Commonwealth Edison 10-Q 31 Oct 19 2019 Q3 Quarterly report Financial data

Cover Page

Cover Page	9 Months Ended
	Sep. 30, 2019shares
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	001-16169
Entity Registrant Name	EXELON CORPORATION
Entity Tax Identification Number	23-2990190
Entity Incorporation, State or Country Code	PA
Entity Address, Address Line One	10 South Dearborn Street
Entity Address, Address Line Two	P.O. Box 805379
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60680-5379
City Area Code	(800)
Local Phone Number	483-3220
Title of 12(b) Security	Common stock, without par value
Trading Symbol	EXC
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock Shares Outstanding	972,108,865
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001109357
Amendment Flag	false
Exelon Generation Co L L C [Member]
Entity File Number	333-85496
Entity Registrant Name	EXELON GENERATION COMPANY, LLC
Entity Tax Identification Number	23-3064219
Entity Incorporation, State or Country Code	PA
Entity Address, Address Line One	300 Exelon Way
Entity Address, City or Town	Kennett Square
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19348-2473
City Area Code	(610)
Local Phone Number	765-5959
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Central Index Key	0001168165
Commonwealth Edison Co [Member]
Entity File Number	001-01839
Entity Registrant Name	COMMONWEALTH EDISON COMPANY
Entity Tax Identification Number	36-0938600
Entity Incorporation, State or Country Code	IL
Entity Address, Address Line One	440 South LaSalle Street
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60605-1028
City Area Code	(312)
Local Phone Number	394-4321
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	127,021,343
Entity Central Index Key	0000022606
PECO Energy Co [Member]
Entity File Number	000-16844
Entity Registrant Name	PECO ENERGY COMPANY
Entity Tax Identification Number	23-0970240
Entity Incorporation, State or Country Code	PA
Entity Address, Address Line One	P.O. Box 8699
Entity Address, Address Line Two	2301 Market Street
Entity Address, City or Town	Philadelphia
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19101-8699
City Area Code	(215)
Local Phone Number	841-4000
Title of 12(b) Security	Cumulative Preferred Security, Series D
Trading Symbol	EXC/28
Security Exchange Name	NYSE
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	170,478,507
Entity Central Index Key	0000078100
Baltimore Gas and Electric Company [Member]
Entity File Number	001-01910
Entity Registrant Name	BALTIMORE GAS AND ELECTRIC COMPANY
Entity Tax Identification Number	52-0280210
Entity Incorporation, State or Country Code	MD
Entity Address, Address Line One	2 Center Plaza
Entity Address, Address Line Two	110 West Fayette Street
Entity Address, City or Town	Baltimore
Entity Address, State or Province	MD
Entity Address, Postal Zip Code	21201-3708
City Area Code	(410)
Local Phone Number	234-5000
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	1,000
Entity Central Index Key	0000009466
Pepco Holdings LLC [Member]
Entity File Number	001-31403
Entity Registrant Name	PEPCO HOLDINGS LLC
Entity Tax Identification Number	52-2297449
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	701 Ninth Street, N.W.
Entity Address, City or Town	Washington, District of Columbia
Entity Address, Postal Zip Code	20068
City Area Code	(202)
Local Phone Number	872-2000
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Central Index Key	0001135971
Potomac Electric Power Company [Member]
Entity File Number	001-01072
Entity Registrant Name	POTOMAC ELECTRIC POWER COMPANY
Entity Tax Identification Number	53-0127880
Entity Incorporation, State or Country Code	DC
Entity Address, Address Line One	701 Ninth Street, N.W.
Entity Address, City or Town	Washington, District of Columbia
Entity Address, Postal Zip Code	20068
City Area Code	(202)
Local Phone Number	872-2000
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	100
Entity Central Index Key	0000079732
Delmarva Power and Light Company [Member]
Entity File Number	001-01405
Entity Registrant Name	DELMARVA POWER & LIGHT COMPANY
Entity Tax Identification Number	51-0084283
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	500 North Wakefield Drive
Entity Address, City or Town	Newark
Entity Address, State or Province	DE
Entity Address, Postal Zip Code	19702
City Area Code	(202)
Local Phone Number	872-2000
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	1,000
Entity Central Index Key	0000027879
Atlantic City Electric Company [Member]
Entity File Number	001-03559
Entity Registrant Name	ATLANTIC CITY ELECTRIC COMPANY
Entity Tax Identification Number	21-0398280
Entity Incorporation, State or Country Code	NJ
Entity Address, Address Line One	500 North Wakefield Drive
Entity Address, City or Town	Newark
Entity Address, State or Province	DE
Entity Address, Postal Zip Code	19702
City Area Code	(202)
Local Phone Number	872-2000
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	8,546,017
Entity Central Index Key	0000008192
VIRGINIA | Potomac Electric Power Company [Member]
Entity Incorporation, State or Country Code	VA
VIRGINIA | Delmarva Power and Light Company [Member]
Entity Incorporation, State or Country Code	VA

