S. Court of Appeals for the Federal Circuit reversed the U.S. Court of Federal Claims and reached a decision for the government in Consolidated Edison v. United States. The Court disallowed Consolidated Edison’s deductions stemming from its participation in a LILO transaction that the IRS also has characterized as a tax shelter. In accordance with applicable accounting standards, Exelon is required to assess whether it is more-likely-than-not that it will prevail in litigation. Exelon continues to believe that its transaction is not a SILO and that it has a strong case on the merits. However, in light of the Consolidated Edison decision and Exelon’s current determination that settlement is unlikely, Exelon has concluded that subsequent to December 31, 2012, it is no longer more-likely-than-not that its position will be sustained. As a result, in the first quarter of 2013 Exelon recorded a non-cash charge to earnings of approximately $265 million , which represents the amount of interest expense (after-tax) and incremental state income tax expense for periods through March 31, 2013 that would be payable in the event that Exelon is unsuccessful in litigation. Of this amount, approximately $170 million was recorded at ComEd. Exelon intends to hold ComEd harmless from any unfavorable impacts of the after-tax interest amounts on ComEd’s equity. As such, ComEd recorded on its consolidated balance sheet as of March 31, 2013, a $172 million receivable and non-cash equity contributions from Exelon. Exelon and ComEd will continue to accrue interest on the unpaid tax liabilities related to the uncertain tax position, and the charges arising from future interest accruals are not expected to be material to the annual operating earnings of Exelon or ComEd. In addition, ComEd will continue to record non-cash equity contributions from Exelon in the amount of the net after-tax interest charges attributable to ComEd in connection with the like-kind exchange position. Exelon continues to believe that it is unlikely that the IRS's assertion of penalties will ultimately be sustained and therefore no liability for the penalty has been recorded. On September 30, 2013, the IRS issued a notice of deficiency to Exelon for the like-kind exchange position. Exelon filed a petition on December 13, 2013 to initiate litigation in the United States Tax Court and the trial took place in August of 2015. Exelon was not required to remit any part of the asserted tax or penalty in order to litigate the issue. While the Tax Court could reach its decision as early as 2016, the litigation could take three to five years if appeals are necessary. Decisions in the Tax Court are not controlled by the Federal Circuit’s decision in Consolidated Edison. In the first quarter of 2014, Exelon entered into an agreement to terminate its investment in one of the three municipal-owned electric generation properties in exchange for a net early termination amount of $335 million . In connection with the termination, Exelon will deposit $ 260 million with the IRS for its 2014 tax year, including $135 million by ComEd representing the remaining gain deferred pursuant to the like-kind exchange transaction. The deposit can be redesignated to any tax year, if necessary, and may be used to satisfy any amounts owed as a result of the litigation. In the event of a fully successful IRS challenge to Exelon’s like-kind exchange position, the potential tax and after-tax interest, net of the deposit discussed above and exclusive of penalties, that could become currently payable as of September 30, 2015 may be as much as $560 million , of which approximately $165 million would be attributable to ComEd after consideration of Exelon’s agreement to hold ComEd harmless. Interest will continue to accrue until such time as payment is made. An appeal of an adverse decision in the Tax Court would necessitate either the posting of a bond or the payment of the tax and interest for the tax years before the court. A final appellate decision could take several years.

Nuclear Decommissioning (Exelon

Nuclear Decommissioning (Exelon and Generation)	9 Months Ended
	Sep. 30, 2015
Environmental Remediation Obligations [Abstract]
Nuclear Decommissioning (Exelon and Generation)	Nuclear Decommissioning (Exelon and Generation) Nuclear Decommissioning Asset Retirement Obligations Generation has a legal obligation to decommission its nuclear power plants following the expiration of their operating licenses. To estimate its decommissioning obligation related to its nuclear generating stations for financial accounting and reporting purposes, Generation uses a probability-weighted, discounted cash flow model which, on a unit-by-unit basis, considers multiple outcome scenarios that include significant estimates and assumptions, and are based on decommissioning cost studies, cost escalation rates, probabilistic cash flow models and discount rates. Generation generally updates its ARO annually during the third quarter, unless circumstances warrant more frequent updates, based on its review of updated cost studies and its annual evaluation of cost escalation factors and probabilities assigned to various scenarios. The following table provides a rollforward of the nuclear decommissioning ARO reflected on Exelon’s and Generation’s Consolidated Balance Sheets from December 31, 2014 to September 30, 2015 : Nuclear decommissioning ARO at December 31, 2014 (a) $ 6,961 Net increase due to changes in, and timing of, estimated future cash flows 831 Accretion expense 283 Costs incurred to decommission retired plants (2 ) Nuclear decommissioning ARO at September 30, 2015 (a) $ 8,073 ___________ (a) Includes $7 million and $8 million as the current portion of the ARO at September 30, 2015 and December 31, 2014 respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets. During the nine months ended September 30, 2015, Generation’s total nuclear ARO increased by approximately $1.1 billion , reflecting impacts of ARO updates completed during the first and third quarters of 2015 to reflect changes in amounts and timing of estimated decommissioning cash flows and impacts of year-to-date accretion of the ARO liability due to the passage of time. In the first quarter of 2015, the ARO liability was increased by $55 million to reflect a purchase accounting adjustment to the fair value of the CENG ARO liability as of April 1, 2014, the date of the consolidation of CENG. See Note 6 - Investment in Constellation Energy Nuclear Group, LLC for additional information. The third quarter 2015 annual update further increased the ARO liability by a net $775 million , which was primarily driven by an increase of approximately $550 million for costs expected to be incurred for required site security during the decommissioning periods in which SNF remains onsite and until major reactor components and buildings have been dismantled and removed. This projected increase is based on emerging industry experience at nuclear sites in the planning or early stage of decommissioning indicating greater than originally expected numbers of security personnel required to be on site during these decommissioning periods. Generation will continue to monitor emerging security cost trends, including potential strategies to limit such costs by, for example, optimizing the transfer of SNF when DOE starts taking possession of SNF or increasing the use of dry SNF storage, and will adjust the ARO liability accordingly. The third quarter 2015 adjustment to the ARO includes an increase of $285 million for the impacts of a change implemented in the 2015 annual assessment of Generation’s SNF storage and disposal cost estimation methodology to better align the projected timing of SNF transfers to the DOE with assumed plant shutdown dates. The third quarter 2015 net increase to the ARO further reflects higher assumed probabilities of early retirements of certain economically challenged nuclear plants (See Note 8 - Implications of Potential Early Plant Retirements for additional information) and net increases in the estimated costs for Peach Bottom and Salem nuclear units pursuant to updated decommissioning cost studies received during 2015; partially offset by reductions in estimated cost escalation rates, primarily for labor and energy costs. The financial statement impact related to the increase in the ARO due to the changes in, and timing of, estimated cash flows primarily resulted in a corresponding increase in Property, plant and equipment on Exelon’s and Generation’s Consolidated Balance Sheets. Approximately $8 million of the third quarter adjustment resulted in a credit to income, which is included in Operating and maintenance expense within Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. During the nine months ended September 30, 2014, Generation’s ARO increased by approximately $1.8 billion . The increase is largely driven by the recording of an ARO on Exelon’s and Generation’s Consolidated Balance Sheets at fair value, including subsequent purchase accounting adjustments, upon consolidation of CENG during the second quarter (see Note 6 - Investment in Constellation Energy Nuclear Group, LLC). The change in the ARO was also driven by an increase in the estimated costs to decommission the Byron and Braidwood nuclear units pursuant to updated decommissioning costs studies received during the third quarter 2014 as part of the annual assessment. These increases in the ARO were partially offset by decreases in the ARO due to reductions in estimated escalation rates, primarily for labor and energy costs. The increase in the ARO due to the changes in, and timing of, estimated cash flows primarily resulted in a corresponding increase in Property, plant and equipment on Exelon’s and Generation’s Consolidated Balance Sheets. Approximately $16 million of the change in the ARO resulted in a credit to income, which is included in Operating and maintenance expense within Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. Nuclear Decommissioning Trust Fund Investments At September 30, 2015 and December 31, 2014 , Exelon and Generation had NDT fund investments totaling $10,103 million and $10,537 million , respectively. The following table provides unrealized gains (losses) on NDT funds for the three and nine months ended September 30, 2015 and 2014 : Exelon and Generation Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Net unrealized gains (losses) on decommissioning trust funds — Regulatory Agreement Units (a) $ (301 ) $ (107 ) $ (385 ) $ 126 Net unrealized gains (losses) on decommissioning trust funds — Non-Regulatory Agreement Units (b)(c) (218 ) (41 ) (274 ) 100 ___________ (a) Net unrealized gains (losses) related to Generation’s NDT funds associated with Regulatory Agreement Units are included in Regulatory liabilities on Exelon’s Consolidated Balance Sheets and Noncurrent payables to affiliates on Generation’s Consolidated Balance Sheets. (b) Excludes $7 million of net unrealized gains related to the Zion Station pledged assets for the three months ended September 30, 2014 and $9 million and $27 million of net unrealized gains related to the Zion Station pledged assets for the nine months ended September 30, 2015 and 2014 , respectively. Net unrealized gains related to Zion Station pledged assets are included in the Payable for Zion Station decommissioning on Exelon’s and Generation’s Consolidated Balance Sheets. (c) Net unrealized gains (losses) related to Generation’s NDT funds with Non-Regulatory Agreement Units are included within Other, net in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. Interest and dividends on NDT fund investments are recognized when earned and are included in Other, net in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. Interest and dividends earned on the NDT fund investments for the Regulatory Agreement Units are eliminated within Other, net in Exelon’s and Generation’s Consolidated Statement of Operations and Comprehensive Income. Refer to Note 3 — Regulatory Matters and Note 25 — Related Party Transactions of the Exelon 2014 Form 10-K for information regarding regulatory liabilities at ComEd and PECO and intercompany balances between Generation, ComEd and PECO reflecting the obligation to refund to customers any decommissioning-related assets in excess of the related decommissioning obligations. Zion Station Decommissioning On September 1, 2010, Generation completed an Asset Sale Agreement (ASA) with EnergySolutions Inc. and its wholly owned subsidiaries, EnergySolutions, LLC (EnergySolutions) and ZionSolutions, under which ZionSolutions has assumed responsibility for completing certain decommissioning activities at Zion Station, which is located in Zion, Illinois and ceased operation in 1998. See Note 15 — Asset Retirement Obligations of the Exelon 2014 Form 10-K for information regarding the specific treatment of assets, including NDT funds, and decommissioning liabilities transferred in the transaction. ZionSolutions is subject to certain restrictions on its ability to request reimbursements from the Zion Station NDT funds as defined within the ASA. Therefore, the transfer of the Zion Station assets did not qualify for asset sale accounting treatment and, as a result, the related NDT funds were reclassified to Pledged assets for Zion Station decommissioning within Generation’s and Exelon’s Consolidated Balance Sheets and will continue to be measured in the same manner as prior to the completion of the transaction. Additionally, the transferred ARO for decommissioning was replaced with a Payable for Zion Station decommissioning in Generation’s and Exelon’s Consolidated Balance Sheets. Changes in the value of the Zion Station NDT assets, net of applicable taxes, are recorded as a change in the Payable to ZionSolutions. At no point will the payable to ZionSolutions exceed the project budget of the costs remaining to decommission Zion Station. Generation has retained its obligation for the SNF. Following ZionSolutions’ completion of its contractual obligations and transfer of the NRC license to Generation, Generation will store the SNF at Zion Station until it is transferred to the DOE for ultimate disposal, and will complete all remaining decommissioning activities associated with the SNF dry storage facility. Generation has a liability of approximately $82 million , which is included within the nuclear decommissioning ARO at September 30, 2015 . Generation also has retained NDT assets to fund its obligation to maintain the SNF at Zion Station until transfer to the DOE and to complete all remaining decommissioning activities for the SNF storage facility. Any shortage of funds necessary to maintain the SNF and decommission the SNF storage facility is ultimately required to be funded by Generation. Any Zion Station NDT funds remaining after the completion of all decommissioning activities will be returned to ComEd customers in accordance with the applicable orders. The following table provides the pledged assets and payables to ZionSolutions and withdrawals by ZionSolutions at September 30, 2015 and December 31, 2014 : Exelon and Generation September 30, 2015 December 31, 2014 Carrying value of Zion Station pledged assets $ 237 $ 319 Payable to Zion Solutions (a) 217 292 Current portion of payable to Zion Solutions (b) 118 137 Cumulative withdrawals by Zion Solutions to pay decommissioning and other costs (c) 757 666 ___________ (a) Excludes a liability recorded within Exelon’s and Generation’s Consolidated Balance Sheets related to the tax obligation on the unrealized activity associated with the Zion Station NDT Funds. The NDT Funds will be utilized to satisfy the tax obligations as gains and losses are realized. (b) Included in Other current liabilities within Exelon’s and Generation’s Consolidated Balance Sheets. (c) Includes project expenses to decommission Zion Station and estimated tax payments on Zion Station NDT Fund earnings. NRC Minimum Funding Requirements NRC regulations require that licensees of nuclear generating facilities demonstrate reasonable assurance that funds will be available in specified minimum amounts to decommission the facility at the end of its life. Generation filed its biennial decommissioning funding status report with the NRC on March 31, 2015. This report reflects the status of decommissioning funding assurance as of December 31, 2014. Due to increased cost estimates received in the second half of 2014, Braidwood Unit 1, Braidwood Unit 2, and Byron Unit 2 did not meet the NRC's minimum funding assurance criteria as of December 31, 2014. NRC guidance provides licensees with two years or by the time of submitting the next biennial report (on or before March 31, 2017) to resolve funding assurance shortfalls. During this period, Generation will monitor funding assurance and new developments, including the impact of a 20-year license renewal for Braidwood and Byron, to assess the status of funding assurance and to take steps, if necessary, to address any funding shortfall on these funds on or before March 31, 2017. The increased security costs discussed above will be taken into consideration, as appropriate and in accordance with the regulatory requirements, in Generation's future decommissioning funding status reports submitted to the NRC. Generation does not expect the increased costs to change Generation's NRC minimum funding assurance status.

Retirement Benefits (Exelon, Ge

Retirement Benefits (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Retirement Benefits (Exelon, Generation, ComEd, PECO and BGE)	Retirement Benefits (Exelon, Generation, ComEd, PECO and BGE) Exelon sponsors defined benefit pension plans and other postretirement benefit plans for essentially all Generation, ComEd, PECO, BGE and BSC employees. Defined Benefit Pension and Other Postretirement Benefits During the first quarter of 2015, Exelon received an updated valuation of its pension and other postretirement benefit obligations to reflect actual census data as of January 1, 2015. This valuation resulted in an increase to the pension obligation of $45 million and an increase to the other postretirement benefit obligation of $57 million . Additionally, accumulated other comprehensive loss increased by approximately $27 million (after tax), regulatory assets increased by approximately $48 million , and regulatory liabilities decreased by approximately $11 million . The majority of the 2015 pension benefit cost for Exelon-sponsored plans is calculated using an expected long-term rate of return on plan assets of 7.00% and a discount rate of 3.94% . The majority of the 2015 other postretirement benefit cost is calculated using an expected long-term rate of return on plan assets of 6.46% for funded plans and a discount rate of 3.92% . A portion of the net periodic benefit cost is capitalized within the Consolidated Balance Sheets. The following tables present the components of Exelon’s net periodic benefit costs, prior to any capitalization, for the three and nine months ended September 30, 2015 and 2014 . Pension Benefits Three Months Ended September 30, Other Postretirement Benefits Three Months Ended September 30, 2015 (a) 2014 (a) 2015 (a) 2014 (a) Service cost $ 82 $ 74 $ 30 $ 27 Interest cost 178 189 42 42 Expected return on assets (257 ) (251 ) (38 ) (39 ) Amortization of: Prior service cost (benefit) 3 3 (43 ) (44 ) Actuarial loss 142 106 20 15 Net periodic benefit cost $ 148 $ 121 $ 11 $ 1 Pension Benefits Nine Months Ended September 30, Other Postretirement Benefits Nine Months Ended September 30, 2015 (b) 2014 (b) 2015 (b) 2014 (b) Service cost $ 245 $ 218 $ 89 $ 90 Interest cost 533 561 125 144 Expected return on assets (770 ) (743 ) (113 ) (115 ) Amortization of: Prior service cost (benefit) 10 10 (130 ) (79 ) Actuarial loss 427 316 60 35 Net periodic benefit cost $ 445 $ 362 $ 31 $ 75 ______________ (a) For the three months ended September 30, 2015 , the cost for pension benefits and other postretirement benefits related to CENG were $2 million and $3 million , respectively. For the three months ended September 30, 2014, the cost for pension benefits and other postretirement benefits related to CENG were $2 million and $3 million , respectively. CENG amounts are included in the tables above. (b) For the nine months ended September 30, 2015 , the cost for pension benefits and other postretirement benefits related to CENG were $8 million and $8 million , respectively. For the period of April 1, 2014 to September 30, 2014, the cost for pension benefits and other postretirement benefits related to CENG were $5 million and $6 million , respectively. CENG amounts are included in the tables above. The amounts below represent Generation’s, ComEd’s, PECO’s, BGE’s and BSC's allocated portion of the pension and postretirement benefit plan costs, which were included in Property, plant and equipment within the respective Consolidated Balance Sheets and Operating and maintenance expense within the Consolidated Statement of Operations and Comprehensive Income during the three and nine months ended September 30, 2015 and 2014 . Three Months Ended September 30, Nine Months Ended September 30, Pension and Other Postretirement Benefit Costs 2015 2014 2015 2014 Generation (a) $ 67 $ 54 $ 200 $ 193 ComEd 52 33 155 129 PECO 10 7 29 28 BGE 16 17 49 50 BSC (b) 14 11 43 37 ______________ (a) For the three and nine months ended September 30, 2015 , the costs related to CENG were $5 million and $16 million , respectively. For the three months ended September 30, 2014, the costs related to CENG were $5 million . For the period of April 1, 2014 to September 30, 2014, the costs related to CENG were $11 million . CENG amounts are included in the table above. (b) These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO or BGE amounts above. Defined Contribution Savings Plans The Registrants participate in various 401(k) defined contribution savings plans that are sponsored by Exelon. The plans are qualified under applicable sections of the IRC and allow employees to contribute a portion of their pre-tax income in accordance with specified guidelines. All Registrants match a percentage of the employee contributions up to certain limits. The following table presents the matching contributions to the savings plans during the three and nine months ended September 30, 2015 and 2014 : Three Months Ended September 30, Nine Months Ended September 30, Savings Plan Matching Contributions 2015 2014 2015 2014 Exelon (a) $ 51 $ 34 $ 111 $ 82 Generation (a) 27 17 60 41 ComEd 10 8 23 20 PECO 3 2 7 6 BGE 5 3 10 7 BSC (b) 6 4 11 8 _______________ (a) Includes $4 million and $8 million , respectively, related to CENG for the three and nine months ended September 30, 2015 . Includes $1 million related to CENG for the three months ended September 30, 2014 and for the period from April 1, 2014 to September 30, 2014. (b) These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These costs are not included in the Generation, ComEd, PECO or BGE amounts above.

Severance (Exelon, Generation,

Severance (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Restructuring Charges [Abstract]
Severance (Exelon, Generation, ComEd, PECO and BGE)	Severance (Exelon, Generation, ComEd, PECO and BGE) The Registrants have an ongoing severance plan under which, in general, the longer an employee worked prior to termination the greater the amount of severance benefits. The Registrants record a liability and expense or regulatory asset for severance once terminations are probable of occurrence and the related severance benefits can be reasonably estimated. For severance benefits that are incremental to its ongoing severance plan (“one-time termination benefits”), the Registrants measure the obligation and record the expense at fair value at the communication date if there are no future service requirements, or, if future service is required to receive the termination benefit, ratably over the required service period. Ongoing Severance Plans The Registrants provide severance, health and welfare benefits under Exelon’s ongoing severance benefit plans to terminated employees in the normal course of business. These benefits are accrued for when the benefits are considered probable and can be reasonably estimated. For the three and nine months ended September 30, 2015 and 2014 , the Registrants recorded the following severance costs (benefits) associated with these ongoing severance benefits within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income: Exelon Generation ComEd PECO BGE Three Months Ended September 30, 2015 $ (3 ) $ (3 ) $ — $ — $ — September 30, 2014 (2 ) (2 ) — — — Nine Months Ended September 30, 2015 $ 18 $ 17 $ 1 $ — $ — September 30, 2014 4 3 1 — — The severance liability balances associated with these ongoing severance benefits as of September 30, 2015 and December 31, 2014 are not material.

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Income (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Changes in Accumulated Other Comprehensive Income [Abstract]
Comprehensive Income (Loss) Note [Text Block]	Changes in Accumulated Other Comprehensive Income (Exelon, Generation, and PECO) The following tables present changes in accumulated other comprehensive income (loss) (AOCI) by component for the nine months ended September 30, 2015 and 2014 : Nine Months Ended September 30, 2015 Gains and (Losses) on Hedging Activity Unrealized Gains and (Losses) on Marketable Securities Pension and Non-Pension Postretirement Benefit Plan Items Foreign Currency Items AOCI of Equity Investments Total Exelon (a) Beginning balance $ (28 ) $ 3 $ (2,640 ) $ (19 ) $ — $ (2,684 ) OCI before reclassifications (18 ) — (29 ) (17 ) — (64 ) Amounts reclassified from AOCI (b) 22 — 130 — — 152 Net current-period OCI 4 — 101 (17 ) — 88 Ending balance $ (24 ) $ 3 $ (2,539 ) $ (36 ) $ — $ (2,596 ) Generation (a) Beginning balance $ (18 ) $ 1 $ — $ (19 ) $ — $ (36 ) OCI before reclassifications (13 ) — — (17 ) — (30 ) Amounts reclassified from AOCI (b) 6 — — — — 6 Net current-period OCI (7 ) — — (17 ) — (24 ) Ending balance $ (25 ) $ 1 $ — $ (36 ) $ — $ (60 ) PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 ______________ (a) All amounts are net of tax. Amounts in parentheses represent a decrease in accumulated other comprehensive income. (b) See tables following changes in accumulated other comprehensive income tables for details about these reclassifications. Nine Months Ended September 30, 2014 Gains Unrealized Gains and (Losses) on Marketable Securities Pension and Non-Pension Postretirement Benefit Plan Items Foreign Currency Items AOCI of Equity Investments Total Exelon (a) Beginning balance $ 120 $ 2 $ (2,260 ) $ (10 ) $ 108 $ (2,040 ) OCI before reclassifications (14 ) (2 ) 240 (6 ) 11 229 Amounts reclassified from AOCI (b) (78 ) — 91 — (119 ) (106 ) Net current-period OCI (92 ) (2 ) 331 (6 ) (108 ) 123 Ending balance $ 28 $ — $ (1,929 ) $ (16 ) $ — $ (1,917 ) Generation (a) Beginning balance $ 114 $ 2 $ — $ (10 ) $ 108 $ 214 OCI before reclassifications (8 ) (3 ) — (6 ) 11 (6 ) Amounts reclassified from AOCI (b) (78 ) — — — (119 ) (197 ) Net current-period OCI (86 ) (3 ) — (6 ) (108 ) (203 ) Ending balance $ 28 $ (1 ) $ — $ (16 ) $ — $ 11 PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 _______________ (a) All amounts are net of tax. Amounts in parentheses represent a decrease in accumulated other comprehensive income. (b) See tables following changes in accumulated other comprehensive income tables for details about these reclassifications. ComEd, PECO, and BGE did not have any reclassifications out of AOCI to Net income during the three and nine months ended September 30, 2015 and 2014 . The following tables present amounts reclassified out of AOCI to Net income for Exelon and Generation during the three and nine months ended September 30, 2015 and 2014 . Three Months Ended September 30, 2015 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statements of Operations and Comprehensive Income Exelon Generation Gains (losses) on hedging activity Other cash flow hedges $ (4 ) $ (4 ) Interest expense (4 ) (4 ) Total before tax 1 1 Tax benefit $ (3 ) $ (3 ) Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 19 $ — Actuarial losses (b) (90 ) — (71 ) — Total before tax 28 — Tax benefit $ (43 ) $ — Net of tax Total Reclassifications for the period $ (46 ) $ (3 ) Net of Tax Nine Months Ended September 30, 2015 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statements of Operations and Comprehensive Income Exelon Generation Gains (losses) on hedging activity Terminated interest rate swaps (c) $ (26 ) $ — Other, net Energy related hedges 2 2 Operating revenues Other cash flow hedges (11 ) (11 ) Interest expense (35 ) (9 ) Total before tax 13 3 Tax benefit $ (22 ) $ (6 ) Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 57 $ — Actuarial losses (b) (270 ) — (213 ) — Total before tax 83 — Tax benefit $ (130 ) $ — Net of tax Total Reclassifications for the period $ (152 ) $ (6 ) Net of Tax Three months ended September 30, 2014 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statements of Operations and Comprehensive Income Exelon Generation Gains on hedging activity Energy related hedges $ 28 $ 28 Operating revenues 28 28 Total before tax (12 ) (12 ) Tax (expense) $ 16 $ 16 Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 19 $ — Actuarial losses (b) (61 ) — (42 ) — Total before tax 16 — Tax benefit $ (26 ) $ — Net of tax Equity investments Reversal of CENG equity method AOCI $ 5 $ 5 Gain on consolidation of CENG 5 5 Total before tax (2 ) (2 ) Tax benefit $ 3 $ 3 Net of tax Total reclassifications for the period $ (7 ) $ 19 Net of Tax Nine Months Ended September 30, 2014 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statements of Operations and Comprehensive Income Exelon Generation Gains on hedging activity Energy related hedges $ 130 $ 130 Operating revenues 130 130 Total before tax (52 ) (52 ) Tax (expense) $ 78 $ 78 Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 29 $ — Actuarial losses (b) (178 ) — (149 ) — Total before tax 58 — Tax benefit $ (91 ) $ — Net of tax Equity investments Sale of equity method investment $ 5 $ 5 Gain on consolidation of CENG Reversal of CENG equity method AOCI 193 193 Gain on consolidation of CENG 198 198 Total before tax (79 ) (79 ) Tax benefit $ 119 $ 119 Net of tax Total reclassifications for the period $ 106 $ 197 Net of Tax ____________ (a) All amounts are net of tax. Amounts in parentheses represent a decrease in net income. (b) This accumulated other comprehensive income component is included in the computation of net periodic pension and OPEB cost (see Note 14 — Retirement Benefits for additional details). (c) In January 2015, in connection with Generation's $750 million issuance of five-year Senior Unsecured Notes, Exelon terminated certain floating-to-fixed interest rate swaps. As the original forecasted transactions were a series of future interest payments over a ten year period, a portion of the anticipated interest payments are probable not to occur. As a result, $26 million of anticipated payments were reclassified from Accumulated OCI to Other, net in Exelon's Consolidated Statement of Operations and Comprehensive Income. The following table presents income tax expense (benefit) allocated to each component of other comprehensive income (loss) during the three and nine months ended September 30, 2015 and 2014 : Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Exelon Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 8 $ 8 $ 22 $ 11 Actuarial loss reclassified to periodic cost (35 ) (24 ) (105 ) (69 ) Pension and non-pension postretirement benefit plans valuation adjustment — 5 17 (153 ) Change in unrealized (gain) loss on cash flow hedges 3 15 (3 ) 62 Change in unrealized income on equity investments — 3 — 73 Change in unrealized loss on marketable securities — 1 — (1 ) Total $ (24 ) $ 8 $ (69 ) $ (77 ) Generation Change in unrealized loss on cash flow hedges $ 3 $ 13 $ 4 $ 57 Change in unrealized income on equity investments — 3 — 73 Change in marketable securities — 1 — (1 ) Total $ 3 $ 17 $ 4 $ 129

Common Stock (Exelon, Generatio

Common Stock (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Common Stock [Abstract]
Common Stock (Exelon, Generation, ComEd, PECO and BGE)	17 . Common Stock (Exelon) Equity Securities Offering In June 2014, Exelon marketed an equity offering of 57.5 million shares of its common stock at a public offering price of $35 per share and entered into forward sale agreements with two counterparties. In July 2015, Exelon settled the forward sale agreements by the issuance of 57.5 million shares of Exelon common stock. Exelon received net cash proceeds of $1.87 billion , which was calculated based on a forward price of $32.48 per share as specified in the forward sale agreements. Use of net proceeds will be to fund the pending acquisition of PHI and related costs and expenses, and for general corporate purposes. The forward sale agreements are classified as equity transactions. As a result, no amounts were recorded in the consolidated financial statements until the July 2015 settlement of the forward sale agreements. However, prior to the July 2015 settlement, incremental shares, if any, were included within the calculation of diluted EPS using the treasury stock method. For further information on the transaction, refer to Note 19 — Common Stock of the Exelon 2014 Form 10-K. Concurrent with the June 2014 forward equity transaction, Exelon also issued $1.15 billion of junior subordinated notes in the form of 23 million equity units. See Note 11 — Debt and Credit Agreements for further information on the equity units.

Earnings Per Share and Equity (

Earnings Per Share and Equity (Exelon)	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Earnings Per Share and Equity (Exelon)	Earnings Per Share and Equity (Exelon) Earnings per Share (Exelon) Diluted earnings per share is calculated by dividing Net income attributable to common shareholders by the weighted average number of shares of common stock outstanding adjusted to include the potentially dilutive effect of stock options, performance share awards and restricted stock outstanding under Exelon’s LTIPs. The following table sets forth the components of basic and diluted earnings per share and shows the effect of these stock options, performance share awards and restricted stock on the weighted average number of shares outstanding (in millions) used in calculating diluted earnings per share: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Net income attributable to common shareholders $ 629 $ 993 $ 1,959 $ 1,604 Average common shares outstanding — basic 913 861 879 860 Potentially dilutive effect of stock options, performance share awards and restricted stock 2 2 4 3 Average common shares outstanding — diluted 915 863 883 863 The number of stock options not included in the calculation of diluted common shares outstanding due to their antidilutive effect was approximately 14 million for the three and nine months ended September 30, 2015 and 16 million for the three and nine months ended September 30, 2014 . The number of equity units related to the PHI merger not included in the calculation of diluted common shares outstanding due to their antidilutive effect was 4 million and 2 million for the three and nine months ended September 30, 2015 , respectively, and 2 million for the three months ended September 30, 2014 and 1 million for the nine months ended September 30, 2014. Additionally, there were no forward units related to the PHI merger not included in the calculation of diluted common shares outstanding due to their antidilutive effect for the three and nine months ended September 30, 2015 , and approximately 2 million not included for the three months ended September 30, 2014 and 1 million not included for the nine months ended September 30, 2014 . Refer to Note 17 — Common Stock for further information regarding the equity units and equity forward units. Under share repurchase programs, 35 million shares of common stock are held as treasury stock with a cost of $2.3 billion as of September 30, 2015 . In 2008, Exelon management decided to defer indefinitely any share repurchases.

Commitments and Contingencies (

Commitments and Contingencies (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies (Exelon, Generation, ComEd, PECO and BGE)	Commitments and Contingencies (Exelon, Generation, ComEd, PECO and BGE) The following is an update to the current status of commitments and contingencies set forth in Note 22 of the Exelon 2014 Form 10-K. Commitments Constellation Merger Commitments In February 2012, the MDPSC issued an Order approving the Exelon and Constellation merger. As part of the MDPSC Order, Exelon agreed to provide a package of benefits to BGE customers, the City of Baltimore and the State of Maryland, resulting in an estimated direct investment in the State of Maryland of approximately $1 billion . The direct investment estimate includes $95 million to $120 million relating to the construction of a headquarters building in Baltimore for Generation’s competitive energy businesses. On March 20, 2013, Generation signed a 20 year lease agreement for office space that was contingent upon the developer obtaining all required approvals, permits and financing for the construction of a building in Baltimore, Maryland. The operating lease became effective during the second quarter of 2014 when these outstanding contingencies were met by the developer. Generation's total commitments under the lease agreement are $ 0 million, $ 5 million , $ 12 million , $ 13 million , $ 13 million , and $ 285 million , related to 2015, 2016, 2017, 2018, 2019 and thereafter. The direct investment commitment also includes $575 million to $ 650 million relating to Exelon and Generation’s development or assistance in the development of 275 — 300 MWs of new generation in Maryland, which is expected to be completed within a period of 10 years. Exelon and Generation have incurred $ 353 million towards satisfying the commitment for new generation development in the state of Maryland, with approximately 160 MW of the new generation commencing with commercial operations to date. The MDPSC order contemplates various options for complying with the new generation development commitments, including building or acquiring generating assets, making subsidy or compliance payments, or in circumstances in which the generation build is delayed or certain specified provisions are elected, making liquidated damages payments. Exelon and Generation expect that the majority of these commitments will be satisfied by building or acquiring generating assets and, therefore, will be primarily capital in nature and recognized as incurred. However, during the third quarter of 2014, the conditions associated with one of the generation development commitments changed such that Exelon and Generation now believe that the most likely outcome will involve making subsidy payments and/or liquidated damages payments rather than constructing the specified generating plant. As a result, Exelon and Generation recorded a pre-tax $44 million loss contingency related to this generation development commitment which is included in Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income for the nine and three months ended September 30, 2014. While this $ 44 million loss contingency represents Generation’s best estimate of the future obligation, it is reasonably possible that Exelon and Generation could ultimately be required to make cumulative subsidy payments of up to a maximum of approximately $105 million over a 20 -year period dependent on actual generating output from a successfully constructed generating plant. See Note 4 — Mergers, Acquisitions, and Dispositions of the Exelon 2014 Form 10-K for additional information regarding the Constellation merger commitments. Equity Investment Commitments As part of Generation's investments in technology development, Generation enters into equity purchase agreements that include commitments to invest additional equity through incremental payments to fund the anticipated needs of the planned operations of the associated companies. The commitment includes approximately $20 million of in-kind services. As of September 30, 2015 , Generation’s estimated commitment relating to its equity purchase agreements, including in-kind services contributions, is anticipated to be as follows: Total 2015 $ 38 2016 276 2017 23 2018 7 2019 2 Total $ 346 Contingencies Commercial Commitments The Registrants’ commercial commitments as of September 30, 2015 , representing commitments potentially triggered by future events were as follows: Exelon Generation ComEd PECO BGE Letters of credit (non-debt) (a) $ 1,078 $ 1,011 $ 18 $ 22 $ 1 Guarantees 5,823 (b) 3,159 (c) 205 (d) 188 (e) 263 (f) Nuclear insurance premiums (g) 3,057 3,057 — — — Total commercial commitments $ 9,958 $ 7,227 $ 223 $ 210 $ 264 ___________________ (a) Non-debt letters of credit maintained to provide credit support for certain transactions as requested by third parties. (b) Primarily reflects parental guarantees issued on behalf of Generation to allow the flexibility needed to conduct business with counterparties without having to post other forms of collateral. Also reflects guarantees issued to ensure performance under specific contracts, preferred securities of financing trusts, property leases, indemnifications, NRC minimum funding assurance requirements and miscellaneous guarantees. The estimated net exposure for obligations under commercial transactions covered by these guarantees was $650 million at September 30, 2015 , which represents the total amount Exelon could be required to fund based on September 30, 2015 market prices. (c) Primarily reflects guarantees issued to ensure performance under energy marketing and other specific contracts. The estimated net exposure for obligations under commercial transactions covered by these guarantees was $475 million at September 30, 2015 , which represents the total amount Generation could be required to fund based on September 30, 2015 market prices. (d) Primarily reflects full and unconditional guarantees of $200 million Trust Preferred Securities of ComEd Financing III, which is a 100% owned finance subsidiary of ComEd. (e) Primarily reflects full and unconditional guarantees of $178 million Trust Preferred Securities of PECO Trust III and IV, which are 100% owned finance subsidiaries of PECO. (f) Primarily reflects full and unconditional guarantees of $250 million Trust Preferred Securities of BGE Capital Trust II, which is a 100% owned finance subsidiary of BGE. (g) Represents the maximum amount that Generation would be required to pay for retrospective premiums in the event of nuclear disaster at any domestic site, including CENG sites, under the Secondary Financial Protection pool as required under the Price-Anderson Act as well as the current aggregate annual retrospective premium obligation that could be imposed by NEIL. See the Nuclear Insurance section within this note for additional details on Generation’s nuclear insurance premiums. Nuclear Insurance (Exelon and Generation) Generation is subject to liability, property damage and other risks associated with major incidents at any of its nuclear stations, including the CENG nuclear stations. Generation has mitigated its financial exposure to these risks through insurance and other industry risk-sharing provisions. The Price-Anderson Act was enacted to ensure the availability of funds for public liability claims arising from an incident at any of the U.S. licensed nuclear facilities and also to limit the liability of nuclear reactor owners for such claims from any single incident. As of September 30, 2015 , the current liability limit per incident was $ 13.4 billion and is subject to change to account for the effects of inflation and changes in the number of licensed reactors. An inflation adjustment must be made at least once every 5 years and the last inflation adjustment was made effective September 10, 2013. In accordance with the Price-Anderson Act, Generation maintains financial protection at levels equal to the amount of liability insurance available from private sources through the purchase of private nuclear energy liability insurance for public liability claims that could arise in the event of an incident. As of September 30, 2015 , the amount of nuclear energy liability insurance purchased is $ 375 million for each operating site. Additionally, the Price-Anderson Act requires a second layer of protection through the mandatory participation in a retrospective rating plan for power reactors (currently 102 reactors) resulting in an additional $ 12.9 billion in funds available for public liability claims. Participation in this secondary financial protection pool requires the operator of each reactor to fund its proportionate share of costs for any single incident that exceeds the primary layer of financial protection. Under the Price-Anderson Act, the maximum assessment in the event of an incident for each nuclear operator, per reactor, per incident (including a 5% surcharge), is $127.3 million , payable at no more than $ 19 million per reactor per incident per year. Exelon’s maximum liability per incident is approximately $ 2.7 billion , including CENG's related liability. In addition, the U.S. Congress could impose revenue-raising measures on the nuclear industry to pay public liability claims exceeding the $ 13.4 billion limit for a single incident. As part of the execution of the NOSA on April 1, 2014, Generation executed an Indemnity Agreement pursuant to which Generation agreed to indemnify EDF and its affiliates against third-party claims that may arise from any future nuclear incident (as defined in the Price Anderson Act) in connection with the CENG nuclear plants or their operations. Exelon guarantees Generation’s obligations under this indemnity. See Note 6 — Investment in Constellation Energy Nuclear Group, LLC for additional information on Generation’s operations relating to CENG. Generation is required each year to report to the NRC the current levels and sources of property insurance that demonstrates Generation possesses sufficient financial resources to stabilize and decontaminate a reactor and reactor station site in the event of an accident. The property insurance maintained for each facility is currently provided through insurance policies purchased from NEIL, an industry mutual insurance company of which Generation is a member. NEIL provides “all risk” property damage, decontamination and premature decommissioning insurance for each station for losses resulting from damage to its nuclear plants, either due to accidents or acts of terrorism. If the decision is made to decommission the facility, a portion of the insurance proceeds will be allocated to a fund, which Generation is required by the NRC to maintain, to provide for decommissioning the facility. In the event of an insured loss, Generation is unable to predict the timing of the availability of insurance proceeds to Generation and the amount of such proceeds that would be available. In the event that one or more acts of terrorism cause accidental property damage within a twelve-month period from the first accidental property damage under one or more policies for all insured plants, the maximum recovery for all losses by all insureds will be an aggregate of $ 3.2 billion plus such additional amounts as the insurer may recover for all such losses from reinsurance, indemnity and any other source, applicable to such losses. For its insured losses, Generation is self-insured to the extent that losses are within the policy deductible or exceed the amount of insurance maintained. Uninsured losses and other expenses, to the extent not recoverable from insurers or the nuclear industry, could also be borne by Generation. Any such losses could have a material adverse effect on Exelon’s and Generation’s financial condition, results of operations and liquidity. Environmental Issues General. The Registrants’ operations have in the past, and may in the future, require substantial expenditures in order to comply with environmental laws. Additionally, under Federal and state environmental laws, the Registrants are generally liable for the costs of remediating environmental contamination of property now or formerly owned by them and of property contaminated by hazardous substances generated by them. The Registrants own or lease a number of real estate parcels, including parcels on which their operations or the operations of others may have resulted in contamination by substances that are considered hazardous under environmental laws. In addition, the Registrants are currently involved in a number of proceedings relating to sites where hazardous substances have been deposited and may be subject to additional proceedings in the future. ComEd, PECO and BGE have identified sites where former MGP activities have or may have resulted in actual site contamination. For almost all of these sites, there are additional PRPs that may share responsibility for the ultimate remediation of each location. • ComEd has identified 42 sites, 17 of which the remediation has been completed and approved by the Illinois EPA or the U.S. EPA and 25 that are currently under some degree of active study and/or remediation. ComEd expects the majority of the remediation at these sites to continue through at least 2020. • PECO has identified 26 sites, 16 of which have been remediated in accordance with applicable PA DEP regulatory requirements. The remaining 10 sites are currently under some degree of active study and/or remediation. PECO expects the majority of the remediation at these sites to continue through at least 2021. • BGE has identified 13 former gas manufacturing or purification sites that it currently owns or owned at one time through a predecessor’s acquisition. Two gas manufacturing sites require some level of remediation and ongoing monitoring under the direction of the MDE. The required costs at these two sites are not considered material. An investigation of an additional gas purification site was completed during the first quarter of 2015 at the direction of the MDE. For more information, see the discussion of the Riverside site below. ComEd, pursuant to an ICC order, and PECO, pursuant to settlements of natural gas distribution rate cases with the PAPUC, are currently recovering environmental remediation costs of former MGP facility sites through customer rates. ComEd and PECO have recorded regulatory assets for the recovery of these costs. See Note 5 — Regulatory Matters for additional information regarding the associated regulatory assets. BGE is authorized to recover, and is currently recovering, environmental costs for the remediation of the former MGP facility sites from customers; however, while BGE does not have a rider for MGP clean-up costs, BGE has historically received recovery of actual clean-up costs in distribution rates. As of September 30, 2015 and December 31, 2014 , the Registrants had accrued the following undiscounted amounts for environmental liabilities in Other current liabilities and Other deferred credits and other liabilities within their respective Consolidated Balance Sheets: September 30, 2015 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 376 $ 309 Generation 63 — ComEd 269 268 PECO 41 39 BGE 3 2 December 31, 2014 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 347 $ 277 Generation 63 — ComEd 238 235 PECO 45 42 BGE 1 — The historical nature of the MGP sites and the fact that many of the sites have been buried and built over, impacts the ability to determine a precise estimate of the ultimate costs prior to initial sampling and determination of the exact scope and method of remedial activity. Management determines its best estimate of remediation costs using all available information at the time of each study, including probabilistic and deterministic modeling for ComEd and PECO, and the remediation standards currently required by the applicable state environmental agency. Prior to completion of any significant clean up, each site remediation plan is approved by the appropriate state environmental agency. During the third quarter of 2015, ComEd and PECO completed an annual study of their future estimated MGP remediation requirements. For ComEd, the results of the study resulted in a $ 50 million increase to ComEd's environmental liabilities and related regulatory assets. The increase at ComEd was primarily driven by refined assumptions and scopes based on further experience and analysis, including one site where a new option is being considered for a facility under which contamination exists and certain sites where another PRP leads the remediation efforts and ComEd shares responsibility. For PECO, the results of the study resulted in a $1 million decrease to PECO's environmental liabilities and related regulatory assets. The Registrants cannot reasonably estimate whether they will incur other significant liabilities for additional investigation and remediation costs at these or additional sites identified by the Registrants, environmental agencies or others, or whether such costs will be recoverable from third parties, including customers. Water Quality Groundwater Contamination. In October 2007, a subsidiary of Constellation entered into a consent decree with the MDE relating to groundwater contamination at a third-party facility that was licensed to accept fly ash, a byproduct generated by coal-fired plants. The consent decree required the payment of a $1 million penalty, remediation of groundwater contamination resulting from the ash placement operations at the site, replacement of drinking water supplies in the vicinity of the site, and monitoring of groundwater conditions. Generation's remaining groundwater contamination reserve was $ 12 million at September 30, 2015 and $ 13 million at December 31, 2014 . Air Quality Notices and Finding of Violations and Midwest Generation Bankruptcy. In December 1999, ComEd sold several generating stations to Midwest Generation, LLC (Midwest Generation), a subsidiary of Edison Mission Energy (EME). Under the terms of the sale agreement, Midwest Generation and EME assumed responsibility for environmental liabilities associated with the ownership, occupancy, use and operation of the stations, including responsibility for compliance by the stations with environmental laws before their purchase by Midwest Generation. Midwest Generation and EME additionally agreed to indemnify and hold ComEd and its affiliates harmless from claims, fines, penalties, liabilities and expenses arising from third party claims against ComEd resulting from or arising out of the environmental liabilities assumed by Midwest Generation and EME under the terms of the agreement governing the sale. In connection with Exelon’s 2001 corporate restructuring, Generation assumed ComEd’s rights and obligations with respect to its former generation business, including its rights and obligations under the sale agreement with Midwest Generation and EME. Under a supplemental agreement reached in 2003, Midwest Generation agreed to reimburse ComEd and Generation for 50% of the specific asbestos claims pending as of February 2003 and related expenses less recovery of insurance costs and agreed to a sharing arrangement for liabilities and expenses associated with future asbestos-related claims as specified in the agreement. On December 17, 2012 (Petition Date), EME and certain of its subsidiaries, including Midwest Generation, filed for protection under Chapter 11 of the U.S. Bankruptcy Code. In 2012, the Bankruptcy Court approved the rejection of an agency agreement related to a coal rail car lease under which Midwest Generation had agreed to reimburse ComEd for all obligations incurred under the coal rail car lease. The rejection left Generation as the party responsible for making all remaining payments under the lease and performing all other obligations thereunder. A settlement was reached in January 2015, to resolve the claims related to the coal rail car lease for approximately $14 million and Exelon recorded a gain upon receipt of the funds, within Operating and maintenance expense in Exelon and Generation's Consolidated Statement of Operations and Comprehensive Income. No further action is expected related to the rail car lease. On March 11, 2014, the Bankruptcy Court for the Northern District of Illinois entered its Order Confirming Debtors’ Joint Chapter 11 Plan of Reorganization. On April 1, 2014 (Effective Date), NRG Energy purchased EME’s portfolio of generation, including Midwest Generation and the Joint Chapter 11 Plan of Reorganization (Plan) became effective. As part of the Plan, the sale agreement, including the environmental indemnity, and the asbestos cost-sharing agreement were rejected. Generation increased its reserve for asbestos-related bodily injury claims pertaining to Midwest Generations’ share of liability as a result of the rejection of the asbestos cost sharing agreement in the bankruptcy proceedings. Exelon and Generation may be entitled to damages associated with the rejection of the agreement and a claim has been filed by Exelon for such damages. These amounts are considered to be contingent gains and would not be recognized until realized. As a prior owner of the generating stations, ComEd (and Generation, through its agreement in Exelon’s 2001 corporate restructuring to assume ComEd’s rights and obligations associated with its former generation business) could face liability (along with any other potentially responsible parties) for environmental conditions at the stations requiring remediation, with the determination of the allocation among the parties subject to many uncertain factors. ComEd and Generation are unable to predict whether and to what extent they may ultimately be held responsible for remediation and other costs relating to the generating stations and as a result no liability has been recorded as of September 30, 2015 . Any liability imposed on ComEd or Generation for environmental matters relating to the generating stations could have a material adverse impact on their future results of operations and cash flows. Solid and Hazardous Waste Cotter Corporation. The U.S. EPA has advised Cotter Corporation (Cotter), a former ComEd subsidiary, that it is potentially liable in connection with radiological contamination at a site known as the West Lake Landfill in Missouri. On February 18, 2000, ComEd sold Cotter to an unaffiliated third- party. As part of the sale, ComEd agreed to indemnify Cotter for any liability arising in connection with the West Lake Landfill. In connection with Exelon’s 2001 corporate restructuring, this responsibility to indemnify Cotter was transferred to Generation. On May 29, 2008, the U.S. EPA issued a Record of Decision approving the remediation option submitted by Cotter and the two other PRPs that required additional landfill cover. By letter dated January 11, 2010, the U.S. EPA requested that the PRPs perform a supplemental feasibility study for a remediation alternative that would involve complete excavation of the radiological contamination. On September 30, 2011, the PRPs submitted the final supplemental feasibility study to the U.S. EPA for review. Since June 2012, the U.S. EPA has requested that the PRPs perform a series of additional analyses and groundwater and soil sampling as part of the supplemental feasibility study, that are now scheduled to be conducted through 2016. In light of these additional requests, it is unknown when the U.S EPA will propose a remedy for public comment, but will likely be sometime in 2017 at the earliest. Thereafter the U.S. EPA will select a final remedy and enter into a Consent Decree with the PRPs to effectuate the remedy. A complete excavation remedy would be significantly more expensive than the previously selected additional cover remedy; however, Generation believes the likelihood that the U.S. EPA would require a complete excavation remedy is remote. The U.S. EPA is also reviewing a partial excavation remedy; however , until the current sampling is concluded there is no basis to determine the likelihood and estimate of a partial excavation remedy. The current estimated cost of the landfill cover remediation for the site is approximately $60 million , which will be allocated among all PRPs. Recent investigation has identified a number of other parties who may be PRPs and could be liable to contribute to the final remedy. Further investigation is underway. Generation has accrued what it believes to be an adequate amount to cover its anticipated share of such liability. On August 8, 2011, Cotter was notified by the DOJ that Cotter is considered a PRP with respect to the government’s clean-up costs for contamination attributable to low level radioactive residues at a former storage and reprocessing facility named Latty Avenue near St. Louis, Missouri. The Latty Avenue site is included in ComEd’s indemnification responsibilities discussed above as part of the sale of Cotter. The radioactive residues had been generated initially in connection with the processing of uranium ores as part of the U.S. government’s Manhattan Project. Cotter purchased the residues in 1969 for initial processing at the Latty Avenue facility for the subsequent extraction of uranium and metals. In 1976, the NRC found that the Latty Avenue site had radiation levels exceeding NRC criteria for decontamination of land areas. Latty Avenue was investigated and remediated by the United States Army Corps of Engineers pursuant to funding under the Formerly Utilized Sites Remedial Action Program. The DOJ has not yet formally advised the PRPs of the amount that it is seeking, but it is believed to be approximately $90 million . The DOJ and the PRPs agreed to toll the statute of limitations until August 2016 so that settlement discussions could proceed. Based on Generation’s preliminary review, it appears probable that Generation has liability to Cotter under the indemnification agreement and has established an appropriate accrual for this liability. Commencing in February 2012, 36 lawsuits have been filed in the U.S. District Court for the Eastern District of Missouri. Among the defendants were Exelon (subsequently dismissed from the case), Generation and ComEd (the Exelon defendants) and Cotter. The suits allege that individuals living in the North St. Louis area developed some form of cancer due to the Exelon defendants’ negligent or reckless conduct in processing, transporting, storing, handling and/or disposing of radioactive materials. Plaintiffs have asserted claims for negligence, strict liability, emotional distress, medical monitoring, and violations of the Price-Anderson Act. The complaints do not contain specific damage claims. In the event of a finding of liability, it is reasonably possible that Exelon would be considered liable due to its indemnification responsibilities of Cotter described above. The court has dismissed the lawsuits filed by 30 of the plaintiffs. Pre-trial motions and discovery are proceeding in the remaining cases and a proposed pre-trial scheduling order has been filed with the court. At this stage of the litigation, Generation and ComEd cannot estimate a range of loss, if any. 68 th Street Dump. In 1999, the U.S. EPA proposed to add the 68th Street Dump in Baltimore, Maryland to the Superfund National Priorities List, and notified BGE and 19 others that they are PRPs at the site. In March 2004, BGE and other PRPs formed the 68th Street Coalition and entered into consent order negotiations with the U.S. EPA to investigate clean-up options for the site under the Superfund Alternative Sites Program. In May 2006, a settlement among the U.S. EPA and 19 of the PRPs, including BGE, with respect to investigation of the site became effective. The settlement requires the PRPs, over the course of several years, to identify contamination at the site and recommend clean-up options. The PRPs submitted their investigation of the range of clean-up options in the first quarter of 2011. Although the investigation and options provided to the U.S. EPA are still subject to U.S. EPA review and selection of a remedy, the range of estimated clean-up costs to be allocated among all of the PRPs is in the range of $50 million to $64 million . On September 30, 2013, U.S. EPA issued the Record of Decision identifying its preferred remedial alternative for the site. The estimated cost for the alternative chosen by U.S. EPA is consistent with the PRPs estimated range of costs noted above. Based on Generation’s preliminary review, it appears probable that Generation has liability and has established an appropriate accrual for its share of the estimated clean-up costs. A wholly owned subsidiary of Generation has agreed to indemnify BGE for most of the costs related to this settlement and clean-up of the site. Rossville Ash Site. The Rossville Ash Site is a 32-acre property located in Rosedale, Baltimore County, Maryland, which was used for the placement of fly ash from 1983-2007. The property is owned by Constellation Power Source Generation, LLC (CPSG). In 2008, CPSG investigated and remediated the property by entering it into the Maryland Voluntary Cleanup Program (VCP) to address any historic environmental concerns and ready the site for appropriate future redevelopment. The site was accepted into the program in 2010 and is currently going through the process to remediate the site and receive closure from MDE. Exelon currently estimates the cost to close the site to be approximately $9 million , which has been fully reserved as of September 30, 2015 . Sauer Dump. On May 30, 2012, BGE was notified by the U.S. EPA that it is considered a PRP at the Sauer Dump Superfund site in Dundalk, Maryland. The U.S. EPA offered BGE and three other PRPs the opportunity to conduct an environmental investigation and present cleanup recommendations at the site. In addition, the U.S. EPA is seeking recovery from the PRPs of $1.7 million for past cleanup and investigation costs at the site. On March 11, 2013, BGE and three other PRP’s signed an Administrative Settlement Agreement and Order on Consent with the U.S. EPA which requires the PRP’s to conduct a Remedial Investigation and Feasibility Study at the site to determine what, if any, are the appropriate and recommended cleanup activities for the site. The ultimate outcome of this proceeding is uncertain. Since the U.S. EPA has not selected a cleanup remedy and the allocation of the cleanup costs among the PRPs has not been determined, an estimate of the range of BGE’s reasonably possible loss, if any, cannot be determined. Riverside . In 2013, the Maryland Department of the Environment (MDE), at the request of U.S. EPA, conducted a site inspection and limited environmental sampling of certain portions of the 170 acre Riverside property owned by BGE. The site consists of several different parcels with different current and historical uses. The sampling included soil and groundwater samples for a number of potential environmental contaminants. The sampling confirmed the existence of contaminants consistent with the known historical uses of the various portions of the site. In March 2014, the MDE requested that BGE conduct an investigation of three specific areas of the site, and a site-wide investigation of soils, sediment, groundwater, and surface water to complement the MDE sampling. The field investigation was completed in January 2015, and a final report was provided to MDE on June 2, 2015. Upon completion of the investigation the MDE will determine if the site requires further action and/or remediation. Based upon the investigation to date, BGE has established what it believes is an appropriate reserve. As the investigation and potential remediation proceed, it is possible that additional reserves could be established, in amounts that could be material to BGE. Litigation and Regulatory Matters Except to the extent noted below, the circumstances set forth in Note 22 of the Exelon 2014 Form 10-K describe, in all material respects, the current status of litigation matters. The following is an update to that discussion. Asbestos Personal Injury Claims (Exelon, Generation, PECO and BGE) Exelon and Generation . Generation maintains a reserve for claims associated with asbestos-related personal injury actions in certain facilities that are currently owned by Generation or were previously owned by ComEd and PECO. The reserve is recorded on an undiscounted basis and excludes the estimated legal costs associated with ha

