Peco Energy 10-Q 29 Jul 15 2015 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - Jun. 30, 2015 - shares	Total
Entity Registrant Name	EXELON CORP
Entity Central Index Key	1,109,357
Document Type	10-Q
Document Period End Date	Jun. 30, 2015
Amendment Flag	false
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q2
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	861,617,731
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				6 Months Ended
	Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014
Operating revenues [Abstract]
Operating revenues from affiliates	$ 1	[1]	$ 0	[1]	$ 3		$ 0
Total Revenues	6,514	[2]	6,024	[2]	15,345	[3]	13,261	[3]
Operating expenses
Purchased power and fuel	2,449		2,346		6,919		6,352
Purchased power and fuel from affiliates	0		66		0		400
Operating and maintenance	2,042		2,166		4,123		4,024
Depreciation and amortization	602		590		1,212		1,154
Taxes other than income	294		288		598		580
Total operating expenses	5,387		5,456		12,852		12,510
Equity in losses of unconsolidated affiliates	0		0		(2)		(20)
Gain (Loss) on Sale of Assets and Asset Impairment Charges	7		13		8		18
Gain on consolidation and acquisition of businesses	0		261				261
Operating income	1,134		842		2,501		1,010
Other income and (deductions)
Interest expense, net	(145)		(228)		(480)		(445)
Interest expense to affiliates	(10)		(10)		(21)		(20)
Other, net	(17)		230		64		330
Total other income and (deductions)	(172)		(8)		(437)		(135)
Income before income taxes	962		834		2,064		875
Income taxes	327		277		690		224
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions	(2)		0		(2)		0
Net income	633		557		1,372		651
Net income (loss) attributable to noncontrolling interest and preference stock dividends	(5)		35		41		39
Net income attributable to common shareholders	638		522		1,331		612
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost	(11)		(6)		(23)		(6)
Actuarial loss reclassified to periodic cost	55		38		110		72
Pension and non-pension postretirement benefit plans valuation adjustment	0		258		(29)		246
Unrealized gain (loss) on cash flow hedges	3		(48)		9		(73)
Unrealized gain on equity investments	0		0		0		11
Unrealized gain (loss) on foreign currency translation	3		4		(9)		(1)
Unrealized loss on marketable securities	0		1		0		1
Reversal of CENG equity method AOCI	0		(116)		0		(116)
Other comprehensive income	50		131		58	[4]	134	[4]
Comprehensive income	$ 683		$ 688		$ 1,430		$ 785
Average shares of common stock outstanding:
Average common shares outstanding — basic	863		860		862		860
Average common shares outstanding — diluted	866		864		866		863
Earnings per average common share:
Earnings per share - basic (in usd per share)	$ 0.74		$ 0.61		$ 1.54		$ 0.71
Earnings per average common share - diluted
Earnings per share - diluted (in usd per share)	0.74		0.60		1.54		0.71
Dividends per common share (in usd per share)	$ 0.31		$ 0.31		$ 0.62		$ 0.62
Exelon Generation Co L L C [Member]
Operating revenues [Abstract]
Operating revenues	$ 4,079		$ 3,588		$ 9,709		$ 7,644
Operating revenues from affiliates	153		201		365		535
Total Revenues	4,232		3,789		10,074		8,179
Operating expenses
Purchased power and fuel from affiliates	1		69		8		417
Purchased power and fuel	1,848		1,766		5,274		4,774
Operating and maintenance	1,149		1,255		2,311		2,194
Operating and maintenance from affiliates	159		158		308		305
Depreciation and amortization	255		254		509		466
Taxes other than income	124		118		246		223
Total operating expenses	3,536		3,620		8,656		8,379
Equity in losses of unconsolidated affiliates			(1)		(3)		(20)
Gain (Loss) on Sale of Assets and Asset Impairment Charges	7		12		6		18
Gain on consolidation and acquisition of businesses	0		261		0		261
Operating income	703		441		1,424		59
Other income and (deductions)
Interest expense, net	(90)		(74)		(180)		(147)
Interest expense to affiliates	(9)		(12)		(21)		(25)
Other, net	(31)		216		62		300
Total other income and (deductions)	(130)		130		(139)		128
Income before income taxes	573		571		1,285		187
Income taxes	181		199		407		(1)
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions	(2)				(3)
Net income	390		372		875		188
Net (loss) income attributable to noncontrolling interests	(8)		32		34		33
Net income attributable to membership interest	398		340		841		155
Pension and non-pension postretirement benefit plans:
Unrealized gain (loss) on cash flow hedges	2		(45)		(3)		(70)
Unrealized gain on equity investments	0		0		0		11
Unrealized gain (loss) on foreign currency translation	3		4		(9)		(1)
Unrealized loss on marketable securities	1		2		1		(1)
Reversal of CENG equity method AOCI	0		(116)		0		(116)
Other comprehensive income	6		(155)		(11)	[4]	(177)	[4]
Comprehensive income	396		217		864		11
Commonwealth Edison Co [Member]
Operating revenues [Abstract]
Operating revenues	1,147		1,128		2,331		2,261
Operating revenues from affiliates	1		0		2		1
Total Revenues	1,148		1,128		2,333		2,262
Operating expenses
Purchased power and fuel	269		204		586		416
Purchased power and fuel from affiliates	6		65		15		173
Operating and maintenance	337		316		670		603
Operating and maintenance from affiliates	47		39		92		78
Depreciation and amortization	177		174		352		347
Taxes other than income	69		72		146		149
Total operating expenses	905		870		1,861		1,766
Operating income	243		258		472		496
Other income and (deductions)
Interest expense, net	(78)		(76)		(158)		(153)
Interest expense to affiliates	(3)		(4)		(7)		(7)
Other, net	5		5		9		10
Total other income and (deductions)	(76)		(75)		(156)		(150)
Income before income taxes	167		183		316		346
Income taxes	68		72		127		137
Net income	99		111		189		209
Pension and non-pension postretirement benefit plans:
Comprehensive income	99		111		189		209
PECO Energy Co [Member]
Operating revenues [Abstract]
Operating revenues	661		656		1,645		1,648
Operating revenues from affiliates	0		0		1		1
Total Revenues	661		656		1,646		1,649
Operating expenses
Purchased power and fuel	189		193		565		570
Purchased power and fuel from affiliates	48		48		110		135
Operating and maintenance	166		160		363		416
Operating and maintenance from affiliates	26		24		51		48
Depreciation and amortization	69		59		131		117
Taxes other than income	39		38		80		80
Total operating expenses	537		522		1,300		1,366
Equity in losses of unconsolidated affiliates							0
Gain (Loss) on Sale of Assets and Asset Impairment Charges							0
Gain (Loss) on Disposition of Assets					1
Operating income	124		134		347		283
Other income and (deductions)
Interest expense, net	(25)		(25)		(50)		(50)
Interest expense to affiliates	(3)		(3)		(6)		(6)
Other, net	1		1		3		3
Total other income and (deductions)	(27)		(27)		(53)		(53)
Income before income taxes	97		107		294		230
Income taxes	27		23		85		57
Net income					209		173
Net income attributable to common shareholders	70		84		209		173
Pension and non-pension postretirement benefit plans:
Comprehensive income	70		84		209		173
Baltimore Gas and Electric Company [Member]
Operating revenues [Abstract]
Operating revenues	627		651		1,656		1,689
Operating revenues from affiliates	1		2		8		18
Total Revenues	628		653		1,664		1,707
Operating expenses
Purchased power and fuel	143		183		493		592
Purchased power and fuel from affiliates	96		85		233		205
Operating and maintenance	120		163		276		326
Operating and maintenance from affiliates	29		25		55		50
Depreciation and amortization	87		89		192		197
Taxes other than income	54		53		111		113
Total operating expenses	529		598		1,360		1,483
Equity in losses of unconsolidated affiliates							0
Operating income	99		55		304		224
Other income and (deductions)
Interest expense, net	(20)		(23)		(42)		(47)
Interest expense to affiliates	(4)		(4)		(8)		(8)
Other, net	4		5		8		9
Total other income and (deductions)	(20)		(22)		(42)		(46)
Income before income taxes	79		33		262		178
Income taxes	32		14		105		72
Net income	47		19		157		106
Preferred security dividends and redemption	3		3		6		6
Net income attributable to common shareholders	44		16		151		100
Pension and non-pension postretirement benefit plans:
Comprehensive income	$ 47		$ 19		$ 157		$ 106
[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 June 30, 2015 and 2014, utility taxes of $24 million and $21 million, respectively, are included in revenues and expenses for Generation. For the three months ended June 30, 2015 and 2014, utility taxes of $55 million and $56 million, respectively, are included in revenues and expenses for ComEd. For the three months ended June 30, 2015 and 2014, utility taxes of $32 million and $30 million, respectively, are included in revenues and expenses for PECO. For the three months ended June 30, 2015 and 2014, utility taxes of $21 million and $19 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	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	$ 1,372	$ 651
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	1,957	1,925
Impairment of long-lived assets	24	112
Gain on consolidation and acquisition of businesses	0	(268)
Gain on sales of assets	(8)	(18)
Deferred income taxes and amortization of investment tax credits	211	133
Net fair value changes related to derivatives	(507)	751
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(2)	(168)
Other non-cash operating activities	579	473
Changes in assets and liabilities:
Accounts receivable	253	48
Inventories	159	(150)
Accounts payable, accrued expenses and other current liabilities	(668)	(358)
Option premiums received, net	22	21
Counterparty collateral received (posted), net	417	(606)
Income taxes	247	(16)
Pension and non-pension postretirement benefit contributions	(301)	(499)
Other assets and liabilities	214	(280)
Net cash flows provided by operating activities	3,969	1,751
Cash flows from investing activities
Capital expenditures	(3,460)	(2,501)
Proceeds from nuclear decommissioning trust fund sales	3,314	4,219
Investment in nuclear decommissioning trust funds	(3,437)	(4,238)
Acquisition of businesses	(28)	(66)
Proceeds from sale of long-lived assets	145	32
Proceeds from termination of direct financing lease investment	0	335
Change in restricted cash	(3)	(40)
Cash and restricted cash acquired from consolidations and acquisitions	0	129
Other investing activities	(77)	(57)
Net cash flows used in investing activities	(3,546)	(2,187)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	94	293
Issuance of long-term debt	5,907	2,100
Retirement of long-term debt	(1,708)	(1,191)
Distributions to noncontrolling interest of consolidated VIE	0	(415)
Dividends paid on common stock	(537)	(533)
Proceeds from employee stock plans	16	18
Other financing activities	(59)	(83)
Net cash flows provided by financing activities	3,713	189
Increase (decrease) in cash and cash equivalents	4,136	(247)
Cash and cash equivalents at beginning of period	1,878	1,609
Cash and cash equivalents at end of period	6,014	1,362
Exelon Generation Co L L C [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	875	188
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	1,255	1,242
Impairment of long-lived assets	(1)	88
Gain on consolidation and acquisition of businesses	0	(268)
Gain on sales of assets	(6)	(18)
Deferred income taxes and amortization of investment tax credits	65	(15)
Net fair value changes related to derivatives	(396)	760
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(2)	(168)
Other non-cash operating activities	134	139
Changes in assets and liabilities:
Accounts receivable	291	63
Receivables from and payables to affiliates, net	(11)	(20)
Inventories	134	(170)
Accounts payable, accrued expenses and other current liabilities	(485)	(273)
Option premiums received, net	22	21
Counterparty collateral received (posted), net	440	(633)
Income taxes	27	72
Pension and non-pension postretirement benefit contributions	(122)	(210)
Other assets and liabilities	203	(56)
Net cash flows provided by operating activities	2,423	742
Cash flows from investing activities
Capital expenditures	(1,764)	(1,103)
Proceeds from nuclear decommissioning trust fund sales	3,314	4,219
Investment in nuclear decommissioning trust funds	(3,437)	(4,238)
Proceeds from nuclear decommissioning trust fund sales	0
Acquisition of businesses	(28)	(66)
Proceeds from sale of long-lived assets	144	32
Change in restricted cash	(16)	(17)
Cash and restricted cash acquired from consolidations and acquisitions	0	129
Other investing activities	(63)	(14)
Changes in Exelon intercompany money pool	638	190
Funding of Exelon intercompany money pool		44
Net cash flows used in investing activities	(1,850)	(1,014)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	15	46
Issuance of long-term debt	1,307	300
Retirement of long-term debt	(39)	(538)
Repayments of Related Party Debt	(550)	0
Distributions to noncontrolling interest of consolidated VIE	0	(415)
Other financing activities	(6)	(29)
Distribution to member	(2,262)	(235)
Changes in Exelon intercompany money pool	638	190
Net cash flows provided by financing activities	(897)	(681)
Increase (decrease) in cash and cash equivalents	(324)	(953)
Cash and cash equivalents at beginning of period	780	1,258
Cash and cash equivalents at end of period	456	305
Commonwealth Edison Co [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	189	209
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	352	347
Deferred income taxes and amortization of investment tax credits	36	63
Other non-cash operating activities	222	99
Changes in assets and liabilities:
Accounts receivable	(57)	(83)
Receivables from and payables to affiliates, net	(10)	(46)
Inventories	(19)	(4)
Accounts payable, accrued expenses and other current liabilities	(52)	27
Income taxes	239	5
Pension and non-pension postretirement benefit contributions	(125)	(236)
Other assets and liabilities	25	48
Net cash flows provided by operating activities	800	429
Cash flows from investing activities
Capital expenditures	(1,061)	(747)
Proceeds from sales of investments	0	7
Purchases of investments	0	(3)
Change in restricted cash	0	(2)
Other investing activities	17	14
Net cash flows used in investing activities	(1,044)	(731)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	199	314
Issuance of long-term debt	400	650
Retirement of long-term debt	(260)	(617)
Dividends paid on common stock	(150)	(153)
Other financing activities	(5)	(2)
Contributions from parent	45	112
Net cash flows provided by financing activities	229	304
Increase (decrease) in cash and cash equivalents	(15)	2
Cash and cash equivalents at beginning of period	66	36
Cash and cash equivalents at end of period	51	38
PECO Energy Co [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	209	173
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	131	117
Gain on sales of assets		0
Deferred income taxes and amortization of investment tax credits	4	6
Other non-cash operating activities	45	50
Changes in assets and liabilities:
Accounts receivable	(18)	34
Receivables from and payables to affiliates, net	(2)	(21)
Inventories	21	22
Accounts payable, accrued expenses and other current liabilities	3	30
Income taxes	57	54
Pension and non-pension postretirement benefit contributions	(15)	(11)
Other assets and liabilities	(60)	(114)
Net cash flows provided by operating activities	375	340
Cash flows from investing activities
Capital expenditures	(289)	(308)
Change in restricted cash	(1)	0
Other investing activities	9	6
Changes in Exelon intercompany money pool	41	0
Net cash flows used in investing activities	(281)	(302)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Dividends paid on common stock	(139)	(160)
Other financing activities	0	(2)
Changes in Exelon intercompany money pool	41	0
Net cash flows provided by financing activities	(98)	(162)
Increase (decrease) in cash and cash equivalents	(4)	(124)
Cash and cash equivalents at beginning of period	30	217
Cash and cash equivalents at end of period	26	93
Baltimore Gas and Electric Company [Member]
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net income	157	106
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	192	197
Deferred income taxes and amortization of investment tax credits	54	47
Other non-cash operating activities	76	89
Changes in assets and liabilities:
Accounts receivable	25	44
Receivables from and payables to affiliates, net	(2)	(12)
Inventories	23	0
Accounts payable, accrued expenses and other current liabilities	(49)	(74)
Counterparty collateral received (posted), net	(23)	27
Income taxes	(6)	(14)
Pension and non-pension postretirement benefit contributions	(9)	(8)
Other assets and liabilities	51	8
Net cash flows provided by operating activities	489	410
Cash flows from investing activities
Capital expenditures	(304)	(313)
Change in restricted cash	21	(30)
Other investing activities	8	11
Net cash flows used in investing activities	(275)	(332)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Changes in short-term borrowings	(120)	(65)
Retirement of long-term debt	(37)	(35)
Dividends paid on common stock	(77)	0
Other financing activities	(14)	12
Contributions from parent	0
Proceeds from employee stock plans	(6)	(6)
Net cash flows provided by financing activities	(254)	(94)
Increase (decrease) in cash and cash equivalents	(40)	(16)
Cash and cash equivalents at beginning of period	64	31
Cash and cash equivalents at end of period	$ 24	$ 15

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Assets, Current [Abstract]
Cash and cash equivalents		$ 6,014	$ 1,878
Restricted cash and cash equivalents		274	271
Accounts receivable, net
Customer		3,227	3,482
Other		1,304	1,227
Mark-to-market derivative assets		1,405	1,279
Unamortized energy contract assets		156	254
Inventories, net
Fossil fuel and emission allowances		364	579
Materials and supplies		1,068	1,024
Deferred income taxes		173	244
Regulatory assets		785	847
Disposal Group, Including Discontinued Operation, Assets, Current		1	147
Other		654	865
Total current assets		15,425	12,097
Property, plant and equipment, net		53,935	52,087
Deferred debits and other assets
Regulatory assets		5,976	6,076
Nuclear decommissioning trust funds		10,607	10,537
Investments		607	544
Goodwill		2,672	2,672
Mark-to-market derivative assets		811	773
Unamortized energy contracts assets		526	549
Deferred Tax Assets, Net, Noncurrent		2	0
Pledged assets for Zion Station decommissioning		264	319
Other		1,388	1,160
Total deferred debits and other assets		22,853	22,630
Total assets		92,213	86,814
Liabilities, Current [Abstract]
Short-term borrowings		543	460
Long-term debt due within one year		226	1,802
Accounts payable		2,727	3,048
Accrued expenses		1,366	1,539
Regulatory liabilities		409	310
Mark-to-market derivative liabilities (current liabilities)		165	234
Unamortized energy contract liabilities		141	238
Other Liabilities, Current		941	1,123
Due to Affiliate, Current		8	8
Total current liabilities		6,526	8,762
Long-term debt		25,220	19,362
Long-term debt to financing trusts		648	648
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		13,309	13,019
Asset retirement obligations		7,550	7,295
Pension obligations		3,134	3,366
Non-pension postretirement benefit obligations		1,850	1,742
Spent nuclear fuel obligation		1,021	1,021
Regulatory liabilities		4,462	4,550
Mark-to-market derivative liabilities (noncurrent liabilities)		595	403
Unamortized energy contract liabilities		166	211
Payable for Zion Station decommissioning		135	155
Other		2,528	2,147
Total deferred credits and other liabilities		34,750	33,909
Total liabilities	[1]	$ 67,144	$ 62,681
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		$ 16,755	$ 16,709
Treasury stock, at cost (35 shares at both June 30, 2015 and December 31, 2014)		(2,327)	(2,327)
Retained earnings		11,704	10,910
Accumulated other comprehensive loss, net	[2]	(2,626)	(2,684)
Total shareholders’ equity		23,506	22,608
BGE preference stock not subject to mandatory redemption		193	193
Noncontrolling interest		1,370	1,332
Total equity		25,069	24,133
Total liabilities and shareholders’ equity		92,213	86,814
Member’s equity
Accumulated other comprehensive loss, net	[2]	(2,626)	(2,684)
Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		7,989	8,160
Deferred credits and other liabilities
Total liabilities		2,555	2,723
Exelon Generation Co L L C [Member]
Assets, Current [Abstract]
Cash and cash equivalents		456	780
Restricted cash and cash equivalents		174	158
Accounts receivable, net
Customer		2,045	2,295
Other		299	318
Mark-to-market derivative assets		1,405	1,276
Unamortized energy contract assets		156	254
Receivables from affiliates		103	113
Inventories, net
Fossil fuel and emission allowances		305	465
Materials and supplies		860	847
Deferred income taxes		188	327
Disposal Group, Including Discontinued Operation, Assets, Current		1	147
Other		451	658
Total current assets		6,443	7,638
Property, plant and equipment, net		23,766	22,945
Deferred debits and other assets
Nuclear decommissioning trust funds		10,607	10,537
Investments		183	104
Goodwill		47	47
Mark-to-market derivative assets		790	771
Unamortized energy contracts assets		526	549
Deferred Tax Assets, Net, Noncurrent		2	3
Pledged assets for Zion Station decommissioning		264	319
Other		798	731
Prepaid pension asset		1,699	1,704
Total deferred debits and other assets		14,916	14,765
Total assets	[3]	45,125	45,348
Liabilities, Current [Abstract]
Short-term borrowings		40	36
Long-term debt due within one year		89	58
Accounts payable		1,528	1,759
Accrued expenses		732	886
Mark-to-market derivative liabilities (current liabilities)		145	214
Unamortized energy contract liabilities		141	238
Other Liabilities, Current		453	605
Payables to affiliates		98	107
Related Party Transaction, Due from (to) Related Party		638	0
Due to Affiliate, Current		0	556
Total current liabilities		3,864	4,459
Long-term debt		7,974	6,709
Long-term debt to affiliate		938	943
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		6,009	6,034
Asset retirement obligations		7,399	7,146
Non-pension postretirement benefit obligations		922	915
Spent nuclear fuel obligation		1,021	1,021
Mark-to-market derivative liabilities (noncurrent liabilities)		392	105
Unamortized energy contract liabilities		166	211
Payable for Zion Station decommissioning		135	155
Other		817	719
Payables to affiliates		2,832	2,880
Total deferred credits and other liabilities		19,693	19,186
Total liabilities	[3]	$ 32,469	$ 31,297
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Accumulated other comprehensive loss, net	[2]	$ (47)	$ (36)
Noncontrolling interest		1,370	1,333
Member’s equity
Membership interest		8,951	8,951
Undistributed earnings		2,382	3,803
Accumulated other comprehensive loss, net	[2]	(47)	(36)
Total member's equity		11,286	12,718
Total equity		12,656	14,051
Total liabilities and equity		45,125	45,348
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		7,949	8,119
Deferred credits and other liabilities
Total liabilities		2,435	2,507
Commonwealth Edison Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents		51	66
Restricted cash and cash equivalents		4	4
Accounts receivable, net
Customer		522	477
Other		569	648
Receivables from affiliates		14	14
Inventories, net
Regulatory assets		276	349
Other		36	40
Inventories, net		144	125
Total current assets		1,616	1,723
Property, plant and equipment, net		16,493	15,793
Deferred debits and other assets
Regulatory assets		834	852
Goodwill		2,625	2,625
Other		283	277
Receivable from affiliate		2,538	2,571
Prepaid pension asset		1,572	1,551
Total deferred debits and other assets		7,852	7,876
Total assets		25,961	25,392
Liabilities, Current [Abstract]
Short-term borrowings		503	304
Long-term debt due within one year		0	260
Accounts payable		580	598
Accrued expenses		291	331
Deferred income taxes		20	63
Regulatory liabilities		154	125
Mark-to-market derivative liabilities (current liabilities)		20	20
Other Liabilities, Current		75	73
Customer deposits		128	128
Due to Affiliate, Current		73	84
Total current liabilities		1,844	1,986
Long-term debt		6,099	5,698
Long-term debt to financing trusts		206	206
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		4,579	4,498
Asset retirement obligations		103	103
Non-pension postretirement benefit obligations		262	263
Regulatory liabilities		3,622	3,655
Mark-to-market derivative liabilities (noncurrent liabilities)		203	187
Other		1,049	889
Total deferred credits and other liabilities		9,818	9,595
Total liabilities		$ 17,967	$ 17,485
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		$ 1,588	$ 1,588
Retained earnings		890	851
Other paid-in capital		5,516	5,468
Total shareholders’ equity		7,994	7,907
Total liabilities and shareholders’ equity		25,961	25,392
PECO Energy Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents		26	30
Restricted cash and cash equivalents		3	2
Accounts receivable, net
Customer		301	320
Other		122	141
Receivables from affiliates		3	3
Inventories, net
Fossil fuel and emission allowances		30	57
Materials and supplies		28	22
Deferred income taxes		69	69
Regulatory assets		42	29
Other		36	31
Prepaid utility taxes		80	10
Total current assets		740	714
Property, plant and equipment, net		6,957	6,801
Deferred debits and other assets
Regulatory assets		1,552	1,529
Investments		28	31
Other		31	34
Receivable from affiliate		477	490
Prepaid pension asset		341	344
Total deferred debits and other assets		2,429	2,428
Total assets		10,126	9,943
Liabilities, Current [Abstract]
Accounts payable		319	337
Accrued expenses		116	91
Regulatory liabilities		117	90
Other Liabilities, Current		41	31
Payables to affiliates		41	0
Customer deposits		54	52
Due to Affiliate, Current		50	52
Total current liabilities		738	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		2,724	2,671
Asset retirement obligations		30	29
Non-pension postretirement benefit obligations		287	287
Regulatory liabilities		633	657
Other		93	95
Total deferred credits and other liabilities		3,767	3,739
Total liabilities		$ 6,935	$ 6,822
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		$ 2,439	$ 2,439
Retained earnings		751	681
Accumulated other comprehensive loss, net	[2]	1	1
Total shareholders’ equity		3,191	3,121
Total liabilities and shareholders’ equity		10,126	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		24	64
Restricted cash and cash equivalents		29	50
Accounts receivable, net
Customer		360	390
Other		76	82
Inventories, net
Fossil fuel and emission allowances		29	57
Materials and supplies		35	30
Deferred income taxes		12	6
Regulatory assets		207	214
Other		4	5
Prepaid utility taxes		0	59
Total current assets		776	957
Property, plant and equipment, net		6,373	6,204
Deferred debits and other assets
Regulatory assets		486	510
Investments		13	12
Other		25	25
Prepaid pension asset		344	370
Total deferred debits and other assets		868	917
Total assets	[4]	8,017	8,078
Liabilities, Current [Abstract]
Short-term borrowings		0	120
Long-term debt due within one year		77	75
Accounts payable		194	215
Accrued expenses		108	131
Deferred income taxes		48	52
Regulatory liabilities		91	44
Other Liabilities, Current		33	51
Customer deposits		97	92
Due to Affiliate, Current		52	66
Total current liabilities		700	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		1,930	1,865
Asset retirement obligations		18	17
Non-pension postretirement benefit obligations		209	212
Regulatory liabilities		185	200
Other		62	60
Total deferred credits and other liabilities		2,404	2,354
Total liabilities	[4]	5,190	5,325
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		1,360	1,360
Retained earnings		1,277	1,203
Total shareholders’ equity		2,637	2,563
BGE preference stock not subject to mandatory redemption		190	190
Total equity		2,827	2,753
Total liabilities and shareholders' equity		8,017	8,078
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		27	24
Deferred credits and other liabilities
Total liabilities		$ 160	$ 197	[4]
[1]	Exelon’s consolidated assets include $7,989 million and $8,160 million at June 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 $2,555 million and $2,723 million at June 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 $7,949 million and $8,119 million at June 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 $2,435 million and $2,507 million at June 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 $27 million and $24 million at June 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 $160 million and $197 million at June 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	Jun. 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	861,243,550	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) - 6 months ended Jun. 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]	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]	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]	Baltimore Gas and Electric Company [Member]	Baltimore Gas and Electric Company [Member]Common Stock [Member]	Baltimore Gas and Electric Company [Member]Retained Earnings [Member]	Baltimore Gas and Electric Company [Member]Preferred Stock [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															$ 2,753
Beginning Balance at Dec. 31, 2014		22,608												$ 3,121	$ 2,439	$ 681	$ 1	$ 7,907	$ 1,588	$ 5,468	$ (1,639)	$ 2,490	2,563	$ 1,360	$ 1,203
Beginning Balance at Dec. 31, 2014									$ 14,051	$ 3,803	$ 8,951	$ (36)	$ 1,333
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		$ 1,372			1,331		35	6	875	841		0	34	209		209		189			189		157		157	$ 0
Noncontrolling Interest, Increase from Sale of Parent Equity Interest									3	0		0	3
Long-term incentive plan activity (in shares)		1,252
Long-term incentive plan activity		$ 29	29
Employee stock purchase plan issuances (in shares)		790
Employee stock purchase plan issuances		$ 16	16
Appropriation of retained earnings for future dividends																		0			(189)	189
Tax benefit on stock compensation		1	1
Common stock dividends		(537)			(537)			(6)						(139)		(139)		(150)				(150)	(77)		(77)
Contribution from parent																		45		45
Distribution to members									(2,262)	(2,262)		0	0
Allocation of tax benefit from parent																		3		3
Consolidated VIE dividend to non-controlling interest		0							0
Minority Interest Increase From Acquisition		3					3
Reversal of CENG equity method AOCI		0							0
Preferred security dividends		(6)																					(6)		(6)	0
Other comprehensive loss, net of income taxes of $53		58				58			(11)	0		(11)	0
Other comprehensive income (loss), net of tax	[1]	58							(11)
Ending Balance at Jun. 30, 2015									$ 12,656	$ 2,382	$ 8,951	$ (47)	$ 1,370
Ending Balance at Jun. 30, 2015		$ 25,069	$ 16,755	$ (2,327)	$ 11,704	$ (2,626)	$ 1,370	$ 193															2,827
Ending Balance (in shares) at Jun. 30, 2015		896,610
Ending Balance at Jun. 30, 2015		$ 23,506												$ 3,191	$ 2,439	$ 751	$ 1	$ 7,994	$ 1,588	$ 5,516	$ (1,639)	$ 2,529	$ 2,637	$ 1,360	$ 1,277	$ 190
[1]	All amounts are net of tax. Amounts in parentheses represent a decrease in accumulated other comprehensive income.

Basis of Presentation

Basis of Presentation	6 Months Ended
	Jun. 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. The accompanying consolidated financial statements as of June 30, 2015 and 2014 and for the six 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)	6 Months Ended
	Jun. 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 standards are not yet required to be reflected in the combined financial statements of the Registrants. 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 are currently assessing the impact this guidance may have 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 entity’s 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. 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 within annual reporting periods 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. As currently issued, the guidance is effective for the Registrants for the first interim period within annual reporting periods beginning on or after December 15, 2016; and early adoption would not be permitted. However, in July 2015, the FASB approved 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. As of July 29, 2015, the amendment to defer the effective date and provide an option to early adopt had not been issued.

Variable Interest Entities (Exe

Variable Interest Entities (Exelon, Generation, ComEd, PECO and BGE)	6 Months Ended
	Jun. 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 June 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 June 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 June 30, 2015 and December 31, 2014 , ComEd and PECO do not have any material consolidated VIEs. As of June 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 six months ended June 30, 2015 , BGE remitted $21 million and $42 million to BondCo, respectively. During the three and six months ended June 30, 2014, BGE remitted $21 million and $42 million to BondCo, respectively. • Generation provides operating and capital funding to the solar entities for ongoing construction, operations and maintenance of the solar power facilities and provides limited recourse 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 Reliability Support Services Agreement (RSSA) which Ginna entered into with Rochester Gas and Electric Corporation (RG&E) on February 13, 2015. The obligations under the RSSA commenced on April 1, 2015 and are effective through September 30, 2018 (see Note 5 — Regulatory Matters for additional details), • Generation provided a $400 million loan to CENG. As of June 30, 2015 , the remaining obligation is $288 million plus 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 June 30, 2015 , the remaining obligation is approximately $2 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 $8 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 June 30, 2015 and December 31, 2014 are as follows: June 30, 2015 December 31, 2014 Exelon (a) Generation BGE Exelon (a) Generation BGE Current assets $ 924 $ 894 $ 24 $ 1,271 $ 1,242 $ 21 Noncurrent assets 7,731 7,723 3 7,580 7,566 3 Total assets $ 8,655 $ 8,617 $ 27 $ 8,851 $ 8,808 $ 24 Current liabilities $ 378 $ 292 $ 79 $ 611 $ 526 $ 77 Noncurrent liabilities 2,860 2,773 81 2,730 2,600 120 Total liabilities $ 3,238 $ 3,065 $ 160 $ 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 June 30, 2015 and December 31, 2014 , these assets and liabilities primarily consisted of the following: June 30, 2015 December 31, 2014 Exelon Generation BGE Exelon Generation BGE Cash and cash equivalents $ 240 $ 240 $ — $ 392 $ 392 $ — Restricted cash 145 121 24 117 96 21 Accounts receivable, net Customer 179 179 — 297 297 — Other 29 29 — 57 57 — Mark-to-market derivatives assets 96 96 — 171 171 — Inventory Materials and supplies 178 178 — 172 172 — Other current assets 32 25 — 33 26 — Total current assets 899 868 24 1,239 1,211 21 Property, plant and equipment, net 4,811 4,811 — 4,638 4,638 — Nuclear decommissioning trust funds 2,096 2,096 — 2,097 2,097 — Goodwill 47 47 — 47 47 — Mark-to-market derivatives assets 45 45 — 44 44 — Other noncurrent assets 91 82 3 95 82 3 Total noncurrent assets 7,090 7,081 3 6,921 6,908 3 Total assets $ 7,989 $ 7,949 $ 27 $ 8,160 $ 8,119 $ 24 Long-term debt due within one year $ 88 $ 5 $ 77 $ 87 $ 5 $ 75 Accounts payable 143 143 — 292 292 — Accrued expenses 87 84 1 111 108 2 Mark-to-market derivative liabilities 8 8 — 24 24 — Unamortized energy contract liabilities 9 9 — 22 22 — Other current liabilities 13 13 — 25 25 — Total current liabilities 348 262 78 561 476 77 Long-term debt 166 79 81 212 81 120 Asset retirement obligations 1,865 1,865 — 1,763 1,763 — Pension obligation (a) 9 9 — 9 9 — Unamortized energy contract liabilities 45 45 — 51 51 — Other noncurrent liabilities 122 122 — 127 127 — Noncurrent liabilities 2,207 2,120 81 2,162 2,031 120 Total liabilities $ 2,555 $ 2,382 $ 159 $ 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 June 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 method 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. 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: June 30, 2015 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 260 $ 127 $ 387 Total liabilities (a) 29 61 90 Exelon's ownership interest in VIE (a) — 16 16 Other ownership interests in VIE (a) 231 51 282 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 19 19 Contract intangible asset 9 — 9 Debt and payment guarantees — 3 3 Net assets pledged for Zion Station decommissioning (b) 23 — 23 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 $264 million and $319 million as of June 30, 2015 and December 31, 2014 , respectively; offset by payables to ZionSolutions, LLC of $241 million and $292 million as of June 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	6 Months Ended
	Jun. 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. In connection with the Merger Agreement, Exelon entered into a subscription agreement under which it has purchased $162 million of a new class of nonvoting, nonconvertible and nontransferable preferred securities of PHI as of June 30, 2015 . The final investment of $18 million was paid on July 24, 2015 to reach the maximum aggregate investment of $180 million . 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. Exelon expects total cash required to fund the acquisition of common stock and preferred securities plus other related acquisition costs to total approximately $7.2 billion . On October 9, 2014, PHI and Exelon each received a request for additional information from the DOJ. The request had the effect of extending the DOJ review period until 30 days after PHI and Exelon each has certified that it had substantially complied with the request. On November 21, 2014, Exelon and PHI each certified that it had substantially complied with the request. Accordingly, 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. Exelon and PHI have cooperated with the DOJ regarding the proposed merger. 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 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 July 1, 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 responses 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. Exelon and PHI intend to vigorously oppose the motion. The merger still requires approval by the public service commission of the District of Columbia. Exelon and PHI expect the merger to be completed in the third quarter of 2015. Under the settlement terms and other conditions established in the merger approvals received to date and as proposed in the approval application in the District of Columbia, Exelon and PHI are required to expend in excess of $300 million , covering rate credits, funding for energy efficiency programs, sustainability funds, charitable contributions 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 2016. The actual nature, amount, timing and financial reporting treatment for these commitments may be materially impacted by terms and conditions set forth in any final District of Columbia approval order. Further, the settlements reached and commission orders received to date include a “most favored nation” provision which, generally speaking, requires allocation of merger benefits proportionately across all the jurisdictions. 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 June 30, 2015 , Exelon has incurred approximately $205 million of expense associated with the proposed merger. Of the total costs incurred, $89 million is primarily related to acquisition and integration costs and $116 million of 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 Merger Agreement also provides for termination rights for both parties. 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 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 certain expenses. Merger Financing Exelon intends to fund the all-cash transaction using a combination of debt, cash from asset sales primarily at Generation, and through issuance of equity (including mandatory convertible securities). On June 11, 2014, Exelon marketed an equity offering of 57.5 million shares of its common stock at a public offering price of $35 per share in connection with forward sales agreements and $1.2 billion of junior subordinated notes in the form of 23 million equity units. In addition, Exelon signed a 364-day $7.2 billion senior unsecured bridge credit facility to support the contemplated transaction and provide flexibility for timing of permanent financing. In June 2015, Exelon issued $4.2 billion of long-term debt which resulted in the termination of the remaining $3.2 billion bridge facility. Additionally, in July 2015, Exelon elected to settle the forward sales agreements resulting in net proceeds of approximately $1.87 billion . See Note 11 — Debt and Credit Agreements and Note 17 — Common Stock for more information. Asset Divestitures (Exelon and Generation) On January 21, 2015, Generation closed on the sale of the Quail Run generating facility. Including 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 ) which are expected to be used primarily to finance a portion of the acquisition and related costs and expenses, of PHI.