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Income (Unaudited) - USD ($) shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Operating revenues
Revenues from alternative revenue programs		$ (80)	$ (25)	$ (98)	$ (41)
Operating revenues from affiliates		0	0	0	0
Total operating revenues		8,929	9,403	26,096	27,170
Operating expenses
Operating and maintenance		2,072	2,346	6,419	7,036
Depreciation and amortization		1,083	1,105	3,237	3,284
Taxes other than income		452	469	1,316	1,342
Total operating expenses		7,559	8,252	22,703	24,036
Gain on sales of assets and businesses		(17)	(5)	19	55
Operating income		1,353	1,146	3,412	3,189
Other income and (deductions)
Interest expense, net		(403)	(387)	(1,202)	(1,119)
Interest expense to affiliates		(6)	(6)	(19)	(19)
Other, net		158	194	837	212
Total other income and (deductions)		(251)	(199)	(384)	(926)
Income before income taxes		1,102	947	3,028	2,263
Income taxes		172	137	626	262
Equity in losses of unconsolidated affiliates		(170)	(10)	(182)	(22)
Net income		760	800	2,220	1,979
Net income attributable to noncontrolling interests		(12)	67	56	121
Net income (loss) attributable to common shareholders		772	733	2,164	1,858
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost		(16)	(17)	(49)	(50)
Actuarial loss reclassified to periodic benefit cost		37	62	111	186
Pension and non-pension postretirement benefit plan valuation adjustment		6	5	(32)	22
Unrealized (loss) gain on cash flow hedges		0	0	0	12
Unrealized (loss) gain on investments in unconsolidated affiliates		5	0	1	3
Unrealized gain (loss) on foreign currency translation		(2)	2	2	(4)
Other comprehensive income		30	52	33	169
Comprehensive income		790	852	2,253	2,148
Comprehensive (loss) income attributable to noncontrolling interests		(9)	67	57	123
Comprehensive income attributable to common shareholders/membership interest		$ 799	$ 785	$ 2,196	$ 2,025
Average shares of common stock outstanding:
Basic average shares of common stock outstanding		973	968	972	967
Assumed exercise and/or distributions of stock-based awards		1	2	1	2
Diluted average shares of common stock outstanding	[1]	974	970	973	969
Earnings per average common share:
Basic earnings per average common share		$ 0.79	$ 0.76	$ 2.23	$ 1.92
Diluted earnings per average common share		$ 0.79	$ 0.76	$ 2.22	$ 1.92
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			2		3
Exelon Generation Co L L C [Member]
Operating revenues
Operating revenues from affiliates		$ 275	$ 308	$ 844	$ 979
Total operating revenues		4,774	5,278	14,280	15,368
Operating expenses
Purchased power and/or fuel from affiliates		3	3	7	10
Operating and maintenance		947	1,218	3,131	3,643
Operating and maintenance from affiliates		140	152	439	483
Depreciation and amortization		407	468	1,221	1,383
Taxes other than income		129	143	394	414
Total operating expenses		4,274	4,961	13,333	14,475
Gain on sales of assets and businesses		(18)	(6)	15	48
Operating income		482	311	962	941
Other income and (deductions)
Interest expense, net		(101)	(93)	(310)	(278)
Interest expense to affiliates		(8)	(8)	(26)	(27)
Other, net		128	179	729	164
Total other income and (deductions)		19	78	393	(141)
Income before income taxes		501	389	1,355	800
Income taxes		87	78	388	110
Equity in losses of unconsolidated affiliates		(170)	(11)	(183)	(23)
Net income		244	300	784	667
Net income attributable to noncontrolling interests		(13)	66	56	120
Net income attributable to membership interest		257	234	728	547
Other comprehensive income (loss), net of income taxes
Unrealized (loss) gain on cash flow hedges		0	0	0	12
Unrealized (loss) gain on investments in unconsolidated affiliates		5	0	1	3
Unrealized gain (loss) on foreign currency translation		(2)	2	2	(4)
Other comprehensive income		3	2	3	11
Comprehensive income		247	302	787	678
Comprehensive (loss) income attributable to noncontrolling interests		(10)	66	57	122
Comprehensive income attributable to common shareholders/membership interest		257	236	730	556
Commonwealth Edison Co [Member]
Operating revenues
Revenues from alternative revenue programs		(56)	(15)	(98)	(27)
Operating revenues from affiliates		4	4	13	23
Total operating revenues		1,583	1,598	4,342	4,508
Operating expenses
Purchased power and/or fuel from affiliates		83	123	270	421
Operating and maintenance		267	276	771	785
Operating and maintenance from affiliates		73	61	196	189
Depreciation and amortization		259	237	767	696
Taxes other than income		80	82	228	238
Total operating expenses		1,256	1,275	3,431	3,610
Gain on sales of assets and businesses		1	0	4	5
Operating income		328	323	915	903
Other income and (deductions)
Interest expense, net		(87)	(82)	(258)	(251)
Interest expense to affiliates		(4)	(3)	(10)	(10)
Other, net		8	7	27	21
Total other income and (deductions)		(83)	(78)	(241)	(240)
Income before income taxes		245	245	674	663
Income taxes		45	52	130	140
Net income		200	193	544	523
Other comprehensive income (loss), net of income taxes
Comprehensive income		200	193	544	523
PECO Energy Co [Member]
Operating revenues
Revenues from alternative revenue programs		(11)	1	(16)	2
Operating revenues from affiliates		1	2	4	5
Total operating revenues		778	757	2,333	2,275
Operating expenses
Purchased power and/or fuel from affiliates		43	34	122	94
Operating and maintenance		182	184	531	572
Operating and maintenance from affiliates		37	35	112	114
Depreciation and amortization		83	75	247	224
Taxes other than income		47	46	126	125
Total operating expenses		595	603	1,783	1,853
Gain on sales of assets and businesses		0	0	0	1
Operating income		183	154	550	423
Other income and (deductions)
Interest expense, net		(30)	(28)	(91)	(85)
Interest expense to affiliates		(3)	(4)	(9)	(11)
Other, net		4	2	11	4
Total other income and (deductions)		(29)	(30)	(89)	(92)
Income before income taxes		154	124	461	331
Income taxes		14	(2)	51	(5)
Net income		140	126	410	336
Other comprehensive income (loss), net of income taxes
Comprehensive income		140	126	410	336
Baltimore Gas and Electric Company [Member]
Operating revenues
Revenues from alternative revenue programs		(5)	(6)	11	(23)
Operating revenues from affiliates		6	6	18	18
Total operating revenues		703	731	2,327	2,369
Operating expenses
Purchased power and/or fuel from affiliates		64	68	196	195
Operating and maintenance		157	144	451	462
Operating and maintenance from affiliates		39	38	118	116
Depreciation and amortization		116	110	368	358
Taxes other than income		65	64	195	188
Total operating expenses		612	628	1,936	2,005
Gain on sales of assets and businesses		0	0	0	1
Operating income		91	103	391	365
Other income and (deductions)
Interest expense, net		(31)	(27)	(89)	(78)
Other, net		7	5	18	14
Total other income and (deductions)		(24)	(22)	(71)	(64)
Income before income taxes		67	81	320	301
Income taxes		12	18	59	59
Net income		55	63	261	242
Other comprehensive income (loss), net of income taxes
Comprehensive income		55	63	261	242
Pepco Holdings LLC [Member]
Operating revenues
Revenues from alternative revenue programs		(9)	(5)	4	7
Operating revenues from affiliates		4	3	11	11
Total operating revenues		1,380	1,361	3,700	3,688
Operating expenses
Purchased power and/or fuel from affiliates		83	82	254	268
Operating and maintenance		254	261	706	751
Operating and maintenance from affiliates		36	31	105	106
Depreciation and amortization		193	192	562	555
Taxes other than income		122	123	342	343
Total operating expenses		1,124	1,116	3,106	3,165
Operating income		256	245	594	523
Other income and (deductions)
Interest expense, net		(66)	(65)	(197)	(193)
Other, net		13	11	39	33
Total other income and (deductions)		(53)	(54)	(158)	(160)
Income before income taxes		203	191	436	363
Income taxes		14	4	25	28
Equity in losses of unconsolidated affiliates		0	0	1	1
Net income		189	187	412	336
Other comprehensive income (loss), net of income taxes
Comprehensive income attributable to common shareholders/membership interest		189	187	412	336
Potomac Electric Power Company [Member]
Operating revenues
Revenues from alternative revenue programs		(3)	(4)	10	6
Operating revenues from affiliates		2	2	5	5
Total operating revenues		642	628	1,748	1,708
Operating expenses
Purchased power and/or fuel from affiliates		65	46	188	143
Operating and maintenance		85	84	208	216
Operating and maintenance from affiliates		50	52	156	167
Depreciation and amortization		95	99	281	286
Taxes other than income		104	104	286	288
Total operating expenses		515	516	1,444	1,454
Operating income		127	112	304	254
Other income and (deductions)
Interest expense, net		(33)	(32)	(100)	(96)
Other, net		9	7	22	23
Total other income and (deductions)		(24)	(25)	(78)	(73)
Income before income taxes		103	87	226	181
Income taxes		5	(2)	9	7
Net income		98	89	217	174
Other comprehensive income (loss), net of income taxes
Comprehensive income		98	89	217	174
Delmarva Power and Light Company [Member]
Operating revenues
Revenues from alternative revenue programs		(6)	0	(6)	5
Operating revenues from affiliates		1	2	5	6
Total operating revenues		319	328	987	1,001
Operating expenses
Purchased power and/or fuel from affiliates		14	26	50	103
Operating and maintenance		43	44	127	137
Operating and maintenance from affiliates		37	38	113	119
Depreciation and amortization		46	47	138	135
Taxes other than income		15	15	43	43
Total operating expenses		268	277	820	859
Operating income		51	51	167	142
Other income and (deductions)
Interest expense, net		(15)	(15)	(45)	(42)
Other, net		2	2	10	7
Total other income and (deductions)		(13)	(13)	(35)	(35)
Income before income taxes		38	38	132	107
Income taxes		5	5	16	17
Net income		33	33	116	90
Other comprehensive income (loss), net of income taxes
Comprehensive income		33	33	116	90
Atlantic City Electric Company [Member]
Operating revenues
Revenues from alternative revenue programs		1	(1)	0	(4)
Operating revenues from affiliates		1	1	2	2
Total operating revenues		419	406	966	981
Operating expenses
Purchased power and/or fuel from affiliates		3	10	16	21
Operating and maintenance		54	52	142	146
Operating and maintenance from affiliates		32	33	99	104
Depreciation and amortization		43	38	114	107
Taxes other than income		1	1	4	4
Total operating expenses		340	322	838	847
Operating income		79	84	128	134
Other income and (deductions)
Interest expense, net		(15)	(16)	(44)	(48)
Other, net		1	1	5	2
Total other income and (deductions)		(14)	(15)	(39)	(46)
Income before income taxes		65	69	89	88
Income taxes		2	8	2	12
Net income		63	61	87	76
Other comprehensive income (loss), net of income taxes
Comprehensive income		63	61	87	76
Generation commodities and services
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,499	4,971	13,436	14,387
Operating expenses
Purchased power and/or fuel		2,648	2,977	8,142	8,542
Generation commodities and services | Exelon Generation Co L L C [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,499	4,970	13,436	14,389
Operating expenses
Purchased power and/or fuel		2,648	2,977	8,141	8,542
Rate-regulated utility revenues
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,510	4,457	12,758	12,824
Operating expenses
Purchased power and/or fuel		1,304	1,355	3,589	3,832
Electricity, US Regulated | Commonwealth Edison Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		1,635	1,609	4,427	4,512
Operating expenses
Purchased power and/or fuel		494	496	1,199	1,281
Electricity, US Regulated | PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		726	697	1,914	1,886
Operating expenses
Purchased power and/or fuel		185	215	461	576
Electricity, US Regulated | Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		623	652	1,814	1,847
Operating expenses
Purchased power and/or fuel		159	183	480	510
Electricity, US Regulated | Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		1,365	1,340	3,570	3,541
Operating expenses
Purchased power and/or fuel		428	415	1,086	1,077
Electricity, US Regulated | Potomac Electric Power Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		643	630	1,733	1,697
Operating expenses
Purchased power and/or fuel		116	131	325	354
Electricity, US Regulated | Delmarva Power and Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		304	302	872	861
Operating expenses
Purchased power and/or fuel		105	96	298	258
Electricity, US Regulated | Atlantic City Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		417	406	964	983
Operating expenses
Purchased power and/or fuel		207	188	463	465
Natural Gas, US Regulated | PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		62	57	431	382
Operating expenses
Purchased power and/or fuel		18	14	184	148
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		79	79	484	527
Operating expenses
Purchased power and/or fuel		12	21	128	176
Natural Gas, US Regulated | Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		20	23	115	129
Operating expenses
Purchased power and/or fuel		8	12	51	65
Natural Gas, US Regulated | Delmarva Power and Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		20	24	116	129
Operating expenses
Purchased power and/or fuel		$ 8	$ 11	$ 51	$ 64
[1]	The number of stock options not included in the calculation of diluted common shares outstanding due to their antidilutive effect was immaterial for the three and nine months ended September 30, 2019 and approximately 2 million and 3 million for the three and nine months ended September 30, 2018 , respectively.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities
Net income	$ 2,220	$ 1,979
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	4,393	4,511
Asset impairments	174	49
Gain on sales of assets and businesses	(15)	(55)
Deferred income taxes and amortization of investment tax credits	412	97
Net fair value changes related to derivatives	96	67
Net realized and unrealized gains on NDT funds	(467)	(21)
Other non-cash operating activities	460	804
Changes in assets and liabilities:
Accounts receivable	445	(167)
Inventories	(94)	(24)
Accounts payable and accrued expenses	(671)	84
Option premiums received (paid), net	13	(36)
Collateral (posted) received, net	(254)	222
Income taxes	143	166
Pension and non-pension postretirement benefit contributions	(377)	(362)
Other assets and liabilities	(1,079)	(639)
Net cash flows provided by operating activities	5,399	6,675
Cash flows from investing activities
Capital expenditures	(5,259)	(5,497)
Proceeds from NDT fund sales	8,443	6,379
Investment in NDT funds	(8,437)	(6,553)
Acquisition of assets and businesses, net	0	(57)
Proceeds from sales of assets and businesses	17	90
Other investing activities	21	29
Net cash flows used in investing activities	(5,215)	(5,609)
Cash flows from financing activities
Changes in short-term borrowings	430	(218)
Proceeds from short-term borrowings with maturities greater than 90 days	0	126
Repayments on short-term borrowings with maturities greater than 90 days	(125)	(1)
Issuance of long-term debt	1,576	2,664
Retirement of long-term debt	(644)	(1,480)
Dividends paid on common stock	(1,055)	(999)
Proceeds from employee stock plans	94	67
Other financing activities	(63)	(94)
Net cash flows provided by (used in) financing activities	213	65
Increase (Decrease) in cash, cash equivalents and restricted cash	397	1,131
Cash, cash equivalents and restricted cash at beginning of period	1,781	1,190
Cash, cash equivalents and restricted cash at end of period	2,178	2,321
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(96)	(175)
Increase in PPE related to ARO update	344	67
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	784	667
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	2,377	2,608
Asset impairments	174	49
Gain on sales of assets and businesses	(15)	(48)
Deferred income taxes and amortization of investment tax credits	201	(278)
Net fair value changes related to derivatives	102	73
Net realized and unrealized gains on NDT funds	(467)	(21)
Other non-cash operating activities	(95)	187
Changes in assets and liabilities:
Accounts receivable	395	126
Receivables from and payables to affiliates, net	(12)	(7)
Inventories	(36)	(10)
Accounts payable and accrued expenses	(428)	(59)
Option premiums received (paid), net	13	(36)
Collateral (posted) received, net	(292)	228
Income taxes	327	220
Pension and non-pension postretirement benefit contributions	(165)	(134)
Other assets and liabilities	(390)	(154)
Net cash flows provided by operating activities	2,473	3,411
Cash flows from investing activities
Capital expenditures	(1,282)	(1,660)
Proceeds from NDT fund sales	8,443	6,379
Investment in NDT funds	(8,437)	(6,553)
Acquisition of assets and businesses, net	0	(57)
Proceeds from sales of assets and businesses	17	90
Other investing activities	(6)	(5)
Net cash flows used in investing activities	(1,265)	(1,806)
Cash flows from financing activities
Issuance of long-term debt	41	14
Retirement of long-term debt	(196)	(100)
Changes in Exelon/PHI intercompany money pool	(100)	(54)
Distributions to member	(674)	(688)
Contributions from member	0	54
Other financing activities	(37)	(46)
Net cash flows provided by (used in) financing activities	(966)	(820)
Increase (Decrease) in cash, cash equivalents and restricted cash	242	785
Cash, cash equivalents and restricted cash at beginning of period	903	554
Cash, cash equivalents and restricted cash at end of period	1,145	1,339
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(24)	(226)
Increase in PPE related to ARO update	342	47
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	544	523
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	767	696
Deferred income taxes and amortization of investment tax credits	115	214
Other non-cash operating activities	180	187
Changes in assets and liabilities:
Accounts receivable	(38)	(190)
Receivables from and payables to affiliates, net	(27)	8
Inventories	(16)	4
Accounts payable and accrued expenses	(132)	(38)
Collateral (posted) received, net	43	(10)
Income taxes	25	(65)
Pension and non-pension postretirement benefit contributions	(71)	(41)
Other assets and liabilities	(245)	(170)
Net cash flows provided by operating activities	1,145	1,118
Cash flows from investing activities
Capital expenditures	(1,413)	(1,540)
Other investing activities	25	22
Net cash flows used in investing activities	(1,388)	(1,518)
Cash flows from financing activities
Changes in short-term borrowings	387	0
Issuance of long-term debt	400	1,350
Retirement of long-term debt	(300)	(840)
Contributions from parent	187	387
Dividends paid on common stock	(380)	(345)
Other financing activities	(10)	(16)
Net cash flows provided by (used in) financing activities	284	536
Increase (Decrease) in cash, cash equivalents and restricted cash	41	136
Cash, cash equivalents and restricted cash at beginning of period	330	144
Cash, cash equivalents and restricted cash at end of period	371	280
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(52)	(28)
PECO Energy Co [Member]
Cash flows from operating activities
Net income	410	336
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	247	224
Gain on sales of assets and businesses	0	(1)
Deferred income taxes and amortization of investment tax credits	6	5
Other non-cash operating activities	28	41
Changes in assets and liabilities:
Accounts receivable	46	(85)
Receivables from and payables to affiliates, net	(12)	1
Inventories	(3)	(13)
Accounts payable and accrued expenses	(32)	(1)
Income taxes	(15)	(16)
Pension and non-pension postretirement benefit contributions	(26)	(25)
Other assets and liabilities	(111)	26
Net cash flows provided by operating activities	538	492
Cash flows from investing activities
Capital expenditures	(675)	(615)
Other investing activities	7	6
Net cash flows used in investing activities	(668)	(609)
Cash flows from financing activities
Issuance of long-term debt	325	700
Retirement of long-term debt	0	(500)
Contributions from parent	174	71
Dividends paid on common stock	(268)	(300)
Other financing activities	(6)	(22)
Net cash flows provided by (used in) financing activities	225	(51)
Increase (Decrease) in cash, cash equivalents and restricted cash	95	(168)
Cash, cash equivalents and restricted cash at beginning of period	135	275
Cash, cash equivalents and restricted cash at end of period	230	107
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	42	4
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	261	242
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	368	358
Deferred income taxes and amortization of investment tax credits	66	82
Other non-cash operating activities	63	42
Changes in assets and liabilities:
Accounts receivable	110	72
Receivables from and payables to affiliates, net	(14)	(4)
Inventories	(5)	(8)
Accounts payable and accrued expenses	(28)	(3)
Collateral (posted) received, net	(5)	1
Income taxes	(43)	(48)
Pension and non-pension postretirement benefit contributions	(45)	(50)
Other assets and liabilities	(65)	(9)
Net cash flows provided by operating activities	663	675
Cash flows from investing activities
Capital expenditures	(842)	(667)
Other investing activities	4	8
Net cash flows used in investing activities	(838)	(659)
Cash flows from financing activities
Changes in short-term borrowings	(35)	(77)
Issuance of long-term debt	400	300
Contributions from parent	104	18
Dividends paid on common stock	(169)	(157)
Other financing activities	(7)	(2)
Net cash flows provided by (used in) financing activities	293	82
Increase (Decrease) in cash, cash equivalents and restricted cash	118	98
Cash, cash equivalents and restricted cash at beginning of period	13	18
Cash, cash equivalents and restricted cash at end of period	131	116
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	6	44
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income	412	336
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	562	555
Deferred income taxes and amortization of investment tax credits	8	50
Other non-cash operating activities	122	109
Changes in assets and liabilities:
Accounts receivable	(64)	(89)
Receivables from and payables to affiliates, net	1	10
Inventories	(36)	0
Accounts payable and accrued expenses	0	115
Income taxes	(11)	(31)
Pension and non-pension postretirement benefit contributions	(15)	(66)
Other assets and liabilities	(102)	(144)
Net cash flows provided by operating activities	877	845
Cash flows from investing activities
Capital expenditures	(1,006)	(988)
Other investing activities	3	2
Net cash flows used in investing activities	(1,003)	(986)
Cash flows from financing activities
Changes in short-term borrowings	78	(141)
Proceeds from short-term borrowings with maturities greater than 90 days	0	125
Repayments on short-term borrowings with maturities greater than 90 days	(125)	0
Issuance of long-term debt	410	300
Retirement of long-term debt	(130)	(33)
Changes in Exelon/PHI intercompany money pool	10	10
Distributions to member	(429)	(232)
Contributions from member	283	237
Other financing activities	(5)	(6)
Net cash flows provided by (used in) financing activities	92	260
Increase (Decrease) in cash, cash equivalents and restricted cash	(34)	119
Cash, cash equivalents and restricted cash at beginning of period	186	95
Cash, cash equivalents and restricted cash at end of period	152	214
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(62)	54
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income	217	174
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	281	286
Deferred income taxes and amortization of investment tax credits	12	(5)
Other non-cash operating activities	43	42
Changes in assets and liabilities:
Accounts receivable	(49)	(36)
Receivables from and payables to affiliates, net	4	(9)
Inventories	(23)	6
Accounts payable and accrued expenses	(12)	104
Income taxes	(23)	(18)
Pension and non-pension postretirement benefit contributions	(10)	(11)
Other assets and liabilities	(55)	(137)
Net cash flows provided by operating activities	385	396
Cash flows from investing activities
Capital expenditures	(455)	(475)
Other investing activities	2	3
Net cash flows used in investing activities	(453)	(472)
Cash flows from financing activities
Changes in short-term borrowings	(28)	38
Issuance of long-term debt	260	100
Retirement of long-term debt	(118)	(8)
Contributions from parent	129	85
Dividends paid on common stock	(173)	(128)
Other financing activities	(3)	(4)
Net cash flows provided by (used in) financing activities	67	83
Increase (Decrease) in cash, cash equivalents and restricted cash	(1)	7
Cash, cash equivalents and restricted cash at beginning of period	53	40
Cash, cash equivalents and restricted cash at end of period	52	47
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(7)	15
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income	116	90
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	138	135
Deferred income taxes and amortization of investment tax credits	(2)	24
Other non-cash operating activities	21	16
Changes in assets and liabilities:
Accounts receivable	29	13
Receivables from and payables to affiliates, net	(7)	(14)
Inventories	(7)	(3)
Accounts payable and accrued expenses	3	18
Income taxes	11	0
Pension and non-pension postretirement benefit contributions	(1)	0
Other assets and liabilities	(22)	13
Net cash flows provided by operating activities	279	292
Cash flows from investing activities
Capital expenditures	(245)	(254)
Other investing activities	1	1
Net cash flows used in investing activities	(244)	(253)
Cash flows from financing activities
Changes in short-term borrowings	57	(216)
Issuance of long-term debt	0	200
Retirement of long-term debt	0	(4)
Contributions from parent	0	150
Dividends paid on common stock	(105)	(58)
Other financing activities	0	(3)
Net cash flows provided by (used in) financing activities	(48)	69
Increase (Decrease) in cash, cash equivalents and restricted cash	(13)	108
Cash, cash equivalents and restricted cash at beginning of period	24	2
Cash, cash equivalents and restricted cash at end of period	11	110
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(13)	20
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income	87	76
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	114	107
Deferred income taxes and amortization of investment tax credits	2	24
Other non-cash operating activities	21	24
Changes in assets and liabilities:
Accounts receivable	(44)	(66)
Receivables from and payables to affiliates, net	(4)	(3)
Inventories	(4)	(2)
Accounts payable and accrued expenses	27	21
Income taxes	5	(3)
Pension and non-pension postretirement benefit contributions	0	(6)
Other assets and liabilities	(18)	(12)
Net cash flows provided by operating activities	186	160
Cash flows from investing activities
Capital expenditures	(300)	(247)
Other investing activities	0	(1)
Net cash flows used in investing activities	(300)	(248)
Cash flows from financing activities
Changes in short-term borrowings	49	37
Proceeds from short-term borrowings with maturities greater than 90 days	0	125
Repayments on short-term borrowings with maturities greater than 90 days	(125)	0
Issuance of long-term debt	150	0
Retirement of long-term debt	(13)	(22)
Contributions from parent	155	0
Dividends paid on common stock	(100)	(46)
Other financing activities	(1)	0
Net cash flows provided by (used in) financing activities	115	94
Increase (Decrease) in cash, cash equivalents and restricted cash	1	6
Cash, cash equivalents and restricted cash at beginning of period	30	31
Cash, cash equivalents and restricted cash at end of period	31	37
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	$ (37)	$ 16