Supplemental Financial Informat

Supplemental Financial Information (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Supplemental Financial Information [Abstract]
Additional Financial Information Disclosure [Text Block]	Supplemental Financial Information (Exelon, Generation, ComEd, PECO and BGE) Supplemental Statement of Operations Information The following tables provide additional information about the Registrants’ Consolidated Statements of Operations and Comprehensive Income for the three and nine months ended September 30, 2015 and 2014 : Three Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 39 $ 39 $ — $ — $ — Non-regulatory agreement units 18 18 — — — Net unrealized losses on decommissioning trust funds Regulatory agreement units (301 ) (301 ) — — — Non-regulatory agreement units (218 ) (218 ) — — — Regulatory offset to decommissioning trust fund-related activities (b) 207 207 — — — Total decommissioning-related activities (255 ) (255 ) — — — Investment income (expense) 4 1 — (1 ) 1 (c) Long-term lease income 4 — — — — AFUDC — Equity 6 — 1 1 4 Other (3 ) (3 ) 3 1 (1 ) Other, net $ (244 ) $ (257 ) $ 4 $ 1 $ 4 Nine Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 203 $ 203 $ — $ — $ — Non-regulatory agreement units 122 122 — — — Net unrealized losses on decommissioning trust funds Regulatory agreement units (385 ) (385 ) — — — Non-regulatory agreement units (274 ) (274 ) — — — Net unrealized gains on pledged assets Zion Station decommissioning 9 9 — — — Regulatory offset to decommissioning trust fund-related activities (b) 129 129 — — — Total decommissioning-related activities (196 ) (196 ) — — — Investment income (expense) 6 1 — (1 ) 3 (c) Long-term lease income 12 — — — — Interest income related to uncertain income tax positions — 1 — — — AFUDC — Equity 16 — 2 4 10 Terminated interest rate swaps (d) (26 ) — — — — Other 9 1 12 — — Other, net $ (179 ) $ (193 ) $ 14 $ 3 $ 13 Three Months Ended September 30, 2014 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 55 $ 55 $ — $ — $ — Non-regulatory agreement units 39 39 — — — Net unrealized losses on decommissioning trust funds Regulatory agreement units (107 ) (107 ) — — — Non-regulatory agreement units (41 ) (41 ) — — — Net unrealized gains on pledged assets Zion Station decommissioning 7 7 — — — Regulatory offset to decommissioning trust fund-related activities (b) 29 29 — — — Total decommissioning-related activities (18 ) (18 ) — — — Investment income (expense) — — — — 1 (c) Long-term lease income 4 — — — — Interest income related to uncertain income tax positions 25 27 AFUDC — Equity 5 — — 2 3 Other — (5 ) 4 — — Other, net $ 16 $ 4 $ 4 $ 2 $ 4 Nine Months Ended September 30, 2014 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 167 $ 167 $ — $ — $ — Non-regulatory agreement units 102 102 — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 126 126 — — — Non-regulatory agreement units 100 100 — — — Net unrealized gains on pledged assets Zion Station decommissioning 27 27 — — — Regulatory offset to decommissioning trust fund-related activities (b) (270 ) (270 ) — — — Total decommissioning-related activities 252 252 — — — Investment income (expense) 1 1 — (1 ) 5 (c) Long-term lease income 20 — — — — Interest income related to uncertain income tax positions 41 53 — — — AFUDC — Equity 17 — 3 5 9 Other 15 — 11 1 — Other, net $ 346 $ 306 $ 14 $ 5 $ 14 ________ (a) Includes investment income and realized gains and losses on sales of investments of the trust funds. (b) Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of net income taxes related to all NDT fund activity for those units. See Note 15 — Asset Retirement Obligations of the Exelon 2014 Form 10-K for additional information regarding the accounting for nuclear decommissioning. (c) Relates to the cash return on BGE’s rate stabilization deferral. See Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K for additional information regarding the rate stabilization deferral. (d) In January 2015, in connection with Generation's $750 million issuance of five-year Senior Unsecured Notes, Exelon terminated certain floating-to-fixed interest rate swaps. As the original forecasted transactions were a series of future interest payments over a ten year period, a portion of the anticipated interest payments are probable not to occur. As a result, $26 million of anticipated payments were reclassified from Accumulated OCI to Other, net in Exelon's Consolidated Statement of Operations and Comprehensive Income. Supplemental Cash Flow Information The following tables provide additional information regarding the Registrants’ Consolidated Statements of Cash Flows for the nine months ended September 30, 2015 and 2014 : Nine Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE Depreciation, amortization, accretion and depletion Property, plant and equipment $ 1,648 $ 739 $ 471 $ 179 $ 216 Regulatory assets 131 — 57 19 55 Amortization of intangible assets, net 39 35 — — — Amortization of energy contract assets and liabilities (a) (20 ) (19 ) — — — Nuclear fuel (b) 841 841 — — — ARO accretion (c) 291 291 — — — Total depreciation, amortization, accretion and depletion $ 2,930 $ 1,887 $ 528 $ 198 $ 271 Nine Months Ended September 30, 2014 Exelon Generation ComEd PECO BGE Depreciation, amortization, accretion and depletion Property, plant and equipment $ 1,549 $ 686 $ 438 $ 169 $ 215 Regulatory assets 150 — 83 7 60 Amortization of intangible assets, net 33 33 — — — Amortization of energy contract assets and liabilities (a) 83 93 — — — Nuclear fuel (b) 790 790 — — — ARO accretion (c) 251 251 — — — Total depreciation, amortization, accretion and depletion $ 2,856 $ 1,853 $ 521 $ 176 $ 275 _________ (a) Included in Operating revenues or Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (b) Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (c) Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Nine Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 476 $ 200 $ 155 $ 29 $ 49 Loss from equity method investments 3 4 — — — Provision for uncollectible accounts 114 15 46 37 15 Stock-based compensation costs 102 — — — — Other decommissioning-related activity (a) (31 ) (31 ) — — — Energy-related options (b) 18 18 — — — Amortization of rate stabilization deferral 60 — — — 60 Amortization of debt fair value adjustment (34 ) (9 ) — — — Discrete impacts of EIMA (c) 101 — 101 — — Amortization of debt costs 43 12 3 2 2 Increase in inventory reserve 7 8 — — — Lower of cost or market inventory adjustment 15 15 — — — Other (18 ) (5 ) 7 1 (15 ) Total other non-cash operating activities $ 856 $ 227 $ 312 $ 69 $ 111 Changes in other assets and liabilities: Under/over-recovered energy and transmission costs $ 47 $ — $ 27 $ 12 $ 8 Other regulatory assets and liabilities (12 ) — 29 (4 ) (106 ) Cash deposits (d) (190 ) (190 ) — — — Other current assets (132 ) (143 ) 2 (23 ) (e) 55 Other noncurrent assets and liabilities (193 ) (92 ) (65 ) (3 ) — Total changes in other assets and liabilities $ (480 ) $ (425 ) $ (7 ) $ (18 ) $ (43 ) Non-cash investing and financing activities: Change in PPE related to the ARO update $ 811 $ 811 $ — — $ — $ — Change in capital expenditures not paid 59 (j) 48 (j) 62 (23 ) (14 ) Non-cash financing of capital projects $ 52 $ 52 $ — $ — $ — Indemnification of like-kind exchange position (f) — — 5 — — Long-term software licensing agreement (g) 95 — — — — Nine Months Ended September 30, 2014 Exelon Generation ComEd PECO BGE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 437 $ 193 $ 129 $ 28 $ 50 Equity method investments 20 20 — — — Provision for uncollectible accounts 96 10 9 39 38 Stock-based compensation costs 111 — — — — Other decommissioning-related activity (a) (102 ) (102 ) — — — Energy-related options (b) 92 92 — — — Amortization of regulatory asset related to debt costs 8 — — — — Amortization of rate stabilization deferral 50 — — — 50 Amortization of debt fair value adjustment (45 ) (17 ) — — — Discrete impacts from EIMA (c) (32 ) — (32 ) — — Amortization of debt costs 36 9 4 2 2 Merger-related commitments 44 44 — — — Other (17 ) 2 6 1 (11 ) Total other non-cash operating activities $ 698 $ 251 $ 116 $ 70 $ 129 Changes in other assets and liabilities: Under/over-recovered energy and transmission costs $ 53 $ — $ 63 $ (14 ) $ 6 Other regulatory assets and liabilities (63 ) — (14 ) (14 ) (89 ) Cash deposits (d) (280 ) (280 ) — — — Other current assets (78 ) 24 (9 ) (48 ) (e) 25 Other noncurrent assets and liabilities (168 ) (111 ) 22 1 (9 ) Total changes in other assets and liabilities $ (536 ) $ (367 ) $ 62 $ (75 ) $ (67 ) Non-cash investing and financing activities: Fair value of net assets recorded upon CENG consolidation $ 3,400 $ 3,400 $ — $ — $ — Change in PPE related to the ARO update (91 ) (91 ) Change in capital expenditures not paid (73 ) (j) (100 ) (j) 13 (13 ) 31 Issuance of equity units (h) 131 — — — — Uranium procurement (i) 70 70 — — — Indemnification of like-kind exchange position (f) — — 4 — — ____________ (a) Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 15 — Asset Retirement Obligations of the Exelon 2014 Form 10-K for additional information regarding the accounting for nuclear decommissioning. (b) Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations. (c) Reflects the change in distribution rates pursuant to EIMA, which allows for the recovery of costs by a utility through a pre-established performance-based formula rate tariff. See Note 5 — Regulatory Matters for more information. (d) Relates primarily to cash deposits made to ISOs/RTOs. (e) Relates primarily to prepaid utility taxes. (f) See Note 12 — Income Taxes for discussion of the like-kind exchange tax position. (g) Relates to a long-term software license agreement entered into on May 31, 2015. Exelon is required to make payments starting August of 2015 through May of 2024. See Note 11 — Debt and Credit Agreements for additional information. (h) Relates to the present value of the contract payments for the equity units issued by Exelon. See Note 17 — Common Stock for additional information. (i) Relates to the nuclear fuel procurement contracts for the purchase of fixed quantities of uranium, which was delivered to Generation on June 30, 2014 and September 24, 2014. Generation is required to make payments starting June 30, 2016, with the final payment being due no later than June 30, 2018. (j) Includes $22 million of changes in capital expenditures not paid between December 31, 2014 and September 30, 2015 and $175 million between December 31, 2013 and September 30, 2014 related to Antelope Valley. DOE Smart Grid Investment Grant (Exelon and PECO). For the nine months ended September 30, 2014 , PECO has included in the capital expenditures line item under investing activities of the cash flow statement capital expenditures of $2 million and reimbursements of $5 million related to PECO’s DOE SGIG programs. For the nine months ended September 30, 2015 PECO had no capital expenditures or reimbursements, as the DOE SGIG program was completed during 2014. See Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K for additional information regarding the DOE SGIG. Supplemental Balance Sheet Information The following tables provide additional information about assets of the Registrants as of September 30, 2015 and December 31, 2014 . September 30, 2015 Exelon Generation ComEd PECO BGE Property, plant and equipment: Accumulated depreciation and amortization $ 16,185 (a) $ 8,659 (a) $ 3,614 $ 3,058 $ 2,962 Accounts receivable: Allowance for uncollectible accounts 329 (c) 70 100 98 (c) 61 December 31, 2014 Exelon Generation ComEd PECO BGE Property, plant and equipment: Accumulated depreciation and amortization $ 14,742 (b) $ 7,612 (b) $ 3,432 $ 2,917 $ 2,868 Accounts receivable: Allowance for uncollectible accounts 311 (c) 60 84 100 (c) 67 _______ (a) Includes accumulated amortization of nuclear fuel in the reactor core of $3,093 million . (b) Includes accumulated amortization of nuclear fuel in the reactor core of $2,673 million . (c) Excludes the non-current allowance for uncollectible accounts related to PECO's installment plan receivables described below of $9 million and $7 million at September 30, 2015 and December 31, 2014 , respectively. PECO Installment Plan Receivables (Exelon and PECO) PECO enters into payment agreements with certain delinquent customers, primarily residential, seeking to restore their service, as required by the PAPUC. Customers with past due balances that meet certain income criteria are provided the option to enter into an installment payment plan, some of which have terms greater than one year, to repay past due balances in addition to paying for their ongoing service on a current basis. The receivable balance for these payment agreement receivables is recorded in accounts receivable for the current portion and other deferred debits and other assets for the noncurrent portion. The net receivable balance for installment plans with terms greater than one year was $15 million as of September 30, 2015 and December 31, 2014 each. The allowance for uncollectible accounts reserve methodology and assessment of the credit quality of the installment plan receivables are consistent with the customer accounts receivable methodology discussed in Note 1 — Significant Accounting Policies of the Exelon 2014 Form 10-K. The allowance for uncollectible accounts balance associated with these receivables at September 30, 2015 of $17 million consists of $1 million , $4 million and $12 million for low risk, medium risk and high risk segments, respectively. The allowance for uncollectible accounts balance at December 31, 2014 of $15 million consists of $1 million , $3 million and $11 million for low risk, medium risk and high risk segments, respectively. The balance of the payment agreement is billed to the customer in equal monthly installments over the term of the agreement. Installment receivables outstanding as of September 30, 2015 and December 31, 2014 include balances not yet presented on the customer bill, accounts currently billed and an immaterial amount of past due receivables. When a customer defaults on its payment agreement, the terms of which are defined by plan type, the entire balance of the agreement becomes due and the balance is reclassified to current customer accounts receivable and reserved for in accordance with the methodology discussed in Note 1 — Significant Accounting Policies of the Exelon 2014 Form 10-K.

Segment Information (Exelon, Ge

Segment Information (Exelon, Generation, ComEd, PECO and BGE)	9 Months Ended
	Sep. 30, 2015
Segment Reporting [Abstract]
Segment Information (Exelon, Generation, ComEd, PECO and BGE)	Segment Information (Exelon, Generation, ComEd, PECO and BGE) Operating segments for each of the Registrants are determined based on information used by the chief operating decision maker(s) (CODM) in deciding how to evaluate performance and allocate resources at each of the Registrants. Exelon has nine reportable segments, which include ComEd, PECO, BGE and Generation’s six power marketing reportable segments, consisting of the Mid-Atlantic, Midwest, New England, New York, ERCOT and all other power regions referred to collectively as “Other Power Regions”, which includes activities in the South, West and Canada. ComEd, PECO and BGE each represent a single reportable segment, and as such, no separate segment information is provided for these Registrants. Exelon, ComEd, PECO and BGE's CODMs evaluate the performance of and allocate resources to ComEd, PECO and BGE based on net income and return on equity. The basis for Generation's reportable segments is the integrated management of its electricity business that is located in different geographic regions, and largely representative of the footprints of ISO/RTO and/or NERC regions, which utilize multiple supply sources to provide electricity through various distribution channels (wholesale and retail). Generation's hedging strategies and risk metrics are also aligned to these same geographic regions. Descriptions of each of Generation’s six reportable segments are as follows: • Mid-Atlantic represents operations in the eastern half of PJM, which includes New Jersey, Maryland, Virginia, West Virginia, Delaware, the District of Columbia and parts of Pennsylvania and North Carolina. • Midwest represents operations in the western half of PJM, which includes portions of Illinois, Pennsylvania, Indiana, Ohio, Michigan, Kentucky and Tennessee, and the United States footprint of MISO, excluding MISO’s Southern Region, which covers all or most of North Dakota, South Dakota, Nebraska, Minnesota, Iowa, Wisconsin, the remaining parts of Illinois, Indiana, Michigan and Ohio not covered by PJM, and parts of Montana, Missouri and Kentucky. • New England represents the operations within ISO-NE covering the states of Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont. • New York represents operations within ISO-NY, which covers the state of New York in its entirety. • ERCOT represents operations within Electric Reliability Council of Texas, covering most of the state of Texas. • Other Power Regions : • South represents operations in the FRCC, MISO’s Southern Region, and the remaining portions of the SERC not included within MISO or PJM, which includes all or most of Florida, Arkansas, Louisiana, Mississippi, Alabama, Georgia, Tennessee, North Carolina, South Carolina and parts of Missouri, Kentucky and Texas. Generation’s South region also includes operations in the SPP, covering Kansas, Oklahoma, most of Nebraska and parts of New Mexico, Texas, Louisiana, Missouri, Mississippi and Arkansas. • West represents operations in the WECC, which includes California ISO, and covers the states of California, Oregon, Washington, Arizona, Nevada, Utah, Idaho, Colorado, and parts of New Mexico, Wyoming and South Dakota. • Canada represents operations across the entire country of Canada and includes AESO, OIESO and the Canadian portion of MISO. The CODMs for Exelon and Generation evaluate the performance of Generation’s power marketing activities and allocate resources based on revenue net of purchased power and fuel expense (RNF). Generation believes that RNF is a useful measurement of operational performance. RNF is not a presentation defined under GAAP and may not be comparable to other companies’ presentations or deemed more useful than the GAAP information provided elsewhere in this report. Generation’s operating revenues include all sales to third parties and affiliated sales to ComEd, PECO, and BGE. Purchased power costs include all costs associated with the procurement and supply of electricity including capacity, energy and ancillary services. Fuel expense includes the fuel costs for Generation’s owned generation and fuel costs associated with tolling agreements. The results of Generation's other business activities are not regularly reviewed by the CODM and are therefore not classified as operating segments or included in the regional reportable segment amounts. These activities include natural gas, as well as other miscellaneous business activities that are not significant to Generation's overall operating revenues or results of operations. Further, Generation’s unrealized mark-to-market gains and losses on economic hedging activities and its amortization of certain intangible assets and liabilities relating to commodity contracts recorded at fair value from mergers and acquisitions are also not included in the regional reportable segment amounts. Exelon and Generation do not use a measure of total assets in making decisions regarding allocating resources to or assessing the performance of these reportable segments. An analysis and reconciliation of the Registrants’ reportable segment information to the respective information in the consolidated financial statements is as follows: Three Months Ended September 30, 2015 and 2014 Generation (a) ComEd PECO BGE Other (b) Intersegment Eliminations Exelon Total revenues (c) : 2015 $ 4,768 $ 1,376 $ 740 $ 725 $ 348 $ (556 ) $ 7,401 2014 4,412 1,222 693 697 305 (417 ) 6,912 Intersegment revenues (d) : 2015 $ 205 $ 1 $ 1 $ 3 $ 347 $ (555 ) $ 2 2014 112 1 — 3 302 (418 ) — Net income (loss): 2015 $ 332 $ 149 $ 90 $ 54 $ (36 ) $ (2 ) $ 587 2014 849 126 81 49 (31 ) — 1,074 Total assets: September 30, 2015 $ 46,479 $ 26,129 $ 10,072 $ 8,134 $ 16,256 $ (11,942 ) $ 95,128 December 31, 2014 45,348 25,392 9,943 8,078 9,794 (11,741 ) 86,814 __________ (a) Generation includes the six power marketing reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. Intersegment revenues for Generation for the three months ended September 30, 2015 include revenue from sales to PECO of $61 million and sales to BGE of $141 million in the Mid-Atlantic region, and sales to ComEd of $2 million in the Midwest. For the three months ended September 30, 2014 , intersegment revenues for Generation include revenue from sales to PECO of $28 million and sales to BGE of $83 million in the Mid-Atlantic region, and sales to ComEd of $1 million in the Midwest region. (b) Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities. (c) For the three months ended September 30, 2015 and 2014 , utility taxes of $28 million and $22 million , respectively, are included in revenues and expenses for Generation. For the three months ended September 30, 2015 and 2014 , utility taxes of $63 million and $61 million , respectively, are included in revenues and expenses for ComEd. For the three months ended September 30, 2015 and 2014 , utility taxes of $37 million and $34 million , respectively, are included in revenues and expenses for PECO. For the three months ended September 30, 2015 and 2014 , utility taxes of $23 million and $21 million , respectively, are included in revenues and expenses for BGE. (d) Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income. Generation total revenues: Three Months Ended September 30, 2015 Three Months Ended September 30, 2014 Revenues from External Customers (a) Intersegment Revenues Total Revenues Revenues from External Customers (a) Intersegment Revenues Total Revenues Mid-Atlantic $ 1,622 $ 10 $ 1,632 $ 1,285 $ 4 $ 1,289 Midwest 1,150 1 1,151 1,062 (1 ) 1,061 New England 519 1 520 272 — 272 New York 254 (4 ) 250 230 2 232 ERCOT 317 (1 ) 316 303 (1 ) 302 Other Power Regions (b) 383 (7 ) 376 381 (6 ) 375 Total Revenues for Reportable Segments 4,245 — 4,245 3,533 (2 ) 3,531 Other (c) 523 — 523 879 2 881 Total Generation Consolidated Operating Revenues $ 4,768 $ — $ 4,768 $ 4,412 $ — $ 4,412 __________ (a) Includes all electric sales to third parties and affiliated sales to ComEd, PECO and BGE. (b) Other Power Regions includes the South, West and Canada. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $3 million decrease to revenues and a $22 million decrease to revenues for the amortization of intangible assets related to commodity contracts for the three months ended September 30, 2015 and 2014 , respectively, unrealized mark-to-market losses of $7 million and gains of $271 million for the three months ended September 30, 2015 and 2014 , respectively, and the elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Three Months Ended September 30, 2015 Three Months Ended September 30, 2014 RNF (a) Intersegment RNF Total RNF RNF (a) Intersegment RNF Total RNF Mid-Atlantic $ 974 $ 17 $ 991 $ 921 $ 14 $ 935 Midwest 752 — 752 722 (6 ) 716 New England 145 (12 ) 133 120 (30 ) 90 New York 159 8 167 176 10 186 ERCOT 166 (55 ) 111 186 (77 ) 109 Other Power Regions (b) 167 (84 ) 83 157 (89 ) 68 Total Revenues net of purchased power and fuel for Reportable Segments 2,363 (126 ) 2,237 2,282 (178 ) 2,104 Other (c) (114 ) 126 12 250 178 428 Total Generation Revenues net of purchased power and fuel expense $ 2,249 $ — $ 2,249 $ 2,532 $ — $ 2,532 __________ (a) Includes purchases and sales from third parties and affiliated sales to ComEd, PECO and BGE. (b) Other Power Regions includes the South, West and Canada. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $4 million decrease to RNF and a $15 million increase to RNF for the amortization of intangible assets related to commodity contracts for the three months ended September 30, 2015 and 2014 , respectively, unrealized mark-to-market losses of $139 million and gains of $267 million for the three months ended September 30, 2015 and 2014 , respectively, and the elimination of intersegment revenues. Nine Months Ended September 30, 2015 and 2014 Generation (a) ComEd PECO BGE Other (b) Intersegment Eliminations Exelon Total revenues (c) : 2015 $ 14,841 $ 3,709 $ 2,386 $ 2,388 $ 1,007 $ (1,585 ) $ 22,746 2014 12,591 3,484 2,343 2,404 924 (1,573 ) 20,173 Intersegment revenues (d) : 2015 $ 567 $ 3 $ 1 $ 10 $ 1,003 $ (1,581 ) $ 3 2014 630 2 1 21 920 (1,574 ) — Net income (loss): 2015 $ 1,208 $ 339 $ 299 $ 212 $ (96 ) $ (3 ) $ 1,959 2014 1,037 335 255 156 (58 ) — 1,725 __________ (a) Generation includes the six power marketing reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. Intersegment revenues for Generation for the nine months ended September 30, 2015 include revenue from sales to PECO of $ 173 million and sales to BGE of $ 376 million in the Mid-Atlantic region, and sales to ComEd of $ 17 million in the Midwest. For the nine months ended September 30, 2014 , intersegment revenues for Generation include revenue from sales to PECO of $ 165 million and sales to BGE of $ 290 million in the Mid-Atlantic region, and sales to ComEd of $ 175 million in the Midwest region. (b) Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities. (c) For the nine months ended September 30, 2015 and 2014 , utility taxes of $ 79 million and $ 67 million , respectively, are included in revenues and expenses for Generation. For the nine months ended September 30, 2015 and 2014 , utility taxes of $ 180 million and $ 180 million , respectively, are included in revenues and expenses for ComEd. For the nine months ended September 30, 2015 and 2014 , utility taxes of $ 104 million and $ 99 million , respectively, are included in revenues and expenses for PECO. For the nine months ended September 30, 2015 and 2014 , utility taxes of $ 67 million and $ 64 million , respectively, are included in revenues and expenses for BGE. (d) Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income. Generation total revenues: Nine Months Ended September 30, 2015 Nine Months Ended September 30, 2014 Revenues (b) Intersegment Total Revenues (b) Intersegment Total Mid-Atlantic (a) $ 4,475 $ 16 $ 4,491 $ 3,998 $ (14 ) $ 3,984 Midwest 3,630 3 3,633 3,302 11 3,313 New England 1,743 3 1,746 1,028 5 1,033 New York (a) 786 (8 ) 778 614 (1 ) 613 ERCOT 691 (4 ) 687 743 (2 ) 741 Other Power Regions (c) 891 (11 ) 880 1,027 (4 ) 1,023 Total Revenues for Reportable Segments 12,216 (1 ) 12,215 10,712 (5 ) 10,707 Other (d) 2,625 1 2,626 1,879 5 1,884 Total Generation Consolidated Operating Revenues $ 14,841 $ — $ 14,841 $ 12,591 $ — $ 12,591 __________ (a) On April 1, 2014, Generation assumed operational control of CENG's nuclear fleet. As a result, beginning on April 1, 2014, CENG's revenues are included on a fully consolidated basis. (b) Includes all wholesale and retail electric sales to third parties and affiliated sales to ComEd, PECO and BGE. (c) Other Power Regions includes the South, West and Canada. (d) Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $19 million increase to revenues and a $203 million decrease to revenues for the amortization of intangible assets related to commodity contracts for the nine months ended September 30, 2015 and 2014 , respectively, unrealized mark-to-market gains of $171 million and losses of $572 million for the nine months ended September 30, 2015 and 2014 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Nine Months Ended September 30, 2015 Nine Months Ended September 30, 2014 RNF from External Customers (b) Intersegment RNF Total RNF RNF from External Customers (b) Intersegment RNF Total RNF Mid-Atlantic (a) $ 2,633 $ 30 $ 2,663 $ 2,610 $ (60 ) $ 2,550 Midwest 2,198 (3 ) 2,195 1,856 21 1,877 New England 416 (37 ) 379 362 (72 ) 290 New York (a) 471 27 498 289 24 313 ERCOT 344 (109 ) 235 457 (207 ) 250 Other Power Regions (c) 403 (210 ) 193 465 (216 ) 249 Total Revenues net of purchased power and fuel expense for Reportable Segments 6,465 — (302 ) 6,163 6,039 (510 ) 5,529 Other (d) 576 302 878 (519 ) 510 (9 ) Total Generation Revenues net of purchased power and fuel expense $ 7,041 — $ — $ 7,041 $ 5,520 $ — $ 5,520 __________ (a) On April 1, 2014, Generation assumed operational control of CENG's nuclear fleet. As a result, starting on April 1, 2014, CENG's revenue net of purchased power and fuel expense are included on a fully consolidated basis. (b) Includes purchases and sales from third parties and affiliated sales to ComEd, PECO and BGE. (c) Other Power Regions includes the South, West and Canada. (d) Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $20 million increase to RNF and a $78 million decrease to RNF for the amortization of intangible assets related to commodity contracts for the nine months ended September 30, 2015 and 2014 , respectively, unrealized mark-to-market gains of $258 million and losses of $477 million for the nine months ended September 30, 2015 and 2014 , respectively, and the elimination of intersegment revenue net of purchased power and fuel expense.

Accounting Policy (Policies)

Accounting Policy (Policies)	9 Months Ended
	Sep. 30, 2015
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Fair Value of Financial Instruments, Policy [Policy Text Block]	Recurring Fair Value Measurements Exelon records the fair value of assets and liabilities in accordance with the hierarchy established by the authoritative guidance for fair value measurements. The hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three levels as follows: • Level 1 — quoted prices (unadjusted) in active markets for identical assets or liabilities that the Registrants have the ability to liquidate as of the reporting date. • Level 2 — inputs other than quoted prices included within Level 1 that are directly observable for the asset or liability or indirectly observable through corroboration with observable market data. • Level 3 — unobservable inputs, such as internally developed pricing models or third-party valuations for the asset or liability due to little or no market activity for the asset or liability. Transfers in and out of levels are recognized as of the end of the reporting period when the transfer occurred. Given derivatives categorized within Level 1 are valued using exchange-based quoted prices within observable periods, transfers between Level 2 and Level 1 were not material. Transfers into Level 2 from Level 3 generally occur when the contract tenure becomes more observable. Transfers into Level 3 from Level 2 generally occur due to changes in market liquidity or assumptions for certain commodity contracts. There were no transfers between Level 1 and Level 2 during the nine months ended September 30, 2015 for cash equivalents, nuclear decommissioning trust fund investments, pledged assets for Zion Station decommissioning, Rabbi trust investments, and deferred compensation obligations.
FairValueMeasurementsValuationTechniques policy [Policy Text Block]	Valuation Techniques Used to Determine Fair Value The following describes the valuation techniques used to measure the fair value of the assets and liabilities shown in the tables above. Cash Equivalents (Exelon, Generation, ComEd, PECO and BGE). The Registrants’ cash equivalents include investments with maturities of three months or less when purchased. The cash equivalents shown in the fair value tables are comprised of investments in mutual and money market funds. The fair values of the shares of these funds are based on observable market prices and, therefore, have been categorized in Level 1 in the fair value hierarchy. Nuclear Decommissioning Trust Fund Investments and Pledged Assets for Zion Station Decommissioning (Exelon and Generation). The trust fund investments have been established to satisfy Generation’s and CENG's nuclear decommissioning obligations as required by the NRC. The NDT funds hold debt and equity securities directly and indirectly through commingled funds and mutual funds, which are included in Equities, Fixed Income and Other. Generation’s and CENG's NDT fund investments policies outline investment guidelines for the trusts and limit the trust funds’ exposures to investments in highly illiquid markets and other alternative investments. Investments with maturities of three months or less when purchased, including certain short-term fixed income securities are considered cash equivalents and included in the recurring fair value measurements hierarchy as Level 1 or Level 2. With respect to individually held equity securities, which are included in Domestic or Foreign equities, the trustees obtain prices from pricing services, whose prices are obtained from direct feeds from market exchanges, which Generation is able to independently corroborate. The fair values of equity securities held directly by the trust funds are based on quoted prices in active markets and are categorized in Level 1. Equity securities held individually are primarily traded on the New York Stock Exchange and NASDAQ-Global Select Market, which contain only actively traded securities due to the volume trading requirements imposed by these exchanges. For fixed income securities, multiple prices from pricing services are obtained whenever possible, which enables cross-provider validations in addition to checks for unusual daily movements. A primary price source is identified based on asset type, class or issue for each security. The trustees monitor prices supplied by pricing services and may use a supplemental price source or change the primary price source of a given security if the portfolio managers challenge an assigned price and the trustees determine that another price source is considered to be preferable. Generation has obtained an understanding of how these prices are derived, including the nature and observability of the inputs used in deriving such prices. Additionally, Generation selectively corroborates the fair values of securities by comparison to other market-based price sources. U.S. Treasury securities are categorized as Level 1 because they trade in a highly liquid and transparent market. The fair values of fixed income securities, excluding U.S. Treasury securities, are based on evaluated prices that reflect observable market information, such as actual trade information or similar securities, adjusted for observable differences and are categorized in Level 2. The fair values of private placement fixed income securities, which are included in Corporate debt, are determined using a third party valuation that contains significant unobservable inputs and are categorized in Level 3. Equity, balanced and fixed income commingled funds and fixed income mutual funds are maintained by investment companies and hold certain investments in accordance with a stated set of fund objectives. The fair values of fixed income commingled and mutual funds held within the trust funds, which generally hold fixed income securities and are not subject to restrictions regarding the purchase or sale of shares, are derived from observable prices. The objectives of the remaining equity commingled funds in which Exelon, Generation, and CENG invest primarily seek to track the performance of certain equity indices by purchasing equity securities to replicate the capitalization and characteristics of the indices. Commingled and mutual funds are categorized in Level 2 because the fair value of the funds are based on NAVs per fund share (the unit of account), primarily derived from the quoted prices in active markets on the underlying equity securities. Middle market lending are investments in loans or managed funds which lend to private companies. Generation elected the fair value option for its investments in certain limited partnerships that invest in middle market lending managed funds. The fair value of these loans is determined using a combination of valuation models including cost models, market models, and income models. Investments in middle market lending are categorized as Level 3 because the fair value of these securities is based largely on inputs that are unobservable and utilize complex valuation models. Investments in middle market lending typically cannot be redeemed until maturity of the term loan. Private equity investments include investments in operating companies that are not publicly traded on a stock exchange. Private equity valuations are reported by the fund manager and are based on the valuation of the underlying investments, which include inputs such as cost, operating results, discounted future cash flows and market based comparable data. Since these valuation inputs are not highly observable, private equity investments have been categorized as Level 3. As of September 30, 2015 , Generation has outstanding commitments to invest in middle market lending, corporate debt securities, private equity investments, and real estate investments of approximately $286 million . These commitments will be funded by Generation’s existing nuclear decommissioning trust funds. See Note 12—Nuclear Decommissioning for further discussion on the NDT fund investments. Rabbi Trust Investments (Exelon, Generation, ComEd, PECO and BGE). The Rabbi trusts were established to hold assets related to deferred compensation plans existing for certain active and retired members of Exelon’s executive management and directors. The Rabbi trusts assets are included in investments in the Registrants’ Consolidated Balance Sheets and consist primarily of mutual funds and life insurance policies. The mutual funds are maintained by investment companies and hold certain investments in accordance with a stated set of fund objectives, which are consistent with Exelon’s overall investment strategy. Mutual funds are publicly quoted and have been categorized as Level 1 given the clear observability of the prices. The life insurance policies are valued using the cash surrender value of the policies, which is provided by a third party. The cash surrender value inputs are not observable. Mark-to-Market Derivatives (Exelon, Generation, and ComEd) . Derivative contracts are traded in both exchange-based and non-exchange-based markets. Exchange-based derivatives that are valued using unadjusted quoted prices in active markets are categorized in Level 1 in the fair value hierarchy. Certain derivatives’ pricing is verified using indicative price quotations available through brokers or over-the-counter, on-line exchanges and are categorized in Level 2. These price quotations reflect the average of the bid-ask, mid-point prices and are obtained from sources that the Registrants believe provide the most liquid market for the commodity. The price quotations are reviewed and corroborated to ensure the prices are observable and representative of an orderly transaction between market participants. This includes consideration of actual transaction volumes, market delivery points, bid-ask spreads and contract duration. The remainder of derivative contracts are valued using the Black model, an industry standard option valuation model. The Black model takes into account inputs such as contract terms, including maturity, and market parameters, including assumptions of the future prices of energy, interest rates, volatility, credit worthiness and credit spread. For derivatives that trade in liquid markets, such as generic forwards, swaps and options, model inputs are generally observable. Such instruments are categorized in Level 2. The Registrants’ derivatives are predominately at liquid trading points. For derivatives that trade in less liquid markets with limited pricing information model inputs generally would include both observable and unobservable inputs. These valuations may include an estimated basis adjustment from an illiquid trading point to a liquid trading point for which active price quotations are available. Such instruments are categorized in Level 3. Exelon may utilize fixed-to-floating interest rate swaps, which are typically designated as fair value hedges, as a means to achieve its targeted level of variable-rate debt as a percent of total debt. In addition, the Registrants may utilize interest rate derivatives to lock in interest rate levels in anticipation of future financings. These interest rate derivatives are typically designated as cash flow hedges. Exelon determines the current fair value by calculating the net present value of expected payments and receipts under the swap agreement, based on and discounted by the market's expectation of future interest rates. Additional inputs to the net present value calculation may include the contract terms, counterparty credit risk and other market parameters. As these inputs are based on observable data and valuations of similar instruments, the interest rate swaps are categorized in Level 2 in the fair value hierarchy. See Note 10 - Derivative Financial Instruments for further discussion on mark-to-market derivatives. Deferred Compensation Obligations (Exelon, Generation, ComEd, PECO and BGE). The Registrants’ deferred compensation plans allow participants to defer certain cash compensation into a notional investment account. The Registrants include such plans in other current and noncurrent liabilities in their Consolidated Balance Sheets. The value of the Registrants’ deferred compensation obligations is based on the market value of the participants’ notional investment accounts. The underlying notional investments are comprised primarily of equities, mutual funds, commingled funds, and fixed income securities which are based on directly and indirectly observable market prices. Since the deferred compensation obligations themselves are not exchanged in an active market, they are categorized as Level 2 in the fair value hierarchy. Additional Information Regarding Level 3 Fair Value Measurements (Exelon, Generation, ComEd) Mark-to-Market Derivatives (Exelon, Generation, ComEd). For valuations that include both observable and unobservable inputs, if the unobservable input is determined to be significant to the overall inputs, the entire valuation is categorized in Level 3. This includes derivatives valued using indicative price quotations whose contract tenure extends into unobservable periods. In instances where observable data is unavailable, consideration is given to the assumptions that market participants would use in valuing the asset or liability. This includes assumptions about market risks such as liquidity, volatility and contract duration. Such instruments are categorized in Level 3 as the model inputs generally are not observable. Exelon’s RMC approves risk management policies and objectives for risk assessment, control and valuation, counterparty credit approval, and the monitoring and reporting of risk exposures. The RMC is chaired by the chief executive officer and includes the chief risk officer, chief strategy officer, chief executive officer of Exelon Utilities, chief commercial officer, chief financial officer and chief executive officer of Constellation. The RMC reports to the Finance and Risk Committee of the Exelon Board of Directors on the scope of the risk management activities. Forward price curves for the power market utilized by the front office to manage the portfolio, are reviewed and verified by the middle office, and used for financial reporting by the back office. The Registrants consider credit and nonperformance risk in the valuation of derivative contracts categorized in Level 2 and 3, including both historical and current market data in its assessment of credit and nonperformance risk by counterparty. Due to master netting agreements and collateral posting requirements, the impacts of credit and nonperformance risk were not material to the financial statements. Disclosed below is detail surrounding the Registrants’ significant Level 3 valuations. The calculated fair value includes marketability discounts for margining provisions and other attributes. Generation’s Level 3 balance generally consists of forward sales and purchases of power and natural gas, coal purchases and certain transmission congestion contracts. Generation utilizes various inputs and factors including market data and assumptions that market participants would use in pricing assets or liabilities as well as assumptions about the risks inherent in the inputs to the valuation technique. The inputs and factors include forward commodity prices, commodity price volatility, contractual volumes, delivery location, interest rates, credit quality of counterparties and credit enhancements. For commodity derivatives, the primary input to the valuation models is the forward commodity price curve for each instrument. Forward commodity price curves are derived by risk management for liquid locations and by the traders and portfolio managers for illiquid locations. All locations are reviewed and verified by risk management considering published exchange transaction prices, executed bilateral transactions, broker quotes, and other observable or public data sources. The relevant forward commodity curve used to value each of the derivatives depends on a number of factors, including commodity type, delivery location, and delivery period. Price volatility varies by commodity and location. When appropriate, Generation discounts future cash flows using risk free interest rates with adjustments to reflect the credit quality of each counterparty for assets and Generation’s own credit quality for liabilities. The level of observability of a forward commodity price varies generally due to the delivery location and delivery period. Certain delivery locations including PJM West Hub (for power) and Henry Hub (for natural gas) are more liquid and prices are observable for up to three years in the future. The observability period of volatility is generally shorter than the underlying power curve used in option valuations. The forward curve for a less liquid location is estimated by using the forward curve from the liquid location and applying a spread to represent the cost to transport the commodity to the delivery location. This spread does not typically represent a majority of the instrument’s market price. As a result, the change in fair value is closely tied to liquid market movements and not a change in the applied spread. The change in fair value associated with a change in the spread is generally immaterial. An average spread calculated across all Level 3 power and gas delivery locations is approximately $3.30 and $0.32 for power and natural gas, respectively. Many of the commodity derivatives are short term in nature and thus a majority of the fair value may be based on observable inputs even though the contract as a whole must be classified as Level 3. See ITEM 3. — QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK for information regarding the maturity by year of the Registrant’s mark-to-market derivative assets and liabilities.
Description of New Accounting Pronouncements Not yet Adopted [Text Block]	New Accounting Pronouncements (Exelon, Generation, ComEd, PECO and BGE) The following recently issued accounting standard was effective for the Registrants during 2015. Application of Normal Purchases Normal Sales Exception to Power Contracts in Nodal Energy Markets In August 2015, the FASB issued authoritative guidance addressing the ability of entities to elect the normal purchase normal sales (NPNS) scope exception when the contract for the purchase or sale of electricity on a forward basis is delivered to a nodal energy market or transmitted through a nodal energy market. The NPNS scope exception allows entities to treat certain contracts that qualify as derivatives as contracts that do not require recognition at fair value. The guidance specifies that the use of locational marginal pricing by an independent system operator in such transactions does not constitute net settlement of a contract for the purchase or sale of electricity, even in scenarios in which legal title to the associated electricity is conveyed to the independent system operator during transmission. Consequently, the use of locational marginal pricing by the independent system operator does not cause that contract to fail to meet the physical delivery criterion of the NPNS scope exception. If the physical delivery criterion is met, along with all of the other criteria of the NPNS scope exception, an entity may elect to designate that contract as NPNS. The guidance is effective upon issuance and should be applied prospectively. The adoption of this guidance had no impact on the Registrants’ financial positions, results of operations, cash flows and disclosures. The following recently issued accounting standards are not yet required to be reflected in the combined financial statements of the Registrants. Simplifying the Accounting for Measurement-Period Adjustments In September 2015, the FASB issued authoritative guidance that requires an acquirer in a business combination to recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined and to record, in the same period’s financial statements, the effect on earnings of changes in depreciation, amortization, or other income effects, if any, as a result of the change to the provisional amounts, calculated as if the accounting had been completed at the acquisition date . The guidance is effective for periods beginning after December 15, 2015. The guidance is required to be applied prospectively to adjustments to provisional amounts that occur after the effective date with earlier application permitted for financial statements that have not been issued. The Registrants expect to early adopt the standard in the fourth quarter of 2015. The adoption of this guidance will have no impact on the Registrants’ financial positions, results of operations, cash flows and disclosures. Simplifying the Measurement of Inventory In July 2015, the FASB issued authoritative guidance that requires inventory to be measured at the lower of cost or net realizable value. The new guidance defines net realizable value as the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal and transportation. This definition is consistent with existing authoritative guidance. Current guidance requires inventory to be measured at the lower of cost or market where market could be replacement cost, net realizable value or net realizable value less an approximately normal profit margin. The guidance is effective for periods beginning after December 15, 2016 with early adoption permitted. The guidance is required to be applied prospectively. The Registrants are currently assessing the impacts this guidance may have on their financial positions, results of operations, cash flows and disclosures as well as the potential to early adopt the guidance. Disclosures for Investments in Certain Entities that Calculate Net Asset Value per Share In May 2015, FASB issued authoritative guidance that removes the requirement to categorize within the fair value hierarchy all investments for which fair value is measured using the net asset value per share practical expedient. Investments measured at net asset value per share using the practical expedient will be presented as a reconciling item between the fair value hierarchy disclosure and the investment line item on the statement of financial position. The guidance also removes the requirement to make certain disclosures for all investments that are eligible to be measured at fair value using the net asset value per share practical expedient. Rather, those disclosures are limited to investments for which the entity has elected to measure the fair value using the practical expedient. The guidance is effective for the Registrants for fiscal years beginning after December 15, 2015 with early adoption permitted. The guidance is required to be applied retrospectively to all prior periods presented. The Registrants are currently assessing the impacts this guidance may have on their disclosures as well as the potential to early adopt the guidance. There will be no impact to their financial position, results of operations or cash flows. Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement In April 2015, the FASB issued authoritative guidance that clarifies the circumstances under which a cloud computing customer would account for the arrangement as a license of internal-use software. A cloud computing arrangement would include a software license if (1) the customer has a contractual right to take possession of the software at any time during the hosting period without significant penalty and (2) it is feasible for the customer to either run the software on its own hardware or contract with another party unrelated to the vendor to host the software. If the arrangement does not contain a software license, it would be accounted for as a service contract. The guidance is effective for the Registrants for fiscal years beginning after December 15, 2015. Early adoption is permitted. The guidance can be applied retrospectively to each prior reporting period presented or prospectively to arrangements entered into, or materially modified, after the effective date. The Registrants do not expect that this guidance will have a significant impact on their financial positions, results of operations, cash flows and disclosures. The Registrants expect to apply the standard prospectively to arrangements entered into, or materially modified, after the standard becomes effective for the Registrants on January 1, 2016. The Registrants do not plan to early adopt the standard. Simplifying the Presentation of Debt Issuance Costs In April 2015, the FASB issued authoritative guidance that changes the presentation of debt issuance costs in financial statements. The new guidance requires entities to present such costs in the balance sheet as a direct reduction to the related debt liability rather than as a deferred cost (i.e., an asset) as required by current guidance. The new standard does not change the recognition or measurement of debt issuance costs. The guidance is effective for the Registrants for fiscal years beginning after December 15, 2015. Early adoption is permitted for financial statements that have not been previously issued. The guidance is required to be applied retrospectively to all prior periods presented. The Registrants are currently assessing the impact this guidance may have on their financial positions and disclosures. The standard will not impact the results of operations and cash flows of the Registrants. The Registrants expect to complete their assessment by the fourth quarter of 2015 and early adopt the standard at that time. In August 2015, the FASB issued clarifying authoritative guidance for debt issuance costs incurred in connection with line-of-credit arrangements as such costs were not addressed within the guidance simplifying the presentation of debt issuance costs issued in April 2015. The guidance clarifies that an entity can defer and present debt issuance costs as an asset and subsequently amortize the deferred debt issuance costs ratably over the term of the line-of-credit arrangement. The adoption of this guidance will have no impact on the Registrants’ financial positions, results of operations, cash flows and disclosures . Amendments to the Consolidation Analysis In February 2015, the FASB issued authoritative guidance that amends the consolidation analysis for variable interest entities (VIEs) as well as voting interest entities. The new guidance primarily (1) changes the assessment of limited partnerships as VIEs, (2) amends the effect that fees paid to a decision maker or service provider have on the VIE analysis, (3) amends how variable interests held by a reporting entity’s related parties and de facto agents impact its consolidation conclusion, (4) clarifies how to determine whether equity holders (as a group) have power over an entity and (5) provides a scope exception for registered and similar unregistered money market funds. The guidance is effective for the Registrants for the first interim period beginning on or after December 15, 2015. Early adoption is permitted. The guidance can be applied retrospectively to each prior reporting period presented (full retrospective method) or retrospectively with a cumulative effect adjustment to retained earnings for initial application of the guidance at the date of adoption (modified retrospective method). The Registrants are currently assessing the impact this guidance may have on their financial positions, results of operations, cash flows and disclosures as well as the transition method that they will use to adopt the guidance. The Registrants do not plan to early adopt the standard. Revenue from Contracts with Customers In May 2014, the FASB issued authoritative guidance that changes the criteria for recognizing revenue from a contract with a customer. The new guidance replaces existing guidance on revenue recognition, including most industry specific guidance, with a five step model for recognizing and measuring revenue from contracts with customers. The objective of the new standard is to provide a single, comprehensive revenue recognition model for all contracts with customers to improve comparability within industries, across industries and across capital markets. The underlying principle is that an entity will recognize revenue to depict the transfer of goods or services to customers at an amount that the entity expects to be entitled to in exchange for those goods or services. The guidance also requires a number of disclosures regarding the nature, amount, timing and uncertainty of revenue and the related cash flows. The guidance can be applied retrospectively to each prior reporting period presented (full retrospective method) or retrospectively with a cumulative effect adjustment to retained earnings for initial application of the guidance at the date of initial adoption (modified retrospective method). The Registrants are currently assessing the impacts this guidance may have on their financial positions, results of operations, cash flows and disclosures as well as the transition method that they will use to adopt the guidance. In August 2015, the FASB issued an amendment to provide a one year deferral of the effective date to annual reporting periods beginning on or after December 15, 2017, as well as an option to early adopt the standard for annual periods beginning on or after December 15, 2016. The Registrants do not plan to early adopt the standard.