Regulatory Matters (Exelon, Gen

Regulatory Matters (Exelon, Generation, ComEd, PECO and BGE)	6 Months Ended
	Jun. 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 June 30, 2015 , and December 31, 2014 , ComEd had recorded a net regulatory asset associated with the distribution formula rate of $275 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 an 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 return on common equity 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 return on common equity 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. Participating utilities are also required to file an annual update on their AMI implementation progress. On June 11, 2014, the ICC approved ComEd's accelerated deployment plan which allows for the installation of more than 4 million smart meters throughout ComEd's service territory by 2018, three years in advance of the originally scheduled 2021 completion date. On April 1, 2015, ComEd filed an annual progress report on its AMI Implementation Plan with the ICC. To date, over 1.2 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. 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 would reflect a 4.4% increase on the basis of total Pennsylvania jurisdictional operating revenue. The requested rate of return on common equity is 10.95% . The new electric delivery rates would take effect no later than January 1, 2016. The results of the rate case are expected to be known in the fourth quarter of 2015. PECO cannot predict how much of the requested increase the PAPUC will ultimately approve. 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. In March 2015, PECO entered into contracts with PAPUC-approved bidders, including Generation, for its residential class and its small, medium, and large commercial classes which commenced in June 2015. 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 June 30, 2015 , PECO has spent $574 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 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. If approved, 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. 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 June 30, 2015 and December 31, 2014 , BGE recorded a regulatory asset of $160 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 cost estimates to be included in the 2015 surcharge. 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 June 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. The Court of Special Appeals (the Court) has issued a preliminary procedural schedule that sets oral argument in this matter for a date in the first two weeks of November 2015. On July 24, 2015, the residential consumer advocate's brief was filed. BGE's brief is due by August 24, 2015, and the residential consumer advocate's reply brief by September 15, 2015. 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. RG&E may terminate the RSSA contract upon providing 12-months' notice, which would require RG&E to make a specified termination payment to Ginna. The proposed RSSA contract extends through September 30, 2018. 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. While the FERC order supports Ginna's current agreement, it remains subject to FERC hearing and settlement procedures. These procedures may result in modifications to the agreement, however, Ginna is unable to predict the ultimate outcome of these proceedings. The effectiveness of the RSSA or any settlement among the parties at FERC remains contingent on approval by the NYPSC of RG&E’s full and timely recovery of rates associated with the costs incurred under the RSSA. 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 June 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. BGE recorded a net regulatory asset associated with the transmission formula rate of $1 million as of June 30, 2015 and December 31, 2014 each. 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 return on common equity 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 the FERC and 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 return on common equity 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 return on common equity (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 return on equity 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. 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. However, BGE is unable to estimate the most likely refund amount for either complaint at this time, and has therefore established a reserve, which is not material, representing the low end of a reasonably possible estimated range of loss. Additionally, management is unable to estimate the maximum exposure of a potential refund at this time, which may have a material impact on BGE's results of operations and cash flows. The estimated annual ongoing reduction in revenues if FERC approved the ROEs requested by the parties in their filings is approximately $11 million . If FERC were to order a reduction of BGE’s base ROE to 8.7% as sought in the first complaint (while retaining the 50 basis points of any incentives that were credited to the base return on equity for certain new transmission investment), the result of the first fifteen month refund window would be a refund to customers of approximately $13 million . If FERC were to order a reduction in BGE’s base ROE to 8.8% as sought in the second complaint (while retaining 50 basis points of any incentives that were credited to the base return on equity for certain new transmission investment) and the refund period extended for a full fifteen months, the result would be a refund to customers of approximately $14 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 2007, FERC issued an order concluding that PJM’s current rate design for existing facilities is just and reasonable and should not be changed. In the same order, FERC held that the costs of new facilities 500 kV and above should be socialized across the entire PJM footprint and that the costs of new facilities less than 500 kV should be allocated to the customers of the new facilities who caused the need for those facilities. A number of parties appealed to the U.S. Court of Appeals for the Seventh Circuit. In August 2009, the court issued its decision affirming the FERC’s order with regard to the existing facilities, but remanded to FERC the issue of the cost allocation associated with the new facilities 500 kV and above (Cost Allocation Issue) for further consideration by the FERC. On remand, FERC reaffirmed its earlier decision to socialize the costs of new facilities 500 kV and above. A number of parties filed appeals of these orders. In June 2014, the court again remanded the Cost Allocation Issue to FERC. On December 18, 2014, FERC issued an order setting an evidentiary hearing and settlement proceeding regarding the Cost Allocation Issue. The hearing only concerns new facilities approved by the PJM Board prior to February 1, 2013. As of June 30, 2015 , settlement discussions are continuing. Because a new cost allocation had been adopted for projects approved by the PJM Board on or after February 1, 2013, this latest remand only involves the cost allocation for facilities 500 kV and above approved prior to that date. ComEd anticipates that all impacts of any rate design changes effective after Decem

Investment in Constellation Ene

Investment in Constellation Energy Nuclear Group, LLC (Exelon and Generation)	6 Months Ended
	Jun. 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 six months ended June 30, 2015 , Generation had sales to EDF of $106 million and $288 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 Registrants 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 six months ended June 30, 2015 , Generation reduced by $4 million and $9 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 $109 million and $306 million and CENG’s net (loss) income, prior to any intercompany eliminations and any adjustments for noncontrolling interest, of $(4) million and $93 million during the three and six months ended June 30, 2015 , respectively.

Impairment of Long-lived Assets

Impairment of Long-lived Assets (Exelon and Generation)	6 Months Ended
	Jun. 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. 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 June 30, 2015 and December 31, 2014 , the components of the net investment in long-term leases were as follows: June 30, 2015 December 31, 2014 Estimated residual value of leased assets $ 639 $ 685 Less: unearned income 295 324 Net investment in long-term leases $ 344 $ 361

Implications of Potential Early

Implications of Potential Early Plant Retirements Implications of Potential Early Plant Retirements (Exelon, Generation)	6 Months Ended
	Jun. 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 the PJM capacity auction for the 2018/2019 delivery year, the effects of the new PJM “Capacity Performance” product, 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 outcome of the Ginna RSSA hearing and settlement procedures and the resulting contractual terms and conditions. Exelon and Generation have not made any decisions regarding potential plant closures at this time; however, various upcoming milestones could influence the timing of any such decisions, which could occur as soon as the third quarter of 2015. In September 2015, Generation has an obligation to inform PJM if any of its plants in the PJM region will not be participating in the May 2016 PJM capacity auction for delivery year beginning June 1, 2019. In December 2015, Generation must inform MISO if the Clinton plant will not be in operation during the next MISO resource adequacy planning year that begins June 1, 2016. As a result of a decision to early retire one or more 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: 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, among other items. 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 June 30, 2015 for significant assets and liabilities associated with the three nuclear plants currently deemed 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 $ 48 $ 55 $ 30 $ 133 Nuclear fuel inventory 205 137 66 408 Completed plant, net 800 465 85 1,350 Construction work in progress 24 24 23 71 Liability Balances Asset retirement obligation (450 ) (287 ) (611 ) (1,348 ) 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 was 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)	6 Months Ended
	Jun. 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 June 30, 2015 and December 31, 2014 : Exelon June 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 546 $ 3 $ 543 $ — $ 546 Long-term debt (including amounts due within one year) 25,446 1,043 24,011 1,349 26,403 Long-term debt to financing trusts 648 — — 663 663 SNF obligation 1,021 — 838 — 838 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 June 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 40 $ — $ 40 $ — $ 40 Long-term debt (including amounts due within one year) 9,001 — 7,995 1,349 9,344 SNF obligation 1,021 — 838 — 838 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 June 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 503 $ — $ 503 $ — $ 503 Long-term debt (including amounts due within one year) 6,099 — 6,640 — 6,640 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 June 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) $ 2,246 $ — $ 2,432 $ — $ 2,432 Long-term debt to financing trusts 184 — — 199 199 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 June 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 3 $ 3 $ — $ — $ 3 Long-term debt (including amounts due within one year) 1,905 — 2,086 — 2,086 Long-term debt to financing trusts 258 — — 258 258 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). 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 six months ended June 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 June 30, 2015 and December 31, 2014 : Generation Exelon As of June 30, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 134 $ — $ — $ 134 $ 5,486 $ — $ — $ 5,486 Nuclear decommissioning trust fund investments Cash equivalents 333 55 — 388 333 55 — 388 Equity Domestic 2,389 2,055 — 4,444 2,389 2,055 — 4,444 Foreign 696 — — 696 696 — — 696 Equity funds subtotal 3,085 2,055 — 5,140 3,085 2,055 — 5,140 Fixed income Corporate debt — 1,860 250 2,110 — 1,860 250 2,110 U.S. Treasury and agencies 1,165 — — 1,165 1,165 — — 1,165 Foreign governments — 83 — 83 — 83 — 83 State and municipal debt — 405 — 405 — 405 — 405 Other — 463 — 463 — — 463 — — — 463 Fixed income subtotal 1,165 2,811 250 4,226 1,165 2,811 250 4,226 Middle market lending — — 417 417 — — 417 417 Private Equity — — 100 100 — — 100 100 Real Estate — — 19 19 — — — — 19 19 Other — 329 — 329 — 329 — 329 Nuclear decommissioning trust fund investments subtotal (b) 4,583 5,250 786 10,619 4,583 5,250 786 10,619 Generation Exelon As of June 30, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Pledged assets for Zion Station decommissioning Cash equivalents — 17 — 17 — 17 — 17 Equities 5 1 — 6 5 1 — 6 Fixed income U.S. Treasury and agencies 7 2 — 9 7 2 — 9 Corporate debt — 62 — 62 — 62 — 62 State and municipal debt — 10 — 10 — 10 — 10 Other — 3 — 3 — — 3 — — 3 Fixed income subtotal 7 77 — 84 7 77 — 84 Middle market lending — — 156 156 — — 156 156 Pledged assets for Zion Station decommissioning subtotal (c) 12 95 156 263 12 95 156 263 Rabbi trust investments in mutual funds (d)(e) 17 — — 17 48 — — 48 Commodity derivative assets Economic hedges 1,080 3,352 2,334 6,766 1,080 3,352 2,334 6,766 Proprietary trading 117 239 38 394 117 239 38 394 Effect of netting and allocation of collateral (f) (1,364 ) (2,753 ) (872 ) (4,989 ) (1,364 ) (2,753 ) (872 ) (4,989 ) Commodity derivative assets subtotal (167 ) 838 1,500 2,171 (167 ) 838 1,500 2,171 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — 1 — 1 — 22 — 22 Economic hedges — 20 — 20 — 20 — 20 Proprietary trading 14 1 — 15 14 1 — 15 Effect of netting and allocation of collateral (8 ) (5 ) — (13 ) (8 ) (5 ) — (13 ) Interest rate and foreign currency derivative assets subtotal 6 17 — 23 6 38 — 44 Other investments — — 30 30 1 — 30 31 Total assets 4,585 6,200 2,472 13,257 9,969 6,221 2,472 18,662 Liabilities Commodity derivative liabilities Economic hedges (1,493 ) (3,129 ) (1,462 ) (6,084 ) (1,493 ) (3,129 ) (1,685 ) (6,307 ) Proprietary trading (111 ) (248 ) (43 ) (402 ) (111 ) (248 ) (43 ) (402 ) Effect of netting and allocation of collateral (f) 1,641 3,296 1,026 5,963 1,641 3,296 1,026 5,963 Commodity derivative liabilities subtotal 37 (81 ) (479 ) (523 ) 37 (81 ) (702 ) (746 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (14 ) — (14 ) — (14 ) — (14 ) Economic hedges — (4 ) — (4 ) — (4 ) — (4 ) Proprietary trading (14 ) — — (14 ) (14 ) — — (14 ) Effect of netting and allocation of collateral 14 5 — 19 14 5 — 19 Interest rate and foreign currency derivative liabilities subtotal — (13 ) — (13 ) — (13 ) — (13 ) Deferred compensation obligation — (26 ) — (26 ) — (88 ) — (88 ) Total liabilities 37 (120 ) (479 ) (562 ) 37 (182 ) (702 ) (847 ) Total net assets $ 4,622 $ 6,080 $ 1,993 $ 12,695 $ 10,006 $ 6,039 $ 1,770 $ 17,815 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 Generation Exelon As of December 31, 2014 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total 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 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 Generation Exelon As of December 31, 2014 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total 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 $(12) million and $(5) million at June 30, 2015 and December 31, 2014 , respectively. These items consist of 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 June 30, 2015 and December 31, 2014 , respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases. (d) Excludes $36 million and $35 million of cash surrender value of life insurance investment at June 30, 2015 and December 31, 2014 , respectively, at Exelon Consolidated. Excludes $13 million and $11 million and of cash surrender value of life insurance investment at June 30, 2015 and December 31, 2014 , respectively, at Generation. (e) The mutual funds held by the Rabbi trusts at Exelon include $47 million related to deferred compensation and $1 million related to Supplemental Executive Retirement Plan at June 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 $277 million , $543 million and $154 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of June 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 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 June 30, 2015 and December 31, 2014 : ComEd PECO BGE As of June 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 $ 5 $ — $ — $ 5 $ 5 $ — $ — $ 5 $ 46 $ — $ — $ 46 Rabbi trust investments in mutual funds (a) — — — — 8 — — 8 5 — — 5 Total assets 5 — — 5 13 — — 13 51 — — 51 Liabilities Deferred compensation obligation — (7 ) — (7 ) — (10 ) — (10 ) — (3 ) — (3 ) Mark-to-market derivative liabilities (b) — — (223 ) (223 ) — — — — — — — — Total liabilities — (7 ) (223 ) (230 ) — (10 ) — (10 ) — (3 ) — (3 ) Total net assets (liabilities) $ 5 $ (7 ) $ (223 ) $ (225 ) $ 13 $ (10 ) $ — $ 3 $ 51 $ (3 ) $ — $ 48 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 June 30, 2015 and December 31, 2014 , respectively. (b) The Level 3 balance includes the current and noncurrent liability of $ 20 million and $ 203 million at June 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 six months ended June 30, 2015 and 2014 : Generation ComEd Exelon Three Months Ended June 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 March 31, 2015 $ 715 $ 178 $ 1,066 $ 3 $ 1,962 $ (241 ) $ — $ 1,721 Total realized / unrealized gains (losses) Included in net income 2 — (7 ) (a) — (5 ) — — (5 ) Included in noncurrent payables to affiliates 7 — — — 7 — (7 ) — Included in payable for Zion Station decommissioning — (2 ) — — (2 ) — — (2 ) Included in regulatory assets — — — — — 18 7 25 Change in collateral — — (30 ) — (30 ) — — (30 ) Purchases, sales, issuances and settlements Purchases 99 6 16 27 148 — — 148 Sales — (26 ) (5 ) — (31 ) — — (31 ) Settlements (37 ) — — — (37 ) — — (37 ) Transfers into Level 3 — — 11 — 11 — — 11 Transfers out of Level 3 — — (30 ) — (30 ) — — (30 ) Balance as of June 30, 2015 $ 786 $ 156 $ 1,021 $ 30 $ 1,993 $ (223 ) $ — $ 1,770 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 June 30, 2015 $ 4 $ — $ 175 $ — $ 179 $ — $ — $ 179 Generation ComEd Exelon Six Months Ended June 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 — (39 ) (a) — (35 ) — — (35 ) Included in noncurrent payables to affiliates 15 — — — 15 — (15 ) — Included in payable for Zion Station decommissioning — 1 — — 1 — — 1 Included in regulatory assets — — — — — (16 ) 15 (1 ) Change in collateral — — (18 ) — (18 ) — — (18 ) Purchases, sales, issuances and settlements Purchases 146 11 57 27 241 — — 241 Sales (8 ) (40 ) (5 ) — (53 ) — — (53 ) Settlements (66 ) — — — (66 ) — — (66 ) Transfers into Level 3 4 — 11 — 15 — — 15 Transfers out of Level 3 — — (35 ) — (35 ) — — (35 ) Balance as of June 30, 2015 $ 786 $ 156 $ 1,021 $ 30 $ 1,993 $ (223 ) $ — $ 1,770 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 six months ended June 30, 2015 $ 5 $ — $ 355 $ — $ 360 $ — $ — $ 360 ______________ (a) Includes the reclassification of $(182) million and $(394) million of realized losses due to the settlement of derivative contracts for the three and six months ended June 30, 2015 , respectively. (b) Includes $14 million of increases in fair value and realized losses due to settlements of $4 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended June 30, 2015 . Includes $22 million of decreases in fair value and realized losses due to settlements of $6 million for the six months ended June 30, 2015 . Generation ComEd Exelon Three Months Ended June 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 March 31, 2014 $ 486 $ 137 $ 287 $ 10 $ 920 $ (168 ) $ — $ 752 Total realized / unrealized gains (losses) Included in net income 2 — (48 ) (a) — (46 ) — — (46 ) Included in noncurrent payables to affiliates 8 — — — 8 — (8 ) — Included in payable for Zion Station decommissioning — 4 — — 4 — — 4 Included in regulatory assets — — — — — 34 8 42 Change in collateral — — 34 — 34 — — 34 Purchases, sales, issuances and settlements Purchases 109 13 5 — 127 — — 127 Sales (1 ) (21 ) (4 ) — (26 ) — — (26 ) Settlements (12 ) — — — (12 ) — — (12 ) Transfers into Level 3 — — (4 ) — (4 ) — — (4 ) Transfers out of Level 3 — — (28 ) — (28 ) — — (28 ) Balance as of June 30, 2014 $ 592 $ 133 $ 242 $ 10 $ 977 $ (134 ) $ — $ 843 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 June 30, 2014 $ 2 $ — $ 19 $ — $ 21 $ — $ — $ 21 Generation ComEd Exelon Six Months Ended June 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 3 — (360 ) (a) — (357 ) — — $ (357 ) Included in noncurrent payables to affiliates 11 — — — 11 — (11 ) $ — Included in payable for Zion Station decommissioning — 4 — — 4 — — $ 4 Included in regulatory assets — — — — — 59 11 $ 70 Change in collateral — — 178 — 178 — — $ 178 Purchases, sales, issuances and settlements Purchases 249 42 15 2 308 — — $ 308 Sales (2 ) (25 ) (6 ) — (33 ) — — $ (33 ) Settlements (19 ) — — — (19 ) — — $ (19 ) Transfers into Level 3 — — (30 ) — (30 ) — — $ (30 ) Transfers out of Level 3 — — (20 ) (7 ) (27 ) — — $ (27 ) Balance as of June 30, 2014 $ 592 $ 133 $ 242 $ 10 $ 977 $ (134 ) $ — $ 843 The amount of total gains included in income attributed to the change in unrealized gains related to assets and liabilities held for the six months ended June 30, 2014 $ 2 $ — $ (427 ) $ — $ (425 ) $ — $ — $ (425 ) ______________ (a) Includes the reclassification of $ 67 million of realized losses due to the settlement of derivative contracts for the three and six months ended June 30, 2014. (b) Includes $34 million of increases in fair value and immaterial realized losses recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended June 30, 2014 . Includes $64 million of increases in fair value and realized gains due to settlements of $5 million for the six months ended June 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 six months ended June 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 June 30, 2015 $ (17 ) $ 10 $ 2 $ (17 ) $ 10 $ 2 Total gains (losses) included in net income for the six months ended June 30, 2015 (27 ) (12 ) 4 (27 ) (12 ) 4 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended June 30, 2015 171 4 4 171 4 4 Change in the unrealized gains (losses) relating to assets and liabilities held for the six months ended June 30, 2015 340 15 5 340 15 5 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 June 30, 2014 $ (62 ) $ 14 $ 2 $ (62 ) $ 14 $ 2 Total gains (losses) included in net income for the six months ended June 30, 2014 (330 ) (30 ) 3 (330 ) (30 ) 3 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended June 30, 2014 (10 ) 29 2 (10 ) 29 2 Change in the unrealized gains (losses) relating to assets and liabilities held for the six months ended June 30, 2014 (435 ) 8 2 (435 ) 8 2 ______________ (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 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. Inves

Derivative Financial Instrument

Derivative Financial Instruments (Exelon, Generation, ComEd, PECO and BGE)	6 Months Ended
	Jun. 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 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 June 30, 2015 , the proportion of expected generation hedged is for the major reportable segments was 98% - 101% , 77% - 80% , and 46% - 49% 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 1,657 GWhs and 3,465 GWhs for the three and six months ended June 30, 2015 , respectively, and 2,629 GWhs and 5,123 GWhs for the three and six months ended June 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 June 30, 2015 , Exelon had $800 million of notional amounts of fixed-to-floating hedges outstanding and Exelon and Generation had $754 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 $2 million decrease in Exelon Consolidated pre-tax income for the six months ended June 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 June 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 $ — $ 10 $ 10 $ (10 ) $ 10 $ — $ — $ — $ — $ 10 Mark-to-market derivative assets assets) 1 10 6 (3 ) 14 21 — — 21 35 Total mark-to-market derivative 1 20 16 (13 ) 24 21 — — 21 45 Mark-to-market derivative liabilities (current liabilities) (9 ) (5 ) (9 ) 14 (9 ) — — — — (9 ) Mark-to-market derivative liabilities (noncurrent liabilities) (5 ) — (5 ) 5 (5 ) — — — — (5 ) Total mark-to-market derivative (14 ) (5 ) (14 ) 19 (14 ) — — — — (14 ) Total mark-to-market derivative (liabilities) $ (13 ) $ 15 $ 2 $ 6 $ 10 $ 21 $ — $ — $ 21 $ 31 _____________ (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 June 30, Income Statement Location 2015 2014 2015 2014 Gain (Loss) on Swaps Gain (Loss) on Borrowings Generation Interest expense (a) $ — $ (3 ) $ — $ 2 Exelon Interest expense (11 ) 3 (12 ) (3 ) Six Months Ended June 30, Income Statement Location 2015 2014 2015 2014 Gain (Loss) on Swaps Gain (Loss) on Borrowings Generation Interest expense (a) $ (1 ) $ (8 ) $ — $ 1 Exelon Interest expense (2 ) 5 (4 ) (7 ) __________ (a) For the three and six months ended June 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 six months ended June 30, 2014 , the loss on Generation swaps included $4 million and $8 million realized in earnings, respectively, with an immaterial amount excluded from hedge effectiveness testing. At June 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 $ 20 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 six months ended June 30, 2015 , the impact on the results of operations as a result of the ineffectiveness from fair value hedges was a $4 million and $8 million gain, respectively. During the three and six months ended June 30, 2014 , the impact on the results of operations as a result of the ineffectiveness from fair value hedges was a $5 million and $8 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 $502 million as of June 30, 2015 and expire in 2019. The swap was designated as a cash flow hedge in the fourth quarter of 2014. At June 30, 2015 , the subsidiary had a $10 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 $201 million as of June 30, 2015 and expire in 2020. The swaps are designated as cash flow hedges. At June 30, 2015 , the subsidiary had a $ 2 million derivative liability related to the swaps. During the three and six months ended June 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 June 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. The balance in Accumulated OCI was frozen as of the date of de-designation and will amortize into Interest expense over the remaining term of the forecasted transaction. All future changes in fair value are reflected in Interest expense. At June 30, 2015 , the subsidiary had a $2 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 June 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. The balance in OCI was frozen as of the date of de-designation and will amortize into Interest expense over the remaining term of the forecasted transaction. All future changes in fair value are reflected in Interest expense. At June 30, 2015 , the subsidiary had an immaterial derivative asset 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 June 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 $ 146 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 June 30, 2015 and December 31, 2014 , $2 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 June 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) $ 4,398 $ 346 $ (3,349 ) $ 1,395 $ — $ 1,395 Mark-to-market derivative assets (noncurrent assets) 2,368 48 (1,640 ) 776 — 776 Total mark-to-market derivative assets 6,766 394 (4,989 ) 2,171 — 2,171 Mark-to-market derivative liabilities (current liabilities) (3,793 ) (347 ) 4,004 (136 ) (20 ) (156 ) Mark-to-market derivative liabilities (noncurrent liabilities) (2,291 ) (55 ) 1,959 (387 ) (203 ) (590 ) Total mark-to-market derivative liabilities (6,084 ) (402 ) 5,963 (523 ) (223 ) (746 ) Total mark-to-market derivative net assets (liabilities) $ 682 $ (8 ) $ 974 $ 1,648 $ (223 ) $ 1,425 _________ (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 $297 million and $144 million , respectively, and current and noncurrent liabilities are shown net of collateral of $358 million and $175 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $974 million at June 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 June 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 six months ended June 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 actual physical power sales, result in the ultimate recognition of net revenues at the contracted price. Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Three Months Ended June 30, 2015 Income Statement Location Total Cash Flow Hedges Total Cash Flow Hedges Accumulated OCI derivative gain at March 31, 2015 $ (23 ) $ (22 ) Effective portion of changes in fair value — 1 Reclassifications from accumulated OCI to net income Interest Expense 2 2 Accumulated OCI derivative gain at J

Debt and Credit Agreements (Exe

Debt and Credit Agreements (Exelon, Generation, ComEd, PECO and BGE)	6 Months Ended
	Jun. 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 June 30, 2015 and December 31, 2014 : Commercial Paper Borrowings June 30, 2015 December 31, 2014 Exelon Corporate $ — $ — Generation — — ComEd 503 304 PECO — — BGE — 120 Credit Facilities Exelon had bank lines of credit under committed credit facilities at June 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 on October 16, 2015. These facilities are solely utilized to issue letters of credit. As of June 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 June 30, 2015 , there were no borrowings under the Registrants’ credit facilities. 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 six months ended June 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) (b) 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) (b) 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) (b) 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 licensers Generation Senior Unsecured Notes (c) 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 (d) 2.50 - 2.70% 2019 - 2020 $ 435 General corporate purposes Generation Albany Green Energy Project Financing LIBOR + 1.25% November 17, 2017 $ 50 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) The 2025 notes, the 2035 notes and the 2045 notes must be redeemed upon the earlier of (i) December 31, 2015, if the PHI acquisition is not consummated on or prior to such date, or (ii) the date on which the Merger Agreement relating to the PHI acquisition is terminated. (c) 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. (d) The Tax Exempt Pollution Control Revenue Bonds have a mandatory put date that ranges from March 1, 2019 - September 1, 2020. 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. Albany Green Energy Project (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 six months ended June 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 3.35 % June 30, 2018 $ 38 Procurement of uranium Generation ExGen Renewables I Nonrecourse Debt LIBOR + 4.25% February 6, 2021 $ 300 General corporate purposes 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 Retirement and Redemptions of Current and Long-Term Debt During the six months ended June 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 Generation (a) Senior Unsecured Notes 4.55 % June 15, 2015 $ 550 Generation CEU Upstream Nonrecourse Debt LIBOR + 2.25% January 14, 2019 $ 2 Generation AVSR DOE Nonrecourse Debt 2.29%-3.56% January 5, 2037 $ 6 Generation Kennett Square Capital Lease 7.83 % September 20, 2020 $ 2 Generation Continental Wind Nonrecourse Debt 6.00 % February 28, 2033 $ 10 Generation ExGen Texas Power Nonrecourse Debt LIBOR + 4.75% September 8, 2021 $ 3 Generation ExGen Renewables I Nonrecourse Debt 4.49 % 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 July 6, 2015, Generation paid down $6 million of principal of its 2.29%-3.55% AVSR DOE Nonrecourse debt. During the six months ended June 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 $ 11 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 $ 1 Generation Clean Horizons Solar Nonrecourse Debt 2.56 % September 7, 2030 $ 1 Generation Sacramento Solar Nonrecourse Debt 2.56 % December 31, 2030 $ 1 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 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. The Long-term debt recorded for the contract payments is 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 of the Exelon 2014 Form 10-K.

Income Taxes (Exelon, Generatio

Income Taxes (Exelon, Generation, ComEd, PECO and BGE)	6 Months Ended
	Jun. 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 June 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 3.9 3.4 5.6 1.4 5.3 Qualified nuclear decommissioning trust fund income (1.0 ) (1.7 ) — — — Domestic production activities deduction (2.0 ) (3.4 ) — — — Health care reform legislation — — — — 0.1 Amortization of investment tax credit, net deferred taxes (0.6 ) (0.9 ) (0.3 ) (0.1 ) (0.2 ) Plant basis differences (1.0 ) — (0.1 ) (9.0 ) (0.5 ) Production tax credits and other credits (1.3 ) (2.2 ) — — — Noncontrolling interest (0.4 ) (0.6 ) — — — Other 1.4 2.0 0.5 0.5 0.8 Effective income tax rate 34.0 % 31.6 % 40.7 % 27.8 % 40.5 % For the Six Months Ended June 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 3.2 3.0 5.3 1.3 5.3 Qualified nuclear decommissioning trust fund income 0.6 0.9 — — — Domestic production activities deduction (2.1 ) (3.4 ) — — — Health care reform legislation — — — — 0.2 Amortization of investment tax credit, net deferred taxes (0.8 ) (1.1 ) (0.3 ) (0.1 ) (0.1 ) Plant basis differences (1.1 ) — (0.2 ) (7.5 ) (0.3 ) Production tax credits and other credits (1.6 ) (2.5 ) — — — Noncontrolling interest (0.6 ) (0.8 ) — — — Other 0.8 0.6 0.4 0.2 — Effective income tax rate 33.4 % 31.7 % 40.2 % 28.9 % 40.1 % For the Three Months Ended June 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 2.1 1.7 4.6 (0.5 ) 4.1 Qualified nuclear decommissioning trust fund income 4.1 6.0 — — — Domestic production activities deduction (2.0 ) (2.9 ) — — — Health care reform legislation — — 0.2 — 0.2 Amortization of investment tax credit, net deferred taxes (0.4 ) (0.5 ) (0.3 ) (0.1 ) (0.7 ) Plant basis differences (1.6 ) — (0.4 ) (13.2 ) 5.1 Production tax credits and other credits (0.8 ) (1.1 ) — — — Noncontrolling interest (2.0 ) (2.9 ) — — — Other (1.2 ) (0.4 ) 0.2 0.3 (1.3 ) Effective income tax rate 33.2 % 34.9 % 39.3 % 21.5 % 42.4 % For the Six Months Ended June 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 (0.6 ) (14.7 ) 5.0 0.4 5.0 Qualified nuclear decommissioning trust fund income 5.9 27.7 — — — Domestic production activities deduction (3.2 ) (14.8 ) — — — Health care reform legislation 0.1 — 0.2 — 0.2 Amortization of investment tax credit, net deferred taxes (1.2 ) (4.9 ) (0.3 ) (0.1 ) (0.3 ) Plant basis differences (3.0 ) — (0.5 ) (10.8 ) 0.4 Production tax credits and other credits (2.4 ) (11.1 ) — — — Noncontrolling interest (1.9 ) (8.8 ) — — — Other (3.1 ) (8.9 ) 0.2 0.3 0.1 Effective income tax rate 25.6 % (0.5 )% 39.6 % 24.8 % 40.4 % Accounting for Uncertainty in Income Taxes Exelon, Generation, ComEd, PECO, and BGE have $1,289 million , $745 million , $146 million , $0 million , and $120 million , of unrecognized tax benefits as of June 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 June 30, 2015 reflect a decrease at Exelon, Generation, and PECO primarily attributable to the disallowed AmerGen claims discussed below. The unrecognized tax benefits as of June 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 (Exelon and Generation) 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 its total unrecognized tax benefits by $ 661 million in the first quarter of 2015. This change in unrecognized tax benefits had no impact on Exelon’s or Generation’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 June 30, 2015, Exelon and ComEd have approximately $ 395 million and $ 145 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 June 30, 2015 , Exelon, Generation, and BGE have approximately $347 million , $ 227 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 $ 227 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. In July 2015, certain of these unrecognized state tax benefits were effectively settled resulting in a reduction of $ 45 million of tax expense and $ 21 million of accrued interest (after-tax) at Generation in the third quarter of 2015. 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 has been scheduled for August of 2015. Exelon was not required to remit any part of the asserted tax or penalty in order to litigate the issue. The litigation could take three to five years including appeals, if necessary. Decisions in the Tax Court are not controlled by the Federal Circuit’s decision in Consolidated Edison. In the event of a fully successful IRS challenge to Exelon’s like-kind exchange position, the potential tax and after-tax interest, exclusive of penalties, that could become currently payable as of June 30, 2015 may be as much as $810 million , of which approximately $310 million would be attributable to ComEd after consideration of Exelon’s agreement to hold ComEd harmless, and the balance at Exelon. Litigation could take several years such that the estimated cash and interest impacts would likely change by a material amount. 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 applied to satisfy taxes owed for any tax year. In the event of a fully successful IRS challenge to Exelon’s like-kind exchange position, the amount placed on deposit will be redesignated to reduce the amount of tax and after-tax interest discussed in the preceding paragraph.

Nuclear Decommissioning (Exelon

Nuclear Decommissioning (Exelon and Generation)	6 Months Ended
	Jun. 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 June 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 (b) 55 Accretion expense 189 Costs incurred to decommission retired plants (1 ) Nuclear decommissioning ARO at June 30, 2015 (a) $ 7,204 ___________ (a) Includes $7 million and $8 million as the current portion of the ARO at June 30, 2015 and December 31, 2014 respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets. (b) Represents a purchase accounting adjustment to the fair value of the CENG ARO liability as of April 1, 2014, the date of consolidation. See Note 6 — Investment in Constellation Energy Nuclear Group, LLC for additional information. Nuclear Decommissioning Trust Fund Investments At June 30, 2015 and December 31, 2014 , Exelon and Generation had NDT fund investments totaling $10,607 million and $10,537 million , respectively. The following table provides unrealized gains (losses) on NDT funds for the three and six months ended June 30, 2015 and 2014 : Exelon and Generation Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Net unrealized gains (losses) on decommissioning trust funds — Regulatory Agreement Units (a) $ (133 ) $ 172 $ (85 ) $ 234 Net unrealized gains (losses) on decommissioning trust funds — Non-Regulatory Agreement Units (b)(c) (96 ) 128 (56 ) 141 ___________ (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 $10 million of net unrealized gains related to the Zion Station pledged assets for the three months ended June 30, 2014 and $9 million and $20 million of net unrealized gains related to the Zion Station pledged assets for the six months ended June 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 $88 million , which is included within the nuclear decommissioning ARO at June 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 June 30, 2015 and December 31, 2014 : Exelon and Generation June 30, 2015 December 31, 2014 Carrying value of Zion Station pledged assets $ 264 $ 319 Payable to Zion Solutions (a) 241 292 Current portion of payable to Zion Solutions (b) 106 137 Cumulative withdrawals by Zion Solutions to pay decommissioning costs 731 666 ___________ (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. 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.