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Sep. 30, 2019	Dec. 31, 2018
Current Assets
Cash and cash equivalents		$ 1,683	$ 1,349
Restricted cash and cash equivalents		309	247
Accounts receivable, net
Customer		4,188	4,607
Other		1,085	1,256
Mark-to-market derivative assets, current		601	804
Unamortized energy contract assets, current		49	48
Inventories, net
Fossil fuel and emission allowances		325	334
Materials and supplies		1,458	1,351
Regulatory assets, current		1,194	1,222
Assets held for sale		18	904
Other		1,296	1,238
Total current assets		12,206	13,360
Property, plant and equipment, net		78,593	76,707
Deferred debits and other assets
Regulatory assets, noncurrent		8,122	8,237
Nuclear decommissioning trust funds		12,706	11,661
Investments		471	625
Goodwill		6,677	6,677
Mark-to-market derivative assets, noncurrent		487	452
Unamortized energy contract assets, noncurrent		353	372
Other		3,123	1,575
Total deferred debits and other assets		31,939	29,599
Total assets	[1]	122,738	119,666
Current Liabilities
Short-term borrowings		1,019	714
Long-term debt due within one year		4,248	1,349
Accounts payable		3,348	3,800
Accrued expenses		1,877	2,112
Payable to affiliates, current		5	5
Regulatory liabilities, current		400	644
Mark-to-market derivative liabilities, current		239	475
Unamortized energy contract liabilities, current		138	149
Renewable energy credit obligation		375	344
Liabilities held for sale		11	777
Other		1,425	1,035
Total current liabilities		13,085	11,404
Long-term debt		32,056	34,075
Long-term debt to financing trusts		390	390
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		12,133	11,330
Asset retirement obligations, noncurrent		10,089	9,679
Pension obligations		3,712	3,988
Non-pension postretirement benefit obligations		2,029	1,928
Spent nuclear fuel obligation		1,193	1,171
Regulatory liabilities, noncurrent		9,792	9,559
Mark-to-market derivative liabilities, noncurrent		416	479
Unamortized energy contract liabilities, noncurrent		368	463
Other		3,123	2,130
Total deferred credits and other liabilities		42,855	40,727
Total liabilities	[1]	88,386	86,596
Commitments and contingencies
Shareholders' equity
Common stock		19,238	19,116
Treasury stock, at cost		(123)	(123)
Retained earnings/Undistributed earnings		15,871	14,766
Accumulated other comprehensive loss, net		(2,963)	(2,995)
Total shareholders’ equity		32,023	30,764
Member’s equity
Noncontrolling Interests		2,329	2,306
Total equity		34,352	33,070
Total liabilities and shareholders’ equity		122,738	119,666
Variable Interest Entity, Consolidated, Assets, Pledged		9,465	9,667
Variable Interest Entity, Consolidated, Liabilities, No Recourse		3,517	3,548
Exelon Generation Co L L C [Member]
Current Assets
Cash and cash equivalents		1,019	750
Restricted cash and cash equivalents		126	153
Accounts receivable, net
Customer		2,587	2,941
Other		337	562
Mark-to-market derivative assets, current		602	804
Receivable from affiliates, current		166	173
Unamortized energy contract assets, current		49	49
Inventories, net
Fossil fuel and emission allowances		243	251
Materials and supplies		1,010	963
Assets held for sale		18	904
Other		1,002	883
Total current assets		7,159	8,433
Property, plant and equipment, net		23,591	23,981
Deferred debits and other assets
Nuclear decommissioning trust funds		12,706	11,661
Investments		248	414
Goodwill		47	47
Mark-to-market derivative assets, noncurrent		483	452
Prepaid pension asset		1,472	1,421
Unamortized energy contract assets, noncurrent		352	371
Deferred income taxes		11	21
Other		1,915	755
Total deferred debits and other assets		17,234	15,142
Total assets	[2]	47,984	47,556
Current Liabilities
Long-term debt due within one year		2,706	906
Accounts payable		1,583	1,847
Accrued expenses		762	898
Payable to affiliates, current		134	139
Borrowings from Exelon/PHI intercompany money pool		0	100
Mark-to-market derivative liabilities, current		212	449
Unamortized energy contract liabilities, current		21	31
Renewable energy credit obligation		374	343
Liabilities held for sale		11	777
Other		541	279
Total current liabilities		6,344	5,769
Long-term debt		5,018	6,989
Long-term debt to affiliates		889	898
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		3,607	3,383
Asset retirement obligations, noncurrent		9,855	9,450
Non-pension postretirement benefit obligations		885	900
Spent nuclear fuel obligation		1,193	1,171
Payables to affiliates, noncurrent		2,960	2,606
Mark-to-market derivative liabilities, noncurrent		163	252
Unamortized energy contract liabilities, noncurrent		11	20
Other		1,466	610
Total deferred credits and other liabilities		20,140	18,392
Total liabilities	[2]	32,391	32,048
Commitments and contingencies
Shareholders' equity
Retained earnings/Undistributed earnings		3,778	3,724
Accumulated other comprehensive loss, net		(36)	(38)
Member’s equity
Membership interest		9,525	9,518
Total members' equity		13,267	13,204
Noncontrolling Interests		2,326	2,304
Total equity		15,593	15,508
Total liabilities and shareholders’ equity		47,984	47,556
Variable Interest Entity, Consolidated, Assets, Pledged		9,443	9,634
Variable Interest Entity, Consolidated, Liabilities, No Recourse		3,467	3,480
Commonwealth Edison Co [Member]
Current Assets
Cash and cash equivalents		76	135
Restricted cash and cash equivalents		124	29
Accounts receivable, net
Customer		561	539
Other		322	320
Receivable from affiliates, current		27	20
Inventories, net
Inventories, net		162	148
Regulatory assets, current		286	293
Other		48	86
Total current assets		1,606	1,570
Property, plant and equipment, net		22,795	22,058
Deferred debits and other assets
Regulatory assets, noncurrent		1,436	1,307
Investments		6	6
Goodwill		2,625	2,625
Receivable from affiliates, noncurrent		2,487	2,217
Prepaid pension asset		1,020	1,035
Other		351	395
Total deferred debits and other assets		7,925	7,585
Total assets		32,326	31,213
Current Liabilities
Short-term borrowings		387	0
Long-term debt due within one year		500	300
Accounts payable		520	607
Accrued expenses		275	373
Payable to affiliates, current		87	119
Customer deposits		116	111
Regulatory liabilities, current		193	293
Mark-to-market derivative liabilities, current		27	26
Other		138	96
Total current liabilities		2,243	1,925
Long-term debt		7,696	7,801
Long-term debt to financing trusts		205	205
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		4,016	3,813
Asset retirement obligations, noncurrent		120	118
Non-pension postretirement benefit obligations		185	201
Regulatory liabilities, noncurrent		6,390	6,050
Mark-to-market derivative liabilities, noncurrent		253	223
Other		621	630
Total deferred credits and other liabilities		11,585	11,035
Total liabilities		21,729	20,966
Commitments and contingencies
Shareholders' equity
Common stock		1,588	1,588
Other paid-in capital		7,509	7,322
Retained deficit unappropriated		(1,639)	(1,639)
Retained earnings appropriated		3,139	2,976
Total shareholders’ equity		10,597	10,247
Member’s equity
Total liabilities and shareholders’ equity		32,326	31,213
PECO Energy Co [Member]
Current Assets
Cash and cash equivalents		224	130
Restricted cash and cash equivalents		6	5
Accounts receivable, net
Customer		286	321
Other		118	151
Receivable from affiliates, current		7	0
Inventories, net
Fossil fuel and emission allowances		41	38
Materials and supplies		37	37
Prepaid utility taxes		34	0
Regulatory assets, current		63	81
Other		27	19
Total current assets		843	782
Property, plant and equipment, net		9,100	8,610
Deferred debits and other assets
Regulatory assets, noncurrent		540	460
Investments		26	25
Receivable from affiliates, noncurrent		473	389
Prepaid pension asset		367	349
Other		30	27
Total deferred debits and other assets		1,436	1,250
Total assets		11,379	10,642
Current Liabilities
Accounts payable		382	370
Accrued expenses		97	113
Payable to affiliates, current		54	59
Customer deposits		69	68
Regulatory liabilities, current		93	175
Other		27	24
Total current liabilities		722	809
Long-term debt		3,404	3,084
Long-term debt to financing trusts		184	184
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,034	1,933
Asset retirement obligations, noncurrent		28	27
Non-pension postretirement benefit obligations		289	288
Regulatory liabilities, noncurrent		503	421
Other		79	76
Total deferred credits and other liabilities		2,933	2,745
Total liabilities		7,243	6,822
Commitments and contingencies
Shareholders' equity
Common stock		2,752	2,578
Retained earnings/Undistributed earnings		1,384	1,242
Total shareholders’ equity		4,136	3,820
Member’s equity
Total liabilities and shareholders’ equity		11,379	10,642
Baltimore Gas and Electric Company [Member]
Current Assets
Cash and cash equivalents		130	7
Restricted cash and cash equivalents		1	6
Accounts receivable, net
Customer		242	353
Other		110	90
Receivable from affiliates, current		1	1
Inventories, net
Fossil fuel and emission allowances		34	36
Materials and supplies		46	39
Prepaid utility taxes		0	74
Regulatory assets, current		180	177
Other		7	3
Total current assets		751	786
Property, plant and equipment, net		8,796	8,243
Deferred debits and other assets
Regulatory assets, noncurrent		386	398
Investments		7	5
Prepaid pension asset		276	279
Other		88	5
Total deferred debits and other assets		757	687
Total assets		10,304	9,716
Current Liabilities
Short-term borrowings		0	35
Accounts payable		245	295
Accrued expenses		165	155
Payable to affiliates, current		51	65
Customer deposits		120	120
Regulatory liabilities, current		21	77
Other		63	27
Total current liabilities		665	774
Long-term debt		3,270	2,876
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		1,329	1,222
Asset retirement obligations, noncurrent		22	24
Non-pension postretirement benefit obligations		198	201
Regulatory liabilities, noncurrent		1,158	1,192
Other		112	73
Total deferred credits and other liabilities		2,819	2,712
Total liabilities		6,754	6,362
Commitments and contingencies
Shareholders' equity
Common stock		1,818	1,714
Retained earnings/Undistributed earnings		1,732	1,640
Total shareholders’ equity		3,550	3,354
Member’s equity
Total liabilities and shareholders’ equity		10,304	9,716
Pepco Holdings LLC [Member]
Current Assets
Cash and cash equivalents		99	124
Restricted cash and cash equivalents		38	43
Accounts receivable, net
Customer		512	453
Other		189	177
Inventories, net
Fossil fuel and emission allowances		8	9
Materials and supplies		203	163
Regulatory assets, current		479	489
Other		50	75
Total current assets		1,578	1,533
Property, plant and equipment, net		13,968	13,446
Deferred debits and other assets
Regulatory assets, noncurrent		2,095	2,312
Investments		135	130
Goodwill		4,005	4,005
Prepaid pension asset		426	486
Deferred income taxes		13	12
Other		356	60
Total deferred debits and other assets		7,030	7,005
Total assets	[3]	22,576	21,984
Current Liabilities
Short-term borrowings		132	179
Long-term debt due within one year		118	125
Accounts payable		416	496
Accrued expenses		279	256
Payable to affiliates, current		95	94
Borrowings from Exelon/PHI intercompany money pool		10	0
Customer deposits		118	116
Regulatory liabilities, current		78	84
Unamortized energy contract liabilities, current		117	119
Other		152	123
Total current liabilities		1,515	1,592
Long-term debt		6,376	6,134
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,289	2,146
Asset retirement obligations, noncurrent		57	52
Non-pension postretirement benefit obligations		99	103
Regulatory liabilities, noncurrent		1,725	1,864
Unamortized energy contract liabilities, noncurrent		357	442
Other		610	369
Total deferred credits and other liabilities		5,137	4,976
Total liabilities	[3]	13,028	12,702
Commitments and contingencies
Shareholders' equity
Retained earnings/Undistributed earnings		45	62
Member’s equity
Membership interest		9,503	9,220
Total members' equity		9,548	9,282
Total equity		9,548	9,282
Total liabilities and shareholders’ equity		22,576	21,984
Variable Interest Entity, Consolidated, Assets, Pledged		22	33
Variable Interest Entity, Consolidated, Liabilities, No Recourse		50	69
Potomac Electric Power Company [Member]
Current Assets
Cash and cash equivalents		18	16
Restricted cash and cash equivalents		34	37
Accounts receivable, net
Customer		258	225
Other		114	81
Receivable from affiliates, current		0	1
Inventories, net
Inventories, net		118	93
Regulatory assets, current		252	270
Other		12	37
Total current assets		806	760
Property, plant and equipment, net		6,734	6,460
Deferred debits and other assets
Regulatory assets, noncurrent		577	643
Investments		109	105
Prepaid pension asset		301	316
Other		76	15
Total deferred debits and other assets		1,063	1,079
Total assets		8,603	8,299
Current Liabilities
Short-term borrowings		12	40
Long-term debt due within one year		8	15
Accounts payable		177	214
Accrued expenses		144	126
Payable to affiliates, current		65	62
Customer deposits		56	54
Regulatory liabilities, current		9	7
Merger related obligation		38	38
Current portion of DC PLUG obligation		30	30
Other		25	42
Total current liabilities		564	628
Long-term debt		2,852	2,704
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		1,150	1,064
Asset retirement obligations, noncurrent		41	37
Non-pension postretirement benefit obligations		23	29
Regulatory liabilities, noncurrent		749	822
Other		311	275
Total deferred credits and other liabilities		2,274	2,227
Total liabilities		5,690	5,559
Commitments and contingencies
Shareholders' equity
Common stock		1,765	1,636
Retained earnings/Undistributed earnings		1,148	1,104
Total shareholders’ equity		2,913	2,740
Member’s equity
Total liabilities and shareholders’ equity		8,603	8,299
Delmarva Power and Light Company [Member]
Current Assets
Cash and cash equivalents		11	23
Restricted cash and cash equivalents		0	1
Accounts receivable, net
Customer		112	134
Other		37	46
Inventories, net
Fossil fuel and emission allowances		8	9
Materials and supplies		47	37
Prepaid utility taxes		15	17
Regulatory assets, current		62	59
Other		5	10
Total current assets		297	336
Property, plant and equipment, net		3,941	3,821
Deferred debits and other assets
Regulatory assets, noncurrent		221	231
Goodwill		8	8
Prepaid pension asset		175	186
Other		82	6
Total deferred debits and other assets		486	431
Total assets		4,724	4,588
Current Liabilities
Short-term borrowings		57	0
Long-term debt due within one year		91	91
Accounts payable		90	111
Accrued expenses		59	39
Payable to affiliates, current		26	33
Customer deposits		36	35
Regulatory liabilities, current		43	59
Other		33	7
Total current liabilities		435	375
Long-term debt		1,404	1,403
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		655	628
Non-pension postretirement benefit obligations		16	17
Regulatory liabilities, noncurrent		580	606
Other		114	50
Total deferred credits and other liabilities		1,365	1,301
Total liabilities		3,204	3,079
Commitments and contingencies
Shareholders' equity
Common stock		914	914
Retained earnings/Undistributed earnings		606	595
Total shareholders’ equity		1,520	1,509
Member’s equity
Total liabilities and shareholders’ equity		4,724	4,588
Atlantic City Electric Company [Member]
Current Assets
Cash and cash equivalents		13	7
Restricted cash and cash equivalents		3	4
Accounts receivable, net
Customer		142	95
Other		47	55
Receivable from affiliates, current		1	1
Inventories, net
Inventories, net		37	33
Prepaid utility taxes		9	0
Regulatory assets, current		48	40
Other		7	5
Total current assets		307	240
Property, plant and equipment, net		3,124	2,966
Deferred debits and other assets
Regulatory assets, noncurrent		370	386
Prepaid pension asset		56	67
Other		59	40
Total deferred debits and other assets		485	493
Total assets	[4]	3,916	3,699
Current Liabilities
Short-term borrowings		63	139
Long-term debt due within one year		19	18
Accounts payable		139	154
Accrued expenses		40	35
Payable to affiliates, current		24	28
Customer deposits		26	26
Regulatory liabilities, current		25	18
Other		11	4
Total current liabilities		347	422
Long-term debt		1,305	1,170
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		569	535
Non-pension postretirement benefit obligations		18	17
Regulatory liabilities, noncurrent		365	402
Other		44	27
Total deferred credits and other liabilities		996	981
Total liabilities	[4]	2,648	2,573
Commitments and contingencies
Shareholders' equity
Common stock		1,134	979
Retained earnings/Undistributed earnings		134	147
Total shareholders’ equity		1,268	1,126
Member’s equity
Total liabilities and shareholders’ equity		3,916	3,699
Variable Interest Entity, Consolidated, Assets, Pledged		18	23
Variable Interest Entity, Consolidated, Liabilities, No Recourse		$ 46	$ 59
[1]	Exelon’s consolidated assets include $9,465 million and $9,667 million at September 30, 2019 and December 31, 2018 , respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,517 million and $3,548 million at September 30, 2019 and December 31, 2018 , respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 2 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $9,443 million and $9,634 million at September 30, 2019 and December 31, 2018 , respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,467 million and $3,480 million at September 30, 2019 and December 31, 2018 , respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 2 — Variable Interest Entities for additional information.
[3]	PHI’s consolidated total assets include $22 million and $33 million at September 30, 2019 and December 31, 2018 , respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $50 million and $69 million at September 30, 2019 and December 31, 2018 , respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 2 — Variable Interest Entities for additional information.
[4]	ACE’s consolidated total assets include $18 million and $23 million at September 30, 2019 and December 31, 2018 , respectively, of ACE's consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated total liabilities include $46 million and $59 million at September 30, 2019 and December 31, 2018 , respectively, of ACE's consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 2 — Variable Interest Entities for additional information.

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) shares in Millions, $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Customer allowance for uncollectible accounts	$ 248	$ 283
Other allowance for uncollectible accounts	49	36
Accumulated depreciation and amortization	$ 23,590	$ 22,902
Common Stock, Shares Authorized	2,000	2,000
Common Stock, Shares, Outstanding	972	968
Treasury Stock, Shares held	2	2
Exelon Generation Co L L C [Member]
Customer allowance for uncollectible accounts	$ 75	$ 103
Other allowance for uncollectible accounts	1	1
Accumulated depreciation and amortization	11,972	12,206
Commonwealth Edison Co [Member]
Customer allowance for uncollectible accounts	65	61
Other allowance for uncollectible accounts	21	20
Accumulated depreciation and amortization	5,046	4,684
PECO Energy Co [Member]
Customer allowance for uncollectible accounts	54	53
Other allowance for uncollectible accounts	7	8
Accumulated depreciation and amortization	3,670	3,561
Baltimore Gas and Electric Company [Member]
Customer allowance for uncollectible accounts	13	16
Other allowance for uncollectible accounts	4	4
Accumulated depreciation and amortization	3,772	3,633
Pepco Holdings LLC [Member]
Customer allowance for uncollectible accounts	41	50
Other allowance for uncollectible accounts	16	3
Accumulated depreciation and amortization	1,124	841
Potomac Electric Power Company [Member]
Customer allowance for uncollectible accounts	16	20
Other allowance for uncollectible accounts	8	1
Accumulated depreciation and amortization	3,473	3,354
Delmarva Power and Light Company [Member]
Customer allowance for uncollectible accounts	10	12
Other allowance for uncollectible accounts	1	1
Accumulated depreciation and amortization	1,407	1,329
Atlantic City Electric Company [Member]
Customer allowance for uncollectible accounts	15	18
Other allowance for uncollectible accounts	5	1
Accumulated depreciation and amortization	$ 1,192	$ 1,137