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
	Sep. 30, 2015
Variable Interest Entity [Abstract]
Schedule of Variable Interest Entities	September 30, 2015 December 31, 2014 Exelon Generation BGE Exelon Generation BGE Cash and cash equivalents $ 330 $ 330 $ — $ 392 $ 392 $ — Restricted cash 193 146 46 117 96 21 Accounts receivable, net Customer 186 186 — 297 297 — Other 32 32 — 57 57 — Mark-to-market derivatives assets 116 116 — 171 171 — Inventory Materials and supplies 180 180 — 172 172 — Other current assets 48 43 — 33 26 — Total current assets 1,085 1,033 46 1,239 1,211 21 Property, plant and equipment, net 4,932 4,932 — 4,638 4,638 — Nuclear decommissioning trust funds 1,973 1,973 — 2,097 2,097 — Goodwill 47 47 — 47 47 — Mark-to-market derivatives assets 53 53 — 44 44 — Other noncurrent assets 100 92 3 95 82 3 Total noncurrent assets 7,105 7,097 3 6,921 6,908 3 Total assets $ 8,190 $ 8,130 $ 49 $ 8,160 $ 8,119 $ 24 Long-term debt due within one year $ 108 $ 26 $ 77 $ 87 $ 5 $ 75 Accounts payable 266 266 — 292 292 — Accrued expenses 92 88 4 111 108 2 Mark-to-market derivative liabilities — — — 24 24 — Unamortized energy contract liabilities 10 10 — 22 22 — Other current liabilities 15 15 — 25 25 — Total current liabilities 491 405 81 561 476 77 Long-term debt 729 643 81 212 81 120 Asset retirement obligations 1,906 1,906 — 1,763 1,763 — Pension obligation (a) 9 9 — 9 9 — Unamortized energy contract liabilities 42 42 — 51 51 — Other noncurrent liabilities 65 65 — 127 127 — Noncurrent liabilities 2,751 2,665 81 2,162 2,031 120 Total liabilities $ 3,242 $ 3,070 $ 162 $ 2,723 $ 2,507 $ 197 ______________ (a) Includes CNEG retail gas pension obligation, which is presented as a net asset balance within the Prepaid Pension asset line item on Generation’s balance sheet. See Note 14 — Retirement Benefits for additional details. The following tables present summary information about Exelon and Generation’s significant unconsolidated VIE entities: September 30, 2015 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 253 $ 131 $ 384 Total liabilities (a) 10 66 76 Exelon's ownership interest in VIE (a) — 19 19 Other ownership interests in VIE (a) 243 46 289 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 27 27 Contract intangible asset 9 — 9 Debt and payment guarantees — 3 3 Net assets pledged for Zion Station decommissioning (b) 20 — 20 December 31, 2014 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 114 $ 91 $ 205 Total liabilities (a) 3 49 52 Exelon's ownership interest in VIE (a) — 9 9 Other ownership interests in VIE (a) 111 33 144 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 13 13 Contract intangible asset 9 — 9 Debt and payment guarantees — 3 3 Net assets pledged for Zion Station decommissioning (b) 27 — 27 ___________________ (a) These items represent amounts on the unconsolidated VIE balance sheets, not on Exelon’s or Generation’s Consolidated Balance Sheets. These items are included to provide information regarding the relative size of the unconsolidated VIEs. Exelon corrected an error in the December 31, 2014 balances within Commercial Agreement VIEs for an overstatement of Total assets, Total liabilities and Other ownership interests in VIE of $392 million , $234 million and $158 million , respectively. The error is not considered material to any prior period. (b) These items represent amounts on Exelon’s and Generation’s Consolidated Balance Sheets related to the asset sale agreement with ZionSolutions, LLC. The net assets pledged for Zion Station decommissioning include, gross pledged assets of $237 million and $319 million as of September 30, 2015 and December 31, 2014 , respectively; offset by payables to ZionSolutions, LLC of $217 million and $292 million as of September 30, 2015 and December 31, 2014 , respectively. These items are included to provide information regarding the relative size of the ZionSolutions, LLC unconsolidated VIE. The carrying amounts and classification of the consolidated VIEs’ assets and liabilities included in Exelon’s, Generation’s, and BGE’s consolidated financial statements at September 30, 2015 and December 31, 2014 are as follows: September 30, 2015 December 31, 2014 Exelon (a) Generation BGE Exelon (a) Generation BGE Current assets $ 1,108 $ 1,057 $ 46 $ 1,271 $ 1,242 $ 21 Noncurrent assets 7,736 7,728 3 7,580 7,566 3 Total assets $ 8,844 $ 8,785 $ 49 $ 8,851 $ 8,808 $ 24 Current liabilities $ 494 $ 408 $ 81 $ 611 $ 526 $ 77 Noncurrent liabilities 2,859 2,773 81 2,730 2,600 120 Total liabilities $ 3,353 $ 3,181 $ 162 $ 3,341 $ 3,126 $ 197 _______________________ (a) Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	9 Months Ended
	Sep. 30, 2015
Regulated Operations [Abstract]
Schedule of Regulatory Assets	September 30, 2015 Exelon ComEd PECO BGE Regulatory assets Pension and other postretirement benefits $ 3,138 $ — $ — $ — Deferred income taxes 1,589 66 1,446 77 AMI programs 373 130 64 179 Under-recovered distribution service costs (a) 240 240 — — Debt costs 50 48 2 8 Fair value of BGE long-term debt 170 — — — Severance 10 — — 10 Asset retirement obligations 106 66 22 18 MGP remediation costs (g) 289 256 32 1 Under-recovered uncollectible accounts 54 54 — — Renewable energy 243 243 — — Energy and transmission programs (b) (c) 67 33 — 34 Deferred storm costs (g) 2 — — 2 Electric generation-related regulatory asset (g) 23 — — 23 Rate stabilization deferral 101 — — 101 Energy efficiency and demand response programs 271 — — 271 Merger integration costs 6 — — 6 Conservation voltage reduction 1 — — 1 Under-recovered revenue decoupling (f) 7 — — 7 Other 39 9 23 4 Total regulatory assets 6,779 1,145 1,589 742 Less: current portion 779 232 32 257 Total noncurrent regulatory assets $ 6,000 $ 913 $ 1,557 $ 485 September 30, 2015 Exelon ComEd PECO BGE Regulatory liabilities Other postretirement benefits $ 65 $ — $ — $ — Nuclear decommissioning 2,538 2,150 388 — Removal costs 1,545 1,342 — 203 Energy efficiency and demand response programs (d) 46 44 2 — DLC Program Costs 9 — 9 — Energy efficiency phase II 38 — 38 — Electric distribution tax repairs 97 — 97 — Gas distribution tax repairs 30 — 30 — Energy and transmission programs (b)(c)(e) 134 46 70 18 Over-recovered electric universal service fund costs 3 — 3 — Over-recovered revenue decoupling (f) 27 — — 27 Other 13 3 3 7 Total regulatory liabilities 4,545 3,585 640 255 Less: current portion 365 144 104 69 Total noncurrent regulatory liabilities $ 4,180 $ 3,441 $ 536 $ 186 December 31, 2014 Exelon ComEd PECO BGE Regulatory assets Pension and other postretirement benefits $ 3,256 $ — $ — $ — Deferred income taxes 1,542 64 1,400 78 AMI programs 296 91 77 128 Under-recovered distribution service costs (a) 371 371 — — Debt costs 57 53 4 9 Fair value of BGE long-term debt 190 — — — Severance 12 — — 12 Asset retirement obligations 116 74 26 16 MGP remediation costs 257 219 37 1 Under-recovered uncollectible accounts 67 67 — — Renewable energy 207 207 — — Energy and transmission programs (b)(c) 48 33 — 15 Deferred storm costs 3 — — 3 Electric generation-related regulatory asset 30 — — 30 Rate stabilization deferral 160 — — 160 Energy efficiency and demand response programs 248 — — 248 Merger integration costs 8 — — 8 Conservation voltage reduction 2 — — 2 Under recovered electric revenue decoupling (f) 7 — — 7 Other 46 22 14 7 Total regulatory assets 6,923 1,201 1,558 724 Less: current portion 847 349 29 214 Total noncurrent regulatory assets $ 6,076 $ 852 $ 1,529 $ 510 December 31, 2014 Exelon ComEd PECO BGE Regulatory liabilities Other postretirement benefits $ 88 $ — $ — $ — Nuclear decommissioning 2,879 2,389 490 — Removal costs 1,566 1,343 — 223 Energy efficiency and demand response programs (d) 27 25 2 — DLC Program Costs 10 — 10 — Energy efficiency phase II 32 — 32 — Electric distribution tax repairs 102 — 102 — Gas distribution tax repairs 49 — 49 — Energy and transmission programs (b)(c)(e) 84 19 58 7 Over-recovered electric universal service fund costs 2 — 2 — Revenue subject to refund 3 3 — — Over-recovered revenue decoupling (f) 12 — — 12 Other 6 1 2 2 Total regulatory liabilities 4,860 3,780 747 244 Less: current portion 310 125 90 44 Total noncurrent regulatory liabilities $ 4,550 $ 3,655 $ 657 $ 200 ________________ (a) As of September 30, 2015 , ComEd’s regulatory asset of $240 million was comprised of $184 million for the applicable annual reconciliations and $56 million related to significant one-time events including $43 million of deferred storm costs and $13 million of Constellation merger and integration related costs. As of December 31, 2014, ComEd’s regulatory asset of $371 million was comprised of $286 million for the applicable annual reconciliations and $85 million related to significant one-time events, including $66 million of deferred storm costs and $19 million of Constellation merger and integration related costs. See Note 4 — Mergers, Acquisitions, and Dispositions of the Exelon 2014 Form 10-K for further information. (b) As of September 30, 2015 , ComEd’s regulatory asset of $33 million included $26 million associated with transmission costs recoverable through its FERC approved formulate rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of September 30, 2015 , ComEd’s regulatory liability of $46 million included $24 million related to over-recovered energy costs for hourly customers and $22 million associated with revenues received for renewable energy requirements. As of December 31, 2014, ComEd’s regulatory asset of $33 million included $4 million related to under-recovered energy costs for non-hourly customers, $22 million associated with transmission costs recoverable through its FERC approved formulate rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2014, ComEd’s regulatory liability of $19 million included $3 million related to over-recovered energy costs for hourly customers and $16 million associated with revenues received for renewable energy requirements. (c) As of September 30, 2015 , BGE's regulatory asset of $34 million included $5 million associated with transmission costs recoverable through its FERC approved formula rate and $29 million related to under-recovered electric energy costs. As of September 30, 2015 , BGE's regulatory liability of $18 million related to $9 million of over-recovered natural gas supply costs and $ 14 million of over-recovered energy costs, offset by $4 million of Constellation merger and integration costs and $1 million of abandonment costs to be recovered upon FERC approval. As of December 31, 2014 , BGE's regulatory asset of $15 million included $10 million related to under-recovered electric energy costs, $4 million of Constellation merger and integration costs and $1 million of abandonment costs to be recovered upon FERC approval. As of December 31, 2014 , BGE's regulatory liability of $7 million related to over-recovered natural gas supply costs. (d) ComEd recovers the costs of its ICC-approved Energy Efficiency and Demand Response plan through a rider. Effective with a change to its rider in August 2015, ComEd will recover or refund any under or over-recoveries through the end of the Plan's fiscal year on May 31 over a twelve-month period beginning on June 1 of the following calendar year. Previously, ComEd's recovery or refund of under or over-recoveries through the end of the Plan's fiscal year on May 31 was over a nine-month period beginning on September 1 of the same calendar year. (e) As of September 30, 2015 , PECO's regulatory liability of $70 million included $33 million related to the DSP program, $31 million related to the over-recovered natural gas costs under the PGC and $6 million related to over-recovered electric transmission costs. As of December 31, 2014 , PECO's regulatory liability of $58 million included $39 million related to the DSP program, $16 million related to the over-recovered natural gas costs under the PGC and $3 million related to the over-recovered electric transmission costs. (f) Represents the electric and gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of September 30, 2015 , BGE had a regulatory asset of $7 million related to under-recovered electric revenue decoupling and a regulatory liability of $27 million related to over-recovered natural gas revenue decoupling. As of December 31, 2014 , BGE had a regulatory asset of $7 million related to under-recovered electric revenue decoupling and a regulatory liability of $12 million related to over-recovered natural gas revenue decoupling. (g) In accordance with the MDPSC approved 2014 electric and natural gas distribution rate case orders, the recovery periods for these regulatory assets were revised, effective in January 2015.
Purchase Of Receivables	As of December 31, 2014 Exelon ComEd PECO BGE Purchased receivables (a) $ 290 $ 139 $ 76 $ 75 Allowance for uncollectible accounts (b) (42 ) (21 ) (8 ) (13 ) Purchased receivables, net $ 248 $ 118 $ 68 $ 62 _________ (a) PECO’s gas POR program became effective on January 1, 2012 and includes a 1% discount on purchased receivables in order to recover the implementation costs of the program. The implementation costs were fully recovered and the 1% discount was reset to 0%, effective July 2015. (b) For ComEd and BGE, reflects the incremental allowance for uncollectible accounts recorded, which is in addition to the purchase discount. For ComEd, the incremental uncollectible accounts expense is recovered through its Purchase of Receivables with Consolidated Billing tariff.

Impairment of Long-lived Asse31

Impairment of Long-lived Assets (Tables)	9 Months Ended
	Sep. 30, 2015
Property, Plant and Equipment [Abstract]
Schedule of Capital Leased Assets	At September 30, 2015 and December 31, 2014 , the components of the net investment in long-term leases were as follows: September 30, 2015 December 31, 2014 Estimated residual value of leased assets $ 639 $ 685 Less: unearned income 291 324 Net investment in long-term leases $ 348 $ 361

Implications of Potential Ear32

Implications of Potential Early Plant Retirements Implications of Potential Early Plant Retirements (Tables)	9 Months Ended
	Sep. 30, 2015
Implications of Potential Early Plant Retirements [Abstract]
ImplicationsofPotentialEarlyPlantRetirements [Table Text Block]	(in millions) Quad Cities Clinton Ginna Total Asset Balances Materials and supplies inventory $ 49 $ 56 $ 30 $ 135 Nuclear fuel inventory, net 186 122 65 373 Completed plant, net 1,027 582 111 1,720 Construction work in progress 29 8 23 60 Liability Balances Asset retirement obligation (696 ) (396 ) (637 ) (1,729 ) NRC License Renewal Term 2032 2046 (a) 2029 ________ (a) Assumes Clinton seeks and receives a 20-year operating license renewal extension.

Fair Value of Financial Asset33

Fair Value of Financial Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2015
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	The following tables present the carrying amounts and fair values of the Registrants’ short-term liabilities, long-term debt, SNF obligation, and trust preferred securities (long-term debt to financing trusts or junior subordinated debentures) as of September 30, 2015 and December 31, 2014 : Exelon September 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 678 $ 3 $ 675 $ — $ 678 Long-term debt (including amounts due within one year) 25,438 1,004 24,181 1,335 26,520 Long-term debt to financing trusts 648 — — 663 663 SNF obligation 1,021 — 820 — 820 December 31, 2014 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 463 $ 3 $ 448 $ 12 $ 463 Long-term debt (including amounts due within one year) 21,164 1,208 20,417 1,311 22,936 Long-term debt to financing trusts 648 — — 648 648 SNF obligation 1,021 — 833 — 833
Assets and liabilities measured and recorded at fair value on recurring basis	The following tables present assets and liabilities measured and recorded at fair value on Exelon's and Generation’s Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of September 30, 2015 and December 31, 2014 : Generation Exelon As of September 30, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 225 $ — $ — $ 225 $ 6,545 $ — $ — $ 6,545 Nuclear decommissioning trust fund investments Cash equivalents 301 67 — 368 301 67 — 368 Equity Domestic 2,274 1,829 — 4,103 2,274 1,829 — 4,103 Foreign 598 — — 598 598 — — 598 Equity funds subtotal 2,872 1,829 — 4,701 2,872 1,829 — 4,701 Fixed income Corporate debt — 1,831 245 2,076 — 1,831 245 2,076 Generation Exelon As of September 30, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total U.S. Treasury and agencies 1,142 — — 1,142 1,142 — — 1,142 Foreign governments — 77 — 77 — 77 — 77 State and municipal debt — 407 — 407 — 407 — 407 Other — 468 — 468 — — 468 — — — 468 Fixed income subtotal 1,142 2,783 245 4,170 1,142 2,783 245 4,170 Middle market lending — — 423 423 — — 423 423 Private equity — — 116 116 — — 116 116 Real estate — — 30 30 — — — — 30 30 Other — 329 — 329 — 329 — 329 Nuclear decommissioning trust fund investments subtotal (b) 4,315 5,008 814 10,137 4,315 5,008 814 10,137 Pledged assets for Zion Station decommissioning Cash equivalents — 11 — 11 — 11 — 11 Equities 5 1 — 6 5 1 — 6 Fixed income U.S. Treasury and agencies 5 2 — 7 5 2 — 7 Corporate debt — 57 — 57 — 57 — 57 State and municipal debt — 10 — 10 — 10 — 10 Other — 1 — 1 — — 1 — — 1 Fixed income subtotal 5 70 — 75 5 70 — 75 Middle market lending — — 144 144 — — 144 144 Pledged assets for Zion Station decommissioning subtotal (c) 10 82 144 236 10 82 144 236 Rabbi trust investments in mutual funds (d)(e) 16 — — 16 46 — — 46 Commodity derivative assets Economic hedges 1,625 2,561 2,144 6,330 1,625 2,561 2,144 6,330 Proprietary trading 85 140 38 263 85 140 38 263 Effect of netting and allocation of collateral (f) (1,865 ) (2,037 ) (835 ) (4,737 ) (1,865 ) (2,037 ) (835 ) (4,737 ) Commodity derivative assets subtotal (155 ) 664 1,347 1,856 (155 ) 664 1,347 1,856 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — — — — — 37 — 37 Economic hedges — 21 — 21 — 21 — 21 Proprietary trading 14 3 — 17 14 3 — 17 Effect of netting and allocation of collateral (8 ) (6 ) — (14 ) (8 ) (6 ) — (14 ) Interest rate and foreign currency derivative assets subtotal 6 18 — 24 6 55 — 61 Other investments — — 32 32 — — 32 32 Total assets 4,417 5,772 2,337 12,526 10,767 5,809 2,337 18,913 Generation Exelon As of September 30, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Liabilities Commodity derivative liabilities Economic hedges (2,120 ) (2,478 ) (1,209 ) (5,807 ) (2,120 ) (2,478 ) (1,452 ) (6,050 ) Proprietary trading (79 ) (140 ) (44 ) (263 ) (79 ) (140 ) (44 ) (263 ) Effect of netting and allocation of collateral (f) 2,218 2,472 1,080 5,770 2,218 2,472 1,080 5,770 Commodity derivative liabilities subtotal 19 (146 ) (173 ) (300 ) 19 (146 ) (416 ) (543 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (21 ) — (21 ) — (21 ) — (21 ) Economic hedges — (6 ) — (6 ) — (6 ) — (6 ) Proprietary trading (15 ) — — (15 ) (15 ) — — (15 ) Effect of netting and allocation of collateral 15 6 — 21 15 6 — 21 Interest rate and foreign currency derivative liabilities subtotal — (21 ) — (21 ) — (21 ) — (21 ) Deferred compensation obligation — (29 ) — (29 ) — (95 ) — (95 ) Total liabilities 19 (196 ) (173 ) (350 ) 19 (262 ) (416 ) (659 ) Total net assets $ 4,436 $ 5,576 $ 2,164 $ 12,176 $ 10,786 $ 5,547 $ 1,921 $ 18,254 Generation Exelon As of December 31, 2014 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 405 $ — $ — $ 405 $ 1,119 $ — $ — $ 1,119 Nuclear decommissioning trust fund investments Cash equivalents 208 37 — 245 208 37 — 245 Equity Domestic 2,423 2,207 — 4,630 2,423 2,207 — 4,630 Foreign 612 — — 612 612 — — 612 Equity funds subtotal 3,035 2,207 — 5,242 3,035 2,207 — 5,242 Fixed income Corporate debt — 2,023 239 2,262 — 2,023 239 2,262 U.S. Treasury and agencies 996 — — 996 996 — — 996 Foreign governments — 95 — 95 — 95 — 95 State and municipal debt — 438 — 438 — 438 — 438 Other — 511 — 511 — — 511 — — 511 Fixed income subtotal 996 3,067 239 4,302 996 3,067 239 4,302 Middle market lending — — 366 366 — — 366 366 Private equity — — 83 83 — — 83 83 Real estate — — 3 3 — — — — 3 3 Other — 301 — 301 — 301 — 301 Nuclear decommissioning trust fund investments subtotal (b) 4,239 5,612 691 10,542 4,239 5,612 691 10,542 Pledged assets for Zion Station decommissioning Cash equivalents — 15 — 15 — 15 — 15 Equities 6 1 — 7 6 1 — 7 Fixed income U.S. Treasury and agencies 5 3 — 8 5 3 — 8 Corporate debt — 89 — 89 — 89 — 89 State and municipal debt — 10 — 10 — 10 — 10 Other — 3 — 3 — — 3 — — 3 Fixed income subtotal 5 105 — 110 5 105 — 110 Middle market lending — — 184 184 — — 184 184 Generation Exelon As of December 31, 2014 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Pledged assets for Zion Station decommissioning subtotal (c) 11 121 184 316 11 121 184 316 Rabbi trust investments (d) Cash equivalents — — — — 1 — — 1 Mutual funds (e) 16 — — 16 46 — — 46 Rabbi trust investments subtotal 16 — — 16 47 — — 47 Commodity derivative assets Economic hedges 1,667 3,465 1,681 6,813 1,667 3,465 1,681 6,813 Proprietary trading 201 284 27 512 201 284 27 512 Effect of netting and allocation of collateral (f) (1,982 ) (2,757 ) (557 ) (5,296 ) (1,982 ) (2,757 ) (557 ) (5,296 ) Commodity derivative assets subtotal (114 ) 992 1,151 2,029 (114 ) 992 1,151 2,029 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — 8 — 8 — 31 — 31 Economic hedges — 12 — 12 — 13 — 13 Proprietary trading 18 9 — 27 18 9 — 27 Effect of netting and allocation of collateral (17 ) (12 ) — (29 ) (17 ) (31 ) — (48 ) Interest rate and foreign currency derivative assets subtotal 1 17 — 18 1 22 — 23 Other investments — — 3 3 2 — 3 5 Total assets 4,558 6,742 2,029 13,329 5,305 6,747 2,029 14,081 Liabilities Commodity derivative liabilities Economic hedges (2,241 ) (3,458 ) (788 ) (6,487 ) (2,241 ) (3,458 ) (995 ) (6,694 ) Proprietary trading (195 ) (295 ) (42 ) (532 ) (195 ) (295 ) (42 ) (532 ) Effect of netting and allocation of collateral (f) 2,416 3,557 729 6,702 2,416 3,557 729 6,702 Commodity derivative liabilities subtotal (20 ) (196 ) (101 ) (317 ) (20 ) (196 ) (308 ) (524 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (12 ) — (12 ) — (41 ) — (41 ) Economic hedges — (2 ) — (2 ) — (103 ) — (103 ) Proprietary trading (14 ) (9 ) — (23 ) (14 ) (9 ) — (23 ) Effect of netting and allocation of collateral 25 10 — 35 25 29 — 54 Interest rate and foreign currency derivative liabilities subtotal 11 (13 ) — (2 ) 11 (124 ) — (113 ) Deferred compensation obligation — (31 ) — (31 ) — (107 ) — (107 ) Total liabilities (9 ) (240 ) (101 ) (350 ) (9 ) (427 ) (308 ) (744 ) Total net assets $ 4,549 $ 6,502 $ 1,928 $ 12,979 $ 5,296 $ 6,320 $ 1,721 $ 13,337 ______________ (a) Excludes certain cash equivalents considered to be held-to-maturity and not reported at fair value. (b) Excludes net liabilities of $(34) million and $(5) million at September 30, 2015 and December 31, 2014 , respectively. These items consist of net receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases. (c) Excludes net assets of $1 million and $3 million at September 30, 2015 and December 31, 2014 , respectively. These items consist of net receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases. (d) Excludes $34 million and $35 million of cash surrender value of life insurance investment at September 30, 2015 and December 31, 2014 , respectively, at Exelon Consolidated. Excludes $12 million and $11 million and of cash surrender value of life insurance investment at September 30, 2015 and December 31, 2014 , respectively, at Generation. (e) The mutual funds held by the Rabbi trusts at Exelon include $45 million related to deferred compensation and $1 million related to Supplemental Executive Retirement Plan at September 30, 2015 , and $45 million related to deferred compensation and $1 million related to Supplemental Executive Retirement Plan at December 31, 2014 . (f) Collateral posted to/(received from) counterparties totaled $353 million , $435 million and $245 million allocated to Level 1, Level 2 and Level 3 commodity mark-to-market derivatives, respectively, as of September 30, 2015 . Collateral posted to/(received from) counterparties totaled $434 million , $800 million and $172 million allocated to Level 1, Level 2 and Level 3 commodity mark-to-market derivatives, respectively, as of December 31, 2014 . ComEd, PECO and BGE The following tables present assets and liabilities measured and recorded at fair value on the utility Registrants' Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of September 30, 2015 and December 31, 2014 : ComEd PECO BGE As of September 30, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents $ — $ — $ — $ — $ 4 $ — $ — $ 4 $ 68 $ — $ — $ 68 Rabbi trust investments in mutual funds (a) — — — — 8 — — 8 5 — — 5 Total assets — — — — 12 — — 12 73 — — 73 Liabilities Deferred compensation obligation — (7 ) — (7 ) — (11 ) — (11 ) — (4 ) — (4 ) Mark-to-market derivative liabilities (b) — — (243 ) (243 ) — — — — — — — — Total liabilities — (7 ) (243 ) (250 ) — (11 ) — (11 ) — (4 ) — (4 ) Total net assets (liabilities) $ — $ (7 ) $ (243 ) $ (250 ) $ 12 $ (11 ) $ — $ 1 $ 73 $ (4 ) $ — $ 69 ComEd PECO BGE As of December 31, 2014 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents $ 25 $ — $ — $ 25 $ 12 $ — $ — $ 12 $ 103 $ — $ — $ 103 Rabbi trust investments in mutual funds (a) — — — — 9 — — 9 5 — — $ 5 Total assets 25 — — 25 21 — — 21 108 — — 108 Liabilities Deferred compensation obligation — (8 ) — (8 ) — (15 ) — (15 ) — (5 ) — (5 ) Mark-to-market derivative liabilities (b) — — (207 ) (207 ) — — — — — — — — Total liabilities — (8 ) (207 ) (215 ) — (15 ) — (15 ) — (5 ) — (5 ) Total net assets (liabilities) $ 25 $ (8 ) $ (207 ) $ (190 ) $ 21 $ (15 ) $ — $ 6 $ 108 $ (5 ) $ — $ 103 ______________ (a) At PECO, excludes $12 million and $14 million of the cash surrender value of life insurance investments at September 30, 2015 and December 31, 2014 , respectively. (b) The Level 3 balance includes the current and noncurrent liability of $ 22 million and $ 221 million at September 30, 2015 , respectively, and $20 million and $187 million at December 31, 2014 , respectively, related to floating-to-fixed energy swap contracts with unaffiliated suppliers.
Fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis	The following table presents the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2015 and 2014 : Generation ComEd Exelon Three Months Ended September 30, 2015 Nuclear Decommissioning Trust Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives (b) Eliminated in Consolidation Total Balance as of June 30, 2015 $ 786 $ 156 $ 1,021 $ 30 $ 1,993 $ (223 ) $ — $ 1,770 Total realized / unrealized gains (losses) Included in net income — — (48 ) (a) — (48 ) — — (48 ) Included in noncurrent payables to affiliates 5 — — — 5 — (5 ) — Included in payable for Zion Station decommissioning — 1 — — 1 — — 1 Included in regulatory assets — — — — — (20 ) 5 (15 ) Change in collateral — — 90 — 90 — — 90 Purchases, sales, issuances and settlements Purchases 40 5 50 2 97 — — 97 Sales — (18 ) (5 ) — (23 ) — — (23 ) Settlements (17 ) — — — (17 ) — — (17 ) Transfers into Level 3 — — 69 — 69 — — 69 Transfers out of Level 3 — — (3 ) — (3 ) — — (3 ) Balance as of September 30, 2015 $ 814 $ 144 $ 1,174 $ 32 $ 2,164 $ (243 ) $ — $ 1,921 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held for the three months ended September 30, 2015 $ (1 ) $ — $ 181 $ — $ 180 $ — $ — $ 180 Generation ComEd Exelon Nine Months Ended September 30, 2015 Nuclear Decommissioning Trust Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives (b) Eliminated in Consolidation Total Balance as of December 31, 2014 $ 691 $ 184 $ 1,050 $ 3 $ 1,928 $ (207 ) $ — $ 1,721 Total realized / unrealized gains (losses) Included in net income 4 — (87 ) (a) — (83 ) — — (83 ) Included in noncurrent payables to affiliates 20 — — — 20 — (20 ) — Included in payable for Zion Station decommissioning — 2 — — 2 — — 2 Included in regulatory assets — — — — — (36 ) 20 (16 ) Change in collateral — — 72 — 72 — — 72 Purchases, sales, issuances and settlements Purchases 186 16 107 29 338 — — 338 Sales (8 ) (58 ) (10 ) — (76 ) — — (76 ) Settlements (83 ) — — — (83 ) — — (83 ) Transfers into Level 3 4 — 80 — 84 — — 84 Transfers out of Level 3 — — (38 ) — (38 ) — — (38 ) Balance as of September 30, 2015 $ 814 $ 144 $ 1,174 $ 32 $ 2,164 $ (243 ) $ — $ 1,921 The amount of total gains included in income attributed to the change in unrealized gains related to assets and liabilities held for the nine months ended September 30, 2015 $ 4 $ — $ 536 $ — $ 540 $ — $ — $ 540 ______________ (a) Includes a reduction for the reclassification of $229 million and $623 million of realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2015 , respectively. (b) Includes $19 million of decreases in fair value and a reduction for realized gains due to settlements of $1 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2015 . Includes $44 million of decreases in fair value and an increase for realized losses due to settlements of $8 million for the nine months ended September 30, 2015 . Generation ComEd Exelon Three Months Ended September 30, 2014 Nuclear Decommissioning Trust Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to-Market Derivatives (b) Eliminated in Consolidation Total Balance as of June 30, 2014 $ 592 $ 133 $ 242 $ 10 $ 977 $ (134 ) $ — $ 843 Total realized / unrealized gains (losses) Included in net income 1 — 76 (a) — 77 — — 77 Included in noncurrent payables to affiliates 3 — — — 3 — (3 ) — Included in payable for Zion Station decommissioning — (2 ) — — (2 ) — — (2 ) Included in regulatory assets — — — — — (44 ) 3 (41 ) Change in collateral — — 79 — 79 — — 79 Purchases, sales, issuances and settlements Purchases 83 53 12 — 148 — — 148 Sales (8 ) (18 ) — (7 ) (33 ) — — (33 ) Settlements (27 ) — — — (27 ) — — (27 ) Transfers into Level 3 — — 21 — 21 — — 21 Transfers out of Level 3 — — 1 — 1 — — 1 Balance as of September 30, 2014 $ 644 $ 166 $ 431 $ 3 $ 1,244 $ (178 ) $ — $ 1,066 The amount of total gains included in income attributed to the change in unrealized gains related to assets and liabilities held for the three months ended September 30, 2014 $ 1 $ — $ 163 $ — $ 164 $ — $ — $ 164 Generation ComEd Exelon Nine Months Ended September 30, 2014 Nuclear Decommissioning Trust Fund Investments Pledged Assets for Zion Station Decommissioning Mark-to-Market Derivatives Other Investments Total Generation Mark-to- Market Derivatives (b) Eliminated in Consolidation Total Balance as of December 31, 2013 $ 350 $ 112 $ 465 $ 15 $ 942 $ (193 ) $ — $ 749 Total realized / unrealized gains (losses) Included in net income 5 — (284 ) (a) — (279 ) — — $ (279 ) Included in noncurrent payables to affiliates 14 — — — 14 — (14 ) $ — Included in payable for Zion Station decommissioning — 2 — — 2 — — $ 2 Included in regulatory assets — — — — — 15 14 $ 29 Change in collateral — — 257 — 257 — — $ 257 Purchases, sales, issuances and settlements Purchases 331 95 27 2 455 — — $ 455 Sales (10 ) (43 ) (6 ) (7 ) (66 ) — — $ (66 ) Settlements (46 ) — — — (46 ) — — $ (46 ) Transfers into Level 3 — — (9 ) — (9 ) — — $ (9 ) Transfers out of Level 3 — — (19 ) (7 ) (26 ) — — $ (26 ) Balance as of September 30, 2014 $ 644 $ 166 $ 431 $ 3 $ 1,244 $ (178 ) $ — $ 1,066 The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held for the nine months ended September 30, 2014 $ 3 $ — $ (264 ) $ — $ (261 ) $ — $ — $ (261 ) ______________ (a) Includes a reduction for the reclassification of $ 87 million and $20 million of realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2014. (b) Includes $45 million of decreases in fair value and an increase for realized losses due to settlements of $1 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2014 . Includes $19 million of increases in fair value and a reduction for realized gains due to settlements of $4 million for the nine months ended September 30, 2014 .
Total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis	The following tables present the income statement classification of the total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2015 and 2014 : Generation Exelon Operating Revenues Purchased Power and Fuel Other, net (a) Operating Revenues Purchased Power and Fuel Other, net (a) Total gains (losses) included in net income for the three months ended September 30, 2015 $ (4 ) $ (44 ) $ — $ (4 ) $ (44 ) $ — Total gains (losses) included in net income for the nine months ended September 30, 2015 (31 ) (56 ) 4 (31 ) (56 ) 4 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended September 30, 2015 198 (17 ) (1 ) 198 (17 ) (1 ) Change in the unrealized gains (losses) relating to assets and liabilities held for the nine months ended September 30, 2015 538 (2 ) 4 538 (2 ) 4 Generation Exelon Operating Revenues Purchased Power and Fuel Other, net (a) Operating Revenues Purchased Power and Fuel Other, net (a) Total gains (losses) included in net income for the three months ended September 30, 2014 $ 70 $ 6 $ 1 $ 70 $ 6 $ 1 Total gains (losses) included in net income for the nine months ended September 30, 2014 (260 ) (24 ) 5 (260 ) (24 ) 5 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended September 30, 2014 142 21 1 142 21 1 Change in the unrealized gains (losses) relating to assets and liabilities held for the nine months ended September 30, 2014 (293 ) 29 3 (293 ) 29 3 ______________ (a) Other, net activity consists of realized and unrealized gains (losses) included in income for the NDT funds held by Generation.
Exelon Generation Co L L C [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	Generation September 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 21 $ — $ 21 $ — $ 21 Long-term debt (including amounts due within one year) 8,996 — 7,978 1,335 9,313 SNF obligation 1,021 — 820 — 820 December 31, 2014 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 36 $ — $ 24 $ 12 $ 36 Long-term debt (including amounts due within one year) 8,266 — 7,511 1,311 8,822 SNF obligation 1,021 — 833 — 833
Commonwealth Edison Co [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	ComEd September 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 604 $ — $ 604 $ — $ 604 Long-term debt (including amounts due within one year) 6,100 — 6,731 — 6,731 Long-term debt to financing trust 206 — — 206 206 December 31, 2014 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 304 $ — $ 304 $ — $ 304 Long-term debt (including amounts due within one year) 5,958 — 6,788 — 6,788 Long-term debt to financing trust 206 — — 213 213
PECO Energy Co [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	PECO September 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) $ 2,246 $ — $ 2,472 $ — $ 2,472 Long-term debt to financing trusts 184 — — 196 196 December 31, 2014 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) $ 2,246 $ — $ 2,537 $ — $ 2,537 Long-term debt to financing trusts 184 — — 199 199
Baltimore Gas and Electric Company [Member]
Fair Value Tables [Line Items]
Fair value of financial liabilities recorded at the carrying amount	BGE September 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 53 $ 3 $ 50 $ — $ 53 Long-term debt (including amounts due within one year) 1,905 — 2,118 — 2,118 Long-term debt to financing trusts 258 — — 261 261 December 31, 2014 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 123 $ 3 $ 120 $ — $ 123 Long-term debt (including amounts due within one year) 1,942 — 2,178 — 2,178 Long-term debt to financing trusts 258 — — 236 236