Retirement Benefits (Exelon, Ge

Retirement Benefits (Exelon, Generation, ComEd, PECO and BGE)	6 Months Ended
	Jun. 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 six months ended June 30, 2015 and 2014 . Pension Benefits Three Months Ended June 30, Other Postretirement Benefits Three Months Ended June 30, 2015 (a) 2014 (a) 2015 (a) 2014 (a) Service cost $ 81 $ 74 $ 29 $ 30 Interest cost 178 190 42 47 Expected return on assets (256 ) (251 ) (37 ) (38 ) Amortization of: Prior service cost (benefit) 4 4 (44 ) (30 ) Actuarial loss 142 104 21 12 Net periodic benefit cost $ 149 $ 121 $ 11 $ 21 Pension Benefits Six Months Ended June 30, Other Postretirement Benefits Six Months Ended June 30, 2015 (a) 2014 (a) 2015 (a) 2014 (a) Service cost $ 163 $ 143 $ 59 $ 62 Interest cost 355 373 83 103 Expected return on assets (513 ) (492 ) (75 ) (76 ) Amortization of: Prior service cost (benefit) 7 7 (88 ) (34 ) Actuarial loss 285 209 41 20 Net periodic benefit cost $ 297 $ 240 $ 20 $ 75 ______________ (a) For the three months ended June 30, 2015 , the cost for pension benefits and other postretirement benefits related to CENG were $3 million and $3 million , respectively. For the six months ended June 30, 2015 , the cost for pension benefits and other postretirement benefits related to CENG were $5 million and $6 million , respectively. For the period of April 1, 2014 to June 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. 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 six months ended June 30, 2015 and 2014 . Three Months Ended June 30, Six Months Ended June 30, Pension and Other Postretirement Benefit Costs 2015 2014 2015 2014 Generation (a) $ 68 $ 63 $ 133 $ 139 ComEd 51 40 103 96 PECO 10 9 19 21 BGE 17 17 33 33 BSC (b) 14 13 29 26 ______________ (a) For the three and six months ended June 30, 2015 , the costs related to CENG were $6 million and $11 million , respectively. For the period of April 1, 2014 to June 30, 2014, amounts include $5 million related to CENG. (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 six months ended June 30, 2015 and 2014 : Three Months Ended June 30, Six Months Ended June 30, Savings Plan Matching Contributions 2015 2014 2015 2014 Exelon (a) $ 38 $ 19 $ 60 $ 48 Generation (a) 20 10 33 24 ComEd 8 5 13 12 PECO 3 2 4 4 BGE 3 1 5 4 BSC (b) 4 1 5 4 _______________ (a) Includes $3 million and $4 million , respectively, related to CENG for the three and six months ended June 30, 2015 . For the period of April 1, 2014 to June 30, 2014, amounts include $1 million related to CENG. (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)	6 Months Ended
	Jun. 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 six months ended June 30, 2015 and 2014 , the Registrants recorded the following severance costs 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 June 30, 2015 $ 1 $ (1 ) $ — $ — $ — June 30, 2014 4 2 — — — Six Months Ended June 30, 2015 $ 21 $ 17 $ — $ — $ — June 30, 2014 6 4 — — — The severance liability balances associated with these ongoing severance benefits as of June 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)	6 Months Ended
	Jun. 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 six months ended June 30, 2015 and 2014 : Six Months Ended June 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 (10 ) — (29 ) (9 ) — (48 ) Amounts reclassified from AOCI (b) 19 — 87 — — 106 Net current-period OCI 9 — 58 (9 ) — 58 Ending balance $ (19 ) $ 3 $ (2,582 ) $ (28 ) $ — $ (2,626 ) Generation (a) Beginning balance $ (18 ) $ 1 $ — $ (19 ) $ — $ (36 ) OCI before reclassifications (6 ) 1 — (9 ) — (14 ) Amounts reclassified from AOCI (b) 3 — — — — 3 Net current-period OCI (3 ) 1 — (9 ) — (11 ) Ending balance $ (21 ) $ 2 $ — $ (28 ) $ — $ (47 ) 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. Six Months Ended June 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 (11 ) 1 246 (1 ) 11 246 Amounts reclassified from AOCI (b) (62 ) — 66 — (116 ) (112 ) Net current-period OCI (73 ) 1 312 (1 ) (105 ) 134 Ending balance $ 47 $ 3 $ (1,948 ) $ (11 ) $ 3 $ (1,906 ) Generation (a) Beginning balance $ 114 $ 2 $ — $ (10 ) $ 108 $ 214 OCI before reclassifications (8 ) (1 ) — (1 ) 11 1 Amounts reclassified from AOCI (b) (62 ) — — — (116 ) (178 ) Net current-period OCI (70 ) (1 ) — (1 ) (105 ) (177 ) Ending balance $ 44 $ 1 $ — $ (11 ) $ 3 $ 37 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 six months ended June 30, 2015 and 2014 . The following tables present amounts reclassified out of AOCI to Net income for Exelon and Generation during the three and six months ended June 30, 2015 and 2014 . Three Months Ended June 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 $ (2 ) $ (2 ) Interest expense (2 ) (2 ) Total before tax — — Tax benefit $ (2 ) $ (2 ) 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 27 — Tax benefit $ (44 ) $ — Net of tax Total Reclassifications for the period $ (46 ) $ (2 ) Net of Tax Six Months Ended June 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 (5 ) (5 ) Interest expense (29 ) (3 ) Total before tax 10 — Tax benefit $ (19 ) $ (3 ) Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 38 $ — Actuarial losses (b) (180 ) — (142 ) — Total before tax 55 — Tax benefit $ (87 ) $ — Net of tax Total Reclassifications for the period $ (106 ) $ (3 ) Net of Tax Three months ended June 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 $ 63 $ 63 Operating revenues 63 63 Total before tax (25 ) (25 ) Tax (expense) $ 38 $ 38 Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 12 $ — Actuarial losses (b) (61 ) — (49 ) — Total before tax 18 — Tax benefit $ (31 ) $ — Net of tax Equity investments Reversal of CENG equity method AOCI $ 193 $ 193 Gain on consolidation of CENG 193 193 Total before tax (77 ) (77 ) Tax benefit $ 116 $ 116 Net of tax Total reclassifications for the period $ 123 $ 154 Net of Tax Six Months Ended June 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 $ 102 $ 102 Operating revenues 102 102 Total before tax (40 ) (40 ) Tax (expense) $ 62 $ 62 Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 10 $ — Actuarial losses (b) (117 ) — (107 ) — Total before tax 41 — Tax benefit $ (66 ) $ — Net of tax Equity investments Reversal of CENG equity method AOCI $ 193 $ 193 Gain on consolidation of CENG 193 193 Total before tax (77 ) (77 ) Tax benefit $ 116 $ 116 Net of tax Total reclassifications for the period $ 112 $ 178 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 six months ended June 30, 2015 and 2014 : Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Exelon Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 8 $ 5 $ 15 $ 5 Actuarial loss reclassified to periodic cost (35 ) (23 ) (69 ) (46 ) Pension and non-pension postretirement benefit plans valuation adjustment — (166 ) 17 (159 ) Change in unrealized (gain) loss on cash flow hedges (2 ) 28 (6 ) 48 Change in unrealized income on equity investments — 77 — 70 Change in unrealized loss on marketable securities 1 — 1 — Total $ (28 ) $ (79 ) $ (42 ) $ (82 ) Generation Change in unrealized (gain) loss on cash flow hedges $ (1 ) $ 25 $ 1 $ 44 Change in unrealized income on equity investments — 77 — 70 Change in marketable securities — — 1 (2 ) Total $ (1 ) $ 102 $ 2 $ 112

Common Stock (Exelon, Generatio

Common Stock (Exelon, Generation, ComEd, PECO and BGE)	6 Months Ended
	Jun. 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. Exelon will use the net proceeds 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)	6 Months Ended
	Jun. 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 June 30, Six Months Ended June 30, 2015 2014 2015 2014 Net income attributable to common shareholders $ 638 $ 522 $ 1,331 $ 612 Average common shares outstanding — basic 863 860 862 860 Potentially dilutive effect of stock options, performance share awards and restricted stock 3 4 4 3 Average common shares outstanding — diluted 866 864 866 863 The number of stock options not included in the calculation of diluted common shares outstanding due to their antidilutive effect was approximately 13 million and 15 million for the three and six months ended June 30, 2015 , respectively, and 16 million for the three and six months ended June 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 1 million for the three and six months ended June 30, 2015 since issuance. 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 six months ended June 30, 2015 since issuance. 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 June 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)	6 Months Ended
	Jun. 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 Energy Commitments As of June 30, 2015 , Generation’s commitments relating to its purchases from unaffiliated utilities and others of energy, capacity, transmission rights and RECs, are as indicated in the following table: Net Capacity Purchases (a) REC Purchases (b) Transmission Rights Purchases (c) Total 2015 $ 218 $ 58 $ 7 $ 283 2016 280 288 15 583 2017 207 187 16 410 2018 96 72 17 185 2019 101 11 18 130 Thereafter 263 1 38 302 Total $ 1,165 $ 617 $ 111 $ 1,893 ____________________ (a) Net capacity purchases include PPAs and other capacity contracts including those that are accounted for as operating leases. Amounts presented in the commitments represent Generation’s expected payments under these arrangements at June 30, 2015 , net of fixed capacity payments expected to be received ("capacity offsets") by Generation under contracts to resell such acquired capacity to third parties under long-term capacity sale contracts. As of June 30, 2015 , capacity offsets were $ 75 million, $ 146 million, $ 149 million, $ 150 million, $ 151 million, and $ 604 million for years 2015, 2016, 2017, 2018, 2019, and thereafter, respectively. Expected payments include certain fixed capacity charges which may be reduced based on plant availability. (b) The table excludes renewable energy purchases that are contingent in nature. (c) Transmission rights purchases include estimated commitments for additional transmission rights that will be required to fulfill firm sales contracts. ComEd’s, PECO’s and BGE’s electric supply procurement, curtailment services, REC and AEC purchase commitments, as applicable, as of June 30, 2015 are as follows: Expiration within Total 2015 2016 2017 2018 2019 2020 and beyond ComEd Electric supply procurement (a) $ 697 $ 251 $ 262 $ 163 $ 21 $ — $ — Renewable energy and RECs (b) 1,481 38 76 77 78 79 1,133 PECO Electric supply procurement (c) 671 368 270 33 — — — AECs (d) 13 2 2 2 2 2 3 BGE Electric supply procurement (e) 1,389 462 675 252 — — — Curtailment services (f) 95 20 34 29 12 — — ___________________ (a) ComEd entered into various contracts for the procurement of electricity that started to expire in 2012, and will continue to expire through 2018. ComEd is permitted to recover its electric supply procurement costs from retail customers with no mark-up. As of June 30, 2015 , ComEd has completed the ICC-approved procurement process for a portion of its energy requirements through the periods ending May 31, 2015, 2016 and 2017. (b) Primarily related to ComEd 20-year contracts for renewable energy and RECs that began in June 2012. ComEd is permitted to recover its renewable energy and REC costs from retail customers with no mark-up. The commitments represent the maximum settlements with suppliers for renewable energy and RECs under the existing contract terms. (c) PECO entered into various contracts for the procurement of electric supply to serve its default service customers that expire between 2015 and 2017. PECO is permitted to recover its electric supply procurement costs from default service customers with no mark-up in accordance with its PAPUC-approved DSP Programs. See Note 5 — Regulatory Matters for additional information. (d) PECO is subject to requirements related to the use of alternative energy resources established by the AEPS Act. See Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K for additional information. (e) BGE entered into various contracts for the procurement of electricity that expire between 2015 through 2017. The cost of power under these contracts is recoverable under MDPSC approved fuel clauses. See Note 3 — Regulatory Matters of the Exelon 2014 10-K for additional information. (f) BGE has entered into various contracts with curtailment services providers related to transactions in PJM’s capacity market. See Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K for additional information. Fuel Purchase Obligations In addition to the energy commitments described above, Generation has commitments to purchase fuel supplies for nuclear and fossil generation. Since the second quarter of 2014, 100% of CENG’s nuclear fuel commitments are disclosed within the Generation line below, since CENG is now fully consolidated by Generation. PECO and BGE have commitments to purchase natural gas related to transportation, storage capacity and services to serve customers in their gas distribution service territory. As of June 30, 2015 , these net commitments were as follows: Expiration within Total 2015 2016 2017 2018 2019 2020 and beyond Generation $ 8,884 $ 726 $ 1,129 $ 1,078 $ 969 $ 880 $ 4,102 PECO 375 65 107 66 46 20 71 BGE 622 52 103 92 69 61 245 Other Purchase Obligations The Registrants’ other purchase obligations as of June 30, 2015 , which primarily represent commitments for services, materials and information technology, are as follows: Expiration within Total 2015 2016 2017 2018 2019 2020 and beyond Exelon $ 1,422 $ 342 $ 421 $ 220 $ 77 $ 80 $ 282 Generation (a) 339 79 95 46 33 24 62 ComEd (b) 356 153 166 8 7 7 15 PECO (b) 21 5 5 2 2 2 5 BGE (b) 302 75 116 111 — — — _____________________ (a) Purchase obligations do not include commitments related to construction contracts. See Construction Commitments section below for additional information. (b) Purchase obligations include commitments related to smart meter installation. See Note 5 — Regulatory Matters for additional information. Construction Commitments Generation’s ongoing investments in renewables development and new natural gas construction illustrates Generation’s growth strategy to provide for diversification opportunities while leveraging its expertise and strengths. Generation completed the construction of the Perryman 6 expansion in Perryman, Maryland, which began commercial operation in June 2015. As of June 30, 2015 , Generation has no further material remaining construction commitments for the project. This project will satisfy a portion of Exelon's commitment to Maryland. See Note 4 — Mergers, Acquisitions, and Dispositions of the Exelon 2014 Form 10-K for additional information on commitments to develop or assist in development of new generation in Maryland resulting from the Constellation merger. Since the third quarter of 2014, Generation executed contracts associated with the construction of new combined-cycle gas turbine units in Texas. The remaining commitment is approximately $ 736 million under these contracts and achievement of commercial operations is expected in 2017. Since the fourth quarter of 2014, Generation executed contracts associated with the construction of the 30 MW Fair Wind project in western Maryland. The remaining commitment is approximately $ 16 million under these contracts and achievement of commercial operations is expected in 2015. This project will satisfy a portion of Exelon’s 125 MW Tier I land-based renewables commitment made to Maryland. See Note 4 — Mergers, Acquisitions, and Dispositions of the Exelon 2014 Form 10-K for additional information on commitments to develop or assist in development of new generation in Maryland resulting from the Constellation merger. Since the fourth quarter of 2014, Generation executed contracts associated with the construction of the 78 MW Sendero Wind project in southern Texas. The remaining commitment is approximately $ 49 million under these contracts and achievement of commercial operations is expected in 2015. During the second quarter of 2015, Generation executed contracts associated with the construction of a 50 MW biomass facility in Georgia. The remaining commitment under these contracts is approximately $ 170 million and achievement of commercial operations is expected in 2017. Refer to Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K for information on investment programs associated with regulatory mandates, such as ComEd’s Infrastructure Investment Plan under EIMA, PECO’s Smart Meter Procurement and Installation Plan and BGE’s comprehensive smart grid initiative. 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 $ 314 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. 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 June 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 $ 77 2016 254 2017 23 2018 7 2019 2 Total $ 363 Contingencies Commercial Commitments The Registrants’ commercial commitments as of June 30, 2015 , representing commitments potentially triggered by future events were as follows: Exelon Generation ComEd PECO BGE Letters of credit (non-debt) (a) $ 1,568 $ 1,502 $ 18 $ 22 $ 1 Guarantees 5,824 (b) 3,115 (c) 203 (d) 188 (e) 263 (f) Nuclear insurance premiums (g) 3,057 3,057 — — — Underwriters discount (h) 60 — — — — Total commercial commitments $ 10,509 $ 7,674 $ 221 $ 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 $674 million at June 30, 2015 , which represents the total amount Exelon could be required to fund based on June 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 $460 million at June 30, 2015 , which represents the total amount Generation could be required to fund based on June 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. (h) Represents the underwriters discount for Exelon’s forward equity transaction. See Note 17 — Common Stock for further details of the equity securities offering. 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 June 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 June 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 2019. • 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. BGE has not established a regulatory asset for the costs associated with the gas purification site as of June 30, 2015 . As of June 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: June 30, 2015 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 337 $ 267 Generation 63 — ComEd 227 224 PECO 44 41 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 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 $ 13 million at both June 30, 2015 and 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 June 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. In June 2012, the U.S. EPA requested that the PRPs perform additional analysis and groundwater sampling as part of the supplemental feasibility study, and subsequently requested additional analysis sampling and modeling that will be conducted throughout 2015. 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 current estimated cost of the landfill cover remediation for the site is approximately $60 million , which will be allocated among all PRPs. 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 2015 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. On February 28, 2012, and April 10, 2012, two lawsuits were filed in the U.S. District Court

Supplemental Financial Informat

Supplemental Financial Information (Exelon, Generation, ComEd, PECO and BGE)	6 Months Ended
	Jun. 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 six months ended June 30, 2015 and 2014 : Three Months Ended June 30, 2015 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 93 $ 93 $ — $ — $ — Non-regulatory agreement units 74 74 — — — Net unrealized losses on decommissioning trust funds Regulatory agreement units (133 ) (133 ) — — — Non-regulatory agreement units (96 ) (96 ) — — — Regulatory offset to decommissioning trust fund-related activities (b) 28 28 — — — Total decommissioning-related activities (34 ) (34 ) — — — Investment income (expense) 1 — — (1 ) 1 (c) Long-term lease income 4 — — — — AFUDC — Equity 5 — 1 1 3 Other 7 3 4 1 — Other, net $ (17 ) $ (31 ) $ 5 $ 1 $ 4 Six Months Ended June 30, 2015 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 164 $ 164 $ — $ — $ — Non-regulatory agreement units 104 104 — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units (85 ) (85 ) — — — Non-regulatory agreement units (56 ) (56 ) — — — Net unrealized gains on pledged assets Zion Station decommissioning 9 9 — — — Regulatory offset to decommissioning trust fund-related activities (b) (78 ) (78 ) — — — Total decommissioning-related activities 58 58 — — — Investment income (expense) 4 1 — (1 ) 2 (c) Long-term lease income 8 — — — — Interest income related to uncertain income tax positions — 1 — — — AFUDC — Equity 11 — 1 3 7 Terminated interest rate swaps (d) (26 ) — — — — Other 9 2 8 1 (1 ) Other, net $ 64 $ 62 $ 9 $ 3 $ 8 Three Months Ended June 30, 2014 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 68 $ 68 $ — $ — $ — Non-regulatory agreement units 38 38 — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 172 172 — — — Non-regulatory agreement units 128 128 — — — Net unrealized losses on pledged assets Zion Station decommissioning 10 10 — — — Regulatory offset to decommissioning trust fund-related activities (b) (204 ) (204 ) — — — Total decommissioning-related activities 212 212 — — — Investment income (expense) 7 7 — (1 ) 2 (c) Long-term lease income 10 — — — — Interest income related to uncertain income tax positions (2 ) 3 AFUDC — Equity 4 — — 1 3 Other (1 ) (6 ) 5 1 — Other, net $ 230 $ 216 $ 5 $ 1 $ 5 Six Months Ended June 30, 2014 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 111 $ 111 $ — $ — $ — Non-regulatory agreement units 63 63 — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 234 234 — — — Non-regulatory agreement units 141 141 — — — Net unrealized losses on pledged assets Zion Station decommissioning 20 20 — — — Regulatory offset to decommissioning trust fund-related activities (b) (299 ) (299 ) — — — Total decommissioning-related activities 270 270 — — — Investment income (expense) 8 8 — (1 ) 4 (c) Long-term lease income 17 — — — — Interest income related to uncertain income tax positions 7 17 — — — AFUDC — Equity 12 — 3 3 6 Other 16 5 7 1 (1 ) Other, net $ 330 $ 300 $ 10 $ 3 $ 9 ________ (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 six months ended June 30, 2015 and 2014 : Six Months Ended June 30, 2015 Exelon Generation ComEd PECO BGE Depreciation, amortization, accretion and depletion Property, plant and equipment $ 1,087 $ 485 $ 312 $ 119 $ 143 Regulatory assets 101 — 40 12 49 Amortization of intangible assets, net 24 24 — — — Amortization of energy contract assets and liabilities (a) — 1 — — — Nuclear fuel (b) 552 552 — — — ARO accretion (c) 193 193 — — — Total depreciation, amortization, accretion and depletion $ 1,957 $ 1,255 $ 352 $ 131 $ 192 Six Months Ended June 30, 2014 Exelon Generation ComEd PECO BGE Depreciation, amortization, accretion and depletion Property, plant and equipment $ 1,015 $ 444 $ 290 $ 112 $ 142 Regulatory assets 117 — 57 5 55 Amortization of intangible assets, net 22 22 — — — Amortization of energy contract assets and liabilities (a) 113 118 — — — Nuclear fuel (b) 499 499 — — — ARO accretion (c) 159 159 — — — Total depreciation, amortization, accretion and depletion $ 1,925 $ 1,242 $ 347 $ 117 $ 197 _________ (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. Six Months Ended June 30, 2015 Exelon Generation ComEd PECO BGE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 317 $ 133 $ 103 $ 19 $ 33 Loss from equity method investments 2 3 — — — Provision for uncollectible accounts 80 11 35 24 11 Stock-based compensation costs 79 — — — — Other decommissioning-related activity (a) (50 ) (50 ) — — — Energy-related options (b) 27 27 — — — Amortization of regulatory asset related to debt costs — — — — — Amortization of rate stabilization deferral 40 — — — 40 Amortization of debt fair value adjustment (37 ) (6 ) — — — Discrete impacts of EIMA (c) 77 — 77 — — Amortization of debt costs 35 8 2 1 1 Lower of cost or market inventory adjustment 13 13 — — — Other (4 ) (5 ) 5 1 (9 ) Total other non-cash operating activities $ 579 $ 134 $ 222 $ 45 $ 76 Changes in other assets and liabilities: Under/over-recovered energy and transmission costs $ 45 $ — $ 10 $ 27 $ 8 Other regulatory assets and liabilities 47 — 26 (13 ) (18 ) Cash deposits (d) 242 242 — — — Other current assets (53 ) (39 ) 3 (74 ) (e) 60 Other noncurrent assets and liabilities (67 ) — (14 ) — 1 Total changes in other assets and liabilities $ 214 $ 203 $ 25 $ (60 ) $ 51 Non-cash investing and financing activities: Indemnification of like-kind exchange position (f) $ — $ — $ 3 $ — $ — Long-term software licensing agreement (g) 95 — — — — Total non-cash investing and financing activities: $ 95 $ — $ 3 $ — $ — Six Months Ended June 30, 2014 Exelon Generation ComEd PECO BGE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 315 $ 139 $ 96 $ 21 $ 33 Equity method investments 20 20 — — — Provision for uncollectible accounts 59 8 (8 ) 28 30 Stock-based compensation costs 68 — — — — Other decommissioning-related activity (a) (85 ) (85 ) — — — Energy-related options (b) 63 63 — — — Amortization of rate stabilization deferral 33 — — — 33 Amortization of debt fair value adjustment (26 ) (12 ) — — — Discrete impacts from EIMA (c) 9 — 9 — — Amortization of debt costs 19 6 (3 ) 1 1 Other (2 ) — 5 — (8 ) Total other non-cash operating activities $ 473 $ 139 $ 99 $ 50 $ 89 Changes in other assets and liabilities: Under/over-recovered energy and transmission costs $ 60 $ — $ 61 $ (6 ) $ 8 Other regulatory assets and liabilities (25 ) — (30 ) (13 ) (49 ) Other current assets (157 ) 13 (5 ) (89 ) (e) 51 Other noncurrent assets and liabilities (158 ) (69 ) 22 (6 ) (2 ) Total changes in other assets and liabilities $ (280 ) $ (56 ) $ 48 $ (114 ) $ 8 Non-cash investing and financing activities: Fair value of net assets recorded upon CENG consolidation $ 3,400 $ 3,400 $ — $ — $ — Issuance of equity units 131 — — — — Uranium procurement 38 38 — — — Indemnification of like-kind exchange position (f) — — 2 — — Total non-cash investing and financing activities $ 3,569 $ 3,438 $ 2 $ — $ — ____________ (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 recalled from ISOs/RTOs and replaced with letters of credit. (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. DOE Smart Grid Investment Grant (Exelon and PECO). For the six months ended June 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 $3 million related to PECO’s DOE SGIG programs. For the six months ended June 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 June 30, 2015 and December 31, 2014 . June 30, 2015 Exelon Generation ComEd PECO BGE Property, plant and equipment: Accumulated depreciation and amortization $ 15,553 (a) $ 8,146 (a) $ 3,571 $ 3,028 $ 2,928 Accounts receivable: Allowance for uncollectible accounts 323 (c) 67 95 101 (c) 60 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 $2,804 million . (b) Includes accumulated amortization of nuclear fuel in the reactor core of $2,673 million . (c) Includes an allowance for uncollectible accounts of $9 million and $7 million at June 30, 2015 and December 31, 2014 , respectively, related to PECO's current installment plan receivables described below. 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 $16 million and $15 million as of June 30, 2015 and December 31, 2014 , respectively. 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 June 30, 2015 of $18 million consists of $1 million , $4 million and $13 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 June 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)	6 Months Ended
	Jun. 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, 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; 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 foundation of Generation’s six reportable segments is based on the geographic location of its assets, and is largely representative of the footprints of an ISO / RTO and/or NERC region. Descriptions of each of Generation’s six reportable segments are as follows: • Mid-Atlantic represents operations in the eastern half of PJM, which includes Pennsylvania, New Jersey, Maryland, Virginia, West Virginia, Delaware, the District of Columbia and parts of North Carolina. • Midwest represents operations in the western half of PJM, which includes portions of Illinois, 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. Generation believes that revenue net of purchased power and fuel expense is a useful measurement of operational performance. Revenue net of purchased power and fuel expense (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. Generation's other business activities, including retail and wholesale gas, investments in gas and oil exploration and production activities, proprietary trading, compressed natural gas fueling stations, energy efficiency and cogeneration projects, sales of electric and gas appliances, servicing of heating, air conditioning, plumbing, electrical, indoor quality systems and home improvements, and investments in energy-related proprietary technology are not allocated to regions. Further, Generation’s unrealized mark-to-market impact of economic hedging activities, amortization of certain intangible assets relating to commodity contracts recorded at fair value from mergers and acquisitions and other miscellaneous revenues are also not allocated to a region. 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 June 30, 2015 and 2014 Generation (a) ComEd PECO BGE Other (b) Intersegment Eliminations Exelon Total revenues (c) : 2015 $ 4,232 $ 1,148 $ 661 $ 628 $ 340 $ (495 ) $ 6,514 2014 3,789 1,128 656 653 329 (531 ) 6,024 Intersegment revenues (d) : 2015 $ 152 $ 1 $ — $ 1 $ 340 $ (493 ) $ 1 2014 201 — — 2 328 (531 ) — Net income (loss): 2015 $ 390 $ 99 $ 70 $ 47 $ 28 $ (1 ) $ 633 2014 372 111 84 19 (29 ) — 557 Total assets: June 30, 2015 $ 45,125 $ 25,961 $ 10,126 $ 8,017 $ 14,526 $ (11,542 ) $ 92,213 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 June 30, 2015 include revenue from sales to PECO of $49 million and sales to BGE of $97 million in the Mid-Atlantic region, and sales to ComEd of $6 million in the Midwest. For the three months ended June 30, 2014 , intersegment revenues for Generation include revenue from sales to PECO of $49 million and sales to BGE of $87 million in the Mid-Atlantic region, and sales to ComEd of $65 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 June 30, 2015 and 2014 , utility taxes of $24 million and $21 million , respectively, are included in revenues and expenses for Generation. For the three months ended June 30, 2015 and 2014 , utility taxes of $55 million and $56 million , respectively, are included in revenues and expenses for ComEd. For the three months ended June 30, 2015 and 2014 , utility taxes of $32 million and $30 million , respectively, are included in revenues and expenses for PECO. For the three months ended June 30, 2015 and 2014 , utility taxes of $21 million and $19 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 June 30, 2015 Three Months Ended June 30, 2014 Revenues from External Customers (a) Intersegment Revenues Total Revenues Revenues from External Customers (a) Intersegment Revenues Total Revenues Mid-Atlantic $ 1,336 $ 10 $ 1,346 $ 1,272 $ 5 $ 1,277 Midwest 1,205 1 1,206 981 — 981 New England 366 1 367 211 1 212 New York 222 (4 ) 218 194 — 194 ERCOT 194 (2 ) 192 198 (1 ) 197 Other Power Regions (b) 294 (5 ) 289 314 (6 ) 308 Total Revenues for Reportable Segments 3,617 1 3,618 3,170 (1 ) 3,169 Other (c) 615 (1 ) 614 619 1 620 Total Generation Consolidated Operating Revenues $ 4,232 $ — $ 4,232 $ 3,789 $ — $ 3,789 __________ (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 $17 million decrease to revenues and an $88 million decrease to revenues for the amortization of intangible assets related to commodity contracts for the three months ended June 30, 2015 and 2014 , respectively, unrealized mark-to-market gains of $25 million and losses of $83 million for the three months ended June 30, 2015 and 2014 , respectively, and the elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Three Months Ended June 30, 2015 Three Months Ended June 30, 2014 RNF (a) Intersegment RNF Total RNF RNF (a) Intersegment RNF Total RNF Mid-Atlantic $ 875 $ 14 $ 889 $ 906 $ 14 $ 920 Midwest 745 (2 ) 743 604 1 605 New England 94 (6 ) 88 88 (24 ) 64 New York 139 5 144 142 6 148 ERCOT 91 (21 ) 70 117 (58 ) 59 Other Power Regions (b) 134 (72 ) 62 157 (82 ) 75 Total Revenues net of purchased power and fuel for Reportable Segments 2,078 (82 ) 1,996 2,014 (143 ) 1,871 Other (c) 305 82 387 (60 ) 143 83 Total Generation Revenues net of purchased power and fuel expense $ 2,383 $ — $ 2,383 $ 1,954 $ — $ 1,954 __________ (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 $14 million decrease to RNF and a $50 million decrease to RNF for the amortization of intangible assets related to commodity contracts for the three months ended June 30, 2015 and 2014 , respectively, unrealized mark-to-market gains of $235 million and losses of $14 million for the three months ended June 30, 2015 and 2014 , respectively, and the elimination of intersegment revenues. Six Months Ended June 30, 2015 and 2014 Generation (a) ComEd PECO BGE Other (b) Intersegment Eliminations Exelon Total revenues (c) : 2015 $ 10,074 $ 2,333 $ 1,646 $ 1,664 $ 657 $ (1,029 ) $ 15,345 2014 8,179 2,262 1,649 1,707 619 (1,155 ) 13,261 Intersegment revenues (d) : 2015 $ 362 $ 2 $ 1 $ 8 $ 656 $ (1,026 ) $ 3 2014 517 1 1 18 618 (1,155 ) — Net income (loss): 2015 $ 875 $ 189 $ 209 $ 157 $ (55 ) $ (3 ) $ 1,372 2014 188 209 173 106 (25 ) — 651 __________ (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 six months ended June 30, 2015 include revenue from sales to PECO of $ 112 million and sales to BGE of $ 235 million in the Mid-Atlantic region, and sales to ComEd of $ 15 million in the Midwest. For the six months ended June 30, 2014 , intersegment revenues for Generation include revenue from sales to PECO of $ 137 million and sales to BGE of $ 207 million in the Mid-Atlantic region, and sales to ComEd of $ 173 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 six months ended June 30, 2015 and 2014 , utility taxes of $ 51 million and $ 45 million , respectively, are included in revenues and expenses for Generation. For the six months ended June 30, 2015 and 2014 , utility taxes of $ 117 million and $ 119 million , respectively, are included in revenues and expenses for ComEd. For the six months ended June 30, 2015 and 2014 , utility taxes of $ 67 million and $ 65 million , respectively, are included in revenues and expenses for PECO. For the six months ended June 30, 2015 and 2014 , utility taxes of $ 44 million and $ 43 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: Six Months Ended June 30, 2015 Six Months Ended June 30, 2014 Revenues (b) Intersegment Total Revenues (b) Intersegment Total Mid-Atlantic (a) $ 2,853 $ 6 $ 2,859 $ 2,713 $ (18 ) $ 2,695 Midwest 2,480 2 2,482 2,239 12 2,251 New England 1,224 2 1,226 756 5 761 New York (a) 532 (4 ) 528 384 (3 ) 381 ERCOT 376 (4 ) 372 441 (1 ) 440 Other Power Regions (c) 506 (3 ) 503 648 1 649 Total Revenues for Reportable Segments 7,971 (1 ) 7,970 7,181 (4 ) 7,177 Other (d) 2,103 1 2,104 998 4 1,002 Total Generation Consolidated Operating Revenues $ 10,074 $ — $ 10,074 $ 8,179 $ — $ 8,179 __________ (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 $22 million increase to revenues and a $180 million decrease to revenues for the amortization of intangible assets related to commodity contracts for the six months ended June 30, 2015 and 2014 , respectively, unrealized mark-to-market gains of $179 million and losses of $843 million for the six months ended June 30, 2015 and 2014 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Six Months Ended June 30, 2015 Six Months Ended June 30, 2014 RNF from External Customers (b) Intersegment RNF Total RNF RNF from External Customers (b) Intersegment RNF Total RNF Mid-Atlantic (a) $ 1,659 $ 12 $ 1,671 $ 1,690 $ (75 ) $ 1,615 Midwest 1,446 (3 ) 1,443 1,134 27 1,161 New England 271 (25 ) 246 242 (42 ) 200 New York (a) 313 19 332 113 14 127 ERCOT 179 (54 ) 125 272 (130 ) 142 Other Power Regions (c) 233 (125 ) 108 307 (127 ) 180 Total Revenues net of purchased power and fuel expense for Reportable Segments 4,101 — (176 ) 3,925 3,758 (333 ) 3,425 Other (d) 691 176 867 (770 ) 333 (437 ) Total Generation Revenues net of purchased power and fuel expense $ 4,792 — $ — $ 4,792 $ 2,988 $ — $ 2,988 __________ (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 $24 million increase to RNF and a $92 million decrease to RNF for the amortization of intangible assets related to commodity contracts for the six months ended June 30, 2015 and 2014 , respectively, unrealized mark-to-market gains of $397 million and losses of $744 million for the six months ended June 30, 2015 and 2014 , respectively, and the elimination of intersegment revenue net of purchased power and fuel expense.

Accounting Policy (Policies)

Accounting Policy (Policies)	6 Months Ended
	Jun. 30, 2015
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Description of New Accounting Pronouncements Not yet Adopted [Text Block]	New Accounting Pronouncements (Exelon, Generation, ComEd, PECO and BGE) The following recently issued accounting standards are not yet required to be reflected in the combined financial statements of the Registrants. 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 are currently assessing the impact this guidance may have 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 entity’s 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. 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 within annual reporting periods 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. As currently issued, the guidance is effective for the Registrants for the first interim period within annual reporting periods beginning on or after December 15, 2016; and early adoption would not be permitted. However, in July 2015, the FASB approved 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. As of July 29, 2015, the amendment to defer the effective date and provide an option to early adopt had not been issued.
Policy Text Block [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 six months ended June 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 June 30, 2015 , Generation has outstanding commitments to invest in middle market lending, corporate debt securities, private equity investments, and real estate investments of approximately $312 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 $3.33 and $0.34 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.

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	6 Months Ended
	Jun. 30, 2015
Variable Interest Entity [Abstract]
Schedule of Variable Interest Entities	June 30, 2015 December 31, 2014 Exelon Generation BGE Exelon Generation BGE Cash and cash equivalents $ 240 $ 240 $ — $ 392 $ 392 $ — Restricted cash 145 121 24 117 96 21 Accounts receivable, net Customer 179 179 — 297 297 — Other 29 29 — 57 57 — Mark-to-market derivatives assets 96 96 — 171 171 — Inventory Materials and supplies 178 178 — 172 172 — Other current assets 32 25 — 33 26 — Total current assets 899 868 24 1,239 1,211 21 Property, plant and equipment, net 4,811 4,811 — 4,638 4,638 — Nuclear decommissioning trust funds 2,096 2,096 — 2,097 2,097 — Goodwill 47 47 — 47 47 — Mark-to-market derivatives assets 45 45 — 44 44 — Other noncurrent assets 91 82 3 95 82 3 Total noncurrent assets 7,090 7,081 3 6,921 6,908 3 Total assets $ 7,989 $ 7,949 $ 27 $ 8,160 $ 8,119 $ 24 Long-term debt due within one year $ 88 $ 5 $ 77 $ 87 $ 5 $ 75 Accounts payable 143 143 — 292 292 — Accrued expenses 87 84 1 111 108 2 Mark-to-market derivative liabilities 8 8 — 24 24 — Unamortized energy contract liabilities 9 9 — 22 22 — Other current liabilities 13 13 — 25 25 — Total current liabilities 348 262 78 561 476 77 Long-term debt 166 79 81 212 81 120 Asset retirement obligations 1,865 1,865 — 1,763 1,763 — Pension obligation (a) 9 9 — 9 9 — Unamortized energy contract liabilities 45 45 — 51 51 — Other noncurrent liabilities 122 122 — 127 127 — Noncurrent liabilities 2,207 2,120 81 2,162 2,031 120 Total liabilities $ 2,555 $ 2,382 $ 159 $ 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: June 30, 2015 Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 260 $ 127 $ 387 Total liabilities (a) 29 61 90 Exelon's ownership interest in VIE (a) — 16 16 Other ownership interests in VIE (a) 231 51 282 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 19 19 Contract intangible asset 9 — 9 Debt and payment guarantees — 3 3 Net assets pledged for Zion Station decommissioning (b) 23 — 23 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 $264 million and $319 million as of June 30, 2015 and December 31, 2014 , respectively; offset by payables to ZionSolutions, LLC of $241 million and $292 million as of June 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 June 30, 2015 and December 31, 2014 are as follows: June 30, 2015 December 31, 2014 Exelon (a) Generation BGE Exelon (a) Generation BGE Current assets $ 924 $ 894 $ 24 $ 1,271 $ 1,242 $ 21 Noncurrent assets 7,731 7,723 3 7,580 7,566 3 Total assets $ 8,655 $ 8,617 $ 27 $ 8,851 $ 8,808 $ 24 Current liabilities $ 378 $ 292 $ 79 $ 611 $ 526 $ 77 Noncurrent liabilities 2,860 2,773 81 2,730 2,600 120 Total liabilities $ 3,238 $ 3,065 $ 160 $ 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)	6 Months Ended
	Jun. 30, 2015
Regulated Operations [Abstract]
Schedule of Regulatory Assets	June 30, 2015 Exelon ComEd PECO BGE Regulatory assets Pension and other postretirement benefits $ 3,193 $ — $ — $ — Deferred income taxes 1,574 65 1,432 77 AMI programs 349 119 70 160 Under-recovered distribution service costs (a) 275 275 — — Debt costs 51 49 2 8 Fair value of BGE long-term debt 177 — — — Severance 11 — — 11 Asset retirement obligations 121 76 26 19 MGP remediation costs 245 210 34 1 Under-recovered uncollectible accounts 50 50 — — Renewable energy 223 223 — — Energy and transmission programs (b) (c) 53 34 — 19 Deferred storm costs 2 — — 2 Electric generation-related regulatory asset 25 — — 25 Rate stabilization deferral 121 — — 121 Energy efficiency and demand response programs 236 — — 236 Merger integration costs 7 — — 7 Conservation voltage reduction 2 — — 2 Other 46 9 30 5 Total regulatory assets 6,761 1,110 1,594 693 Less: current portion 785 276 42 207 Total noncurrent regulatory assets $ 5,976 $ 834 $ 1,552 $ 486 June 30, 2015 Exelon ComEd PECO BGE Regulatory liabilities Other postretirement benefits $ 68 $ — $ — $ — Nuclear decommissioning 2,831 2,354 477 — Removal costs 1,563 1,351 — 212 Energy efficiency and demand response programs 41 39 2 — DLC Program Costs 9 — 9 — Energy efficiency phase II 38 — 38 — Electric distribution tax repairs 102 — 102 — Gas distribution tax repairs 33 — 33 — Energy and transmission programs (b)(c)(d) 134 30 85 19 Over-recovered electric universal service fund costs 2 — 2 — Over-recovered revenue decoupling (e) 40 — — 40 Other 10 2 2 5 Total regulatory liabilities 4,871 3,776 750 276 Less: current portion 409 154 117 91 Total noncurrent regulatory liabilities $ 4,462 $ 3,622 $ 633 $ 185 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 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 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)(d) 84 19 58 7 Over-recovered electric universal service fund costs 2 — 2 — Revenue subject to refund 3 3 — — Over-recovered revenue decoupling (e) 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 June 30, 2015 , ComEd’s regulatory asset of $275 million was comprised of $209 million for the applicable annual reconciliations and $66 million related to significant one-time events including $51 million of deferred storm costs and $15 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 June 30, 2015 , ComEd’s regulatory asset of $34 million included $1 million related to under-recovered energy costs for non-hourly customers, $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 June 30, 2015 , ComEd’s regulatory liability of $30 million included $10 million related to over-recovered energy costs for hourly customers and $20 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 June 30, 2015 , BGE's regulatory asset of $19 million included $1 million associated with transmission costs recoverable through its FERC approved formula rate and $18 million related to under-recovered electric energy costs. As of June 30, 2015 , BGE's regulatory liability of $19 million related to $18 million of over-recovered natural gas supply costs and $ 6 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) As of June 30, 2015 , PECO's regulatory liability of $85 million included $35 million related to the DSP program, $44 million related to the over-recovered natural gas costs under the PGC, $5 million related to over-recovered electric transmission costs and $1 million related to the Non-Bypassable service charge included in the DSP program. 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. (e) Represents the electric and gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of June 30, 2015 , BGE had a regulatory liability of $11 million related to over-recovered electric revenue decoupling and a regulatory liability of $29 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.
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. If the costs are not fully recovered when PECO files its next gas distribution rate case, PECO will propose a mechanism to recover the remaining implementation costs as a distribution charge to low volume transportation customers or apply future discounts on purchased receivables from natural gas suppliers serving those customers. (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)	6 Months Ended
	Jun. 30, 2015
Property, Plant and Equipment [Abstract]
Schedule of Capital Leased Assets	At June 30, 2015 and December 31, 2014 , the components of the net investment in long-term leases were as follows: June 30, 2015 December 31, 2014 Estimated residual value of leased assets $ 639 $ 685 Less: unearned income 295 324 Net investment in long-term leases $ 344 $ 361