Consolidated Statements of Chan

Consolidated Statements of Changes in Shareholders Equity (Unaudited) - 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]	Other Comprehensive Income (Loss) [Member]	Exelon Generation Co L L C [Member]	Exelon Generation Co L L C [Member]Membership Interest [Member]	Exelon Generation Co L L C [Member]Retained Earnings, Unappropriated/Undistributed [Member]	Exelon Generation Co L L C [Member]Accumulated Other Comprehensive Income (Loss) [Member]	Exelon Generation Co L L C [Member]Noncontrolling Interest [Member]	Commonwealth Edison Co [Member]	Commonwealth Edison Co [Member]Common Stock [Member]	Commonwealth Edison Co [Member]Other Paid-in-Capital [Member]	Commonwealth Edison Co [Member]Retained Earnings, Unappropriated/Undistributed [Member]	Commonwealth Edison Co [Member]Retained Earnings, Appropriated	Commonwealth Edison Co [Member]Retained Earnings [Member]	PECO Energy Co [Member]	PECO Energy Co [Member]Common Stock [Member]	PECO Energy Co [Member]Retained Earnings [Member]	PECO Energy Co [Member]Accumulated Other Comprehensive Income (Loss) [Member]	Baltimore Gas and Electric Company [Member]	Baltimore Gas and Electric Company [Member]Common Stock [Member]	Baltimore Gas and Electric Company [Member]Retained Earnings [Member]	Pepco Holdings LLC [Member]	Pepco Holdings LLC [Member]Membership Interest [Member]	Pepco Holdings LLC [Member]Retained Earnings, Unappropriated/Undistributed [Member]	Potomac Electric Power Company [Member]	Potomac Electric Power Company [Member]Common Stock [Member]	Potomac Electric Power Company [Member]Retained Earnings [Member]	Delmarva Power and Light Company [Member]	Delmarva Power and Light Company [Member]Common Stock [Member]	Delmarva Power and Light Company [Member]Retained Earnings [Member]	Atlantic City Electric Company [Member]	Atlantic City Electric Company [Member]Common Stock [Member]	Atlantic City Electric Company [Member]Retained Earnings [Member]
Beginning balance (in shares) at Dec. 31, 2017	965,168
Beginning balance at Dec. 31, 2017	$ 32,187	$ 18,964	$ (123)	$ 14,081	$ (3,026)	$ 2,291
Beginning Balance at Dec. 31, 2017								$ 15,959	$ 9,357	$ 4,349	$ (37)	$ 2,290														$ 8,825	$ 8,835	$ (10)
Beginning Balance at Dec. 31, 2017													$ 9,542	$ 1,588	$ 6,822	$ (1,639)	$ 2,771		$ 3,577	$ 2,489	$ 1,087	$ 1	$ 3,141	$ 1,605	$ 1,536				$ 2,533	$ 1,470	$ 1,063	$ 1,335	$ 764	$ 571	$ 1,043	$ 912	$ 131
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 636			585		51		186		136		50	165			165			113		113	0	128		128	65		65	31		31	31		31	7		7
Stock issued during period, shares, long-term incentive plan activity	1,685
Stock issued during period, value, long-term incentive plan activity	$ (3)	(3)	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	361
Stock issued during period, value, employee stock purchase plan	$ 12	12	0	0	0	0
Changes in equity of noncontrolling interests	(9)					(9)		(9)				(9)
Common stock dividends	(334)			(334)									(114)				(114)		(287)		(287)		(52)		(52)				(25)		(25)	(36)		(36)	(9)		(9)
Contributions from parent													113		113
Distributions to member								(188)		(188)																(71)		(71)
Other comprehensive income (loss), net of income taxes					71	1	$ 72	7		0	6	1
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard	$ 4			14	(10)			3		6	(3)								0		1	(1)
Ending balance (in shares) at Mar. 31, 2018	967,214
Ending balance at Mar. 31, 2018	$ 32,565	18,973	(123)	14,346	(2,965)	2,334
Ending Balance at Mar. 31, 2018								15,958	9,357	4,303	(34)	2,332														8,819	8,835	(16)
Ending Balance at Mar. 31, 2018													9,706	1,588	6,935	(1,639)	2,822		3,403	2,489	914	0	3,217	1,605	1,612				2,539	1,470	1,069	1,330	764	566	1,041	912	129
Beginning balance (in shares) at Dec. 31, 2017	965,168
Beginning balance at Dec. 31, 2017	$ 32,187	18,964	(123)	14,081	(3,026)	2,291
Beginning Balance at Dec. 31, 2017								15,959	9,357	4,349	(37)	2,290														8,825	8,835	(10)
Beginning Balance at Dec. 31, 2017													9,542	1,588	6,822	(1,639)	2,771		3,577	2,489	1,087	1	3,141	1,605	1,536				2,533	1,470	1,063	1,335	764	571	1,043	912	131
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,979							667					523						336				242			336			174			90			76
Other comprehensive income (loss), net of income taxes	$ 169				167			11
Ending balance (in shares) at Sep. 30, 2018	968,842
Ending balance at Sep. 30, 2018	$ 33,388	19,063	(123)	14,949	(2,869)	2,368
Ending Balance at Sep. 30, 2018								15,960	9,411	4,214	(31)	2,366														9,166	9,072	94
Ending Balance at Sep. 30, 2018													10,107	1,588	7,209	(1,639)	2,949		3,684	2,560	1,124	0	3,244	1,623	1,621				2,664	1,555	1,109	1,517	914	603	1,073	912	161
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Appropriation of retained earnings for future dividends																(165)	165	$ 0
Beginning balance (in shares) at Mar. 31, 2018	967,214
Beginning balance at Mar. 31, 2018	$ 32,565	18,973	(123)	14,346	(2,965)	2,334
Beginning Balance at Mar. 31, 2018								15,958	9,357	4,303	(34)	2,332														8,819	8,835	(16)
Beginning Balance at Mar. 31, 2018													9,706	1,588	6,935	(1,639)	2,822		3,403	2,489	914	0	3,217	1,605	1,612				2,539	1,470	1,069	1,330	764	566	1,041	912	129
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 542			539		3		181		178		3	164			164			96		96	0	51		51	84		84	54		54	26		26	8		8
Stock issued during period, shares, long-term incentive plan activity	183
Stock issued during period, value, long-term incentive plan activity	$ 20	20	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	342
Stock issued during period, value, employee stock purchase plan	$ 15	15	0	0	0	0
Changes in equity of noncontrolling interests	(14)					(14)		(13)				(13)
Common stock dividends	$ (334)			(334)									(115)				(115)		(5)		(5)		(53)		(53)				(25)		(25)	(4)		(4)	(10)		(10)
Contributions from parent													112		112				41	41	0	0				235	235		85	85		150	150
Distributions to member								(189)		(189)																(38)		(38)
Other comprehensive income (loss), net of income taxes					44	1	45	2		0	1	1
Ending balance (in shares) at Jun. 30, 2018	967,739
Ending balance at Jun. 30, 2018	$ 32,839	19,008	(123)	14,551	(2,921)	2,324
Ending Balance at Jun. 30, 2018								15,939	9,357	4,292	(33)	2,323														9,100	9,070	30
Ending Balance at Jun. 30, 2018													9,867	1,588	7,047	(1,639)	2,871		3,535	2,530	1,005	0	3,215	1,605	1,610				2,653	1,555	1,098	1,502	914	588	1,039	912	127
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Appropriation of retained earnings for future dividends																(164)	164	0
Net income	$ 800			733		67		300		234		66	193			193			126		126	0	63		63	187		187	89		89	33		33	61		61
Stock issued during period, shares, long-term incentive plan activity	809
Stock issued during period, value, long-term incentive plan activity	$ 15	15	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	294
Stock issued during period, value, employee stock purchase plan	$ 40	40	0	0	0	0
Changes in equity of noncontrolling interests	(23)					(23)		(23)				(23)
Common stock dividends	(335)			(335)									(115)				(115)		(7)		(7)		(52)		(52)				(78)		(78)	(18)		(18)	(27)		(27)
Contributions from parent								54	54				162		162				30	30	0	0	18	18	0	2	2
Distributions to member								(312)		(312)																(123)		(123)
Other comprehensive income (loss), net of income taxes	$ 52				52	0	52	2		0	2	0
Ending balance (in shares) at Sep. 30, 2018	968,842
Ending balance at Sep. 30, 2018	$ 33,388	19,063	(123)	14,949	(2,869)	2,368
Ending Balance at Sep. 30, 2018								15,960	9,411	4,214	(31)	2,366														9,166	9,072	94
Ending Balance at Sep. 30, 2018													10,107	1,588	7,209	(1,639)	2,949		3,684	2,560	1,124	0	3,244	1,623	1,621				2,664	1,555	1,109	1,517	914	603	1,073	912	161
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Appropriation of retained earnings for future dividends																(193)	193	0
Appropriation of retained earnings for future dividends													2,976
Beginning balance (in shares) at Dec. 31, 2018	970,020
Beginning balance at Dec. 31, 2018	$ 33,070	19,116	(123)	14,766	(2,995)	2,306
Beginning Balance at Dec. 31, 2018								15,508	9,518	3,724	(38)	2,304														9,282	9,220	62
Beginning Balance at Dec. 31, 2018	30,764												10,247	1,588	7,322	(1,639)	2,976		3,820	2,578	1,242	0	3,354	1,714	1,640				2,740	1,636	1,104	1,509	914	595	1,126	979	147
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 966			907		59		422		363		59	157			157			168		168	0	160		160	117		117	55		55	53		53	10		10
Stock issued during period, shares, long-term incentive plan activity	2,446
Stock issued during period, value, long-term incentive plan activity	$ (3)	(3)	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	320
Stock issued during period, value, employee stock purchase plan	$ 51	51	0	0	0	0
Changes in equity of noncontrolling interests	(17)					(17)		(17)				(17)
Sale of noncontrolling interests	7	7						7	7
Common stock dividends	$ (352)			(352)									(127)				(127)		(90)		(90)		(56)		(56)				(24)		(24)	(41)		(41)	(12)		(12)
Contributions from parent													63		63				145	145	0	0				19	19		14	14					5	5
Distributions to member								(225)		(225)																(128)		(128)
Other comprehensive income (loss), net of income taxes					(17)	(1)	(18)	1		0	2	(1)
Ending balance (in shares) at Mar. 31, 2019	972,786
Ending balance at Mar. 31, 2019	$ 33,704	19,171	(123)	15,321	(3,012)	2,347
Ending Balance at Mar. 31, 2019								15,696	9,525	3,862	(36)	2,345														9,290	9,239	51
Ending Balance at Mar. 31, 2019													10,340	1,588	7,385	(1,639)	3,006		4,043	2,723	1,320	0	3,458	1,714	1,744				2,785	1,650	1,135	1,521	914	607	1,129	984	145
Beginning balance (in shares) at Dec. 31, 2018	970,020
Beginning balance at Dec. 31, 2018	$ 33,070	19,116	(123)	14,766	(2,995)	2,306
Beginning Balance at Dec. 31, 2018								15,508	9,518	3,724	(38)	2,304														9,282	9,220	62
Beginning Balance at Dec. 31, 2018	30,764												10,247	1,588	7,322	(1,639)	2,976		3,820	2,578	1,242	0	3,354	1,714	1,640				2,740	1,636	1,104	1,509	914	595	1,126	979	147
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	2,220							784					544						410				261			412			217			116			87
Other comprehensive income (loss), net of income taxes	$ 33				32			3
Ending balance (in shares) at Sep. 30, 2019	973,941
Ending balance at Sep. 30, 2019	$ 34,352	19,238	(123)	15,871	(2,963)	2,329
Ending Balance at Sep. 30, 2019								15,593	9,525	3,778	(36)	2,326														9,548	9,503	45
Ending Balance at Sep. 30, 2019	$ 32,023												10,597	1,588	7,509	(1,639)	3,139		4,136	2,752	1,384	0	3,550	1,818	1,732				2,913	1,765	1,148	1,520	914	606	1,268	1,134	134
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Appropriation of retained earnings for future dividends																(157)	157	0
Beginning balance (in shares) at Mar. 31, 2019	972,786
Beginning balance at Mar. 31, 2019	$ 33,704	19,171	(123)	15,321	(3,012)	2,347
Beginning Balance at Mar. 31, 2019								15,696	9,525	3,862	(36)	2,345														9,290	9,239	51
Beginning Balance at Mar. 31, 2019													10,340	1,588	7,385	(1,639)	3,006		4,043	2,723	1,320	0	3,458	1,714	1,744				2,785	1,650	1,135	1,521	914	607	1,129	984	145
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 494			484		10		118		108		10	186			186			102		102	0	45		45	106		106	64		64	30		30	14		14
Stock issued during period, shares, long-term incentive plan activity	320
Stock issued during period, value, long-term incentive plan activity	$ 14	14	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	311
Stock issued during period, value, employee stock purchase plan	$ 24	24	0	0	0	0
Changes in equity of noncontrolling interests	3					3		3				3
Common stock dividends	$ (353)			(353)									(127)				(127)		(90)		(90)		(55)		(55)				(48)		(48)	(29)		(29)	(12)		(12)
Contributions from parent													61		61											264	264		115	115					150	150
Distributions to member								(224)		(224)																(88)		(88)
Other comprehensive income (loss), net of income taxes					22	(1)	21	(1)		0	0	(1)
Ending balance (in shares) at Jun. 30, 2019	973,417
Ending balance at Jun. 30, 2019	$ 33,907	19,209	(123)	15,452	(2,990)	2,359
Ending Balance at Jun. 30, 2019								15,592	9,525	3,746	(36)	2,357														9,572	9,503	69
Ending Balance at Jun. 30, 2019													10,460	1,588	7,446	(1,639)	3,065		4,055	2,723	1,332	0	3,448	1,714	1,734				2,916	1,765	1,151	1,522	914	608	1,281	1,134	147
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Appropriation of retained earnings for future dividends																(186)	186	0
Net income	$ 760			772		(12)		244		257		(13)	200			200			140		140	0	55		55	189		189	98		98	33		33	63		63
Stock issued during period, shares, long-term incentive plan activity	207
Stock issued during period, value, long-term incentive plan activity	$ 10	10	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	317
Stock issued during period, value, employee stock purchase plan	$ 19	19	0	0	0	0
Changes in equity of noncontrolling interests	(18)					(18)		(18)				(18)
Sale of noncontrolling interests		0
Common stock dividends	(353)			(353)									(126)				(126)		(88)		(88)		(57)		(57)				(101)		(101)	(35)		(35)	(76)		(76)
Contributions from parent													63		63				29	29	0	0	104	104	0
Distributions to member								(225)		(225)																(213)		213
Other comprehensive income (loss), net of income taxes	$ 30				27	0	$ 27	3
Ending balance (in shares) at Sep. 30, 2019	973,941
Ending balance at Sep. 30, 2019	$ 34,352	$ 19,238	$ (123)	$ 15,871	$ (2,963)	$ 2,329
Ending Balance at Sep. 30, 2019								$ 15,593	$ 9,525	$ 3,778	$ (36)	$ 2,326														$ 9,548	$ 9,503	$ 45
Ending Balance at Sep. 30, 2019	$ 32,023												10,597	$ 1,588	$ 7,509	(1,639)	3,139		$ 4,136	$ 2,752	$ 1,384	$ 0	$ 3,550	$ 1,818	$ 1,732				$ 2,913	$ 1,765	$ 1,148	$ 1,520	$ 914	$ 606	$ 1,268	$ 1,134	$ 134
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Appropriation of retained earnings for future dividends													$ 3,139			$ (200)	$ 200	$ 0

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Shareholders Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Statement of Stockholders' Equity [Abstract]
Common Stock, Dividends, Per Share, Declared	$ 0.36	$ 0.36	$ 0.36	$ 0.35	$ 0.35	$ 0.35