Derivative Financial Instrume34

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of the derivative fair value	Exelon includes the gain or loss on the hedged items and the offsetting loss or gain on the related interest rate swaps in interest expense as follows: Three Months Ended September 30, Income Statement Location 2015 2014 2015 2014 Gain (Loss) on Swaps Gain (Loss) on Borrowings Generation Interest expense (a) $ — $ (4 ) $ — $ 1 Exelon Interest expense 16 (8 ) 13 (6 ) Nine Months Ended September 30, Income Statement Location 2015 2014 2015 2014 Gain (Loss) on Swaps Gain (Loss) on Borrowings Generation Interest expense (a) $ (1 ) $ (12 ) $ — $ 1 Exelon Interest expense 13 (3 ) 8 6 __________ (a) For the three and nine months ended September 30, 2015 , the loss on Generation swaps included $0 million and $1 million realized in earnings, respectively, with an immaterial amount excluded from hedge effectiveness testing. For the three and nine months ended September 30, 2014 , the loss on Generation swaps included $4 million and $12 million realized in earnings, respectively, with an $2 million amount excluded from hedge effectiveness testing. Below is a summary of the interest rate and foreign currency hedges as of September 30, 2015 . Generation Other Exelon Description Derivatives Designated as Hedging Instruments Economic Hedges Proprietary Trading (a) Collateral and Netting (b) Subtotal Derivatives Economic Collateral (b) Subtotal Total Mark-to-market derivative assets $ — $ 11 $ 10 $ (12 ) $ 9 $ — $ — $ — $ — $ 9 Mark-to-market derivative assets assets) — 10 7 (2 ) 15 37 — — 37 52 Total mark-to-market derivative — 21 17 (14 ) 24 37 — — 37 61 Mark-to-market derivative liabilities (current liabilities) (9 ) (6 ) (10 ) 16 (9 ) — — — — (9 ) Mark-to-market derivative liabilities (noncurrent liabilities) (12 ) — (5 ) 5 (12 ) — — — — (12 ) Total mark-to-market derivative (21 ) (6 ) (15 ) 21 (21 ) — — — — (21 ) Total mark-to-market derivative (liabilities) $ (21 ) $ 15 $ 2 $ 7 $ 3 $ 37 $ — $ — $ 37 $ 40 _____________ (a) Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts within the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates. (b) Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as accrued interest, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above. The following table provides a summary of the interest rate and foreign exchange hedge balances recorded by the Registrants as of December 31, 2014 : Generation Other Exelon Description Derivatives Designated as Hedging Instruments Economic Hedges Proprietary Trading (a) Collateral and Netting (b) Subtotal Derivatives Designated as Hedging Instruments Economic Collateral (b) Subtotal Total Mark-to-market $ 7 $ 7 $ 20 $ (22 ) $ 12 $ 3 $ — $ — $ 3 $ 15 Mark-to-market 1 5 7 (7 ) 6 20 1 (19 ) 2 8 Total mark-to-market 8 12 27 (29 ) 18 23 1 (19 ) 5 23 Mark-to-market (8 ) (2 ) (14 ) 25 1 — — — — 1 Mark-to-market (4 ) — (9 ) 10 (3 ) (29 ) (101 ) 19 (111 ) (114 ) Total mark-to-market derivative (12 ) (2 ) (23 ) 35 (2 ) (29 ) (101 ) 19 (111 ) (113 ) Total mark-to-market $ (4 ) $ 10 $ 4 $ 6 $ 16 $ (6 ) $ (100 ) $ — $ (106 ) $ (90 ) _______________ (a) Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts within the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates. (b) Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as accrued interest, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above. The following table provides a summary of the derivative fair value balances recorded by the Registrants as of September 30, 2015 : Generation ComEd Exelon Derivatives Economic Hedges Proprietary Trading Collateral and Netting (a) Subtotal (b) Economic Hedges (c) Total Derivatives Mark-to-market derivative assets (current assets) $ 3,958 $ 221 $ (3,072 ) $ 1,107 $ — $ 1,107 Mark-to-market derivative assets (noncurrent assets) 2,372 42 (1,665 ) 749 — 749 Total mark-to-market derivative assets 6,330 263 (4,737 ) 1,856 — 1,856 Mark-to-market derivative liabilities (current liabilities) (3,719 ) (213 ) 3,759 (173 ) (22 ) (195 ) Mark-to-market derivative liabilities (noncurrent liabilities) (2,088 ) (50 ) 2,011 (127 ) (221 ) (348 ) Total mark-to-market derivative liabilities (5,807 ) (263 ) 5,770 (300 ) (243 ) (543 ) Total mark-to-market derivative net assets (liabilities) $ 523 $ — $ 1,033 $ 1,556 $ (243 ) $ 1,313 _________ (a) Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as trade receivables and payables, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above. (b) Current and noncurrent assets are shown net of collateral of $281 million and $150 million , respectively, and current and noncurrent liabilities are shown net of collateral of $405 million and $197 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $1,033 million at September 30, 2015 . (c) Includes current and noncurrent liabilities relating to floating-to-fixed energy swap contracts with unaffiliated suppliers. The following table provides a summary of the derivative fair value balances recorded by the Registrants as of December 31, 2014 : Generation ComEd Exelon Description Economic Hedges Proprietary Trading Collateral and Netting (a) Subtotal (b) Economic Hedges (c) Total Derivatives Mark-to-market derivative assets (current assets) $ 4,992 $ 456 $ (4,184 ) $ 1,264 $ — $ 1,264 Mark-to-market derivative assets (noncurrent assets) 1,821 56 (1,112 ) 765 — 765 Total mark-to-market derivative assets 6,813 512 (5,296 ) 2,029 — 2,029 Mark-to-market derivative liabilities (current liabilities) (4,947 ) (468 ) 5,200 (215 ) (20 ) (235 ) Mark-to-market derivative liabilities (noncurrent liabilities) (1,540 ) (64 ) 1,502 (102 ) (187 ) (289 ) Total mark-to-market derivative liabilities (6,487 ) (532 ) 6,702 (317 ) (207 ) (524 ) Total mark-to-market derivative net assets (liabilities) $ 326 $ (20 ) $ 1,406 $ 1,712 $ (207 ) $ 1,505 ________ (a) Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as trade receivables and payables, transactions that do not qualify as derivatives, and letters of credit. These are not reflected in the table above. (b) Current and noncurrent assets are shown net of collateral of $416 million and $171 million , respectively, and current and noncurrent liabilities are shown net of collateral of $599 million and $220 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $1,406 million at December 31, 2014 . (c) Includes current and noncurrent liabilities relating to floating-to-fixed energy swap contracts with unaffiliated suppliers.
The activity of accumulated OCI related to cash flow hedges	The amounts reclassified from accumulated OCI, when combined with the impacts of the hedged transactions, result in the ultimate recognition of net revenues or expenses at the contractual price. Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Three Months Ended September 30, 2015 Income Statement Location Total Cash Flow Hedges Total Cash Flow Hedges Accumulated OCI derivative gain at June 30, 2015 $ (21 ) $ (19 ) Effective portion of changes in fair value (7 ) (8 ) Reclassifications from accumulated OCI to net income Interest Expense 3 3 Accumulated OCI derivative gain at September 30, 2015 $ (25 ) $ (24 ) Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Nine Months Ended September 30, 2015 Income Statement Location Total Cash Flow Total Cash Flow Hedges Accumulated OCI derivative gain at December 31, 2014 $ (18 ) $ (28 ) Effective portion of changes in fair value (13 ) (18 ) Reclassifications from accumulated OCI to net income Other, net — 16 (a) Reclassifications from accumulated OCI to net income Interest Expense 8 8 Reclassifications from accumulated OCI to net income Operating Revenues (2 ) (2 ) Accumulated OCI derivative gain at September 30, 2015 $ (25 ) $ (24 ) ______ (a) Amount is net of related income tax expense of $10 million for the nine months ended September 30, 2015 . Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Three Months Ended September 30, 2014 Income Statement Location Total Cash Flow Hedges Total Cash Flow Hedges Accumulated OCI derivative gain at June 30, 2014 $ 45 (a) $ 47 Effective portion of changes in fair value — (3 ) Reclassifications from accumulated OCI to net income Operating Revenues (16 ) (b) (16 ) Accumulated OCI derivative gain at September 30, 2014 $ 29 (a) $ 28 ______ (a) Excludes $13 million of losses, net of taxes, related to interest rate swaps and treasury rate locks as of September 30, 2014 and June 30, 2014 . (b) Amount is net of related income tax expense of $12 million for the three months ended September 30, 2014 . Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Nine Months Ended September 30, 2014 Income Statement Location Total Cash Flow Hedges Total Cash Flow Hedges Accumulated OCI derivative gain at December 31, 2013 $ 116 (a) $ 120 Effective portion of changes in fair value (9 ) (14 ) Reclassifications from accumulated OCI to net income Operating Revenues (78 ) (b) (78 ) Accumulated OCI derivative gain at September 30, 2014 $ 29 (a) $ 28 __________ (a) Excludes $13 million of losses and $5 million of losses, net of taxes, related to interest rate swaps and treasury locks as of September 30, 2014 and December 31, 2013 , respectively. (b) Amount is net of related income tax expense of $52 million for the nine months ended September 30, 2014 .
Other Derivatives - Gain (loss) and reclassification	In the tables below, “Change in fair value” represents the change in fair value of the derivative contracts held at the reporting date. The “Reclassification to realized at settlement” represents the recognized change in fair value that was reclassified to realized due to settlement of the derivative during the period. Location on Income Statement Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Change in fair value of commodity positions Operating Revenues $ (4 ) $ (2 ) $ 5 $ (2 ) Reclassification to realized at settlement of commodity positions Operating Revenues (2 ) (10 ) (8 ) (17 ) Net commodity mark-to-market gains (losses) Operating Revenues (6 ) (12 ) (3 ) (19 ) Change in fair value of treasury positions Operating Revenues 3 1 7 — Reclassification to realized at settlement of treasury positions Operating Revenues (3 ) — (9 ) 1 Net treasury mark-to-market gains (losses) Operating Revenues — 1 (2 ) 1 Total Net mark-to-market gains (losses) Operating Revenues $ (6 ) $ (11 ) $ (5 ) $ (18 ) In the tables below, “Change in fair value” represents the change in fair value of the derivative contracts held at the reporting date. The “Reclassification to realized at settlement” represents the recognized change in fair value that was reclassified to realized due to settlement of the derivative during the period. Generation HoldCo Exelon Three Months Ended September 30, 2015 Operating Revenues Purchased Power and Fuel Interest Expense Total Interest Total Change in fair value of commodity positions $ 136 $ (178 ) $ — $ (42 ) $ — $ (42 ) Reclassification to realized at settlement of commodity positions (143 ) 46 — (97 ) — (97 ) Net commodity mark-to-market gains (losses) (7 ) (132 ) — (139 ) — (139 ) Change in fair value of treasury positions 2 — — 2 — 2 Reclassification to realized at settlement of treasury positions (2 ) — — (2 ) — (2 ) Net treasury mark-to-market gains (losses) — — — — — — Net mark-to-market gains (losses) $ (7 ) $ (132 ) $ — $ (139 ) $ — $ (139 ) Generation HoldCo Exelon Nine Months Ended September 30, 2015 Operating Revenues Purchased Power and Fuel Interest Expense Total Interest Total Change in fair value of commodity positions $ 513 $ (163 ) $ — $ 350 $ — $ 350 Reclassification to realized at settlement of commodity positions (347 ) 249 — (98 ) — (98 ) Net commodity mark-to-market gains (losses) 166 86 — 252 — 252 Change in fair value of treasury positions 12 — — 12 36 48 Reclassification to realized at settlement of treasury positions (6 ) — — (6 ) 64 58 Net treasury mark-to-market gains (losses) 6 — — 6 100 106 Net mark-to-market gains (losses) $ 172 $ 86 $ — $ 258 $ 100 $ 358 Generation HoldCo Exelon Three Months Ended September 30, 2014 Operating Revenues Purchased Power and Fuel Interest Expense Total Interest Total Change in fair value of commodity positions $ 181 $ 19 $ — $ 200 $ — $ 200 Reclassification to realized at settlement of commodity positions 86 (23 ) — 63 — 63 Net commodity mark-to-market gains (losses) 267 (4 ) — 263 — 263 Change in fair value of treasury positions 5 — (3 ) 2 (8 ) (6 ) Reclassification to realized at settlement of treasury positions (1 ) — — (1 ) — (1 ) Net treasury mark-to-market gains (losses) 4 — (3 ) 1 (8 ) (7 ) Net mark-to-market gains (losses) $ 271 $ (4 ) $ (3 ) $ 264 $ (8 ) $ 256 Generation HoldCo Exelon Nine Months Ended September 30, 2014 Operating Revenues Purchased Power and Fuel Interest Expense Total Interest Total Change in fair value of commodity positions $ (795 ) $ 302 $ — $ (493 ) $ — $ (493 ) Reclassification to realized at settlement of commodity positions 224 (207 ) — 17 — $ 17 Net commodity mark-to-market gains (losses) (571 ) 95 — (476 ) — (476 ) Change in fair value of treasury positions 1 — (5 ) (4 ) (8 ) (12 ) Reclassification to realized at settlement of treasury positions (2 ) — — (2 ) — (2 ) Net treasury mark-to-market gains (losses) (1 ) — (5 ) (6 ) (8 ) (14 ) Net mark-to-market gains (losses) $ (572 ) $ 95 $ (5 ) $ (482 ) $ (8 ) $ (490 )
Information on Generation's credit exposure for all derivative instruments, normal purchase normal sales, and applicable payables and receivables, net of collateral and instruments that are subject to master netting agreements	The aggregate fair value of all derivative instruments with credit-risk-related contingent features in a liability position that are not fully collateralized (excluding transactions on the exchanges that are fully collateralized) is detailed in the table below: Credit-Risk Related Contingent Feature September 30, 2015 December 31, 2014 Gross Fair Value of Derivative Contracts Containing this Feature (a) $ (1,533 ) $ (1,433 ) Offsetting Fair Value of In-the-Money Contracts Under Master Netting Arrangements (b) 1,302 1,140 Net Fair Value of Derivative Contracts Containing This Feature (c) $ (231 ) $ (293 ) __________ (a) Amount represents the gross fair value of out-of-the-money derivative contracts containing credit-risk related contingent features ignoring the effects of master netting agreements. (b) Amount represents the offsetting fair value of in-the-money derivative contracts under legally enforceable master netting agreements with the same counterparty, which reduces the amount of any liability for which a Registrant could potentially be required to post collateral. (c) Amount represents the net fair value of out-of-the-money derivative contracts containing credit-risk related contingent features after considering the mitigating effects of offsetting positions under master netting arrangements and reflects the actual net liability upon which any potential contingent collateral obligations would be based.
Disclosure of Credit Derivatives [Table Text Block]	Additionally, the figures in the tables below exclude exposures with affiliates, including net receivables with ComEd, PECO and BGE of $24 million , $33 million and $27 million , as of September 30, 2015 , respectively. Rating as of September 30, 2015 Total Exposure Before Credit Collateral Credit Collateral (a) Net Exposure Number of Counterparties Greater than 10% of Net Exposure Net Exposure of Counterparties Greater than 10% of Net Exposure Investment grade $ 1,463 $ 18 $ 1,445 1 $ 444 Non-investment grade 55 15 40 — — No external ratings Internally rated — investment grade 535 — 535 — — Internally rated — non-investment grade 53 5 48 — — Total $ 2,106 $ 38 $ 2,068 1 $ 444 Net Credit Exposure by Type of Counterparty As of September 30, 2015 Financial institutions $ 260 Investor-owned utilities, marketers, power producers 867 Energy cooperatives and municipalities 908 Other 33 Total $ 2,068 _____________________ (a) As of September 30, 2015 , credit collateral held from counterparties where Generation had credit exposure included $13 million of cash and $25 million of letters of credit.

Debt and Credit Agreements (Tab

Debt and Credit Agreements (Tables)	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Schedule of Short-term Debt	Exelon had bank lines of credit under committed credit facilities at September 30, 2015 for short-term financial needs, as follows: Type of Credit Facility Amount (a) Expiration Dates Capacity Type (In billions) Exelon Corporate Syndicated Revolver (b) $ 0.5 May 2019 Letters of credit and cash Generation Syndicated Revolver 5.1 May 2019 Letters of credit and cash Syndicated Revolver 0.2 August 2018 Letters of credit and cash Bilateral 0.3 December 2015 and March 2016 Letters of credit and cash Bilateral 0.1 January 2017 Letters of credit Bilateral 0.1 October 2015 Letters of credit and cash ComEd Syndicated Revolver 1.0 March 2019 Letters of credit and cash PECO Syndicated Revolver (b) 0.6 May 2019 Letters of credit and cash BGE Syndicated Revolver (b) 0.6 May 2019 Letters of credit and cash Total $ 8.5 (a) Excludes additional credit facility agreements for Generation, ComEd, PECO and BGE with aggregate commitments of $50 million , $34 million , $34 million and $5 million , respectively, arranged with minority and community banks located primarily within ComEd’s, PECO’s and BGE’s service territories. These facilities expire d on October 16, 2015 and were renewed at the same amount through October 14, 2016. These facilities are solely utilized to issue letters of credit. As of September 30, 2015 , letters of credit issued under these agreements for Generation, ComEd, PECO and BGE totaled $7 million , $16 million , $21 million and $1 million , respectively. (b) Syndicated revolvers include credit facility commitments of $22 million , $27 million and $27 million for Exelon Corporate, PECO and BGE, respectively, which expire in August 2018. The Registrants had the following amounts of commercial paper borrowings outstanding as of September 30, 2015 and December 31, 2014 : Commercial Paper Borrowings September 30, 2015 December 31, 2014 Exelon Corporate $ — $ — Generation — — ComEd 604 304 PECO — — BGE 50 120
Schedule Of Issuance Of Long Term Debt	During the nine months ended September 30, 2015 , the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Exelon Corporate Senior Unsecured Notes (a) 1.55 % June 9, 2017 $ 550 Finance a portion of the pending acquisition of PHI and related costs and expenses, and for general corporate purposes Exelon Corporate Senior Unsecured Notes (a) 2.85 % June 15, 2020 $ 900 Finance a portion of the pending acquisition of PHI and related costs and expenses, and for general corporate purposes Exelon Corporate Senior Unsecured Notes (a) 3.95 % June 15, 2025 $ 1,250 Finance a portion of the pending acquisition of PHI and related costs and expenses, and for general corporate purposes Exelon Corporate Senior Unsecured Notes (a) 4.95 % June 15, 2035 $ 500 Finance a portion of the pending acquisition of PHI and related costs and expenses, and for general corporate purposes Exelon Corporate Senior Unsecured Notes (a) 5.10 % June 15, 2045 $ 1,000 Finance a portion of the pending acquisition of PHI and related costs and expenses, and for general corporate purposes Exelon Corporate Long Term Software License Agreement 3.95 % May 1, 2024 $ 111 Procurement of software licenses Generation Senior Unsecured Notes (b) 2.95 % January 15, 2020 $ 750 Fund the optional redemption of Exelon's $550 million, 4.550% Senior Notes and for general corporate purposes Generation AVSR DOE Nonrecourse Debt 2.29 - 2.96% January 5, 2037 $ 39 Antelope Valley solar development Generation Energy Efficiency Project Financing 3.71 % October 1, 2035 $ 42 Funding to install energy conservation measures in Coleman, Florida Generation Energy Efficiency Project Financing 3.55 % November 15, 2016 $ 19 Funding to install energy conservation measures in Frederick, Maryland Generation Tax Exempt Pollution Control Revenue Bonds (c) 2.50 - 2.70% 2019 - 2020 $ 435 General corporate purposes Generation Albany Green Energy Project Financing LIBOR + 1.25% November 17, 2017 $ 74 Albany Green Energy biomass generation development ComEd Mortgage Bonds Series 118 3.70 % March 1, 2045 $ 400 Refinance maturing mortgage bonds, repay a portion of ComEd's outstanding commercial paper obligations and for general corporate purposes _____________ (a) In connection with the issuance of PHI acquisition financing, Exelon terminated its interest rate swaps that had been designated as cash flow hedges. See Note 10 — Derivative Financial Instruments for further information. (b) In connection with the issuance of Senior Unsecured Notes, Exelon terminated floating-to-fixed interest rate swaps that had been designated as cash flow hedges. See Note 10 — Derivative Financial Instruments for further information on the swap termination. (c) The Tax Exempt Pollution Control Revenue Bonds have a mandatory put date that ranges from March 1, 2019 - September 1, 2020.
Schedule of Long-term Debt Instruments	During the nine months ended September 30, 2014 , the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Exelon Junior Subordinated Notes 2.50 % June 1, 2024 $ 1,150 Finance a portion of the acquisition of PHI and for general corporate purposes Generation Nuclear Fuel Purchase Contract 3.25 - 3.35% June 30, 2018 $ 70 Procurement of uranium Generation ExGen Renewables I Nonrecourse Debt LIBOR + 4.25% February 6, 2021 $ 300 General corporate purposes Generation ExGen Texas Power Nonrecourse Debt LIBOR + 4.75% September 18, 2021 $ 675 General corporate purposes Generation Energy Efficiency Project Financing 4.12 % December 31, 2015 $ 12 Funding to install energy conservation measures in Washington, DC Generation AVSR DOE Nonrecourse Debt 3.06 - 3.14% January 5, 2037 $ 125 Antelope Valley solar development ComEd First Mortgage Bonds Series 115 2.15 % January 15, 2019 $ 300 Refinance maturing mortgage bonds and general corporate purposes ComEd First Mortgage Bonds Series 116 4.70 % January 15, 2044 $ 350 Refinance maturing mortgage bonds and general corporate purposes PECO First and Refunding Mortgage Bonds 4.15 % October 1, 2044 $ 300 Refinance existing mortgage bonds and general corporate purposes
Retirement and Redemptions of Current and Long-Term Debt	During the nine months ended September 30, 2014 , the following long-term debt was retired and/or redeemed: Company Type Interest Rate Maturity Amount Generation Senior Unsecured Notes 5.35 % January 15, 2014 $ 500 Generation Pollution Control Notes 4.10 % July 1, 2014 $ 20 Generation Continental Wind Nonrecourse Debt 6.00 % February 28, 2033 $ 20 Generation Kennett Square Capital Lease 7.83 % September 20, 2020 $ 2 Generation ExGen Renewables I Nonrecourse Debt 3mL + 4.25% February 6, 2021 $ 3 Generation AVSR DOE Nonrecourse Debt 2.33% - 3.55% January 5, 2037 $ 4 Generation Clean Horizons Solar Nonrecourse Debt 2.56 % September 7, 2030 $ 1 Generation Sacramento Solar Nonrecourse Debt 2.56 % December 31, 2030 $ 1 Generation Energy Efficiency Project Financing 4.40 % August 31, 2014 $ 9 ComEd Mortgage Bonds Series 110 1.63 % January 15, 2014 $ 600 ComEd Pollution Control Series 1994C 5.85 % January 15, 2014 $ 17 BGE Rate Stabilization Bonds 5.72 % April 1, 2016 $ 35 During the nine months ended September 30, 2015 , the following long-term debt was retired and/or redeemed: Company Type Interest Rate Maturity Amount Exelon Corporate (a) Senior Unsecured Notes 4.55 % June 15, 2015 $ 550 Exelon Corporate Senior Notes 4.90 % June 15, 2015 $ 800 Exelon Corporate Long Term Software License Agreement 3.95 % May 1, 2024 $ 1 Generation (a) Senior Unsecured Notes 4.55 % June 15, 2015 $ 550 Generation CEU Upstream Nonrecourse Debt LIBOR + 2.25% January 14, 2019 $ 9 Generation AVSR DOE Nonrecourse Debt 2.29%-3.56% January 5, 2037 $ 12 Generation Kennett Square Capital Lease 7.83 % September 20, 2020 $ 3 Generation Continental Wind Nonrecourse Debt 6.00 % February 28, 2033 $ 20 Generation ExGen Texas Power Nonrecourse Debt LIBOR + 4.75% September 8, 2021 $ 5 Generation ExGen Renewables I Nonrecourse Debt LIBOR + 4.25% February 6, 2021 $ 14 Generation Constellation Solar Horizons Nonrecourse Debt 2.56 % September 7, 2030 $ 1 Generation Sacramento PV Energy Nonrecourse Debt 2.58 % December 31, 2030 $ 1 ComEd FMB Series 101 4.70 % April 15, 2015 $ 260 BGE Rate Stabilization Bonds 5.72 % April 1, 2016 $ 37 ____________ (a) As part of the 2012 Constellation merger, Exelon and subsidiaries of Generation assumed intercompany loan agreements that mirrored the terms and amounts of external obligations held by Exelon, resulting in intercompany notes payable at Generation and Exelon Corporate.

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation	For the Three Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit 2.7 2.1 5.0 1.2 5.3 Qualified nuclear decommissioning trust fund income (5.4 ) (12.5 ) — — — Domestic production activities deduction (4.9 ) (11.6 ) — — — Health care reform legislation — — — — 0.2 Amortization of investment tax credit, net deferred taxes (2.3 ) (5.2 ) (0.3 ) (0.1 ) (0.2 ) Plant basis differences (1.4 ) — (0.1 ) (7.0 ) (0.6 ) Production tax credits and other credits (3.8 ) (9.0 ) — — — Noncontrolling interest 1.7 3.9 — — — Statute of limitations expiration (6.4 ) (15.2 ) — — — Other 1.2 0.4 0.3 — (0.4 ) Effective income tax rate 16.4 % (12.1 )% 39.9 % 29.1 % 39.3 % For the Nine Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit 3.1 2.8 5.2 1.2 5.3 Qualified nuclear decommissioning trust fund income (0.9 ) (1.6 ) — — — Domestic production activities deduction (2.8 ) (4.9 ) — — — Health care reform legislation — — — — 0.2 Amortization of investment tax credit, net deferred taxes (1.2 ) (1.9 ) (0.3 ) (0.1 ) (0.1 ) Plant basis differences (1.2 ) — (0.1 ) (7.3 ) (0.4 ) Production tax credits and other credits (2.2 ) (3.8 ) — — — Noncontrolling interest — 0.1 — — — Statute of limitations expiration (1.6 ) (2.9 ) — — — Other 0.9 0.6 0.2 0.2 (0.1 ) Effective income tax rate 29.1 % 23.4 % 40.0 % 29.0 % 39.9 % For the Three Months Ended September 30, 2014 Exelon Generation ComEd PECO BGE U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit 3.4 3.7 5.0 0.1 4.6 Qualified nuclear decommissioning trust fund income (0.3 ) (0.4 ) — — — Domestic production activities deduction (2.4 ) (3.2 ) — — — Health care reform legislation — — 0.2 — 0.2 Amortization of investment tax credit, net deferred taxes (1.0 ) (1.2 ) (0.3 ) (0.1 ) (0.3 ) Plant basis differences (0.8 ) — — (11.3 ) 0.5 Production tax credits and other credits (1.9 ) (2.4 ) — — — Noncontrolling interest (1.2 ) (1.6 ) — — — Statute of limitations expiration (3.8 ) (5.0 ) — — — Other 1.2 0.6 0.1 (0.1 ) (1.2 ) Effective income tax rate 28.2 % 25.5 % 40.0 % 23.6 % 38.8 % For the Nine Months Ended September 30, 2014 Exelon Generation ComEd PECO BGE U.S. Federal statutory rate 35.0 % 35.0 % 35.0 % 35.0 % 35.0 % Increase (decrease) due to: State income taxes, net of Federal income tax benefit 2.0 1.2 5.0 0.3 4.9 Qualified nuclear decommissioning trust fund income 2.0 3.6 — — — Domestic production activities deduction (2.7 ) (4.8 ) — — — Health care reform legislation 0.1 — 0.2 — 0.2 Amortization of investment tax credit, net deferred taxes (1.1 ) (1.7 ) (0.3 ) (0.1 ) (0.3 ) Plant basis differences (1.6 ) — (0.3 ) (11.0 ) 0.5 Production tax credits and other credits (2.1 ) (3.7 ) — — — Noncontrolling interest (1.4 ) (2.6 ) — — — Statute of limitations expiration (2.5 ) (4.4 ) — — — Other (0.5 ) (0.7 ) 0.1 0.1 (0.5 ) Effective income tax rate 27.2 % 21.9 % 39.7 % 24.3 % 39.8 %

Nuclear Decommissioning (Tables

Nuclear Decommissioning (Tables) - Exelon Generation Co L L C [Member]	9 Months Ended
	Sep. 30, 2015
Schedule Of Nuclear Decommissioning [Line Items]
Nuclear decommissioning asset retirement obligation rollforward	The following table provides a rollforward of the nuclear decommissioning ARO reflected on Exelon’s and Generation’s Consolidated Balance Sheets from December 31, 2014 to September 30, 2015 : Nuclear decommissioning ARO at December 31, 2014 (a) $ 6,961 Net increase due to changes in, and timing of, estimated future cash flows 831 Accretion expense 283 Costs incurred to decommission retired plants (2 ) Nuclear decommissioning ARO at September 30, 2015 (a) $ 8,073 ___________ (a) Includes $7 million and $8 million as the current portion of the ARO at September 30, 2015 and December 31, 2014 respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets.
Unrealized Gains (Losses) on nuclear decommissioning trust funds	The following table provides unrealized gains (losses) on NDT funds for the three and nine months ended September 30, 2015 and 2014 : Exelon and Generation Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Net unrealized gains (losses) on decommissioning trust funds — Regulatory Agreement Units (a) $ (301 ) $ (107 ) $ (385 ) $ 126 Net unrealized gains (losses) on decommissioning trust funds — Non-Regulatory Agreement Units (b)(c) (218 ) (41 ) (274 ) 100 ___________ (a) Net unrealized gains (losses) related to Generation’s NDT funds associated with Regulatory Agreement Units are included in Regulatory liabilities on Exelon’s Consolidated Balance Sheets and Noncurrent payables to affiliates on Generation’s Consolidated Balance Sheets. (b) Excludes $7 million of net unrealized gains related to the Zion Station pledged assets for the three months ended September 30, 2014 and $9 million and $27 million of net unrealized gains related to the Zion Station pledged assets for the nine months ended September 30, 2015 and 2014 , respectively. Net unrealized gains related to Zion Station pledged assets are included in the Payable for Zion Station decommissioning on Exelon’s and Generation’s Consolidated Balance Sheets. (c) Net unrealized gains (losses) related to Generation’s NDT funds with Non-Regulatory Agreement Units are included within Other, net in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income.
Zion Station pledged assets	The following table provides the pledged assets and payables to ZionSolutions and withdrawals by ZionSolutions at September 30, 2015 and December 31, 2014 : Exelon and Generation September 30, 2015 December 31, 2014 Carrying value of Zion Station pledged assets $ 237 $ 319 Payable to Zion Solutions (a) 217 292 Current portion of payable to Zion Solutions (b) 118 137 Cumulative withdrawals by Zion Solutions to pay decommissioning and other costs (c) 757 666 ___________ (a) Excludes a liability recorded within Exelon’s and Generation’s Consolidated Balance Sheets related to the tax obligation on the unrealized activity associated with the Zion Station NDT Funds. The NDT Funds will be utilized to satisfy the tax obligations as gains and losses are realized. (b) Included in Other current liabilities within Exelon’s and Generation’s Consolidated Balance Sheets. (c) Includes project expenses to decommission Zion Station and estimated tax payments on Zion Station NDT Fund earnings.

Retirement Benefits (Tables)

Retirement Benefits (Tables)	9 Months Ended
	Sep. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Schedule of Defined Benefit Plans Disclosures	The following tables present the components of Exelon’s net periodic benefit costs, prior to any capitalization, for the three and nine months ended September 30, 2015 and 2014 . Pension Benefits Three Months Ended September 30, Other Postretirement Benefits Three Months Ended September 30, 2015 (a) 2014 (a) 2015 (a) 2014 (a) Service cost $ 82 $ 74 $ 30 $ 27 Interest cost 178 189 42 42 Expected return on assets (257 ) (251 ) (38 ) (39 ) Amortization of: Prior service cost (benefit) 3 3 (43 ) (44 ) Actuarial loss 142 106 20 15 Net periodic benefit cost $ 148 $ 121 $ 11 $ 1 Pension Benefits Nine Months Ended September 30, Other Postretirement Benefits Nine Months Ended September 30, 2015 (b) 2014 (b) 2015 (b) 2014 (b) Service cost $ 245 $ 218 $ 89 $ 90 Interest cost 533 561 125 144 Expected return on assets (770 ) (743 ) (113 ) (115 ) Amortization of: Prior service cost (benefit) 10 10 (130 ) (79 ) Actuarial loss 427 316 60 35 Net periodic benefit cost $ 445 $ 362 $ 31 $ 75 ______________ (a) For the three months ended September 30, 2015 , the cost for pension benefits and other postretirement benefits related to CENG were $2 million and $3 million , respectively. For the three months ended September 30, 2014, the cost for pension benefits and other postretirement benefits related to CENG were $2 million and $3 million , respectively. CENG amounts are included in the tables above. (b) For the nine months ended September 30, 2015 , the cost for pension benefits and other postretirement benefits related to CENG were $8 million and $8 million , respectively. For the period of April 1, 2014 to September 30, 2014, the cost for pension benefits and other postretirement benefits related to CENG were $5 million and $6 million , respectively. CENG amounts are included in the tables above.
Schedule Of Pension And Other Postretirement Benefit Costs	The amounts below represent Generation’s, ComEd’s, PECO’s, BGE’s and BSC's allocated portion of the pension and postretirement benefit plan costs, which were included in Property, plant and equipment within the respective Consolidated Balance Sheets and Operating and maintenance expense within the Consolidated Statement of Operations and Comprehensive Income during the three and nine months ended September 30, 2015 and 2014 . Three Months Ended September 30, Nine Months Ended September 30, Pension and Other Postretirement Benefit Costs 2015 2014 2015 2014 Generation (a) $ 67 $ 54 $ 200 $ 193 ComEd 52 33 155 129 PECO 10 7 29 28 BGE 16 17 49 50 BSC (b) 14 11 43 37 ______________ (a) For the three and nine months ended September 30, 2015 , the costs related to CENG were $5 million and $16 million , respectively. For the three months ended September 30, 2014, the costs related to CENG were $5 million . For the period of April 1, 2014 to September 30, 2014, the costs related to CENG were $11 million . CENG amounts are included in the table above. (b) These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO or BGE amounts above.
Schedule Of Defined Contributions	The following table presents the matching contributions to the savings plans during the three and nine months ended September 30, 2015 and 2014 : Three Months Ended September 30, Nine Months Ended September 30, Savings Plan Matching Contributions 2015 2014 2015 2014 Exelon (a) $ 51 $ 34 $ 111 $ 82 Generation (a) 27 17 60 41 ComEd 10 8 23 20 PECO 3 2 7 6 BGE 5 3 10 7 BSC (b) 6 4 11 8 _______________ (a) Includes $4 million and $8 million , respectively, related to CENG for the three and nine months ended September 30, 2015 . Includes $1 million related to CENG for the three months ended September 30, 2014 and for the period from April 1, 2014 to September 30, 2014. (b) These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These costs are not included in the Generation, ComEd, PECO or BGE amounts above.

Severance (Tables)

Severance (Tables)	9 Months Ended
	Sep. 30, 2015
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs	For the three and nine months ended September 30, 2015 and 2014 , the Registrants recorded the following severance costs (benefits) associated with these ongoing severance benefits within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income: Exelon Generation ComEd PECO BGE Three Months Ended September 30, 2015 $ (3 ) $ (3 ) $ — $ — $ — September 30, 2014 (2 ) (2 ) — — — Nine Months Ended September 30, 2015 $ 18 $ 17 $ 1 $ — $ — September 30, 2014 4 3 1 — —

Changes in Accumulated Other 40

Changes in Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2015
Changes in Accumulated Other Comprehensive Income [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following tables present changes in accumulated other comprehensive income (loss) (AOCI) by component for the nine months ended September 30, 2015 and 2014 : Nine Months Ended September 30, 2015 Gains and (Losses) on Hedging Activity Unrealized Gains and (Losses) on Marketable Securities Pension and Non-Pension Postretirement Benefit Plan Items Foreign Currency Items AOCI of Equity Investments Total Exelon (a) Beginning balance $ (28 ) $ 3 $ (2,640 ) $ (19 ) $ — $ (2,684 ) OCI before reclassifications (18 ) — (29 ) (17 ) — (64 ) Amounts reclassified from AOCI (b) 22 — 130 — — 152 Net current-period OCI 4 — 101 (17 ) — 88 Ending balance $ (24 ) $ 3 $ (2,539 ) $ (36 ) $ — $ (2,596 ) Generation (a) Beginning balance $ (18 ) $ 1 $ — $ (19 ) $ — $ (36 ) OCI before reclassifications (13 ) — — (17 ) — (30 ) Amounts reclassified from AOCI (b) 6 — — — — 6 Net current-period OCI (7 ) — — (17 ) — (24 ) Ending balance $ (25 ) $ 1 $ — $ (36 ) $ — $ (60 ) PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 ______________ (a) All amounts are net of tax. Amounts in parentheses represent a decrease in accumulated other comprehensive income. (b) See tables following changes in accumulated other comprehensive income tables for details about these reclassifications. Nine Months Ended September 30, 2014 Gains Unrealized Gains and (Losses) on Marketable Securities Pension and Non-Pension Postretirement Benefit Plan Items Foreign Currency Items AOCI of Equity Investments Total Exelon (a) Beginning balance $ 120 $ 2 $ (2,260 ) $ (10 ) $ 108 $ (2,040 ) OCI before reclassifications (14 ) (2 ) 240 (6 ) 11 229 Amounts reclassified from AOCI (b) (78 ) — 91 — (119 ) (106 ) Net current-period OCI (92 ) (2 ) 331 (6 ) (108 ) 123 Ending balance $ 28 $ — $ (1,929 ) $ (16 ) $ — $ (1,917 ) Generation (a) Beginning balance $ 114 $ 2 $ — $ (10 ) $ 108 $ 214 OCI before reclassifications (8 ) (3 ) — (6 ) 11 (6 ) Amounts reclassified from AOCI (b) (78 ) — — — (119 ) (197 ) Net current-period OCI (86 ) (3 ) — (6 ) (108 ) (203 ) Ending balance $ 28 $ (1 ) $ — $ (16 ) $ — $ 11 PECO (a) Beginning balance $ — $ 1 $ — $ — $ — $ 1 OCI before reclassifications — — — — — — Amounts reclassified from AOCI (b) — — — — — — Net current-period OCI — — — — — — Ending balance $ — $ 1 $ — $ — $ — $ 1 _______________ (a) All amounts are net of tax. Amounts in parentheses represent a decrease in accumulated other comprehensive income. (b) See tables following changes in accumulated other comprehensive income tables for details about these reclassifications.
Reclassification out of Accumulated Other Comprehensive Income	The following tables present amounts reclassified out of AOCI to Net income for Exelon and Generation during the three and nine months ended September 30, 2015 and 2014 . Three Months Ended September 30, 2015 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statements of Operations and Comprehensive Income Exelon Generation Gains (losses) on hedging activity Other cash flow hedges $ (4 ) $ (4 ) Interest expense (4 ) (4 ) Total before tax 1 1 Tax benefit $ (3 ) $ (3 ) Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 19 $ — Actuarial losses (b) (90 ) — (71 ) — Total before tax 28 — Tax benefit $ (43 ) $ — Net of tax Total Reclassifications for the period $ (46 ) $ (3 ) Net of Tax Nine Months Ended September 30, 2015 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statements of Operations and Comprehensive Income Exelon Generation Gains (losses) on hedging activity Terminated interest rate swaps (c) $ (26 ) $ — Other, net Energy related hedges 2 2 Operating revenues Other cash flow hedges (11 ) (11 ) Interest expense (35 ) (9 ) Total before tax 13 3 Tax benefit $ (22 ) $ (6 ) Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 57 $ — Actuarial losses (b) (270 ) — (213 ) — Total before tax 83 — Tax benefit $ (130 ) $ — Net of tax Total Reclassifications for the period $ (152 ) $ (6 ) Net of Tax Three months ended September 30, 2014 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statements of Operations and Comprehensive Income Exelon Generation Gains on hedging activity Energy related hedges $ 28 $ 28 Operating revenues 28 28 Total before tax (12 ) (12 ) Tax (expense) $ 16 $ 16 Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 19 $ — Actuarial losses (b) (61 ) — (42 ) — Total before tax 16 — Tax benefit $ (26 ) $ — Net of tax Equity investments Reversal of CENG equity method AOCI $ 5 $ 5 Gain on consolidation of CENG 5 5 Total before tax (2 ) (2 ) Tax benefit $ 3 $ 3 Net of tax Total reclassifications for the period $ (7 ) $ 19 Net of Tax Nine Months Ended September 30, 2014 Details about AOCI components Items reclassified out of AOCI (a) Affected line item in the Statements of Operations and Comprehensive Income Exelon Generation Gains on hedging activity Energy related hedges $ 130 $ 130 Operating revenues 130 130 Total before tax (52 ) (52 ) Tax (expense) $ 78 $ 78 Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 29 $ — Actuarial losses (b) (178 ) — (149 ) — Total before tax 58 — Tax benefit $ (91 ) $ — Net of tax Equity investments Sale of equity method investment $ 5 $ 5 Gain on consolidation of CENG Reversal of CENG equity method AOCI 193 193 Gain on consolidation of CENG 198 198 Total before tax (79 ) (79 ) Tax benefit $ 119 $ 119 Net of tax Total reclassifications for the period $ 106 $ 197 Net of Tax ____________ (a) All amounts are net of tax. Amounts in parentheses represent a decrease in net income. (b) This accumulated other comprehensive income component is included in the computation of net periodic pension and OPEB cost (see Note 14 — Retirement Benefits for additional details). (c) In January 2015, in connection with Generation's $750 million issuance of five-year Senior Unsecured Notes, Exelon terminated certain floating-to-fixed interest rate swaps. As the original forecasted transactions were a series of future interest payments over a ten year period, a portion of the anticipated interest payments are probable not to occur. As a result, $26 million of anticipated payments were reclassified from Accumulated OCI to Other, net in Exelon's Consolidated Statement of Operations and Comprehensive Income.
Schedule Of Other Comprehensive Income Loss Tax	The following table presents income tax expense (benefit) allocated to each component of other comprehensive income (loss) during the three and nine months ended September 30, 2015 and 2014 : Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Exelon Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 8 $ 8 $ 22 $ 11 Actuarial loss reclassified to periodic cost (35 ) (24 ) (105 ) (69 ) Pension and non-pension postretirement benefit plans valuation adjustment — 5 17 (153 ) Change in unrealized (gain) loss on cash flow hedges 3 15 (3 ) 62 Change in unrealized income on equity investments — 3 — 73 Change in unrealized loss on marketable securities — 1 — (1 ) Total $ (24 ) $ 8 $ (69 ) $ (77 ) Generation Change in unrealized loss on cash flow hedges $ 3 $ 13 $ 4 $ 57 Change in unrealized income on equity investments — 3 — 73 Change in marketable securities — 1 — (1 ) Total $ 3 $ 17 $ 4 $ 129

Earnings Per Share and Equity41

Earnings Per Share and Equity (Tables)	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Reconciliation of basic and diluted earnings per share	The following table sets forth the components of basic and diluted earnings per share and shows the effect of these stock options, performance share awards and restricted stock on the weighted average number of shares outstanding (in millions) used in calculating diluted earnings per share: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Net income attributable to common shareholders $ 629 $ 993 $ 1,959 $ 1,604 Average common shares outstanding — basic 913 861 879 860 Potentially dilutive effect of stock options, performance share awards and restricted stock 2 2 4 3 Average common shares outstanding — diluted 915 863 883 863

Commitments and Contingencies42

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2015
Commitments And Contingencies Tables Disclosure [Line Items]
Energy Commitments
Utility Energy Purchase Commitments
Fuel Purchase Commitments
Other Purchase Obligation
Commercial Commitments	The Registrants’ commercial commitments as of September 30, 2015 , representing commitments potentially triggered by future events were as follows: Exelon Generation ComEd PECO BGE Letters of credit (non-debt) (a) $ 1,078 $ 1,011 $ 18 $ 22 $ 1 Guarantees 5,823 (b) 3,159 (c) 205 (d) 188 (e) 263 (f) Nuclear insurance premiums (g) 3,057 3,057 — — — Total commercial commitments $ 9,958 $ 7,227 $ 223 $ 210 $ 264 ___________________ (a) Non-debt letters of credit maintained to provide credit support for certain transactions as requested by third parties. (b) Primarily reflects parental guarantees issued on behalf of Generation to allow the flexibility needed to conduct business with counterparties without having to post other forms of collateral. Also reflects guarantees issued to ensure performance under specific contracts, preferred securities of financing trusts, property leases, indemnifications, NRC minimum funding assurance requirements and miscellaneous guarantees. The estimated net exposure for obligations under commercial transactions covered by these guarantees was $650 million at September 30, 2015 , which represents the total amount Exelon could be required to fund based on September 30, 2015 market prices. (c) Primarily reflects guarantees issued to ensure performance under energy marketing and other specific contracts. The estimated net exposure for obligations under commercial transactions covered by these guarantees was $475 million at September 30, 2015 , which represents the total amount Generation could be required to fund based on September 30, 2015 market prices. (d) Primarily reflects full and unconditional guarantees of $200 million Trust Preferred Securities of ComEd Financing III, which is a 100% owned finance subsidiary of ComEd. (e) Primarily reflects full and unconditional guarantees of $178 million Trust Preferred Securities of PECO Trust III and IV, which are 100% owned finance subsidiaries of PECO. (f) Primarily reflects full and unconditional guarantees of $250 million Trust Preferred Securities of BGE Capital Trust II, which is a 100% owned finance subsidiary of BGE. (g) Represents the maximum amount that Generation would be required to pay for retrospective premiums in the event of nuclear disaster at any domestic site, including CENG sites, under the Secondary Financial Protection pool as required under the Price-Anderson Act as well as the current aggregate annual retrospective premium obligation that could be imposed by NEIL. See the Nuclear Insurance section within this note for additional details on Generation’s nuclear insurance premiums.
Accrued environmental liabilities	As of September 30, 2015 and December 31, 2014 , the Registrants had accrued the following undiscounted amounts for environmental liabilities in Other current liabilities and Other deferred credits and other liabilities within their respective Consolidated Balance Sheets: September 30, 2015 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 376 $ 309 Generation 63 — ComEd 269 268 PECO 41 39 BGE 3 2 December 31, 2014 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 347 $ 277 Generation 63 — ComEd 238 235 PECO 45 42 BGE 1 —
Exelon Generation Co L L C [Member] | Equity Method Investments [Member]
Commitments And Contingencies Tables Disclosure [Line Items]
Other Commitments	As of September 30, 2015 , Generation’s estimated commitment relating to its equity purchase agreements, including in-kind services contributions, is anticipated to be as follows: Total 2015 $ 38 2016 276 2017 23 2018 7 2019 2 Total $ 346

Supplemental Financial Inform43

Supplemental Financial Information (Tables)	9 Months Ended
	Sep. 30, 2015
Supplemental Financial Information [Abstract]
Components of non-operating income and expenses	The following tables provide additional information about the Registrants’ Consolidated Statements of Operations and Comprehensive Income for the three and nine months ended September 30, 2015 and 2014 : Three Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 39 $ 39 $ — $ — $ — Non-regulatory agreement units 18 18 — — — Net unrealized losses on decommissioning trust funds Regulatory agreement units (301 ) (301 ) — — — Non-regulatory agreement units (218 ) (218 ) — — — Regulatory offset to decommissioning trust fund-related activities (b) 207 207 — — — Total decommissioning-related activities (255 ) (255 ) — — — Investment income (expense) 4 1 — (1 ) 1 (c) Long-term lease income 4 — — — — AFUDC — Equity 6 — 1 1 4 Other (3 ) (3 ) 3 1 (1 ) Other, net $ (244 ) $ (257 ) $ 4 $ 1 $ 4 Nine Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 203 $ 203 $ — $ — $ — Non-regulatory agreement units 122 122 — — — Net unrealized losses on decommissioning trust funds Regulatory agreement units (385 ) (385 ) — — — Non-regulatory agreement units (274 ) (274 ) — — — Net unrealized gains on pledged assets Zion Station decommissioning 9 9 — — — Regulatory offset to decommissioning trust fund-related activities (b) 129 129 — — — Total decommissioning-related activities (196 ) (196 ) — — — Investment income (expense) 6 1 — (1 ) 3 (c) Long-term lease income 12 — — — — Interest income related to uncertain income tax positions — 1 — — — AFUDC — Equity 16 — 2 4 10 Terminated interest rate swaps (d) (26 ) — — — — Other 9 1 12 — — Other, net $ (179 ) $ (193 ) $ 14 $ 3 $ 13 Three Months Ended September 30, 2014 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 55 $ 55 $ — $ — $ — Non-regulatory agreement units 39 39 — — — Net unrealized losses on decommissioning trust funds Regulatory agreement units (107 ) (107 ) — — — Non-regulatory agreement units (41 ) (41 ) — — — Net unrealized gains on pledged assets Zion Station decommissioning 7 7 — — — Regulatory offset to decommissioning trust fund-related activities (b) 29 29 — — — Total decommissioning-related activities (18 ) (18 ) — — — Investment income (expense) — — — — 1 (c) Long-term lease income 4 — — — — Interest income related to uncertain income tax positions 25 27 AFUDC — Equity 5 — — 2 3 Other — (5 ) 4 — — Other, net $ 16 $ 4 $ 4 $ 2 $ 4 Nine Months Ended September 30, 2014 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 167 $ 167 $ — $ — $ — Non-regulatory agreement units 102 102 — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 126 126 — — — Non-regulatory agreement units 100 100 — — — Net unrealized gains on pledged assets Zion Station decommissioning 27 27 — — — Regulatory offset to decommissioning trust fund-related activities (b) (270 ) (270 ) — — — Total decommissioning-related activities 252 252 — — — Investment income (expense) 1 1 — (1 ) 5 (c) Long-term lease income 20 — — — — Interest income related to uncertain income tax positions 41 53 — — — AFUDC — Equity 17 — 3 5 9 Other 15 — 11 1 — Other, net $ 346 $ 306 $ 14 $ 5 $ 14 ________ (a) Includes investment income and realized gains and losses on sales of investments of the trust funds. (b) Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of net income taxes related to all NDT fund activity for those units. See Note 15 — Asset Retirement Obligations of the Exelon 2014 Form 10-K for additional information regarding the accounting for nuclear decommissioning. (c) Relates to the cash return on BGE’s rate stabilization deferral. See Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K for additional information regarding the rate stabilization deferral. (d) In January 2015, in connection with Generation's $750 million issuance of five-year Senior Unsecured Notes, Exelon terminated certain floating-to-fixed interest rate swaps. As the original forecasted transactions were a series of future interest payments over a ten year period, a portion of the anticipated interest payments are probable not to occur. As a result, $26 million of anticipated payments were reclassified from Accumulated OCI to Other, net in Exelon's Consolidated Statement of Operations and Comprehensive Income.
Components of depreciation, amortization and accretion, and other, net	The following tables provide additional information regarding the Registrants’ Consolidated Statements of Cash Flows for the nine months ended September 30, 2015 and 2014 : Nine Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE Depreciation, amortization, accretion and depletion Property, plant and equipment $ 1,648 $ 739 $ 471 $ 179 $ 216 Regulatory assets 131 — 57 19 55 Amortization of intangible assets, net 39 35 — — — Amortization of energy contract assets and liabilities (a) (20 ) (19 ) — — — Nuclear fuel (b) 841 841 — — — ARO accretion (c) 291 291 — — — Total depreciation, amortization, accretion and depletion $ 2,930 $ 1,887 $ 528 $ 198 $ 271 Nine Months Ended September 30, 2014 Exelon Generation ComEd PECO BGE Depreciation, amortization, accretion and depletion Property, plant and equipment $ 1,549 $ 686 $ 438 $ 169 $ 215 Regulatory assets 150 — 83 7 60 Amortization of intangible assets, net 33 33 — — — Amortization of energy contract assets and liabilities (a) 83 93 — — — Nuclear fuel (b) 790 790 — — — ARO accretion (c) 251 251 — — — Total depreciation, amortization, accretion and depletion $ 2,856 $ 1,853 $ 521 $ 176 $ 275 _________ (a) Included in Operating revenues or Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (b) Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (c) Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Nine Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 476 $ 200 $ 155 $ 29 $ 49 Loss from equity method investments 3 4 — — — Provision for uncollectible accounts 114 15 46 37 15 Stock-based compensation costs 102 — — — — Other decommissioning-related activity (a) (31 ) (31 ) — — — Energy-related options (b) 18 18 — — — Amortization of rate stabilization deferral 60 — — — 60 Amortization of debt fair value adjustment (34 ) (9 ) — — — Discrete impacts of EIMA (c) 101 — 101 — — Amortization of debt costs 43 12 3 2 2 Increase in inventory reserve 7 8 — — — Lower of cost or market inventory adjustment 15 15 — — — Other (18 ) (5 ) 7 1 (15 ) Total other non-cash operating activities $ 856 $ 227 $ 312 $ 69 $ 111 Changes in other assets and liabilities: Under/over-recovered energy and transmission costs $ 47 $ — $ 27 $ 12 $ 8 Other regulatory assets and liabilities (12 ) — 29 (4 ) (106 ) Cash deposits (d) (190 ) (190 ) — — — Other current assets (132 ) (143 ) 2 (23 ) (e) 55 Other noncurrent assets and liabilities (193 ) (92 ) (65 ) (3 ) — Total changes in other assets and liabilities $ (480 ) $ (425 ) $ (7 ) $ (18 ) $ (43 ) Non-cash investing and financing activities: Change in PPE related to the ARO update $ 811 $ 811 $ — — $ — $ — Change in capital expenditures not paid 59 (j) 48 (j) 62 (23 ) (14 ) Non-cash financing of capital projects $ 52 $ 52 $ — $ — $ — Indemnification of like-kind exchange position (f) — — 5 — — Long-term software licensing agreement (g) 95 — — — —
Cash Flow Supplemental Disclosures	Nine Months Ended September 30, 2015 Exelon Generation ComEd PECO BGE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 476 $ 200 $ 155 $ 29 $ 49 Loss from equity method investments 3 4 — — — Provision for uncollectible accounts 114 15 46 37 15 Stock-based compensation costs 102 — — — — Other decommissioning-related activity (a) (31 ) (31 ) — — — Energy-related options (b) 18 18 — — — Amortization of rate stabilization deferral 60 — — — 60 Amortization of debt fair value adjustment (34 ) (9 ) — — — Discrete impacts of EIMA (c) 101 — 101 — — Amortization of debt costs 43 12 3 2 2 Increase in inventory reserve 7 8 — — — Lower of cost or market inventory adjustment 15 15 — — — Other (18 ) (5 ) 7 1 (15 ) Total other non-cash operating activities $ 856 $ 227 $ 312 $ 69 $ 111 Changes in other assets and liabilities: Under/over-recovered energy and transmission costs $ 47 $ — $ 27 $ 12 $ 8 Other regulatory assets and liabilities (12 ) — 29 (4 ) (106 ) Cash deposits (d) (190 ) (190 ) — — — Other current assets (132 ) (143 ) 2 (23 ) (e) 55 Other noncurrent assets and liabilities (193 ) (92 ) (65 ) (3 ) — Total changes in other assets and liabilities $ (480 ) $ (425 ) $ (7 ) $ (18 ) $ (43 ) Non-cash investing and financing activities: Change in PPE related to the ARO update $ 811 $ 811 $ — — $ — $ — Change in capital expenditures not paid 59 (j) 48 (j) 62 (23 ) (14 ) Non-cash financing of capital projects $ 52 $ 52 $ — $ — $ — Indemnification of like-kind exchange position (f) — — 5 — — Long-term software licensing agreement (g) 95 — — — — Nine Months Ended September 30, 2014 Exelon Generation ComEd PECO BGE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 437 $ 193 $ 129 $ 28 $ 50 Equity method investments 20 20 — — — Provision for uncollectible accounts 96 10 9 39 38 Stock-based compensation costs 111 — — — — Other decommissioning-related activity (a) (102 ) (102 ) — — — Energy-related options (b) 92 92 — — — Amortization of regulatory asset related to debt costs 8 — — — — Amortization of rate stabilization deferral 50 — — — 50 Amortization of debt fair value adjustment (45 ) (17 ) — — — Discrete impacts from EIMA (c) (32 ) — (32 ) — — Amortization of debt costs 36 9 4 2 2 Merger-related commitments 44 44 — — — Other (17 ) 2 6 1 (11 ) Total other non-cash operating activities $ 698 $ 251 $ 116 $ 70 $ 129 Changes in other assets and liabilities: Under/over-recovered energy and transmission costs $ 53 $ — $ 63 $ (14 ) $ 6 Other regulatory assets and liabilities (63 ) — (14 ) (14 ) (89 ) Cash deposits (d) (280 ) (280 ) — — — Other current assets (78 ) 24 (9 ) (48 ) (e) 25 Other noncurrent assets and liabilities (168 ) (111 ) 22 1 (9 ) Total changes in other assets and liabilities $ (536 ) $ (367 ) $ 62 $ (75 ) $ (67 ) Non-cash investing and financing activities: Fair value of net assets recorded upon CENG consolidation $ 3,400 $ 3,400 $ — $ — $ — Change in PPE related to the ARO update (91 ) (91 ) Change in capital expenditures not paid (73 ) (j) (100 ) (j) 13 (13 ) 31 Issuance of equity units (h) 131 — — — — Uranium procurement (i) 70 70 — — — Indemnification of like-kind exchange position (f) — — 4 — — ____________ (a) Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 15 — Asset Retirement Obligations of the Exelon 2014 Form 10-K for additional information regarding the accounting for nuclear decommissioning. (b) Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations. (c) Reflects the change in distribution rates pursuant to EIMA, which allows for the recovery of costs by a utility through a pre-established performance-based formula rate tariff. See Note 5 — Regulatory Matters for more information. (d) Relates primarily to cash deposits made to ISOs/RTOs. (e) Relates primarily to prepaid utility taxes. (f) See Note 12 — Income Taxes for discussion of the like-kind exchange tax position. (g) Relates to a long-term software license agreement entered into on May 31, 2015. Exelon is required to make payments starting August of 2015 through May of 2024. See Note 11 — Debt and Credit Agreements for additional information.
Supplemental Balance Sheet Disclosures	The following tables provide additional information about assets of the Registrants as of September 30, 2015 and December 31, 2014 . September 30, 2015 Exelon Generation ComEd PECO BGE Property, plant and equipment: Accumulated depreciation and amortization $ 16,185 (a) $ 8,659 (a) $ 3,614 $ 3,058 $ 2,962 Accounts receivable: Allowance for uncollectible accounts 329 (c) 70 100 98 (c) 61 December 31, 2014 Exelon Generation ComEd PECO BGE Property, plant and equipment: Accumulated depreciation and amortization $ 14,742 (b) $ 7,612 (b) $ 3,432 $ 2,917 $ 2,868 Accounts receivable: Allowance for uncollectible accounts 311 (c) 60 84 100 (c) 67 _______ (a) Includes accumulated amortization of nuclear fuel in the reactor core of $3,093 million . (b) Includes accumulated amortization of nuclear fuel in the reactor core of $2,673 million . (c) Excludes the non-current allowance for uncollectible accounts related to PECO's installment plan receivables described below of $9 million and $7 million at September 30, 2015 and December 31, 2014 , respectively.