Implications of Potential Ear32

Implications of Potential Early Plant Retirements Implications of Potential Early Plant Retirements (Tables)	6 Months Ended
	Jun. 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 $ 48 $ 55 $ 30 $ 133 Nuclear fuel inventory 205 137 66 408 Completed plant, net 800 465 85 1,350 Construction work in progress 24 24 23 71 Liability Balances Asset retirement obligation (450 ) (287 ) (611 ) (1,348 ) 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)	6 Months Ended
	Jun. 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 June 30, 2015 and December 31, 2014 : Exelon June 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 546 $ 3 $ 543 $ — $ 546 Long-term debt (including amounts due within one year) 25,446 1,043 24,011 1,349 26,403 Long-term debt to financing trusts 648 — — 663 663 SNF obligation 1,021 — 838 — 838 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 June 30, 2015 and December 31, 2014 : Generation Exelon As of June 30, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 134 $ — $ — $ 134 $ 5,486 $ — $ — $ 5,486 Nuclear decommissioning trust fund investments Cash equivalents 333 55 — 388 333 55 — 388 Equity Domestic 2,389 2,055 — 4,444 2,389 2,055 — 4,444 Foreign 696 — — 696 696 — — 696 Equity funds subtotal 3,085 2,055 — 5,140 3,085 2,055 — 5,140 Fixed income Corporate debt — 1,860 250 2,110 — 1,860 250 2,110 U.S. Treasury and agencies 1,165 — — 1,165 1,165 — — 1,165 Foreign governments — 83 — 83 — 83 — 83 State and municipal debt — 405 — 405 — 405 — 405 Other — 463 — 463 — — 463 — — — 463 Fixed income subtotal 1,165 2,811 250 4,226 1,165 2,811 250 4,226 Middle market lending — — 417 417 — — 417 417 Private Equity — — 100 100 — — 100 100 Real Estate — — 19 19 — — — — 19 19 Other — 329 — 329 — 329 — 329 Nuclear decommissioning trust fund investments subtotal (b) 4,583 5,250 786 10,619 4,583 5,250 786 10,619 Generation Exelon As of June 30, 2015 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Pledged assets for Zion Station decommissioning Cash equivalents — 17 — 17 — 17 — 17 Equities 5 1 — 6 5 1 — 6 Fixed income U.S. Treasury and agencies 7 2 — 9 7 2 — 9 Corporate debt — 62 — 62 — 62 — 62 State and municipal debt — 10 — 10 — 10 — 10 Other — 3 — 3 — — 3 — — 3 Fixed income subtotal 7 77 — 84 7 77 — 84 Middle market lending — — 156 156 — — 156 156 Pledged assets for Zion Station decommissioning subtotal (c) 12 95 156 263 12 95 156 263 Rabbi trust investments in mutual funds (d)(e) 17 — — 17 48 — — 48 Commodity derivative assets Economic hedges 1,080 3,352 2,334 6,766 1,080 3,352 2,334 6,766 Proprietary trading 117 239 38 394 117 239 38 394 Effect of netting and allocation of collateral (f) (1,364 ) (2,753 ) (872 ) (4,989 ) (1,364 ) (2,753 ) (872 ) (4,989 ) Commodity derivative assets subtotal (167 ) 838 1,500 2,171 (167 ) 838 1,500 2,171 Interest rate and foreign currency derivative assets Derivatives designated as hedging instruments — 1 — 1 — 22 — 22 Economic hedges — 20 — 20 — 20 — 20 Proprietary trading 14 1 — 15 14 1 — 15 Effect of netting and allocation of collateral (8 ) (5 ) — (13 ) (8 ) (5 ) — (13 ) Interest rate and foreign currency derivative assets subtotal 6 17 — 23 6 38 — 44 Other investments — — 30 30 1 — 30 31 Total assets 4,585 6,200 2,472 13,257 9,969 6,221 2,472 18,662 Liabilities Commodity derivative liabilities Economic hedges (1,493 ) (3,129 ) (1,462 ) (6,084 ) (1,493 ) (3,129 ) (1,685 ) (6,307 ) Proprietary trading (111 ) (248 ) (43 ) (402 ) (111 ) (248 ) (43 ) (402 ) Effect of netting and allocation of collateral (f) 1,641 3,296 1,026 5,963 1,641 3,296 1,026 5,963 Commodity derivative liabilities subtotal 37 (81 ) (479 ) (523 ) 37 (81 ) (702 ) (746 ) Interest rate and foreign currency derivative liabilities Derivatives designated as hedging instruments — (14 ) — (14 ) — (14 ) — (14 ) Economic hedges — (4 ) — (4 ) — (4 ) — (4 ) Proprietary trading (14 ) — — (14 ) (14 ) — — (14 ) Effect of netting and allocation of collateral 14 5 — 19 14 5 — 19 Interest rate and foreign currency derivative liabilities subtotal — (13 ) — (13 ) — (13 ) — (13 ) Deferred compensation obligation — (26 ) — (26 ) — (88 ) — (88 ) Total liabilities 37 (120 ) (479 ) (562 ) 37 (182 ) (702 ) (847 ) Total net assets $ 4,622 $ 6,080 $ 1,993 $ 12,695 $ 10,006 $ 6,039 $ 1,770 $ 17,815 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 Generation Exelon As of December 31, 2014 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total 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 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 Generation Exelon As of December 31, 2014 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total 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 $(12) million and $(5) million at June 30, 2015 and December 31, 2014 , respectively. These items consist of 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 June 30, 2015 and December 31, 2014 , respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, and payables related to pending securities purchases. (d) Excludes $36 million and $35 million of cash surrender value of life insurance investment at June 30, 2015 and December 31, 2014 , respectively, at Exelon Consolidated. Excludes $13 million and $11 million and of cash surrender value of life insurance investment at June 30, 2015 and December 31, 2014 , respectively, at Generation. (e) The mutual funds held by the Rabbi trusts at Exelon include $47 million related to deferred compensation and $1 million related to Supplemental Executive Retirement Plan at June 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 $277 million , $543 million and $154 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of June 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 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 June 30, 2015 and December 31, 2014 : ComEd PECO BGE As of June 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 $ 5 $ — $ — $ 5 $ 5 $ — $ — $ 5 $ 46 $ — $ — $ 46 Rabbi trust investments in mutual funds (a) — — — — 8 — — 8 5 — — 5 Total assets 5 — — 5 13 — — 13 51 — — 51 Liabilities Deferred compensation obligation — (7 ) — (7 ) — (10 ) — (10 ) — (3 ) — (3 ) Mark-to-market derivative liabilities (b) — — (223 ) (223 ) — — — — — — — — Total liabilities — (7 ) (223 ) (230 ) — (10 ) — (10 ) — (3 ) — (3 ) Total net assets (liabilities) $ 5 $ (7 ) $ (223 ) $ (225 ) $ 13 $ (10 ) $ — $ 3 $ 51 $ (3 ) $ — $ 48 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 June 30, 2015 and December 31, 2014 , respectively. (b) The Level 3 balance includes the current and noncurrent liability of $ 20 million and $ 203 million at June 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 six months ended June 30, 2015 and 2014 : Generation ComEd Exelon Three Months Ended June 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 March 31, 2015 $ 715 $ 178 $ 1,066 $ 3 $ 1,962 $ (241 ) $ — $ 1,721 Total realized / unrealized gains (losses) Included in net income 2 — (7 ) (a) — (5 ) — — (5 ) Included in noncurrent payables to affiliates 7 — — — 7 — (7 ) — Included in payable for Zion Station decommissioning — (2 ) — — (2 ) — — (2 ) Included in regulatory assets — — — — — 18 7 25 Change in collateral — — (30 ) — (30 ) — — (30 ) Purchases, sales, issuances and settlements Purchases 99 6 16 27 148 — — 148 Sales — (26 ) (5 ) — (31 ) — — (31 ) Settlements (37 ) — — — (37 ) — — (37 ) Transfers into Level 3 — — 11 — 11 — — 11 Transfers out of Level 3 — — (30 ) — (30 ) — — (30 ) Balance as of June 30, 2015 $ 786 $ 156 $ 1,021 $ 30 $ 1,993 $ (223 ) $ — $ 1,770 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 June 30, 2015 $ 4 $ — $ 175 $ — $ 179 $ — $ — $ 179 Generation ComEd Exelon Six Months Ended June 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 — (39 ) (a) — (35 ) — — (35 ) Included in noncurrent payables to affiliates 15 — — — 15 — (15 ) — Included in payable for Zion Station decommissioning — 1 — — 1 — — 1 Included in regulatory assets — — — — — (16 ) 15 (1 ) Change in collateral — — (18 ) — (18 ) — — (18 ) Purchases, sales, issuances and settlements Purchases 146 11 57 27 241 — — 241 Sales (8 ) (40 ) (5 ) — (53 ) — — (53 ) Settlements (66 ) — — — (66 ) — — (66 ) Transfers into Level 3 4 — 11 — 15 — — 15 Transfers out of Level 3 — — (35 ) — (35 ) — — (35 ) Balance as of June 30, 2015 $ 786 $ 156 $ 1,021 $ 30 $ 1,993 $ (223 ) $ — $ 1,770 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 six months ended June 30, 2015 $ 5 $ — $ 355 $ — $ 360 $ — $ — $ 360 ______________ (a) Includes the reclassification of $(182) million and $(394) million of realized losses due to the settlement of derivative contracts for the three and six months ended June 30, 2015 , respectively. (b) Includes $14 million of increases in fair value and realized losses due to settlements of $4 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended June 30, 2015 . Includes $22 million of decreases in fair value and realized losses due to settlements of $6 million for the six months ended June 30, 2015 . Generation ComEd Exelon Three Months Ended June 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 March 31, 2014 $ 486 $ 137 $ 287 $ 10 $ 920 $ (168 ) $ — $ 752 Total realized / unrealized gains (losses) Included in net income 2 — (48 ) (a) — (46 ) — — (46 ) Included in noncurrent payables to affiliates 8 — — — 8 — (8 ) — Included in payable for Zion Station decommissioning — 4 — — 4 — — 4 Included in regulatory assets — — — — — 34 8 42 Change in collateral — — 34 — 34 — — 34 Purchases, sales, issuances and settlements Purchases 109 13 5 — 127 — — 127 Sales (1 ) (21 ) (4 ) — (26 ) — — (26 ) Settlements (12 ) — — — (12 ) — — (12 ) Transfers into Level 3 — — (4 ) — (4 ) — — (4 ) Transfers out of Level 3 — — (28 ) — (28 ) — — (28 ) Balance as of June 30, 2014 $ 592 $ 133 $ 242 $ 10 $ 977 $ (134 ) $ — $ 843 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 June 30, 2014 $ 2 $ — $ 19 $ — $ 21 $ — $ — $ 21 Generation ComEd Exelon Six Months Ended June 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 3 — (360 ) (a) — (357 ) — — $ (357 ) Included in noncurrent payables to affiliates 11 — — — 11 — (11 ) $ — Included in payable for Zion Station decommissioning — 4 — — 4 — — $ 4 Included in regulatory assets — — — — — 59 11 $ 70 Change in collateral — — 178 — 178 — — $ 178 Purchases, sales, issuances and settlements Purchases 249 42 15 2 308 — — $ 308 Sales (2 ) (25 ) (6 ) — (33 ) — — $ (33 ) Settlements (19 ) — — — (19 ) — — $ (19 ) Transfers into Level 3 — — (30 ) — (30 ) — — $ (30 ) Transfers out of Level 3 — — (20 ) (7 ) (27 ) — — $ (27 ) Balance as of June 30, 2014 $ 592 $ 133 $ 242 $ 10 $ 977 $ (134 ) $ — $ 843 The amount of total gains included in income attributed to the change in unrealized gains related to assets and liabilities held for the six months ended June 30, 2014 $ 2 $ — $ (427 ) $ — $ (425 ) $ — $ — $ (425 ) ______________ (a) Includes the reclassification of $ 67 million of realized losses due to the settlement of derivative contracts for the three and six months ended June 30, 2014. (b) Includes $34 million of increases in fair value and immaterial realized losses recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended June 30, 2014 . Includes $64 million of increases in fair value and realized gains due to settlements of $5 million for the six months ended June 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 six months ended June 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 June 30, 2015 $ (17 ) $ 10 $ 2 $ (17 ) $ 10 $ 2 Total gains (losses) included in net income for the six months ended June 30, 2015 (27 ) (12 ) 4 (27 ) (12 ) 4 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended June 30, 2015 171 4 4 171 4 4 Change in the unrealized gains (losses) relating to assets and liabilities held for the six months ended June 30, 2015 340 15 5 340 15 5 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 June 30, 2014 $ (62 ) $ 14 $ 2 $ (62 ) $ 14 $ 2 Total gains (losses) included in net income for the six months ended June 30, 2014 (330 ) (30 ) 3 (330 ) (30 ) 3 Change in the unrealized gains (losses) relating to assets and liabilities held for the three months ended June 30, 2014 (10 ) 29 2 (10 ) 29 2 Change in the unrealized gains (losses) relating to assets and liabilities held for the six months ended June 30, 2014 (435 ) 8 2 (435 ) 8 2 ______________ (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 June 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 40 $ — $ 40 $ — $ 40 Long-term debt (including amounts due within one year) 9,001 — 7,995 1,349 9,344 SNF obligation 1,021 — 838 — 838 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 June 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 503 $ — $ 503 $ — $ 503 Long-term debt (including amounts due within one year) 6,099 — 6,640 — 6,640 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 June 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Long-term debt (including amounts due within one year) $ 2,246 $ — $ 2,432 $ — $ 2,432 Long-term debt to financing trusts 184 — — 199 199 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 June 30, 2015 Carrying Amount Fair Value Level 1 Level 2 Level 3 Total Short-term liabilities $ 3 $ 3 $ — $ — $ 3 Long-term debt (including amounts due within one year) 1,905 — 2,086 — 2,086 Long-term debt to financing trusts 258 — — 258 258 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)	6 Months Ended
	Jun. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of the derivative fair value	Below is a summary of the interest rate and foreign currency hedges as of June 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 $ — $ 10 $ 10 $ (10 ) $ 10 $ — $ — $ — $ — $ 10 Mark-to-market derivative assets assets) 1 10 6 (3 ) 14 21 — — 21 35 Total mark-to-market derivative 1 20 16 (13 ) 24 21 — — 21 45 Mark-to-market derivative liabilities (current liabilities) (9 ) (5 ) (9 ) 14 (9 ) — — — — (9 ) Mark-to-market derivative liabilities (noncurrent liabilities) (5 ) — (5 ) 5 (5 ) — — — — (5 ) Total mark-to-market derivative (14 ) (5 ) (14 ) 19 (14 ) — — — — (14 ) Total mark-to-market derivative (liabilities) $ (13 ) $ 15 $ 2 $ 6 $ 10 $ 21 $ — $ — $ 21 $ 31 _____________ (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. 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 June 30, Income Statement Location 2015 2014 2015 2014 Gain (Loss) on Swaps Gain (Loss) on Borrowings Generation Interest expense (a) $ — $ (3 ) $ — $ 2 Exelon Interest expense (11 ) 3 (12 ) (3 ) Six Months Ended June 30, Income Statement Location 2015 2014 2015 2014 Gain (Loss) on Swaps Gain (Loss) on Borrowings Generation Interest expense (a) $ (1 ) $ (8 ) $ — $ 1 Exelon Interest expense (2 ) 5 (4 ) (7 ) __________ (a) For the three and six months ended June 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 six months ended June 30, 2014 , the loss on Generation swaps included $4 million and $8 million realized in earnings, respectively, with an immaterial amount excluded from hedge effectiveness testing. The following table provides a summary of the derivative fair value balances recorded by the Registrants as of June 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) $ 4,398 $ 346 $ (3,349 ) $ 1,395 $ — $ 1,395 Mark-to-market derivative assets (noncurrent assets) 2,368 48 (1,640 ) 776 — 776 Total mark-to-market derivative assets 6,766 394 (4,989 ) 2,171 — 2,171 Mark-to-market derivative liabilities (current liabilities) (3,793 ) (347 ) 4,004 (136 ) (20 ) (156 ) Mark-to-market derivative liabilities (noncurrent liabilities) (2,291 ) (55 ) 1,959 (387 ) (203 ) (590 ) Total mark-to-market derivative liabilities (6,084 ) (402 ) 5,963 (523 ) (223 ) (746 ) Total mark-to-market derivative net assets (liabilities) $ 682 $ (8 ) $ 974 $ 1,648 $ (223 ) $ 1,425 _________ (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 $297 million and $144 million , respectively, and current and noncurrent liabilities are shown net of collateral of $358 million and $175 million , respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $974 million at June 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 actual physical power sales, result in the ultimate recognition of net revenues at the contracted price. Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Three Months Ended June 30, 2015 Income Statement Location Total Cash Flow Hedges Total Cash Flow Hedges Accumulated OCI derivative gain at March 31, 2015 $ (23 ) $ (22 ) Effective portion of changes in fair value — 1 Reclassifications from accumulated OCI to net income Interest Expense 2 2 Accumulated OCI derivative gain at June 30, 2015 $ (21 ) $ (19 ) Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Six Months Ended June 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 (6 ) (10 ) Reclassifications from accumulated OCI to net income Other, net — 16 (a) Reclassifications from accumulated OCI to net income Interest Expense 5 5 Reclassifications from accumulated OCI to net income Operating Revenues (2 ) (2 ) Accumulated OCI derivative gain at June 30, 2015 $ (21 ) $ (19 ) ______ (a) Amount is net of related income tax expense of $10 million for the six months ended June 30, 2015 . Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Three Months Ended June 30, 2014 Income Statement Location Total Cash Flow Hedges Total Cash Flow Hedges Accumulated OCI derivative gain at March 31, 2014 $ 88 $ 95 Effective portion of changes in fair value (5 ) (10 ) Reclassifications from accumulated OCI to net income Operating Revenues (38 ) (a) (38 ) (a) Accumulated OCI derivative gain at June 30, 2014 $ 45 $ 47 ______ (a) Amount is net of related income tax expense of $25 million for the three months ended June 30, 2014 . Total Cash Flow Hedge OCI Activity, Net of Income Tax Generation Exelon Six Months Ended June 30, 2014 Income Statement Location Total Cash Flow Hedges Total Cash Flow Hedges Accumulated OCI derivative gain at December 31, 2013 $ 116 $ 120 Effective portion of changes in fair value (9 ) (11 ) Reclassifications from accumulated OCI to net income Operating Revenues (62 ) (a) (62 ) (a) Accumulated OCI derivative gain at June 30, 2014 $ 45 $ 47 __________ (a) Amount is net of related income tax expense of $40 million for the six months ended June 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 June 30, Six Months Ended June 30, 2015 2014 2015 2014 Change in fair value of commodity positions Operating Revenues $ 7 $ 1 $ 8 $ — Reclassification to realized at settlement of commodity positions Operating Revenues (7 ) (8 ) (5 ) (7 ) Net commodity mark-to-market gains (losses) Operating Revenues — (7 ) 3 (7 ) Change in fair value of treasury positions Operating Revenues — — 4 (1 ) Reclassification to realized at settlement of treasury positions Operating Revenues (2 ) 1 (6 ) 1 Net treasury mark-to-market gains (losses) Operating Revenues (2 ) 1 (2 ) — Total Net mark-to-market gains (losses) Operating Revenues $ (2 ) $ (6 ) $ 1 $ (7 ) 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 June 30, 2015 Operating Revenues Purchased Power and Fuel Interest Expense Total Interest Total Change in fair value of commodity positions $ 197 $ 110 $ — $ 307 $ — $ 307 Reclassification to realized at settlement of commodity positions (167 ) 100 — (67 ) — (67 ) Net commodity mark-to-market gains (losses) 30 210 — 240 — 240 Change in fair value of treasury positions (3 ) — — (3 ) 114 111 Reclassification to realized at settlement of treasury positions (2 ) — — (2 ) 64 62 Net treasury mark-to-market gains (losses) (5 ) — — (5 ) 178 173 Net mark-to-market gains (losses) $ 25 $ 210 $ — $ 235 $ 178 $ 413 Generation HoldCo Exelon Six Months Ended June 30, 2015 Operating Revenues Purchased Power and Fuel Interest Expense Total Interest Total Change in fair value of commodity positions $ 377 $ 15 $ — $ 392 $ — $ 392 Reclassification to realized at settlement of commodity positions (204 ) 203 — (1 ) — (1 ) Net commodity mark-to-market gains (losses) 173 218 — 391 — 391 Change in fair value of treasury positions 10 — — 10 36 46 Reclassification to realized at settlement of treasury positions (4 ) — — (4 ) 64 60 Net treasury mark-to-market gains (losses) 6 — — 6 100 106 Net mark-to-market gains (losses) $ 179 $ 218 $ — $ 397 $ 100 $ 497 Generation HoldCo Exelon Three Months Ended June 30, 2014 Operating Revenues Purchased Power and Fuel Interest Expense Total Interest Total Change in fair value of commodity positions $ (124 ) $ 111 $ — $ (13 ) $ — $ (13 ) Reclassification to realized at settlement of commodity positions 45 (42 ) — 3 — 3 Net commodity mark-to-market gains (losses) (79 ) 69 — (10 ) — (10 ) Change in fair value of treasury positions (3 ) — (1 ) (4 ) — (4 ) Reclassification to realized at settlement of treasury positions (1 ) — — (1 ) — (1 ) Net treasury mark-to-market gains (losses) (4 ) — (1 ) (5 ) — (5 ) Net mark-to-market gains (losses) $ (83 ) $ 69 $ (1 ) $ (15 ) $ — $ (15 ) Generation HoldCo Exelon Six Months Ended June 30, 2014 Operating Revenues Purchased Power and Fuel Interest Expense Total Interest Total Change in fair value of commodity positions $ (975 ) $ 282 $ — $ (693 ) $ — $ (693 ) Reclassification to realized at settlement of commodity positions 137 (183 ) — (46 ) — (46 ) Net commodity mark-to-market gains (losses) (838 ) 99 — (739 ) — (739 ) Change in fair value of treasury positions (4 ) — (1 ) (5 ) — (5 ) Reclassification to realized at settlement of treasury positions (1 ) — — (1 ) — (1 ) Net treasury mark-to-market gains (losses) (5 ) — (1 ) (6 ) — (6 ) Net mark-to-market gains (losses) $ (843 ) $ 99 $ (1 ) $ (745 ) $ — $ (745 )
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 June 30, 2015 December 31, 2014 Gross Fair Value of Derivative Contracts Containing this Feature (a) $ (1,558 ) $ (1,433 ) Offsetting Fair Value of In-the-Money Contracts Under Master Netting Arrangements (b) 1,275 1,140 Net Fair Value of Derivative Contracts Containing This Feature (c) $ (283 ) $ (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 $36 million , $35 million and $31 million , as of June 30, 2015 , respectively. Rating as of June 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 $ 1,643 $ 24 $ 1,619 1 $ 444 Non-investment grade 55 18 37 — — No external ratings Internally rated — investment grade 498 — 498 — — Internally rated — non-investment grade 48 6 42 — — Total $ 2,244 $ 48 $ 2,196 1 $ 444 Net Credit Exposure by Type of Counterparty As of June 30, 2015 Financial institutions $ 383 Investor-owned utilities, marketers, power producers 880 Energy cooperatives and municipalities 881 Other 52 Total $ 2,196 _____________________ (a) As of June 30, 2015 , credit collateral held from counterparties where Generation had credit exposure included $30 million of cash and $18 million of letters of credit.

Debt and Credit Agreements (Tab

Debt and Credit Agreements (Tables)	6 Months Ended
	Jun. 30, 2015
Debt Disclosure [Abstract]
Schedule of Short-term Debt	Exelon had bank lines of credit under committed credit facilities at June 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 on October 16, 2015. These facilities are solely utilized to issue letters of credit. As of June 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 June 30, 2015 and December 31, 2014 : Commercial Paper Borrowings June 30, 2015 December 31, 2014 Exelon Corporate $ — $ — Generation — — ComEd 503 304 PECO — — BGE — 120
Schedule Of Issuance Of Long Term Debt	During the six months ended June 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) (b) 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) (b) 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) (b) 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 licensers Generation Senior Unsecured Notes (c) 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 (d) 2.50 - 2.70% 2019 - 2020 $ 435 General corporate purposes Generation Albany Green Energy Project Financing LIBOR + 1.25% November 17, 2017 $ 50 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) The 2025 notes, the 2035 notes and the 2045 notes must be redeemed upon the earlier of (i) December 31, 2015, if the PHI acquisition is not consummated on or prior to such date, or (ii) the date on which the Merger Agreement relating to the PHI acquisition is terminated. (c) 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. (d) The Tax Exempt Pollution Control Revenue Bonds have a mandatory put date that ranges from March 1, 2019 - September 1, 2020. 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. Albany Green Energy Project (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.
Schedule of Long-term Debt Instruments	During the six months ended June 30, 2014 , the following long-term debt was issued:
Retirement and Redemptions of Current and Long-Term Debt	During the six months ended June 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 $ 11 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 $ 1 Generation Clean Horizons Solar Nonrecourse Debt 2.56 % September 7, 2030 $ 1 Generation Sacramento Solar Nonrecourse Debt 2.56 % December 31, 2030 $ 1 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 six months ended June 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 Generation (a) Senior Unsecured Notes 4.55 % June 15, 2015 $ 550 Generation CEU Upstream Nonrecourse Debt LIBOR + 2.25% January 14, 2019 $ 2 Generation AVSR DOE Nonrecourse Debt 2.29%-3.56% January 5, 2037 $ 6 Generation Kennett Square Capital Lease 7.83 % September 20, 2020 $ 2 Generation Continental Wind Nonrecourse Debt 6.00 % February 28, 2033 $ 10 Generation ExGen Texas Power Nonrecourse Debt LIBOR + 4.75% September 8, 2021 $ 3 Generation ExGen Renewables I Nonrecourse Debt 4.49 % 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

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation	For the Three Months Ended June 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 3.9 3.4 5.6 1.4 5.3 Qualified nuclear decommissioning trust fund income (1.0 ) (1.7 ) — — — Domestic production activities deduction (2.0 ) (3.4 ) — — — Health care reform legislation — — — — 0.1 Amortization of investment tax credit, net deferred taxes (0.6 ) (0.9 ) (0.3 ) (0.1 ) (0.2 ) Plant basis differences (1.0 ) — (0.1 ) (9.0 ) (0.5 ) Production tax credits and other credits (1.3 ) (2.2 ) — — — Noncontrolling interest (0.4 ) (0.6 ) — — — Other 1.4 2.0 0.5 0.5 0.8 Effective income tax rate 34.0 % 31.6 % 40.7 % 27.8 % 40.5 % For the Six Months Ended June 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 3.2 3.0 5.3 1.3 5.3 Qualified nuclear decommissioning trust fund income 0.6 0.9 — — — Domestic production activities deduction (2.1 ) (3.4 ) — — — Health care reform legislation — — — — 0.2 Amortization of investment tax credit, net deferred taxes (0.8 ) (1.1 ) (0.3 ) (0.1 ) (0.1 ) Plant basis differences (1.1 ) — (0.2 ) (7.5 ) (0.3 ) Production tax credits and other credits (1.6 ) (2.5 ) — — — Noncontrolling interest (0.6 ) (0.8 ) — — — Other 0.8 0.6 0.4 0.2 — Effective income tax rate 33.4 % 31.7 % 40.2 % 28.9 % 40.1 % For the Three Months Ended June 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 2.1 1.7 4.6 (0.5 ) 4.1 Qualified nuclear decommissioning trust fund income 4.1 6.0 — — — Domestic production activities deduction (2.0 ) (2.9 ) — — — Health care reform legislation — — 0.2 — 0.2 Amortization of investment tax credit, net deferred taxes (0.4 ) (0.5 ) (0.3 ) (0.1 ) (0.7 ) Plant basis differences (1.6 ) — (0.4 ) (13.2 ) 5.1 Production tax credits and other credits (0.8 ) (1.1 ) — — — Noncontrolling interest (2.0 ) (2.9 ) — — — Other (1.2 ) (0.4 ) 0.2 0.3 (1.3 ) Effective income tax rate 33.2 % 34.9 % 39.3 % 21.5 % 42.4 % For the Six Months Ended June 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 (0.6 ) (14.7 ) 5.0 0.4 5.0 Qualified nuclear decommissioning trust fund income 5.9 27.7 — — — Domestic production activities deduction (3.2 ) (14.8 ) — — — Health care reform legislation 0.1 — 0.2 — 0.2 Amortization of investment tax credit, net deferred taxes (1.2 ) (4.9 ) (0.3 ) (0.1 ) (0.3 ) Plant basis differences (3.0 ) — (0.5 ) (10.8 ) 0.4 Production tax credits and other credits (2.4 ) (11.1 ) — — — Noncontrolling interest (1.9 ) (8.8 ) — — — Other (3.1 ) (8.9 ) 0.2 0.3 0.1 Effective income tax rate 25.6 % (0.5 )% 39.6 % 24.8 % 40.4 %

Nuclear Decommissioning (Tables

Nuclear Decommissioning (Tables) - Exelon Generation Co L L C [Member]	6 Months Ended
	Jun. 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 June 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 (b) 55 Accretion expense 189 Costs incurred to decommission retired plants (1 ) Nuclear decommissioning ARO at June 30, 2015 (a) $ 7,204 ___________ (a) Includes $7 million and $8 million as the current portion of the ARO at June 30, 2015 and December 31, 2014 respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets. (b) Represents a purchase accounting adjustment to the fair value of the CENG ARO liability as of April 1, 2014, the date of consolidation. See Note 6 — Investment in Constellation Energy Nuclear Group, LLC for additional information.
Unrealized Gains (Losses) on nuclear decommissioning trust funds	The following table provides unrealized gains (losses) on NDT funds for the three and six months ended June 30, 2015 and 2014 : Exelon and Generation Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Net unrealized gains (losses) on decommissioning trust funds — Regulatory Agreement Units (a) $ (133 ) $ 172 $ (85 ) $ 234 Net unrealized gains (losses) on decommissioning trust funds — Non-Regulatory Agreement Units (b)(c) (96 ) 128 (56 ) 141 ___________ (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 $10 million of net unrealized gains related to the Zion Station pledged assets for the three months ended June 30, 2014 and $9 million and $20 million of net unrealized gains related to the Zion Station pledged assets for the six months ended June 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 June 30, 2015 and December 31, 2014 : Exelon and Generation June 30, 2015 December 31, 2014 Carrying value of Zion Station pledged assets $ 264 $ 319 Payable to Zion Solutions (a) 241 292 Current portion of payable to Zion Solutions (b) 106 137 Cumulative withdrawals by Zion Solutions to pay decommissioning costs 731 666 ___________ (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.

Retirement Benefits (Tables)

Retirement Benefits (Tables)	6 Months Ended
	Jun. 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 six months ended June 30, 2015 and 2014 . Pension Benefits Three Months Ended June 30, Other Postretirement Benefits Three Months Ended June 30, 2015 (a) 2014 (a) 2015 (a) 2014 (a) Service cost $ 81 $ 74 $ 29 $ 30 Interest cost 178 190 42 47 Expected return on assets (256 ) (251 ) (37 ) (38 ) Amortization of: Prior service cost (benefit) 4 4 (44 ) (30 ) Actuarial loss 142 104 21 12 Net periodic benefit cost $ 149 $ 121 $ 11 $ 21 Pension Benefits Six Months Ended June 30, Other Postretirement Benefits Six Months Ended June 30, 2015 (a) 2014 (a) 2015 (a) 2014 (a) Service cost $ 163 $ 143 $ 59 $ 62 Interest cost 355 373 83 103 Expected return on assets (513 ) (492 ) (75 ) (76 ) Amortization of: Prior service cost (benefit) 7 7 (88 ) (34 ) Actuarial loss 285 209 41 20 Net periodic benefit cost $ 297 $ 240 $ 20 $ 75 ______________ (a) For the three months ended June 30, 2015 , the cost for pension benefits and other postretirement benefits related to CENG were $3 million and $3 million , respectively. For the six months ended June 30, 2015 , the cost for pension benefits and other postretirement benefits related to CENG were $5 million and $6 million , respectively. For the period of April 1, 2014 to June 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.
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 six months ended June 30, 2015 and 2014 . Three Months Ended June 30, Six Months Ended June 30, Pension and Other Postretirement Benefit Costs 2015 2014 2015 2014 Generation (a) $ 68 $ 63 $ 133 $ 139 ComEd 51 40 103 96 PECO 10 9 19 21 BGE 17 17 33 33 BSC (b) 14 13 29 26 ______________ (a) For the three and six months ended June 30, 2015 , the costs related to CENG were $6 million and $11 million , respectively. For the period of April 1, 2014 to June 30, 2014, amounts include $5 million related to CENG. (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 six months ended June 30, 2015 and 2014 : Three Months Ended June 30, Six Months Ended June 30, Savings Plan Matching Contributions 2015 2014 2015 2014 Exelon (a) $ 38 $ 19 $ 60 $ 48 Generation (a) 20 10 33 24 ComEd 8 5 13 12 PECO 3 2 4 4 BGE 3 1 5 4 BSC (b) 4 1 5 4 _______________ (a) Includes $3 million and $4 million , respectively, related to CENG for the three and six months ended June 30, 2015 . For the period of April 1, 2014 to June 30, 2014, amounts include $1 million related to CENG. (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)	6 Months Ended
	Jun. 30, 2015
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs	For the three and six months ended June 30, 2015 and 2014 , the Registrants recorded the following severance costs 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 June 30, 2015 $ 1 $ (1 ) $ — $ — $ — June 30, 2014 4 2 — — — Six Months Ended June 30, 2015 $ 21 $ 17 $ — $ — $ — June 30, 2014 6 4 — — —

Changes in Accumulated Other 40

Changes in Accumulated Other Comprehensive Income (Tables)	6 Months Ended
	Jun. 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 six months ended June 30, 2015 and 2014 : Six Months Ended June 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 (10 ) — (29 ) (9 ) — (48 ) Amounts reclassified from AOCI (b) 19 — 87 — — 106 Net current-period OCI 9 — 58 (9 ) — 58 Ending balance $ (19 ) $ 3 $ (2,582 ) $ (28 ) $ — $ (2,626 ) Generation (a) Beginning balance $ (18 ) $ 1 $ — $ (19 ) $ — $ (36 ) OCI before reclassifications (6 ) 1 — (9 ) — (14 ) Amounts reclassified from AOCI (b) 3 — — — — 3 Net current-period OCI (3 ) 1 — (9 ) — (11 ) Ending balance $ (21 ) $ 2 $ — $ (28 ) $ — $ (47 ) 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. Six Months Ended June 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 (11 ) 1 246 (1 ) 11 246 Amounts reclassified from AOCI (b) (62 ) — 66 — (116 ) (112 ) Net current-period OCI (73 ) 1 312 (1 ) (105 ) 134 Ending balance $ 47 $ 3 $ (1,948 ) $ (11 ) $ 3 $ (1,906 ) Generation (a) Beginning balance $ 114 $ 2 $ — $ (10 ) $ 108 $ 214 OCI before reclassifications (8 ) (1 ) — (1 ) 11 1 Amounts reclassified from AOCI (b) (62 ) — — — (116 ) (178 ) Net current-period OCI (70 ) (1 ) — (1 ) (105 ) (177 ) Ending balance $ 44 $ 1 $ — $ (11 ) $ 3 $ 37 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 six months ended June 30, 2015 and 2014 . Three Months Ended June 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 $ (2 ) $ (2 ) Interest expense (2 ) (2 ) Total before tax — — Tax benefit $ (2 ) $ (2 ) 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 27 — Tax benefit $ (44 ) $ — Net of tax Total Reclassifications for the period $ (46 ) $ (2 ) Net of Tax Six Months Ended June 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 (5 ) (5 ) Interest expense (29 ) (3 ) Total before tax 10 — Tax benefit $ (19 ) $ (3 ) Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 38 $ — Actuarial losses (b) (180 ) — (142 ) — Total before tax 55 — Tax benefit $ (87 ) $ — Net of tax Total Reclassifications for the period $ (106 ) $ (3 ) Net of Tax Three months ended June 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 $ 63 $ 63 Operating revenues 63 63 Total before tax (25 ) (25 ) Tax (expense) $ 38 $ 38 Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 12 $ — Actuarial losses (b) (61 ) — (49 ) — Total before tax 18 — Tax benefit $ (31 ) $ — Net of tax Equity investments Reversal of CENG equity method AOCI $ 193 $ 193 Gain on consolidation of CENG 193 193 Total before tax (77 ) (77 ) Tax benefit $ 116 $ 116 Net of tax Total reclassifications for the period $ 123 $ 154 Net of Tax Six Months Ended June 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 $ 102 $ 102 Operating revenues 102 102 Total before tax (40 ) (40 ) Tax (expense) $ 62 $ 62 Net of tax Amortization of pension and other postretirement benefit plan items Prior service costs (b) $ 10 $ — Actuarial losses (b) (117 ) — (107 ) — Total before tax 41 — Tax benefit $ (66 ) $ — Net of tax Equity investments Reversal of CENG equity method AOCI $ 193 $ 193 Gain on consolidation of CENG 193 193 Total before tax (77 ) (77 ) Tax benefit $ 116 $ 116 Net of tax Total reclassifications for the period $ 112 $ 178 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 six months ended June 30, 2015 and 2014 : Three Months Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Exelon Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 8 $ 5 $ 15 $ 5 Actuarial loss reclassified to periodic cost (35 ) (23 ) (69 ) (46 ) Pension and non-pension postretirement benefit plans valuation adjustment — (166 ) 17 (159 ) Change in unrealized (gain) loss on cash flow hedges (2 ) 28 (6 ) 48 Change in unrealized income on equity investments — 77 — 70 Change in unrealized loss on marketable securities 1 — 1 — Total $ (28 ) $ (79 ) $ (42 ) $ (82 ) Generation Change in unrealized (gain) loss on cash flow hedges $ (1 ) $ 25 $ 1 $ 44 Change in unrealized income on equity investments — 77 — 70 Change in marketable securities — — 1 (2 ) Total $ (1 ) $ 102 $ 2 $ 112