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Significant Accounting Policies [Text Block]	Basis of Presentation (All Registrants) Each of the Registrant’s Consolidated Financial Statements includes the accounts of its subsidiaries. All intercompany transactions have been eliminated. Through its business services subsidiary, BSC, Exelon provides its subsidiaries with a variety of support services at cost, including legal, human resources, financial, information technology and supply management services. PHI also has a business services subsidiary, PHISCO, which provides a variety of support services at cost, including legal, accounting, engineering, customer operations, distribution and transmission planning, asset management, system operations, and power procurement, to PHI operating companies. The costs of BSC and PHISCO are directly charged or allocated to the applicable subsidiaries. The results of Exelon’s corporate operations are presented as “Other” within the consolidated financial statements and include intercompany eliminations unless otherwise disclosed. The accompanying consolidated financial statements as of September 30, 2019 and 2018 and for the three and nine months then ended are unaudited but, in the opinion of the management of each Registrant include all adjustments that are considered necessary for a fair statement of the Registrants’ respective financial statements in accordance with GAAP. All adjustments are of a normal, recurring nature, except as otherwise disclosed. The December 31, 2018 Consolidated Balance Sheets were derived 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, 2019 . 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. New Accounting Standards (All Registrants) New Accounting Standards Adopted in 2019: In 2019, the Registrants have adopted the following new authoritative accounting guidance issued by the FASB. Leases. The Registrants applied the new guidance with the following transition practical expedients: • a "package of three" expedients that must be taken together and allow entities to (1) not reassess whether existing contracts contain leases, (2) carry forward the existing lease classification, and (3) not reassess initial direct costs associated with existing leases, • an implementation expedient which allows the requirements of the standard in the period of adoption with no restatement of prior periods, and • a land easement expedient which allows entities to not evaluate land easements under the new standard at adoption if they were not previously accounted for as leases. The standard materially impacted the Registrants' Consolidated Balance Sheets but did not have a material impact in the Registrants' Consolidated Statements of Operations and Comprehensive Income, Consolidated Statements of Cash Flows and Consolidated Statements of Changes in Shareholders' Equity. The most significant impact was the recognition of the ROU assets and lease liabilities for operating leases. The operating ROU assets and lease liabilities recognized upon adoption are materially consistent with the balances presented in the Combined Notes to the Consolidated Financial Statements. See Note 5 - Leases for additional information. See Note 1 — Significant Accounting Policies of the Exelon 2018 Form 10-K for additional information on new accounting standards issued and adopted as of January 1, 2019. New Accounting Standards Issued and Not Yet Adopted as of September 30, 2019 : The following new authoritative accounting guidance issued by the FASB has not yet been adopted and reflected by the Registrants in their consolidated financial statements as of September 30, 2019 . Unless otherwise indicated, the Registrants are currently assessing the impacts such guidance may have (which could be material) in their financial statements. The Registrants have assessed other FASB issuances of new standards which are not listed below as the Registrants do not expect such standards to have a material impact to their financial statements. Goodwill Impairment (Issued January 2017). Simplifies the accounting for goodwill impairment by removing Step 2 of the current test, which requires calculation of a hypothetical purchase price allocation. Under the revised guidance, goodwill impairment will be measured as the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill (currently Step 1 of the two-step impairment test). Entities will continue to have the option to perform a qualitative assessment to determine if a quantitative impairment test is necessary. Exelon, Generation, ComEd, PHI and DPL do not expect the updated guidance to have a material impact to their financial statements. The standard is effective January 1, 2020, with early adoption permitted, and must be applied on a prospective basis. Impairment of Financial Instruments (Issued June 2016). Provides for a new Current Expected Credit Loss (CECL) impairment model for specified financial instruments including loans, trade receivables, debt securities classified as held-to-maturity investments and net investments in leases recognized by a lessor. Under the new guidance, on initial recognition and at each reporting period, an entity is required to recognize an allowance that reflects its current estimate of credit losses expected to be incurred over the life of the financial instrument based on historical experience, current conditions and reasonable and supportable forecasts. The standard will be effective January 1, 2020 (with early adoption as of January 1, 2019 permitted) and requires a modified retrospective transition approach through a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption. This standard is primarily applicable to Generation's and the Utility Registrants' trade accounts receivable balances. The Registrants do not expect that this guidance will have a significant impact on their consolidated financial statements. Leases (All Registrants) The Registrants recognize a ROU asset and lease liability for operating leases with a term of greater than one year. The ROU asset is included in Other deferred debits and other assets and the lease liability is included in Other current liabilities and Other deferred credits and other liabilities on the Consolidated Balance Sheets. The ROU asset is measured as the sum of (1) the present value of all remaining fixed and in-substance fixed payments using each Registrant’s incremental borrowing rate, (2) any lease payments made at or before the commencement date (less any lease incentives received) and (3) any initial direct costs incurred. The lease liability is measured the same as the ROU asset, but excludes any payments made before the commencement date and initial direct costs incurred. Lease terms include options to extend or terminate the lease if it is reasonably certain they will be exercised. The Registrants include non-lease components, which are service-related costs that are not integral to the use of the asset, in the measurement of the ROU asset and lease liability. Expense for operating leases and leases with a term of one year or less is recognized on a straight-line basis over the term of the lease, unless another systematic and rational basis is more representative of the derivation of benefit from use of the leased property. Variable lease payments are recognized in the period in which the related obligation is incurred and consist primarily of payments for purchases of electricity under contracted generation and are based on the electricity produced by those generating assets. Operating lease expense and variable lease payments are recorded to Purchased power and fuel expense for contracted generation or Operating and maintenance expense for all other lease agreements on the Registrants’ Statements of Operations and Comprehensive Income. Income from operating leases, including subleases, is recognized on a straight-line basis over the term of the lease, unless another systematic and rational basis is more representative of the pattern in which income is earned over the term of the lease. Variable lease payments are recognized in the period in which the related obligation is performed and consist primarily of payments received from sales of electricity under contracted generation and are based on the electricity produced by those generating assets. Operating lease income and variable lease payments are recorded to Operating revenues on the Registrants’ Statements of Operations and Comprehensive Income. The Registrants’ operating leases consist primarily of contracted generation, real estate including office buildings, and vehicles and equipment. The Registrants generally account for contracted generation in which the generating asset is not renewable as a lease if the customer has dispatch rights and obtains substantially all of the economic benefits. For new agreements entered after January 1, 2019, the Registrants will generally not account for contracted generation in which the generating asset is renewable as a lease if the customer does not design the generating asset. The Registrants account for land right arrangements that provide for exclusive use as leases while shared use land arrangements are generally not leases. The Registrants do not account for secondary use pole attachments as leases. See Note 5 — Leases for additional information. Significant Accounting Policies (All Registrants)
Business Description [Text Block]	Significant Accounting Policies (All Registrants) Description of Business (All Registrants) Exelon is a utility services holding company engaged in the generation, delivery and marketing of energy through Generation and the energy distribution and transmission businesses through ComEd, PECO, BGE, Pepco, DPL and ACE. Name of Registrant Business Service Territories Exelon Generation Generation, physical delivery and marketing of power across multiple geographical regions through its customer-facing business, Constellation, which sells electricity to both wholesale and retail customers. Generation also sells natural gas, renewable energy and other energy-related products and services. Five reportable segments: Mid-Atlantic, Midwest, New York, ERCOT and Other Power Regions Commonwealth Edison Company Purchase and regulated retail sale of electricity Northern Illinois, including the City of Chicago Transmission and distribution of electricity to retail customers PECO Energy Company Purchase and regulated retail sale of electricity and natural gas Southeastern Pennsylvania, including the City of Philadelphia (electricity) Transmission and distribution of electricity and distribution of natural gas to retail customers Pennsylvania counties surrounding the City of Philadelphia (natural gas) Baltimore Gas and Electric Company Purchase and regulated retail sale of electricity and natural gas Central Maryland, including the City of Baltimore (electricity and natural gas) Transmission and distribution of electricity and distribution of natural gas to retail customers Pepco Holdings LLC Utility services holding company engaged, through its reportable segments Pepco, DPL and ACE Service Territories of Pepco, DPL and ACE Potomac Electric Purchase and regulated retail sale of electricity District of Columbia, and major portions of Montgomery and Prince George’s Counties, Maryland Transmission and distribution of electricity to retail customers Delmarva Power & Light Company Purchase and regulated retail sale of electricity and natural gas Portions of Delaware and Maryland (electricity) Transmission and distribution of electricity and distribution of natural gas to retail customers Portions of New Castle County, Delaware (natural gas) Atlantic City Electric Company Purchase and regulated retail sale of electricity Portions of Southern New Jersey Transmission and distribution of electricity to retail customers

Variable Interest Entities (Exe

Variable Interest Entities (Exelon, Generation, PHI and ACE)	9 Months Ended
	Sep. 30, 2019
Variable Interest Entity [Abstract]
Variable Interest Entites (Exelon, Generation, PHI and ACE)	Variable Interest Entities (Exelon, Generation, PHI and ACE) At September 30, 2019 and December 31, 2018 , Exelon, Generation, PHI and ACE collectively consolidated several VIEs or VIE groups for which the applicable Registrant was the primary beneficiary (see Consolidated VIEs below) and had significant interests in several other VIEs for which the applicable Registrant does not have the power to direct the entities’ activities and, accordingly, was not the primary beneficiary (see Unconsolidated VIEs below). Consolidated and unconsolidated VIEs are aggregated to the extent that the entities have similar risk profiles. Consolidated VIEs The table below shows the carrying amounts and classification of the consolidated VIEs’ assets and liabilities included in the consolidated financial statements of Exelon, Generation, PHI and ACE as of September 30, 2019 and December 31, 2018 . The assets, except as noted in the footnotes to the table below, can only be used to settle obligations of the VIEs. The liabilities, except as noted in the footnote to the table below, are such that creditors, or beneficiaries, do not have recourse to the general credit of Exelon, Generation, PHI and ACE. September 30, 2019 December 31, 2018 Exelon Generation PHI (a) ACE Exelon Generation PHI (a) ACE Cash and cash equivalents $ 168 $ 168 $ — $ — $ 414 $ 414 $ — $ — Restricted cash and cash equivalents 76 73 3 3 66 62 4 4 Accounts receivable, net Customer 163 163 — — 146 146 — — Other 43 43 — — 23 23 — — Unamortized energy contract asset (b) 23 23 — — 25 25 — — Inventory, net Materials and supplies 222 222 — — 212 212 — — Other current assets 50 48 2 — 52 49 3 — Total current assets 745 740 5 3 938 931 7 4 Property, plant and equipment, net (c) 6,079 6,079 — — 6,188 6,188 — — NDT funds 2,636 2,636 — — 2,351 2,351 — — Unamortized energy contract asset (b) 258 258 — — 274 274 — — Other noncurrent assets 69 52 17 15 258 232 26 19 Total noncurrent assets 9,042 9,025 17 15 9,071 9,045 26 19 Total assets $ 9,787 $ 9,765 $ 22 $ 18 $ 10,009 $ 9,976 $ 33 $ 23 Long-term debt due within one year $ 556 $ 535 $ 21 $ 19 $ 87 $ 66 $ 21 $ 18 Accounts payable 148 148 — — 96 96 — — Accrued expenses 58 57 1 1 73 72 1 1 Unamortized energy contract liabilities 10 10 — — 15 15 — — Other current liabilities 30 30 — — 3 3 — — Total current liabilities 802 780 22 20 274 252 22 19 Long-term debt 532 504 28 26 1,072 1,025 47 40 Asset retirement obligations (d) 2,103 2,103 — — 2,165 2,165 — — Unamortized energy contract liabilities 1 1 — — 1 1 — — Other noncurrent liabilities 84 84 — — 42 42 — — Total noncurrent liabilities 2,720 2,692 28 26 3,280 3,233 47 40 Total liabilities $ 3,522 $ 3,472 $ 50 $ 46 $ 3,554 $ 3,485 $ 69 $ 59 _________ (a) Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity. (b) These are unrestricted assets to Exelon and Generation. (c) Exelon’s and Generation’s balances include unrestricted assets of $41 million and $43 million as of September 30, 2019 and December 31, 2018 , respectively. (d) Exelon’s and Generation’s balances include liabilities with recourse of $5 million as of September 30, 2019 and December 31, 2018 . As of September 30, 2019 and December 31, 2018 , Exelon's and Generation's consolidated VIEs consist of: Consolidated VIE or VIE groups: Reason entity is a VIE: Reason Generation is primary beneficiary: CENG - A joint venture between Generation and EDF. Generation has a 50.01% equity ownership in CENG. See additional discussion below. Disproportionate relationship between equity interest and operational control as a result of the Nuclear Operating Services Agreement (NOSA) described further below. Generation conducts the operational activities. EGRP - A collection of wind and solar project entities. Generation has a 51% equity ownership in EGRP. See additional discussion below. Similar structure to a limited partnership and the limited partners do not have kick out rights with respect to the general partner. Generation conducts the operational activities. Bluestem Wind Energy Holdings, LLC - A Tax Equity structure which is consolidated by EGRP. Generation is a minority interest holder. Similar structure to a limited partnership and the limited partners do not have kick out rights with respect to the general partner. Generation conducts the operational activities. Antelope Valley - A solar generating facility, which is 100% owned by Generation. Antelope Valley sells all of its output to PG&E through a PPA. The PPA contract absorbs variability through a performance guarantee. Generation conducts all activities. Equity investment in distributed energy company - Generation has a 31% equity ownership. This distributed energy company has an interest in an unconsolidated VIE (see Unconsolidated VIEs disclosure below). Generation fully impaired this investment in the third quarter of 2019. See Note 7— Asset Impairments for additional information. Similar structure to a limited partnership and the limited partners do not have kick out rights with respect to the general partner. Generation conducts the operational activities. CENG - On April 1, 2014, Generation, CENG, and subsidiaries of CENG executed the NOSA pursuant to which Generation conducts all activities associated with the operations of the CENG fleet and provides corporate and administrative services to CENG and the CENG fleet for the remaining life of the CENG nuclear plants as if they were a part of the Generation nuclear fleet, subject to the CENG member rights of EDF. Exelon and Generation, where indicated, provide the following support to CENG: • Generation provided a $400 million loan to CENG. The loan balance was fully repaid by CENG in January 2019. • Generation executed an Indemnity Agreement pursuant to which Generation agreed to indemnify EDF 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 22 — Commitments and Contingencies of the Exelon 2018 Form 10-K for additional information. • Generation and EDF share in the $688 million of contingent payment obligations for the payment of contingent retrospective premium adjustments for the nuclear liability insurance. • 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. EGRP - EGRP is a collection of wind and solar project entities and some of these project entities are VIEs that are consolidated by EGRP. Generation owns a number of limited liability companies that build, own, and operate solar and wind power facilities some of which are owned by EGRP. While Generation or EGRP owns 100% of the solar entities and 100% of the majority of the wind entities, it has been determined that certain of the solar and wind entities are VIEs because the entities require additional subordinated financial support in the form of a parental guarantee of debt, loans from the customers in order to obtain the necessary funds for construction of the solar facilities, or the customers absorb price variability from the entities through the fixed price power and/or REC purchase agreements. Generation is the primary beneficiary of these solar and wind entities that qualify as VIEs because Generation controls the design, construction, and operation of the facilities. Generation provides operating and capital funding to the solar and wind entities for ongoing construction, operations and maintenance and there is limited recourse related to Generation related to certain solar and wind entities. In 2017, Generation’s interests in EGRP were contributed to and are pledged for the EGR IV non-recourse debt project financing structure. Refer to Note 11 — Debt and Credit Agreements for additional information. As of September 30, 2019 and December 31, 2018 , Exelon's, PHI's and ACE's consolidated VIE consists of: Consolidated VIEs: Reason entity is a VIE: Reason ACE is the primary beneficiary: ACE Transition Funding - A special purpose entity formed by ACE for the purpose of securitizing authorized portions of ACE’s recoverable stranded costs through the issuance and sale of transition bonds. Proceeds from the sale of each series of transition bonds by ATF were transferred to ACE in exchange for the transfer by ACE to ATF of the right to collect a non-bypassable Transition Bond Charge from ACE customers pursuant to bondable stranded costs rate orders issued by the NJBPU in an amount sufficient to fund the principal and interest payments on transition bonds and related taxes, expenses and fees. ACE’s equity investment is a variable interest as, by design, it absorbs any initial variability of ACETF. The bondholders also have a variable interest for the investment made to purchase the transition bonds. ACE controls the servicing activities. Unconsolidated VIEs 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 in Exelon’s and Generation’s Consolidated Balance Sheets in Investments. For the energy purchase and sale contracts (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. As of September 30, 2019 and December 31, 2018 , Exelon and Generation had significant unconsolidated variable interests in several VIEs for which Exelon or Generation, as applicable, was not the primary beneficiary. These interests include certain equity method investments and certain commercial agreements. The following table presents summary information about Exelon's and Generation’s unconsolidated VIE entities: September 30, 2019 December 31, 2018 Commercial Agreement VIEs Equity Investment VIEs Total Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 614 $ 453 $ 1,067 $ 597 $ 472 $ 1,069 Total liabilities (a) 36 224 260 37 222 259 Exelon's ownership interest in VIE (a) — 201 201 — 223 223 Other ownership interests in VIE (a) 587 28 615 560 27 587 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 12 12 — 223 223 _________ (a) These items represent amounts in the unconsolidated VIE balance sheets, not in Exelon’s or Generation’s Consolidated Balance Sheets. These items are included to provide information regarding the relative size of the unconsolidated VIEs. For each of the unconsolidated VIEs, Exelon and Generation have 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. As of September 30, 2019 and December 31, 2018 , Exelon's and Generation's unconsolidated VIEs consist of: Unconsolidated VIE groups: Reason entity is a VIE: Reason Generation is not the primary beneficiary: Equity investments in distributed energy companies - 1) Generation has a 90% equity ownership in a distributed energy company. 2) Generation, via a consolidated VIE, has a 90% equity ownership in another distributed energy company (See Consolidated VIEs disclosure above). Generation fully impaired these investments in the third quarter of 2019. See Note 7— Asset Impairments for additional information. Similar structures to a limited partnership and the limited partners do not have kick out rights with respect to the general partner. Generation does not conduct the operational activities. Energy Purchase and Sale agreements - Generation has several energy purchase and sale agreements with generating facilities. PPA contracts that absorb variability through fixed pricing. Generation does not conduct the operational activities.

Mergers, Acquisitions and Dispo

Mergers, Acquisitions and Dispositions (Exelon and Generation)	9 Months Ended
	Sep. 30, 2019
Business Combinations [Abstract]
Mergers, Acquisitions and Dispositions Disclosures [Text Block]	Mergers, Acquisitions and Dispositions (Exelon and Generation) Acquisition of Handley Generating Station On November 7, 2017, ExGen Texas Power, LLC (EGTP), and all of its wholly owned subsidiaries filed voluntary petitions for relief under Chapter 11 of Title 11 of the United States Code in the United States Bankruptcy Court for the District of Delaware, which resulted in Exelon and Generation deconsolidating EGTP's assets and liabilities from their consolidated financial statements. Concurrently with the Chapter 11 filings, Generation entered into an asset purchase agreement to acquire one of EGTP's generating plants, the Handley Generating Station, which closed on April 4, 2018 for a purchase price of $62 million . Disposition of Oyster Creek On July 31, 2018, Generation entered into an agreement with Holtec International (Holtec) and its indirect wholly owned subsidiary, Oyster Creek Environmental Protection, LLC (OCEP), for the sale and decommissioning of Oyster Creek located in Forked River, New Jersey, which permanently ceased generation operations on September 17, 2018. Completion of the transaction contemplated by the sale agreement was subject to the satisfaction of several closing conditions, including approval of the license transfer from the NRC and other regulatory approvals, and a private letter ruling from the IRS, which were satisfied in the second quarter 2019. The sale was completed on July 1, 2019. Exelon and Generation recognized a loss on the sale in the third quarter, which was immaterial. Under the terms of the transaction, Generation transferred to OCEP substantially all the assets associated with Oyster Creek, including assets held in NDT funds, along with the assumption of liability for all responsibility for the site, including full decommissioning and ongoing management of spent fuel until the spent fuel is moved offsite. The terms of the transaction also include various forms of performance assurance for the obligations of OCEP to timely complete the required decommissioning, including a parental guaranty from Holtec for all performance and payment obligations of OCEP, and a requirement for Holtec to deliver a letter of credit to Generation upon the occurrence of specified events. As a result of the transaction, in the third quarter of 2018, Exelon and Generation reclassified certain Oyster Creek assets and liabilities in Exelon’s and Generation’s Consolidated Balance Sheets as held for sale at their respective fair value s. Exelon and Generation had $897 million and $777 million of Assets and Liabilities held for sale, respectively, at December 31, 2018 . Upon remeasurement of the Oyster Creek ARO, Exelon and Generation recognized an $84 million and a $9 million pre-tax charge to Operating and maintenance expense in the third quarter of 2018 and in the second quarter of 2019, respectively. See Note 13 — Nuclear Decommissioning for additional information. Other Asset Disposition On February 28, 2018, Generation completed the sale of its interest in an electrical contracting business that primarily installs, maintains and repairs underground and high-voltage cable transmission and distribution systems for $87 million , resulting in a pre-tax gain which is included within Gain on sales of assets and businesses in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income for the nine months ended September 30, 2018 .