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2015
Segment Reporting Information [Line Items]
Analysis and reconciliation of reportable segment information	Months Ended September 30, 2015 and 2014 Generation (a) ComEd PECO BGE Other (b) Intersegment Eliminations Exelon Total revenues (c) : 2015 $ 14,841 $ 3,709 $ 2,386 $ 2,388 $ 1,007 $ (1,585 ) $ 22,746 2014 12,591 3,484 2,343 2,404 924 (1,573 ) 20,173 Intersegment revenues (d) : 2015 $ 567 $ 3 $ 1 $ 10 $ 1,003 $ (1,581 ) $ 3 2014 630 2 1 21 920 (1,574 ) — Net income (loss): 2015 $ 1,208 $ 339 $ 299 $ 212 $ (96 ) $ (3 ) $ 1,959 2014 1,037 335 255 156 (58 ) — 1,725 __________ (a) Generation includes the six power marketing reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. Intersegment revenues for Generation for the nine months ended September 30, 2015 include revenue from sales to PECO of $ 173 million and sales to BGE of $ 376 million in the Mid-Atlantic region, and sales to ComEd of $ 17 million in the Midwest. For the nine months ended September 30, 2014 , intersegment revenues for Generation include revenue from sales to PECO of $ 165 million and sales to BGE of $ 290 million in the Mid-Atlantic region, and sales to ComEd of $ 175 million in the Midwest region. (b) Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities. (c) For the nine months ended September 30, 2015 and 2014 , utility taxes of $ 79 million and $ 67 million , respectively, are included in revenues and expenses for Generation. For the nine months ended September 30, 2015 and 2014 , utility taxes of $ 180 million and $ 180 million , respectively, are included in revenues and expenses for ComEd. For the nine months ended September 30, 2015 and 2014 , utility taxes of $ 104 million and $ 99 million , respectively, are included in revenues and expenses for PECO. For the nine months ended September 30, 2015 and 2014 , utility taxes of $ 67 million and $ 64 million , respectively, are included in revenues and expenses for BGE. (d) Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income. Three Months Ended September 30, 2015 and 2014 Generation (a) ComEd PECO BGE Other (b) Intersegment Eliminations Exelon Total revenues (c) : 2015 $ 4,768 $ 1,376 $ 740 $ 725 $ 348 $ (556 ) $ 7,401 2014 4,412 1,222 693 697 305 (417 ) 6,912 Intersegment revenues (d) : 2015 $ 205 $ 1 $ 1 $ 3 $ 347 $ (555 ) $ 2 2014 112 1 — 3 302 (418 ) — Net income (loss): 2015 $ 332 $ 149 $ 90 $ 54 $ (36 ) $ (2 ) $ 587 2014 849 126 81 49 (31 ) — 1,074 Total assets: September 30, 2015 $ 46,479 $ 26,129 $ 10,072 $ 8,134 $ 16,256 $ (11,942 ) $ 95,128 December 31, 2014 45,348 25,392 9,943 8,078 9,794 (11,741 ) 86,814 __________ (a) Generation includes the six power marketing reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. Intersegment revenues for Generation for the three months ended September 30, 2015 include revenue from sales to PECO of $61 million and sales to BGE of $141 million in the Mid-Atlantic region, and sales to ComEd of $2 million in the Midwest. For the three months ended September 30, 2014 , intersegment revenues for Generation include revenue from sales to PECO of $28 million and sales to BGE of $83 million in the Mid-Atlantic region, and sales to ComEd of $1 million in the Midwest region. (b) Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities. (c) For the three months ended September 30, 2015 and 2014 , utility taxes of $28 million and $22 million , respectively, are included in revenues and expenses for Generation. For the three months ended September 30, 2015 and 2014 , utility taxes of $63 million and $61 million , respectively, are included in revenues and expenses for ComEd. For the three months ended September 30, 2015 and 2014 , utility taxes of $37 million and $34 million , respectively, are included in revenues and expenses for PECO. For the three months ended September 30, 2015 and 2014 , utility taxes of $23 million and $21 million , respectively, are included in revenues and expenses for BGE. (d) Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.
Analysis and reconciliation of reportable segment revenues for Generation	Nine Months Ended September 30, 2015 Nine Months Ended September 30, 2014 Revenues (b) Intersegment Total Revenues (b) Intersegment Total Mid-Atlantic (a) $ 4,475 $ 16 $ 4,491 $ 3,998 $ (14 ) $ 3,984 Midwest 3,630 3 3,633 3,302 11 3,313 New England 1,743 3 1,746 1,028 5 1,033 New York (a) 786 (8 ) 778 614 (1 ) 613 ERCOT 691 (4 ) 687 743 (2 ) 741 Other Power Regions (c) 891 (11 ) 880 1,027 (4 ) 1,023 Total Revenues for Reportable Segments 12,216 (1 ) 12,215 10,712 (5 ) 10,707 Other (d) 2,625 1 2,626 1,879 5 1,884 Total Generation Consolidated Operating Revenues $ 14,841 $ — $ 14,841 $ 12,591 $ — $ 12,591 __________ (a) On April 1, 2014, Generation assumed operational control of CENG's nuclear fleet. As a result, beginning on April 1, 2014, CENG's revenues are included on a fully consolidated basis. (b) Includes all wholesale and retail electric sales to third parties and affiliated sales to ComEd, PECO and BGE. (c) Other Power Regions includes the South, West and Canada. (d) Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $19 million increase to revenues and a $203 million decrease to revenues for the amortization of intangible assets related to commodity contracts for the nine months ended September 30, 2015 and 2014 , respectively, unrealized mark-to-market gains of $171 million and losses of $572 million for the nine months ended September 30, 2015 and 2014 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Three Months Ended September 30, 2015 Three Months Ended September 30, 2014 RNF (a) Intersegment RNF Total RNF RNF (a) Intersegment RNF Total RNF Mid-Atlantic $ 974 $ 17 $ 991 $ 921 $ 14 $ 935 Midwest 752 — 752 722 (6 ) 716 New England 145 (12 ) 133 120 (30 ) 90 New York 159 8 167 176 10 186 ERCOT 166 (55 ) 111 186 (77 ) 109 Other Power Regions (b) 167 (84 ) 83 157 (89 ) 68 Total Revenues net of purchased power and fuel for Reportable Segments 2,363 (126 ) 2,237 2,282 (178 ) 2,104 Other (c) (114 ) 126 12 250 178 428 Total Generation Revenues net of purchased power and fuel expense $ 2,249 $ — $ 2,249 $ 2,532 $ — $ 2,532 __________ (a) Includes purchases and sales from third parties and affiliated sales to ComEd, PECO and BGE. (b) Other Power Regions includes the South, West and Canada. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $4 million decrease to RNF and a $15 million increase to RNF for the amortization of intangible assets related to commodity contracts for the three months ended September 30, 2015 and 2014 , respectively, unrealized mark-to-market losses of $139 million and gains of $267 million for the three months ended September 30, 2015 and 2014 , respectively, and the elimination of intersegment revenues. Generation total revenues: Three Months Ended September 30, 2015 Three Months Ended September 30, 2014 Revenues from External Customers (a) Intersegment Revenues Total Revenues Revenues from External Customers (a) Intersegment Revenues Total Revenues Mid-Atlantic $ 1,622 $ 10 $ 1,632 $ 1,285 $ 4 $ 1,289 Midwest 1,150 1 1,151 1,062 (1 ) 1,061 New England 519 1 520 272 — 272 New York 254 (4 ) 250 230 2 232 ERCOT 317 (1 ) 316 303 (1 ) 302 Other Power Regions (b) 383 (7 ) 376 381 (6 ) 375 Total Revenues for Reportable Segments 4,245 — 4,245 3,533 (2 ) 3,531 Other (c) 523 — 523 879 2 881 Total Generation Consolidated Operating Revenues $ 4,768 $ — $ 4,768 $ 4,412 $ — $ 4,412 __________ (a) Includes all electric sales to third parties and affiliated sales to ComEd, PECO and BGE. (b) Other Power Regions includes the South, West and Canada. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $3 million decrease to revenues and a $22 million decrease to revenues for the amortization of intangible assets related to commodity contracts for the three months ended September 30, 2015 and 2014 , respectively, unrealized mark-to-market losses of $7 million and gains of $271 million for the three months ended September 30, 2015 and 2014 , respectively, and the elimination of intersegment revenues. Nine Months Ended September 30, 2015 Nine Months Ended September 30, 2014 RNF from External Customers (b) Intersegment RNF Total RNF RNF from External Customers (b) Intersegment RNF Total RNF Mid-Atlantic (a) $ 2,633 $ 30 $ 2,663 $ 2,610 $ (60 ) $ 2,550 Midwest 2,198 (3 ) 2,195 1,856 21 1,877 New England 416 (37 ) 379 362 (72 ) 290 New York (a) 471 27 498 289 24 313 ERCOT 344 (109 ) 235 457 (207 ) 250 Other Power Regions (c) 403 (210 ) 193 465 (216 ) 249 Total Revenues net of purchased power and fuel expense for Reportable Segments 6,465 — (302 ) 6,163 6,039 (510 ) 5,529 Other (d) 576 302 878 (519 ) 510 (9 ) Total Generation Revenues net of purchased power and fuel expense $ 7,041 — $ — $ 7,041 $ 5,520 $ — $ 5,520 __________ (a) On April 1, 2014, Generation assumed operational control of CENG's nuclear fleet. As a result, starting on April 1, 2014, CENG's revenue net of purchased power and fuel expense are included on a fully consolidated basis. (b) Includes purchases and sales from third parties and affiliated sales to ComEd, PECO and BGE. (c) Other Power Regions includes the South, West and Canada. (d) Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $20 million increase to RNF and a $78 million decrease to RNF for the amortization of intangible assets related to commodity contracts for the nine months ended September 30, 2015 and 2014 , respectively, unrealized mark-to-market gains of $258 million and losses of $477 million for the nine months ended September 30, 2015 and 2014 , respectively, and the elimination of intersegment revenue net of purchased power and fuel expense.

Basis of Presentation - Narrati

Basis of Presentation - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2015	Sep. 30, 2015	Sep. 30, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total interest expense to affiliates, net	$ 10	$ 11		$ 31	$ 31
Pretax decrease in operating and maintenance expense	(1,996)	(1,982)		(6,119)	(6,005)
Pretax increase in taxes other than income	310	306		908	887
Income (Loss) from Equity Method Investments		0		(3)	(20)
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions	(1)			(3)
Exelon Generation Co L L C [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Purchased power and fuel from affiliates	3	59		11	476
Total interest expense to affiliates, net	12	12		33	37
Pretax decrease in operating and maintenance expense	(1,088)	(1,114)		(3,399)	(3,308)
Pretax increase in taxes other than income	123	127		369	350
Income (Loss) from Equity Method Investments		1		(4)	(20)
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions	(1)			(4)
Exelon Generation Co L L C [Member] | Scenario Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Derivative, Gain (Loss) on Derivative, Net	52	12	$ 40
Baltimore Gas and Electric Company [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total interest expense to affiliates, net	4	4		11	12
Purchased power and fuel	170	216		664	808
Pretax decrease in operating and maintenance expense	(138)	(142)		(412)	(468)
Pretax increase in taxes other than income	$ 57	$ 55		$ 169	168
Income (Loss) from Equity Method Investments					$ 0

Variable Interest Entities - Na

Variable Interest Entities - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2015USD ($)VIE	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)VIE	Sep. 30, 2014USD ($)	Jun. 09, 2015USD ($)	Dec. 31, 2014USD ($)VIE	Aug. 18, 2014	Jul. 18, 2014USD ($)	Apr. 01, 2014USD ($)	Mar. 31, 2014
Variable Interest Entity [Line Items]
Number of Variable Interest Entities not consolidated by equity holders | VIE	8		8			6
Number Of Variable Interest Entities Consolidated | VIE	7		7			6
Guarantor Obligations, Current Carrying Value	$ 75,000,000		$ 75,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted	9,958,000,000		9,958,000,000
Note Receivable			$ 27,000,000
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage							67.00%			50.01%
Related Party Transaction Required Purchase Of Power Percentage			85.00%
Guarantor Obligations, Current Carrying Value	11,000,000		$ 11,000,000
Related Party Purchase Of Nuclear Output By Third Party Percentage			49.99%
Payables to affiliates	106,000,000		$ 106,000,000			$ 107,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted	7,227,000,000		7,227,000,000
Exelon Generation Co L L C [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Current Carrying Value	275,000,000		275,000,000
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Current Carrying Value					$ 275,000,000				$ 7,000,000
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Current Carrying Value	637,000,000		637,000,000
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	264,000,000		264,000,000
Baltimore Gas and Electric Company [Member] | RSB Bond Co LLC [Member]
Variable Interest Entity [Line Items]
Remittance of payments received from customers for rate stabilization to BondCo.	21,000,000	$ 21,000,000	63,000,000	$ 63,000,000
Constellation Energy Nuclear Group [Member]
Variable Interest Entity [Line Items]
Severance Benefits Obligations Balance									6,000,000
Severance Costs			1,000,000
Constellation Energy Nuclear Group [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Due from Affiliates	296,000,000		296,000,000						400,000,000
Distributed Energy Company [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Summarized Financial Information, Equity Excluding Noncontrolling Interests	$ 250,000,000		$ 250,000,000					$ 91,000,000
Financial Guarantee [Member] | Constellation Energy Nuclear Group [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted									165,000,000
Payment Guarantee [Member] | Constellation Energy Nuclear Group [Member]
Variable Interest Entity [Line Items]
Payables to affiliates									$ 245,000,000

Variable Interest Entities - Ca

Variable Interest Entities - Carrying Amounts and Classification of Consolidated VIE Assets and Liabilities (Details) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Current Assets	[1]	$ 1,108	$ 1,271
Non Current Assets	[1]	7,736	7,580
Total Assets	[1]	8,844	8,851
Current Liabilities	[1]	494	611
Non Current Liabilities	[1]	2,859	2,730
Total Liabilities	[1]	3,353	3,341
Assets		95,128	86,814
Total liabilities	[2]	67,839	62,681
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		8,190	8,160
Total liabilities		3,242	2,723
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Current Assets		1,057	1,242
Non Current Assets		7,728	7,566
Total Assets		8,785	8,808
Current Liabilities		408	526
Non Current Liabilities		2,773	2,600
Total Liabilities		3,181	3,126
Assets	[3]	46,479	45,348
Total liabilities	[3]	33,555	31,297
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		8,130	8,119
Total liabilities		3,070	2,507
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Current Assets		46	21
Non Current Assets		3	3
Total Assets		49	24
Current Liabilities		81	77
Non Current Liabilities		81	120
Total Liabilities		162	197
Assets	[4]	8,134	8,078
Total liabilities	[4]	5,289	5,325
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		49	24
Total liabilities		$ 162	$ 197
[1]	Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity.
[2]	Exelon’s consolidated assets include $8,190 million and $8,160 million at September 30, 2015 and December 31, 2014, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,242 million and $2,723 million at September 30, 2015 and December 31, 2014, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 3 — Variable Interest Entities.
[3]	Generation’s consolidated assets include $8,130 million and $8,119 million at September 30, 2015 and December 31, 2014, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,070 million and $2,507 million at September 30, 2015 and December 31, 2014, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 3 — Variable Interest Entities.
[4]	BGE’s consolidated assets include $49 million and $24 million at September 30, 2015 and December 31, 2014, respectively, of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $162 million and $197 million at September 30, 2015 and December 31, 2014, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 3 — Variable Interest Entities.

Variable Interest Entities - As

Variable Interest Entities - Assets and Liabilities of VIES which Creditors or Beneficiaries have no Recourse (Details) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 7,265	$ 1,878	$ 2,763	$ 1,609
Restricted cash		341	271
Accounts receivable, net
Customer		3,215	3,482
Other		1,107	1,227
Inventory
Materials and supplies		1,074	1,024
Other current assets		1,178	865
Mark-to-market derivative assets (current assets)		1,116	1,279
Total current assets		16,867	12,097
Property, plant and equipment, net		55,814	52,087
Nuclear decommissioning trust funds		10,103	10,537
Goodwill		2,672	2,672
Mark-to-market derivative assets		801	773
Other noncurrent assets		1,499	1,160
Total assets		95,128	86,814
Short-term borrowings		675	460
Long-term debt due within one year		897	1,802
Accounts payable		2,987	3,048
Accrued expenses		1,576	1,539
Mark-to-market derivative liabilities (current liabilities)		204	234
Other current liabilities		118	238
Other Liabilities, Current		1,017	1,123
Total current liabilities		7,847	8,762
Long-term debt		24,541	19,362
Asset retirement obligations		8,405	7,295
Pension obligation(a)		3,014	3,366
Energy Marketing Contract Liabilities, Noncurrent		136	211
Other noncurrent liabilities		2,231	2,147
Total deferred credits and other liabilities		34,803	33,909
Total liabilities	[1]	67,839	62,681
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		330	392
Restricted cash		193	117
Accounts receivable, net
Customer		186	297
Other		32	57
Inventory
Materials and supplies		180	172
Other current assets		48	33
Mark-to-market derivative assets (current assets)		116	171
Total current assets		1,085	1,239
Property, plant and equipment, net		4,932	4,638
Nuclear decommissioning trust funds		1,973	2,097
Goodwill		47	47
Mark-to-market derivative assets		53	44
Other noncurrent assets		100	95
Total noncurrent assets		7,105	6,921
Total assets		8,190	8,160
Long-term debt due within one year		108	87
Accounts payable		266	292
Accrued expenses		92	111
Mark-to-market derivative liabilities (current liabilities)		0	24
Other current liabilities		10	22
Other Liabilities, Current		15	25
Total current liabilities		491	561
Long-term debt		729	212
Asset retirement obligations		1,906	1,763
Pension obligation(a)	[2]	9	9
Energy Marketing Contract Liabilities, Noncurrent		42	51
Other noncurrent liabilities		65	127
Total deferred credits and other liabilities		2,751	2,162
Total liabilities		3,242	2,723
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		545	780	1,311	1,258
Restricted cash		242	158
Accounts receivable, net
Customer		2,056	2,295
Other		487	318
Inventory
Materials and supplies		863	847
Other current assets		960	658
Mark-to-market derivative assets (current assets)		1,116	1,276
Total current assets		7,050	7,638
Property, plant and equipment, net		24,982	22,945
Nuclear decommissioning trust funds		10,103	10,537
Goodwill		47	47
Mark-to-market derivative assets		764	771
Other noncurrent assets		881	731
Total assets	[3]	46,479	45,348
Short-term borrowings		21	36
Long-term debt due within one year		97	58
Accounts payable		1,676	1,759
Accrued expenses		835	886
Mark-to-market derivative liabilities (current liabilities)		182	214
Other current liabilities		118	238
Other Liabilities, Current		546	605
Total current liabilities		4,786	4,459
Long-term debt		7,964	6,709
Asset retirement obligations		8,254	7,146
Energy Marketing Contract Liabilities, Noncurrent		136	211
Other noncurrent liabilities		727	719
Total deferred credits and other liabilities		19,870	19,186
Total liabilities	[3]	33,555	31,297
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		330	392
Restricted cash		146	96
Accounts receivable, net
Customer		186	297
Other		32	57
Inventory
Materials and supplies		180	172
Other current assets		43	26
Mark-to-market derivative assets (current assets)		116	171
Total current assets		1,033	1,211
Property, plant and equipment, net		4,932	4,638
Nuclear decommissioning trust funds		1,973	2,097
Goodwill		47	47
Mark-to-market derivative assets		53	44
Other noncurrent assets		92	82
Total noncurrent assets		7,097	6,908
Total assets		8,130	8,119
Long-term debt due within one year		26	5
Accounts payable		266	292
Accrued expenses		88	108
Mark-to-market derivative liabilities (current liabilities)		0	24
Other current liabilities		10	22
Other Liabilities, Current		15	25
Total current liabilities		405	476
Long-term debt		643	81
Asset retirement obligations		1,906	1,763
Pension obligation(a)	[2]	9	9
Energy Marketing Contract Liabilities, Noncurrent		42	51
Other noncurrent liabilities		65	127
Total deferred credits and other liabilities		2,665	2,031
Total liabilities		3,070	2,507
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		27	64	$ 27	$ 31
Restricted cash		48	50
Accounts receivable, net
Customer		318	390
Other		77	82
Inventory
Materials and supplies		35	30
Other current assets		5	5
Total current assets		822	957
Property, plant and equipment, net		6,459	6,204
Other noncurrent assets		25	25
Total assets	[4]	8,134	8,078
Short-term borrowings		50	120
Long-term debt due within one year		77	75
Accounts payable		201	215
Accrued expenses		159	131
Other Liabilities, Current		32	51
Total current liabilities		797	846
Long-term debt		1,828	1,867
Asset retirement obligations		15	17
Other noncurrent liabilities		59	60
Total deferred credits and other liabilities		2,406	2,354
Total liabilities	[4]	5,289	5,325
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0	0
Restricted cash		46	21
Accounts receivable, net
Customer		0	0
Other		0	0
Inventory
Materials and supplies		0	0
Other current assets		0	0
Mark-to-market derivative assets (current assets)		0	0
Total current assets		46	21
Property, plant and equipment, net		0	0
Nuclear decommissioning trust funds		0	0
Goodwill		0	0
Mark-to-market derivative assets		0	0
Other noncurrent assets		3	3
Total noncurrent assets		3	3
Total assets		49	24
Long-term debt due within one year		77	75
Accounts payable		0	0
Accrued expenses		4	2
Mark-to-market derivative liabilities (current liabilities)		0	0
Other current liabilities		0	0
Other Liabilities, Current		0	0
Total current liabilities		81	77
Long-term debt		81	120
Asset retirement obligations		0	0
Pension obligation(a)		0	0
Energy Marketing Contract Liabilities, Noncurrent		0	0
Other noncurrent liabilities		0	0
Total deferred credits and other liabilities		81	120
Total liabilities		$ 162	$ 197
[1]	Exelon’s consolidated assets include $8,190 million and $8,160 million at September 30, 2015 and December 31, 2014, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,242 million and $2,723 million at September 30, 2015 and December 31, 2014, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 3 — Variable Interest Entities.
[2]	Includes CNEG retail gas pension obligation, which is presented as a net asset balance within the Prepaid Pension asset line item on Generation’s balance sheet. See Note 14 — Retirement Benefits for additional details.
[3]	Generation’s consolidated assets include $8,130 million and $8,119 million at September 30, 2015 and December 31, 2014, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,070 million and $2,507 million at September 30, 2015 and December 31, 2014, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 3 — Variable Interest Entities.
[4]	BGE’s consolidated assets include $49 million and $24 million at September 30, 2015 and December 31, 2014, respectively, of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $162 million and $197 million at September 30, 2015 and December 31, 2014, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 3 — Variable Interest Entities.

Variable Interest Entities - Su

Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Total assets	[1]	$ 384	$ 205
Total liabilities	[1]	76	52
Exelon's ownership interest in VIE	[1]	19	9
Other ownership interests in VIE	[1]	289	144
Assets Held-in-trust, Noncurrent		237	319
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	253	114
Total liabilities	[1]	10	3
Exelon's ownership interest in VIE	[1]	0	0
Other ownership interests in VIE	[1]	243	111
Commercial Agreement Variable Interest Entities [Member] | Scenario Adjustment [Member]
Variable Interest Entity [Line Items]
Total assets			392
Total liabilities			234
Other ownership interests in VIE			158
Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	131	91
Total liabilities	[1]	66	49
Exelon's ownership interest in VIE	[1]	19	9
Other ownership interests in VIE	[1]	46	33
Investments [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		27	13
Investments [Member] | Maximum [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Investments [Member] | Maximum [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		27	13
Contract Intangible Asset [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Contract Intangible Asset [Member] | Maximum [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Payment Guarantee [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		3	3
Payment Guarantee [Member] | Maximum [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		3	3
Asset Held In Trust Noncurrent [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	20	27
Asset Held In Trust Noncurrent [Member] | Maximum [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	20	27
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Assets Held-in-trust, Noncurrent		237	319
Payable to Zion Solutions	[3]	$ 217	$ 292
[1]	These items represent amounts on the unconsolidated VIE balance sheets, not on Exelon’s or Generation’s Consolidated Balance Sheets. These items are included to provide information regarding the relative size of the unconsolidated VIEs.
[2]	These items represent amounts on Exelon’s and Generation’s Consolidated Balance Sheets related to the asset sale agreement with ZionSolutions, LLC. The net assets pledged for Zion Station decommissioning include, gross pledged assets of $237 million and $319 million as of September 30, 2015 and December 31, 2014, respectively; offset by payables to ZionSolutions, LLC of $217 million and $292 million as of September 30, 2015 and December 31, 2014, respectively. These items are included to provide information regarding the relative size of the ZionSolutions, LLC unconsolidated VIE.
[3]	Excludes a liability recorded within Exelon’s and Generation’s Consolidated Balance Sheets related to the tax obligation on the unrealized activity associated with the Zion Station NDT Funds. The NDT Funds will be utilized to satisfy the tax obligations as gains and losses are realized.

Mergers, Acquisitions, and Di50

Mergers, Acquisitions, and Dispositions - Narrative (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		Jan. 21, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Sep. 30, 2015	Aug. 18, 2014	Jul. 18, 2014	Mar. 31, 2014	Jun. 05, 2013
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross					$ 28	$ 67
Business Combination, Integration Related Costs			$ 21	$ 32	47	57		$ 110
Business Acquisition, Transaction Costs			$ 226		$ 226			$ 226
Temporary Equity, Share Subscriptions			57.5		57.5			57.5
Line of Credit Facility, Maximum Borrowing Capacity	[1]		$ 8,500		$ 8,500			$ 8,500
Other noncurrent assets			1,499		1,499		$ 1,160	1,499
Proceeds from Issuance of Common Stock			1,870		1,868
Cost of Reimbursable Expense					40
Long-term Debt, Excluding Current Maturities			24,541		24,541		19,362	24,541
Net present value of settlement amount					430
Payments of Merger Related Costs, Financing Activities								116
Junior Subordinated Notes, Noncurrent												$ 1,150
Forward Contract Indexed to Issuer's Equity, Indexed Shares												23
Charitable Contributions [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination Proposed Customer Benefits Package			50		50			50
New Jersey Board Of Public Utilities [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			62		62			62
New Jersey Board Of Public Utilities [Member] | Energy Efficiency Program [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			15		15			15
Delaware Public Service Commission [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			40		40			40
Delaware Public Service Commission [Member] | Workforce Development [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			2		2			2
Delaware Public Service Commission [Member] | Energy Efficiency Program [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			2		2			2
District of Columbia Public Service Commission [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			78		78			78
District of Columbia Public Service Commission [Member] | Workforce Development [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			5		5			5
District of Columbia Public Service Commission [Member] | Rate Bill Credits [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			26		26			26
District of Columbia Public Service Commission [Member] | Charitable Contributions [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			19		19			19
District of Columbia Public Service Commission [Member] | OneTimeBillCredit [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			14		14			14
District of Columbia Public Service Commission [Member] | LowIncomeAssistance [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			16		16			16
Maryland Public Service Commission [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			66		66			66
Maryland Public Service Commission [Member] | Energy Efficiency Program [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			43.2		43.2			43.2
Maryland Public Service Commission [Member] | Green Sustainability Fund [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			14.4		14.4			14.4
Pepco Holdings [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross					6,900
Cash offered in exchange for each share of PHI stock										$ 27.25
Cost of Reimbursable Expense					5,400
Pepco Holdings [Member] | Minimum [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Exit Costs							259
Pepco Holdings [Member] | Maximum [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Exit Costs							293
Other Long-term Investments										$ 180
Exelon Generation Co L L C [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross					28	67
Business Combination, Integration Related Costs			9	3	24	4
Equity Method Investment, Ownership Percentage									67.00%		50.01%
Gain on Sale of Investments				329
Equity Method Investment, Net Sales Proceeds				615
Other noncurrent assets			881		881		731	881
Long-term Debt, Excluding Current Maturities			7,964		7,964		6,709	7,964
Proceeds from Sale of Productive Assets		$ 1,800
Baltimore Gas and Electric Company [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination, Integration Related Costs			2	1	5	1
Other noncurrent assets			25		25		25	25
Long-term Debt, Excluding Current Maturities			1,828		1,828		1,867	1,828
Gain (Loss) on Disposition of Assets			1		1
Commonwealth Edison Co [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination, Integration Related Costs			3	1	10	1
Other noncurrent assets			295		295		277	295
Long-term Debt, Excluding Current Maturities			5,435		5,435		5,698	5,435
PECO Energy Co [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Combination, Integration Related Costs			2	1	4	$ 1
Other noncurrent assets			36		36		34	36
Long-term Debt, Excluding Current Maturities			2,246		2,246		$ 2,246	$ 2,246
Gain (Loss) on Disposition of Assets			$ 0	$ 0	$ 1
[1]	Excludes additional credit facility agreements for Generation, ComEd, PECO and BGE with aggregate commitments of $50 million, $34 million, $34 million and $5 million, respectively, arranged with minority and community banks located primarily within ComEd’s, PECO’s and BGE’s service territories. These facilities expired on October 16, 2015 and were renewed at the same amount through October 14, 2016. These facilities are solely utilized to issue letters of credit. As of September 30, 2015, letters of credit issued under these agreements for Generation, ComEd, PECO and BGE totaled $7 million, $16 million, $21 million and $1 million, respectively.

Mergers, Acquisitions, and Di51

Mergers, Acquisitions, and Dispositions - Assets Disposition Table (Details) - USD ($) $ in Millions	Jan. 21, 2015	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014
Assets Disposition Table [Line Items]
Total assets held for sale			$ 4	$ 147
Accrued expenses			1,576	1,539
Other current liabilities			1,017	1,123
Exelon Generation Co L L C [Member]
Assets Disposition Table [Line Items]
Proceeds from Sale of Productive Assets	$ 1,800
Total assets held for sale			4	147
Accrued expenses			835	886
Other current liabilities			$ 546	$ 605
Asset Impairment Charges		$ 50
Proceed from sale of asset net of tax	$ 1,400

Regulatory Matters - Narrative

Regulatory Matters - Narrative (Details) $ in Millions		Oct. 20, 2015USD ($)	Oct. 19, 2015USD ($)	Sep. 10, 2015USD ($)	May. 27, 2015USD ($)	May. 19, 2015USD ($)	Apr. 24, 2015USD ($)	Apr. 15, 2015USD ($)	Mar. 27, 2015USD ($)	Dec. 08, 2014	Aug. 21, 2014USD ($)	Dec. 13, 2013USD ($)	Feb. 27, 2013	Aug. 31, 2010USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Dec. 31, 2014USD ($)	Sep. 30, 2015USD ($)	Jun. 11, 2014	Jun. 03, 2014USD ($)	Apr. 28, 2014	Aug. 23, 2013USD ($)	May. 17, 2013USD ($)
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															$ 6,779		$ 6,779		$ 6,923	$ 6,779
Rate of Return on Common Equity, Incentive Basis Points															0.50%		0.50%			0.50%
Regulatory assets															$ 6,000		$ 6,000		6,076	$ 6,000
Transmission Rate Formula, First Basis Points Credited																	0.50%
Business Combination, Integration Related Costs															21	$ 32	$ 47	$ 57		110
Regulatory Liabilities															4,545		4,545		4,860	4,545
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															1,145		$ 1,145		1,201	1,145
Public Utilities, Requested Rate Increase (Decrease), Amount								$ 50
Expected revenue adjustment for current year								$ 92
Expected revenue adjustment for prior year																			$ 142
Requested Debt and Equity Return on Distribution								7.05%
Requested ROE								9.14%											9.09%
Weighted Average Debt And Equity Return Electric Distribution																			7.02%
Weighted Average Debt And Equity Return								8.61%											8.62%
Gross transmission revenue requirement						$ 68
Transmission revenue true up								$ 18
Net transmission revenue requirement						$ 86
Estimated number of smart meters to be installed																					4,000,000
Smart Meters Installed																	1,600,000
Regulatory assets															913		$ 913		$ 852	913
Rate Of Return On Common Equity								11.50%
Business Combination, Integration Related Costs															3	1	10	1
Regulatory Liabilities															3,585		3,585		3,780	3,585
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															1,589		1,589		1,558	1,589
Spend on smart grid investments															155		$ 155			155
Public Utilities, Requested Rate Increase (Decrease), Amount				$ 127					$ 190
Public Utilities, Requested Rate Increase (Decrease), Percentage									10.95%
TotalSmartMetersInstalled																	1,700,000
SmartMeterFundingSGIG																	$ 200
Smart meter spend to date															579		579			579
Smart grid infrastructure spend to date															155		155			155
Total smart grid and smart meter investment grant amount															591		591			591
Regulatory assets															1,557		1,557		1,529	1,557
Amount of Regulatory Costs Not yet Approved															534		534			534
Business Combination, Integration Related Costs															2	1	4	1
Regulatory Liabilities															640		640		747	640
Total Projected Natural Gas LTIIP Spend					$ 275
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															742		742		724	742
Weighted Average Debt And Equity Return							8.46%																8.53%
Adjustment to Requested increase in electric revenues																								$ 83
Requested increase in gas revenues																									$ 24
Rate of return on common equity electric distribution												9.75%
Rate of return on common equity gas distribution												9.60%
Increase in electric delivery service revenue resulting from rate case settlement or order.												$ 34
Increase in gas delivery service revenue resulting from rate case settlement or order.												$ 12
Gross transmission revenue requirement							$ 13
Transmission revenue true up							3
Net transmission revenue requirement							$ 10
Estimated number of smart meters to be installed														2,000,000
Reimbursements received from the DOE														$ 200
Regulatory assets															485		485		510	485
Total Projected smart meter smart grid spend														$ 480
Rate Of Return On Common Equity							11.30%
Rate Of Return On Common Equity In Federal Energy Regulatory Committee Complaint										8.80%			8.70%
Business Combination, Integration Related Costs															2	1	5	1
Regulatory Liabilities															255		255		244	255
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
License Costs																	43
Other Commitment															3.5		3.5			3.5
Business Combination, Integration Related Costs															9	$ 3	24	$ 4
Exelon Generation Co L L C [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Minimum Purchase Obligation																						$ 25
Exelon Generation Co L L C [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Maximum Purchase Obligation																						$ 35
Under Recovered Distribution Service Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															240		240		371	240
Under Recovered Distribution Service Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[1]														240		240		371	240
CostRecoveryForSignificantOneTimeEvents																	56		85
UnderOverRecoveredDistributionServiceCosts																	184		286
Business Combination, Integration Related Costs																	13		19
RegulatoryAssetsDueToDeferredStormCosts																	43		66
Under Recovered Distribution Service Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															0		0		0	0
Under Recovered Distribution Service Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															0		0		0	0
AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															373		373		296	373
AMI Expenses [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															130		130		91	130
AMI Expenses [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															64		64		77	64
AMI Expenses [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															179		179		128	179
Energy Efficiency And Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															271		271		248	271
Energy Efficiency And Demand Response Programs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															0		0		0	0
Energy Efficiency And Demand Response Programs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															0		0		0	0
Energy Efficiency And Demand Response Programs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															271		271		248	271
Transmission Rate Formula [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Net regulatory asset															26		26		21	26
Net Regulatory Asset															26		26		21	26
Transmission Rate Formula [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Net regulatory asset															5		5		1	5
Net Regulatory Asset															5		5		1	5
Distribution formula Rate [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Net Regulatory Assets															240		240		371	240
Under Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															67		67		48	67
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[2]														33		33		33	33
ElectricTransmissionCostsUnderRecovery																	26		22
Business Combination, Integration Related Costs																	7		7
Under Recovered Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets															0		0		0	0
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[3]														34		$ 34		15	34
Business Combination, Integration Related Costs																			4
FERC Transmission Complaint [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Approved ROE													10.80%
Revenue Reduction											$ 14
Customer Refund Liability, Noncurrent											13
Customer Refund											13
Cash Collected											$ 27
Subsequent Event [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 68
Expected revenue adjustment for current year			8
Expected revenue adjustment for prior year			10
Revenue Reduction			$ 18
Scenario, Forecast [Member] | FERC Transmission Complaint [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenue Reduction		$ (11)
Over Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities															134		$ 134		84	134
Over Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities	[2]														46		46		19	46
Over Recovered Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities	[4]														70		70		58	70
Over Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities	[3]														$ 18		$ 18		$ 7	$ 18
[1]	As of September 30, 2015, ComEd’s regulatory asset of $240 million was comprised of $184 million for the applicable annual reconciliations and $56 million related to significant one-time events including $43 million of deferred storm costs and $13 million of Constellation merger and integration related costs. As of December 31, 2014, ComEd’s regulatory asset of $371 million was comprised of $286 million for the applicable annual reconciliations and $85 million related to significant one-time events, including $66 million of deferred storm costs and $19 million of Constellation merger and integration related costs. See Note 4 — Mergers, Acquisitions, and Dispositions of the Exelon 2014 Form 10-K for further information.
[2]	As of September 30, 2015, ComEd’s regulatory asset of $33 million included $26 million associated with transmission costs recoverable through its FERC approved formulate rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of September 30, 2015, ComEd’s regulatory liability of $46 million included $24 million related to over-recovered energy costs for hourly customers and $22 million associated with revenues received for renewable energy requirements. As of December 31, 2014, ComEd’s regulatory asset of $33 million included $4 million related to under-recovered energy costs for non-hourly customers, $22 million associated with transmission costs recoverable through its FERC approved formulate rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2014, ComEd’s regulatory liability of $19 million included $3 million related to over-recovered energy costs for hourly customers and $16 million associated with revenues received for renewable energy requirements.
[3]	As of September 30, 2015, BGE's regulatory asset of $34 million included $5 million associated with transmission costs recoverable through its FERC approved formula rate and $29 million related to under-recovered electric energy costs. As of September 30, 2015, BGE's regulatory liability of $18 million related to $9 million of over-recovered natural gas supply costs and $14 million of over-recovered energy costs, offset by $4 million of Constellation merger and integration costs and $1 million of abandonment costs to be recovered upon FERC approval. As of December 31, 2014, BGE's regulatory asset of $15 million included $10 million related to under-recovered electric energy costs, $4 million of Constellation merger and integration costs and $1 million of abandonment costs to be recovered upon FERC approval. As of December 31, 2014, BGE's regulatory liability of $7 million related to over-recovered natural gas supply costs.
[4]	(e)As of September 30, 2015, PECO's regulatory liability of $70 million included $33 million related to the DSP program, $31 million related to the over-recovered natural gas costs under the PGC and $6 million related to over-recovered electric transmission costs. As of December 31, 2014, PECO's regulatory liability of $58 million included $39 million related to the DSP program, $16 million related to the over-recovered natural gas costs under the PGC and $3 million related to the over-recovered electric transmission costs.

Regulatory Matters Regulatory M

Regulatory Matters Regulatory Matters - Schedule of Regulatory Assets (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended			12 Months Ended	17 Months Ended
		Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014	Dec. 31, 2014	Sep. 30, 2015
Regulatory Assets [Line Items]
Current		$ 779			$ 779			$ 847	$ 779
Noncurrent		6,000			6,000			6,076	6,000
Regulatory Assets		6,779			6,779			6,923	6,779
Business Combination, Integration Related Costs		21		$ 32	47		$ 57		110
Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3,138			3,138			3,256	3,138
Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,589			1,589			1,542	1,589
AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		373			373			296	373
Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		240			240			371	240
Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		50			50			57	50
Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		170			170			190	170
Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10			10			12	10
Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		106			106			116	106
Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		289			289			257	289
Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		54			54			67	54
Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		243			243			207	243
Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		67			67			48	67
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2			2			3	2
Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		23			23			30	23
Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		101			101			160	101
Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		271			271			248	271
Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6			6			8	6
ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1			1			2	1
Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		39			39			46	39
Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7			7			7	7
Commonwealth Edison Co [Member]
Regulatory Assets [Line Items]
Current		232			232			349	232
Noncurrent		913			913			852	913
Regulatory Assets		1,145			1,145			1,201	1,145
Business Combination, Integration Related Costs		3		1	10		1
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Commonwealth Edison Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		66			66			64	66
Commonwealth Edison Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		130			130			91	130
Commonwealth Edison Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[1]	240			240			371	240
UnderOverRecoveredDistributionServiceCosts					184			286
CostRecoveryForSignificantOneTimeEvents					56			85
RegulatoryAssetsDueToDeferredStormCosts					43			66
Business Combination, Integration Related Costs					13			19
Commonwealth Edison Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		48			48			53	48
Commonwealth Edison Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Commonwealth Edison Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Commonwealth Edison Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		66			66			74	66
Commonwealth Edison Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		256			256			219	256
Commonwealth Edison Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		54			54			67	54
Commonwealth Edison Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		243			243			207	243
Commonwealth Edison Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[2]	33			33			33	33
Business Combination, Integration Related Costs					7			7
ElectricTransmissionCostsUnderRecovery					26			22
Underrecovered Electric Supply cost								4
Commonwealth Edison Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Commonwealth Edison Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Commonwealth Edison Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Commonwealth Edison Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Commonwealth Edison Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Commonwealth Edison Co [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Commonwealth Edison Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9			9			22	9
Commonwealth Edison Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member]
Regulatory Assets [Line Items]
Current		32			32			29	32
Noncurrent		1,557			1,557			1,529	1,557
Regulatory Assets		1,589			1,589			1,558	1,589
Business Combination, Integration Related Costs		2		1	4		1
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,446			1,446			1,400	1,446
PECO Energy Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		64			64			77	64
PECO Energy Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2			2			4	2
PECO Energy Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		22			22			26	22
PECO Energy Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		32			32			37	32
PECO Energy Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
PECO Energy Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		23			23			14	23
PECO Energy Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Current		257			257			214	257
Noncurrent		485			485			510	485
Regulatory Assets		742			742			724	742
Business Combination, Integration Related Costs		2		$ 1	5		$ 1
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		77			77			78	77
Baltimore Gas and Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		179			179			128	179
Baltimore Gas and Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Baltimore Gas and Electric Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8			8			9	8
Baltimore Gas and Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Baltimore Gas and Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		10			10			12	10
Baltimore Gas and Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		18			18			16	18
Baltimore Gas and Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1	[3]		1	[3]		1	1	[3]
Baltimore Gas and Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Baltimore Gas and Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0			0			0	0
Baltimore Gas and Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[4]	34			$ 34			15	34
Business Combination, Integration Related Costs								4
Underrecovered Electric Supply cost					$ 29			10
Environmental Restoration Costs					5			1
Baltimore Gas and Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	[3]		2	[3]		3	2	[3]
Baltimore Gas and Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		23	[3]		23	[3]		30	23	[3]
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		101			101			160	101
Baltimore Gas and Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		271			271			248	271
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		6			6			8	6
Baltimore Gas and Electric Company [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1			1			2	1
Baltimore Gas and Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		4			4			7	4
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[5]	$ 7			7			7	$ 7
UnderRecoveredElectricRevenueDecoupling								$ 7
Over Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Underrecovered Electric Supply cost					$ 4
[1]	As of September 30, 2015, ComEd’s regulatory asset of $240 million was comprised of $184 million for the applicable annual reconciliations and $56 million related to significant one-time events including $43 million of deferred storm costs and $13 million of Constellation merger and integration related costs. As of December 31, 2014, ComEd’s regulatory asset of $371 million was comprised of $286 million for the applicable annual reconciliations and $85 million related to significant one-time events, including $66 million of deferred storm costs and $19 million of Constellation merger and integration related costs. See Note 4 — Mergers, Acquisitions, and Dispositions of the Exelon 2014 Form 10-K for further information.
[2]	As of September 30, 2015, ComEd’s regulatory asset of $33 million included $26 million associated with transmission costs recoverable through its FERC approved formulate rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of September 30, 2015, ComEd’s regulatory liability of $46 million included $24 million related to over-recovered energy costs for hourly customers and $22 million associated with revenues received for renewable energy requirements. As of December 31, 2014, ComEd’s regulatory asset of $33 million included $4 million related to under-recovered energy costs for non-hourly customers, $22 million associated with transmission costs recoverable through its FERC approved formulate rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2014, ComEd’s regulatory liability of $19 million included $3 million related to over-recovered energy costs for hourly customers and $16 million associated with revenues received for renewable energy requirements.
[3]	(g)In accordance with the MDPSC approved 2014 electric and natural gas distribution rate case orders, the recovery periods for these regulatory assets were revised, effective in January 2015.
[4]	As of September 30, 2015, BGE's regulatory asset of $34 million included $5 million associated with transmission costs recoverable through its FERC approved formula rate and $29 million related to under-recovered electric energy costs. As of September 30, 2015, BGE's regulatory liability of $18 million related to $9 million of over-recovered natural gas supply costs and $14 million of over-recovered energy costs, offset by $4 million of Constellation merger and integration costs and $1 million of abandonment costs to be recovered upon FERC approval. As of December 31, 2014, BGE's regulatory asset of $15 million included $10 million related to under-recovered electric energy costs, $4 million of Constellation merger and integration costs and $1 million of abandonment costs to be recovered upon FERC approval. As of December 31, 2014, BGE's regulatory liability of $7 million related to over-recovered natural gas supply costs.
[5]	(f)Represents the electric and gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of September 30, 2015, BGE had a regulatory asset of $7 million related to under-recovered electric revenue decoupling and a regulatory liability of $27 million related to over-recovered natural gas revenue decoupling. As of December 31, 2014, BGE had a regulatory asset of $7 million related to under-recovered electric revenue decoupling and a regulatory liability of $12 million related to over-recovered natural gas revenue decoupling.