Earnings Per Share and Equity41

Earnings Per Share and Equity (Tables)	6 Months Ended
	Jun. 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 June 30, Six Months Ended June 30, 2015 2014 2015 2014 Net income attributable to common shareholders $ 638 $ 522 $ 1,331 $ 612 Average common shares outstanding — basic 863 860 862 860 Potentially dilutive effect of stock options, performance share awards and restricted stock 3 4 4 3 Average common shares outstanding — diluted 866 864 866 863

Commitments and Contingencies42

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2015
Commitments And Contingencies Tables Disclosure [Line Items]
Energy Commitments	As of June 30, 2015 , Generation’s commitments relating to its purchases from unaffiliated utilities and others of energy, capacity, transmission rights and RECs, are as indicated in the following table: Net Capacity Purchases (a) REC Purchases (b) Transmission Rights Purchases (c) Total 2015 $ 218 $ 58 $ 7 $ 283 2016 280 288 15 583 2017 207 187 16 410 2018 96 72 17 185 2019 101 11 18 130 Thereafter 263 1 38 302 Total $ 1,165 $ 617 $ 111 $ 1,893 ____________________ (a) Net capacity purchases include PPAs and other capacity contracts including those that are accounted for as operating leases. Amounts presented in the commitments represent Generation’s expected payments under these arrangements at June 30, 2015 , net of fixed capacity payments expected to be received ("capacity offsets") by Generation under contracts to resell such acquired capacity to third parties under long-term capacity sale contracts. As of June 30, 2015 , capacity offsets were $ 75 million, $ 146 million, $ 149 million, $ 150 million, $ 151 million, and $ 604 million for years 2015, 2016, 2017, 2018, 2019, and thereafter, respectively. Expected payments include certain fixed capacity charges which may be reduced based on plant availability. (b) The table excludes renewable energy purchases that are contingent in nature. (c) Transmission rights purchases include estimated commitments for additional transmission rights that will be required to fulfill firm sales contracts.
Utility Energy Purchase Commitments	ComEd’s, PECO’s and BGE’s electric supply procurement, curtailment services, REC and AEC purchase commitments, as applicable, as of June 30, 2015 are as follows: Expiration within Total 2015 2016 2017 2018 2019 2020 and beyond ComEd Electric supply procurement (a) $ 697 $ 251 $ 262 $ 163 $ 21 $ — $ — Renewable energy and RECs (b) 1,481 38 76 77 78 79 1,133 PECO Electric supply procurement (c) 671 368 270 33 — — — AECs (d) 13 2 2 2 2 2 3 BGE Electric supply procurement (e) 1,389 462 675 252 — — — Curtailment services (f) 95 20 34 29 12 — — ___________________ (a) ComEd entered into various contracts for the procurement of electricity that started to expire in 2012, and will continue to expire through 2018. ComEd is permitted to recover its electric supply procurement costs from retail customers with no mark-up. As of June 30, 2015 , ComEd has completed the ICC-approved procurement process for a portion of its energy requirements through the periods ending May 31, 2015, 2016 and 2017. (b) Primarily related to ComEd 20-year contracts for renewable energy and RECs that began in June 2012. ComEd is permitted to recover its renewable energy and REC costs from retail customers with no mark-up. The commitments represent the maximum settlements with suppliers for renewable energy and RECs under the existing contract terms. (c) PECO entered into various contracts for the procurement of electric supply to serve its default service customers that expire between 2015 and 2017. PECO is permitted to recover its electric supply procurement costs from default service customers with no mark-up in accordance with its PAPUC-approved DSP Programs. See Note 5 — Regulatory Matters for additional information. (d) PECO is subject to requirements related to the use of alternative energy resources established by the AEPS Act. See Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K for additional information. (e) BGE entered into various contracts for the procurement of electricity that expire between 2015 through 2017. The cost of power under these contracts is recoverable under MDPSC approved fuel clauses. See Note 3 — Regulatory Matters of the Exelon 2014 10-K for additional information. (f) BGE has entered into various contracts with curtailment services providers related to transactions in PJM’s capacity market. See Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K for additional information.
Fuel Purchase Commitments	As of June 30, 2015 , these net commitments were as follows: Expiration within Total 2015 2016 2017 2018 2019 2020 and beyond Generation $ 8,884 $ 726 $ 1,129 $ 1,078 $ 969 $ 880 $ 4,102 PECO 375 65 107 66 46 20 71 BGE 622 52 103 92 69 61 245
Other Purchase Obligation	The Registrants’ other purchase obligations as of June 30, 2015 , which primarily represent commitments for services, materials and information technology, are as follows: Expiration within Total 2015 2016 2017 2018 2019 2020 and beyond Exelon $ 1,422 $ 342 $ 421 $ 220 $ 77 $ 80 $ 282 Generation (a) 339 79 95 46 33 24 62 ComEd (b) 356 153 166 8 7 7 15 PECO (b) 21 5 5 2 2 2 5 BGE (b) 302 75 116 111 — — — _____________________ (a) Purchase obligations do not include commitments related to construction contracts. See Construction Commitments section below for additional information. (b) Purchase obligations include commitments related to smart meter installation. See Note 5 — Regulatory Matters for additional information.
Commercial Commitments	The Registrants’ commercial commitments as of June 30, 2015 , representing commitments potentially triggered by future events were as follows: Exelon Generation ComEd PECO BGE Letters of credit (non-debt) (a) $ 1,568 $ 1,502 $ 18 $ 22 $ 1 Guarantees 5,824 (b) 3,115 (c) 203 (d) 188 (e) 263 (f) Nuclear insurance premiums (g) 3,057 3,057 — — — Underwriters discount (h) 60 — — — — Total commercial commitments $ 10,509 $ 7,674 $ 221 $ 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 $674 million at June 30, 2015 , which represents the total amount Exelon could be required to fund based on June 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 $460 million at June 30, 2015 , which represents the total amount Generation could be required to fund based on June 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. (h) Represents the underwriters discount for Exelon’s forward equity transaction. See Note 17 — Common Stock for further details of the equity securities offering.
Accrued environmental liabilities	As of June 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: June 30, 2015 Total Environmental Investigation and Remediation Reserve Portion of Total Related to MGP Investigation and Remediation Exelon $ 337 $ 267 Generation 63 — ComEd 227 224 PECO 44 41 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 June 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 $ 77 2016 254 2017 23 2018 7 2019 2 Total $ 363

Supplemental Financial Inform43

Supplemental Financial Information (Tables)	6 Months Ended
	Jun. 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 six months ended June 30, 2015 and 2014 : Three Months Ended June 30, 2015 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 93 $ 93 $ — $ — $ — Non-regulatory agreement units 74 74 — — — Net unrealized losses on decommissioning trust funds Regulatory agreement units (133 ) (133 ) — — — Non-regulatory agreement units (96 ) (96 ) — — — Regulatory offset to decommissioning trust fund-related activities (b) 28 28 — — — Total decommissioning-related activities (34 ) (34 ) — — — Investment income (expense) 1 — — (1 ) 1 (c) Long-term lease income 4 — — — — AFUDC — Equity 5 — 1 1 3 Other 7 3 4 1 — Other, net $ (17 ) $ (31 ) $ 5 $ 1 $ 4 Six Months Ended June 30, 2015 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 164 $ 164 $ — $ — $ — Non-regulatory agreement units 104 104 — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units (85 ) (85 ) — — — Non-regulatory agreement units (56 ) (56 ) — — — Net unrealized gains on pledged assets Zion Station decommissioning 9 9 — — — Regulatory offset to decommissioning trust fund-related activities (b) (78 ) (78 ) — — — Total decommissioning-related activities 58 58 — — — Investment income (expense) 4 1 — (1 ) 2 (c) Long-term lease income 8 — — — — Interest income related to uncertain income tax positions — 1 — — — AFUDC — Equity 11 — 1 3 7 Terminated interest rate swaps (d) (26 ) — — — — Other 9 2 8 1 (1 ) Other, net $ 64 $ 62 $ 9 $ 3 $ 8 Three Months Ended June 30, 2014 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 68 $ 68 $ — $ — $ — Non-regulatory agreement units 38 38 — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 172 172 — — — Non-regulatory agreement units 128 128 — — — Net unrealized losses on pledged assets Zion Station decommissioning 10 10 — — — Regulatory offset to decommissioning trust fund-related activities (b) (204 ) (204 ) — — — Total decommissioning-related activities 212 212 — — — Investment income (expense) 7 7 — (1 ) 2 (c) Long-term lease income 10 — — — — Interest income related to uncertain income tax positions (2 ) 3 AFUDC — Equity 4 — — 1 3 Other (1 ) (6 ) 5 1 — Other, net $ 230 $ 216 $ 5 $ 1 $ 5 Six Months Ended June 30, 2014 Exelon Generation ComEd PECO BGE Other, Net Decommissioning-related activities: Net realized income on decommissioning trust funds (a) Regulatory agreement units $ 111 $ 111 $ — $ — $ — Non-regulatory agreement units 63 63 — — — Net unrealized gains on decommissioning trust funds Regulatory agreement units 234 234 — — — Non-regulatory agreement units 141 141 — — — Net unrealized losses on pledged assets Zion Station decommissioning 20 20 — — — Regulatory offset to decommissioning trust fund-related activities (b) (299 ) (299 ) — — — Total decommissioning-related activities 270 270 — — — Investment income (expense) 8 8 — (1 ) 4 (c) Long-term lease income 17 — — — — Interest income related to uncertain income tax positions 7 17 — — — AFUDC — Equity 12 — 3 3 6 Other 16 5 7 1 (1 ) Other, net $ 330 $ 300 $ 10 $ 3 $ 9 ________ (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 six months ended June 30, 2015 and 2014 : Six Months Ended June 30, 2015 Exelon Generation ComEd PECO BGE Depreciation, amortization, accretion and depletion Property, plant and equipment $ 1,087 $ 485 $ 312 $ 119 $ 143 Regulatory assets 101 — 40 12 49 Amortization of intangible assets, net 24 24 — — — Amortization of energy contract assets and liabilities (a) — 1 — — — Nuclear fuel (b) 552 552 — — — ARO accretion (c) 193 193 — — — Total depreciation, amortization, accretion and depletion $ 1,957 $ 1,255 $ 352 $ 131 $ 192 Six Months Ended June 30, 2014 Exelon Generation ComEd PECO BGE Depreciation, amortization, accretion and depletion Property, plant and equipment $ 1,015 $ 444 $ 290 $ 112 $ 142 Regulatory assets 117 — 57 5 55 Amortization of intangible assets, net 22 22 — — — Amortization of energy contract assets and liabilities (a) 113 118 — — — Nuclear fuel (b) 499 499 — — — ARO accretion (c) 159 159 — — — Total depreciation, amortization, accretion and depletion $ 1,925 $ 1,242 $ 347 $ 117 $ 197 _________ (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. Six Months Ended June 30, 2015 Exelon Generation ComEd PECO BGE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 317 $ 133 $ 103 $ 19 $ 33 Loss from equity method investments 2 3 — — — Provision for uncollectible accounts 80 11 35 24 11 Stock-based compensation costs 79 — — — — Other decommissioning-related activity (a) (50 ) (50 ) — — — Energy-related options (b) 27 27 — — — Amortization of regulatory asset related to debt costs — — — — — Amortization of rate stabilization deferral 40 — — — 40 Amortization of debt fair value adjustment (37 ) (6 ) — — — Discrete impacts of EIMA (c) 77 — 77 — — Amortization of debt costs 35 8 2 1 1 Lower of cost or market inventory adjustment 13 13 — — — Other (4 ) (5 ) 5 1 (9 ) Total other non-cash operating activities $ 579 $ 134 $ 222 $ 45 $ 76 Changes in other assets and liabilities: Under/over-recovered energy and transmission costs $ 45 $ — $ 10 $ 27 $ 8 Other regulatory assets and liabilities 47 — 26 (13 ) (18 ) Cash deposits (d) 242 242 — — — Other current assets (53 ) (39 ) 3 (74 ) (e) 60 Other noncurrent assets and liabilities (67 ) — (14 ) — 1 Total changes in other assets and liabilities $ 214 $ 203 $ 25 $ (60 ) $ 51 Non-cash investing and financing activities: Indemnification of like-kind exchange position (f) $ — $ — $ 3 $ — $ — Long-term software licensing agreement (g) 95 — — — — Total non-cash investing and financing activities: $ 95 $ — $ 3 $ — $ —
Cash Flow Supplemental Disclosures	Six Months Ended June 30, 2015 Exelon Generation ComEd PECO BGE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 317 $ 133 $ 103 $ 19 $ 33 Loss from equity method investments 2 3 — — — Provision for uncollectible accounts 80 11 35 24 11 Stock-based compensation costs 79 — — — — Other decommissioning-related activity (a) (50 ) (50 ) — — — Energy-related options (b) 27 27 — — — Amortization of regulatory asset related to debt costs — — — — — Amortization of rate stabilization deferral 40 — — — 40 Amortization of debt fair value adjustment (37 ) (6 ) — — — Discrete impacts of EIMA (c) 77 — 77 — — Amortization of debt costs 35 8 2 1 1 Lower of cost or market inventory adjustment 13 13 — — — Other (4 ) (5 ) 5 1 (9 ) Total other non-cash operating activities $ 579 $ 134 $ 222 $ 45 $ 76 Changes in other assets and liabilities: Under/over-recovered energy and transmission costs $ 45 $ — $ 10 $ 27 $ 8 Other regulatory assets and liabilities 47 — 26 (13 ) (18 ) Cash deposits (d) 242 242 — — — Other current assets (53 ) (39 ) 3 (74 ) (e) 60 Other noncurrent assets and liabilities (67 ) — (14 ) — 1 Total changes in other assets and liabilities $ 214 $ 203 $ 25 $ (60 ) $ 51 Non-cash investing and financing activities: Indemnification of like-kind exchange position (f) $ — $ — $ 3 $ — $ — Long-term software licensing agreement (g) 95 — — — — Total non-cash investing and financing activities: $ 95 $ — $ 3 $ — $ — Six Months Ended June 30, 2014 Exelon Generation ComEd PECO BGE Other non-cash operating activities: Pension and non-pension postretirement benefit costs $ 315 $ 139 $ 96 $ 21 $ 33 Equity method investments 20 20 — — — Provision for uncollectible accounts 59 8 (8 ) 28 30 Stock-based compensation costs 68 — — — — Other decommissioning-related activity (a) (85 ) (85 ) — — — Energy-related options (b) 63 63 — — — Amortization of rate stabilization deferral 33 — — — 33 Amortization of debt fair value adjustment (26 ) (12 ) — — — Discrete impacts from EIMA (c) 9 — 9 — — Amortization of debt costs 19 6 (3 ) 1 1 Other (2 ) — 5 — (8 ) Total other non-cash operating activities $ 473 $ 139 $ 99 $ 50 $ 89 Changes in other assets and liabilities: Under/over-recovered energy and transmission costs $ 60 $ — $ 61 $ (6 ) $ 8 Other regulatory assets and liabilities (25 ) — (30 ) (13 ) (49 ) Other current assets (157 ) 13 (5 ) (89 ) (e) 51 Other noncurrent assets and liabilities (158 ) (69 ) 22 (6 ) (2 ) Total changes in other assets and liabilities $ (280 ) $ (56 ) $ 48 $ (114 ) $ 8 Non-cash investing and financing activities: Fair value of net assets recorded upon CENG consolidation $ 3,400 $ 3,400 $ — $ — $ — Issuance of equity units 131 — — — — Uranium procurement 38 38 — — — Indemnification of like-kind exchange position (f) — — 2 — — Total non-cash investing and financing activities $ 3,569 $ 3,438 $ 2 $ — $ — ____________ (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 recalled from ISOs/RTOs and replaced with letters of credit. (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 June 30, 2015 and December 31, 2014 . June 30, 2015 Exelon Generation ComEd PECO BGE Property, plant and equipment: Accumulated depreciation and amortization $ 15,553 (a) $ 8,146 (a) $ 3,571 $ 3,028 $ 2,928 Accounts receivable: Allowance for uncollectible accounts 323 (c) 67 95 101 (c) 60 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 $2,804 million . (b) Includes accumulated amortization of nuclear fuel in the reactor core of $2,673 million . (c) Includes an allowance for uncollectible accounts of $9 million and $7 million at June 30, 2015 and December 31, 2014 , respectively, related to PECO's current installment plan receivables described below.

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2015
Segment Reporting Information [Line Items]
Analysis and reconciliation of reportable segment information	Six Months Ended June 30, 2015 and 2014 Generation (a) ComEd PECO BGE Other (b) Intersegment Eliminations Exelon Total revenues (c) : 2015 $ 10,074 $ 2,333 $ 1,646 $ 1,664 $ 657 $ (1,029 ) $ 15,345 2014 8,179 2,262 1,649 1,707 619 (1,155 ) 13,261 Intersegment revenues (d) : 2015 $ 362 $ 2 $ 1 $ 8 $ 656 $ (1,026 ) $ 3 2014 517 1 1 18 618 (1,155 ) — Net income (loss): 2015 $ 875 $ 189 $ 209 $ 157 $ (55 ) $ (3 ) $ 1,372 2014 188 209 173 106 (25 ) — 651 __________ (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 six months ended June 30, 2015 include revenue from sales to PECO of $ 112 million and sales to BGE of $ 235 million in the Mid-Atlantic region, and sales to ComEd of $ 15 million in the Midwest. For the six months ended June 30, 2014 , intersegment revenues for Generation include revenue from sales to PECO of $ 137 million and sales to BGE of $ 207 million in the Mid-Atlantic region, and sales to ComEd of $ 173 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 six months ended June 30, 2015 and 2014 , utility taxes of $ 51 million and $ 45 million , respectively, are included in revenues and expenses for Generation. For the six months ended June 30, 2015 and 2014 , utility taxes of $ 117 million and $ 119 million , respectively, are included in revenues and expenses for ComEd. For the six months ended June 30, 2015 and 2014 , utility taxes of $ 67 million and $ 65 million , respectively, are included in revenues and expenses for PECO. For the six months ended June 30, 2015 and 2014 , utility taxes of $ 44 million and $ 43 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 June 30, 2015 and 2014 Generation (a) ComEd PECO BGE Other (b) Intersegment Eliminations Exelon Total revenues (c) : 2015 $ 4,232 $ 1,148 $ 661 $ 628 $ 340 $ (495 ) $ 6,514 2014 3,789 1,128 656 653 329 (531 ) 6,024 Intersegment revenues (d) : 2015 $ 152 $ 1 $ — $ 1 $ 340 $ (493 ) $ 1 2014 201 — — 2 328 (531 ) — Net income (loss): 2015 $ 390 $ 99 $ 70 $ 47 $ 28 $ (1 ) $ 633 2014 372 111 84 19 (29 ) — 557 Total assets: June 30, 2015 $ 45,125 $ 25,961 $ 10,126 $ 8,017 $ 14,526 $ (11,542 ) $ 92,213 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 June 30, 2015 include revenue from sales to PECO of $49 million and sales to BGE of $97 million in the Mid-Atlantic region, and sales to ComEd of $6 million in the Midwest. For the three months ended June 30, 2014 , intersegment revenues for Generation include revenue from sales to PECO of $49 million and sales to BGE of $87 million in the Mid-Atlantic region, and sales to ComEd of $65 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 June 30, 2015 and 2014 , utility taxes of $24 million and $21 million , respectively, are included in revenues and expenses for Generation. For the three months ended June 30, 2015 and 2014 , utility taxes of $55 million and $56 million , respectively, are included in revenues and expenses for ComEd. For the three months ended June 30, 2015 and 2014 , utility taxes of $32 million and $30 million , respectively, are included in revenues and expenses for PECO. For the three months ended June 30, 2015 and 2014 , utility taxes of $21 million and $19 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	Six Months Ended June 30, 2015 Six Months Ended June 30, 2014 RNF from External Customers (b) Intersegment RNF Total RNF RNF from External Customers (b) Intersegment RNF Total RNF Mid-Atlantic (a) $ 1,659 $ 12 $ 1,671 $ 1,690 $ (75 ) $ 1,615 Midwest 1,446 (3 ) 1,443 1,134 27 1,161 New England 271 (25 ) 246 242 (42 ) 200 New York (a) 313 19 332 113 14 127 ERCOT 179 (54 ) 125 272 (130 ) 142 Other Power Regions (c) 233 (125 ) 108 307 (127 ) 180 Total Revenues net of purchased power and fuel expense for Reportable Segments 4,101 — (176 ) 3,925 3,758 (333 ) 3,425 Other (d) 691 176 867 (770 ) 333 (437 ) Total Generation Revenues net of purchased power and fuel expense $ 4,792 — $ — $ 4,792 $ 2,988 $ — $ 2,988 __________ (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 $24 million increase to RNF and a $92 million decrease to RNF for the amortization of intangible assets related to commodity contracts for the six months ended June 30, 2015 and 2014 , respectively, unrealized mark-to-market gains of $397 million and losses of $744 million for the six months ended June 30, 2015 and 2014 , respectively, and the elimination of intersegment revenue net of purchased power and fuel expense. Six Months Ended June 30, 2015 Six Months Ended June 30, 2014 Revenues (b) Intersegment Total Revenues (b) Intersegment Total Mid-Atlantic (a) $ 2,853 $ 6 $ 2,859 $ 2,713 $ (18 ) $ 2,695 Midwest 2,480 2 2,482 2,239 12 2,251 New England 1,224 2 1,226 756 5 761 New York (a) 532 (4 ) 528 384 (3 ) 381 ERCOT 376 (4 ) 372 441 (1 ) 440 Other Power Regions (c) 506 (3 ) 503 648 1 649 Total Revenues for Reportable Segments 7,971 (1 ) 7,970 7,181 (4 ) 7,177 Other (d) 2,103 1 2,104 998 4 1,002 Total Generation Consolidated Operating Revenues $ 10,074 $ — $ 10,074 $ 8,179 $ — $ 8,179 __________ (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 $22 million increase to revenues and a $180 million decrease to revenues for the amortization of intangible assets related to commodity contracts for the six months ended June 30, 2015 and 2014 , respectively, unrealized mark-to-market gains of $179 million and losses of $843 million for the six months ended June 30, 2015 and 2014 , respectively, and elimination of intersegment revenues. Generation total revenues net of purchased power and fuel expense: Three Months Ended June 30, 2015 Three Months Ended June 30, 2014 RNF (a) Intersegment RNF Total RNF RNF (a) Intersegment RNF Total RNF Mid-Atlantic $ 875 $ 14 $ 889 $ 906 $ 14 $ 920 Midwest 745 (2 ) 743 604 1 605 New England 94 (6 ) 88 88 (24 ) 64 New York 139 5 144 142 6 148 ERCOT 91 (21 ) 70 117 (58 ) 59 Other Power Regions (b) 134 (72 ) 62 157 (82 ) 75 Total Revenues net of purchased power and fuel for Reportable Segments 2,078 (82 ) 1,996 2,014 (143 ) 1,871 Other (c) 305 82 387 (60 ) 143 83 Total Generation Revenues net of purchased power and fuel expense $ 2,383 $ — $ 2,383 $ 1,954 $ — $ 1,954 __________ (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 $14 million decrease to RNF and a $50 million decrease to RNF for the amortization of intangible assets related to commodity contracts for the three months ended June 30, 2015 and 2014 , respectively, unrealized mark-to-market gains of $235 million and losses of $14 million for the three months ended June 30, 2015 and 2014 , respectively, and the elimination of intersegment revenues. Generation total revenues: Three Months Ended June 30, 2015 Three Months Ended June 30, 2014 Revenues from External Customers (a) Intersegment Revenues Total Revenues Revenues from External Customers (a) Intersegment Revenues Total Revenues Mid-Atlantic $ 1,336 $ 10 $ 1,346 $ 1,272 $ 5 $ 1,277 Midwest 1,205 1 1,206 981 — 981 New England 366 1 367 211 1 212 New York 222 (4 ) 218 194 — 194 ERCOT 194 (2 ) 192 198 (1 ) 197 Other Power Regions (b) 294 (5 ) 289 314 (6 ) 308 Total Revenues for Reportable Segments 3,617 1 3,618 3,170 (1 ) 3,169 Other (c) 615 (1 ) 614 619 1 620 Total Generation Consolidated Operating Revenues $ 4,232 $ — $ 4,232 $ 3,789 $ — $ 3,789 __________ (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 $17 million decrease to revenues and an $88 million decrease to revenues for the amortization of intangible assets related to commodity contracts for the three months ended June 30, 2015 and 2014 , respectively, unrealized mark-to-market gains of $25 million and losses of $83 million for the three months ended June 30, 2015 and 2014 , respectively, and the elimination of intersegment revenues.

Basis of Presentation - Narrati

Basis of Presentation - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total interest expense to affiliates, net	$ 10	$ 10	$ 21	$ 20
Pretax decrease in operating and maintenance expense	(2,042)	(2,166)	(4,123)	(4,024)
Pretax increase in taxes other than income	294	288	598	580
Income (Loss) from Equity Method Investments	0	0	(2)	(20)
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions	(2)	0	(2)	0
Exelon Generation Co L L C [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Purchased power and fuel from affiliates	1	69	8	417
Total interest expense to affiliates, net	9	12	21	25
Pretax decrease in operating and maintenance expense	(1,149)	(1,255)	(2,311)	(2,194)
Pretax increase in taxes other than income	124	118	246	223
Income (Loss) from Equity Method Investments		(1)	(3)	(20)
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions	(2)		(3)
Baltimore Gas and Electric Company [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total interest expense to affiliates, net	4	4	8	8
Purchased power and fuel	143	183	493	592
Pretax decrease in operating and maintenance expense	(120)	(163)	(276)	(326)
Pretax increase in taxes other than income	$ 54	$ 53	$ 111	113
Income (Loss) from Equity Method Investments				$ 0

Variable Interest Entities - Na

Variable Interest Entities - Narrative (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2015USD ($)VIE	Jun. 30, 2014USD ($)	Jun. 30, 2015USD ($)VIE	Jun. 30, 2014USD ($)	Jun. 09, 2015USD ($)	Dec. 31, 2014USD ($)VIE	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	10,509,000,000		10,509,000,000
Note Receivable			$ 27,000,000
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage									50.01%
Related Party Transaction Required Purchase Of Power Percentage			85.00%
Guarantor Obligations, Current Carrying Value	8,000,000		$ 8,000,000
Related Party Purchase Of Nuclear Output By Third Party Percentage			49.99%
Payables to affiliates	98,000,000		$ 98,000,000			$ 107,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted	7,674,000,000		7,674,000,000
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	42,000,000	$ 42,000,000
Constellation Energy Nuclear Group [Member]
Variable Interest Entity [Line Items]
Severance Benefits Obligations Balance								6,000,000
Severance Costs			2,000,000
Constellation Energy Nuclear Group [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Due from Affiliates	288,000,000		288,000,000					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		Jun. 30, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Current Assets	[1]	$ 924	$ 1,271
Non Current Assets	[1]	7,731	7,580
Total Assets	[1]	8,655	8,851
Current Liabilities	[1]	378	611
Non Current Liabilities	[1]	2,860	2,730
Total Liabilities	[1]	3,238	3,341
Assets		92,213	86,814
Total liabilities	[2]	67,144	62,681
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		7,989	8,160
Total liabilities		2,555	2,723
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Current Assets		894	1,242
Non Current Assets		7,723	7,566
Total Assets		8,617	8,808
Current Liabilities		292	526
Non Current Liabilities		2,773	2,600
Total Liabilities		3,065	3,126
Assets	[3]	45,125	45,348
Total liabilities	[3]	32,469	31,297
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		7,949	8,119
Total liabilities		2,382	2,507
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Current Assets		24	21
Non Current Assets		3	3
Total Assets		27	24
Current Liabilities		79	77
Non Current Liabilities		81	120
Total Liabilities		160	197
Assets	[4]	8,017	8,078
Total liabilities	[4]	5,190	5,325
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Assets		27	24
Total liabilities		$ 159	$ 197
[1]	Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity.
[2]	Exelon’s consolidated assets include $7,989 million and $8,160 million at June 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 $2,555 million and $2,723 million at June 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 $7,949 million and $8,119 million at June 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 $2,435 million and $2,507 million at June 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 $27 million and $24 million at June 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 $160 million and $197 million at June 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		Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 6,014	$ 1,878	$ 1,362	$ 1,609
Restricted cash		274	271
Accounts receivable, net
Customer		3,227	3,482
Other		1,304	1,227
Inventory
Materials and supplies		1,068	1,024
Other current assets		654	865
Mark-to-market derivative assets (current assets)		1,405	1,279
Total current assets		15,425	12,097
Property, plant and equipment, net		53,935	52,087
Nuclear decommissioning trust funds		10,607	10,537
Goodwill		2,672	2,672
Mark-to-market derivative assets		811	773
Other noncurrent assets		1,388	1,160
Total assets		92,213	86,814
Short-term borrowings		543	460
Long-term debt due within one year		226	1,802
Accounts payable		2,727	3,048
Accrued expenses		1,366	1,539
Mark-to-market derivative liabilities (current liabilities)		165	234
Other current liabilities		141	238
Other Liabilities, Current		941	1,123
Total current liabilities		6,526	8,762
Long-term debt		25,220	19,362
Asset retirement obligations		7,550	7,295
Pension obligation(a)		3,134	3,366
Energy Marketing Contract Liabilities, Noncurrent		166	211
Other noncurrent liabilities		2,528	2,147
Total deferred credits and other liabilities		34,750	33,909
Total liabilities	[1]	67,144	62,681
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		240	392
Restricted cash		145	117
Accounts receivable, net
Customer		179	297
Other		29	57
Inventory
Materials and supplies		178	172
Other current assets		32	33
Mark-to-market derivative assets (current assets)		96	171
Total current assets		899	1,239
Property, plant and equipment, net		4,811	4,638
Nuclear decommissioning trust funds		2,096	2,097
Goodwill		47	47
Mark-to-market derivative assets		45	44
Other noncurrent assets		91	95
Total noncurrent assets		7,090	6,921
Total assets		7,989	8,160
Long-term debt due within one year		88	87
Accounts payable		143	292
Accrued expenses		87	111
Mark-to-market derivative liabilities (current liabilities)		8	24
Other current liabilities		9	22
Other Liabilities, Current		13	25
Total current liabilities		348	561
Long-term debt		166	212
Asset retirement obligations		1,865	1,763
Pension obligation(a)	[2]	9	9
Energy Marketing Contract Liabilities, Noncurrent		45	51
Other noncurrent liabilities		122	127
Total deferred credits and other liabilities		2,207	2,162
Total liabilities		2,555	2,723
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		456	780	305	1,258
Restricted cash		174	158
Accounts receivable, net
Customer		2,045	2,295
Other		299	318
Inventory
Materials and supplies		860	847
Other current assets		451	658
Mark-to-market derivative assets (current assets)		1,405	1,276
Total current assets		6,443	7,638
Property, plant and equipment, net		23,766	22,945
Nuclear decommissioning trust funds		10,607	10,537
Goodwill		47	47
Mark-to-market derivative assets		790	771
Other noncurrent assets		798	731
Total assets	[3]	45,125	45,348
Short-term borrowings		40	36
Long-term debt due within one year		89	58
Accounts payable		1,528	1,759
Accrued expenses		732	886
Mark-to-market derivative liabilities (current liabilities)		145	214
Other current liabilities		141	238
Other Liabilities, Current		453	605
Total current liabilities		3,864	4,459
Long-term debt		7,974	6,709
Asset retirement obligations		7,399	7,146
Energy Marketing Contract Liabilities, Noncurrent		166	211
Other noncurrent liabilities		817	719
Total deferred credits and other liabilities		19,693	19,186
Total liabilities	[3]	32,469	31,297
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		240	392
Restricted cash		121	96
Accounts receivable, net
Customer		179	297
Other		29	57
Inventory
Materials and supplies		178	172
Other current assets		25	26
Mark-to-market derivative assets (current assets)		96	171
Total current assets		868	1,211
Property, plant and equipment, net		4,811	4,638
Nuclear decommissioning trust funds		2,096	2,097
Goodwill		47	47
Mark-to-market derivative assets		45	44
Other noncurrent assets		82	82
Total noncurrent assets		7,081	6,908
Total assets		7,949	8,119
Long-term debt due within one year		5	5
Accounts payable		143	292
Accrued expenses		84	108
Mark-to-market derivative liabilities (current liabilities)		8	24
Other current liabilities		9	22
Other Liabilities, Current		13	25
Total current liabilities		262	476
Long-term debt		79	81
Asset retirement obligations		1,865	1,763
Pension obligation(a)	[2]	9	9
Energy Marketing Contract Liabilities, Noncurrent		45	51
Other noncurrent liabilities		122	127
Total deferred credits and other liabilities		2,120	2,031
Total liabilities		2,382	2,507
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		24	64	$ 15	$ 31
Restricted cash		29	50
Accounts receivable, net
Customer		360	390
Other		76	82
Inventory
Materials and supplies		35	30
Other current assets		4	5
Total current assets		776	957
Property, plant and equipment, net		6,373	6,204
Other noncurrent assets		25	25
Total assets	[4]	8,017	8,078
Short-term borrowings		0	120
Long-term debt due within one year		77	75
Accounts payable		194	215
Accrued expenses		108	131
Other Liabilities, Current		33	51
Total current liabilities		700	846
Long-term debt		1,828	1,867
Asset retirement obligations		18	17
Other noncurrent liabilities		62	60
Total deferred credits and other liabilities		2,404	2,354
Total liabilities	[4]	5,190	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		24	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		24	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		27	24
Long-term debt due within one year		77	75
Accounts payable		0	0
Accrued expenses		1	2
Mark-to-market derivative liabilities (current liabilities)		0	0
Other current liabilities		0	0
Other Liabilities, Current		0	0
Total current liabilities		78	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		$ 159	$ 197
[1]	Exelon’s consolidated assets include $7,989 million and $8,160 million at June 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 $2,555 million and $2,723 million at June 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 $7,949 million and $8,119 million at June 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 $2,435 million and $2,507 million at June 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 $27 million and $24 million at June 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 $160 million and $197 million at June 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		Jun. 30, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Total assets	[1]	$ 387	$ 205
Total liabilities	[1]	90	52
Exelon's ownership interest in VIE	[1]	16	9
Other ownership interests in VIE	[1]	282	144
Assets Held-in-trust, Noncurrent		264	319
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	260	114
Total liabilities	[1]	29	3
Exelon's ownership interest in VIE	[1]	0	0
Other ownership interests in VIE	[1]	231	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]	127	91
Total liabilities	[1]	61	49
Exelon's ownership interest in VIE	[1]	16	9
Other ownership interests in VIE	[1]	51	33
Investments [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		19	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		19	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]	23	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]	23	27
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Assets Held-in-trust, Noncurrent		264	319
Payable to Zion Solutions	[3]	$ 241	$ 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 $264 million and $319 million as of June 30, 2015 and December 31, 2014, respectively; offset by payables to ZionSolutions, LLC of $241 million and $292 million as of June 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	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Jul. 18, 2014	Jun. 11, 2014	May. 01, 2014	Mar. 31, 2014
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross				$ 28	$ 66
Business Combination, Integration Related Costs				$ 89
Temporary Equity, Share Subscriptions			57.5	57.5				57.5
Line of Credit Facility, Maximum Borrowing Capacity	[1]		$ 8,500	$ 8,500
Bridge Loan									$ 7,200
Other noncurrent assets			1,388	1,388		$ 1,160
Business Acquisition, Preacquisition Contingency, Amount of Settlement			300	300
Business Combination, Separately Recognized Transactions, Expenses and Losses Recognized				205
Proceeds from Issuance of Common Stock			1,870
Pepco Holdings [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Transaction Costs								$ 116
Temporary Equity, Share Subscriptions								23
Line of Credit Facility, Maximum Borrowing Capacity								$ 7,200
Cash offered in exchange for each share of PHI stock						$ 35	$ 27.25
Other Long-term Investments							$ 18
Other noncurrent assets			162	162
Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds				7,200
Business Acquisition, Preacquisition Contingency, Amount of Settlement			66	66
Pepco Holdings [Member] | Workforce Development [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Customer Loyalty Program Liability, Noncurrent			14.4	14.4
Pepco Holdings [Member] | Energy Efficiency Program [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Customer Loyalty Program Liability, Noncurrent			43.2	43.2
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
Delmarva Power & Light [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Business Acquisition, Preacquisition Contingency, Amount of Settlement			40	40
Delmarva Power & Light [Member] | Workforce Development [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Customer Loyalty Program Liability, Noncurrent			2	2
Delmarva Power & Light [Member] | Energy Efficiency Program [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Customer Loyalty Program Liability, Noncurrent			2	2
Exelon Generation Co L L C [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Payments to Acquire Businesses, Gross				28	66
Equity Method Investment, Ownership Percentage										50.01%
Other noncurrent assets			$ 798	$ 798		731
Debt Instrument, Face Amount					$ 3,200
Proceeds from Sale of Productive Assets		$ 1,800
Junior Subordinated Debt [Member] | Pepco Holdings [Member]
Payments to Acquire Businesses and Interest in Affiliates [Abstract]
Subordinated Debt, Amount						$ 1,200
[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 expire on October 16, 2015. These facilities are solely utilized to issue letters of credit. As of June 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	Jun. 30, 2015	Dec. 31, 2014
Assets Disposition Table [Line Items]
Total assets held for sale		$ 1	$ 147
Accrued expenses		1,366	1,539
Other current liabilities		941	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		1	147
Accrued expenses		732	886
Other current liabilities		$ 453	$ 605
Proceed from sale of asset net of tax	$ 1,400