Revenue from Contracts with Cus

Revenue from Contracts with Customers (All Registrants)	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers [Text Block]	Revenue from Contracts with Customers (All Registrants) The Registrants recognize revenue from contracts with customers to depict the transfer of goods or services to customers at an amount that the entities expect to be entitled to in exchange for those goods or services. Generation’s primary sources of revenue include competitive sales of power, natural gas, and other energy-related products and services. The Utility Registrants’ primary sources of revenue include regulated electric and gas tariff sales, distribution and transmission services. See Note 3 — Revenue from Contracts with Customers of the Exelon 2018 Form 10-K for additional information regarding the primary sources of revenue for the Registrants. Contract Balances (All Registrants) Contract Assets and Liabilities Generation records contract assets for the revenue recognized on the construction and installation of energy efficiency assets and new power generating facilities before Generation has an unconditional right to bill for and receive the consideration from the customer. These contract assets are subsequently reclassified to receivables when the right to payment becomes unconditional. Generation records contract assets and contract receivables within Other current assets and Accounts receivable, net - Customer, respectively, within Exelon’s and Generation’s Consolidated Balance Sheets. Generation records contract liabilities when consideration is received or due prior to the satisfaction of the performance obligations. These contract liabilities primarily relate to upfront consideration received or due for equipment service plans, solar panel leases and the Illinois ZEC program that introduces a cap on the total consideration to be received by Generation. Generation records contract liabilities within Other current liabilities and Other noncurrent liabilities within Exelon's and Generation's Consolidated Balance Sheets. The following table provides a rollforward of the contract assets and liabilities reflected in Exelon's and Generation's Consolidated Balance Sheets from January 1, 2018 to September 30, 2019 : Contract Assets Contract Liabilities Exelon Generation Exelon Generation Balance as of January 1, 2018 $ 283 $ 283 $ 35 $ 35 Consideration received or due (146 ) (146 ) 179 465 Revenues recognized 50 50 (187 ) (458 ) Balance at December 31, 2018 187 187 27 42 Consideration received or due (109 ) (109 ) 65 198 Revenues recognized 92 92 (66 ) (192 ) Balance at September 30, 2019 170 170 26 48 The Utility Registrants do not have any contract assets. The Utility Registrants also record contract liabilities when consideration is received prior to the satisfaction of the performance obligations. As of September 30, 2019 and December 31, 2018 , the Utility Registrants' contract liabilities were immaterial. Transaction Price Allocated to Remaining Performance Obligations (All Registrants) The following table shows the amounts of future revenues expected to be recorded in each year for performance obligations that are unsatisfied or partially unsatisfied as of September 30, 2019 . This disclosure only includes contracts for which the total consideration is fixed and determinable at contract inception. The average contract term varies by customer type and commodity but ranges from one month to several years. This disclosure excludes Generation's power and gas sales contracts as they contain variable volumes and/or variable pricing. This disclosure also excludes the Utility Registrants' gas and electric tariff sales contracts and transmission revenue contracts as they generally have an original expected duration of one year or less and, therefore, do not contain any future, unsatisfied performance obligations to be included in this disclosure. 2019 2020 2021 2022 2023 and thereafter Total Exelon 156 341 142 74 244 957 Generation 215 442 197 89 244 1,187 Revenue Disaggregation (All Registrants) The Registrants disaggregate revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. See Note 18 — Segment Information for the presentation of the Registrant's revenue disaggregation.

Leases (All Registrants)

Leases (All Registrants)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Lessee, Finance and Operating Leases [Text Block]	Leases (All Registrants) Lessee The Registrants have operating leases for which they are the lessees. The following tables outline the significant types of operating leases at each registrant and other terms and conditions of the lease agreements. The Registrants do not have material finance leases. Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Contracted generation ● ● Real estate ● ● ● ● ● ● ● ● ● Vehicles and equipment ● ● ● ● ● ● ● ● ● (in years) Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Remaining lease terms 1-87 1-37 1-6 1-15 1-87 1-13 1-13 1-13 1-8 Options to extend the term 3-30 3-30 5 N/A N/A 3-30 5 3-30 N/A Options to terminate within 2-14 2 4 N/A 3 N/A N/A N/A N/A The components of lease costs for the three months ended September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Operating lease costs $ 97 $ 73 $ 1 $ — $ 8 $ 12 $ 3 $ 3 $ 2 Variable lease costs 79 74 — — 1 1 — — — Short-term lease costs 5 5 — — — — — — — Total lease costs (a) $ 181 $ 152 $ 1 $ — $ 9 $ 13 $ 3 $ 3 $ 2 __________ (a) Excludes $29 million , $28 million , $1 million and $1 million of sublease income recorded at Exelon, Generation, PHI and DPL, respectively The components of lease costs for the nine months ended September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Operating lease costs $ 252 $ 180 $ 2 $ 1 $ 25 $ 35 $ 9 $ 10 $ 5 Variable lease costs 229 214 1 — 1 5 2 2 1 Short-term lease costs 16 16 — — — — — — — Total lease costs (a) $ 497 $ 410 $ 3 $ 1 $ 26 $ 40 $ 11 $ 12 $ 6 __________ (a) Excludes $48 million , $42 million , $6 million and $6 million of sublease income recorded at Exelon, Generation, PHI and DPL, respectively. The following table provides additional information regarding the presentation of operating lease ROU assets and lease liabilities within the Registrants’ Consolidated Balance Sheets as of September 30, 2019 : Exelon (a) Generation (a) ComEd PECO BGE PHI Pepco DPL ACE Operating lease ROU assets Other deferred debits and other assets $ 1,374 $ 926 $ 10 $ 2 $ 83 $ 304 $ 66 $ 75 $ 24 Operating lease liabilities Other current liabilities 242 170 3 — 32 35 8 11 5 Other deferred credits and other liabilities 1,355 949 8 1 50 279 60 74 19 Total operating lease liabilities $ 1,597 $ 1,119 $ 11 $ 1 $ 82 $ 314 $ 68 $ 85 $ 24 __________ (a) Exelon's and Generation's operating ROU assets and lease liabilities include $542 million and $703 million , respectively, related to contracted generation. The weighted average remaining lease terms, in years, and discount rates for operating leases as of September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Remaining lease term 10.1 10.6 4.7 4.3 5.6 9.0 9.6 9.5 5.3 Discount rate 4.5 % 4.8 % 3.1 % 3.3 % 3.6 % 4.0 % 3.7 % 3.7 % 3.3 % Future minimum lease payments for operating leases as of September 30, 2019 were as follows: Year Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE 2019 $ 65 $ 50 $ 1 $ — $ 1 $ 11 $ 3 $ 2 $ 2 2020 289 203 3 1 34 45 10 13 5 2021 246 162 3 — 31 43 9 12 5 2022 179 113 2 — 16 42 9 12 4 2023 148 100 1 — — 41 8 11 4 Remaining years 1,123 837 2 — 19 197 43 53 6 Total 2,050 1,465 12 1 101 379 82 103 26 Interest 453 346 1 — 19 65 14 18 2 Total operating lease liabilities $ 1,597 $ 1,119 $ 11 $ 1 $ 82 $ 314 $ 68 $ 85 $ 24 Future minimum lease payments for operating leases under the prior lease accounting guidance as of December 31, 2018 were as follows: Year Exelon (a)(b) Generation (a)(b) ComEd (a)(c) PECO (a)(c) BGE (a)(c)(d)(e) PHI (a) Pepco (a) DPL (a)(c) ACE (a) 2019 $ 140 $ 33 $ 7 $ 5 $ 35 $ 48 $ 11 $ 14 $ 7 2020 149 46 5 5 35 46 10 13 6 2021 143 46 4 5 33 43 9 12 5 2022 126 47 4 5 18 42 8 12 5 2023 97 46 3 5 3 39 8 10 4 Remaining years 723 545 — — 19 159 40 35 5 Total minimum future lease payments $ 1,378 $ 763 $ 23 $ 25 $ 143 $ 377 $ 86 $ 96 $ 32 __________ (a) Includes amounts related to shared use land arrangements. (b) Excludes Generation’s contingent operating lease payments associated with contracted generation. (c) Amounts related to certain real estate leases and railroad licenses effectively have indefinite payment periods. As a result, ComEd, PECO, BGE and DPL have excluded these payments from the remaining years as such amounts would not be meaningful. ComEd's, PECO’s, BGE’s and DPL's average annual obligation for these arrangements, included in each of the years 2019 - 2023, was $3 million , $5 million , $1 million and $1 million respectively. Also includes amounts related to shared use land arrangements. (d) Includes all future lease payments on a 99-year real estate lease that expires in 2106. (e) The BGE column above includes minimum future lease payments associated with a 6-year lease for the Baltimore City conduit system that became effective during the fourth quarter of 2016. BGE's total commitments under the lease agreement are $26 million , $28 million , $28 million and $14 million related to years 2019 - 2022, respectively. Cash paid for amounts included in the measurement of lease liabilities for the nine months ended September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Operating cash flows from operating leases $ 225 $ 156 $ 2 $ — $ 32 $ 29 $ 7 $ 6 $ 4 ROU assets obtained in exchange for lease obligations for the nine months ended September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Operating leases $ 70 $ 11 $ 6 $ — $ 1 $ 20 $ 7 $ 9 $ 4
Lessor, Operating Leases [Text Block]	Lessor The Registrants have operating leases for which they are the lessors. The following tables outline the significant types of leases at each registrant and other terms and conditions of their lease agreements. Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Contracted generation ● ● Real estate ● ● ● ● ● ● ● ● ● (in years) Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Remaining lease terms 1-84 1-33 1-18 1-84 24 1-14 2-7 13-14 1-3 Options to extend the term 1-79 1-5 5-79 5-50 N/A 5 N/A N/A N/A The components of lease income for the three months ended September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Operating lease income $ 30 $ 29 $ — $ — $ — $ 1 $ — $ 1 $ — Variable lease income 80 80 — — — — — — — The components of lease income for the nine months ended September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Operating lease income $ 48 $ 44 $ — $ — $ — $ 3 $ — $ 3 $ — Variable lease income 209 206 — — — 3 — 3 — Future minimum lease payments to be recovered under operating leases as of September 30, 2019 were as follows: Year Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE 2019 $ 4 $ 3 $ — $ — $ — $ 1 $ — $ 1 $ — 2020 51 46 — — — 4 — 3 — 2021 50 45 — — — 4 1 3 — 2022 50 45 — — — 5 — 4 — 2023 49 45 — — — 4 — 3 — Remaining years 314 271 1 3 1 38 — 38 — Total $ 518 $ 455 $ 1 $ 3 $ 1 $ 56 $ 1 $ 52 $ — Leases (All Registrants)