Regulatory Matters Regulatory54

Regulatory Matters Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions		9 Months Ended		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Regulatory Liabilities [Line Items]
Current		$ 365		$ 310
Noncurrent		4,180		4,550
Regulatory Liabilities		4,545		4,860
Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		65		88
Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,538		2,879
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,545		1,566
Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		46		27
Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		9		10
Energy Efficiency Phase [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		38		32
Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		97		102
Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		30		49
Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		134		84
Over-Recovered Universal Service Fund Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3		2
Revenue Subject to Refund [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				3
Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		27		12
Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		13		6
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Current		69		44
Noncurrent		186		200
Regulatory Liabilities		255		244
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Baltimore Gas and Electric Company [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Baltimore Gas and Electric Company [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		203		223
Baltimore Gas and Electric Company [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Baltimore Gas and Electric Company [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Baltimore Gas and Electric Company [Member] | Energy Efficiency Phase [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Baltimore Gas and Electric Company [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Baltimore Gas and Electric Company [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Baltimore Gas and Electric Company [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[1]	18		7
Over recovered Natural Gas Supply Cost		9		7
Underrecovered Electric Supply cost		4
Baltimore Gas and Electric Company [Member] | Over-Recovered Universal Service Fund Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Baltimore Gas and Electric Company [Member] | Revenue Subject to Refund [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				0
Baltimore Gas and Electric Company [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[2]	27		12
Over Recovered Electric Revenue Decoupling		7
Over Recovered Natural Gas Revenue Decoupling		27		12
Baltimore Gas and Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		7		2
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Current		104		90
Noncurrent		536		657
Regulatory Liabilities		640		747
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
PECO Energy Co [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		388		490
PECO Energy Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
PECO Energy Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2		2
PECO Energy Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		9		10
PECO Energy Co [Member] | Energy Efficiency Phase [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		38		32
PECO Energy Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		97		102
PECO Energy Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		30		49
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[3]	70		58
Over recovered Natural Gas Supply Cost		31		16
Default Service Provider Program Costs		33		39
Over Recovered Electric Transmission Costs		6		3
PECO Energy Co [Member] | Over-Recovered Universal Service Fund Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3		2
PECO Energy Co [Member] | Revenue Subject to Refund [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				0
PECO Energy Co [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
PECO Energy Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3		2
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Current		144		125
Noncurrent		3,441		3,655
Regulatory Liabilities		3,585		3,780
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Commonwealth Edison Co [Member] | Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,150		2,389
Commonwealth Edison Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,342		1,343
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[4]	44		25
Commonwealth Edison Co [Member] | Dlc Program Cost [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Commonwealth Edison Co [Member] | Energy Efficiency Phase [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Commonwealth Edison Co [Member] | Electric Transmission And Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Commonwealth Edison Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Commonwealth Edison Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[5]	46		19
Over Recovered electric Supply Costs		24		3
Renewable Energy Requirement Revenue		22		16
Commonwealth Edison Co [Member] | Over-Recovered Universal Service Fund Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Commonwealth Edison Co [Member] | Revenue Subject to Refund [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities				3
Commonwealth Edison Co [Member] | Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		0		0
Commonwealth Edison Co [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		3		1
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Underrecovered Electric Supply cost		$ 29		10
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Underrecovered Electric Supply cost				$ 4
Pledged Assets For Zion Station Decommissioning [Member] | Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member]
Regulatory Liabilities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			$ 0
[1]	As of September 30, 2015, BGE's regulatory asset of $34 million included $5 million associated with transmission costs recoverable through its FERC approved formula rate and $29 million related to under-recovered electric energy costs. As of September 30, 2015, BGE's regulatory liability of $18 million related to $9 million of over-recovered natural gas supply costs and $14 million of over-recovered energy costs, offset by $4 million of Constellation merger and integration costs and $1 million of abandonment costs to be recovered upon FERC approval. As of December 31, 2014, BGE's regulatory asset of $15 million included $10 million related to under-recovered electric energy costs, $4 million of Constellation merger and integration costs and $1 million of abandonment costs to be recovered upon FERC approval. As of December 31, 2014, BGE's regulatory liability of $7 million related to over-recovered natural gas supply costs.
[2]	(f)Represents the electric and gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of September 30, 2015, BGE had a regulatory asset of $7 million related to under-recovered electric revenue decoupling and a regulatory liability of $27 million related to over-recovered natural gas revenue decoupling. As of December 31, 2014, BGE had a regulatory asset of $7 million related to under-recovered electric revenue decoupling and a regulatory liability of $12 million related to over-recovered natural gas revenue decoupling.
[3]	(e)As of September 30, 2015, PECO's regulatory liability of $70 million included $33 million related to the DSP program, $31 million related to the over-recovered natural gas costs under the PGC and $6 million related to over-recovered electric transmission costs. As of December 31, 2014, PECO's regulatory liability of $58 million included $39 million related to the DSP program, $16 million related to the over-recovered natural gas costs under the PGC and $3 million related to the over-recovered electric transmission costs.
[4]	(d)ComEd recovers the costs of its ICC-approved Energy Efficiency and Demand Response plan through a rider. Effective with a change to its rider in August 2015, ComEd will recover or refund any under or over-recoveries through the end of the Plan's fiscal year on May 31 over a twelve-month period beginning on June 1 of the following calendar year. Previously, ComEd's recovery or refund of under or over-recoveries through the end of the Plan's fiscal year on May 31 was over a nine-month period beginning on September 1 of the same calendar year.
[5]	As of September 30, 2015, ComEd’s regulatory asset of $33 million included $26 million associated with transmission costs recoverable through its FERC approved formulate rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of September 30, 2015, ComEd’s regulatory liability of $46 million included $24 million related to over-recovered energy costs for hourly customers and $22 million associated with revenues received for renewable energy requirements. As of December 31, 2014, ComEd’s regulatory asset of $33 million included $4 million related to under-recovered energy costs for non-hourly customers, $22 million associated with transmission costs recoverable through its FERC approved formulate rate, and $7 million of Constellation merger and integration costs to be recovered upon FERC approval. As of December 31, 2014, ComEd’s regulatory liability of $19 million included $3 million related to over-recovered energy costs for hourly customers and $16 million associated with revenues received for renewable energy requirements.

Regulatory Matters Regulatory55

Regulatory Matters Regulatory Matters - Purchase of Receivables Programs (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2015	Dec. 31, 2014
Purchase Of Receivables [Line Items]
Purchased receivables	[1]	$ 296	$ 290
Allowance for uncollectible accounts	[2]	(40)	(42)
Purchased receivables, net		256	248
Commonwealth Edison Co [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	[1]	137	139
Allowance for uncollectible accounts	[2]	(22)	(21)
Purchased receivables, net		115	118
PECO Energy Co [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	[1]	90	76
Allowance for uncollectible accounts	[2]	(8)	(8)
Purchased receivables, net		$ 82	68
Discount rate		1.00%
Baltimore Gas and Electric Company [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	[1]	$ 69	75
Allowance for uncollectible accounts	[2]	(10)	(13)
Purchased receivables, net		$ 59	$ 62
[1]	PECO’s gas POR program became effective on January 1, 2012 and includes a 1% discount on purchased receivables in order to recover the implementation costs of the program. The implementation costs were fully recovered and the 1% discount was reset to 0%, effective July 2015.
[2]	For ComEd and BGE, reflects the incremental allowance for uncollectible accounts recorded, which is in addition to the purchase discount. For ComEd, the incremental uncollectible accounts expense is recovered through its Purchase of Receivables with Consolidated Billing tariff.

Investment in Constellation E56

Investment in Constellation Energy Nuclear Group LLC - Narrative (Details) - USD ($)		3 Months Ended				9 Months Ended				17 Months Ended
		Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015	Jun. 09, 2015	Dec. 31, 2014	Aug. 18, 2014	Apr. 01, 2014	Mar. 31, 2014	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		$ 9,958,000,000				$ 9,958,000,000				$ 9,958,000,000
Revenues		7,401,000,000	[1]	$ 6,912,000,000	[1]	22,746,000,000	[2]	$ 20,173,000,000	[2]
Accumulated other comprehensive loss, net	[3]	(2,596,000,000)		(1,917,000,000)		(2,596,000,000)		(1,917,000,000)		(2,596,000,000)		$ (2,684,000,000)				$ (2,040,000,000)
Other Comprehensive Income (Loss), Tax		(24,000,000)		8,000,000		(69,000,000)		(77,000,000)
Revenue from Related Parties		2,000,000	[4]	0	[4]	3,000,000		0
Guarantor Obligations, Current Carrying Value		75,000,000				75,000,000				75,000,000
Business Combination, Integration Related Costs		21,000,000		32,000,000		47,000,000		57,000,000		110,000,000
Exelon Generation Co L L C [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage													67.00%		50.01%
Payments of Distributions to Affiliates						$ 2,368,000,000		440,000,000
Related Party Purchase Of Nuclear Output By Third Party Percentage						49.99%
Payables to affiliates		106,000,000				$ 106,000,000				106,000,000		107,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted		7,227,000,000				7,227,000,000				7,227,000,000
Total equity investment earnings (losses) - CENG								19,000,000
Revenues		4,768,000,000		4,412,000,000		14,841,000,000		12,591,000,000
Accumulated other comprehensive loss, net	[3]	(60,000,000)		11,000,000		(60,000,000)		11,000,000		(60,000,000)		$ (36,000,000)				$ 214,000,000
Other Comprehensive Income (Loss), Tax		3,000,000		17,000,000		$ 4,000,000		129,000,000
Related Party Transaction Required Purchase Of Power Percentage						85.00%
Revenue from Related Parties		206,000,000		112,000,000		$ 571,000,000		647,000,000
Guarantor Obligations, Current Carrying Value		11,000,000				11,000,000				11,000,000
Business Combination, Integration Related Costs		9,000,000		$ 3,000,000		24,000,000		4,000,000
Exelon Generation Co L L C [Member] | Constellation Energy Nuclear Group [Member]
Schedule of Equity Method Investments [Line Items]
Revenues		110,000,000				$ 416,000,000		17,000,000
Investment in CENG															$ 1,900,000,000
Accumulated other comprehensive loss, net															$ 116,000,000
Other Comprehensive Income (Loss), Tax								$ 77,000,000
Electricite De France LLC [Member]
Schedule of Equity Method Investments [Line Items]
Related Party Transaction Required Purchase Of Power Percentage						15.00%
Constellation Energy Nuclear Group [Member] | Exelon Generation Co L L C [Member]
Schedule of Equity Method Investments [Line Items]
Due from Affiliates		296,000,000				$ 296,000,000				$ 296,000,000				$ 400,000,000
Reduction To Net Income Attributable To Noncontrolling Interest		5,000,000				13,000,000
Net Income (Loss) Attributable to Parent		(75,000,000)				18,000,000
EDFI [Member] | Exelon Generation Co L L C [Member] | Constellation Energy Nuclear Group [Member]
Schedule of Equity Method Investments [Line Items]
Revenue from Related Parties		$ 108,000,000				$ 395,000,000
Payment Guarantee [Member] | Constellation Energy Nuclear Group [Member]
Schedule of Equity Method Investments [Line Items]
Payables to affiliates														245,000,000
Financial Guarantee [Member] | Constellation Energy Nuclear Group [Member]
Schedule of Equity Method Investments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted														165,000,000
Variable Interest Entity, Primary Beneficiary [Member] | Exelon Generation Co L L C [Member]
Schedule of Equity Method Investments [Line Items]
Guarantor Obligations, Current Carrying Value											$ 275,000,000			$ 7,000,000
[1]	(c)For the three months ended September 30, 2015 and 2014, utility taxes of $28 million and $22 million, respectively, are included in revenues and expenses for Generation. For the three months ended September 30, 2015 and 2014, utility taxes of $63 million and $61 million, respectively, are included in revenues and expenses for ComEd. For the three months ended September 30, 2015 and 2014, utility taxes of $37 million and $34 million, respectively, are included in revenues and expenses for PECO. For the three months ended September 30, 2015 and 2014, utility taxes of $23 million and $21 million, respectively, are included in revenues and expenses for BGE.
[2]	(d)Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.
[3]	All amounts are net of tax. Amounts in parentheses represent a decrease in accumulated other comprehensive income.
[4]	(d)Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.

Impairment of Long-Lived Asse57

Impairment of Long-Lived Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	May. 31, 2014	Oct. 31, 2000
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Tangible Asset Impairment Charges	$ 24
Estimated residual value of leased assets	639		$ 639		$ 685		$ 1,600
Capital Lease Net Investment In Direct Financing Leases Prepayments Received							$ 1,200
Proceeds From Lease Termination			0	$ 335
Operating and maintenance	1,996	$ 1,982	6,119	6,005
Exelon Generation Co L L C [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Carrying Amount Of Long Lived Assets To Be Written Down						$ 151
Impaired Assets Fair Value						$ 65
Tangible Asset Impairment Charges		86
Asset Impairment Charges				50
Operating and maintenance	$ 1,088	$ 1,114	$ 3,399	$ 3,308

Impairment of Long-lived Asse58

Impairment of Long-lived Assets - Components of the Net Investment in Long-term Leases (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014	Oct. 31, 2000
Property, Plant and Equipment [Abstract]
Estimated residual value of leased assets	$ 639	$ 685	$ 1,600
Less: unearned income	291	324
Net investment in long-term leases	$ 348	$ 361

Implications of Potential Ear59

Implications of Potential Early Plant Retirements Implications of Potential Early Plant Retirements (Details) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross		$ 1,074	$ 1,024
Property, Plant and Equipment, Net		55,814	52,087
Nuclear Plant [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross		135
Nuclear Fuel, Net of Amortization		373
Property, Plant and Equipment, Net		1,720
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress		60
Asset Retirement Obligation		(1,729)
Quad Cities [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross		49
Nuclear Fuel, Net of Amortization		186
Property, Plant and Equipment, Net		1,027
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress		29
Asset Retirement Obligation		(696)
Clinton [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross		56
Nuclear Fuel, Net of Amortization		122
Property, Plant and Equipment, Net		582
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress		8
Asset Retirement Obligation		(396)
Ginna [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross		30
Nuclear Fuel, Net of Amortization		65
Property, Plant and Equipment, Net		111
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress		23
Asset Retirement Obligation		(637)
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross		863	847
Property, Plant and Equipment, Net		24,982	22,945
Exelon Generation Co L L C [Member] | Nuclear Plant [Member]
Property, Plant and Equipment [Line Items]
Asset Retirement Obligation	[1]	$ (8,073)	$ (6,961)
[1]	Includes $7 million and $8 million as the current portion of the ARO at September 30, 2015 and December 31, 2014 respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets.

Fair Value of Financial Asset60

Fair Value of Financial Assets and Liabilities - Fair Value of Financial Liabilities Recorded at the Carrying Amount (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	$ 675	$ 460
Due to Related Parties, Noncurrent	648	648
Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	678	463
Long-term debt (including amounts due within one year)	25,438	21,164
SNF obligation	1,021	1,021
Due to Related Parties, Noncurrent	648	648
Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	678	463
Long-term debt (including amounts due within one year)	26,520	22,936
SNF obligation	820	833
Due to Related Parties, Noncurrent	663	648
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	3	3
Long-term debt (including amounts due within one year)	1,004	1,208
SNF obligation	0	0
Due to Related Parties, Noncurrent	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	675	448
Long-term debt (including amounts due within one year)	24,181	20,417
SNF obligation	820	833
Due to Related Parties, Noncurrent	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	0	12
Long-term debt (including amounts due within one year)	1,335	1,311
SNF obligation	0	0
Due to Related Parties, Noncurrent	663	648
Exelon Generation Co L L C [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	21	36
Exelon Generation Co L L C [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	21	36
Long-term debt (including amounts due within one year)	8,996	8,266
SNF obligation	1,021	1,021
Exelon Generation Co L L C [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	21	36
Long-term debt (including amounts due within one year)	9,313	8,822
SNF obligation	820	833
Exelon Generation Co L L C [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	0	0
Long-term debt (including amounts due within one year)	0	0
SNF obligation	0	0
Exelon Generation Co L L C [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	21	24
Long-term debt (including amounts due within one year)	7,978	7,511
SNF obligation	820	833
Exelon Generation Co L L C [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	0	12
Long-term debt (including amounts due within one year)	1,335	1,311
SNF obligation	0	0
Commonwealth Edison Co [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	604	304
Due to Related Parties, Noncurrent	206	206
Commonwealth Edison Co [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	604	304
Long-term debt (including amounts due within one year)	6,100	5,958
Due to Related Parties, Noncurrent	206	206
Commonwealth Edison Co [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	604	304
Long-term debt (including amounts due within one year)	6,731	6,788
Due to Related Parties, Noncurrent	206	213
Commonwealth Edison Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	0	0
Long-term debt (including amounts due within one year)	0	0
Due to Related Parties, Noncurrent	0	0
Commonwealth Edison Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	604	304
Long-term debt (including amounts due within one year)	6,731	6,788
Due to Related Parties, Noncurrent	0	0
Commonwealth Edison Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	0	0
Long-term debt (including amounts due within one year)	0	0
Due to Related Parties, Noncurrent	206	213
PECO Energy Co [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Due to Related Parties, Noncurrent	184	184
PECO Energy Co [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	2,246	2,246
Due to Related Parties, Noncurrent	184	184
PECO Energy Co [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	2,472	2,537
Due to Related Parties, Noncurrent	196	199
PECO Energy Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Due to Related Parties, Noncurrent	0	0
PECO Energy Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	2,472	2,537
Due to Related Parties, Noncurrent	0	0
PECO Energy Co [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	0	0
Due to Related Parties, Noncurrent	196	199
Baltimore Gas and Electric Company [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	50	120
Due to Related Parties, Noncurrent	258	258
Baltimore Gas and Electric Company [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	53	123
Long-term debt (including amounts due within one year)	1,905	1,942
Due to Related Parties, Noncurrent	258	258
Baltimore Gas and Electric Company [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	53	123
Long-term debt (including amounts due within one year)	2,118	2,178
Due to Related Parties, Noncurrent	261	236
Baltimore Gas and Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	3	3
Long-term debt (including amounts due within one year)	0	0
Due to Related Parties, Noncurrent	0	0
Baltimore Gas and Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	50	120
Long-term debt (including amounts due within one year)	2,118	2,178
Due to Related Parties, Noncurrent	0	0
Baltimore Gas and Electric Company [Member] | Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Lines of Credit, Fair Value Disclosure	0	0
Long-term debt (including amounts due within one year)	0	0
Due to Related Parties, Noncurrent	$ 261	$ 236

Fair Value of Financial Asset61

Fair Value of Financial Assets and Liabilities - Fair Value Measurements of Assets and Liabilities, Recurring and Nonrecurring (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	$ (360)	$ (403)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	1	3
Supplemental executive retirement plan fair value		1
Cash surrender value of life insurance investments excluded from Rabbi Trust investments	34	35
Derivative Liability, Noncurrent	(360)	(403)
Derivative Liability, Current	204	234
Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Rabbi Trust Investments [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Deferred Compensation Plan Assets	45	45
Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		46
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		46
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	6,545	1,119
FinancialAssetsFairValueDisclosure1	18,913	14,081
Deferred Compensation Liability, Current and Noncurrent	(95)	(107)
Financial Liabilities Fair Value Disclosure	(659)	(744)
FinancialAssetLiabilitiesNetFairValueDisclosure1	18,254	13,337
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	6,545	1,119
Deferred Compensation Liability, Current and Noncurrent	(95)	(107)
Financial Liabilities Fair Value Disclosure	(659)	(744)
Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(543)	(524)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(543)	(524)
Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6,050)	(6,694)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6,050)	(6,694)
Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,770)	(6,702)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,770)	(6,702)
Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(113)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(113)
Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(103)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(103)
Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(41)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(41)
Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(23)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(23)
Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(54)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(54)
Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10,137	10,542
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10,137	10,542
Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,103	4,630
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,103	4,630
Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		7
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		7
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,076	2,262
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,076	2,262
Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,701	5,242
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,701	5,242
Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,170	4,302
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,170	4,302
Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	368	245
Investments, Fair Value Disclosure		1
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	368	245
Investments, Fair Value Disclosure		1
Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Fair Value, Inputs, Level 1 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	353	434
Fair Value, Inputs, Level 1 [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Fair Value, Inputs, Level 1 [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		46
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		46
Fair Value, Inputs, Level 1 [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	6,545	1,119
FinancialAssetsFairValueDisclosure1	10,767	5,305
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	19	(9)
FinancialAssetLiabilitiesNetFairValueDisclosure1	10,786	5,296
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	6,545	1,119
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	19	(9)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(19)	(20)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(19)	(20)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,120)	(2,241)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,120)	(2,241)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(79)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(79)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,218)	(2,416)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,218)	(2,416)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(11)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(11)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(14)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(14)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(25)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(25)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,315	4,239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,315	4,239
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,274	2,423
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,274	2,423
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	6
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	6
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	11
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,872	3,035
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,872	3,035
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	46	47
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	46	47
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	301	208
Investments, Fair Value Disclosure		1
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	301	208
Investments, Fair Value Disclosure		1
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(155)	(114)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(6)	(1)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,625)	(1,667)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(85)	(201)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,865	1,982
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(14)	(18)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	8	17
Derivative Liability, Noncurrent		(195)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(195)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	2
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	2
Fair Value, Inputs, Level 2 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	435	800
Fair Value, Inputs, Level 2 [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(263)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(263)
Fair Value, Inputs, Level 2 [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	6
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	6
Fair Value, Inputs, Level 2 [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	57	89
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	57	89
Fair Value, Inputs, Level 2 [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7	8
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7	8
Fair Value, Inputs, Level 2 [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	10
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	10
Fair Value, Inputs, Level 2 [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	3
Fair Value, Inputs, Level 2 [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	75	110
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	75	110
Fair Value, Inputs, Level 2 [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	236	316
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	236	316
Fair Value, Inputs, Level 2 [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Fair Value, Inputs, Level 2 [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	46	47
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	46	47
Fair Value, Inputs, Level 2 [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Fair Value, Inputs, Level 2 [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,856)	(2,029)
Fair Value, Inputs, Level 2 [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(21)	(13)
Fair Value, Inputs, Level 2 [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(61)	(23)
Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(37)	(31)
Fair Value, Inputs, Level 2 [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(6,330)	(6,813)
Fair Value, Inputs, Level 2 [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(263)	(512)
Fair Value, Inputs, Level 2 [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	4,737	5,296
Fair Value, Inputs, Level 2 [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(17)	(27)
Fair Value, Inputs, Level 2 [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	14	48
Derivative Liability, Noncurrent		(532)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(532)
Fair Value, Inputs, Level 2 [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	5
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
FinancialAssetsFairValueDisclosure1	5,809	6,747
Deferred Compensation Liability, Current and Noncurrent	(95)	(107)
Financial Liabilities Fair Value Disclosure	(262)	(427)
FinancialAssetLiabilitiesNetFairValueDisclosure1	5,547	6,320
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	(95)	(107)
Financial Liabilities Fair Value Disclosure	(262)	(427)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(146)	(196)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(146)	(196)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,478)	(3,458)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,478)	(3,458)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(140)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(140)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,472)	(3,557)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,472)	(3,557)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(124)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(124)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(103)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(103)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(41)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(41)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(9)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(9)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(29)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(29)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,008	5,612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,008	5,612
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	1
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	1
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,831	2,023
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,831	2,023
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	57	89
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	57	89
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2	3
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	10
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	10
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	3
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	70	105
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	70	105
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	82	121
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	82	121
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,783	3,067
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,783	3,067
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	67	37
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	67	37
Investments, Fair Value Disclosure		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(664)	(992)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(55)	(22)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(37)	(31)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(2,561)	(3,465)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(140)	(284)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	2,037	2,757
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(3)	(9)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	6	31
Derivative Liability, Noncurrent		(295)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(295)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	245	172
Fair Value, Inputs, Level 3 [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
FinancialAssetsFairValueDisclosure1	2,337	2,029
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(416)	(308)
FinancialAssetLiabilitiesNetFairValueDisclosure1	1,921	1,721
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(416)	(308)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(416)	(308)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(416)	(308)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,452)	(995)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,452)	(995)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(44)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(44)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,080)	(729)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,080)	(729)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	814	691
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	814	691
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Investments, Fair Value Disclosure		0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,347)	(1,151)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(2,144)	(1,681)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(38)	(27)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	835	557
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Derivative Liability, Noncurrent		(42)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(42)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	3
Exelon Generation Co L L C [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(139)	(105)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash surrender value of life insurance investments excluded from Rabbi Trust investments	12	11
Derivative Liability, Noncurrent	(139)	(105)
Derivative Liability, Current	182	214
Exelon Generation Co L L C [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Exelon Generation Co L L C [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	225	405
FinancialAssetsFairValueDisclosure1	12,526	13,329
Deferred Compensation Liability, Current and Noncurrent	(29)	(31)
Financial Liabilities Fair Value Disclosure	(350)	(350)
FinancialAssetLiabilitiesNetFairValueDisclosure1	12,176	12,979
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	225	405
Deferred Compensation Liability, Current and Noncurrent	(29)	(31)
Financial Liabilities Fair Value Disclosure	(350)	(350)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(300)	(317)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(300)	(317)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,807)	(6,487)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,807)	(6,487)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,770)	(6,702)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,770)	(6,702)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(2)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(2)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(2)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(2)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(12)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(12)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(23)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(23)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(35)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(35)
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10,137	10,542
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10,137	10,542
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,103	4,630
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,103	4,630
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		7
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		7
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,076	2,262
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,076	2,262
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,701	5,242
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,701	5,242
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,170	4,302
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,170	4,302
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	368	245
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	368	245
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		16
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	225	405
FinancialAssetsFairValueDisclosure1	4,417	4,558
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	19	(9)
FinancialAssetLiabilitiesNetFairValueDisclosure1	4,436	4,549
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	225	405
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	19	(9)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(19)	(20)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(19)	(20)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,120)	(2,241)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,120)	(2,241)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(79)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(79)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,218)	(2,416)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,218)	(2,416)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(11)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(11)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(14)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(14)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(25)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(15)	(25)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,315	4,239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,315	4,239
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,274	2,423
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,274	2,423
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	598	612
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	6
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	6
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	11
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,872	3,035
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,872	3,035
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,142	996
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	16	16
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	16	16
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	301	208
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	301	208
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(155)	(114)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(6)	(1)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,625)	(1,667)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(85)	(201)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,865	1,982
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(14)	(18)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	8	17
Derivative Liability, Noncurrent		(195)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(195)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(263)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(263)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		15
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	16	16
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	16	16
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,856)	(2,029)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(21)	(12)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(24)	(18)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	(8)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(6,330)	(6,813)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(263)	(512)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	4,737	5,296
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(17)	(27)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	14	29
Derivative Liability, Noncurrent		(532)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(532)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	3
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
FinancialAssetsFairValueDisclosure1	5,772	6,742
Deferred Compensation Liability, Current and Noncurrent	(29)	(31)
Financial Liabilities Fair Value Disclosure	(196)	(240)
FinancialAssetLiabilitiesNetFairValueDisclosure1	5,576	6,502
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	(29)	(31)
Financial Liabilities Fair Value Disclosure	(196)	(240)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(146)	(196)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(146)	(196)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,478)	(3,458)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,478)	(3,458)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(140)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(140)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,472)	(3,557)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(2,472)	(3,557)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(13)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(13)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(2)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(2)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(12)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(21)	(12)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(9)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	(9)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(10)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6)	(10)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,008	5,612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,008	5,612
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	1
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	1
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,831	2,023
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,831	2,023
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	57	89
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	57	89
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2	3
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	95
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	407	438
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	10
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10	10
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	468	511
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	3
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	70	105
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	70	105
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	329	301
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	82	121
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	82	121
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	11
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,829	2,207
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,783	3,067
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,783	3,067
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	67	37
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	67	37
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(664)	(992)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(18)	(17)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	(8)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(2,561)	(3,465)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(140)	(284)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	2,037	2,757
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(3)	(9)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	6	12
Derivative Liability, Noncurrent		(295)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(295)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Economic hedge Interest and Currency [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
FinancialAssetsFairValueDisclosure1	2,337	2,029
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(173)	(101)
FinancialAssetLiabilitiesNetFairValueDisclosure1	2,164	1,928
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(173)	(101)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(173)	(101)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(173)	(101)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,209)	(788)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,209)	(788)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(44)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(44)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,080)	(729)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,080)	(729)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Derivatives Designated As Hedging Instruments Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Liabilities Interest and FX [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effect of Netting and Allocation of Collateral Interest Rate and FX Liabilities [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	814	691
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	814	691
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Domestic [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds, Foreign [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | CorporateDebtSecuritiesZoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | US Treasury And Government Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Government Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | State and Municipal Debt Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Fixed income Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities Zion Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Middle market lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	423	366
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalent Zion [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	245	239
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | MiddleMarketLending Zoin Decom [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	144	184
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Investments, Fair Value Disclosure		0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Investments, Fair Value Disclosure		0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	83
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,347)	(1,151)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate and Foreign Currency Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Designated as Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(2,144)	(1,681)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(38)	(27)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Effects of Netting and Allocation of Collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	835	557
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Proprietary Trading Interest and Currency Derivative [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Derivative Liability, Noncurrent		(42)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent		(42)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Other Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	32	3
PECO Energy Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	4	12
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash surrender value of life insurance investments excluded from Rabbi Trust investments	12	14
Cash and Cash Equivalents, Fair Value Disclosure	4	12
PECO Energy Co [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	8	9
FinancialAssetsFairValueDisclosure1	12	21
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(11)	(15)
Financial Liabilities Fair Value Disclosure	(11)	(15)
FinancialAssetLiabilitiesNetFairValueDisclosure1	1	6
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Investments, Fair Value Disclosure	8	9
Deferred Compensation Liability, Current and Noncurrent	(11)	(15)
Financial Liabilities Fair Value Disclosure	(11)	(15)
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	4	12
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	4	12
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	8	9
FinancialAssetsFairValueDisclosure1	12	21
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	12	21
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Investments, Fair Value Disclosure	8	9
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	0
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(11)	(15)
Financial Liabilities Fair Value Disclosure	(11)	(15)
FinancialAssetLiabilitiesNetFairValueDisclosure1	(11)	(15)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(11)	(15)
Financial Liabilities Fair Value Disclosure	(11)	(15)
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	0
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	25
Derivative Liability, Noncurrent	(221)	(187)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(221)	(187)
Derivative Liability, Current	22	20
Cash and Cash Equivalents, Fair Value Disclosure	0	25
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	25
Derivative Liability, Noncurrent	(243)	(207)
Deferred Compensation Liability, Current and Noncurrent	(7)	(8)
Financial Liabilities Fair Value Disclosure	(250)	(215)
FinancialAssetLiabilitiesNetFairValueDisclosure1	(250)	(190)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(243)	(207)
Deferred Compensation Liability, Current and Noncurrent	(7)	(8)
Financial Liabilities Fair Value Disclosure	(250)	(215)
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	25
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	25
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	25
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	0	25
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	0
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(7)	(8)
Financial Liabilities Fair Value Disclosure	(7)	(8)
FinancialAssetLiabilitiesNetFairValueDisclosure1	(7)	(8)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(7)	(8)
Financial Liabilities Fair Value Disclosure	(7)	(8)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	0
Derivative Liability, Noncurrent	(243)	(207)
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(243)	(207)
FinancialAssetLiabilitiesNetFairValueDisclosure1	(243)	(207)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(243)	(207)
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(243)	(207)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	68	103
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	68	103
Baltimore Gas and Electric Company [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
FinancialAssetsFairValueDisclosure1	73	108
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(4)	(5)
Financial Liabilities Fair Value Disclosure	(4)	(5)
FinancialAssetLiabilitiesNetFairValueDisclosure1	69	103
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Investments, Fair Value Disclosure	5	5
Deferred Compensation Liability, Current and Noncurrent	(4)	(5)
Financial Liabilities Fair Value Disclosure	(4)	(5)
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	68	103
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	68	103
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5	5
FinancialAssetsFairValueDisclosure1	73	108
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	73	108
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Investments, Fair Value Disclosure	5	5
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	0
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(4)	(5)
Financial Liabilities Fair Value Disclosure	(4)	(5)
FinancialAssetLiabilitiesNetFairValueDisclosure1	(4)	(5)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(4)	(5)
Financial Liabilities Fair Value Disclosure	(4)	(5)
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	0	0
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Nuclear Decommissioning [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	$ (34)	$ (5)

Fair Value of Financial Asset62

Fair Value of Financial Assets and Liabilities - Fair Value Assets Liabilities Measured On Recurring Basis Unobservable Input Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Exelon Generation Co L L C [Member]
Purchases, sales, issuances and settlements
Settlements	$ (1)	$ (1)	$ (8)	$ (4)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Gain (loss) reclassified to results of operating due to the settlement of derivative contracts	(229)	87	(623)	20
Decrease in Fair Value Adjustment	$ 19	45
Increase In Fair Value Adjustment			$ 44	19
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Earnings		77		(279)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	(48)		(83)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 0	0	$ 0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value					$ (1,921)	$ (1,770)	$ (1,721)
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	(90)	(79)	(72)	(257)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	97	148	338	455
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(17)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	69
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Value		1,066		1,066				$ 1,066	$ 843	$ 749
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses	180	164	540	(261)
Purchases, sales, issuances and settlements
Purchases	97	148	338	455
Sales	(23)	(33)	(76)	(66)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(17)
Settlements		(27)	(83)	(46)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers In		21	84	(9)
Transfers out of Level 3	(3)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Out		1	(38)	(26)
Ending balance		1,066		1,066
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held	180	164	540	(261)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	1	(2)	2	2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities	$ (15)	(41)	(16)	29
Fair Value, Inputs, Level 3 [Member] | Consolidation, Eliminations [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates		(3)	(20)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value							0	0	0
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3			0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses		0	0
Purchases, sales, issuances and settlements
Purchases		0	0
Sales		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements		0	0
Transfers into Level 3		0
Transfers out of Level 3		0
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held		0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable		0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities		3	$ 20
Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Consolidation, Eliminations [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ (5)			(14)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value						0		0		0
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses	0			0
Purchases, sales, issuances and settlements
Purchases	0			0
Sales	0			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0
Transfers into Level 3				0
Transfers out of Level 3	0			0
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held	0			0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0			0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities	$ 5			14
Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value							(1,928)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Earnings		77		(279)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	(48)		(83)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 5	3	$ 20	14
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value					(2,164)	(1,993)
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	(90)	(79)	(72)	(257)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	97	148	338	455
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	69
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Value		1,244		1,244				1,244	977	942
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses	180	164	540	(261)
Purchases, sales, issuances and settlements
Purchases	97	148	338	455
Sales	(23)	(33)	(76)	(66)
Settlements	(17)	(27)	(83)	(46)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers In		21	84	(9)
Transfers out of Level 3	(3)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Out		1	(38)	(26)
Ending balance		1,244		1,244
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held	180	164	540	(261)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	1	(2)	2	2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities	$ 0	0	$ 0	0
Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Earnings		1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0		4
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 5	3	$ 20	14
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value					(814)	(786)	(691)			(350)
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	40	83	186	331
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(17)			(46)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Value	814	644	814	644	814			644	592
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses	(1)	1	4	3
Purchases, sales, issuances and settlements
Purchases	40	83	186	331
Sales	0	(8)	(8)	(10)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(17)			(46)
Settlements		(27)	(83)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers In		0	4
Transfers into Level 3				0
Transfers out of Level 3	0			0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Out		0	0
Ending balance	814	644	814	644
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held	(1)	1	4	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities	$ 0		$ 0	0
Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member] | Pledged Assets For Zion Station Decommissioning [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Earnings		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 0	0	$ 0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value					(144)	(156)	(184)			(112)
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	5	53	16	95
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Value	144	166	144	166	144			166	133
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	5	53	16	95
Sales	(18)	(18)	(58)	(43)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0
Settlements		0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers In		0	0
Transfers into Level 3				0
Transfers out of Level 3	0			0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Out		0	0
Ending balance	144	166	144	166
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held	0	0	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	1	(2)	2	2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities	$ 0	0	$ 0	$ 0
Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member] | Derivative [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Earnings		76
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	(48)		(87)	(284)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 0	0	$ 0	$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value					(1,174)	(1,021)	(1,050)			(465)
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	(90)	79	(72)	(257)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	50	12	107	27
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	69
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Value	1,174	431	1,174	431	1,174			431	242
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses	181	163	536	(264)
Purchases, sales, issuances and settlements
Purchases	50	12	107	27
Sales	(5)	0	(10)	(6)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0
Settlements		0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers In		21	80
Transfers into Level 3				9
Transfers out of Level 3	(3)			(19)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Out		1	(38)
Ending balance	1,174	431	1,174	431
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held	181	163	536	(264)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0	0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities	$ 0	0	$ 0	$ 0
Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member] | Other Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings, Description				0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Earnings		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 0	0	$ 0	$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value					(32)	(30)	(3)			(15)
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	2	0	29	2
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Value	32	3	32	3	32			3	10
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	2	0	29	2
Sales	0	(7)	0	(7)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0
Settlements		0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers In		0	0
Transfers into Level 3				0
Transfers out of Level 3	0			(7)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Out		0	0
Ending balance	32	3	32	3
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held	0	0	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities	$ 0	0	$ 0	0
Fair Value, Inputs, Level 3 [Member] | Commonwealth Edison Co [Member] | Derivative [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value					(243)		$ (207)			$ (193)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Earnings		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0		0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 0	0	$ 0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value						$ (223)
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Value	(243)	(178)	(243)	(178)	$ (243)			$ (178)	$ (134)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0			0
Settlements		0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers In		0	0
Transfers into Level 3				0
Transfers out of Level 3	0			0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Out		0	0
Ending balance	(243)	(178)	(243)	(178)
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held	0	0	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Nuclear Decommissioning Payable	0	0	0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities	$ (20)	$ (44)	$ (36)	$ 15

Fair Value of Financial Asset63

Fair Value of Financial Assets and Liabilities Fair Value of Financial Assets and Liabilities - Narrative (Details)	Sep. 30, 2015USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward Power Basis	$ 3.3
Forward Gas Basis	0.32
Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 286,000,000

Fair Value of Financial Asset64

Fair Value of Financial Assets and Liabilities - Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Operating Revenue [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	$ (4)	$ 70	$ (31)	$ (260)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	198	142	538	(293)
Purchased Fuel and Electric [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(44)	6	(56)	(24)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(17)	21	(2)	29
Other, net [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	1	4	5
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(1)	1	4	3
Exelon Generation Co L L C [Member] | Operating Revenue [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(4)	70	(31)	(260)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	198	142	538	(293)
Exelon Generation Co L L C [Member] | Purchased Fuel and Electric [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(44)	6	(56)	(24)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(17)	21	(2)	29
Exelon Generation Co L L C [Member] | Other, net [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	1	4	5
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	$ (1)	1	$ 4	3
Fair Value, Inputs, Level 3 [Member] | Consolidation, Eliminations [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		$ 0
Nuclear Decommissioning Trust Fund Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings				5
Derivative [Member] | Fair Value, Inputs, Level 3 [Member] | Commonwealth Edison Co [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings				0
Pledged Assets For Zion Station Decommissioning [Member] | Fair Value, Inputs, Level 3 [Member] | Exelon Generation Co L L C [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings				0
Derivative [Member] | Fair Value, Inputs, Level 3 [Member] | Consolidation, Eliminations [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings				$ 0

Fair Value of Financial Asset65

Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Derivatives Fair Value Footnotes [Abstract]
Cash collateral excluded	$ 245,000,000
Fair Value, Inputs, Level 3 [Member]
Derivatives Fair Value Footnotes [Abstract]
Cash collateral excluded		$ 172,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	935,000,000	893,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Forward power price assets	11	15
Forward gas price assets	1.49	1.52
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Forward power price assets	96	120
Forward gas price assets	$ 9.86	$ 14.02
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Option Model Valuation Technique [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Volatility percentage	7.00%	8.00%
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Option Model Valuation Technique [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Volatility percentage	130.00%	257.00%
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ (6,000,000)	$ (15,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Forward power price assets	13	15
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Forward power price assets	89	117
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ (243,000,000)	$ (207,000,000)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Inputs [Abstract]
Marketability Reserve	3.50%	3.50%
Forward heat rate	(8.00%)	(8.00%)
Renewable factor	85.00%	86.00%
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Marketability Reserve	7.00%	8.00%
Forward heat rate	(9.00%)	(9.00%)
Renewable factor	126.00%	126.00%
All Regions excluding New England [Member] | Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Forward power price assets		$ 97
Forward gas price assets		8.14
All Regions excluding New England [Member] | Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Inputs [Abstract]
Forward power price assets		$ 76

Derivative Financial Instrume66

Derivative Financial Instruments - Summary of Interest Rate and Foreign Currency Hedges (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Gain (Loss) from Components Excluded from Assessment of Fair Value Hedge Effectiveness, Net		$ 2
Mark-to-market derivative assets (current assets)			$ 1,116	$ 1,279
Mark-to-market derivative assets			801	773
Derivative Liability, Current			204	234
Derivative Liability, Noncurrent			(360)	(403)
InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			9	15
Mark-to-market derivative assets			52	8
Derivative Liability, Current			9	1
Derivative Liability, Noncurrent			(12)	(114)
Total mark-to-market derivative net assets (liabilities)	[1]		40	(90)
Total mark-to-market derivative assets	[1]		61	23
Derivative Liability	[1]		(21)	(113)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			1,116	1,276
Mark-to-market derivative assets			764	771
Derivative Liability, Current			182	214
Derivative Liability, Noncurrent			(139)	(105)
Exelon Generation Co L L C [Member] | InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			9	12
Mark-to-market derivative assets			15	6
Derivative Liability, Current			9	1
Derivative Liability, Noncurrent			(12)	(3)
Total mark-to-market derivative net assets (liabilities)	[1]		3	16
Total mark-to-market derivative assets	[1]		24	18
Derivative Liability	[1]		(21)	(2)
Exelon Generation Co L L C [Member] | InterestRateAndForeignExchangeContract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			0	7
Mark-to-market derivative assets			0	1
Derivative Liability, Current			9	8
Derivative Liability, Noncurrent			(12)	(4)
Total mark-to-market derivative net assets (liabilities)			(21)	(4)
Total mark-to-market derivative assets			0	8
Derivative Liability			(21)	(12)
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Liability, Noncurrent			(4)
Exelon Generation Co L L C [Member] | Proprietary Trading [Member] | InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			10	20
Mark-to-market derivative assets			7	7
Derivative Liability, Current			10	14
Derivative Liability, Noncurrent			(5)	(9)
Total mark-to-market derivative net assets (liabilities)			2	4
Total mark-to-market derivative assets	[2]		17	27
Derivative Liability	[2]		(15)	(23)
Exelon Generation Co L L C [Member] | Collateral And Netting [Member] | InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			(12)	(22)
Mark-to-market derivative assets			(2)	(7)
Derivative Liability, Current			(16)	(25)
Derivative Liability, Noncurrent			5	10
Total mark-to-market derivative net assets (liabilities)	[1]		7	6
Total mark-to-market derivative assets	[1]		(14)	(29)
Derivative Liability	[1]		21	35
Exelon Generation Co L L C [Member] | Economic Hedging Instrument [Member] | InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			11	7
Mark-to-market derivative assets			10	5
Derivative Liability, Current			6	2
Derivative Liability, Noncurrent			0	0
Total mark-to-market derivative net assets (liabilities)			15	10
Total mark-to-market derivative assets			21	12
Derivative Liability			(6)	(2)
Corporate, Non-Segment [Member] | InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			0	3
Mark-to-market derivative assets			37	2
Derivative Liability, Current			0	0
Derivative Liability, Noncurrent			0	(111)
Total mark-to-market derivative net assets (liabilities)	[1]		37	(106)
Total mark-to-market derivative assets	[1]		37	5
Derivative Liability	[1]		0	(111)
Corporate, Non-Segment [Member] | InterestRateAndForeignExchangeContract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			0	3
Mark-to-market derivative assets			37	20
Derivative Liability, Current			0	0
Derivative Liability, Noncurrent			0	(29)
Total mark-to-market derivative net assets (liabilities)			37	(6)
Total mark-to-market derivative assets			37	23
Derivative Liability			0	(29)
Corporate, Non-Segment [Member] | Collateral And Netting [Member] | InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			0	0
Mark-to-market derivative assets			0	(19)
Derivative Liability, Current			0	0
Derivative Liability, Noncurrent			0	19
Total mark-to-market derivative net assets (liabilities)	[1]		0	0
Total mark-to-market derivative assets	[1]		0	(19)
Derivative Liability	[1]		0	19
Corporate, Non-Segment [Member] | Economic Hedging Instrument [Member] | InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)			0	0
Mark-to-market derivative assets			0	1
Derivative Liability, Current			0	0
Derivative Liability, Noncurrent			0	(101)
Total mark-to-market derivative net assets (liabilities)			0	(100)
Total mark-to-market derivative assets			0	1
Derivative Liability			$ 0	$ (101)
[1]	Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as accrued interest, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above.
[2]	Generation enters into interest rate derivative contracts to economically hedge risk associated with the interest rate component of commodity positions. The characterization of the interest rate derivative contracts within the proprietary trading activity in the above table is driven by the corresponding characterization of the underlying commodity position that gives rise to the interest rate exposure. Generation does not utilize proprietary trading interest rate derivatives with the objective of benefiting from shifts or changes in market interest rates.

Derivative Financial Instrume67

Derivative Financial Instruments - Summary of Gains and Losses on Hedges (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings		$ 0		$ 1
Fair Value Hedging [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net		16	$ (8)
Fair Value Hedging [Member] | Exelon Generation Co L L C [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[1]	0	(4)
Interest Expense [Member] | Fair Value Hedging [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[1]			13	$ (3)
Interest Expense [Member] | Fair Value Hedging [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net		13	(6)
Interest Expense [Member] | Fair Value Hedging [Member] | Exelon Generation Co L L C [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[1]			(1)	(12)
Interest Expense [Member] | Fair Value Hedging [Member] | Exelon Generation Co L L C [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[1]	$ 0	1
Gain (Loss) on Fair Value Hedges Recognized in Earnings			$ (4)		(12)
Designated as Hedging Instrument [Member] | Interest Expense [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[1]			8	6
Designated as Hedging Instrument [Member] | Interest Expense [Member] | Fair Value Hedging [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[1]			$ 0	$ 1
[1]	For the three and nine months ended September 30, 2015, the loss on Generation swaps included $0 million and $1 million realized in earnings, respectively, with an immaterial amount excluded from hedge effectiveness testing. For the three and nine months ended September 30, 2014, the loss on Generation swaps included $4 million and $12 million realized in earnings, respectively, with an $2 million amount excluded from hedge effectiveness testing.

Derivative Financial Instrume68

Derivative Financial Instruments Derivative Financial Instruments - Summary of Derivative Fair Value Balances (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Sep. 30, 2015		Sep. 30, 2014	Jun. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		$ 1,116				$ 1,279
Mark-to-market derivative assets (noncurrent assets)		801				773
Mark-to-market derivative liabilities (current liabilities)		(204)				(234)
Mark-to-market derivative liabilities (noncurrent liabilities)		(360)				(403)
Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		1,107				1,264
Mark-to-market derivative assets (noncurrent assets)		749				765
Total mark-to-market derivative assets		1,856				2,029
Mark-to-market derivative liabilities (current liabilities)		(195)				(235)
Mark-to-market derivative liabilities (noncurrent liabilities)		(348)				(289)
Total mark-to-market derivative liabilities		(543)				(524)
Total mark-to-market derivative net assets (liabilities)		1,313				1,505
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		1,116				1,276
Mark-to-market derivative assets (noncurrent assets)		764				771
Mark-to-market derivative liabilities (current liabilities)		(182)				(214)
Mark-to-market derivative liabilities (noncurrent liabilities)		(139)				(105)
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		3,958				4,992
Mark-to-market derivative assets (noncurrent assets)		2,372				1,821
Total mark-to-market derivative assets		6,330				6,813
Mark-to-market derivative liabilities (current liabilities)		(3,719)				(4,947)
Mark-to-market derivative liabilities (noncurrent liabilities)		(2,088)				(1,540)
Total mark-to-market derivative liabilities		(5,807)				(6,487)
Total mark-to-market derivative net assets (liabilities)		523				326
Current assets collateral offset		281				416
Noncurrent assets collateral offset		150				171
Current liabilities collateral offset		405				599
Noncurrent liabilities collateral offset		197				220
Total cash collateral received net of cash collateral posted		1,033				(1,406)
Exelon Generation Co L L C [Member] | Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		1,107	[1]			1,264	[2]
Mark-to-market derivative assets (noncurrent assets)		749	[1]			765	[2]
Total mark-to-market derivative assets		1,856	[1]			2,029	[2]
Mark-to-market derivative liabilities (current liabilities)		(173)	[1]			(215)	[2]
Mark-to-market derivative liabilities (noncurrent liabilities)		(127)	[1]			(102)	[2]
Total mark-to-market derivative liabilities		(300)	[1]			(317)	[2]
Total mark-to-market derivative net assets (liabilities)		1,556	[1]			1,712	[2]
Exelon Generation Co L L C [Member] | Proprietary Trading [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		221				456
Mark-to-market derivative assets (noncurrent assets)		42				56
Total mark-to-market derivative assets		263				512
Mark-to-market derivative liabilities (current liabilities)		(213)				(468)
Mark-to-market derivative liabilities (noncurrent liabilities)		(50)				(64)
Total mark-to-market derivative liabilities		(263)				(532)
Total mark-to-market derivative net assets (liabilities)		0				(20)
Exelon Generation Co L L C [Member] | Collateral And Netting [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		(3,072)				(4,184)
Mark-to-market derivative assets (noncurrent assets)		(1,665)				(1,112)
Total mark-to-market derivative assets	[3]	(4,737)				(5,296)
Mark-to-market derivative liabilities (current liabilities)		3,759				5,200
Mark-to-market derivative liabilities (noncurrent liabilities)		2,011				1,502
Total mark-to-market derivative liabilities	[3]	5,770				6,702
Total mark-to-market derivative net assets (liabilities)	[3]	1,033				1,406
Commonwealth Edison Co [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities (current liabilities)		(22)				(20)
Mark-to-market derivative liabilities (noncurrent liabilities)		(221)				(187)
Commonwealth Edison Co [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		0				0
Mark-to-market derivative assets (noncurrent assets)		0				0
Total mark-to-market derivative assets	[4]	0				0
Mark-to-market derivative liabilities (current liabilities)		(22)				(20)
Mark-to-market derivative liabilities (noncurrent liabilities)		(221)				(187)
Total mark-to-market derivative liabilities	[4]	(243)				(207)
Total mark-to-market derivative net assets (liabilities)	[4]	(243)				$ (207)
Scenario Adjustment [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net		$ 52		$ 12	$ 40
[1]	Current and noncurrent assets are shown net of collateral of $281 million and $150 million, respectively, and current and noncurrent liabilities are shown net of collateral of $405 million and $197 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $1,033 million at September 30, 2015.
[2]	Current and noncurrent assets are shown net of collateral of $416 million and $171 million, respectively, and current and noncurrent liabilities are shown net of collateral of $599 million and $220 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $1,406 million at December 31, 2014.
[3]	Exelon and Generation net all available amounts allowed under the derivative accounting guidance on the balance sheet. These amounts include unrealized derivative transactions with the same counterparty under legally enforceable master netting agreements and cash collateral. In some cases Exelon and Generation may have other offsetting exposures, subject to a master netting or similar agreement, such as trade receivables and payables, transactions that do not qualify as derivatives, letters of credit and other forms of non-cash collateral. These are not reflected in the table above.
[4]	Includes current and noncurrent liabilities relating to floating-to-fixed energy swap contracts with unaffiliated suppliers.