Regulatory Matters - Narrative

Regulatory Matters - Narrative (Details) - Regulatory Asset [Domain] $ in Millions		Oct. 20, 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 ($)	Jun. 30, 2015USD ($)	Dec. 31, 2014USD ($)	Jun. 11, 2014	Jun. 03, 2014USD ($)	Apr. 28, 2014	Aug. 23, 2013USD ($)	May. 17, 2013USD ($)
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													$ 6,761	$ 6,923
Rate of Return on Common Equity, Incentive Basis Points													0.50%
Regulatory assets													$ 5,976	6,076
Transmission Rate Formula, First Basis Points Credited													0.50%
Business Combination, Integration Related Costs													$ 89
Regulatory Liabilities													4,871	4,860
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													$ 1,110	1,201
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													1,200,000
Regulatory assets													$ 834	$ 852
Rate Of Return On Common Equity						11.50%
Regulatory Liabilities													3,776	3,780
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													1,594	1,558
Spend on smart grid investments													$ 155
Public Utilities, Requested Rate Increase (Decrease), Amount							$ 190
Requested ROE							10.95%
Public Utilities, Requested Rate Increase (Decrease), Percentage							4.40%
TotalSmartMetersInstalled													1,700,000
SmartMeterFundingSGIG													$ 200
Smart meter spend to date													574
Smart grid infrastructure spend to date													155
Total smart grid and smart meter investment grant amount													591
Regulatory assets													1,552	1,529
Amount of Regulatory Costs Not yet Approved													534
Regulatory Liabilities													750	747
Total Projected Natural Gas LTIIP Spend			$ 275
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													693	724
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													486	510
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%
Regulatory Liabilities													276	244
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
License Costs													42
Other Commitment													3.5
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													275	371
Under Recovered Distribution Service Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[1]												275	371
CostRecoveryForSignificantOneTimeEvents													66	85
UnderOverRecoveredDistributionServiceCosts													209	286
Business Combination, Integration Related Costs													15	19
RegulatoryAssetsDueToDeferredStormCosts													51	66
Under Recovered Distribution Service Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													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
AMI Expenses [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													349	296
AMI Expenses [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													119	91
AMI Expenses [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													70	77
AMI Expenses [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													160	128
Energy Efficiency And Demand Response Programs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													236	248
Energy Efficiency And Demand Response Programs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													0	0
Energy Efficiency And Demand Response Programs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													0	0
Energy Efficiency And Demand Response Programs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													236	248
Transmission Rate Formula [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Net regulatory asset													26	21
Net Regulatory Asset													26	21
Transmission Rate Formula [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Net regulatory asset													1
Net Regulatory Asset													1
Distribution formula Rate [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Net Regulatory Assets													275	371
Under Recovered Energy And Transmission Costs [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets													53	48
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[2]												34	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
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Assets	[3]												19	15
Business Combination, Integration Related Costs													4	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
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	84
Over Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities	[2]												30	19
Over Recovered Energy And Transmission Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities	[4]												85	58
Over Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Regulatory Liabilities	[3]												$ 19	$ 7
[1]	As of June 30, 2015, ComEd’s regulatory asset of $275 million was comprised of $209 million for the applicable annual reconciliations and $66 million related to significant one-time events including $51 million of deferred storm costs and $15 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 June 30, 2015, ComEd’s regulatory asset of $34 million included $1 million related to under-recovered energy costs for non-hourly customers, $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 June 30, 2015, ComEd’s regulatory liability of $30 million included $10 million related to over-recovered energy costs for hourly customers and $20 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 June 30, 2015, BGE's regulatory asset of $19 million included $1 million associated with transmission costs recoverable through its FERC approved formula rate and $18 million related to under-recovered electric energy costs. As of June 30, 2015, BGE's regulatory liability of $19 million related to $18 million of over-recovered natural gas supply costs and $6 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]	ncluded $35 million related to the DSP program, $44 million related to the over-recovered natural gas costs under the PGC, $5 million related to over-recovered electric transmission costs and $1 million related to the Non-Bypassable service charge included in the DSP program. 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		6 Months Ended	12 Months Ended
		Jun. 30, 2015	Dec. 31, 2014
Regulatory Assets [Line Items]
Current		$ 785	$ 847
Noncurrent		5,976	6,076
Regulatory Assets		6,761	6,923
Business Combination, Integration Related Costs		89
Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		3,193	3,256
Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,574	1,542
AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		349	296
Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		275	371
Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		51	57
Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		177	190
Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11	12
Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		121	116
Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		245	257
Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		50	67
Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		223	207
Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		53	48
Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	3
Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		25	30
Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		121	160
Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		236	248
Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7	8
ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	2
Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		46	46
Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7
Commonwealth Edison Co [Member]
Regulatory Assets [Line Items]
Current		276	349
Noncurrent		834	852
Regulatory Assets		1,110	1,201
Commonwealth Edison Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		65	64
Commonwealth Edison Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		119	91
Commonwealth Edison Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[1]	275	371
UnderOverRecoveredDistributionServiceCosts		209	286
CostRecoveryForSignificantOneTimeEvents		66	85
RegulatoryAssetsDueToDeferredStormCosts		51	66
Business Combination, Integration Related Costs		15	19
Commonwealth Edison Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		49	53
Commonwealth Edison Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		76	74
Commonwealth Edison Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		210	219
Commonwealth Edison Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		50	67
Commonwealth Edison Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		223	207
Commonwealth Edison Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[2]	34	33
Business Combination, Integration Related Costs		7	7
ElectricTransmissionCostsUnderRecovery		26	22
Underrecovered Electric Supply cost		1	4
Commonwealth Edison Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Commonwealth Edison Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		9	22
Commonwealth Edison Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0
PECO Energy Co [Member]
Regulatory Assets [Line Items]
Current		42	29
Noncurrent		1,552	1,529
Regulatory Assets		1,594	1,558
PECO Energy Co [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1,432	1,400
PECO Energy Co [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		70	77
PECO Energy Co [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	4
PECO Energy Co [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		26	26
PECO Energy Co [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		34	37
PECO Energy Co [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
PECO Energy Co [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		30	14
PECO Energy Co [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			0
Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Current		207	214
Noncurrent		486	510
Regulatory Assets		693	724
Baltimore Gas and Electric Company [Member] | Other Postretirement Benefits [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Baltimore Gas and Electric Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory Assets		77	78
Baltimore Gas and Electric Company [Member] | AMI Expenses [Member]
Regulatory Assets [Line Items]
Regulatory Assets		160	128
Baltimore Gas and Electric Company [Member] | Under Recovered Distribution Service Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Baltimore Gas and Electric Company [Member] | Loss on Reacquired Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		8	9
Baltimore Gas and Electric Company [Member] | Fair Value Of Long Term Debt [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Baltimore Gas and Electric Company [Member] | Employee Severance [Member]
Regulatory Assets [Line Items]
Regulatory Assets		11	12
Baltimore Gas and Electric Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		19	16
Baltimore Gas and Electric Company [Member] | Environmental Restoration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		1	1
Baltimore Gas and Electric Company [Member] | Under Recovered Uncollectible Accounts Expense [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Baltimore Gas and Electric Company [Member] | Renewable Energy And Associated REC [Member]
Regulatory Assets [Line Items]
Regulatory Assets		0	0
Baltimore Gas and Electric Company [Member] | Under Recovered Energy And Transmission Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets	[3]	19	15
Business Combination, Integration Related Costs		4	4
Underrecovered Electric Supply cost		18	10
Environmental Restoration Costs		1	1
Baltimore Gas and Electric Company [Member] | Deferred Storm Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	3
Baltimore Gas and Electric Company [Member] | Electric Generation Related Regulatory Asset [Member]
Regulatory Assets [Line Items]
Regulatory Assets		25	30
Baltimore Gas and Electric Company [Member] | Rate Stabilization Deferral [Member]
Regulatory Assets [Line Items]
Regulatory Assets		121	160
Baltimore Gas and Electric Company [Member] | Energy Efficiency And Demand Response Programs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		236	248
Baltimore Gas and Electric Company [Member] | Merger Integration Costs [Member]
Regulatory Assets [Line Items]
Regulatory Assets		7	8
Baltimore Gas and Electric Company [Member] | ConservativeVoltageReductionProgram [Member]
Regulatory Assets [Line Items]
Regulatory Assets		2	2
Baltimore Gas and Electric Company [Member] | Regulatory Assets [Member]
Regulatory Assets [Line Items]
Regulatory Assets		5	7
Baltimore Gas and Electric Company [Member] | Under Recovered Decoupling Revenue [Member]
Regulatory Assets [Line Items]
Regulatory Assets			7
UnderRecoveredElectricRevenueDecoupling			$ 7
Over Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Assets [Line Items]
Underrecovered Electric Supply cost		$ 6
[1]	As of June 30, 2015, ComEd’s regulatory asset of $275 million was comprised of $209 million for the applicable annual reconciliations and $66 million related to significant one-time events including $51 million of deferred storm costs and $15 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 June 30, 2015, ComEd’s regulatory asset of $34 million included $1 million related to under-recovered energy costs for non-hourly customers, $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 June 30, 2015, ComEd’s regulatory liability of $30 million included $10 million related to over-recovered energy costs for hourly customers and $20 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 June 30, 2015, BGE's regulatory asset of $19 million included $1 million associated with transmission costs recoverable through its FERC approved formula rate and $18 million related to under-recovered electric energy costs. As of June 30, 2015, BGE's regulatory liability of $19 million related to $18 million of over-recovered natural gas supply costs and $6 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.

Regulatory Matters Regulatory54

Regulatory Matters Regulatory Matters - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Jun. 30, 2015	Dec. 31, 2014
Regulatory Liabilities [Line Items]
Current		$ 409	$ 310
Noncurrent		4,462	4,550
Regulatory Liabilities		4,871	4,860
Other Postretirement Benefits [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		68	88
Nuclear Decommissioning [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2,831	2,879
Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,563	1,566
Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		41	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		102	102
Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		33	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		2	2
Revenue Subject to Refund [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities			3
Over Recovered Decoupling Revenue [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		40	12
Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		10	6
Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Current		91	44
Noncurrent		185	200
Regulatory Liabilities		276	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		212	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]	19	7
Over recovered Natural Gas Supply Cost		18	7
Underrecovered Electric Supply cost		6
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]	40	12
Over Recovered Electric Revenue Decoupling		11
Over Recovered Natural Gas Revenue Decoupling		29	12
Baltimore Gas and Electric Company [Member] | Regulatory Liabilities Other [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		5	2
PECO Energy Co [Member]
Regulatory Liabilities [Line Items]
Current		117	90
Noncurrent		633	657
Regulatory Liabilities		750	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		477	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		102	102
PECO Energy Co [Member] | Gas Distribution Tax Repairs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		33	49
PECO Energy Co [Member] | Over Recovered Energy And Transmission Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities	[3]	85	58
Over recovered Natural Gas Supply Cost		44	3
Default Service Provider Program Costs		35	39
Over Recovered Electric Transmission Costs		5	16
Non Bypassable Service Charges		1
PECO Energy Co [Member] | Over-Recovered Universal Service Fund Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		2	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		2	2
Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Current		154	125
Noncurrent		3,622	3,655
Regulatory Liabilities		3,776	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		2,354	2,389
Commonwealth Edison Co [Member] | Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		1,351	1,343
Commonwealth Edison Co [Member] | Energy Efficiency Demand Response Programs [Member]
Regulatory Liabilities [Line Items]
Regulatory Liabilities		39	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	[4]	30	19
Over Recovered electric Supply Costs		10	3
Renewable Energy Requirement Revenue		20	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		2	1
Under Recovered Energy And Transmission Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Liabilities [Line Items]
Underrecovered Electric Supply cost		18	10
Under Recovered Energy And Transmission Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Liabilities [Line Items]
Underrecovered Electric Supply cost		$ 1	$ 4
[1]	As of June 30, 2015, BGE's regulatory asset of $19 million included $1 million associated with transmission costs recoverable through its FERC approved formula rate and $18 million related to under-recovered electric energy costs. As of June 30, 2015, BGE's regulatory liability of $19 million related to $18 million of over-recovered natural gas supply costs and $6 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]	Represents the electric and gas distribution costs recoverable from customers under BGE’s decoupling mechanism. As of June 30, 2015, BGE had a regulatory liability of $11 million related to over-recovered electric revenue decoupling and a regulatory liability of $29 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]	ncluded $35 million related to the DSP program, $44 million related to the over-recovered natural gas costs under the PGC, $5 million related to over-recovered electric transmission costs and $1 million related to the Non-Bypassable service charge included in the DSP program. 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]	As of June 30, 2015, ComEd’s regulatory asset of $34 million included $1 million related to under-recovered energy costs for non-hourly customers, $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 June 30, 2015, ComEd’s regulatory liability of $30 million included $10 million related to over-recovered energy costs for hourly customers and $20 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		6 Months Ended
		Jun. 30, 2015	Dec. 31, 2014
Purchase Of Receivables [Line Items]
Purchased receivables	[1]	$ 275	$ 290
Allowance for uncollectible accounts	[2]	(40)	(42)
Purchased receivables, net		235	248
Commonwealth Edison Co [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	[1]	128	139
Allowance for uncollectible accounts	[2]	(22)	(21)
Purchased receivables, net		106	118
PECO Energy Co [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	[1]	80	76
Allowance for uncollectible accounts	[2]	(8)	(8)
Purchased receivables, net		$ 72	68
Discount rate		1.00%
Baltimore Gas and Electric Company [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	[1]	$ 67	75
Allowance for uncollectible accounts	[2]	(10)	(13)
Purchased receivables, net		$ 57	$ 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. If the costs are not fully recovered when PECO files its next gas distribution rate case, PECO will propose a mechanism to recover the remaining implementation costs as a distribution charge to low volume transportation customers or apply future discounts on purchased receivables from natural gas suppliers serving those customers.
[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				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014		Jun. 09, 2015	Dec. 31, 2014	Apr. 01, 2014	Mar. 31, 2014	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		$ 10,509,000,000				$ 10,509,000,000
Revenues		6,514,000,000	[1]	$ 6,024,000,000	[1]	15,345,000,000	[2]	$ 13,261,000,000	[2]
Accumulated other comprehensive loss, net	[3]	(2,626,000,000)		(1,906,000,000)		(2,626,000,000)		(1,906,000,000)			$ (2,684,000,000)			$ (2,040,000,000)
Other Comprehensive Income (Loss), Tax		(28,000,000)		(79,000,000)		(42,000,000)		(82,000,000)
Revenue from Related Parties		1,000,000	[4]	0	[4]	3,000,000		0
Guarantor Obligations, Current Carrying Value		75,000,000				75,000,000
Business Combination, Integration Related Costs						89,000,000
Exelon Generation Co L L C [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage													50.01%
Payments of Distributions to Affiliates						$ 2,262,000,000		235,000,000
Related Party Purchase Of Nuclear Output By Third Party Percentage						49.99%
Payables to affiliates		98,000,000				$ 98,000,000					107,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted		7,674,000,000				7,674,000,000
Total equity investment earnings (losses) - CENG								19,000,000
Revenues		4,232,000,000		3,789,000,000		10,074,000,000		8,179,000,000
Accumulated other comprehensive loss, net	[3]	(47,000,000)		37,000,000		(47,000,000)		37,000,000			$ (36,000,000)			$ 214,000,000
Other Comprehensive Income (Loss), Tax		(1,000,000)		102,000,000		$ 2,000,000		112,000,000
Related Party Transaction Required Purchase Of Power Percentage						85.00%
Revenue from Related Parties		153,000,000		$ 201,000,000		$ 365,000,000		535,000,000
Guarantor Obligations, Current Carrying Value		8,000,000				8,000,000
Exelon Generation Co L L C [Member] | Constellation Energy Nuclear Group [Member]
Schedule of Equity Method Investments [Line Items]
Revenues		109,000,000				$ 306,000,000		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		288,000,000				$ 288,000,000						$ 400,000,000
Reduction To Net Income Attributable To Noncontrolling Interest		4,000,000				9,000,000
Net Income (Loss) Attributable to Parent		(4,000,000)				93,000,000
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		$ 106,000,000				$ 288,000,000
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 June 30, 2015 and 2014, utility taxes of $24 million and $21 million, respectively, are included in revenues and expenses for Generation. For the three months ended June 30, 2015 and 2014, utility taxes of $55 million and $56 million, respectively, are included in revenues and expenses for ComEd. For the three months ended June 30, 2015 and 2014, utility taxes of $32 million and $30 million, respectively, are included in revenues and expenses for PECO. For the three months ended June 30, 2015 and 2014, utility taxes of $21 million and $19 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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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	2,042	$ 2,166	4,123	4,024
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
Operating and maintenance	$ 1,149	$ 1,255	$ 2,311	$ 2,194

Impairment of Long-lived Asse58

Impairment of Long-lived Assets - Components of the Net Investment in Long-term Leases (Details) - USD ($) $ in Millions	Jun. 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	295	324
Net investment in long-term leases	$ 344	$ 361

Implications of Potential Ear59

Implications of Potential Early Plant Retirements Implications of Potential Early Plant Retirements (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	$ 1,068	$ 1,024
Property, Plant and Equipment, Net	53,935	52,087
Nuclear Plant [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	133
Nuclear Fuel, Net of Amortization	408
Property, Plant and Equipment, Net	1,350
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	71
Asset Retirement Obligation	(1,348)
Quad Cities [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	48
Nuclear Fuel, Net of Amortization	205
Property, Plant and Equipment, Net	800
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	24
Asset Retirement Obligation	(450)
Clinton [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	55
Nuclear Fuel, Net of Amortization	137
Property, Plant and Equipment, Net	465
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	24
Asset Retirement Obligation	(287)
Ginna [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	30
Nuclear Fuel, Net of Amortization	66
Property, Plant and Equipment, Net	85
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	23
Asset Retirement Obligation	(611)
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross	860	847
Property, Plant and Equipment, Net	$ 23,766	$ 22,945

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	Jun. 30, 2015	Dec. 31, 2014
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	$ 543	$ 460
Due to Related Parties, Noncurrent	648	648
Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	546	463
Long-term debt (including amounts due within one year)	25,446	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	546	463
Long-term debt (including amounts due within one year)	26,403	22,936
SNF obligation	838	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)	1,043	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	543	448
Long-term debt (including amounts due within one year)	24,011	20,417
SNF obligation	838	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)	1,349	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	40	36
Exelon Generation Co L L C [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	40	36
Long-term debt (including amounts due within one year)	9,001	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	40	36
Long-term debt (including amounts due within one year)	9,344	8,822
SNF obligation	838	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	40	24
Long-term debt (including amounts due within one year)	7,995	7,511
SNF obligation	838	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)	1,349	1,311
SNF obligation	0	0
Commonwealth Edison Co [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	503	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	503	304
Long-term debt (including amounts due within one year)	6,099	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	503	304
Long-term debt (including amounts due within one year)	6,640	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	503	304
Long-term debt (including amounts due within one year)	6,640	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)	2,432	2,537
Due to Related Parties, Noncurrent	199	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)	2,432	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	199	199
Baltimore Gas and Electric Company [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Short-term Debt	0	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	3	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	3	123
Long-term debt (including amounts due within one year)	2,086	2,178
Due to Related Parties, Noncurrent	258	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	0	120
Long-term debt (including amounts due within one year)	2,086	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	$ 258	$ 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	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	$ (595)	$ (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	36	35
Derivative Liability, Noncurrent	(595)	(403)
Derivative Liability, Current	165	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
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	5,486	1,119
FinancialAssetsFairValueDisclosure1	18,662	14,081
Deferred Compensation Liability, Current and Noncurrent	(88)	(107)
Financial Liabilities Fair Value Disclosure	(847)	(744)
FinancialAssetLiabilitiesNetFairValueDisclosure1	17,815	13,337
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	5,486	1,119
Deferred Compensation Liability, Current and Noncurrent	(88)	(107)
Financial Liabilities Fair Value Disclosure	(847)	(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	(746)	(524)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(746)	(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	(6,307)	(6,694)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6,307)	(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	(5,963)	(6,702)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,963)	(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	(13)	(113)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(13)	(113)
Fair Value, Measurements, Recurring [Member] | EconomicHedgingInstrumentLiabilites1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(4)	(103)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(4)	(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	(14)	(41)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(14)	(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	(14)	(23)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(14)	(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	(19)	(54)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(19)	(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	10,619	10,542
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10,619	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	4,444	4,630
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,444	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	696	612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	696	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	2,110	2,262
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,110	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	1,165	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,165	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	83	95
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	83	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	405	438
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	405	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	463	511
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	463	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	417	366
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	417	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	19	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	19	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	17
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	17
Fair Value, Measurements, Recurring [Member] | Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,140	5,242
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,140	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	4,226	4,302
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,226	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	388	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	388	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	100	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	100	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	277	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	5,486	1,119
FinancialAssetsFairValueDisclosure1	9,969	5,305
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	37	(9)
FinancialAssetLiabilitiesNetFairValueDisclosure1	10,006	5,296
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	5,486	1,119
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	37	(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	37	(20)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	37	(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	(1,493)	(2,241)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,493)	(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	(111)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(111)
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	(1,641)	(2,416)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,641)	(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	(14)	(14)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(14)	(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	(14)	(25)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(14)	(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	4,583	4,239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,583	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	2,389	2,423
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,389	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	696	612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	696	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	1,165	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,165	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	7	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7	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	7	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7	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	12	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	12	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	3,085	3,035
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3,085	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	1,165	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,165	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	48	47
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	48	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	333	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	333	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	167	(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	(1,080)	(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	(117)	(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	1,364	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	1	2
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1	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	543	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	(402)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(402)
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	62	89
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	62	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	9	8
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	9	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	3	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3	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	84	110
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	84	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	263	316
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	263	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	156	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	156	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	48	47
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	48	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	(2,171)	(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	(20)	(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	(44)	(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	(22)	(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	(6,766)	(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	(394)	(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	4,989	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	(15)	(27)
Fair Value, Inputs, Level 2 [Member] | EffectsofNettingandAllocationofCollateral1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	13	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	31	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	31	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	6,221	6,747
Deferred Compensation Liability, Current and Noncurrent	(88)	(107)
Financial Liabilities Fair Value Disclosure	(182)	(427)
FinancialAssetLiabilitiesNetFairValueDisclosure1	6,039	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	(88)	(107)
Financial Liabilities Fair Value Disclosure	(182)	(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	(81)	(196)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(81)	(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	(3,129)	(3,458)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(3,129)	(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	(248)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(248)
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	(3,296)	(3,557)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(3,296)	(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	(13)	(124)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(13)	(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	(4)	(103)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(4)	(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	(14)	(41)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(14)	(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	(5)	(29)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5)	(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	5,250	5,612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,250	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	2,055	2,207
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,055	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	1,860	2,023
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,860	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	62	89
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	62	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	83	95
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	83	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	405	438
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	405	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	463	511
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	463	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	3	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3	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	77	105
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	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	95	121
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	95	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	17
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	17
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	2,055	2,207
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,055	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	2,811	3,067
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,811	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	55	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	55	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	(838)	(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	(38)	(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	(22)	(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	(3,352)	(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	(239)	(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	2,753	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	(1)	(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	5	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	154	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	2,472	2,029
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(702)	(308)
FinancialAssetLiabilitiesNetFairValueDisclosure1	1,770	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	(702)	(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	(702)	(308)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(702)	(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	(1,685)	(995)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,685)	(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	(43)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(43)
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	(1,026)	(729)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,026)	(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	786	691
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	786	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	250	239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	250	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	417	366
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	417	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	19	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	19	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	156	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	156	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	250	239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	250	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	156	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	156	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	100	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	100	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	(1,500)	(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	(2,334)	(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	872	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	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, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(392)	(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	13	11
Derivative Liability, Noncurrent	(392)	(105)
Derivative Liability, Current	145	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	134	405
FinancialAssetsFairValueDisclosure1	13,257	13,329
Deferred Compensation Liability, Current and Noncurrent	(26)	(31)
Financial Liabilities Fair Value Disclosure	(562)	(350)
FinancialAssetLiabilitiesNetFairValueDisclosure1	12,695	12,979
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	134	405
Deferred Compensation Liability, Current and Noncurrent	(26)	(31)
Financial Liabilities Fair Value Disclosure	(562)	(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	(523)	(317)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(523)	(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	(6,084)	(6,487)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(6,084)	(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	(5,963)	(6,702)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5,963)	(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	(13)	(2)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(13)	(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	(4)	(2)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(4)	(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	(14)	(12)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(14)	(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	(14)	23
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(14)	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	(19)	(35)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(19)	(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	10,619	10,542
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	10,619	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	4,444	4,630
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,444	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	696	612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	696	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	2,110	2,262
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,110	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	1,165	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,165	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	83	95
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	83	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	405	438
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	405	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	463	511
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	463	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	417	366
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	417	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	19	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	19	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	17
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	17
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	5,140	5,242
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,140	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	4,226	4,302
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,226	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	388	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	388	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	100	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	100	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	134	405
FinancialAssetsFairValueDisclosure1	4,585	4,558
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	37	9
FinancialAssetLiabilitiesNetFairValueDisclosure1	4,622	4,549
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	134	405
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	37	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	37	(20)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	37	(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	(1,493)	(2,241)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,493)	(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	(111)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(111)
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	(1,641)	(2,416)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,641)	(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	(14)	(14)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(14)	(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	(14)	(25)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(14)	(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	4,583	4,239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,583	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	2,389	2,423
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,389	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	696	612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	696	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	1,165	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,165	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	7	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7	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	7	5
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7	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	12	11
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	12	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	3,085	3,035
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3,085	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	1,165	996
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,165	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	17	16
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	17	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	333	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	333	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	(167)	(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	(1,080)	(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	(117)	(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	1,364	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	(402)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(402)
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	17	16
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	17	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	(2,171)	(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	(20)	(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	(23)	(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	(1)	(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	(6,766)	(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	(394)	(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	4,989	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	(15)	(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	13	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	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 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	6,200	6,742
Deferred Compensation Liability, Current and Noncurrent	(26)	(31)
Financial Liabilities Fair Value Disclosure	(120)	(240)
FinancialAssetLiabilitiesNetFairValueDisclosure1	6,080	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	(26)	(31)
Financial Liabilities Fair Value Disclosure	(120)	(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	(81)	(196)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(81)	(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	(3,129)	(3,458)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(3,129)	(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	(248)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(248)
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	(3,296)	(3,557)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(3,296)	(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	(13)	(13)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(13)	(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	(4)	(2)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(4)	(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	(14)	(12)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(14)	(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	(5)	(10)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(5)	(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	5,250	5,612
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,250	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	2,055	2,207
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,055	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	1,860	2,023
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,860	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	62	89
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	62	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	83	95
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	83	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	405	438
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	405	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	463	511
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	463	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	3	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3	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	77	105
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	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	95	121
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	95	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	17
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	17
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	2,055	2,207
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,055	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	2,811	3,067
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	2,811	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	55	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	55	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	(838)	(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	(17)	(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	(1)	(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	(3,352)	(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	(239)	(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	2,753	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	(1)	(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	5	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	2,472	2,029
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(479)	(101)
FinancialAssetLiabilitiesNetFairValueDisclosure1	1,993	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	(479)	(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	(479)	(101)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(479)	(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	(1,462)	(788)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,462)	(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	(43)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(43)
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	(1,026)	(729)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(1,026)	(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	786	691
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	786	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	250	239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	250	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	417	366
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	417	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	19	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	19	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	156	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	156	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	250	239
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	250	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	156	184
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	156	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	100	83
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	100	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	(1,500)	(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	(2,334)	(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	872	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	30	3
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Investments, Fair Value Disclosure	30	3
PECO Energy Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	5	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	5	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	13	21
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(10)	(15)
Financial Liabilities Fair Value Disclosure	(10)	(15)
FinancialAssetLiabilitiesNetFairValueDisclosure1	3	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	(10)	(15)
Financial Liabilities Fair Value Disclosure	(10)	(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	5	12
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	5	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	13	21
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	13	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	(10)	(15)
Financial Liabilities Fair Value Disclosure	(10)	(15)
FinancialAssetLiabilitiesNetFairValueDisclosure1	(10)	(15)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(10)	(15)
Financial Liabilities Fair Value Disclosure	(10)	(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	5	25
Derivative Liability, Noncurrent	(203)	(187)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(203)	(187)
Derivative Liability, Current	20	20
Cash and Cash Equivalents, Fair Value Disclosure	5	25
Commonwealth Edison Co [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
FinancialAssetsFairValueDisclosure1	5	25
Derivative Liability, Noncurrent	(223)	(207)
Deferred Compensation Liability, Current and Noncurrent	(7)	(8)
Financial Liabilities Fair Value Disclosure	(230)	215
FinancialAssetLiabilitiesNetFairValueDisclosure1	(225)	(190)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(223)	(207)
Deferred Compensation Liability, Current and Noncurrent	(7)	(8)
Financial Liabilities Fair Value Disclosure	(230)	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	5	25
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	5	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	5	25
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	5	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	(223)	(207)
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(223)	207
FinancialAssetLiabilitiesNetFairValueDisclosure1	(223)	(207)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	(223)	(207)
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	(223)	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	46	103
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	46	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	51	108
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(3)	(5)
Financial Liabilities Fair Value Disclosure	(3)	5
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	(3)	(5)
Financial Liabilities Fair Value Disclosure	(3)	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	46	103
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Cash and Cash Equivalents, Fair Value Disclosure	46	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	51	108
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial Liabilities Fair Value Disclosure	0	0
FinancialAssetLiabilitiesNetFairValueDisclosure1	51	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	(3)	(5)
Financial Liabilities Fair Value Disclosure	(3)	5
FinancialAssetLiabilitiesNetFairValueDisclosure1	(3)	(5)
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis [Abstract]
Derivative Liability, Noncurrent	0	0
Deferred Compensation Liability, Current and Noncurrent	(3)	(5)
Financial Liabilities Fair Value Disclosure	(3)	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	$ (12)	$ (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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Exelon Generation Co L L C [Member]
Purchases, sales, issuances and settlements
Settlements	$ (4)			$ (6)
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	(182)		$ (394)
Decrease in Fair Value Adjustment	$ 14
Increase In Fair Value Adjustment				22
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		$ (46)		(357)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	(5)
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	1,770		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	30	(34)	18	(178)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	148	127	241	308
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	11
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Value		843		843			$ 752	$ 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	179	21	360	(425)
Purchases, sales, issuances and settlements
Purchases	148	127	241	308
Sales	(31)	(26)	(53)	(33)
Settlements		(12)		(19)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers In		(4)	15	(30)
Transfers out of Level 3	(30)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Out		(28)	(35)	(27)
Ending balance		843		843
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held	179	21	360	(425)
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	(2)	4	1	4
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities	$ 25	42	(1)	70
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			(15)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value								0
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements			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
Purchases, sales, issuances and settlements
Purchases			0
Sales			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements			0
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held			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
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities			15
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
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ (7)	(8)		(11)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		0		0	0		0	0
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings		0	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	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	0
Purchases, sales, issuances and settlements
Purchases	0	0	0
Sales	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	0	0	0
Transfers into Level 3		0	0
Transfers out of Level 3	0	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	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
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Regulatory Assets Liabilities	$ 7	8		11
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		(46)		(357)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	(5)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 7	8	15	11
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	1,993		1,993		1,962
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	30	(34)	18	(178)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	148	127	241	308
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3	11
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Value		977		977			920	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	179	21	360	(425)
Purchases, sales, issuances and settlements
Purchases	148	127	241	308
Sales	(31)	(26)	(53)	(33)
Settlements	(37)	12		(19)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers In		(4)	15	(30)
Transfers out of Level 3	(30)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Out		(28)	(35)	(27)
Ending balance		977		977
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held	179	21	360	(425)
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	(2)	4	1	4
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		2	4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	2
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 7	8	15	11
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	786		786		715			350
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			3
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	99	109	146	249
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(37)		(19)
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	786	592	786	592			486	691
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses	4	2	5	2
Purchases, sales, issuances and settlements
Purchases	99	109	146	249
Sales	0	(1)	(8)	(2)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(37)		(19)
Settlements		(12)	(66)
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	786	592	786	592
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held	4	2	5	2
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
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	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	156		156		178			112
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	6	13	11	42
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	156	133	156	133			137	184
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
Purchases, sales, issuances and settlements
Purchases	6	13	11	42
Sales	(26)	(21)	(40)	(25)
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	156	133	156	133
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
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	(2)	4	1	4
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] | 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		(48)	$ (39)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	(7)		(360)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 0	0	$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	1,021		1,021		1,066			465
Total realized / unrealized gains (losses)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	30	34	18	(178)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	16	5	57	15
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	11
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Value	1,021	242	1,021	242			287	1,050
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Total Gain Loss Included In Earnings Attributed To Changes In Unrealized Gains Losses	175	19	355	(427)
Purchases, sales, issuances and settlements
Purchases	16	5	57	15
Sales	(5)	(4)	(5)	(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		(4)	11
Transfers into Level 3			30
Transfers out of Level 3	(30)		(20)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Out		(28)	(35)
Ending balance	1,021	242	1,021	242
The amount of total losses included in income attributed to the change in unrealized gains (losses) related to assets and liabilities held	175	19	355	(427)
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	$ 0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	30		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
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	27	0	27	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	30	10	30	10			10	3
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
Purchases, sales, issuances and settlements
Purchases	27	0	27	2
Sales	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		(7)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Transfers Out		0	0
Ending balance	30	10	30	10
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
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
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	$ (223)		(223)					(193)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Included In Earnings		0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings, Description	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Included In Noncurrent Payables To Affiliates	$ 0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value					$ (241)
Total realized / unrealized gains (losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings			0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Liability Gain Loss Change In Collateral	0	0	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	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	(223)	(134)	(223)	(134)			$ (168)	$ (207)
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
Purchases, sales, issuances and settlements
Purchases	0	0	0
Sales	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	(223)	(134)	(223)	(134)
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
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	$ 18	$ 34	$ (16)	$ 59

Fair Value of Financial Asset63

Fair Value of Financial Assets and Liabilities Fair Value of Financial Assets and Liabilities - Narrative (Details)	Jun. 30, 2015USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Forward Power Basis	$ 3.33
Forward Gas Basis	0.34
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	$ 312,000,000

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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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	$ (17)	$ (62)	$ (27)	$ (330)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	171	(10)	340	(435)
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	10	14	(12)	(30)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	4	29	15	8
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	2	2	4	3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	4	2	5	2
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	(17)	(62)	(27)	(330)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	171	(10)	340	(435)
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	10	14	(12)	(30)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	4	29	15	8
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	2	2	4	3
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	$ 4	$ 2	$ 5	$ 2

Fair Value of Financial Asset65

Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
Derivatives Fair Value Footnotes [Abstract]
Cash collateral excluded	$ 154,000,000
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	872,000,000	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	1.27	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	122	120
Forward gas price assets	$ 13.46	$ 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	8.00%	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	233.00%	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	$ (5,000,000)	$ (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	119	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	$ (223,000,000)	$ (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	86.00%	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	123.00%	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	$ 108	$ 97
Forward gas price assets	8.53	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	$ 104	$ 76