Regulatory Matters (All Registr

Regulatory Matters (All Registrants)	9 Months Ended
	Sep. 30, 2019
Regulated Operations [Abstract]
Regulatory Matters (All Registrants)	Regulatory Matters (All Registrants) As discussed in Note 4 — Regulatory Matters of the Exelon 2018 Form 10-K, the Registrants are involved in rate and regulatory proceedings at the FERC and their state commissions. The following discusses developments in 2019 and updates to the 2018 Form 10-K. Utility Regulatory Matters (Exelon and the Utility Registrants) Distribution Base Rate Case Proceedings The following tables show the completed and pending distribution base rate case proceedings in 2019. Completed Distribution Base Rate Case Proceedings Registrant/Jurisdiction Filing Date Requested Revenue Requirement (Decrease) Increase Approved Revenue Requirement (Decrease) Increase Approved ROE Approval Date Rate Effective Date ComEd - Illinois (Electric) April 16, 2018 $ (23 ) $ (24 ) 8.69% December 4, 2018 January 1, 2019 PECO - Pennsylvania (Electric) March 29, 2018 $ 82 $ 25 N/A (a) December 20, 2018 January 1, 2019 BGE - Maryland (Natural Gas) June 8, 2018 (amended October 12, 2018) $ 61 $ 43 9.8% January 4, 2019 January 4, 2019 ACE - New Jersey (Electric) August 21, 2018 (amended November 19, 2018) $ 122 (b) $ 70 (b) 9.6% March 13, 2019 April 1, 2019 Pepco - Maryland (Electric) January 15, 2019 (amended May 16, 2019) $ 27 $ 10 9.6% August 12, 2019 August 13, 2019 __________ (a) The PECO rate case proceeding was resolved through a settlement agreement, which did not specify an approved ROE. (b) Requested and approved increases are before New Jersey sales and use tax. Pending Distribution Base Rate Case Proceedings Registrant/Jurisdiction Filing Date Requested Revenue Requirement (Decrease) Increase Requested ROE Expected Approval Timing ComEd - Illinois (Electric) (a) April 8, 2019 $ (6 ) 8.91 % December 2019 BGE - Maryland (Electric) (b) May 24, 2019 (amended October 4, 2019) $ 74 10.3 % December 2019 BGE - Maryland (Natural Gas) (b) May 24, 2019 (amended October 4, 2019) $ 59 10.3 % December 2019 Pepco - District of Columbia (Electric) (c) May 30, 2019 (amended September 16, 2019) $ 160 10.3 % Fourth quarter of 2020 __________ (a) Reflects an increase of $57 million for the initial revenue requirement for 2019 and a decrease of $63 million related to the annual reconciliation for 2018. The revenue requirement for 2019 and annual reconciliation for 2018 provides for a weighted average debt and equity return on distribution rate base of 6.53% . See Note 4 — Regulatory Matters of the Exelon 2018 Form 10-K for additional information on ComEd's distribution formula rate filings. (b) On October 25, 2019, BGE filed a settlement agreement with the MDPSC. The settlement provides for an increase to BGE’s annual electric and natural gas distribution rates of $18 million and $45 million , respectively. (c) Reflects a three-year cumulative multi-year plan and total requested revenue requirement increases of $84 million , $40 million and $36 million for years 2020, 2021, and 2022, respectively, to recover capital investments made in 2018 and 2019 and planned capital investments from 2020 to 2022. Transmission Formula Rates Transmission Formula Rate (Exelon, ComEd, BGE, PHI, Pepco, DPL and ACE). ComEd’s, BGE’s, Pepco's, DPL's and ACE's transmission rates are each established based on a FERC-approved formula. ComEd, BGE, Pepco, DPL and ACE 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 (initial year revenue requirement). 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 (annual reconciliation). For 2019, the following total increases/(decreases) were included in ComEd’s, BGE’s, Pepco's, DPL's and ACE's electric transmission formula rate filings: Registrant (a) Initial Revenue Requirement Increase (Decrease) Annual Reconciliation (Decrease) Increase Total Revenue Requirement Increase (Decrease) Allowed Return on Rate Base (c) Allowed ROE (d) ComEd $ 21 $ (16 ) $ 5 8.21 % 11.50 % BGE (10 ) (23 ) (19 ) (b) 7.35 % 10.50 % Pepco 15 11 26 7.75 % 10.50 % DPL 17 (1 ) 16 7.14 % 10.50 % ACE 11 (2 ) 9 7.79 % 10.50 % __________ (a) All rates are effective June 2019 , subject to review by the FERC and other parties, which is due by the fourth quarter of 2019 . (b) The change in BGE's transmission revenue requirement includes a FERC approved dedicated facilities charge of $14 million to recover the costs of providing transmission service to specifically designated load by BGE. (c) Represents the weighted average debt and equity return on transmission rate bases. (d) As part of the FERC-approved settlement of ComEd’s 2007 transmission rate case, the rate of return on common equity is 11.50% , inclusive of a 50-basis-point incentive adder for being a member of a RTO, and the common equity component of the ratio used to calculate the weighted average debt and equity return for the transmission formula rate is currently capped at 55% . As part of the FERC-approved settlement of the ROE complaint against BGE, Pepco, DPL and ACE, the rate of return on common equity is 10.50% , inclusive of a 50-basis-point incentive adder for being a member of a RTO. Pending Transmission Formula Rate (Exelon and PECO). On May 1, 2017, PECO filed a request with FERC seeking approval to update its transmission rates and change the manner in which PECO’s transmission rate is determined from a fixed rate to a formula rate. The formula rate will be updated annually to ensure that under this rate customers pay the actual costs of providing transmission services. PECO’s initial formula rate filing included a requested increase of $22 million to PECO’s annual transmission revenue requirement, which reflected a ROE of 11% , inclusive of a 50 basis point adder for being a member of a RTO. On June 27, 2017, FERC issued an Order accepting the filing and suspending the proposed rates until December 1, 2017, subject to refund, and set the matter for hearing and settlement judge procedures. Pursuant to the transmission formula rate request discussed above, PECO made its annual formula rate updates in May 2018 and 2019, which included a decrease of $6 million and an increase of $8 million , respectively, to the annual transmission revenue requirement. The updated transmission formula rates were effective on June 1, 2018 and 2019, respectively, subject to refund. On July 22, 2019, PECO and other parties filed with FERC a settlement agreement, which includes a ROE of 10.35% , inclusive of a 50 basis point adder for being a member of a RTO. The settlement did not have a material impact on PECO’s 2017, 2018, or 2019 annual transmission revenue requirements. A final order from FERC is expected before the end of the first quarter of 2020. PECO cannot predict the outcome of this proceeding, or the transmission formula FERC may approve. Other State Regulatory Matters Energy Efficiency Formula Rate. ComEd filed its annual energy efficiency formula rate update with the ICC on May 23, 2019. The filing establishes the revenue requirement used to set the rates that will take effect in January 2020 after the ICC’s review and approval. The revenue requirement requested is based on a reconciliation of the 2018 actual costs plus projected 2019 and 2020 expenditures. Registrant Initial Revenue Requirement Increase (Decrease) Annual Reconciliation Increase (Decrease) Total Revenue Requirement Increase (Decrease) Requested Return on Rate Base Requested ROE ComEd $ 53 $ (2 ) $ 51 (a) 6.53 % 8.91 % __________ (a) The requested revenue requirement increase provides for a weighted average debt and equity return on rate base of 6.53% inclusive of an allowed ROE of 8.91% . The ROE reflects the average rate on 30-year treasury notes plus 580 basis points. The ROE applicable to the 2018 reconciliation year is 10.91% and the return on rate base is 7.49% , which include the Performance Adjustment, which can either increase or decrease the ROE by up to a maximum of 200 basis points. Maryland Regulatory Matters Maryland Alternative Rate Plans Rulemaking (Exelon, BGE, PHI, Pepco and DPL). On August 9, 2019, the MDPSC issued an order in which the MDPSC determined that it is now appropriate to move forward to implement alternative rate plans in Maryland. The MDPSC found that a multi-year rate plan, based on a historic test year and allowing up to three future test years, can produce just and reasonable rates. A working group has been convened to develop and submit a detailed implementation report to the MDPSC by December 20, 2019. The MDPSC will issue another order on next steps by January 30, 2020. BGE, Pepco and DPL cannot predict the outcome or the potential financial impact, if any, on BGE, Pepco or DPL. New Jersey Regulatory Matters ACE Infrastructure Investment Program Filing (Exelon, PHI and ACE). On February 28, 2018, ACE filed with the NJBPU the company’s Infrastructure Investment Program (IIP) proposing to seek recovery of a series of investments through a new rider mechanism, totaling $338 million , between 2019-2022 to provide safe and reliable service for its customers. The IIP allowed for more timely recovery of investments made to modernize and enhance ACE’s electric system. On April 15, 2019, ACE entered into a settlement agreement with other parties, which allows for a recovery totaling $96 million of reliability related capital investments from July 1, 2019 through June 30, 2023. On April 18, 2019, the NJBPU approved the settlement agreement. New Jersey Clean Energy Legislation (Exelon, PHI and ACE). On May 23, 2018, New Jersey enacted legislation that established and modified New Jersey’s clean energy and energy efficiency programs and solar and renewable energy portfolio standards. On the same day, New Jersey enacted legislation that established a ZEC program that provides compensation for nuclear plants that demonstrate to the NJBPU that they meet certain requirements, including that they make a significant contribution to air quality in the state and that their revenues are insufficient to cover their costs and risks. Electric distribution utilities in New Jersey, including ACE, began collecting from retail distribution customers, through a non-bypassable charge, all costs associated with the utility’s procurement of the ZECs effective April 18, 2019. See Generation Regulatory Matters below for additional information. Other Federal Regulatory Matters Transmission-Related Income Tax Regulatory Assets (Exelon, ComEd, BGE, PHI, Pepco, DPL and ACE). On December 13, 2016 (and as amended on March 13, 2017), BGE filed with FERC to begin recovering certain existing and future transmission-related income tax regulatory assets through its transmission formula rate. BGE’s existing regulatory assets included (1) amounts that, if BGE’s transmission formula rate provided for recovery, would have been previously amortized and (2) amounts that would be amortized and recovered prospectively. ComEd, Pepco, DPL and ACE had similar transmission-related income tax regulatory liabilities and assets also requiring FERC approval. On November 16, 2017, FERC issued an order rejecting BGE’s proposed revisions to its transmission formula rate to recover these transmission-related income tax regulatory assets. As a result of the FERC’s order, ComEd, BGE, Pepco, DPL and ACE took a charge to Income tax expense within their Consolidated Statements of Operations and Comprehensive Income in the fourth quarter of 2017 reducing their associated transmission-related income tax regulatory assets for the portion of the total transmission-related income tax regulatory assets that would have been previously amortized and recovered through rates. Similar regulatory assets and liabilities at PECO are not subject to the same FERC transmission rate recovery formula. See above for additional information regarding PECO's transmission formula rate filing. On December 18, 2017, BGE filed for clarification and rehearing of FERC’s November 16, 2017 order and on February 23, 2018 (as amended on July 9, 2018), ComEd, Pepco, DPL, and ACE each filed with FERC to revise their transmission formula rate mechanisms to permit recovery of transmission-related income tax regulatory assets, including those amounts that would have been previously amortized and recovered through rates had the transmission formula rate provided for such recovery. On September 7, 2018, FERC issued orders rejecting BGE’s December 18, 2017 request for rehearing and clarification and ComEd's, Pepco's, DPL's and ACE's February 23, 2018 (as amended on July 9, 2018) filings, citing the lack of timeliness of the requests to recover amounts that would have been previously amortized, but indicating that ongoing recovery of certain transmission-related income tax regulatory assets would provide for a more accurate revenue requirement, consistent with its November 16, 2017 order. On October 1, 2018, ComEd, BGE, Pepco, DPL, and ACE submitted filings to recover ongoing non-TCJA amortization amounts and refund TCJA transmission-related income tax regulatory liabilities for the prospective period starting on October 1, 2018. In addition, on October 9, 2018, ComEd, Pepco, DPL, and ACE sought rehearing of FERC's September 7, 2018 order. On November 2, 2018, BGE filed an appeal of FERC’s September 7, 2018 order to the Court of Appeals for the D.C. Circuit. On April 26, 2019, FERC issued an order accepting ComEd’s, BGE’s, Pepco’s, DPL’s, and ACE’s October 1, 2018 filings, effective October 1, 2018, subject to refund and established hearing and settlement judge procedures. ComEd, BGE, Pepco, DPL, and ACE cannot predict the outcome of these proceedings. If FERC ultimately rules that the future, ongoing non-TCJA amortization amounts are not recoverable, Exelon, ComEd, BGE, PHI, Pepco, DPL and ACE would record additional charges to Income tax expense, which could be up to approximately $80 million , $52 million , $16 million , $12 million , $4 million , $6 million and $2 million , respectively, as of September 30, 2019 . Regulatory Assets and Liabilities The Utility Registrants' regulatory assets and liabilities have not changed materially since December 31, 2018, unless noted below. See Note 4 — Regulatory Matters of the Exelon 2018 Form 10-K for additional information on the specific regulatory assets and liabilities. ComEd . Regulatory assets increased $122 million primarily due to an increase of $186 million in Energy Efficiency Costs and $32 million Renewable Energy partially offset by a decrease of $97 million in Electric Distribution Formula Rate Annual Reconciliations. PECO. Regulatory assets increased $62 million primarily due to an increase of $95 million in Deferred Income Taxes offset by a $34 million decrease in Electric Energy and Natural Gas Costs. BGE . Regulatory liabilities decreased $90 million primarily due to a decrease of $40 million in Deferred Income Taxes and $43 million in Removal Costs. Pepco. Regulatory assets decreased $84 million primarily due to a decrease of $39 million in Electric Energy and Natural Gas Costs, $26 million in DC PLUG charge and $14 million in AMI Programs - Deployment Costs and Legacy Meters. Regulatory liabilities decreased by $71 million primarily due to a decrease of $73 million in Deferred Income Taxes. DPL. Regulatory liabilities decreased $42 million primarily due to a decrease of $29 million in Deferred Income Taxes and $10 million in Electric Energy and Natural Gas Costs. ACE. Regulatory liabilities decreased $30 million primarily due to a decrease of $32 million in Deferred Income Taxes. Capitalized Ratemaking Amounts Not Recognized (Exelon and the Utility Registrants) The following table presents authorized amounts capitalized for ratemaking purposes related to earnings on shareholders’ investment that are not recognized for financial reporting purposes in Exelon's and the Utility Registrant's Consolidated Balance Sheets. These amounts will be recognized as revenues in the related Consolidated Statements of Operations and Comprehensive Income in the periods they are billable to our customers. Exelon ComEd (a) PECO BGE (b) PHI Pepco (c) DPL (c) ACE September 30, 2019 $ 59 $ 4 $ — $ 47 $ 8 $ 5 $ 3 $ — December 31, 2018 $ 65 $ 8 $ — $ 49 $ 8 $ 5 $ 3 $ — _________ (a) Reflects ComEd's unrecognized equity returns earned for ratemaking purposes on its electric distribution formula rate regulatory assets. (b) BGE's authorized amounts capitalized for ratemaking purposes primarily relate to earnings on shareholders' investment on its AMI programs. (c) Pepco's and DPL's authorized amounts capitalized for ratemaking purposes relate to earnings on shareholders' investment on their respective AMI Programs and Energy Efficiency and Demand Response Programs. The earnings on energy efficiency are on Pepco DC and DPL DE programs only. Generation Regulatory Matters (Exelon and Generation) Illinois Regulatory Matters Zero Emission Standard. Pursuant to FEJA, on January 25, 2018, the ICC announced that Generation’s Clinton Unit 1, Quad Cities Unit 1 and Quad Cities Unit 2 nuclear plants were selected as the winning bidders through the IPA's ZEC procurement event. Generation executed the ZEC procurement contracts with Illinois utilities, including ComEd, effective January 26, 2018 and began recognizing revenue with compensation for the sale of ZECs retroactive to the June 1, 2017 effective date of FEJA. During the first quarter of 2018, Generation recognized $150 million of revenue related to ZECs generated from June 1, 2017 through December 31, 2017. On February 14, 2017, two lawsuits were filed in the Northern District of Illinois against the IPA alleging that the state’s ZEC program violates certain provisions of the U.S. Constitution. Both lawsuits argued that the Illinois ZEC program would distort PJM's FERC-approved energy and capacity market auction system of setting wholesale prices and sought a permanent injunction preventing the implementation of the program. The lawsuits were dismissed by the district court on July 14, 2017. On September 13, 2018, the U.S. Circuit Court of Appeals for the Seventh Circuit affirmed the lower court's dismissal of both lawsuits. On January 7, 2019, plaintiffs filed a petition seeking U.S. Supreme Court review of the case, which was denied on April 15, 2019. New Jersey Regulatory Matters New Jersey Clean Energy Legislation. On May 23, 2018, New Jersey enacted legislation that established a ZEC program that will provide compensation for nuclear plants that demonstrate to the NJBPU that they meet certain requirements, including that they make a significant contribution to air quality in the state and that their revenues are insufficient to cover their costs and risks. Under the legislation, the NJBPU will issue ZECs to qualifying nuclear power plants and the electric distribution utilities in New Jersey, including ACE, will be required to purchase those ZECs. On November 19, 2018, NJBPU issued an order providing for the method and application process for determining the eligibility of nuclear power plants, a draft method and process for ranking and selecting eligible nuclear power plants, and the establishment of a mechanism for each regulated utility to purchase ZECs from selected nuclear power plants. On December 19, 2018, PSEG filed complete applications seeking NJBPU approval for Salem 1 and Salem 2, of which Generation owns a 42.59% ownership interest, to participate in the ZEC program. On April 18, 2019, the NJBPU approved the award of ZECs to Salem 1 and Salem 2. Upon approval, Generation began recognizing revenue for the sale of New Jersey ZECs in the month they are generated and has recognized $21 million and $31 million for the three and nine months ended September 30, 2019 . On May 15, 2019, New Jersey Rate Counsel appealed the NJBPU's decision to the New Jersey Superior Court. The appeal does not prevent implementation of the ZEC program. Exelon and Generation cannot predict the outcome of the appeal. See Note 8 — Early Plant Retirements for additional information related to Salem. New York Regulatory Matters New York Clean Energy Standard. On August 1, 2016, the NYPSC issued an order establishing the New York CES, a component of which is a Tier 3 ZEC program targeted at preserving the environmental attributes of zero-emissions nuclear-powered generating facilities that meet the criteria demonstrating public necessity as determined by the NYPSC. On October 19, 2016, a coalition of fossil-generation companies filed a complaint in federal district court against the NYPSC alleging that the ZEC program violates certain provisions of the U.S. Constitution; specifically, that the ZEC program interferes with FERC’s jurisdiction over wholesale rates and that it discriminates against out of state competitors, which was dismissed by the district court on July 25, 2017. On September 27, 2018, the U.S. Court of Appeals for the Second Circuit affirmed the lower court's dismissal of the complaint against the ZEC program. On January 7, 2019, the fossil-generation companies filed a petition seeking U.S. Supreme Court review of the case which was denied on April 15, 2019. In addition, on November 30, 2016 (as amended on January 13, 2017), a group of parties filed a Petition in New York State court seeking to invalidate the ZEC program, which argued that the NYPSC did not have authority to establish the program, that it violated state environmental law and that it violated certain technical provisions of the State Administrative Procedures Act when adopting the ZEC program. Subsequently, Generation, CENG and the NYPSC filed motions to dismiss the state court action, which were later opposed by the plaintiffs. On January 22, 2018, the court dismissed the environmental claims and the majority of the plaintiffs from the case but denied the motions to dismiss with respect to the remaining five plaintiffs and claims, without commenting on the merits of the case. On October 8, 2019, the court dismissed all remaining claims. The petitioners have until November 11, 2019 to file a notice of appeal. See Note 8 — Early Plant Retirements for additional information related to Ginna and Nine Mile Point. Federal Regulatory Matters Operating License Renewals Conowingo Hydroelectric Project. On August 29, 2012, Generation submitted a hydroelectric license application to FERC for a new license for the Conowingo Hydroelectric Project (Conowingo). In connection with Generation’s efforts to obtain a water quality certification pursuant to Section 401 of the Clean Water Act (401 Certification) from MDE for Conowingo, Generation has been working with MDE and other stakeholders to resolve water quality licensing issues, including: (1) water quality, (2) fish habitat, and (3) sediment. On April 21, 2016, Generation and the U.S. Fish and Wildlife Service of the U.S. Department of the Interior executed a settlement agreement (DOI Settlement) resolving all fish passage issues between the parties. On April 27, 2018, MDE issued its 401 Certification for Conowingo. As issued, the 401 Certification contains numerous conditions, including those relating to reduction of nutrients from upstream sources, removal of all visible trash and debris from upstream sources, and implementation of measures relating to fish passage, which could have a material, unfavorable impact on Exelon’s and Generation’s financial statements through an increase in capital expenditures and operating costs if implemented. On May 25, 2018, Generation filed complaints in federal and state court, along with a petition for reconsideration with MDE, alleging that the conditions are unfair and onerous and in violation of MDE regulations and state, federal, and constitutional law. Generation also requested that FERC defer the issuance of the federal license while these significant state and federal law issues are pending. On February 28, 2019, Generation filed a Petition for Declaratory Order with FERC requesting that FERC issue an order declaring that MDE waived its right to issue a 401 Certification for Conowingo because it failed to timely act on Conowingo's 401 Certification application and requesting that FERC decline to include the conditions required by MDE in April 2018. On October 29, 2019, Generation and MDE entered into a settlement agreement (MDE Settlement) that would resolve all outstanding issues relating to the 401 Certification. Under the MDE Settlement, the parties will propose license articles to FERC for approval as an offer of settlement to be incorporated by FERC into the new license in accordance with FERC’s discretionary authority under the Federal Power Act. The MDE Settlement provides that if FERC approves the offer of settlement, MDE would waive its rights to issue a 401 Certification and Generation would agree to implement environmental protection, mitigation and enhancement measures over the anticipated 50-year term of the new license. These measures address ecological and water quality matters, including modifications to river flows to improve aquatic habitat, along with other additional fish and eel passage improvements and initiatives to support rare, threatened and endangered wildlife, among other commitments. Exelon’s commitments under the DOI and MDE Settlements are not effective until incorporated by FERC into the new license. The financial impact of the DOI and MDE Settlements and other anticipated license commitments are estimated to be $11 million to $14 million per year, on average, recognized over the new license term, including capital and operating costs. The actual timing and amount of the majority of these costs are not currently fixed and will vary from year to year throughout the life of the new license. Generation cannot currently predict when FERC will issue the new license. As of September 30, 2019 , $41 million of direct costs associated with Conowingo licensing efforts have been capitalized. Generation’s current depreciation provision for Conowingo assumes renewal of the FERC license.