Derivative Financial Instrume69

Derivative Financial Instruments - Summary of AOCI related to Cash Flow Hedges (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended			12 Months Ended
		Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014	Dec. 31, 2013	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Derivative [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax				$ 12	$ 10		$ 52
Gain loss on interest rate swap treasury rate lock net of tax							13	$ 5
Income taxes		$ (115)		(422)	(805)		(646)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes		36		(291)	(371)		(290)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Derivative [Line Items]
Income taxes	[1]	1		(12)	13		(52)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes	[1]	1		(12)	3		(52)
Energy Related Hedges [Member]
Derivative [Line Items]
Effective portion of changes in fair value							(9)
Energy Related Hedges [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Cash Flow Hedge Accumulated Other Comprehensive Income Gain Loss		(25)		29	(25)		29	116		$ (18)
Energy Related Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member] | Operating Revenue One [Member]
Derivative [Line Items]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion					(2)		(78)
Energy Related Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member] | Interest Expense [Member]
Derivative [Line Items]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion					(8)
Energy Related Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member] | Other, net [Member]
Derivative [Line Items]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion					0
Cash Flow Hedging [Member]
Derivative [Line Items]
Effective portion of changes in fair value		(8)			(18)		(14)
Cash Flow Hedging [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Cash Flow Hedge Accumulated Other Comprehensive Income Gain Loss		(24)		28	(24)		28	$ 120		$ (28)
Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Operating Revenue One [Member]
Derivative [Line Items]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion					(2)		(78)
Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Interest Expense [Member]
Derivative [Line Items]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion					(8)
Cash Flow Hedging [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Other, net [Member]
Derivative [Line Items]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion					(16)
Total Cash Flow Hedges [Member]
Derivative [Line Items]
Cash Flow Hedge Accumulated Other Comprehensive Income Gain Loss		(24)		28	(24)		28		$ (19)		$ 47
Effective portion of changes in fair value				(3)
Total Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Operating Revenue One [Member]
Derivative [Line Items]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		(3)		(16)
Energy Related Hedges [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Cash Flow Hedge Accumulated Other Comprehensive Income Gain Loss		(25)	[2]	29	(25)	[2]	$ 29		$ (21)		$ 45
Effective portion of changes in fair value		(7)		0	$ (13)
Energy Related Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Exelon Generation Co L L C [Member] | Operating Revenue One [Member]
Derivative [Line Items]
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion		$ (3)		$ (16)
[1]	All amounts are net of tax. Amounts in parentheses represent a decrease in net income.
[2]	Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Nine Months Ended September 30, 2015 Income StatementLocation Total Cash FlowHedges Total Cash FlowHedges Accumulated OCI derivative gain at December 31, 2014 $(18) $(28) Effective portion of changes in fair value (13) (18) Reclassifications from accumulated OCI to net incomeOther, net — 16(a) Reclassifications from accumulated OCI to net incomeInterest Expense 8 8 Reclassifications from accumulated OCI to net incomeOperating Revenues (2) (2) Accumulated OCI derivative gain at September 30, 2015 $(25) $(24)

Derivative Financial Instrume70

Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		$ (6)	$ (11)
Unrealized Gain (Loss) on Derivatives				$ 363	$ (522)
Gain (Loss) on Sale of Derivatives	[1]			(26)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives				252	(509)
Gain (Loss) on Sale of Derivatives	[1]			0
Unrealized Gain (Loss) on Commodity Contracts		(7)	271	171	(572)
Operating Revenue [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net				(5)	(18)
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		(139)	256	358	(490)
Not Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		(139)	264	258	(482)
Not Designated as Hedging Instrument [Member] | Purchased Power And Fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		(132)	(4)	86	95
Not Designated as Hedging Instrument [Member] | Interest Expense [Member] | Corporate, Non-Segment [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		0	(8)	100	(8)
Not Designated as Hedging Instrument [Member] | Interest Expense [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		0	(3)	0	(5)
Not Designated as Hedging Instrument [Member] | Operating Revenue [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		(7)	271	172	(572)
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		(139)	263	252	(476)
Gain (Loss) on Sale of Derivatives		(97)	63	(98)	17
Unrealized Gain (Loss) on Commodity Contracts		(42)	200	350	(493)
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		(139)	263	252	(476)
Gain (Loss) on Sale of Derivatives		(97)	63	(98)	17
Unrealized Gain (Loss) on Commodity Contracts		(42)	200	350	(493)
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Purchased Power And Fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		(132)	(4)	86	95
Gain (Loss) on Sale of Derivatives		46	(23)	249	(207)
Unrealized Gain (Loss) on Commodity Contracts		(178)	19	(163)	302
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Interest Expense [Member] | Corporate, Non-Segment [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		0	0	0	0
Gain (Loss) on Sale of Derivatives		0	0	0	0
Unrealized Gain (Loss) on Commodity Contracts		0	0	0	0
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Interest Expense [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		0	0	0	0
Gain (Loss) on Sale of Derivatives		0	0	0	0
Unrealized Gain (Loss) on Commodity Contracts		0	0	0	0
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member] | Operating Revenue [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		(7)	267	166	(571)
Gain (Loss) on Sale of Derivatives		(143)	86	(347)	224
Unrealized Gain (Loss) on Commodity Contracts		136	181	513	(795)
Not Designated as Hedging Instrument [Member] | InterestRateandForeignExchange [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		0	(7)	106	(14)
Unrealized Gain (Loss) on Derivatives		2	(6)	48	(12)
Gain (Loss) on Sale of Derivatives		(2)	(1)	58	(2)
Not Designated as Hedging Instrument [Member] | InterestRateandForeignExchange [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		0	1	6	(6)
Unrealized Gain (Loss) on Derivatives		2	2	12	(4)
Gain (Loss) on Sale of Derivatives		(2)	(1)	(6)	(2)
Not Designated as Hedging Instrument [Member] | InterestRateandForeignExchange [Member] | Purchased Power And Fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		0	0	0	0
Unrealized Gain (Loss) on Derivatives		0	0	0	0
Gain (Loss) on Sale of Derivatives		0	0	0	0
Not Designated as Hedging Instrument [Member] | InterestRateandForeignExchange [Member] | Interest Expense [Member] | Corporate, Non-Segment [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		0	(8)	100	(8)
Unrealized Gain (Loss) on Derivatives		0	(8)	36	(8)
Gain (Loss) on Sale of Derivatives		0	0	64	0
Not Designated as Hedging Instrument [Member] | InterestRateandForeignExchange [Member] | Interest Expense [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		0	(3)	0	(5)
Unrealized Gain (Loss) on Derivatives		0	(3)	0	(5)
Gain (Loss) on Sale of Derivatives		0	0	0	0
Not Designated as Hedging Instrument [Member] | InterestRateandForeignExchange [Member] | Operating Revenue [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		0	4	6	(1)
Unrealized Gain (Loss) on Derivatives		2	5	12	1
Gain (Loss) on Sale of Derivatives		$ (2)	$ (1)	$ (6)	$ (2)
[1]	In January 2015, in connection with Generation's $750 million issuance of five-year Senior Unsecured Notes, Exelon terminated certain floating-to-fixed interest rate swaps. As the original forecasted transactions were a series of future interest payments over a ten year period, a portion of the anticipated interest payments are probable not to occur. As a result, $26 million of anticipated payments were reclassified from Accumulated OCI to Other, net in Exelon's Consolidated Statement of Operations and Comprehensive Income.

Derivative Financial Instrume71

Derivative Financial Instruments - Summary of Proprietary Trading Activities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ (6)	$ (11)
Operating Revenue [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net			$ (5)	$ (18)
Operating Revenue [Member] | Principal or Proprietary Transactions [Member]
Derivative [Line Items]
Proprietary Trading Activities Change In Fair Value	3	1	7	0
Proprietary Trading Activities Reclassification To Realized At Settlement	(3)	0	(9)	1
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	1	(2)	1
Commodity Contract [Member] | Operating Revenue [Member] | Principal or Proprietary Transactions [Member]
Derivative [Line Items]
Proprietary Trading Activities Change In Fair Value	(4)	(2)	5	(2)
Proprietary Trading Activities Reclassification To Realized At Settlement	(2)	(10)	(8)	(17)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ (6)	$ (12)	$ (3)	$ (19)

Derivative Financial Instrume72

Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015USD ($)
Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Total Credit Risk Exposure	$ 1
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	2,106
Credit derivative net exposure	$ 2,068
Credit Derivative, Collateral Held Directly or by Third Parties	38
Number of Credit Risk Derivatives Held	1
Derivative Credit Risk Valuation Adjustment, Derivative Assets	$ 444
Exelon Generation Co L L C [Member] | Financial institution [Member]
Derivative [Line Items]
Credit derivative net exposure	260
Exelon Generation Co L L C [Member] | Energy Cooperatives And Municipalities [Member]
Derivative [Line Items]
Credit derivative net exposure	908
Exelon Generation Co L L C [Member] | Investor Owned Utilities Marketers And Power Producers Credit Risk Exposure [Member]
Derivative [Line Items]
Credit derivative net exposure	867
Exelon Generation Co L L C [Member] | Other Credit Risk Exposure [Member]
Derivative [Line Items]
Credit derivative net exposure	33
Exelon Generation Co L L C [Member] | External Credit Rating, Investment Grade [Member]
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	1,463
Credit derivative net exposure	$ 1,445
Credit Derivative, Collateral Held Directly or by Third Parties	18
Number of Credit Risk Derivatives Held	1
Derivative Credit Risk Valuation Adjustment, Derivative Assets	$ 444
Exelon Generation Co L L C [Member] | External Credit Rating, Non Investment Grade [Member]
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	55
Credit derivative net exposure	$ 40
Credit Derivative, Collateral Held Directly or by Third Parties	15
Number of Credit Risk Derivatives Held	0
Derivative Credit Risk Valuation Adjustment, Derivative Assets	$ 0
Exelon Generation Co L L C [Member] | Risk Level, High [Member]
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	53
Credit derivative net exposure	$ 48
Credit Derivative, Collateral Held Directly or by Third Parties	5
Number of Credit Risk Derivatives Held	0
Derivative Credit Risk Valuation Adjustment, Derivative Assets	$ 0
Exelon Generation Co L L C [Member] | Risk Level, Low [Member]
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	535
Credit derivative net exposure	$ 535
Credit Derivative, Collateral Held Directly or by Third Parties	0
Number of Credit Risk Derivatives Held	0
Derivative Credit Risk Valuation Adjustment, Derivative Assets	$ 0

Derivative Financial Instrume73

Derivative Financial Instruments - Summary of Credit Risk Related Contingent Features (Details) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Derivative, Collateral, Obligation to Return Cash		$ 13
Derivative, Collateral, Obligation to Return Securities		25
ReNewAble Energy Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value of Collateral		19
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Aggregate fair value of derivatives with credit-risk-related contingent features		(1,533)	$ (1,433)
Contractual right of offset related to derivative assets		1,302	1,140
Net liability position after contractual right of offset	[1]	(231)	(293)
Derivative, Collateral, Right to Reclaim Cash		1,065	1,497
Derivative, Collateral, Right to Reclaim Securities		474	672
Derivative, Collateral, Obligation to Return Cash		21	77
Derivative, Collateral, Obligation to Return Securities		$ 40	$ 24
[1]	Amount represents the net fair value of out-of-the-money derivative contracts containing credit-risk related contingent features after considering the mitigating effects of offsetting positions under master netting arrangements and reflects the actual net liability upon which any potential contingent collateral obligations would be based.

Derivative Financial Instrume74

Derivative Financial Instruments - Narrative (Details) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)MWh		Sep. 30, 2014USD ($)MWh	Jun. 30, 2015USD ($)	Dec. 31, 2014USD ($)
Derivative [Line Items]
Income taxes		$ 115	$ 422	$ 805		$ 646
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax			28	$ 2		130
Hypothetical Increase In Interest Rates				0.50%
Mark-to-market derivative assets (noncurrent assets)		801		$ 801				$ 773
Hypothetical increase in interest rates associated with variable-rate debt				3
Ineffective portion recognized in income		3	6	11	[1]	14
Mark-to-market derivative liabilities (noncurrent liabilities)		360		360				403
Cash collateral held		13		13
Letters of credit collateral posted		25		25
Interest Rate Fair Value Hedge Asset at Fair Value		40		40
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount of Pre-issuance Interest Rate Cash Flow Hedge Derivatives		752		752
ReNewAble Energy Contract [Member]
Derivative [Line Items]
Derivative Asset, Fair Value of Collateral		19		19
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes		(36)	291	$ 371		$ 290
Proprietary trading activities volume | MWh				3,006,000		8,129,000
Mark-to-market derivative assets (noncurrent assets)		764		$ 764				771
Mark-to-market derivative liabilities (noncurrent liabilities)		139		139				105
Cash collateral received not offset against net derivative positions		4		4				8
Credit exposure under natural gas supply and management agreements		2,106		2,106
Cash collateral posted		1,065		1,065				1,497
Letters of credit collateral posted		474		474				672
Cash collateral held		21		21				77
Letters of credit collateral posted		40		40				24
Incremental collateral for loss of investment grade credit rating		2,100		2,100				2,400
Interest Rate Fair Value Hedge Asset at Fair Value		3		3
Commonwealth Edison Co [Member]
Derivative [Line Items]
Income taxes		99	84	226		$ 221
Mark-to-market derivative liabilities (noncurrent liabilities)		221		221				187
PECO Energy Co [Member]
Derivative [Line Items]
Income taxes		37	25	$ 122		82
Estimated percentage of natural gas purchases hedged				30.00%
Incremental collateral for loss of investment grade credit rating		18		$ 18
Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Income taxes		35	31	141		103
Total		1		1
Incremental collateral for loss of investment grade credit rating		28		$ 28
Minimum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months				97.00%
Expected Generation Hedged In Year Two				81.00%
Expected generation hedged in year three				51.00%
Minimum [Member] | Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Estimated percentage of natural gas purchases hedged				10.00%
Maximum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months				100.00%
Expected Generation Hedged In Year Two				84.00%
Expected generation hedged in year three				54.00%
Maximum [Member] | Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Estimated percentage of natural gas purchases hedged				20.00%
Interest Rate Swap [Member] | Derivative [Member]
Derivative [Line Items]
Derivative, Notional Amount		800		$ 800
Interest Rate Swap [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities (noncurrent liabilities)		4		4
Foreign Exchange Contract [Member] | Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount		99		99
Fair Value Hedging [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount		800		800				1,450
Derivative, Gain (Loss) on Derivative, Net		16	(8)
Mark-to-market derivative assets (noncurrent assets)		37		37				29
Fair Value Hedging [Member] | Interest Rate Swap [Member] | Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount								550
Derivative, Gain (Loss) on Derivative, Net	[1]	0	(4)
Mark-to-market derivative assets (noncurrent assets)								7
Cash Flow Hedging [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount of Pre-issuance Interest Rate Cash Flow Hedge Derivatives								$ 400
Other Solar Projects [Member] | Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional amounts on forward starting interest rate swaps		25		25
Mark-to-market derivative liabilities (noncurrent liabilities)		3		3
Other Solar Projects [Member] | Cash Flow Hedging [Member] | Interest Rate Swap [Member] | Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount		26		26
PHI Merger [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net				64
PHI Merger [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount							$ 2,400
ExGen Texas Power [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount		501		501
ExGen Texas Power [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities (noncurrent liabilities)		16		16
ExGen Texas Power [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member] | Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount		200		200
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member] | Interest Rate Contract [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax				26
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative [Line Items]
Income taxes	[2]	(1)	12	(13)		52
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes	[2]	(1)	$ 12	(3)		$ 52
Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		24		24
PECO Energy Co Affiliate [Member] | PECO Energy Co [Member]
Derivative [Line Items]
Net receivable from affiliated electric and gas utility		33		33
Baltimore Gas And Electric Company Affiliate [Member] | Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Net receivable from affiliated electric and gas utility		$ 27		$ 27
[1]	For the three and nine months ended September 30, 2015, the loss on Generation swaps included $0 million and $1 million realized in earnings, respectively, with an immaterial amount excluded from hedge effectiveness testing. For the three and nine months ended September 30, 2014, the loss on Generation swaps included $4 million and $12 million realized in earnings, respectively, with an $2 million amount excluded from hedge effectiveness testing.
[2]	All amounts are net of tax. Amounts in parentheses represent a decrease in net income.

Debt and Credit Agreements - Co

Debt and Credit Agreements - Commercial Paper Borrowings Outstanding (Details) - Commercial Paper [Member] - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Short-term Debt [Line Items]
Commercial paper borrowings	$ 0	$ 0
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	0	0
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	604	304
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	$ 50	$ 120

Debt and Credit Agreements - Li

Debt and Credit Agreements - Lines of Credit under Committed Credit Facilities (Details) $ in Millions	Sep. 30, 2015USD ($)
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 8,500	[1]
Line of Credit Facility, Current Borrowing Capacity	22
Parent [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	500	[1],[2]
Exelon Generation Co L L C [Member] | Community and Minority Banks [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	50
Letters of Credit Outstanding, Amount	7
Exelon Generation Co L L C [Member] | CitiBank [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	300	[1]
Exelon Generation Co L L C [Member] | CIBC [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	100	[1]
Exelon Generation Co L L C [Member] | SUMITOMO [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	100	[1]
Commonwealth Edison Co [Member] | Community and Minority Banks [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	34
Letters of Credit Outstanding, Amount	16
Commonwealth Edison Co [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	1,000	[1]
PECO Energy Co [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	27
PECO Energy Co [Member] | Community and Minority Banks [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	34
Letters of Credit Outstanding, Amount	21
PECO Energy Co [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	600	[1],[2]
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	27
Baltimore Gas and Electric Company [Member] | Community and Minority Banks [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	5
Letters of Credit Outstanding, Amount	1
Baltimore Gas and Electric Company [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	600	[1],[2]
Syndicated Revolver 1 [Member] | Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	5,100	[1]
Syndicated Revolver 2 [Member] | Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 200	[1]
[1]	Excludes additional credit facility agreements for Generation, ComEd, PECO and BGE with aggregate commitments of $50 million, $34 million, $34 million and $5 million, respectively, arranged with minority and community banks located primarily within ComEd’s, PECO’s and BGE’s service territories. These facilities expired on October 16, 2015 and were renewed at the same amount through October 14, 2016. These facilities are solely utilized to issue letters of credit. As of September 30, 2015, letters of credit issued under these agreements for Generation, ComEd, PECO and BGE totaled $7 million, $16 million, $21 million and $1 million, respectively.
[2]	Syndicated revolvers include credit facility commitments of $22 million, $27 million and $27 million for Exelon Corporate, PECO and BGE, respectively, which expire in August 2018.

Debt and Credit Agreements - Na

Debt and Credit Agreements - Narrative (Details) $ in Millions		Oct. 05, 2015USD ($)	Jun. 11, 2014USD ($)shares	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Oct. 23, 2015USD ($)	May. 01, 2014USD ($)
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 1,745	$ 1,214
equity units issued | shares			23,000,000
Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions			$ 35
Subordinated Borrowing, Interest Rate			2.50%
Long-term Debt			$ 131
Line of Credit Facility, Maximum Borrowing Capacity	[1]			$ 8,500
Parent Company [Member]
Debt Instrument [Line Items]
Basis points adders for prime-based borrowings				0.275%
Basis Points For Libor Based Borrowings				0.01275
Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 260	617
Basis points adders for prime-based borrowings				0.075%
Basis Points For Libor Based Borrowings				0.01075
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 64	552
Basis points adders for prime-based borrowings				0.275%
Basis Points For Libor Based Borrowings				0.01275
PECO Energy Co [Member]
Debt Instrument [Line Items]
Basis points adders for prime-based borrowings				0.00%
Basis Points For Libor Based Borrowings				0.009
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 37	35
Basis points adders for prime-based borrowings				0.00%
Basis Points For Libor Based Borrowings				0.01
Revolving Credit Facility [Member] | Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1]			$ 1,000
Revolving Credit Facility [Member] | PECO Energy Co [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1],[2]			600
Revolving Credit Facility [Member] | Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1],[2]			600
Parent [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1],[2]			$ 500
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage				1.00%
Unamortized Debt Issuance Expense				$ 22
Senior Notes [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt					$ 9
Interest Rate					4.40%
Debt Instrument, Face Amount	[3]			750
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount							$ 4,200
Convertible Debt Securities [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Subordinated Long-term Debt			1,110
Junior Subordinated Debt [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 33
ExGen425Feb062021 [Member] | Senior Notes [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 300
AGE143Nov172017 [Member] | Senior Notes [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Interest Rate				1.43%
Debt Instrument, Face Amount				$ 74
TaxExemptBonds255 [Member] | First Mortgage Bonds [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[4]			$ 435
TaxExemptBonds255 [Member] | Maximum [Member] | First Mortgage Bonds [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Interest Rate				2.70%
TaxExemptBonds255 [Member] | Minimum [Member] | First Mortgage Bonds [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Interest Rate				2.50%
AVSR [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 12
Debt Instrument, Face Amount				$ 39	$ 125
AVSR [Member] | Maximum [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Interest Rate				2.96%	3.14%
AVSR [Member] | Minimum [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Interest Rate				2.29%	3.06%
SeniorSecuredNotes525January152014Member [Member] | Senior Notes [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt					$ 500
Interest Rate					5.35%
SeniorSecuredNotes525January152014Member [Member] | Junior Subordinated Debt [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt			$ 1,150
Subsequent Event [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity						$ 100
Subsequent Event [Member] | First Mortgage Bonds [Member] | PECO Energy Co [Member]
Debt Instrument [Line Items]
Long-term Debt		$ 350
Interest Rate		3.15%
Subsequent Event [Member] | AVSR [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Secured Debt		$ 10
Bridge Loan [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity							3,200
Line of Credit Facility, Maximum Borrowing Capacity							$ 7,200
[1]	Excludes additional credit facility agreements for Generation, ComEd, PECO and BGE with aggregate commitments of $50 million, $34 million, $34 million and $5 million, respectively, arranged with minority and community banks located primarily within ComEd’s, PECO’s and BGE’s service territories. These facilities expired on October 16, 2015 and were renewed at the same amount through October 14, 2016. These facilities are solely utilized to issue letters of credit. As of September 30, 2015, letters of credit issued under these agreements for Generation, ComEd, PECO and BGE totaled $7 million, $16 million, $21 million and $1 million, respectively.
[2]	Syndicated revolvers include credit facility commitments of $22 million, $27 million and $27 million for Exelon Corporate, PECO and BGE, respectively, which expire in August 2018.
[3]	In connection with the issuance of Senior Unsecured Notes, Exelon terminated floating-to-fixed interest rate swaps that had been designated as cash flow hedges. See Note 10 — Derivative Financial Instruments for further information on the swap termination.
[4]	The Tax Exempt Pollution Control Revenue Bonds have a mandatory put date that ranges from March 1, 2019 - September 1, 2020.

Debt and Credit Agreements - Sc

Debt and Credit Agreements - Schedule of Issuance of Long-Term Debt (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2015	Oct. 15, 2015	Oct. 05, 2015	Sep. 30, 2014	Jun. 11, 2014	May. 01, 2014
Debt Instrument [Line Items]
Long-term Debt						$ 131
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage		1.00%
Unamortized Debt Issuance Expense		$ 22
Senior Notes [Member] | MergerDebt155June092017 [Member]
Debt Instrument [Line Items]
Interest Rate		1.55%
Debt Instrument, Face Amount	[1]	$ 550
Senior Notes [Member] | MergerDebt285June152020 [Member]
Debt Instrument [Line Items]
Interest Rate		2.85%
Debt Instrument, Face Amount	[1]	$ 900
Senior Notes [Member] | MergerDebt395June152025 [Member]
Debt Instrument [Line Items]
Interest Rate		3.95%
Debt Instrument, Face Amount	[1]	$ 1,250
Senior Notes [Member] | MergerDebt495June152035 [Member]
Debt Instrument [Line Items]
Interest Rate		4.95%
Debt Instrument, Face Amount	[1]	$ 500
Senior Notes [Member] | MergerDebt510June152045 [Member]
Debt Instrument [Line Items]
Interest Rate		5.10%
Debt Instrument, Face Amount	[1]	$ 1,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount							$ 4,200
Subordinated Debt [Member] | JuniorNotes250June012024 [Member]
Debt Instrument [Line Items]
Interest Rate					2.50%
Debt Instrument, Face Amount					$ 1,150
Notes Payable, Other Payables [Member] | SoftwareLicense395May012024 [Member]
Debt Instrument [Line Items]
Interest Rate		3.95%
Debt Instrument, Face Amount		$ 111
Exelon Generation Co L L C [Member] | AVSR [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 39			$ 125
Exelon Generation Co L L C [Member] | AVSR [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest Rate		2.96%			3.14%
Exelon Generation Co L L C [Member] | AVSR [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest Rate		2.29%			3.06%
Exelon Generation Co L L C [Member] | First Mortgage Bonds [Member] | TaxExemptBonds255 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[2]	$ 435
Exelon Generation Co L L C [Member] | First Mortgage Bonds [Member] | TaxExemptBonds255 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest Rate		2.70%
Exelon Generation Co L L C [Member] | First Mortgage Bonds [Member] | TaxExemptBonds255 [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest Rate		2.50%
Exelon Generation Co L L C [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest Rate					4.40%
Debt Instrument, Face Amount	[3]	$ 750
Exelon Generation Co L L C [Member] | Senior Notes [Member] | ExgenRenewables425February62021 [Member]
Debt Instrument [Line Items]
Interest Rate					5.25%
Exelon Generation Co L L C [Member] | Senior Notes [Member] | Energy Efficiency Project Financing [Member]
Debt Instrument [Line Items]
Interest Rate		3.71%
Debt Instrument, Face Amount		$ 42
Exelon Generation Co L L C [Member] | Senior Notes [Member] | EnergyEfficiency355Nov152016 [Member]
Debt Instrument [Line Items]
Interest Rate		3.55%
Debt Instrument, Face Amount		$ 19
Exelon Generation Co L L C [Member] | Senior Notes [Member] | SeniorNotesJuly12023Member [Member]
Debt Instrument [Line Items]
Interest Rate		2.95%
Debt Instrument, Face Amount	[3]	$ 750
Exelon Generation Co L L C [Member] | Senior Notes [Member] | ExGen425Feb062021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 300
Exelon Generation Co L L C [Member] | Senior Notes [Member] | AGE143Nov172017 [Member]
Debt Instrument [Line Items]
Interest Rate		1.43%
Debt Instrument, Face Amount		$ 74
Exelon Generation Co L L C [Member] | Unsecured Debt [Member] | ExGen Texas Power [Member]
Debt Instrument [Line Items]
Interest Rate					4.94%
Debt Instrument, Face Amount					$ 675
Exelon Generation Co L L C [Member] | Unsecured Debt [Member] | Energy Efficiency Project Financing [Member]
Debt Instrument [Line Items]
Interest Rate					4.12%
Debt Instrument, Face Amount					$ 12
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | ExgenRenewables425February62021 [Member]
Debt Instrument [Line Items]
Interest Rate		5.25%			4.44%
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | ExgenRenewables425February62021 [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Interest Rate			5.25%
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | ExGen Texas Power [Member]
Debt Instrument [Line Items]
Interest Rate		4.94%
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | Continental Wind 6000 February 28, 2033 [Member]
Debt Instrument [Line Items]
Interest Rate		6.00%			6.00%
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | NuclearFuelPurchaseContract3250june302018Member [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 70
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | NuclearFuelPurchaseContract3250june302018Member [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest Rate					3.35%
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | NuclearFuelPurchaseContract3250june302018Member [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest Rate					3.25%
Commonwealth Edison Co [Member] | First Mortgage Bonds [Member] | FirstMortgageBondSeries115January152019 [Member]
Debt Instrument [Line Items]
Interest Rate					2.15%
Debt Instrument, Face Amount					$ 300
Commonwealth Edison Co [Member] | First Mortgage Bonds [Member] | FirstMortgageBondSeries116January152044 [Member]
Debt Instrument [Line Items]
Interest Rate					4.70%
Debt Instrument, Face Amount					$ 350
Commonwealth Edison Co [Member] | First Mortgage Bonds [Member] | FirstMortgageBondSeries118March12045 [Member]
Debt Instrument [Line Items]
Interest Rate		3.70%
Debt Instrument, Face Amount		$ 400
PECO Energy Co [Member] | First Mortgage Bonds [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Long-term Debt				$ 350
Interest Rate				3.15%
PECO Energy Co [Member] | First Mortgage Bonds [Member] | FirstMortgageBond101 [Member]
Debt Instrument [Line Items]
Interest Rate					4.15%
Debt Instrument, Face Amount					$ 300
[1]	In connection with the issuance of PHI acquisition financing, Exelon terminated its interest rate swaps that had been designated as cash flow hedges. See Note 10 — Derivative Financial Instruments for further informatio
[2]	The Tax Exempt Pollution Control Revenue Bonds have a mandatory put date that ranges from March 1, 2019 - September 1, 2020.
[3]	In connection with the issuance of Senior Unsecured Notes, Exelon terminated floating-to-fixed interest rate swaps that had been designated as cash flow hedges. See Note 10 — Derivative Financial Instruments for further information on the swap termination.

Debt and Credit Agreements - Re

Debt and Credit Agreements - Retirement and Redemptions of Current and Long-Term Debt (Details) - USD ($) $ in Millions		Oct. 15, 2015	Oct. 05, 2015	Sep. 30, 2015	Sep. 30, 2014
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 1,745	$ 1,214
Senior Notes [Member] | SeniorSecuredNotes455Jun152015 [Member]
Debt Instrument [Line Items]
Interest Rate				4.55%
Repayments of Long-term Debt	[1]			$ 550
SeniorNotes490June152015 [Member] | SeniorNotes490June152015 [Member]
Debt Instrument [Line Items]
Interest Rate				4.90%
Repayments of Long-term Debt				$ 800
Notes Payable, Other Payables [Member] | SoftwareLicense395May012024 [Member]
Debt Instrument [Line Items]
Interest Rate				3.95%
Repayments of Long-term Debt				$ 1
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 64	$ 552
Exelon Generation Co L L C [Member] | AVSR DOE Member [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest Rate					2.33%
Exelon Generation Co L L C [Member] | AVSR DOE Member [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest Rate				3.56%	3.55%
Exelon Generation Co L L C [Member] | AVSR [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 12
Exelon Generation Co L L C [Member] | AVSR [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest Rate				2.29%	3.06%
Exelon Generation Co L L C [Member] | AVSR [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest Rate				2.96%	3.14%
Exelon Generation Co L L C [Member] | AVSR [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Repayments of Secured Debt			$ 10
Exelon Generation Co L L C [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest Rate					4.40%
Repayments of Long-term Debt					$ 9
Exelon Generation Co L L C [Member] | Senior Notes [Member] | SeniorSecuredNotes525January152014Member [Member]
Debt Instrument [Line Items]
Interest Rate					5.35%
Repayments of Long-term Debt					$ 500
Exelon Generation Co L L C [Member] | Senior Notes [Member] | ExgenRenewables425February62021 [Member]
Debt Instrument [Line Items]
Interest Rate					5.25%
Exelon Generation Co L L C [Member] | Senior Notes [Member] | SeniorSecuredNotes455Jun152015 [Member]
Debt Instrument [Line Items]
Interest Rate				4.55%
Repayments of Long-term Debt	[1]			$ 550
Exelon Generation Co L L C [Member] | Pollution Control Notes [Member] | Pollution Control Notes [Member]
Debt Instrument [Line Items]
Interest Rate					4.10%
Repayments of Long-term Debt					$ 20
Exelon Generation Co L L C [Member] | Capital Lease Obligations [Member] | Continental Wind 6000 February 28, 2033 [Member]
Debt Instrument [Line Items]
Interest Rate				7.83%	7.83%
Repayments of Long-term Debt				$ 3	$ 2
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | ExgenRenewables425February62021 [Member]
Debt Instrument [Line Items]
Interest Rate				5.25%	4.44%
Repayments of Long-term Debt				$ 14	$ 3
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | ExgenRenewables425February62021 [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Interest Rate		5.25%
Repayments of Long-term Debt		$ 10
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | Clear Horizon solar [Member]
Debt Instrument [Line Items]
Interest Rate				2.56%	2.56%
Repayments of Long-term Debt				$ 1	$ 1
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | Sacramento Solar [Member]
Debt Instrument [Line Items]
Interest Rate				2.58%	2.56%
Repayments of Long-term Debt				$ 1	$ 1
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | Continental Wind 6000 February 28, 2033 [Member]
Debt Instrument [Line Items]
Interest Rate				6.00%	6.00%
Repayments of Long-term Debt				$ 20	$ 20
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | ExGen Texas Power [Member]
Debt Instrument [Line Items]
Interest Rate				4.94%
Repayments of Long-term Debt				$ 5
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | UpstreamGasLending221July222016[Member]
Debt Instrument [Line Items]
Interest Rate				2.44%
Repayments of Long-term Debt				$ 9
Exelon Generation Co L L C [Member] | Unsecured Debt [Member] | ExGen Texas Power [Member]
Debt Instrument [Line Items]
Interest Rate					4.94%
Exelon Generation Co L L C [Member] | AVSR DOE Member [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt					$ 4
Baltimore Gas and Electric Company [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 37	$ 35
Baltimore Gas and Electric Company [Member] | Rate Stabilization Bonds, April 1, 2017 [Member] | Rate Stabilization Bonds, April 1, 2017 [Member]
Debt Instrument [Line Items]
Interest Rate					5.72%
Repayments of Long-term Debt					$ 35
Baltimore Gas and Electric Company [Member] | Rate Stabilization Bonds, April 1, 2017 [Member] | RateStabilization572April12016 [Member]
Debt Instrument [Line Items]
Interest Rate				5.72%
Repayments of Long-term Debt				$ 37
Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 260	$ 617
Commonwealth Edison Co [Member] | Pollution Control Notes [Member] | Pollution Control Notes [Member]
Debt Instrument [Line Items]
Interest Rate					5.85%
Repayments of Long-term Debt					$ 17
Commonwealth Edison Co [Member] | First Mortgage Bonds [Member] | FirstMortgageBond163January12014 [Member]
Debt Instrument [Line Items]
Interest Rate					1.63%
Repayments of Long-term Debt					$ 600
Commonwealth Edison Co [Member] | First Mortgage Bonds [Member] | FMBSeries470April152015 [Member]
Debt Instrument [Line Items]
Interest Rate				4.70%
Repayments of Long-term Debt				$ 260
[1]	(a)As part of the 2012 Constellation merger, Exelon and subsidiaries of Generation assumed intercompany loan agreements that mirrored the terms and amounts of external obligations held by Exelon, resulting in intercompany notes payable at Generation and Exelon Corporate

Income Taxes - Reconciliation t

Income Taxes - Reconciliation to Effective Tax Rate (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Increase (Decrease) due to
State income taxes, net of Federal income tax benefit	(2.70%)	(3.40%)	(3.10%)	(2.00%)
Qualified nuclear decommissioning trust fund income	(5.40%)	(0.30%)	(0.90%)	2.00%
Domestic production activities deduction	(4.90%)	(2.40%)	(2.80%)	(2.70%)
Health care reform legislation	(0.00%)	(0.00%)	(0.00%)	(0.10%)
Amortization of investment tax credit, net deferred taxes	(2.30%)	(1.00%)	(1.20%)	(1.10%)
Plant basis differences	(1.40%)	(0.80%)	(1.20%)	(1.60%)
Production tax credits and other credits	(3.80%)	(1.90%)	(2.20%)	(2.10%)
Statute of limitations expiration	(6.40%)	(3.80%)	(1.60%)	(2.50%)
Noncontrolling interest	1.70%	(1.20%)	(0.00%)	(1.40%)
Other	1.20%	1.20%	0.90%	(0.50%)
Effective Income Tax Rate Reconciliation, Percent	16.40%	28.20%	29.10%	27.20%
Exelon Generation Co L L C [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Increase (Decrease) due to
State income taxes, net of Federal income tax benefit	(2.10%)	(3.70%)	(2.80%)	(1.20%)
Qualified nuclear decommissioning trust fund income	(12.50%)	(0.40%)	(1.60%)	3.60%
Domestic production activities deduction	(11.60%)	(3.20%)	(4.90%)	(4.80%)
Health care reform legislation	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Amortization of investment tax credit, net deferred taxes	(5.20%)	(1.20%)	(1.90%)	(1.70%)
Plant basis differences	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Production tax credits and other credits	(9.00%)	(2.40%)	(3.80%)	(3.70%)
Statute of limitations expiration	(15.20%)	(5.00%)	(2.90%)	(4.40%)
Noncontrolling interest	3.90%	(1.60%)	0.10%	(2.60%)
Other	0.40%	0.60%	0.60%	(0.70%)
Effective Income Tax Rate Reconciliation, Percent	(12.10%)	25.50%	23.40%	21.90%
Commonwealth Edison Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Increase (Decrease) due to
State income taxes, net of Federal income tax benefit	(5.00%)	(5.00%)	(5.20%)	(5.00%)
Qualified nuclear decommissioning trust fund income	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Domestic production activities deduction	(0.00%)		(0.00%)
Health care reform legislation	(0.00%)	(0.20%)	(0.00%)	(0.20%)
Amortization of investment tax credit, net deferred taxes	(0.30%)	(0.30%)	(0.30%)	(0.30%)
Plant basis differences	(0.10%)	(0.00%)	(0.10%)	(0.30%)
Production tax credits and other credits	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Noncontrolling interest	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Other	0.30%	0.10%	0.20%	0.10%
Effective Income Tax Rate Reconciliation, Percent	39.90%	40.00%	40.00%	39.70%
PECO Energy Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Increase (Decrease) due to
State income taxes, net of Federal income tax benefit	(1.20%)	(0.10%)	(1.20%)	(0.30%)
Qualified nuclear decommissioning trust fund income	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Domestic production activities deduction	(0.00%)		(0.00%)
Health care reform legislation	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Amortization of investment tax credit, net deferred taxes	(0.10%)	(0.10%)	(0.10%)	(0.10%)
Plant basis differences	(7.00%)	(11.30%)	(7.30%)	(11.00%)
Production tax credits and other credits	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Noncontrolling interest	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Other	0.00%	(0.10%)	0.20%	0.10%
Effective Income Tax Rate Reconciliation, Percent	29.10%	23.60%	29.00%	24.30%
Baltimore Gas and Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	35.00%	35.00%	35.00%	35.00%
Increase (Decrease) due to
State income taxes, net of Federal income tax benefit	(5.30%)	(4.60%)	(5.30%)	(4.90%)
Qualified nuclear decommissioning trust fund income	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Domestic production activities deduction	(0.00%)		(0.00%)
Health care reform legislation	(0.20%)	(0.20%)	(0.20%)	(0.20%)
Amortization of investment tax credit, net deferred taxes	(0.20%)	(0.30%)	(0.10%)	(0.30%)
Plant basis differences	(0.60%)	0.50%	(0.40%)	0.50%
Production tax credits and other credits	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Noncontrolling interest	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Other	(0.40%)	(1.20%)	(0.10%)	(0.50%)
Effective Income Tax Rate Reconciliation, Percent	39.30%	38.80%	39.90%	39.80%

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended				9 Months Ended
	Sep. 30, 2014	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Jun. 30, 2013	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Mar. 31, 2013	Dec. 31, 2009
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits		$ 1,204				$ 1,204		$ 1,829
Unrecognized Tax Benefits, Increase Resulting from Settlements with Taxing Authorities						261
Deferred tax gain under involuntary conversion provisions of the IRC										$ 1,200
IRS asserted penalties for understatement of tax						90
Expected non-cash charge to earnings									$ 265
Potential tax and interest from a successful IRS challenge of the like-kind exchange transaction position		560				560
Early termination amount				$ 335
Unrecognized Tax Benefits, Interest on Income Taxes Accrued									265
Income taxes		115		422		805	$ 646
Increase in Unrecognized Tax Benefits is Reasonably Possible		71				71
Settlement with Taxing Authority [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits		394				394
Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits		660				660		1,357
Unrecognized tax benefits that if recognized would affect the effective tax rate		141				141
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions			$ 661
Increase (Decrease) in Income Taxes	$ 141
Effective Income Tax Rate Reconciliation, Tax Settlement, Amount		120
Income taxes		(36)		291		371	290
Commonwealth Edison Co [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits		144				144		149
Expected non-cash charge to earnings									170
Non-cash equity contributions					$ 172
Potential tax and interest from a successful IRS challenge of the like-kind exchange transaction position		165				165
Unrecognized Tax Benefits, Interest on Income Taxes Accrued									$ 170
Income taxes		99		84		226	221
Increase in Unrecognized Tax Benefits is Reasonably Possible		11				11
Commonwealth Edison Co [Member] | Settlement with Taxing Authority [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits		144				144
PECO Energy Co [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits		0				0		44
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions			$ 43
Income taxes		37		25		122	82
Baltimore Gas and Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits		120				120		$ 0
Income taxes		$ 35		$ 31		$ 141	$ 103

Nuclear Decommissioning - Rollf

Nuclear Decommissioning - Rollforward of Nuclear Decommissioning ARO (Details) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
		Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Accretion Expense	[1]		$ 291	$ 251
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate		$ 8		16
Asset Retirement Obligation, Accretion Expense	[1]		291	$ 251
Nuclear Plant [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Nuclear Decommissioning ARO, Ending Balance		1,729	1,729
Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Nuclear Decommissioning ARO, Beginning Balance	[2]		6,961
Costs incurred to decommission retired plants			(2)
Nuclear Decommissioning ARO, Ending Balance	[2]	8,073	8,073
Asset Retirement Obligation, Revision of Estimate			831
Asset Retirement Obligation, Accretion Expense			283
Current portion of ARO		$ 7	$ 7		$ 8
[1]	Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
[2]	Includes $7 million and $8 million as the current portion of the ARO at September 30, 2015 and December 31, 2014 respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets.

Nuclear Decommissioning (Detail

Nuclear Decommissioning (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	$ 10,103		$ 10,103		$ 10,537
Decommissioning Liability, Noncurrent	99		99		155
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)				$ 1,800
AssetRetirementObligationPeriodIncreaseSiteSecurity	550
AssetRetirementObligationPeriodIncreaseSNF	285
Decommissioning Fund Investments	10,103		10,103		10,537
Decommissioning Liability, Noncurrent	99		99		$ 155
Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)	775	$ 55	1,100
Decommissioning Liability, Noncurrent	$ 82		$ 82

Nuclear Decommissioning - Unrea

Nuclear Decommissioning - Unrealized Gains on NDT Funds (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Unrealized Losses On Nuclear Decommissioning Trust Fund Investment [Line Items]
Net unrealized gains (losses) on decommissioning trust funds - regulatory agreement units	[1]	$ (301)	$ (107)	$ (385)	$ 126
Net unrealized gains (losses) on decommissioning trust funds - non-regulatory agreement units	[2],[3]	$ (218)	(41)	(274)	100
Unrealized Gain Loss Investment Income Pledged Assets			$ 7	$ 9	$ 27
[1]	Net unrealized gains (losses) related to Generation’s NDT funds associated with Regulatory Agreement Units are included in Regulatory liabilities on Exelon’s Consolidated Balance Sheets and Noncurrent payables to affiliates on Generation’s Consolidated Balance Sheets.
[2]	Excludes $7 million of net unrealized gains related to the Zion Station pledged assets for the three months ended September 30, 2014 and $9 million and $27 million of net unrealized gains related to the Zion Station pledged assets for the nine months ended September 30, 2015 and 2014, respectively. Net unrealized gains related to Zion Station pledged assets are included in the Payable for Zion Station decommissioning on Exelon’s and Generation’s Consolidated Balance Sheets.
[3]	Net unrealized gains (losses) related to Generation’s NDT funds with Non-Regulatory Agreement Units are included within Other, net in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income.

Nuclear Decommissioning - Asset

Nuclear Decommissioning - Assets, Payables and Withdrawals by ZionSolutions (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Nuclear Decommissioning Additional Narrative Information [Line Items]
Pledged assets for Zion Station decommissioning		$ 237		$ 319
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Pledged assets for Zion Station decommissioning		237		319
Payable to Zion Solutions	[1]	217		292
Current portion of payable to Zion Solutions	[2]	118		$ 137
Withdrawals by Zion Solutions to pay decommissioning costs		$ 757	$ 666
[1]	Excludes a liability recorded within Exelon’s and Generation’s Consolidated Balance Sheets related to the tax obligation on the unrealized activity associated with the Zion Station NDT Funds. The NDT Funds will be utilized to satisfy the tax obligations as gains and losses are realized.
[2]	Included in Other current liabilities within Exelon’s and Generation’s Consolidated Balance Sheets.

Retirement Benefits - Narrative

Retirement Benefits - Narrative (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Changes in plan assets and benefit obligations recognized in OCI			$ 27
Increase in regulatory assets due valuation received by Exelon for its legacy pension and other postretirement benefit obligations.			48
Increase in regulatory liabilities due to updated valuation of Exelon's legacy pension and postretirement benefit obligations			11
CENG [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		$ 5		$ 5	$ 16	$ 11
Business Services Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense	[1]	14		11	43	37
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense	[2]	67		54	200	193
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		52		33	155	129
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		10		7	29	28
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		16		17	$ 49	50
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation increase (decrease) reflecting actual census data			45
Expected return on assets					7.00%
Discount rate					3.94%
Pension Plan, Defined Benefit [Member] | CENG [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		2		2	$ 8	5
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation increase (decrease) reflecting actual census data			$ 57
Expected return on assets					6.46%
Discount rate					3.92%
Other Postretirement Benefit Plan, Defined Benefit [Member] | CENG [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		$ 3		$ 3	$ 8	$ 6
[1]	These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO or BGE amounts above.
[2]	For the three and nine months ended September 30, 2015, the costs related to CENG were $5 million and $16 million, respectively. For the three months ended September 30, 2014, the costs related to CENG were $5 million. For the period of April 1, 2014 to September 30, 2014, the costs related to CENG were $11 million. CENG amounts are included in the table above.

Retirement Benefits - Calculati

Retirement Benefits - Calculation of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1]	$ 51	$ 34	$ 111		$ 82
Amortization of:
Pension and Other Postretirement Benefit Expense				476		437
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		82	74	245	[2]	218	[2]
Interest cost		178	189	533	[2]	561	[2]
Expected return on assets		(257)	(251)	(770)	[2]	(743)	[2]
Amortization of:
Prior service cost (benefit)		3	3	10	[2]	10	[2]
Actuarial loss		142	106	427	[2]	316	[2]
Net periodic benefit cost		148	121	445	[2]	362	[2]
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		30	27	89	[2]	90	[2]
Interest cost		42	42	125	[2]	144	[2]
Expected return on assets		(38)	(39)	(113)	[2]	(115)	[2]
Amortization of:
Prior service cost (benefit)		(43)	(44)	(130)	[2]	(79)	[2]
Actuarial loss		20	15	60	[2]	35	[2]
Net periodic benefit cost		11	1	31	[2]	75	[2]
CENG [Member]
Amortization of:
Pension and Other Postretirement Benefit Costs		5	5	16		11
CENG [Member] | Pension Plan, Defined Benefit [Member]
Amortization of:
Pension and Other Postretirement Benefit Costs		2	2	8		5
CENG [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Amortization of:
Pension and Other Postretirement Benefit Costs		$ 3	$ 3	$ 8		$ 6
[1]	Includes $4 million and $8 million, respectively, related to CENG for the three and nine months ended September 30, 2015. Includes $1 million related to CENG for the three months ended September 30, 2014 and for the period from April 1, 2014 to September 30, 2014.
[2]	For the three months ended September 30, 2015, the cost for pension benefits and other postretirement benefits related to CENG were $2 million and $3 million, respectively. For the three months ended September 30, 2014, the cost for pension benefits and other postretirement benefits related to CENG were $2 million and $3 million, respectively. CENG amounts are included in the tables above. (b)For the nine months ended September 30, 2015, the cost for pension benefits and other postretirement benefits related to CENG were $8 million and $8 million, respectively. For the period of April 1, 2014 to September 30, 2014, the cost for pension benefits and other postretirement benefits related to CENG were $5 million and $6 million, respectively. CENG amounts are included in the tables above.