Derivative Financial Instrume66

Derivative Financial Instruments - Summary of Interest Rate and Foreign Currency Hedges (Details) - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		$ 1,405	$ 1,279
Mark-to-market derivative assets		811	773
Derivative Liability, Current		165	234
Derivative Liability, Noncurrent		(595)	(403)
InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		10	15
Mark-to-market derivative assets		35	8
Derivative Liability, Current		9	1
Derivative Liability, Noncurrent		(5)	(114)
Total mark-to-market derivative net assets (liabilities)	[1]	31	(90)
Total mark-to-market derivative assets	[1]	45	23
Derivative Liability	[1]	(14)	(113)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		1,405	1,276
Mark-to-market derivative assets		790	771
Derivative Liability, Current		145	214
Derivative Liability, Noncurrent		(392)	(105)
Exelon Generation Co L L C [Member] | InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		10	12
Mark-to-market derivative assets		14	6
Derivative Liability, Current		9	1
Derivative Liability, Noncurrent		(5)	(3)
Total mark-to-market derivative net assets (liabilities)	[1]	10	16
Total mark-to-market derivative assets	[1]	24	18
Derivative Liability	[1]	(14)	(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		1	1
Derivative Liability, Current		9	8
Derivative Liability, Noncurrent		(5)	(4)
Total mark-to-market derivative net assets (liabilities)		(13)	(4)
Total mark-to-market derivative assets		1	8
Derivative Liability		(14)	(12)
Exelon Generation Co L L C [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Liability, Noncurrent		(2)
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		6	7
Derivative Liability, Current		9	14
Derivative Liability, Noncurrent		(5)	(9)
Total mark-to-market derivative net assets (liabilities)		2	4
Total mark-to-market derivative assets	[2]	16	27
Derivative Liability	[2]	(14)	(23)
Exelon Generation Co L L C [Member] | Collateral And Netting [Member] | InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		(10)	(22)
Mark-to-market derivative assets		(3)	(7)
Derivative Liability, Current		(14)	(25)
Derivative Liability, Noncurrent		5	10
Total mark-to-market derivative net assets (liabilities)	[1]	6	6
Total mark-to-market derivative assets	[1]	(13)	(29)
Derivative Liability	[1]	19	35
Exelon Generation Co L L C [Member] | Economic Hedging Instrument [Member] | InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		10	7
Mark-to-market derivative assets		10	5
Derivative Liability, Current		5	2
Derivative Liability, Noncurrent		0	0
Total mark-to-market derivative net assets (liabilities)		15	10
Total mark-to-market derivative assets		20	12
Derivative Liability		(5)	(2)
Corporate, Non-Segment [Member] | InterestRateAndForeignExchangeContract [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		0	3
Mark-to-market derivative assets		21	2
Derivative Liability, Current		0	0
Derivative Liability, Noncurrent		0	(111)
Total mark-to-market derivative net assets (liabilities)	[1]	21	(106)
Total mark-to-market derivative assets	[1]	21	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		21	20
Derivative Liability, Current		0	0
Derivative Liability, Noncurrent		0	(29)
Total mark-to-market derivative net assets (liabilities)		21	(6)
Total mark-to-market derivative assets		21	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		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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		(11)	$ 3
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	(3)
Interest Expense [Member] | Fair Value Hedging [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[1]			(2)	$ 5
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		(12)	(3)
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)	(8)
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	2
Gain (Loss) on Fair Value Hedges Recognized in Earnings			$ (4)		(8)
Designated as Hedging Instrument [Member] | Interest Expense [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[1]			(4)	(7)
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 six months ended June 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 six months ended June 30, 2014, the loss on Generation swaps included $4 million and $8 million realized in earnings, respectively, with an immaterial 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		Jun. 30, 2015		Dec. 31, 2014
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		$ 1,405		$ 1,279
Mark-to-market derivative assets (noncurrent assets)		811		773
Mark-to-market derivative liabilities (current liabilities)		(165)		(234)
Mark-to-market derivative liabilities (noncurrent liabilities)		(595)		(403)
Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		1,395		1,264
Mark-to-market derivative assets (noncurrent assets)		776		765
Total mark-to-market derivative assets		2,171		2,029
Mark-to-market derivative liabilities (current liabilities)		(156)		(235)
Mark-to-market derivative liabilities (noncurrent liabilities)		(590)		(289)
Total mark-to-market derivative liabilities		(746)		(524)
Total mark-to-market derivative net assets (liabilities)		1,425		1,505
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		1,405		1,276
Mark-to-market derivative assets (noncurrent assets)		790		771
Mark-to-market derivative liabilities (current liabilities)		(145)		(214)
Mark-to-market derivative liabilities (noncurrent liabilities)		(392)		(105)
Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		4,398		4,992
Mark-to-market derivative assets (noncurrent assets)		2,368		1,821
Total mark-to-market derivative assets		6,766		6,813
Mark-to-market derivative liabilities (current liabilities)		(3,793)		(4,947)
Mark-to-market derivative liabilities (noncurrent liabilities)		(2,291)		(1,540)
Total mark-to-market derivative liabilities		(6,084)		(6,487)
Total mark-to-market derivative net assets (liabilities)		682		326
Current assets collateral offset		297		416
Noncurrent assets collateral offset		144		171
Current liabilities collateral offset		358		599
Noncurrent liabilities collateral offset		175		220
Total cash collateral received net of cash collateral posted		974		(1,406)
Exelon Generation Co L L C [Member] | Derivative [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		1,395	[1]	1,264	[2]
Mark-to-market derivative assets (noncurrent assets)		776	[1]	765	[2]
Total mark-to-market derivative assets		2,171	[1]	2,029	[2]
Mark-to-market derivative liabilities (current liabilities)		(136)	[1]	(215)	[2]
Mark-to-market derivative liabilities (noncurrent liabilities)		(387)	[1]	(102)	[2]
Total mark-to-market derivative liabilities		(523)	[1]	(317)	[2]
Total mark-to-market derivative net assets (liabilities)		1,648	[1]	1,712	[2]
Exelon Generation Co L L C [Member] | Proprietary Trading [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		346		456
Mark-to-market derivative assets (noncurrent assets)		48		56
Total mark-to-market derivative assets		394		512
Mark-to-market derivative liabilities (current liabilities)		(347)		(468)
Mark-to-market derivative liabilities (noncurrent liabilities)		(55)		(64)
Total mark-to-market derivative liabilities		(402)		(532)
Total mark-to-market derivative net assets (liabilities)		(8)		(20)
Exelon Generation Co L L C [Member] | Collateral And Netting [Member]
Derivative [Line Items]
Mark-to-market derivative assets (current assets)		(3,349)		(4,184)
Mark-to-market derivative assets (noncurrent assets)		(1,640)		(1,112)
Total mark-to-market derivative assets	[3]	(4,989)		(5,296)
Mark-to-market derivative liabilities (current liabilities)		4,004		5,200
Mark-to-market derivative liabilities (noncurrent liabilities)		1,959		1,502
Total mark-to-market derivative liabilities	[3]	5,963		6,702
Total mark-to-market derivative net assets (liabilities)	[3]	974		1,406
Commonwealth Edison Co [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities (current liabilities)		(20)		(20)
Mark-to-market derivative liabilities (noncurrent liabilities)		(203)		(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)		(20)		(20)
Mark-to-market derivative liabilities (noncurrent liabilities)		(203)		(187)
Total mark-to-market derivative liabilities	[4]	(223)		(207)
Total mark-to-market derivative net assets (liabilities)	[4]	$ (223)		$ (207)
[1]	Current and noncurrent assets are shown net of collateral of $297 million and $144 million, respectively, and current and noncurrent liabilities are shown net of collateral of $358 million and $175 million, respectively. The total cash collateral posted, net of cash collateral received and offset against mark-to-market assets and liabilities was $974 million at June 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			6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Gain loss on interest rate swap treasury rate lock net of tax				$ 25	$ 10		$ 40
Income taxes		$ (327)		(277)	(690)		(224)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Income taxes		(181)		(199)	(407)		1
Electrical Generation Revenue		(4,079)		(3,588)	(9,709)		(7,644)
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]	0		(25)	10		(40)
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]	0		(25)	0		(40)
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		(21)		45	(21)		45		$ (18)		$ 116
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)		(62)
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					(5)
Cash Flow Hedging [Member]
Derivative [Line Items]
Effective portion of changes in fair value		1			(10)		(11)
Cash Flow Hedging [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Cash Flow Hedge Accumulated Other Comprehensive Income Gain Loss		(19)		47	(19)		47		$ (28)		$ 120
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)		(62)
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					(5)
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		(19)		47	(19)		47	$ (22)		$ 95
Effective portion of changes in fair value				(10)
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]
Electrical Generation Revenue		(2)		(38)
Energy Related Hedges [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Cash Flow Hedge Accumulated Other Comprehensive Income Gain Loss		(21)	[2]	45	(21)	[2]	$ 45	$ (23)		$ 88
Effective portion of changes in fair value		0		(5)	$ (6)
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]
Electrical Generation Revenue		$ (2)		$ (38)
[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 Six Months Ended June 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 (6) (10) Reclassifications from accumulated OCI to net incomeOther, net — 16(a) Reclassifications from accumulated OCI to net incomeInterest Expense 5 5 Reclassifications from accumulated OCI to net incomeOperating Revenues (2) (2) Accumulated OCI derivative gain at June 30, 2015 $(21) $(19)

Derivative Financial Instrume70

Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		$ (2)	$ (6)
Unrealized Gain (Loss) on Derivatives				$ 507	$ (751)
Gain (Loss) on Sale of Derivatives	[1]			(26)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives				396	(760)
Gain (Loss) on Sale of Derivatives	[1]			0
Unrealized Gain (Loss) on Commodity Contracts		25	(83)	179	(843)
Operating Revenue [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net				1	(7)
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		413	(15)	497	(745)
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		235	(15)	397	(745)
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		210	69	218	99
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		178	0	100	0
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	(1)	0	(1)
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		25	(83)	179	(843)
Not Designated as Hedging Instrument [Member] | Commodity Contract [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		240	(10)	391	(739)
Gain (Loss) on Sale of Derivatives		(67)	3	(1)	(46)
Unrealized Gain (Loss) on Commodity Contracts		307	(13)	392	(693)
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		240	(10)	391	(739)
Gain (Loss) on Sale of Derivatives		(67)	3	(1)	(46)
Unrealized Gain (Loss) on Commodity Contracts		307	(13)	392	(693)
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		210	69	218	99
Gain (Loss) on Sale of Derivatives		100	(42)	203	(183)
Unrealized Gain (Loss) on Commodity Contracts		110	111	15	282
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
Gain (Loss) on Sale of Derivatives		0		0	0
Unrealized Gain (Loss) on Commodity Contracts		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		30	(79)	173	(838)
Gain (Loss) on Sale of Derivatives		(167)	45	(204)	137
Unrealized Gain (Loss) on Commodity Contracts		197	(124)	377	(975)
Not Designated as Hedging Instrument [Member] | InterestRateandForeignExchange [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		173	(5)	106	(6)
Unrealized Gain (Loss) on Derivatives		111	(4)		(5)
Unrealized Gain (Loss) on Foreign Currency Derivatives, Net, before Tax				46
Gain (Loss) on Sale of Derivatives		62	(1)	60	(1)
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		(5)	(5)	6	(6)
Unrealized Gain (Loss) on Derivatives		(3)	(4)		(5)
Unrealized Gain (Loss) on Foreign Currency Derivatives, Net, before Tax				10
Gain (Loss) on Sale of Derivatives		(2)	(1)	(4)	(1)
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
Unrealized Gain (Loss) on Foreign Currency Derivatives, Net, before Tax				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		178	0	100	0
Unrealized Gain (Loss) on Derivatives		114			0
Unrealized Gain (Loss) on Foreign Currency Derivatives, Net, before Tax				36
Gain (Loss) on Sale of Derivatives		64		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	(1)	0	(1)
Unrealized Gain (Loss) on Derivatives		0	(1)		(1)
Unrealized Gain (Loss) on Foreign Currency Derivatives, Net, before Tax				0
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		(5)	(4)	6	(5)
Unrealized Gain (Loss) on Derivatives		(3)	(3)		(4)
Unrealized Gain (Loss) on Foreign Currency Derivatives, Net, before Tax				10
Gain (Loss) on Sale of Derivatives		$ (2)	$ (1)	$ (4)	$ (1)
[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) - Consolidation Items [Domain] - Entity [Domain] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ (2)	$ (6)
Operating Revenue [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net			$ 1	$ (7)
Operating Revenue [Member] | Principal or Proprietary Transactions [Member]
Derivative [Line Items]
Proprietary Trading Activities Change In Fair Value	0	0	4	(1)
Proprietary Trading Activities Reclassification To Realized At Settlement	(2)	1	(6)	1
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(2)	1	(2)	0
Commodity Contract [Member] | Operating Revenue [Member] | Principal or Proprietary Transactions [Member]
Derivative [Line Items]
Proprietary Trading Activities Change In Fair Value	7	1	8	0
Proprietary Trading Activities Reclassification To Realized At Settlement	(7)	(8)	(5)	(7)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 0	$ (7)	$ 3	$ (7)

Derivative Financial Instrume72

Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) - Jun. 30, 2015 - USD ($) $ in Millions	Total
PECO Energy Co [Member]
Derivative [Line Items]
Total Credit Risk Exposure	$ 3
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	2,244
Credit derivative net exposure	$ 2,196
Credit Derivative, Collateral Held Directly or by Third Parties	48
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	383
Exelon Generation Co L L C [Member] | Energy Cooperatives And Municipalities [Member]
Derivative [Line Items]
Credit derivative net exposure	881
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	880
Exelon Generation Co L L C [Member] | Other Credit Risk Exposure [Member]
Derivative [Line Items]
Credit derivative net exposure	52
Exelon Generation Co L L C [Member] | External Credit Rating, Investment Grade [Member]
Derivative [Line Items]
Credit Derivative, Maximum Exposure, Undiscounted	1,643
Credit derivative net exposure	$ 1,619
Credit Derivative, Collateral Held Directly or by Third Parties	24
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	$ 37
Credit Derivative, Collateral Held Directly or by Third Parties	18
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	48
Credit derivative net exposure	$ 42
Credit Derivative, Collateral Held Directly or by Third Parties	6
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	498
Credit derivative net exposure	$ 498
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		Jun. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Derivative, Collateral, Obligation to Return Cash		$ 30
Derivative, Collateral, Obligation to Return Securities		18
Energy Supply Procurement [Member]
Derivative [Line Items]
Derivative Asset, Fair Value of Collateral		2
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		(1,558)	$ (1,433)
Contractual right of offset related to derivative assets		1,275	1,140
Net liability position after contractual right of offset	[1]	(283)	(293)
Derivative, Collateral, Right to Reclaim Cash		1,020	1,497
Derivative, Collateral, Right to Reclaim Securities		511	672
Derivative, Collateral, Obligation to Return Cash		39	77
Derivative, Collateral, Obligation to Return Securities		$ 23	$ 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		6 Months Ended
		Jun. 30, 2015USD ($)	Jun. 30, 2014USD ($)	Jun. 30, 2015USD ($)MWh		Jun. 30, 2014USD ($)MWh	Dec. 31, 2014USD ($)
Derivative [Line Items]
Income taxes		$ 327	$ 277	$ 690		$ 224
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax			63	$ 2		102
Hypothetical Increase In Interest Rates				0.50%
Mark-to-market derivative assets (noncurrent assets)		811		$ 811			$ 773
Hypothetical increase in interest rates associated with variable-rate debt				2
Ineffective portion recognized in income		4	5	8	[1]	8
Mark-to-market derivative liabilities (noncurrent liabilities)		595		595			403
Cash collateral held		30		30
Letters of credit collateral posted		18		18
Interest Rate Fair Value Hedge Asset at Fair Value		31		31
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Notional Amount of Pre-issuance Interest Rate Cash Flow Hedge Derivatives		754		754
Energy Supply Procurement [Member]
Derivative [Line Items]
Derivative Asset, Fair Value of Collateral		2		2
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		181	199	$ 407		$ (1)
Proprietary trading activities volume | MWh				3,006,000		8,129,000
Mark-to-market derivative assets (noncurrent assets)		790		$ 790			771
Mark-to-market derivative liabilities (noncurrent liabilities)		392		392			105
Cash collateral received not offset against net derivative positions		2		2			8
Credit exposure under natural gas supply and management agreements		2,244		2,244
Cash collateral posted		1,020		1,020			1,497
Letters of credit collateral posted		511		511			672
Cash collateral held		39		39			77
Letters of credit collateral posted		23		23			24
Incremental collateral for loss of investment grade credit rating		2,200		2,200			2,400
Interest Rate Fair Value Hedge Asset at Fair Value		10		10
Commonwealth Edison Co [Member]
Derivative [Line Items]
Income taxes		68	72	127		$ 137
Mark-to-market derivative liabilities (noncurrent liabilities)		203		203			187
PECO Energy Co [Member]
Derivative [Line Items]
Income taxes		27	23	$ 85		57
Estimated percentage of natural gas purchases hedged				30.00%
Total		3		$ 3
Incremental collateral for loss of investment grade credit rating		20		20
Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Income taxes		32	14	105		72
Total		1		1
Incremental collateral for loss of investment grade credit rating		34		$ 34
Minimum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months				98.00%
Expected Generation Hedged In Year Two				77.00%
Expected generation hedged in year three				46.00%
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				101.00%
Expected Generation Hedged In Year Two				80.00%
Expected generation hedged in year three				49.00%
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)		2		2
Foreign Exchange Contract [Member] | Exelon Generation Co L L C [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount		146		146
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		(11)	3
Mark-to-market derivative assets (noncurrent assets)		20		20			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	(3)
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)		2		2
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		2,400
ExGen Texas Power [Member] | Interest Rate Swap [Member] | Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative, Notional Amount		502		502
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)		10		10
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		201		201
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]	0	25	(10)		40
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]	0	$ 25	0		$ 40
Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		36		36
PECO Energy Co Affiliate [Member] | PECO Energy Co [Member]
Derivative [Line Items]
Net receivable from affiliated electric and gas utility		35		35
Baltimore Gas And Electric Company Affiliate [Member] | Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Net receivable from affiliated electric and gas utility		$ 31		$ 31
[1]	For the three and six months ended June 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 six months ended June 30, 2014, the loss on Generation swaps included $4 million and $8 million realized in earnings, respectively, with an immaterial 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	Jun. 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	503	304
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings	$ 0	$ 120

Debt and Credit Agreements - Li

Debt and Credit Agreements - Lines of Credit under Committed Credit Facilities (Details) - USD ($) $ in Millions		Jun. 30, 2015	Jun. 30, 2014	May. 01, 2014
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1]	$ 8,500
Bridge Loan				$ 7,200
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	[1],[2]	500
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 3,200
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	[1]	300
Exelon Generation Co L L C [Member] | CIBC [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	[1]	100
Exelon Generation Co L L C [Member] | SUMITOMO [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	[1]	100
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]	1,000
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	[1],[2]	600
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	[1],[2]	600
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	[1]	5,100
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	[1]	$ 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 expire on October 16, 2015. These facilities are solely utilized to issue letters of credit. As of June 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) - Derivative Contract [Domain] $ in Millions		Jul. 06, 2015USD ($)	Jun. 11, 2014USD ($)	Jun. 01, 2014shares	Jun. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Jun. 30, 2014USD ($)	May. 01, 2014USD ($)
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 1,708	$ 1,191
Line of Credit Facility, Maximum Borrowing Capacity	[1]				$ 8,500	8,500
Bridge Loan								$ 7,200
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	$ 131
Parent Company [Member]
Debt Instrument [Line Items]
Basis points adders for prime-based borrowings					0.28%	0.28%
Basis Points For Libor Based Borrowings					0.0128	0.0128
Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 260	617
Basis points adders for prime-based borrowings					0.08%	0.08%
Basis Points For Libor Based Borrowings					0.0108	0.0108
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 39	538
Basis points adders for prime-based borrowings					0.28%	0.28%
Basis Points For Libor Based Borrowings					0.0019	0.0019
Debt Instrument, Face Amount							3,200
PECO Energy Co [Member]
Debt Instrument [Line Items]
Basis points adders for prime-based borrowings					0.00%	0.00%
Basis Points For Libor Based Borrowings					0.009	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%	0.00%
Basis Points For Libor Based Borrowings					0.01	0.01
Revolving Credit Facility [Member] | Commonwealth Edison Co [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1]				$ 1,000	$ 1,000
Revolving Credit Facility [Member] | PECO Energy Co [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1],[2]				600	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	600
Parent [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	[1],[2]				500	500
AVSR [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt							$ 1
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum							2.33%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum							3.55%
Senior Notes [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[3]				750	750
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					4,200	$ 4,200
Convertible Debt Securities [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Subordinated Long-term Debt					$ 1,110
Maximum [Member]
Debt Instrument [Line Items]
Basis points adders for prime-based borrowings					0.07%	0.07%
Basis Points For Libor Based Borrowings					0.0017	0.0017
ExGen425Feb062021 [Member] | Senior Notes [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Interest Rate							4.44%
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%	1.43%
Debt Instrument, Face Amount					$ 50	$ 50
TaxExemptBonds255 [Member] | First Mortgage Bonds [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum						2.50%
Debt Instrument, Face Amount	[4]				435	$ 435
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum						2.70%
AVSR [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum						2.29%
Debt Instrument, Face Amount					$ 39	$ 39
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum						2.96%
AVSR [Member] | AVSR [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt						$ 6
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum						2.29%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum						3.56%
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] | AVSR [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt		$ 6
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum		2.29%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum		3.55%
[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 expire on October 16, 2015. These facilities are solely utilized to issue letters of credit. As of June 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		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014
Debt Instrument [Line Items]
Long-term Debt		$ 131
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],[2]	$ 1,250
Senior Notes [Member] | MergerDebt495June152035 [Member]
Debt Instrument [Line Items]
Interest Rate		4.95%
Debt Instrument, Face Amount	[1],[2]	$ 500
Senior Notes [Member] | MergerDebt510June152045 [Member]
Debt Instrument [Line Items]
Interest Rate		5.10%
Debt Instrument, Face Amount	[1],[2]	$ 1,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 4,200
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]
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 3,200
Exelon Generation Co L L C [Member] | AVSR [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 39
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum		2.29%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum		2.96%
Exelon Generation Co L L C [Member] | First Mortgage Bonds [Member] | TaxExemptBonds255 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[3]	$ 435
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum		2.50%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum		2.70%
Exelon Generation Co L L C [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	[4]	$ 750
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	[4]	$ 750
Exelon Generation Co L L C [Member] | Senior Notes [Member] | ExGen425Feb062021 [Member]
Debt Instrument [Line Items]
Interest Rate			4.44%
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		$ 50
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] | Subordinated Debt [Member] | JuniorNotes250June012024 [Member]
Debt Instrument [Line Items]
Interest Rate			2.50%
Debt Instrument, Face Amount			$ 1,150
Exelon Generation Co L L C [Member] | Notes Payable, Other Payables [Member] | NuclearFuelPurchaseContract3250june302018Member [Member]
Debt Instrument [Line Items]
Interest Rate			3.35%
Debt Instrument, Face Amount			$ 38
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
[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 2025 notes, the 2035 notes and the 2045 notes must be redeemed upon the earlier of (i) December 31, 2015, if the PHI acquisition is not consummated on or prior to such date, or (ii) the date on which the Merger Agreement relating to the PHI acquisition is terminated.
[3]	The Tax Exempt Pollution Control Revenue Bonds have a mandatory put date that ranges from March 1, 2019 - September 1, 2020.
[4]	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		Jul. 06, 2015	Jun. 30, 2015	Jun. 30, 2014
Debt Instrument [Line Items]
Repayments of Long-term Debt			$ 1,708	$ 1,191
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
Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt			$ 39	$ 538
Exelon Generation Co L L C [Member] | AVSR [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum			2.29%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum			2.96%
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] | 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			$ 2	$ 2
Exelon Generation Co L L C [Member] | AVSR [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt				$ 1
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum				2.33%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum				3.55%
Exelon Generation Co L L C [Member] | AVSR [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt		$ 6
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum		2.29%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum		3.55%
Exelon Generation Co L L C [Member] | AVSR [Member] | AVSR [Member]
Debt Instrument [Line Items]
Repayments of Long-term Debt			$ 6
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum			2.29%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum			3.56%
Exelon Generation Co L L C [Member] | Subordinated Debt [Member] | ExgenRenewables425February62021 [Member]
Debt Instrument [Line Items]
Interest Rate			4.49%	4.25%
Repayments of Long-term Debt			$ 14	$ 3
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			$ 10	$ 11
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			$ 3
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			$ 2
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		6 Months Ended
	Jun. 30, 2015	Mar. 31, 2014	Jun. 30, 2015	Jun. 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	3.90%	2.10%	3.20%	(0.60%)
Qualified nuclear decommissioning trust fund income	(1.00%)	4.10%	0.60%	5.90%
Domestic production activities deduction	(2.00%)	(2.00%)	(2.10%)	(3.20%)
Health care reform legislation	0.00%	0.00%	0.00%	0.10%
Amortization of investment tax credit, net deferred taxes	(0.60%)	(0.40%)	(0.80%)	(1.20%)
Plant basis differences	(1.00%)	(1.60%)	(1.10%)	(3.00%)
Production tax credits and other credits	1.30%	0.80%	1.60%	2.40%
Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent	(0.40%)	(2.00%)	(0.60%)	(1.90%)
Other	1.40%	(1.20%)	0.80%	(3.10%)
Effective income tax rate	34.00%	33.20%	33.40%	25.60%
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	3.40%	1.70%	3.00%	(14.70%)
Qualified nuclear decommissioning trust fund income	(1.70%)	6.00%	0.90%	27.70%
Domestic production activities deduction	(3.40%)	(2.90%)	(3.40%)	(14.80%)
Health care reform legislation	0.00%	0.00%	0.00%	0.00%
Amortization of investment tax credit, net deferred taxes	(0.90%)	(0.50%)	(1.10%)	(4.90%)
Plant basis differences	0.00%	0.00%	0.00%	0.00%
Production tax credits and other credits	2.20%	1.10%	2.50%	11.10%
Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent	(0.60%)	(2.90%)	(0.80%)	(8.80%)
Other	2.00%	(0.40%)	0.60%	(8.90%)
Effective income tax rate	31.60%	34.90%	31.70%	(0.50%)
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	5.60%	4.60%	5.30%	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%)	(0.40%)	(0.20%)	(0.50%)
Production tax credits and other credits	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent	0.00%	0.00%	0.00%	0.00%
Other	0.50%	0.20%	0.40%	0.20%
Effective income tax rate	40.70%	39.30%	40.20%	39.60%
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	1.40%	(0.50%)	1.30%	0.40%
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	(9.00%)	(13.20%)	(7.50%)	(10.80%)
Production tax credits and other credits	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent	0.00%	0.00%	0.00%	0.00%
Other	0.50%	0.30%	0.20%	0.30%
Effective income tax rate	27.80%	21.50%	28.90%	24.80%
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%	4.10%	5.30%	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	0.10%	0.20%	0.20%	0.20%
Amortization of investment tax credit, net deferred taxes	(0.20%)	(0.70%)	(0.10%)	(0.30%)
Plant basis differences	(0.50%)	5.10%	(0.30%)	0.40%
Production tax credits and other credits	(0.00%)	(0.00%)	(0.00%)	(0.00%)
Effective Income Tax Rate Reconciliation, Noncontrolling Interest Income (Loss), Percent	0.00%	0.00%	0.00%	0.00%
Other	0.80%	(1.30%)	0.00%	0.10%
Effective income tax rate	40.50%	42.40%	40.10%	40.40%

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended				6 Months Ended
	Jul. 28, 2015	Sep. 30, 2014	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Mar. 31, 2013	Jun. 30, 2015	Jun. 30, 2014	Jul. 20, 2015	Dec. 31, 2014	Dec. 31, 2009
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			$ 1,289				$ 1,289			$ 1,829
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions				$ 661
Unrecognized Tax Benefits, Increase Resulting from Settlements with Taxing Authorities							347
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			810				810
Early termination amount					$ 335
Unrecognized Tax Benefits, Interest on Income Taxes Accrued						265
Income taxes			327		277		690	$ 224
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			395				395
Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			745				745			1,357
Unrecognized tax benefits that if recognized would affect the effective tax rate			227				227
Increase (Decrease) in Income Taxes		$ 227
Effective Income Tax Rate Reconciliation, Tax Settlement, Amount			120
Income taxes			181		199		407	(1)
Exelon Generation Co L L C [Member] | Settlement with Taxing Authority [Member] | Subsequent Event [Member]
Income Tax Additional Narrative Information [Line Items]
Expected non-cash charge to earnings									$ 21
Unrecognized Tax Benefits, Interest on Income Taxes Accrued									$ 21
Income taxes	$ 45
Commonwealth Edison Co [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			146				146			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			310				310
Unrecognized Tax Benefits, Interest on Income Taxes Accrued						$ 170
Income taxes			68		72		127	137
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			145				145
PECO Energy Co [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			0				0			44
Income taxes			27		23		85	57
Baltimore Gas and Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits			120				120			$ 0
Income taxes			$ 32		$ 14		$ 105	$ 72

Nuclear Decommissioning - Rollf

Nuclear Decommissioning - Rollforward of Nuclear Decommissioning ARO (Details) - Nuclear Decommissioning Asset Retirement Obligation [Member] - Exelon Generation Co L L C [Member] - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2015	Dec. 31, 2014
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Nuclear Decommissioning ARO, Beginning Balance	[1]	$ 6,961
Accretion expense		189
Costs incurred to decommission retired plants		(1)
Nuclear Decommissioning ARO, Ending Balance	[1]	7,204
Asset Retirement Obligation, Revision of Estimate	[2]	55
Current portion of ARO		$ 7	$ 8
[1]	Includes $7 million and $8 million as the current portion of the ARO at June 30, 2015 and December 31, 2014 respectively, which is included in Other current liabilities on Exelon’s and Generation’s Consolidated Balance Sheets.
[2]	the fair value of the CENG ARO liability as of April 1, 2014, the date of consolidation. See Note 6 — Investment in Constellation Energy Nuclear Group, LLC for additional information.

Nuclear Decommissioning (Detail

Nuclear Decommissioning (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	$ 10,607	$ 10,537
Decommissioning Liability, Noncurrent	135	155
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	10,607	10,537
Decommissioning Liability, Noncurrent	135	$ 155
Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Liability, Noncurrent	$ 88

Nuclear Decommissioning - Unrea

Nuclear Decommissioning - Unrealized Gains on NDT Funds (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Unrealized Losses On Nuclear Decommissioning Trust Fund Investment [Line Items]
Net unrealized gains (losses) on decommissioning trust funds - regulatory agreement units	[1]	$ (133)	$ 172	$ (85)	$ 234
Net unrealized gains (losses) on decommissioning trust funds - non-regulatory agreement units	[2],[3]	$ (96)	128	(56)	141
Unrealized Gain Loss Investment Income Pledged Assets			$ 10	$ 9	$ 20
[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 $10 million of net unrealized gains related to the Zion Station pledged assets for the three months ended June 30, 2014 and $9 million and $20 million of net unrealized gains related to the Zion Station pledged assets for the six months ended June 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		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Nuclear Decommissioning Additional Narrative Information [Line Items]
Pledged assets for Zion Station decommissioning		$ 264		$ 319
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Pledged assets for Zion Station decommissioning		264		319
Payable to Zion Solutions	[1]	241		292
Current portion of payable to Zion Solutions	[2]	106		$ 137
Withdrawals by Zion Solutions to pay decommissioning costs		$ 731	$ 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			6 Months Ended
		Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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		$ 6		$ 5	$ 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		13	29	$ 26
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]	68		63	133	139
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		51		40	103	96
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		9	19	21
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		17		17	$ 33	$ 33
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		3		2	$ 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	$ 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 six months ended June 30, 2015, the costs related to CENG were $6 million and $11 million, respectively. For the period of April 1, 2014 to June 30, 2014, amounts include $5 million related to CENG.

Retirement Benefits - Calculati

Retirement Benefits - Calculation of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1]	$ 38	$ 19	$ 60		$ 48
Amortization of:
Pension and Other Postretirement Benefit Expense				317		315
CENG [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1]	3	1	4
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		81	74	163	[2]	143	[2]
Interest cost		178	190	355	[2]	373	[2]
Expected return on assets		(256)	(251)	(513)	[2]	(492)	[2]
Amortization of:
Prior service cost (benefit)		4	4	7	[2]	7	[2]
Actuarial loss		142	104	285	[2]	209	[2]
Net periodic benefit cost		149	121
Pension Plan, Defined Benefit [Member] | Regulatory Assets [Member]
Amortization of:
Net periodic benefit cost	[2]			297		240
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost		29	30	59	[2]	62	[2]
Interest cost		42	47	83	[2]	103	[2]
Expected return on assets		(37)	(38)	(75)	[2]	(76)	[2]
Amortization of:
Prior service cost (benefit)		(44)	(30)	(88)	[2]	(34)	[2]
Actuarial loss		21	12	41	[2]	20	[2]
Net periodic benefit cost		11	21
Other Postretirement Benefit Plan, Defined Benefit [Member] | Regulatory Assets [Member]
Amortization of:
Net periodic benefit cost	[2]			20		$ 75
CENG [Member]
Amortization of:
Pension and Other Postretirement Benefit Costs		6	5	11
CENG [Member] | Pension Plan, Defined Benefit [Member]
Amortization of:
Pension and Other Postretirement Benefit Costs		3	2	5
CENG [Member] | Other Postretirement Benefit Plan, Defined Benefit [Member]
Amortization of:
Pension and Other Postretirement Benefit Costs		$ 3	$ 3	$ 6
[1]	Includes $3 million and $4 million, respectively, related to CENG for the three and six months ended June 30, 2015. For the period of April 1, 2014 to June 30, 2014, amounts include $1 million related to CENG.
[2]	For the three months ended June 30, 2015, the cost for pension benefits and other postretirement benefits related to CENG were $3 million and $3 million, respectively. For the six months ended June 30, 2015, the cost for pension benefits and other postretirement benefits related to CENG were $5 million and $6 million, respectively. For the period of April 1, 2014 to June 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.