Retirement Benefits - Allocated

Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense	[1]	$ 67	$ 54	$ 200	$ 193
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		52	33	155	129
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		10	7	29	28
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		16	17	49	50
Business Services Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense	[2]	14	11	43	37
CENG [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		5	5	16	11
CENG [Member] | Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		$ 2	$ 2	$ 8	$ 5
[1]	For the three and nine months ended September 30, 2015, the costs related to CENG were $5 million and $16 million, respectively. For the three months ended September 30, 2014, the costs related to CENG were $5 million. For the period of April 1, 2014 to September 30, 2014, the costs related to CENG were $11 million. CENG amounts are included in the table above.
[2]	These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These amounts are not included in the Generation, ComEd, PECO or BGE amounts above.

Retirement Benefits - Defined C

Retirement Benefits - Defined Contribution Savings Plans (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1]	$ 51	$ 34	$ 111	$ 82
CENG [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1]	4	1	8
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1]	27	17	60	41
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		10	8	23	20
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		3	2	7	6
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		5	3	10	7
Business Services Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[2]	$ 6	$ 4	$ 11	$ 8
[1]	Includes $4 million and $8 million, respectively, related to CENG for the three and nine months ended September 30, 2015. Includes $1 million related to CENG for the three months ended September 30, 2014 and for the period from April 1, 2014 to September 30, 2014.
[2]	These amounts primarily represent amounts billed to Exelon’s subsidiaries through intercompany allocations. These costs are not included in the Generation, ComEd, PECO or BGE amounts above.

Severance - Ongoing Severance P

Severance - Ongoing Severance Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	$ (3)	$ (2)	$ 18	$ 4
Exelon Generation Co L L C [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	(3)	(2)	17	3
Commonwealth Edison Co [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	0	0	1	1
PECO Energy Co [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	0	0	0	0
Baltimore Gas and Electric Company [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	$ 0	$ 0	$ 0	$ 0

Changes in Accumulated Other 91

Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			$ (2,684)		$ (2,040)
OCI before reclassifications	[1]			(64)		229
Amounts reclassified from AOCI	[1],[2]			152		(106)
Net current-period OCI		$ 32	$ (11)	88	[1]	123	[1]
Ending balance	[1]	(2,596)	(1,917)	(2,596)		(1,917)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			(28)		120
OCI before reclassifications	[1]			(18)		(14)
Amounts reclassified from AOCI	[1],[2]			22		(78)
Net current-period OCI	[1]			4		(92)
Ending balance	[1]	(24)	28	(24)		28
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance				3	[1]	2
OCI before reclassifications	[1]			0		(2)
Net current-period OCI	[1]			0		(2)
Ending balance	[1]	3	0	3		0
Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			(2,640)		(2,260)
OCI before reclassifications	[1]			(29)		240
Amounts reclassified from AOCI	[1],[2]			130		91
Net current-period OCI	[1]			101		331
Ending balance	[1]	(2,539)	(1,929)	(2,539)		(1,929)
Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance				(19)	[1]	(10)
OCI before reclassifications	[1]			(17)		(6)
Net current-period OCI	[1]			(17)		(6)
Ending balance	[1]	(36)	(16)	(36)		(16)
Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			0		108
OCI before reclassifications	[1]			0		11
Amounts reclassified from AOCI	[1],[2]			0		(119)
Net current-period OCI	[1]			0		(108)
Ending balance	[1]	0	0	0		0
Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			(36)		214
OCI before reclassifications	[1]			(30)		(6)
Amounts reclassified from AOCI	[1],[2]			6		(197)
Net current-period OCI		(13)	(26)	(24)	[1]	(203)	[1]
Ending balance	[1]	(60)	11	(60)		11
Exelon Generation Co L L C [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			(18)		114
OCI before reclassifications	[1]			(13)		(8)
Amounts reclassified from AOCI	[1],[2]			6		(78)
Net current-period OCI	[1]			(7)		(86)
Ending balance	[1]	(25)	28	(25)		28
Exelon Generation Co L L C [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			1		2
OCI before reclassifications	[1]			0		(3)
Net current-period OCI	[1]			0		(3)
Ending balance	[1]	1	(1)	1		(1)
Exelon Generation Co L L C [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]					0
Ending balance	[1]		0			0
Exelon Generation Co L L C [Member] | Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance				(19)	[1]	(10)
OCI before reclassifications	[1]			(17)		(6)
Net current-period OCI	[1]			(17)		(6)
Ending balance	[1]	(36)	(16)	(36)		(16)
Exelon Generation Co L L C [Member] | Accumulated Equity Investment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			0		108
OCI before reclassifications	[1]			0		11
Amounts reclassified from AOCI	[1],[2]			0		(119)
Net current-period OCI	[1]			0		(108)
Ending balance	[1]	0	0	0		0
PECO Energy Co [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			1		1
Ending balance	[1]	1	1	1		1
PECO Energy Co [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			0		0
Ending balance	[1]	0	0	0		0
PECO Energy Co [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			1		1
Ending balance	[1]	$ 1	$ 1	$ 1		$ 1
[1]	All amounts are net of tax. Amounts in parentheses represent a decrease in accumulated other comprehensive income.
[2]	See tables following changes in accumulated other comprehensive income tables for details about these reclassifications.

Changes in Accumulated Other 92

Changes in Accumulated Other Comprehensive Income - Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues		$ 7,401	[1]	$ 6,912	[1]	$ 22,746	[2]	$ 20,173	[2]
Income before income taxes		703		1,496		2,767		2,371
Income taxes		(115)		(422)		(805)		(646)
Net income		587		1,074		1,959		1,725
Prior service benefit reclassified to periodic benefit cost		8		8		22		11
Other Nonoperating Income (Expense)		(244)		16		(179)		346
Equity in losses of unconsolidated affiliates				0		(3)		(20)
Interest Expense		243		247		724		691
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	[3]	(46)		(7)		(152)		106
Reclassification out of Accumulated Other Comprehensive Income [Member] | Energy Related Derivative [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues						2
Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Swap [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues						26
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	[3]	(4)		28		(35)		130
Income taxes	[3]	1		(12)		13		(52)
Net income	[3]	(3)		16		(22)		78
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Energy Related Derivative [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues				28				130
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues		4
Other Nonoperating Income (Expense)						(11)
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	[3]	(71)		(42)		(213)		(149)
Income taxes		28	[3]	16		83	[3]	58
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	[3]	(43)				(130)
Net income	[3]			(26)				(91)
Prior service benefit reclassified to periodic benefit cost		19	[3],[4]	19		57	[3],[4]	29
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax		(90)	[3],[4]	(61)		(270)	[3],[4]	(178)
Equity Method Investments | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	[3]			5				198
Income taxes				(2)				(79)
Net income	[3]			3				119
Other Nonoperating Income (Expense)				5				5
Gain on consolidation of CENG								193
Exelon Generation Co L L C [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues		4,768		4,412		14,841		12,591
Income before income taxes		297		1,140		1,583		1,327
Income taxes		36		(291)		(371)		(290)
Net income		332		849		1,208		1,037
Other Nonoperating Income (Expense)		(257)		4		(193)		306
Equity in losses of unconsolidated affiliates				1		(4)		(20)
Interest Expense		56		77		236		224
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	[3]	(3)		19		(6)		197
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Energy Related Derivative [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues						2
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Swap [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues						0
Exelon Generation Co L L C [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	[3]	(4)		28		(9)		130
Income taxes	[3]	1		(12)		3		(52)
Net income	[3]	(3)		16		(6)		78
Exelon Generation Co L L C [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Energy Related Derivative [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues				28				130
Exelon Generation Co L L C [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues		4
Other Nonoperating Income (Expense)						11
Exelon Generation Co L L C [Member] | Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes		0	[3]	0		0	[3]	0
Income taxes		0	[3]	0		0	[3]	0
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	[3]	0				0
Net income				0				0
Prior service benefit reclassified to periodic benefit cost		0	[3],[4]	0		0	[3],[4]	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax		$ 0	[3],[4]	0		$ 0	[3],[4]	0
Exelon Generation Co L L C [Member] | Equity Method Investments | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	[3]			5				198
Income taxes				(2)				(79)
Net income	[3]			3				119
Other Nonoperating Income (Expense)				$ 5				5
Gain on consolidation of CENG								$ 193
[1]	(c)For the three months ended September 30, 2015 and 2014, utility taxes of $28 million and $22 million, respectively, are included in revenues and expenses for Generation. For the three months ended September 30, 2015 and 2014, utility taxes of $63 million and $61 million, respectively, are included in revenues and expenses for ComEd. For the three months ended September 30, 2015 and 2014, utility taxes of $37 million and $34 million, respectively, are included in revenues and expenses for PECO. For the three months ended September 30, 2015 and 2014, utility taxes of $23 million and $21 million, respectively, are included in revenues and expenses for BGE.
[2]	(d)Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.
[3]	All amounts are net of tax. Amounts in parentheses represent a decrease in net income.
[4]	This accumulated other comprehensive income component is included in the computation of net periodic pension and OPEB cost (see Note 14— Retirement Benefits for additional details).

Changes in Accumulated Other 93

Changes in Accumulated Other Comprehensive Income - Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	[1]	$ (2,596)	$ (1,917)	$ (2,596)	$ (1,917)	$ (2,684)	$ (2,040)
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost		8	8	22	11
Actuarial loss reclassified to periodic cost		(35)	(24)	(105)	(69)
Pension and non-pension postretirement benefit plans valuation adjustment		0	5	17	(153)
Change in unrealized (gain) loss on cash flow hedges		3	15	(3)	62
Change in unrealized income on equity investments		0	3	0	73
Change in marketable securities		0	1	0	(1)
Total		(24)	8	(69)	(77)
Exelon Generation Co L L C [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	[1]	(60)	11	(60)	11	$ (36)	$ 214
Pension and non-pension postretirement benefit plans:
Change in unrealized (gain) loss on cash flow hedges		3	13	4	57
Change in unrealized income on equity investments		0	3	0	73
Change in marketable securities		0	1	0	(1)
Total		$ 3	$ 17	$ 4	$ 129
[1]	All amounts are net of tax. Amounts in parentheses represent a decrease in accumulated other comprehensive income.

Common Stock - Narrative (Detai

Common Stock - Narrative (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Jun. 11, 2014	Jun. 30, 2014	Sep. 30, 2015	Sep. 30, 2015	Jun. 05, 2013
Common Stock [Abstract]
Temporary Equity, Share Subscriptions			57.5	57.5
Shares Issued, Price Per Share					$ 35
Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions	$ 35
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share		$ 32.48
Junior Subordinated Notes, Noncurrent					$ 1,150
Forward Contract Indexed to Issuer's Equity, Indexed Shares					23
Proceeds from Issuance of Common Stock			$ 1,870	$ 1,868

Earnings Per Share and Equity -

Earnings Per Share and Equity - Schedule of Earnings per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 629	$ 993	$ 1,959	$ 1,604
Average common shares outstanding — basic	913	861	879	860
Potentially dilutive effect of stock options, performance share awards and restricted stock	2	2	4	3
Average common shares outstanding — diluted	915	863	883	863

Earnings Per Share and Equity96

Earnings Per Share and Equity - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Treasury Stock, Shares held	35,000,000		35,000,000		35,000,000
Treasury Stock, Value	$ 2,327		$ 2,327		$ 2,327
Stock options not included in the calculation of diluted common shares outstanding	4,000,000	2,000,000	2,000,000	1,000,000
Equity Forward Units [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Stock options not included in the calculation of diluted common shares outstanding		2,000,000		1,000,000
Employee Stock Option [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Stock options not included in the calculation of diluted common shares outstanding			14,000,000	16,000,000

Commitments and Contingencies -

Commitments and Contingencies - Commitments Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Mar. 31, 2014	Jun. 30, 2012
Guarantor Obligations [Line Items]
Accrued environmental liabilities	$ 376,000,000	$ 376,000,000		$ 347,000,000
Noncash Merger Related Costs			$ 44,000,000
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Accrued environmental liabilities	63,000,000	63,000,000		63,000,000
Minimum future operating lease payments due in one year	0	0
Minimum future operating lease payments due in three years	12,000,000	12,000,000
Minimum future operating lease payments due in four years	13,000,000	13,000,000
Minimum future operating lease payments due in five years	13,000,000	13,000,000
Minimum future operating lease payments due beyond five years	285,000,000	285,000,000
Noncash Merger Related Costs			44,000,000
Other Commitment	3,500,000	3,500,000
Loss Contingency, Loss in Period	44,000,000
Loss Contingency, Estimate of Possible Loss			105,000,000
Operating Leases, Future Minimum Payments, Due in Two Years	5,000,000	5,000,000
Costs Incurred, Development Costs		353,000,000
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Accrued environmental liabilities	3,000,000	3,000,000		$ 1,000,000
Business Acquisition, Direct Investment With State And Local Governments Due To Settlement						$ 1,000,000,000
Noncash Merger Related Costs			$ 0
Loss Contingency, Estimate of Possible Loss	1,700,000	1,700,000
Minimum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Business Acquisition, Construction Cost					$ 95,000,000
Business Acquisition, Development Of New Generation Cost	575,000,000	575,000,000
Maximum [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Business Acquisition, Construction Cost					$ 120,000,000
Business Acquisition, Development Of New Generation Cost	650,000,000	650,000,000
Equity Method Investments [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
2,016	276,000,000	276,000,000
2,015	38,000,000	38,000,000
2,018	$ 7,000,000	$ 7,000,000

Commitments and Contingencies98

Commitments and Contingencies - Schedule of Equity Investment Commitments (Details) - Equity Method Investments [Member] - Exelon Generation Co L L C [Member] $ in Millions	9 Months Ended
	Sep. 30, 2015USD ($)
Guarantor Obligations [Line Items]
2,015	$ 38
2,016	276
2,017	23
2,018	7
2,019	2
Total	346
Long-term Purchase Commitment, Amount	$ 20

Commitments and Contingencies99

Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Sep. 30, 2015USD ($)
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 9,958
Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	1,078	[1]
Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	5,823	[2]
Estimated net exposure for commercial transaction obligations	650
Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	3,057	[3]
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	7,227
Exelon Generation Co L L C [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	1,011	[1]
Exelon Generation Co L L C [Member] | Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	3,159	[4]
Estimated net exposure for commercial transaction obligations	475
Exelon Generation Co L L C [Member] | Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	3,057	[3]
Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	223
Commonwealth Edison Co [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	18	[1]
Commonwealth Edison Co [Member] | Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	205	[5]
Commonwealth Edison Co [Member] | Trust Preferred Securities [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	200
PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	210
PECO Energy Co [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	22	[1]
PECO Energy Co [Member] | Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	188	[6]
PECO Energy Co [Member] | Trust Preferred Securities [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	178
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	264
Baltimore Gas and Electric Company [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	1	[1]
Baltimore Gas and Electric Company [Member] | Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	263	[7]
Baltimore Gas and Electric Company [Member] | Trust Preferred Securities [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 250
Commonwealth Edison III [Member] | Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Percentage owned finance subsidiary	100.00%
PECO Trust III and IV [Member] | PECO Energy Co [Member]
Guarantor Obligations [Line Items]
Percentage owned finance subsidiary	100.00%
Baltimore Gas and Electric Capital Trust II [Member] | Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Percentage owned finance subsidiary	100.00%
[1]	Non-debt letters of credit maintained to provide credit support for certain transactions as requested by third parties.
[2]	Primarily reflects parental guarantees issued on behalf of Generation to allow the flexibility needed to conduct business with counterparties without having to post other forms of collateral. Also reflects guarantees issued to ensure performance under specific contracts, preferred securities of financing trusts, property leases, indemnifications, NRC minimum funding assurance requirements and miscellaneous guarantees. The estimated net exposure for obligations under commercial transactions covered by these guarantees was $650 million at September 30, 2015, which represents the total amount Exelon could be required to fund based on September 30, 2015 market prices.
[3]	Represents the maximum amount that Generation would be required to pay for retrospective premiums in the event of nuclear disaster at any domestic site, including CENG sites, under the Secondary Financial Protection pool as required under the Price-Anderson Act as well as the current aggregate annual retrospective premium obligation that could be imposed by NEIL. See the Nuclear Insurance section within this note for additional details on Generation’s nuclear insurance premiums.
[4]	Primarily reflects guarantees issued to ensure performance under energy marketing and other specific contracts. The estimated net exposure for obligations under commercial transactions covered by these guarantees was $475 million at September 30, 2015, which represents the total amount Generation could be required to fund based on September 30, 2015 market prices.
[5]	Primarily reflects full and unconditional guarantees of $200 million Trust Preferred Securities of ComEd Financing III, which is a 100% owned finance subsidiary of ComEd.
[6]	Primarily reflects full and unconditional guarantees of $178 million Trust Preferred Securities of PECO Trust III and IV, which are 100% owned finance subsidiaries of PECO.
[7]	Primarily reflects full and unconditional guarantees of $250 million Trust Preferred Securities of BGE Capital Trust II, which is a 100% owned finance subsidiary of BGE.

Commitments and Contingencie100

Commitments and Contingencies - Contingencies Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015USD ($)reactor
Commitments And Contingencies Additional Narrative Information [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 9,958
Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Total of U.S. licensed nuclear reactors | reactor	102
Nuclear financial protection pool value	$ 375
Maximum liability per nuclear incident	13,400
Guarantor Obligations, Maximum Exposure, Undiscounted	7,227
Funds available for claim	12,900
Recovery of Direct Costs	3,200
Nuclear Insurance Premiums [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Maximum assessment mandated by Price-Anderson Act per nuclear reactor for a nuclear incident	2,700
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 3,057	[1]
Nuclear Insurance Premiums [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Nuclear Insurance Financial Protection Pool Surcharge On Nuclear Incident Assessment	5.00%
Maximum assessment mandated by Price-Anderson Act per nuclear reactor for a nuclear incident	$ 127.3
Maximum liability per nuclear incident	19
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 3,057	[1]
[1]	Represents the maximum amount that Generation would be required to pay for retrospective premiums in the event of nuclear disaster at any domestic site, including CENG sites, under the Secondary Financial Protection pool as required under the Price-Anderson Act as well as the current aggregate annual retrospective premium obligation that could be imposed by NEIL. See the Nuclear Insurance section within this note for additional details on Generation’s nuclear insurance premiums.

Commitments and Contingencie101

Commitments and Contingencies - Environmental Issues Narrative (Details) $ in Millions	1 Months Ended		3 Months Ended	9 Months Ended
	Jan. 31, 2015USD ($)	Oct. 31, 2007USD ($)	Sep. 30, 2015USD ($)MGPSite	Sep. 30, 2015USD ($)MGPSitePrinciple_responsible_party	Dec. 31, 2014USD ($)	Sep. 30, 2014USD ($)
Accrual For Environmental Loss Contingencies [Line Items]
Net investment in long-term direct financing leases			$ 348	$ 348	$ 361
Litigation Settlement, Amount	$ 14
Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total number of MGP sites | MGPSite			42	42
Approved clean-up | MGPSite			17	17
Sites under study/remediation | MGPSite			25	25
Other Increase (Decrease) in Environmental Liabilities			$ 50
PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total number of MGP sites | MGPSite			26	26
Approved clean-up | MGPSite			16	16
Sites under study/remediation | MGPSite			10	10
Other Increase (Decrease) in Environmental Liabilities			$ 1
Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total number of MGP sites | MGPSite			13	13
Sites under study/remediation | MGPSite			2	2
Loss Contingency, Estimate of Possible Loss			$ 1.7	$ 1.7
Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Consent decree penalty		$ 1
Environmental loss contingencies			12	12	$ 13
Loss Contingency, Estimate of Possible Loss						$ 105
Cotter Corporation [Member] | Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total cost of remediation to be shared by PRPs				60
DOJ potential settlement				$ 90
Sixty-Eighth Street Dump [Member] | Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency Number Of Parties Jointly And Severally Liable In Environmental Protection Agency Action | Principle_responsible_party				19
Minimum estimated clean-up costs for all potentially responsible parties			50	$ 50
Maximum estimated clean-up costs for all potentially responsible parties			64	64
Rossville ash site [Member] | Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, Estimate of Possible Loss			$ 9	$ 9

Commitments and Contingencie102

Commitments and Contingencies - Litigation and Regulatory Matters (Details)	Nov. 19, 2013USD ($)	Jul. 11, 2011Customer	Jan. 31, 2015USD ($)	Sep. 30, 2015USD ($)Open_claimclaimant	Sep. 30, 2015USD ($)Open_claimCustomerclaimant	Dec. 31, 2014USD ($)	Sep. 30, 2014USD ($)	Jun. 05, 2013Customer
Telephone Consumer Protection Act Lawsuit [Abstract]
Litigation Settlement, Amount			$ 14,000,000
Exelon Generation Co L L C [Member]
Loss Contingency, Estimate [Abstract]
Loss Contingency, Estimate of Possible Loss							$ 105,000,000
Loss Contingency, Pending Claims, Number | Open_claim				217	217
Exelon Generation Co L L C [Member] | Asbestos Issue [Member]
Loss Contingency, Estimate [Abstract]
Loss Contingency, Estimate of Possible Loss				$ 95,000,000	$ 95,000,000
Estimated Litigation Liability, Noncurrent				75,000,000	75,000,000
Exelon Generation Co L L C [Member] | Pending Litigation [Member] | Asbestos Issue [Member]
Loss Contingency, Estimate [Abstract]
Loss Contingency, Estimate of Possible Loss				20,000,000	$ 20,000,000	$ 100,000,000
Commonwealth Edison Co [Member]
Continuous Power Interruption [Abstract]
Minimum number of customers ComEd can be held liable to for power interruption | Customer					30,000
Number of customers affected by a major storm | Customer		900,000
Number of customers proposed by the ICC that ComEd should not be granted a waiver under Continuous Power Interruption | Customer								34,559
Commonwealth Edison Co [Member] | Settled Litigation [Member] | Telephone Consumer Protection Act Lawsuit [Member]
Telephone Consumer Protection Act Lawsuit [Abstract]
Litigation Settlement, Amount				$ 5,000,000
Loss Contingency, Estimate [Abstract]
Loss Contingency, Number of Plaintiffs | claimant				1,200,000
Commonwealth Edison Co [Member] | Maximum [Member] | Pending Litigation [Member] | Telephone Consumer Protection Act Lawsuit [Member]
Telephone Consumer Protection Act Lawsuit [Abstract]
Loss Contingency, Damages Sought, Value	$ 1,500
Commonwealth Edison Co [Member] | Minimum [Member] | Pending Litigation [Member] | Telephone Consumer Protection Act Lawsuit [Member]
Telephone Consumer Protection Act Lawsuit [Abstract]
Loss Contingency, Damages Sought, Value	$ 500
Baltimore Gas and Electric Company [Member]
Loss Contingency, Estimate [Abstract]
Loss Contingency, Estimate of Possible Loss				$ 1,700,000	$ 1,700,000
Baltimore Gas and Electric Company [Member] | Pending Litigation [Member] | Asbestos Issue [Member]
Loss Contingency, Estimate [Abstract]
Loss Contingency, Number of Plaintiffs | claimant					468

Commitments and Contingencie103

Commitments and Contingencies - Schedule of Accruals for Environmental Matters (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	$ 376	$ 347
Accrual For MGP Investigation And Remediation [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	309	277
Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	63	63
Exelon Generation Co L L C [Member] | Accrual For MGP Investigation And Remediation [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	0	0
Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	269	238
Other Increase (Decrease) in Environmental Liabilities	50
Commonwealth Edison Co [Member] | Accrual For MGP Investigation And Remediation [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	268	235
PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	41	45
Other Increase (Decrease) in Environmental Liabilities	1
PECO Energy Co [Member] | Accrual For MGP Investigation And Remediation [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	39	42
Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	3	1
Baltimore Gas and Electric Company [Member] | Accrual For MGP Investigation And Remediation [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	$ 2	$ 0

Supplemental Financial Infor104

Supplemental Financial Information - Narrative (Details) - PECO Energy Co [Member] - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014
Supplemental Financial Information Tables [Line Items]
Smart Grid Grant Project Capital Expenditures	$ 2
Smart Grid Grant Reimbursements	$ 5
Financing Receivable, Net		$ 15
Financing Receivable, Allowance for Credit Losses		17	$ 15
Low To Medium Risk [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Allowance for Credit Losses		1	1
Risk Level, Medium [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Allowance for Credit Losses		4	3
Risk Level, High [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Allowance for Credit Losses		$ 12	$ 11

Supplemental Financial Infor105

Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]	$ 39		$ 55		$ 203		$ 167
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[1]	18		39		122		102
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units		(301)		(107)		(385)		126
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement		(218)		(41)		(274)		100
Net unrealized income (losses) on pledged assets				7		9		27
Regulatory offset to decommissioning trust fund-related activities	[2]	207		29		129		(270)
Total decommissioning-related activities		(255)		(18)		(196)		252
Investment income		4		0		6		1
Long-term lease income		4		4		12		20
Interest income related to uncertain income tax positions				25		0		41
AFUDC - equity		6		5		16		17
Gain (Loss) on Sale of Derivatives	[3]					(26)
Other Income		(3)		0		9		15
Other, net		(244)		16		(179)		346
Exelon Generation Co L L C [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]	39		55		203		167
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[1]	18		39		122		102
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units		(301)		(107)		(385)		126
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement		(218)		(41)		(274)		100
Net unrealized income (losses) on pledged assets				7		9		27
Regulatory offset to decommissioning trust fund-related activities	[2]	207		29		129		(270)
Total decommissioning-related activities		(255)		(18)		(196)		252
Investment income		1		0		1		1
Long-term lease income		0		0		0		0
Interest income related to uncertain income tax positions				27		1		53
AFUDC - equity						0		0
Gain (Loss) on Sale of Derivatives	[3]					0
Other Income		(3)		(5)		1		0
Other, net		(257)		4		(193)		306
Commonwealth Edison Co [Member]
Decommissioning-Related Activities [Abstract]
Investment income		0				0
Interest income related to uncertain income tax positions						0		0
AFUDC - equity		1		0		2		3
Other Income		3		4		12		11
Other, net		4		4		14		14
PECO Energy Co [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]	0		0		0		0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[1]	0		0		0		0
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units		0		0		0		0
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement		0		0		0		0
Net unrealized income (losses) on pledged assets				0		0		0
Regulatory offset to decommissioning trust fund-related activities	[2]	0		0		0		0
Total decommissioning-related activities		0		0		0		0
Investment income		(1)		0		(1)		(1)
Long-term lease income		0		0		0		0
Interest income related to uncertain income tax positions						0		0
AFUDC - equity		1		2		4		5
Gain (Loss) on Disposition of Assets		0		0		1
Gain (Loss) on Sale of Derivatives	[3]					0
Other Income		1		0		0		1
Other, net		1		2		3		5
Baltimore Gas and Electric Company [Member]
Decommissioning-Related Activities [Abstract]
Investment income		1	[4]	1	[4]	3	[4]	5
Long-term lease income								0
Interest income related to uncertain income tax positions						0		0
AFUDC - equity		4		3		10		9
Gain (Loss) on Disposition of Assets		1				1
Other Income		(1)		0		0		0
Other, net		$ 4		$ 4		13		$ 14
Reclassification out of Accumulated Other Comprehensive Income [Member]
Decommissioning-Related Activities [Abstract]
Gain (Loss) on Sale of Derivatives	[3]					$ 26
[1]	Includes investment income and realized gains and losses on sales of investments of the trust funds.
[2]	Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of net income taxes related to all NDT fund activity for those units. See Note 15 — Asset Retirement Obligations of the Exelon 2014 Form 10-K for additional information regarding the accounting for nuclear decommissioning.
[3]	In January 2015, in connection with Generation's $750 million issuance of five-year Senior Unsecured Notes, Exelon terminated certain floating-to-fixed interest rate swaps. As the original forecasted transactions were a series of future interest payments over a ten year period, a portion of the anticipated interest payments are probable not to occur. As a result, $26 million of anticipated payments were reclassified from Accumulated OCI to Other, net in Exelon's Consolidated Statement of Operations and Comprehensive Income.
[4]	Relates to the cash return on BGE’s rate stabilization deferral. See Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K for additional information regarding the rate stabilization deferral.

Supplemental Financial Infor106

Supplemental Financial Information - Cash Flow (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015		Sep. 30, 2014
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment				$ 1,648		$ 1,549
Regulatory assets				131		150
Amortization of intangible assets, net				39		33
Amortization of energy contract assets and liabilities	[1]			(20)		83
Nuclear fuel	[2]			841		790
Asset retirement obligation accretion	[3]			291		251
Total depreciation, amortization and accretion				2,930		2,856
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				476		437
Gain (loss) on equity method investments			$ 0	3		20
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions		$ 1		3
Provision for uncollectible accounts				114		96
Stock-based compensation costs				102		111
Other Decommissioning Related Activity	[4]			(31)		(102)
Energy-related options				18	[5]	92
Amortization of regulatory asset related to debt costs						8
Amortization of rate stabilization deferral				60		50
Amortization of debt fair value adjustment				34		45
Discrete impacts from EIMA	[6]			101		(32)
Amortization of debt costs				43		36
Non Cash Increase in Inventory Reserve				7
Merger related commitments						44
Inventory Write-down				15
Tangible Asset Impairment Charges		24
Other Noncash Income Expense Net				(18)		(17)
Total other noncash operating activities				856		698
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs				47		53
Other regulatory assets and liabilities				(12)		(63)
Increase (Decrease) in Deposits				(190)	[7]	(280)
Increase (Decrease) in Other Current Liabilities				(132)
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net				193
Other current assets and liabilities						(78)
Other noncurrent assets and liabilities						(168)
Total changes in other assets and liabilities				(480)		(536)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						3,400
Capital Expenditures Incurred but Not yet Paid				59		(73)
Non Cash Licensing Agreement				95
Consolidated VIE dividend to non-controlling interest				0
Costs Incurred, Asset Retirement Obligation Incurred				(811)		(91)
Stock Issued						131
Indemnification Agreement [Member]
Other Non-Cash Operating Activities [Abstract]
Energy-related options						70
Exelon Generation Co L L C [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment				739		686
Regulatory assets				0		0
Amortization of intangible assets, net				35		33
Amortization of energy contract assets and liabilities	[1]			(19)		93
Nuclear fuel	[2]			841		790
Asset retirement obligation accretion	[3]			291		251
Total depreciation, amortization and accretion				1,887		1,853
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				200		193
Gain (loss) on equity method investments			(1)	4		20
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions		$ 1		4
Provision for uncollectible accounts				15		10
Stock-based compensation costs				0		0
Other Decommissioning Related Activity	[4]			(31)		(102)
Energy-related options	[5]			18		92
Amortization of regulatory asset related to debt costs						0
Amortization of rate stabilization deferral				0		0
Amortization of debt fair value adjustment				9		17
Discrete impacts from EIMA				0		0
Amortization of debt costs				12		9
Non Cash Increase in Inventory Reserve				8
Merger related commitments						44
Inventory Write-down				15
Tangible Asset Impairment Charges			$ 86
Other Noncash Income Expense Net				(5)		2
Total other noncash operating activities				227		251
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs				0
Other regulatory assets and liabilities				0
Increase (Decrease) in Deposits				(190)	[7]	(280)
Increase (Decrease) in Other Current Liabilities				(143)
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net				92
Other current assets and liabilities						24
Other noncurrent assets and liabilities						(111)
Total changes in other assets and liabilities				(425)		(367)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						3,400
Capital Expenditures Incurred but Not yet Paid				48		(100)
Consolidated VIE dividend to non-controlling interest				0
Costs Incurred, Asset Retirement Obligation Incurred				(811)		(91)
Exelon Generation Co L L C [Member] | Indemnification Agreement [Member]
Other Non-Cash Operating Activities [Abstract]
Energy-related options						70
Commonwealth Edison Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment				471		438
Regulatory assets				57		83
Total depreciation, amortization and accretion				528		521
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				155		129
Provision for uncollectible accounts				46		9
Stock-based compensation costs				0
Energy-related options	[5]					0
Amortization of regulatory asset related to debt costs						0
Discrete impacts from EIMA	[6]			101		(32)
Amortization of debt costs				3		4
Inventory Write-down				0
Other Noncash Income Expense Net				7		6
Total other noncash operating activities				312		116
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs				27		63
Other regulatory assets and liabilities				29		(14)
Increase (Decrease) in Deposits				0
Increase (Decrease) in Other Current Liabilities				2
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net				65
Other current assets and liabilities						(9)
Other noncurrent assets and liabilities						22
Total changes in other assets and liabilities				(7)		62
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid				62		13
Indemnification of like-kind exchange position				75		168
Commonwealth Edison Co [Member] | Indemnification Agreement [Member]
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Indemnification of like-kind exchange position	[8]			5		4
PECO Energy Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment				179		169
Regulatory assets				19		7
Amortization of intangible assets, net				0		0
Amortization of energy contract assets and liabilities	[1]			0		0
Nuclear fuel	[2]			0		0
Asset retirement obligation accretion	[3]			0		0
Total depreciation, amortization and accretion				198		176
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				29		28
Gain (loss) on equity method investments				0		0
Provision for uncollectible accounts				37		39
Stock-based compensation costs				0		0
Other Decommissioning Related Activity				0	[4]	0
Energy-related options	[5]			0		0
Amortization of regulatory asset related to debt costs						0
Amortization of rate stabilization deferral				0		0
Amortization of debt fair value adjustment				0		0
Discrete impacts from EIMA				0		0
Amortization of debt costs				2		2
Merger related commitments						0
Inventory Write-down				0
Other Noncash Income Expense Net				1		1
Total other noncash operating activities				69		70
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs				12		(14)
Other regulatory assets and liabilities				(4)		(14)
Increase (Decrease) in Deposits				0		0
Increase (Decrease) in Other Current Liabilities	[9]			(23)
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net				3
Other current assets and liabilities	[9]					(48)
Other noncurrent assets and liabilities						1
Total changes in other assets and liabilities				(18)		(75)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						0
Capital Expenditures Incurred but Not yet Paid				23		(13)
PECO Energy Co [Member] | Indemnification Agreement [Member]
Other Non-Cash Operating Activities [Abstract]
Energy-related options						0
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Indemnification of like-kind exchange position	[8]			0		0
Baltimore Gas and Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment				216		215
Regulatory assets				55		60
Total depreciation, amortization and accretion				271		275
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				49		50
Gain (loss) on equity method investments						0
Provision for uncollectible accounts				15		38
Stock-based compensation costs				0		0
Other Decommissioning Related Activity						0
Energy-related options	[5]					0
Amortization of regulatory asset related to debt costs						0
Amortization of rate stabilization deferral				60		50
Amortization of debt fair value adjustment						0
Discrete impacts from EIMA						0
Amortization of debt costs				2		2
Merger related commitments						0
Inventory Write-down				0
Other Noncash Income Expense Net				(15)		(11)
Total other noncash operating activities				111		129
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs				8		6
Other regulatory assets and liabilities				(106)		(89)
Increase (Decrease) in Deposits				0
Increase (Decrease) in Other Current Liabilities				55
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net				0
Other current assets and liabilities						25
Other noncurrent assets and liabilities						(9)
Total changes in other assets and liabilities				(43)		(67)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital Expenditures Incurred but Not yet Paid				14		$ 31
Indemnification of like-kind exchange position				$ 6
[1]	Included in Operating revenues or Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
[2]	Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
[3]	Included in Operating and maintenance expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
[4]	Includes the elimination of NDT fund activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 15 — Asset Retirement Obligations of the Exelon 2014 Form 10-K for additional information regarding the accounting for nuclear decommissioning.
[5]	Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations.
[6]	Reflects the change in distribution rates pursuant to EIMA, which allows for the recovery of costs by a utility through a pre-established performance-based formula rate tariff. See Note 5 — Regulatory Matters for more information.
[7]	Relates primarily to cash deposits made to ISOs/RTOs.
[8]	See Note 12 — Income Taxes for discussion of the like-kind exchange tax position
[9]	Relates primarily to prepaid utility taxes.

Supplemental Financial Infor107

Supplemental Financial Information - Balance Sheet (Details) - USD ($) $ in Millions		9 Months Ended		12 Months Ended
		Sep. 30, 2015		Dec. 31, 2014
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		$ 16,185	[1]	$ 14,742	[2]
Accounts receivable, net
Allowance for uncollectible accounts		329		311
Exelon Generation Co L L C [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		8,659	[1]	7,612	[2]
Accounts receivable, net
Allowance for uncollectible accounts		70		60
Accumulated amortization of nuclear fuel		3,093		2,673
Commonwealth Edison Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		3,614		3,432
Accounts receivable, net
Allowance for uncollectible accounts		100		84
PECO Energy Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		3,058		2,917
Accounts receivable, net
Allowance for uncollectible accounts	[3]	98		100
Financing Receivable, Allowance for Credit Losses		17		15
CurrentFinancingReceivableAllowanceForCreditLosses		9		7
Baltimore Gas and Electric Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		2,962		2,868
Accounts receivable, net
Allowance for uncollectible accounts		$ 61		$ 67
[1]	Includes accumulated amortization of nuclear fuel in the reactor core of $3,093 million.
[2]	Includes accumulated amortization of nuclear fuel in the reactor core of $2,673 million.
[3]	Excludes the non-current allowance for uncollectible accounts related to PECO's installment plan receivables described below of $9 million and $7 million at September 30, 2015 and December 31, 2014, respectively.

Segment Information - Narrative

Segment Information - Narrative (Details)	9 Months Ended
	Sep. 30, 2015Reportable_segment
Segment Reporting Information [Line Items]
Number of reportable segments	9
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	6

Segment Information - Reconcili

Segment Information - Reconciliation to Consolidated Financial Statements (Details) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014		Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues		$ 7,401	[1]	$ 6,912	[1]	$ 22,746	[2]	$ 20,173	[2]
Net income (loss)		587		1,074		1,959		1,725
Operating revenues from affiliates		2	[3]	0	[3]	3		0
Assets		95,128				95,128				$ 86,814
Operating Segments [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenues		4,768	[1]	4,412	[1]	14,841	[2],[4],[5]	12,591	[2],[4],[5]
Net income (loss)		332		849		1,208	[4],[5]	1,037	[4],[5]
Operating revenues from affiliates		205	[3]	112	[3]	567	[4],[5]	630	[4],[5]
Assets		46,479				46,479				45,348
Utility Taxes		28		22		79		67
Operating Segments [Member] | Commonwealth Edison Co [Member]
Segment Reporting Information [Line Items]
Revenues		1,376	[1]	1,222	[1]	3,709	[2]	3,484	[2]
Net income (loss)		149		126		339		335
Operating revenues from affiliates		1	[3]	1	[3]	3		2
Assets		26,129				26,129				25,392
Utility Taxes		63		61		180		180
Operating Segments [Member] | PECO Energy Co [Member]
Segment Reporting Information [Line Items]
Revenues		740	[1]	693	[1]	2,386	[2]	2,343	[2]
Net income (loss)		90		81		299		255
Operating revenues from affiliates		1	[3]	0	[3]	1		1
Assets		10,072				10,072				9,943
Utility Taxes		37		34		104		99
Operating Segments [Member] | Baltimore Gas and Electric Company [Member]
Segment Reporting Information [Line Items]
Revenues		725	[1]	697	[1]	2,388	[2]	2,404	[2]
Net income (loss)		54		49		212		156
Operating revenues from affiliates		3	[3]	3	[3]	10		21
Assets		8,134				8,134				8,078
Utility Taxes		23		21		67		64
Operating Segments [Member] | PECO Energy Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		61		28		173		165
Operating Segments [Member] | Baltimore Gas And Electric Company Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		141		83		376		290
Operating Segments [Member] | Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		2		1		17		175
Other Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues		348	[1],[6]	305	[1],[6]	1,007	[2],[7]	924	[2],[7]
Net income (loss)		(36)	[6]	(31)	[6]	(96)	[7]	(58)	[7]
Operating revenues from affiliates		347	[3],[6]	302	[3],[6]	1,003	[7]	920	[7]
Assets	[6]	16,256				16,256				9,794
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		0
Intersegment Eliminations [Member] | Segment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues		(556)	[1]	(417)	[1]	(1,585)	[2]	(1,573)	[2]
Net income (loss)		(2)		0		(3)		0
Operating revenues from affiliates		(555)	[3]	$ (418)	[3]	(1,581)		$ (1,574)
Assets		$ (11,942)				$ (11,942)				$ (11,741)
[1]	(c)For the three months ended September 30, 2015 and 2014, utility taxes of $28 million and $22 million, respectively, are included in revenues and expenses for Generation. For the three months ended September 30, 2015 and 2014, utility taxes of $63 million and $61 million, respectively, are included in revenues and expenses for ComEd. For the three months ended September 30, 2015 and 2014, utility taxes of $37 million and $34 million, respectively, are included in revenues and expenses for PECO. For the three months ended September 30, 2015 and 2014, utility taxes of $23 million and $21 million, respectively, are included in revenues and expenses for BGE.
[2]	(d)Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.
[3]	(d)Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.
[4]	(a)Generation includes the six power marketing reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. Intersegment revenues for Generation for the nine months ended September 30, 2015 include revenue from sales to PECO of $173 million and sales to BGE of $376 million in the Mid-Atlantic region, and sales to ComEd of $17 million in the Midwest. For the nine months ended September 30, 2014, intersegment revenues for Generation include revenue from sales to PECO of $165 million and sales to BGE of $290 million in the Mid-Atlantic region, and sales to ComEd of $175 million in the Midwest region.
[5]	(b)Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities.
[6]	(b)Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities.
[7]	(c)For the nine months ended September 30, 2015 and 2014, utility taxes of $79 million and $67 million, respectively, are included in revenues and expenses for Generation. For the nine months ended September 30, 2015 and 2014, utility taxes of $180 million and $180 million, respectively, are included in revenues and expenses for ComEd. For the nine months ended September 30, 2015 and 2014, utility taxes of $104 million and $99 million, respectively, are included in revenues and expenses for PECO. For the nine months ended September 30, 2015 and 2014, utility taxes of $67 million and $64 million, respectively, are included in revenues and expenses for BGE.

Segment Information - Generatio

Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions		3 Months Ended				9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014
Segment Reporting Information [Line Items]
Revenues		$ 7,401	[1]	$ 6,912	[1]	$ 22,746	[2]	$ 20,173	[2]
Revenue from Related Parties		2	[3]	0	[3]	3		0
Net income (loss)		587		1,074		1,959		1,725
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Unrealized Gain (Loss) on Commodity Contracts		(7)		271		171		(572)
Revenues		4,768		4,412		14,841		12,591
Revenue from Related Parties		206		112		571		647
Net income (loss)		332		849		1,208		1,037
Amortization of Intangible Assets		(3)		(22)		(19)		(203)
Exelon Generation Co L L C [Member] | Sales Revenue, Goods, Net [Member]
Segment Reporting Information [Line Items]
Unrealized Gain (Loss) on Commodity Contracts		(139)		267		(258)		477
Amortization of Intangible Assets		(4)		(15)		(20)		(78)
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		0
Segment Elimination [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(556)	[1]	(417)	[1]	(1,585)	[2]	(1,573)	[2]
Revenue from Related Parties		(555)	[3]	(418)	[3]	(1,581)		(1,574)
Net income (loss)		(2)		0		(3)		0
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues		1,632		1,289		4,491		3,984
Generation Mid Atlantic [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		1,622		1,285		4,475		3,998
Generation Mid Atlantic [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		10		4		16		(14)
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues		1,151		1,061		3,633		3,313
Generation Midwest [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		1,150		1,062		3,630		3,302
Generation Midwest [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		1		(1)		3		11
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues		520		272		1,746		1,033
Generation New England [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		519		272		1,743		1,028
Generation New England [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		1		0		3		5
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues		250		232		778		613
Generation New York [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		254		230		786		614
Generation New York [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(4)		2		(8)		(1)
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues		316		302		687		741
Generation ERCOT [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		317		303		691		743
Generation ERCOT [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(1)		(1)		(4)		(2)
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues		376		375		880		1,023
Generation Other Regions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		383		381		891		1,027
Generation Other Regions [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(7)		(6)		(11)		(4)
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues		4,245		3,531		12,215		10,707
Generation Reportable Segments Total [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	[4]	4,245		3,533		12,216		10,712
Generation Reportable Segments Total [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		0		(2)		(1)		(5)
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues		523		881		2,626		1,884
Generation All Other Segments [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		523		879	[4],[5]	2,625		1,879
Generation All Other Segments [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		0		2	[5]	1		5
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	[4]	4,768		4,412		14,841		12,591
Generation Total Consolidated Group [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues				0		0		0
Exelon Generation Co L L C [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		4,768	[1]	4,412	[1]	14,841	[2],[6],[7]	12,591	[2],[6],[7]
Revenue from Related Parties		205	[3]	112	[3]	567	[6],[7]	630	[6],[7]
Net income (loss)		332		849		1,208	[6],[7]	1,037	[6],[7]
Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		$ 2		$ 1		$ 17		$ 175
[1]	(c)For the three months ended September 30, 2015 and 2014, utility taxes of $28 million and $22 million, respectively, are included in revenues and expenses for Generation. For the three months ended September 30, 2015 and 2014, utility taxes of $63 million and $61 million, respectively, are included in revenues and expenses for ComEd. For the three months ended September 30, 2015 and 2014, utility taxes of $37 million and $34 million, respectively, are included in revenues and expenses for PECO. For the three months ended September 30, 2015 and 2014, utility taxes of $23 million and $21 million, respectively, are included in revenues and expenses for BGE.
[2]	(d)Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.
[3]	(d)Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.
[4]	(a)Includes all electric sales to third parties and affiliated sales to ComEd, PECO and BGE.
[5]	(c)Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $3 million decrease to revenues and a $22 million decrease to revenues for the amortization of intangible assets related to commodity contracts for the three months ended September 30, 2015 and 2014, respectively, unrealized mark-to-market losses of $7 million and gains of $271 million for the three months ended September 30, 2015 and 2014, respectively, and the elimination of intersegment revenues.
[6]	(a)Generation includes the six power marketing reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. Intersegment revenues for Generation for the nine months ended September 30, 2015 include revenue from sales to PECO of $173 million and sales to BGE of $376 million in the Mid-Atlantic region, and sales to ComEd of $17 million in the Midwest. For the nine months ended September 30, 2014, intersegment revenues for Generation include revenue from sales to PECO of $165 million and sales to BGE of $290 million in the Mid-Atlantic region, and sales to ComEd of $175 million in the Midwest region.
[7]	(b)Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities.

Segment Information - Genera111

Segment Information - Generation Total Revenues Net of Purchased Power and Fuel Expense (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2015		Sep. 30, 2014		Sep. 30, 2015		Sep. 30, 2014
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Amortization of Intangible Assets	$ 3		$ 22		$ 19		$ 203
Unrealized Gain (Loss) on Commodity Contracts	(7)		271		171		(572)
Sales Revenue, Goods, Net [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Amortization of Intangible Assets	4		15		20		78
Unrealized Gain (Loss) on Commodity Contracts	(139)		267		(258)		477
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	2,249		2,532		7,041		5,520
Generation Total Consolidated Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	2,249		2,532		7,041	[1]	5,520	[1]
Generation Total Consolidated Group [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	0		0		0		0
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	991		935		2,663		2,550
Generation Mid Atlantic [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	974	[1]	921	[1]	2,633		2,610
Generation Mid Atlantic [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	17	[1]	14		30		(60)
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	752		716		2,195		1,877
Generation Midwest [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	752	[1]	722	[1]	2,198		1,856
Generation Midwest [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	0		(6)		(3)		21
Generation New England [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	133		90		379		290
Generation New England [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	145	[1]	120	[1]	416		362
Generation New England [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	(12)		(30)		(37)		(72)
Generation New York [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	167		186		498		313
Generation New York [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	159	[1]	176	[1]	471		289
Generation New York [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	8		10		27		24
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	111		109		235		250
Generation ERCOT [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	166	[1]	186	[1]	344		457
Generation ERCOT [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	(55)		(77)		(109)		(207)
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	83		68		193		249
Generation Other Regions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	167	[1]	157	[1]	403		465
Generation Other Regions [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	(84)		(89)		(210)		(216)
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	2,237		2,104		6,163		5,529
Generation Reportable Segments Total [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	2,363		2,282		6,465	[1]	6,039	[1]
Generation Reportable Segments Total [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	(126)		(178)		(302)		(510)
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	12	[2]	428	[2]	878		(9)
Generation All Other Segments [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	(114)	[1],[2]	250	[1],[2]	576		(519)
Generation All Other Segments [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	$ 126	[2]	$ 178	[2]	$ 302		$ 510
[1]	(a)Includes purchases and sales from third parties and affiliated sales to ComEd, PECO and BGE.
[2]	(c)Other represents activities not allocated to a region. See text above for a description of included activities. Also includes a $4 million decrease to RNF and a $15 million increase to RNF for the amortization of intangible assets related to commodity contracts for the three months ended September 30, 2015 and 2014, respectively, unrealized mark-to-market losses of $139 million and gains of $267 million for the three months ended September 30, 2015 and 2014, respectively, and the elimination of intersegment revenues.

Uncategorized Items - exc-20150

Label	Element	Value
Baltimore Gas and Electric Company [Member] | Stride Program [Member]
Captial and OM estimates current year	exc_CapitalandOMestimatescurrentyear	$ 78
Regulatory Liabilities	us-gaap_RegulatoryLiabilities	1
Exelon Generation Co L L C [Member]
Allocation Of Tax Benefit From Members	exc_AllocationOfTaxBenefitFromMembers	55
Membership Interest [Member] | Exelon Generation Co L L C [Member]
Allocation Of Tax Benefit From Members	exc_AllocationOfTaxBenefitFromMembers	$ 55