Retirement Benefits - Allocated

Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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]	$ 68	$ 63	$ 133	$ 139
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		51	40	103	96
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	9	19	21
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		17	17	33	33
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	13	29	$ 26
CENG [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension And Other Postretirement Benefit Expense Included In Capital And Operating And Maintenance Expense		6	5	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		$ 3	$ 2	$ 5
[1]	For the three and six months ended June 30, 2015, the costs related to CENG were $6 million and $11 million, respectively. For the period of April 1, 2014 to June 30, 2014, amounts include $5 million related to CENG.
[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		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1]	$ 38	$ 19	$ 60	$ 48
CENG [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1]	3	1	4
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[1]	20	10	33	24
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		8	5	13	12
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		3	2	4	4
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions		3	1	5	4
Business Services Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	[2]	$ 4	$ 1	$ 5	$ 4
[1]	Includes $3 million and $4 million, respectively, related to CENG for the three and six months ended June 30, 2015. For the period of April 1, 2014 to June 30, 2014, amounts include $1 million related to CENG.
[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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	$ 1	$ 4	$ 21	$ 6
Exelon Generation Co L L C [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	(1)	2	17	4
Commonwealth Edison Co [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	0	0	0	0
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		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			$ (2,684)		$ (2,040)
OCI before reclassifications	[1]			(48)		246
Amounts reclassified from AOCI	[1],[2]			106		(112)
Net current-period OCI		$ 50	$ 131	58	[1]	134	[1]
Ending balance	[1]	(2,626)	(1,906)	(2,626)		(1,906)
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]			(10)		(11)
Amounts reclassified from AOCI	[1],[2]			19		(62)
Net current-period OCI	[1]			9		(73)
Ending balance	[1]	(19)	47	(19)		47
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		1
Net current-period OCI	[1]			0		1
Ending balance	[1]	3	3	3		3
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)		246
Amounts reclassified from AOCI	[1],[2]			87		66
Net current-period OCI	[1]			58		312
Ending balance	[1]	(2,582)	(1,948)	(2,582)		(1,948)
Accumulated Translation Adjustment [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance				(19)	[1]	(10)
OCI before reclassifications	[1]			(9)		(1)
Net current-period OCI	[1]			(9)		(1)
Ending balance	[1]	(28)	(11)	(28)		(11)
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		(116)
Net current-period OCI	[1]			0		(105)
Ending balance	[1]	0	3	0		3
Exelon Generation Co L L C [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	[1]			(36)		214
OCI before reclassifications	[1]			(14)		1
Amounts reclassified from AOCI	[1],[2]			3		(178)
Net current-period OCI		6	(155)	(11)	[1]	(177)	[1]
Ending balance	[1]	(47)	37	(47)		37
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]			(6)		(8)
Amounts reclassified from AOCI	[1],[2]			3		(62)
Net current-period OCI	[1]			(3)		(70)
Ending balance	[1]	(21)	44	(21)		44
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]			1		(1)
Net current-period OCI	[1]			1		(1)
Ending balance	[1]	2	1	2		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]			(9)		(1)
Net current-period OCI	[1]			(9)		(1)
Ending balance	[1]	(28)	(11)	(28)		(11)
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		(116)
Net current-period OCI	[1]			0		(105)
Ending balance	[1]	0	3	0		3
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				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues		$ 6,514	[1]	$ 6,024	[1]	$ 15,345	[2]	$ 13,261	[2]
Income before income taxes		962		834		2,064		875
Income taxes		(327)		(277)		(690)		(224)
Net income		633		557		1,372		651
Prior service benefit reclassified to periodic benefit cost		8		5		15		5
Other Nonoperating Income (Expense)		(17)		230		64		330
Equity in losses of unconsolidated affiliates		0		0		(2)		(20)
Interest Expense		145		228		480		445
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	[3]	(46)		123		(106)		112
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]	(2)		63		(29)		102
Income taxes	[3]	0		(25)		10		(40)
Net income	[3]	(2)		38		(19)		62
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				63				102
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		(2)				(5)
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)		(49)		(142)		(107)
Income taxes		27	[3]	18		55	[3]	41
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	[3]	(44)				(87)
Net income	[3]			(31)				(66)
Prior service benefit reclassified to periodic benefit cost		19	[3],[4]	12		38	[3],[4]	10
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax		(90)	[3],[4]	(61)		(180)	[3],[4]	(117)
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]			193				193
Income taxes				(77)				(77)
Net income	[3]			116				116
Other Nonoperating Income (Expense)				193				193
Exelon Generation Co L L C [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues		4,232		3,789		10,074		8,179
Income before income taxes		573		571		1,285		187
Income taxes		(181)		(199)		(407)		1
Net income		390		372		875		188
Other Nonoperating Income (Expense)		(31)		216		62		300
Equity in losses of unconsolidated affiliates				(1)		(3)		(20)
Interest Expense		90		74		180		147
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]	(2)		154		(3)		178
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]	(2)		63		(3)		102
Income taxes	[3]	0		(25)		0		(40)
Net income	[3]	(2)		38		(3)		62
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				63				102
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		(2)				(5)
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]			193				193
Income taxes				(77)				(77)
Net income	[3]			116				116
Other Nonoperating Income (Expense)				$ 193				$ 193
[1]	(c)For the three months ended June 30, 2015 and 2014, utility taxes of $24 million and $21 million, respectively, are included in revenues and expenses for Generation. For the three months ended June 30, 2015 and 2014, utility taxes of $55 million and $56 million, respectively, are included in revenues and expenses for ComEd. For the three months ended June 30, 2015 and 2014, utility taxes of $32 million and $30 million, respectively, are included in revenues and expenses for PECO. For the three months ended June 30, 2015 and 2014, utility taxes of $21 million and $19 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		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	[1]	$ (2,626)	$ (1,906)	$ (2,626)	$ (1,906)	$ (2,684)	$ (2,040)
Pension and non-pension postretirement benefit plans:
Prior service benefit reclassified to periodic benefit cost		8	5	15	5
Actuarial loss reclassified to periodic cost		(35)	(23)	(69)	(46)
Pension and non-pension postretirement benefit plans valuation adjustment		0	(166)	17	(159)
Change in unrealized (gain) loss on cash flow hedges		(2)	28	(6)	48
Change in unrealized income on equity investments		0	77	0	70
Change in marketable securities		1		1	0
Total		(28)	(79)	(42)	(82)
Exelon Generation Co L L C [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive loss, net	[1]	(47)	37	(47)	37	$ (36)	$ 214
Pension and non-pension postretirement benefit plans:
Change in unrealized (gain) loss on cash flow hedges		(1)	25	1	44
Change in unrealized income on equity investments		0	77	0	70
Change in marketable securities		0	0	1	(2)
Total		$ (1)	$ 102	$ 2	$ 112
[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	1 Months Ended	3 Months Ended
	Jun. 30, 2014	Jun. 30, 2015	Jun. 11, 2014	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

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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Net income attributable to common shareholders	$ 638	$ 522	$ 1,331	$ 612
Average common shares outstanding — basic	863	860	862	860
Potentially dilutive effect of stock options, performance share awards and restricted stock	3	4	4	3
Average common shares outstanding — diluted	866	864	866	863

Earnings Per Share and Equity96

Earnings Per Share and Equity - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Jun. 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		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	13,000,000	15,000,000	16,000,000

Commitments and Contingencies -

Commitments and Contingencies - Energy Commitments (Details) $ in Millions		Jun. 30, 2015USD ($)
Exelon Generation Co L L C [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Total		$ 1,893
2,015		283
2,016		583
2,017		410
2,018		185
2,019		130
Thereafter		302
Exelon Generation Co L L C [Member] | Net Capacity Purchases [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Total	[1]	1,165
2,015	[1]	218
2,016	[1]	280
2,017	[1]	207
2,018	[1]	96
2,019	[1]	101
Thereafter	[1]	263
Exelon Generation Co L L C [Member] | Power Purchases [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Total	[2]	617
2,015	[2]	58
2,016	[2]	288
2,017	[2]	187
2,018	[2]	72
2,019	[2]	11
Thereafter	[2]	1
Exelon Generation Co L L C [Member] | Transmission Rights Purchases [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Total	[3]	111
2,015	[3]	7
2,016	[3]	15
2,017	[3]	16
2,018	[3]	17
2,019	[3]	18
Thereafter	[3]	38
Exelon Generation Co L L C [Member] | CapacityOffsets [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
2,015		75
2,016		146
2,017		149
2,018		150
2,019		151
Operating Leases, Future Minimum Payments Receivable [Abstract]
Thereafter		604
Commonwealth Edison Co [Member] | Energy Supply Procurement [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Total	[4]	697
2,015	[4]	251
2,016	[4]	262
2,017	[4]	163
2,018	[4]	21
2,019	[4]	0
Thereafter	[4]	0
Commonwealth Edison Co [Member] | Renewable Energy Including Renewable Energy Credits [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Total	[5]	1,481
2,015	[5]	38
2,016	[5]	76
2,017	[5]	77
2,018	[5]	78
2,019	[5]	79
Thereafter	[5]	1,133
PECO Energy Co [Member] | DSP Program Electric Procurement Contracts [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Total	[6]	671
2,015	[6]	368
2,016	[6]	270
2,017	[6]	33
2,018	[6]	0
2,019	[6]	0
Thereafter	[6]	0
PECO Energy Co [Member] | Alternative Energy Credits [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Total	[7]	13
2,015	[7]	2
2,016	[7]	2
2,017	[7]	2
2,018	[7]	2
2,019	[7]	2
Thereafter	[7]	3
Baltimore Gas and Electric Company [Member] | Energy Supply Procurement [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Total	[8]	1,389
2,015	[8]	462
2,016	[8]	675
2,017	[8]	252
2,018	[8]	0
2,019	[8]	0
Thereafter	[8]	0
Baltimore Gas and Electric Company [Member] | Curtailment Services [Member]
Unrecorded Unconditional Purchase Obligation, Fiscal Year Maturity [Abstract]
Total	[9]	95
2,015	[9]	20
2,016	[9]	34
2,017	[9]	29
2,018	[9]	12
2,019	[9]	$ 0
[1]	Net capacity purchases include PPAs and other capacity contracts including those that are accounted for as operating leases. Amounts presented in the commitments represent Generation’s expected payments under these arrangements at June 30, 2015, net of fixed capacity payments expected to be received ("capacity offsets") by Generation under contracts to resell such acquired capacity to third parties under long-term capacity sale contracts. As of June 30, 2015, capacity offsets were $75 million, $146 million, $149 million, $150 million, $151 million, and $604 million for years 2015, 2016, 2017, 2018, 2019, and thereafter, respectively. Expected payments include certain fixed capacity charges which may be reduced based on plant availability.
[2]	The table excludes renewable energy purchases that are contingent in nature.
[3]	Transmission rights purchases include estimated commitments for additional transmission rights that will be required to fulfill firm sales contracts.
[4]	ComEd entered into various contracts for the procurement of electricity that started to expire in 2012, and will continue to expire through 2018. ComEd is permitted to recover its electric supply procurement costs from retail customers with no mark-up. As of June 30, 2015, ComEd has completed the ICC-approved procurement process for a portion of its energy requirements through the periods ending May 31, 2015, 2016 and 2017.
[5]	Primarily related to ComEd 20-year contracts for renewable energy and RECs that began in June 2012. ComEd is permitted to recover its renewable energy and REC costs from retail customers with no mark-up. The commitments represent the maximum settlements with suppliers for renewable energy and RECs under the existing contract terms.
[6]	PECO entered into various contracts for the procurement of electric supply to serve its default service customers that expire between 2015 and 2017. PECO is permitted to recover its electric supply procurement costs from default service customers with no mark-up in accordance with its PAPUC-approved DSP Programs. See Note 5 — Regulatory Matters for additional information.
[7]	PECO is subject to requirements related to the use of alternative energy resources established by the AEPS Act. See Note 3 — Regulatory Matters of the Exelon 2014 Form 10-K for additional information.
[8]	BGE entered into various contracts for the procurement of electricity that expire between 2015 through 2017. The cost of power under these contracts is recoverable under MDPSC approved fuel clauses. See Note 3 — Regulatory Matters of the Exelon 2014 10-K for additional information.
[9]	BGE has entered into various contracts with curtailment services providers related to transactions in PJM’s capacity market. See Note 3 —Regulatory Matters of the Exelon 2014 Form 10-K for additional information.

Commitments and Contingencies98

Commitments and Contingencies - Fuel Purchase Obligations (Details) $ in Millions	Jun. 30, 2015USD ($)
Exelon Generation Co L L C [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	$ 1,893
2,015	283
2,016	583
2,017	410
2,018	185
2,019	130
Thereafter	302
Exelon Generation Co L L C [Member] | Public Utilities, Inventory, Fuel [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	8,884
2,015	726
2,016	1,129
2,017	1,078
2,018	969
2,019	880
Thereafter	4,102
PECO Energy Co [Member] | Public Utilities, Inventory, Fuel [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	375
2,015	65
2,016	107
2,017	66
2,018	46
2,019	20
Thereafter	71
Baltimore Gas and Electric Company [Member] | Public Utilities, Inventory, Fuel [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	622
2,015	52
2,016	103
2,017	92
2,018	69
2,019	61
Thereafter	$ 245

Commitments and Contingencies99

Commitments and Contingencies - Other Purchase Obligations (Details) $ in Millions		Jun. 30, 2015USD ($)
Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total		$ 1,422
2,015		342
2,016		421
2,017		220
2,018		77
2,019		80
Thereafter		282
Exelon Generation Co L L C [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total		1,893
2,015		283
2,016		583
2,017		410
2,018		185
2,019		130
Thereafter		302
Exelon Generation Co L L C [Member] | Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	[1],[2]	339
2,015	[1],[2]	79
2,016	[1],[2]	95
2,017	[1],[2]	46
2,018	[1],[2]	33
2,019	[1],[2]	24
Thereafter	[1],[2]	62
Commonwealth Edison Co [Member] | Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	[3]	356
2,015	[3]	153
2,016	[3]	166
2,017	[3]	8
2,018	[3]	7
2,019	[3]	7
Thereafter	[3]	15
PECO Energy Co [Member] | Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	[3]	21
2,015	[3]	5
2,016	[3]	5
2,017	[3]	2
2,018	[3]	2
2,019	[3]	2
Thereafter	[3]	5
Baltimore Gas and Electric Company [Member] | Other Purchase Obligations [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Total	[3]	302
2,015	[3]	75
2,016	[3]	116
2,017	[3]	111
2,018	[3]	0
2,019	[3]	0
Thereafter	[3]	$ 0
[1]	Purchase obligations do not include commitments related to construction contracts. See Construction Commitments section below for additional information.
[2]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk2MjBhNWQ1NDg2YjQxZmY5MWFlODE4Y2Q3NTY3MjBmfFRleHRTZWxlY3Rpb246QzBFM0E3QjBFQTJBNUYxRTlBMkQzNzVFOUNEQjM3NkIM}
[3]	Purchase obligations include commitments related to smart meter installation. See Note 5 — Regulatory Matters for additional information.

Commitments and Contingencie100

Commitments and Contingencies - Commitments Narrative (Details) - Unconditional Purchase Obligation, Category of Goods or Services Acquired [Domain] - Accrual For Environmental Loss Contingencies Material Components [Domain] - USD ($)	3 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Mar. 31, 2014	Jun. 30, 2012
Guarantor Obligations [Line Items]
Accrued environmental liabilities	$ 337,000,000	$ 347,000,000
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Accrued environmental liabilities	63,000,000	63,000,000
2,016	583,000,000
2,015	283,000,000
2,018	185,000,000
Minimum future operating lease payments due in one year	0
Minimum future operating lease payments due in three years	12,000,000
Minimum future operating lease payments due in four years	13,000,000
Minimum future operating lease payments due in five years	13,000,000
Minimum future operating lease payments due beyond five years	285,000,000
Other Commitment	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
Exelon Generation Co L L C [Member] | Combine-cycle Turbine Units [Member]
Guarantor Obligations [Line Items]
Other Commitment	736,000,000
Exelon Generation Co L L C [Member] | Fair Wind Project [Member]
Guarantor Obligations [Line Items]
Other Commitment	16,000,000
Exelon Generation Co L L C [Member] | Sendero Wind Project [Member]
Guarantor Obligations [Line Items]
Other Commitment	49,000,000
Exelon Generation Co L L C [Member] | AGE Biomass project [Member]
Guarantor Obligations [Line Items]
Other Commitment	170,000,000
Baltimore Gas and Electric Company [Member]
Guarantor Obligations [Line Items]
Accrued environmental liabilities	3,000,000	$ 1,000,000
Business Acquisition, Direct Investment With State And Local Governments Due To Settlement					$ 1,000,000,000
Loss Contingency, Estimate of Possible Loss	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
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
Equity Method Investments [Member] | Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
2,016	254,000,000
2,015	77,000,000
2,018	$ 7,000,000

Commitments and Contingencie101

Commitments and Contingencies - Schedule of Equity Investment Commitments (Details) - Jun. 30, 2015 - Exelon Generation Co L L C [Member] - USD ($) $ in Millions	Total
Guarantor Obligations [Line Items]
2,015	$ 283
2,016	583
2,017	410
2,018	185
2,019	130
Total	1,893
Equity Method Investments [Member]
Guarantor Obligations [Line Items]
2,015	77
2,016	254
2,017	23
2,018	7
2,019	2
Total	363
Long-term Purchase Commitment, Amount	$ 20

Commitments and Contingencie102

Commitments and Contingencies - Schedule of Commercial Commitments (Details) - Jun. 30, 2015 - USD ($) $ in Millions		Total
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		$ 10,509
Underwriting Discount	[1]	60
Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	[2]	1,568
Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	[3]	5,824
Estimated net exposure for commercial transaction obligations		674
Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	[4]	3,057
Exelon Generation Co L L C [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		7,674
Exelon Generation Co L L C [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	[2]	1,502
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	[5]	3,115
Estimated net exposure for commercial transaction obligations		460
Exelon Generation Co L L C [Member] | Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	[4]	3,057
Commonwealth Edison Co [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		221
Commonwealth Edison Co [Member] | Financial Standby Letter of Credit [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	[2]	18
Commonwealth Edison Co [Member] | Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	[6]	203
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	[2]	22
PECO Energy Co [Member] | Guarantees Other Than Letters Of Credit and Nuclear Insurance Premiums [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	[7]	188
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	[2]	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	[8]	263
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]	Represents the underwriters discount for Exelon’s forward equity transaction. See Note 17 — Common Stock for further details of the equity securities offering.
[2]	Non-debt letters of credit maintained to provide credit support for certain transactions as requested by third parties.
[3]	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 $674 million at June 30, 2015, which represents the total amount Exelon could be required to fund based on June 30, 2015 market prices.
[4]	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.
[5]	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 $460 million at June 30, 2015, which represents the total amount Generation could be required to fund based on June 30, 2015 market prices.
[6]	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.
[7]	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.
[8]	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 Contingencie103

Commitments and Contingencies - Contingencies Narrative (Details) - Jun. 30, 2015 $ in Millions		USD ($)reactor
Commitments And Contingencies Additional Narrative Information [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		$ 10,509
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		7,674
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	[1]	$ 3,057
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	[1]	$ 3,057
[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 Contingencie104

Commitments and Contingencies - Environmental Issues Narrative (Details) $ in Millions	Apr. 12, 2012Defendant	Feb. 28, 2012Defendant	Jan. 31, 2015USD ($)	Oct. 31, 2007USD ($)	Jun. 30, 2015USD ($)MGPSite	Jun. 30, 2015USD ($)Principle_responsible_partyMGPSite	Dec. 31, 2014USD ($)	Sep. 30, 2014USD ($)
Accrual For Environmental Loss Contingencies [Line Items]
Net investment in long-term direct financing leases					$ 344	$ 344	$ 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
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
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					13	13
Increase (decrease) in the value of the asbestos liability reserve					1
Loss Contingency, Estimate of Possible Loss								$ 105
Cotter Corporation [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Loss Contingency, Number of Defendants | Defendant	16	13
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 Contingencie105

Commitments and Contingencies - Litigation and Regulatory Matters (Details)	Jul. 11, 2011Customer	Jun. 30, 2015USD ($)claimantOpen_claim	Jun. 30, 2015USD ($)CustomerclaimantOpen_claim	Dec. 31, 2014USD ($)	Jun. 05, 2013Customer
Exelon Generation Co L L C [Member]
Asbestos Loss Contingency [Abstract]
Asbestos liability reserve		$ 97,000,000	$ 97,000,000	$ 100,000,000
Asbestos liability reserve related to open claims		$ 20,000,000	$ 20,000,000
Open asbestos liability claims | Open_claim		213	213
Asbestos liability reserve related to anticipated claims		$ 77,000,000	$ 77,000,000
Increase (decrease) in the value of the asbestos liability reserve		1,000,000
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
Telephone Consumer Protection Act Lawsuit [Abstract]
Possible Defendants Number | claimant			1,200,000
Commonwealth Edison Co [Member] | Legal Reserve [Member]
Telephone Consumer Protection Act Lawsuit [Abstract]
Accrued Liabilities		$ 5,000,000	$ 5,000,000
Commonwealth Edison Co [Member] | Maximum [Member]
Telephone Consumer Protection Act Lawsuit [Abstract]
Loss Contingency, Damages Sought, Value			1,500
Commonwealth Edison Co [Member] | Minimum [Member]
Telephone Consumer Protection Act Lawsuit [Abstract]
Loss Contingency, Damages Sought, Value			$ 500
Baltimore Gas and Electric Company [Member]
Asbestos Loss Contingency [Abstract]
Number of claimants | claimant		468	468

Commitments and Contingencie106

Commitments and Contingencies - Schedule of Accruals for Environmental Matters (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	$ 337	$ 347
Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	63	63
Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	227	238
PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	44	45
Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	3	1
Accrual For MGP Investigation And Remediation [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	267	277
Accrual For MGP Investigation And Remediation [Member] | Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	0	0
Accrual For MGP Investigation And Remediation [Member] | Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	224	235
Accrual For MGP Investigation And Remediation [Member] | PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	41	42
Accrual For MGP Investigation And Remediation [Member] | Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities	$ 2	$ 0

Supplemental Financial Infor107

Supplemental Financial Information - Narrative (Details) - PECO Energy Co [Member] - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2015	Mar. 31, 2014
Supplemental Financial Information Tables [Line Items]
Smart Grid Grant Project Capital Expenditures	$ 2
Smart Grid Grant Reimbursements	$ 3
Financing Receivable, Net		$ 16
Financing Receivable, Allowance for Credit Losses		18	$ 15
Low To Medium Risk [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Net		1	1
Risk Level, Medium [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Net		4	3
Risk Level, High [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Net		$ 13	$ 11

Supplemental Financial Infor108

Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]	$ 93		$ 68		$ 164		$ 111
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[1]	74		38		104		63
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units		(133)		172		(85)		234
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement		(96)		128		(56)		141
Net unrealized income (losses) on pledged assets				10		9		20
Regulatory offset to decommissioning trust fund-related activities	[2]	28		(204)		(78)		(299)
Total decommissioning-related activities		(34)		212		58		270
Investment income		1		7		4		8
Long-term lease income		4		10		8		17
Interest income related to uncertain income tax positions				(2)		0		7
AFUDC - equity		5		4		11		12
Gain (Loss) on Sale of Derivatives	[3]					(26)
Other Income		7		(1)		9		16
Other, net		(17)		230		64		330
Exelon Generation Co L L C [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	[1]	93		68		164		111
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	[1]	74		38		104		63
Net unrealized income (losses) on decommissioning trust funds - Regulatory Agreement Units		(133)		172		(85)		234
Net unrealized income (losses) on decommissioning trust funds - Non-Regulatory Agreement		(96)		128		(56)		141
Net unrealized income (losses) on pledged assets				10		9		20
Regulatory offset to decommissioning trust fund-related activities	[2]	28		(204)		(78)		(299)
Total decommissioning-related activities		(34)		212		58		270
Investment income		0		7		1		8
Long-term lease income		0		0		0		0
Interest income related to uncertain income tax positions				3		1		17
AFUDC - equity						0		0
Gain (Loss) on Sale of Derivatives	[3]					0
Other Income		3		(6)		2		5
Other, net		(31)		216		62		300
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		1		3
Other Income		4		5		8		7
Other, net		5		5		9		10
PECO Energy Co [Member]
Decommissioning-Related Activities [Abstract]
Investment income		(1)		(1)		(1)		(1)
Interest income related to uncertain income tax positions						0		0
AFUDC - equity		1		1		3		3
Gain (Loss) on Disposition of Assets						1
Other Income		1		1		1		1
Other, net		1		1		3		3
Baltimore Gas and Electric Company [Member]
Decommissioning-Related Activities [Abstract]
Investment income		1	[4]	2	[4]	2	[4]	4
Long-term lease income								0
Interest income related to uncertain income tax positions						0		0
AFUDC - equity		3		3		7		6
Other Income		0		0		(1)		(1)
Other, net		$ 4		$ 5		8		$ 9
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 Infor109

Supplemental Financial Information - Cash Flow (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment				$ 1,087		$ 1,015
Regulatory assets				101		117
Amortization of intangible assets, net				24		22
Amortization of energy contract assets and liabilities	[1]			0		113
Nuclear fuel	[2]			552		499
Asset retirement obligation accretion	[3]			193		159
Total depreciation, amortization and accretion				1,957		1,925
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				317		315
Gain (loss) on equity method investments		$ 0	$ 0	2		20
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions		2	0	2		0
Provision for uncollectible accounts				80		59
Stock-based compensation costs				79		68
Other Decommissioning Related Activity	[4]			(50)		(85)
Energy-related options				27	[5]	63
Amortization of regulatory asset related to debt costs				0
Amortization of rate stabilization deferral				40		33
Amortization of debt fair value adjustment				37		26
Discrete impacts from EIMA	[6]			77		9
Amortization of debt costs				35		19
Inventory Write-down				13
Tangible Asset Impairment Charges		24
Other				(4)		(2)
Total other noncash operating activities				579		473
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs				45		60
Other regulatory assets and liabilities				47		(25)
Increase (Decrease) in Deposits	[7]			242
Increase (Decrease) in Other Current Liabilities				(53)
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net				67
Other current assets and liabilities						(157)
Other noncurrent assets and liabilities						(158)
Total changes in other assets and liabilities				214		(280)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						3,400
Non Cash Licensing Agreement				95
Consolidated VIE dividend to non-controlling interest				0		(415)
Total noncash investing and financing activities				95		3,569
Indemnification Agreement [Member]
Other Non-Cash Operating Activities [Abstract]
Energy-related options						38
Exelon Generation Co L L C [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment				485		444
Regulatory assets				0		0
Amortization of intangible assets, net				24		22
Amortization of energy contract assets and liabilities	[1]			1		118
Nuclear fuel	[2]			552		499
Asset retirement obligation accretion	[3]			193		159
Total depreciation, amortization and accretion				1,255		1,242
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				133		139
Gain (loss) on equity method investments			1	3		20
Income (Loss) from Equity Method Investments, Net of Dividends or Distributions		$ 2		3
Provision for uncollectible accounts				11		8
Stock-based compensation costs				0		0
Other Decommissioning Related Activity	[4]			(50)		(85)
Energy-related options	[5]			27		63
Amortization of regulatory asset related to debt costs				0
Amortization of rate stabilization deferral				0		0
Amortization of debt fair value adjustment				6		12
Discrete impacts from EIMA				0		0
Amortization of debt costs				8		6
Inventory Write-down				13
Tangible Asset Impairment Charges			$ 86
Other				(5)		0
Total other noncash operating activities				134		139
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	[7]			242
Increase (Decrease) in Other Current Liabilities				(39)
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net				0
Other current assets and liabilities						13
Other noncurrent assets and liabilities						(69)
Total changes in other assets and liabilities				203		(56)
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Non cash Fair Value Adjustment for CENG						3,400
Consolidated VIE dividend to non-controlling interest				0		(415)
Total noncash investing and financing activities				0		3,438
Exelon Generation Co L L C [Member] | Indemnification Agreement [Member]
Other Non-Cash Operating Activities [Abstract]
Energy-related options						38
Commonwealth Edison Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment				312		290
Regulatory assets				40		57
Total depreciation, amortization and accretion				352		347
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				103		96
Provision for uncollectible accounts				35		(8)
Stock-based compensation costs				0
Energy-related options	[5]					0
Amortization of regulatory asset related to debt costs				0
Discrete impacts from EIMA	[6]			77		9
Amortization of debt costs				2		(3)
Inventory Write-down				0
Other				5		5
Total other noncash operating activities				222		99
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs				10		61
Other regulatory assets and liabilities				26		(30)
Increase (Decrease) in Deposits				0
Increase (Decrease) in Other Current Liabilities				3
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net				14
Other current assets and liabilities						(5)
Other noncurrent assets and liabilities						22
Total changes in other assets and liabilities				25		48
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Indemnification of like-kind exchange position				45		112
Total noncash investing and financing activities				3		2
Commonwealth Edison Co [Member] | Indemnification Agreement [Member]
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Indemnification of like-kind exchange position	[8]			3		2
PECO Energy Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment				119		112
Regulatory assets				12		5
Total depreciation, amortization and accretion				131		117
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				19		21
Gain (loss) on equity method investments						0
Provision for uncollectible accounts				24		28
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						0
Amortization of debt fair value adjustment						0
Discrete impacts from EIMA						0
Amortization of debt costs				1		1
Inventory Write-down				0
Other				1		0
Total other noncash operating activities				45		50
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs				27		(6)
Other regulatory assets and liabilities				(13)		(13)
Increase (Decrease) in Deposits				0
Increase (Decrease) in Other Current Liabilities	[9]			(74)
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net				0
Other current assets and liabilities	[9]					(89)
Other noncurrent assets and liabilities						(6)
Total changes in other assets and liabilities				(60)		(114)
Baltimore Gas and Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment				143		142
Regulatory assets				49		55
Total depreciation, amortization and accretion				192		197
Other Non-Cash Operating Activities [Abstract]
Pension and Other Postretirement Benefit Expense				33		33
Gain (loss) on equity method investments						0
Provision for uncollectible accounts				11		30
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				40		33
Amortization of debt fair value adjustment						0
Discrete impacts from EIMA						0
Amortization of debt costs				1		1
Inventory Write-down				0
Other				(9)		(8)
Total other noncash operating activities				76		89
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs				8		8
Other regulatory assets and liabilities				(18)		(49)
Increase (Decrease) in Deposits				0
Increase (Decrease) in Other Current Liabilities				60
Increase (Decrease) in Other Noncurrent Assets and Liabilities, Net				(1)
Other current assets and liabilities						51
Other noncurrent assets and liabilities						(2)
Total changes in other assets and liabilities				51		$ 8
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Indemnification of like-kind exchange position				$ 0
[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 recalled from ISOs/RTOs and replaced with letters of credit.
[8]	See Note 12 — Income Taxes for discussion of the like-kind exchange tax position
[9]	Relates primarily to prepaid utility taxes.

Supplemental Financial Infor110

Supplemental Financial Information - Balance Sheet (Details) - USD ($) $ in Millions		6 Months Ended		12 Months Ended
		Jun. 30, 2015		Dec. 31, 2014		Mar. 31, 2014
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		$ 15,553	[1]	$ 14,742	[2]
Accounts receivable, net
Allowance for uncollectible accounts		323		311
Exelon Generation Co L L C [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		8,146	[1]	7,612	[2]
Accounts receivable, net
Allowance for uncollectible accounts		67		60
Accumulated amortization of nuclear fuel		2,804		2,673
Commonwealth Edison Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		3,571		3,432
Accounts receivable, net
Allowance for uncollectible accounts		95		84
PECO Energy Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		3,028		2,917
Accounts receivable, net
Allowance for uncollectible accounts	[3]	101		100
Financing Receivable, Allowance for Credit Losses		18				$ 15
CurrentFinancingReceivableAllowanceForCreditLosses		9		7
Baltimore Gas and Electric Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		2,928		2,868
Accounts receivable, net
Allowance for uncollectible accounts		$ 60		$ 67
[1]	Includes accumulated amortization of nuclear fuel in the reactor core of $2,804 million.
[2]	Includes accumulated amortization of nuclear fuel in the reactor core of $2,673 million.
[3]	Includes an allowance for uncollectible accounts of $9 million and $7 million at June 30, 2015 and December 31, 2014, respectively, related to PECO's current installment plan receivables described below.

Segment Information - Narrative

Segment Information - Narrative (Details)	6 Months Ended
	Jun. 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				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014		Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues		$ 6,514	[1]	$ 6,024	[1]	$ 15,345	[2]	$ 13,261	[2]
Net income (loss)		633		557		1,372		651
Operating revenues from affiliates		1	[3]	0	[3]	3		0
Assets		92,213				92,213				$ 86,814
Operating Segments [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenues		4,232	[1]	3,789	[1]	10,074	[2],[4],[5]	8,179	[2],[4],[5]
Net income (loss)		390		372		875	[4],[5]	188	[4],[5]
Operating revenues from affiliates		152	[3]	201	[3]	362	[4],[5]	517	[4],[5]
Assets		45,125				45,125				45,348
Utility Taxes		24		21		51		45
Operating Segments [Member] | Commonwealth Edison Co [Member]
Segment Reporting Information [Line Items]
Revenues		1,148	[1]	1,128	[1]	2,333	[2]	2,262	[2]
Net income (loss)		99		111		189		209
Operating revenues from affiliates		1	[3]	0	[3]	2		1
Assets		25,961				25,961				25,392
Utility Taxes		55		56		117		119
Operating Segments [Member] | PECO Energy Co [Member]
Segment Reporting Information [Line Items]
Revenues		661	[1]	656	[1]	1,646	[2]	1,649	[2]
Net income (loss)		70		84		209		173
Operating revenues from affiliates		0	[3]	0	[3]	1		1
Assets		10,126				10,126				9,943
Utility Taxes		32		30		67		65
Operating Segments [Member] | Baltimore Gas and Electric Company [Member]
Segment Reporting Information [Line Items]
Revenues		628	[1]	653	[1]	1,664	[2]	1,707	[2]
Net income (loss)		47		19		157		106
Operating revenues from affiliates		1	[3]	2	[3]	8		18
Assets		8,017				8,017				8,078
Utility Taxes		21		19		44		43
Operating Segments [Member] | PECO Energy Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		49		49		112		137
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		97		87		235		207
Operating Segments [Member] | Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		6		65		15		173
Other Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues		340	[1],[6]	329	[1],[6]	657	[2],[7]	619	[2],[7]
Net income (loss)		28	[6]	(29)	[6]	(55)	[7]	(25)	[7]
Operating revenues from affiliates		340	[3],[6]	328	[3],[6]	656	[7]	618	[7]
Assets	[6]	14,526				14,526				9,794
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		0
Intersegment Eliminations [Member] | Segment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues		(495)	[1]	(531)	[1]	(1,029)	[2]	(1,155)	[2]
Net income (loss)		(1)		0		(3)		0
Operating revenues from affiliates		(493)	[3]	$ (531)	[3]	(1,026)		$ (1,155)
Assets		$ (11,542)				$ (11,542)				$ (11,741)
[1]	(c)For the three months ended June 30, 2015 and 2014, utility taxes of $24 million and $21 million, respectively, are included in revenues and expenses for Generation. For the three months ended June 30, 2015 and 2014, utility taxes of $55 million and $56 million, respectively, are included in revenues and expenses for ComEd. For the three months ended June 30, 2015 and 2014, utility taxes of $32 million and $30 million, respectively, are included in revenues and expenses for PECO. For the three months ended June 30, 2015 and 2014, utility taxes of $21 million and $19 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 six months ended June 30, 2015 include revenue from sales to PECO of $112 million and sales to BGE of $235 million in the Mid-Atlantic region, and sales to ComEd of $15 million in the Midwest. For the six months ended June 30, 2014, intersegment revenues for Generation include revenue from sales to PECO of $137 million and sales to BGE of $207 million in the Mid-Atlantic region, and sales to ComEd of $173 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 six months ended June 30, 2015 and 2014, utility taxes of $51 million and $45 million, respectively, are included in revenues and expenses for Generation. For the six months ended June 30, 2015 and 2014, utility taxes of $117 million and $119 million, respectively, are included in revenues and expenses for ComEd. For the six months ended June 30, 2015 and 2014, utility taxes of $67 million and $65 million, respectively, are included in revenues and expenses for PECO. For the six months ended June 30, 2015 and 2014, utility taxes of $44 million and $43 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				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014
Segment Reporting Information [Line Items]
Revenues		$ 6,514	[1]	$ 6,024	[1]	$ 15,345	[2]	$ 13,261	[2]
Revenue from Related Parties		1	[3]	0	[3]	3		0
Net income (loss)		633		557		1,372		651
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Unrealized Gain (Loss) on Commodity Contracts		25		(83)		179		(843)
Revenues		4,232		3,789		10,074		8,179
Revenue from Related Parties		153		201		365		535
Net income (loss)		390		372		875		188
Amortization of Intangible Assets		17		88		(22)		180
Exelon Generation Co L L C [Member] | Sales Revenue, Goods, Net [Member]
Segment Reporting Information [Line Items]
Unrealized Gain (Loss) on Commodity Contracts		235		(14)		(397)		744
Amortization of Intangible Assets		14		50		24		92
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		0
Segment Elimination [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(495)	[1]	(531)	[1]	(1,029)	[2]	(1,155)	[2]
Revenue from Related Parties		(493)	[3]	(531)	[3]	(1,026)		(1,155)
Net income (loss)		(1)		0		(3)		0
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues		1,346		1,277		2,859		2,695
Generation Mid Atlantic [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		1,336		1,272		2,853		2,713
Generation Mid Atlantic [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		10		5		6		(18)
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues		1,206		981		2,482		2,251
Generation Midwest [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		1,205		981		2,480		2,239
Generation Midwest [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		1		0		2		12
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues		367		212		1,226		761
Generation New England [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		366		211		1,224		756
Generation New England [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		1		1		2		5
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues		218		194		528		381
Generation New York [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		222		194		532		384
Generation New York [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(4)		0		(4)		(3)
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues		192		197		372		440
Generation ERCOT [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		194		198		376		441
Generation ERCOT [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(2)		(1)		(4)		(1)
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues		289		308		503		649
Generation Other Regions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		294		314		506		648
Generation Other Regions [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(5)		(6)		(3)		1
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues		3,618		3,169		7,970		7,177
Generation Reportable Segments Total [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	[4]	3,617		3,170		7,971		7,181
Generation Reportable Segments Total [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		1		(1)		(1)		(4)
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues		614		620		2,104		1,002
Generation All Other Segments [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		615		619	[4],[5]	2,103		998
Generation All Other Segments [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		(1)		1	[5]	1		4
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	[4]	4,232		3,789		10,074		8,179
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		4,232	[1]	3,789	[1]	10,074	[2],[6],[7]	8,179	[2],[6],[7]
Revenue from Related Parties		152	[3]	201	[3]	362	[6],[7]	517	[6],[7]
Net income (loss)		390		372		875	[6],[7]	188	[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		$ 6		$ 65		$ 15		$ 173
[1]	(c)For the three months ended June 30, 2015 and 2014, utility taxes of $24 million and $21 million, respectively, are included in revenues and expenses for Generation. For the three months ended June 30, 2015 and 2014, utility taxes of $55 million and $56 million, respectively, are included in revenues and expenses for ComEd. For the three months ended June 30, 2015 and 2014, utility taxes of $32 million and $30 million, respectively, are included in revenues and expenses for PECO. For the three months ended June 30, 2015 and 2014, utility taxes of $21 million and $19 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 $17 million decrease to revenues and an $88 million decrease to revenues for the amortization of intangible assets related to commodity contracts for the three months ended June 30, 2015 and 2014, respectively, unrealized mark-to-market gains of $25 million and losses of $83 million for the three months ended June 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 six months ended June 30, 2015 include revenue from sales to PECO of $112 million and sales to BGE of $235 million in the Mid-Atlantic region, and sales to ComEd of $15 million in the Midwest. For the six months ended June 30, 2014, intersegment revenues for Generation include revenue from sales to PECO of $137 million and sales to BGE of $207 million in the Mid-Atlantic region, and sales to ComEd of $173 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 - Genera114

Segment Information - Generation Total Revenues Net of Purchased Power and Fuel Expense (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Amortization of Intangible Assets	$ (17)		$ (88)		$ 22		$ (180)
Unrealized Gain (Loss) on Commodity Contracts	25		(83)		179		(843)
Sales Revenue, Goods, Net [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Amortization of Intangible Assets	(14)		(50)		(24)		(92)
Unrealized Gain (Loss) on Commodity Contracts	235		(14)		(397)		744
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	2,383		1,954		4,792		2,988
Generation Total Consolidated Group [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	2,383		1,954		4,792	[1]	2,988	[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	889		920		1,671		1,615
Generation Mid Atlantic [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	875	[1]	906	[1]	1,659		1,690
Generation Mid Atlantic [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	14	[1]	14		12		(75)
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	743		605		1,443		1,161
Generation Midwest [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	745	[1]	604	[1]	1,446		1,134
Generation Midwest [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	(2)		1		(3)		27
Generation New England [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	88		64		246		200
Generation New England [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	94	[1]	88	[1]	271		242
Generation New England [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	(6)		(24)		(25)		(42)
Generation New York [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	144		148		332		127
Generation New York [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	139	[1]	142	[1]	313		113
Generation New York [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	5		6		19		14
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	70		59		125		142
Generation ERCOT [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	91	[1]	117	[1]	179		272
Generation ERCOT [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	(21)		(58)		(54)		(130)
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	62		75		108		180
Generation Other Regions [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	134	[1]	157	[1]	233		307
Generation Other Regions [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	(72)		(82)		(125)		(127)
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	1,996		1,871		3,925		3,425
Generation Reportable Segments Total [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	2,078		2,014		4,101	[1]	3,758	[1]
Generation Reportable Segments Total [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	(82)		(143)		(176)		(333)
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Segment Reporting Information Revenue Net of Purchase Power And Fuel	387	[2]	83	[2]	867		(437)
Generation All Other Segments [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	305	[1],[2]	(60)	[1],[2]	691		(770)
Generation All Other Segments [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Intersegment RNF	$ 82	[2]	$ 143	[2]	$ 176		$ 333
[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 $14 million decrease to RNF and a $50 million decrease to RNF for the amortization of intangible assets related to commodity contracts for the three months ended June 30, 2015 and 2014, respectively, unrealized mark-to-market gains of $235 million and losses of $14 million for the three months ended June 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]
Regulatory Liabilities	us-gaap_RegulatoryLiabilities	$ 1