Asset Impairments (Exelon and G

Asset Impairments (Exelon and Generation)	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Asset Impairment Charges [Text Block]	Asset Impairments (Exelon and Generation) The Registrants evaluate the carrying value of long-lived assets or asset groups for recoverability whenever events or changes in circumstances indicate that the carrying value of those assets may not be recoverable. Indicators of impairment may include a deteriorating business climate, including, but not limited to, declines in energy prices, condition of the asset, specific regulatory disallowance, or plans to dispose of a long-lived asset significantly before the end of its useful life. The Registrants determine if long-lived assets or asset groups are impaired by comparing the undiscounted expected future cash flows to the carrying value. When the undiscounted cash flow analysis indicates a long-lived asset or asset group is not recoverable, the amount of the impairment loss is determined by measuring the excess of the carrying amount of the long-lived asset or asset group over its fair value. The fair value analysis is 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. A variation in the assumptions used could lead to a different conclusion regarding the recoverability of an asset or asset group and, thus, could potentially result in material future impairments of the Registrant's long-lived assets. Equity Method Investments in Certain Distributed Energy Companies In the third quarter of 2019, Generation’s equity method investments in certain distributed energy companies were fully impaired due to an other-than-temporary decline in market conditions and underperforming projects. Exelon and Generation recorded a pre-tax impairment charge of $164 million in Equity in losses of unconsolidated affiliates and an offsetting pre-tax $96 million in Net income attributable to noncontrolling interests in their Consolidated Statements of Operations and Comprehensive Income. As a result, Generation accelerated the amortization of investment tax credits associated with these companies and Exelon and Generation recorded a benefit of $46 million in Income taxes. The impairment charge and the accelerated amortization of investment tax credits resulted in a net $15 million decrease to Exelon’s and Generation’s earnings. See Note 2 — Variable Interest Entities for additional information. Antelope Valley Solar Facility Generation’s Antelope Valley, a 242 MW solar facility in Lancaster, CA, sells all of its output to PG&E through a PPA. As of September 30, 2019 , Generation had approximately $730 million of net long-lived assets related to Antelope Valley. As a result of the PG&E bankruptcy filing in the first quarter of 2019, Generation completed a comprehensive review of Antelope Valley's estimated undiscounted future cash flows and no impairment charge was recorded. Significant changes in assumptions such as the likelihood of the PPA being rejected as part of the bankruptcy proceedings could potentially result in future impairments of Antelope Valley’s net long-lived assets, which could be material. Antelope Valley is a wholly owned indirect subsidiary of EGR IV, which had approximately $1,930 million of additional net long-lived assets as of September 30, 2019 . EGR IV is a wholly owned indirect subsidiary of Exelon and Generation and includes Generation's interest in EGRP and other projects with non-controlling interests. To date, there have been no indicators to suggest that the carrying amount of other net long-lived assets of EGR IV may not be recoverable. Generation will continue to monitor the bankruptcy proceedings for any changes in circumstances that may indicate the carrying amount of the net long-lived assets of Antelope Valley or other long-lived assets of EGR IV may not be recoverable. See Note 11 - Debt and Credit Agreements for additional information on the PG&E bankruptcy.

Early Plant Retirements (Exelon

Early Plant Retirements (Exelon and Generation)	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Early Plant Retirements (Exelon and Generation)	Early Plant Retirements (Exelon and Generation) Exelon and Generation continuously evaluate factors that affect the current and expected economic value of Generation’s plants, including, but not limited to: market power prices, results of capacity auctions, potential legislative and regulatory solutions to ensure plants are fairly compensated for benefits they provide through their carbon-free emissions, reliability, or fuel security, and the impact of potential rules from the EPA requiring reduction of carbon and other emissions and the efforts of states to implement those final rules. The precise timing of an early retirement date for any plant, and the resulting financial statement impacts, may be affected by many factors, including the status of potential regulatory or legislative solutions, results of any transmission system reliability study assessments, the nature of any co-owner requirements and stipulations, and NDT fund requirements for nuclear plants, 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 or other obligations, and where applicable, just prior to its next scheduled nuclear refueling outage. Nuclear Generation In 2015 and 2016, Generation identified the Clinton and Quad Cities nuclear plants in Illinois, Ginna and Nine Mile Point nuclear plants in New York and Three Mile Island nuclear plant in Pennsylvania as having the greatest risk of early retirement based on economic valuation and other factors. In 2017, PSEG made public similar financial challenges facing its New Jersey nuclear plants, including Salem, of which Generation owns a 42.59% ownership interest. PSEG is the operator of Salem and also has the decision-making authority to retire Salem. Assuming the continued effectiveness of the Illinois ZES, New Jersey ZEC program and the New York CES, Generation and CENG, through its ownership of Ginna and Nine Mile Point, no longer consider Clinton, Quad Cities, Salem, Ginna or Nine Mile Point to be at heightened risk for early retirement. However, to the extent the Illinois ZES, New Jersey ZEC program or the New York CES do not operate as expected over their full terms, each of these plants could again be at heightened risk for early retirement, which could have a material impact on Exelon’s and Generation’s future financial statements. See Note 6 — Regulatory Matters for additional information on the Illinois ZES, New Jersey ZEC program and New York CES. In Pennsylvania, the TMI nuclear plant did not clear in the May 2017 PJM capacity auction for the 2020-2021 planning year, the third consecutive year that TMI failed to clear the PJM base residual capacity auction and on May 30, 2017, based on these capacity auction results, prolonged periods of low wholesale power prices, and the absence of federal or state policies that place a value on nuclear energy for its ability to produce electricity without air pollution, Generation announced that it would permanently cease generation operations at TMI. On September 20, 2019, Generation permanently ceased generation operations at TMI. On February 2, 2018, Generation announced that it would permanently cease generation operations at the Oyster Creek nuclear plant at the end of its current operating cycle and permanently ceased generation operations on September 17, 2018. As a result of these early nuclear plant retirement decisions, Exelon and Generation recognized incremental non-cash charges to earnings stemming from shortening the expected economic useful lives primarily related to accelerated depreciation of plant assets (including any ARC) and accelerated amortization of nuclear fuel, as well as operating and maintenance expenses. See Note 13 — Nuclear Decommissioning for additional information on changes to the nuclear decommissioning ARO balance. The total impact for the three and nine months ended September 30, 2019 and 2018 are summarized in the table below. Three Months Ended September 30, Nine Months Ended September 30, Income statement expense (pre-tax) 2019 2018 2019 2018 Depreciation and amortization (a) Accelerated depreciation $ 71 $ 152 $ 216 $ 441 Accelerated nuclear fuel amortization 3 18 13 52 Operating and maintenance (b) 39 4 (44 ) 32 Total $ 113 $ 174 $ 185 $ 525 _________ (a) Reflects incremental accelerated depreciation and amortization for TMI for the three and nine months ended September 30, 2019 . Reflects incremental accelerated depreciation for TMI and Oyster Creek for the three and nine months ended September 30, 2018 . The Oyster Creek amounts are from February 2, 2018 through September 17, 2018. The TMI amounts are through September 20, 2019. (b) In 2019, primarily reflects the net impacts associated with the remeasurements of the TMI ARO in the first and third quarters. See Note 13 — Nuclear Decommissioning for additional information on the first quarter 2019 TMI ARO update. In 2018, primarily reflects materials and supplies inventory reserve adjustments, employee related costs and CWIP impairments associated with the early retirement decisions for TMI and Oyster Creek. Excludes the charges in the third quarter of 2018 and second quarter of 2019 to Operating and maintenance expense for the ARO remeasurement due to the sale of Oyster Creek. See Note 3 — Mergers, Acquisitions and Dispositions for additional information. Generation’s Dresden, Byron and Braidwood nuclear plants in Illinois are also showing increased signs of economic distress, which could lead to an early retirement, in a market that does not currently compensate them for their unique contribution to grid resiliency and their ability to produce large amounts of energy without carbon and air pollution. The May 2018 PJM capacity auction for the 2021-2022 planning year resulted in the largest volume of nuclear capacity ever not selected in the auction, including all of Dresden, and portions of Byron and Braidwood. Exelon continues to work with stakeholders on state policy solutions, while also advocating for broader market reforms at the regional and federal level. Other Generation On March 29, 2018, Generation notified grid operator ISO-NE of its plans to early retire its Mystic Generating Station assets absent regulatory reforms on June 1, 2022, at the end of the then-current capacity commitment for Mystic Units 7 and 8. Mystic Unit 9 was then committed through May 2021. On May 16, 2018, Generation made a filing with FERC to establish cost-of-service compensation and terms and conditions of service for Mystic Units 8 and 9 for the period between June 1, 2022 - May 31, 2024. On December 20, 2018, FERC issued an order accepting the cost of service agreement reflecting a number of adjustments to the annual fixed revenue requirement and allowing for recovery of a substantial portion of the costs associated with the Everett Marine Terminal. Those adjustments were reflected in a compliance filing filed March 1, 2019. In the December 20, 2018 order, FERC also directed a paper hearing on ROE using a new methodology. Initial briefs in the ROE proceeding were filed on April 19, 2019 and reply briefs were filed on July 18, 2019. On January 4, 2019, Generation notified ISO-NE that it will participate in the Forward Capacity Market auction for the 2022 - 2023 capacity commitment period. In addition, on January 22, 2019, Exelon and several other parties filed requests for rehearing of certain findings of the December 20, 2018 order, which does not alter Generation's commitment to participate in the Forward Capacity Auction for the 2022-2023 capacity commitment period. On June 10, 2019, ISO-NE announced that it has determined that Mystic 8 and 9 are needed for fuel security for the 2023-2024 capacity commitment period. On March 25, 2019, ISO-NE filed the Inventoried Energy Program, which is intended to provide an interim fuel security program pending conclusion of the stakeholder process to develop a long-term, market-based solution to address fuel security. Exelon filed comments on the Inventoried Energy Program proposal on April 15, 2019. On May 8, 2019, FERC issued a deficiency letter to ISO-NE seeking additional information on the Inventoried Energy Program proposal, and ISO-NE filed a response on June 6, 2019. On August 5, 2019, FERC allowed the Inventoried Energy Program to take effect by operation of law. Several parties have filed requests for rehearing. FERC ordered ISO-NE to file long-term, market-based fuel security rules by October 15, 2019. On August 30, 2019, FERC granted an extension of time to file the long-term, market-based fuel security rules to April 15, 2020. The following table provides the balance sheet amounts as of September 30, 2019 for Exelon's and Generation’s significant assets and liabilities associated with the Mystic Units 8 and 9 and Everett Marine Terminal assets that would potentially be impacted by the failure to adopt long-term solutions for reliability and fuel security. September 30, 2019 Asset Balances Materials and supplies inventory $ 31 Fuel inventory 5 Completed plant, net 889 Construction work in progress 7 Liability Balances Asset retirement obligation (2 )

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities (All Registrants)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities (All Registrants)	Fair Value of Financial Assets and Liabilities (All Registrants) E xelon measures and classifies fair value measurements in accordance with the hierarchy as defined by GAAP. 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. Exelon’s valuation techniques used to measure the fair value of the assets and liabilities shown in the tables below are in accordance with the policies discussed in Note 11 — Fair Value of Financial Assets and Liabilities of the Exelon 2018 Form 10-K, unless otherwise noted below. Fair Value of Financial Liabilities Recorded at Amortized Cost The following tables present the carrying amounts and fair values of the Registrants’ short-term liabilities, long-term debt, SNF obligation and trust preferred securities (long-term debt to financing trusts or junior subordinated debentures) as of September 30, 2019 and December 31, 2018 . The Registrants have no financial liabilities classified as Level 1. The carrying amounts of the Registrants’ short-term liabilities as presented on their Consolidated Balance Sheets are representative of their fair value (Level 2) because of the short-term nature of these instruments. September 30, 2019 December 31, 2018 Carrying Amount Fair Value Carrying Amount Fair Value Level 2 Level 3 Total Level 2 Level 3 Total Long-Term Debt, including amounts due within one year (a) Exelon $ 36,304 $ 38,056 $ 2,541 $ 40,597 $ 35,424 $ 33,711 $ 2,158 $ 35,869 Generation 8,613 7,962 1,398 9,360 8,793 7,467 1,443 8,910 ComEd 8,196 9,622 — 9,622 8,101 8,390 — 8,390 PECO 3,404 3,891 50 3,941 3,084 3,157 50 3,207 BGE 3,270 3,678 — 3,678 2,876 2,950 — 2,950 PHI 6,494 5,993 1,093 7,086 6,259 5,436 665 6,101 Pepco 2,860 3,249 395 3,644 2,719 2,901 196 3,097 DPL 1,495 1,437 232 1,669 1,494 1,303 193 1,496 ACE 1,324 1,034 466 1,500 1,188 987 275 1,262 Long-Term Debt to Financing Trusts (a) Exelon $ 390 $ — $ 426 $ 426 $ 390 $ — $ 400 $ 400 ComEd 205 — 223 223 205 — 209 209 PECO 184 — 203 203 184 — 191 191 SNF Obligation Exelon $ 1,193 $ 1,017 $ — $ 1,017 $ 1,171 $ 949 $ — $ 949 Generation 1,193 1,017 — 1,017 1,171 949 — 949 ____ (a) Includes unamortized debt issuance costs which are not fair valued. Recurring Fair Value Measurements The following tables present assets and liabilities measured and recorded at fair value in the Registrants' Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of September 30, 2019 and December 31, 2018 : Exelon and Generation Exelon Generation As of September 30, 2019 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 1,719 $ — $ — $ — $ 1,719 $ 896 $ — $ — $ — $ 896 NDT fund investments Cash equivalents (b) 315 78 — — 393 315 78 — — 393 Equities 3,121 1,727 — 1,314 6,162 3,121 1,727 — 1,314 6,162 Fixed income Corporate debt — 1,473 259 — 1,732 — 1,473 259 — 1,732 U.S. Treasury and agencies 1,777 152 — — 1,929 1,777 152 — — 1,929 Foreign governments — 56 — — 56 — 56 — — 56 State and municipal debt — 85 — — 85 — 85 — — 85 Other (c) — 23 — 979 1,002 — 23 — 979 1,002 Exelon Generation As of September 30, 2019 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Fixed income subtotal 1,777 1,789 259 979 4,804 1,777 1,789 259 979 4,804 Middle market lending — — 255 445 700 — — 255 445 700 Private equity — — — 398 398 — — — 398 398 Real estate — — — 581 581 — — — 581 581 NDT fund investments subtotal (d) 5,213 3,594 514 3,717 13,038 5,213 3,594 514 3,717 13,038 Rabbi trust investments Cash equivalents 49 — — — 49 4 — — — 4 Mutual funds 77 — — — 77 24 — — — 24 Fixed income — 13 — — 13 — — — — — Life insurance contracts — 76 40 — 116 — 24 — — 24 Rabbi trust investments subtotal 126 89 40 — 255 28 24 — — 52 Commodity derivative assets Economic hedges 533 1,488 1,817 — 3,838 533 1,488 1,817 — 3,838 Proprietary trading — 54 156 — 210 — 54 156 — 210 Effect of netting and allocation of collateral (e)(f) (677 ) (1,261 ) (1,025 ) — (2,963 ) (677 ) (1,261 ) (1,025 ) — (2,963 ) Commodity derivative assets subtotal (144 ) 281 948 — 1,085 (144 ) 281 948 — 1,085 Total assets 6,914 3,964 1,502 3,717 16,097 5,993 3,899 1,462 3,717 15,071 Liabilities Commodity derivative liabilities Economic hedges (773 ) (1,695 ) (1,686 ) — (4,154 ) (773 ) (1,695 ) (1,406 ) — (3,874 ) Proprietary trading — (59 ) (89 ) — (148 ) — (59 ) (89 ) — (148 ) Effect of netting and allocation of collateral (e)(f) 770 1,585 1,329 — 3,684 770 1,585 1,329 — 3,684 Commodity derivative liabilities subtotal (3 ) (169 ) (446 ) — (618 ) (3 ) (169 ) (166 ) — (338 ) Deferred compensation obligation — (140 ) — — (140 ) — (37 ) — — (37 ) Total liabilities (3 ) (309 ) (446 ) — (758 ) (3 ) (206 ) (166 ) — (375 ) Total net assets $ 6,911 $ 3,655 $ 1,056 $ 3,717 $ 15,339 $ 5,990 $ 3,693 $ 1,296 $ 3,717 $ 14,696 Exelon Generation As of December 31, 2018 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 1,243 $ — $ — $ — $ 1,243 $ 581 $ — $ — $ — $ 581 NDT fund investments Cash equivalents (b) 252 86 — — 338 252 86 — — 338 Equities 2,918 1,591 — 1,381 5,890 2,918 1,591 — 1,381 5,890 Fixed income Corporate debt — 1,593 230 — 1,823 — 1,593 230 — 1,823 U.S. Treasury and agencies 2,081 99 — — 2,180 2,081 99 — — 2,180 Foreign governments — 50 — — 50 — 50 — — 50 State and municipal debt — 149 — — 149 — 149 — — 149 Other (c) — 30 — 846 876 — 30 — 846 876 Fixed income subtotal 2,081 1,921 230 846 5,078 2,081 1,921 230 846 5,078 Middle market lending — — 313 367 680 — — 313 367 680 Private equity — — — 329 329 — — — 329 329 Real estate — — — 510 510 — — — 510 510 NDT fund investments subtotal (d) 5,251 3,598 543 3,433 12,825 5,251 3,598 543 3,433 12,825 Rabbi trust investments Cash equivalents 48 — — — 48 5 — — — 5 Mutual funds 72 — — — 72 24 — — — 24 Fixed income — 15 — — 15 — — — — — Life insurance contracts — 70 38 — 108 — 22 — — 22 Rabbi trust investments subtotal 120 85 38 — 243 29 22 — — 51 Commodity derivative assets Economic hedges 541 2,760 1,470 — 4,771 541 2,760 1,470 — 4,771 Proprietary trading — 69 77 — 146 — 69 77 — 146 Effect of netting and allocation of collateral (e)(f) (582 ) (2,357 ) (732 ) — (3,671 ) (582 ) (2,357 ) (732 ) — (3,671 ) Commodity derivative assets subtotal (41 ) 472 815 — 1,246 (41 ) 472 815 — 1,246 Total assets 6,573 4,155 1,396 3,433 15,557 5,820 4,092 1,358 3,433 14,703 Exelon Generation As of December 31, 2018 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Liabilities Commodity derivative liabilities Economic hedges (642 ) (2,963 ) (1,276 ) — (4,881 ) (642 ) (2,963 ) (1,027 ) — (4,632 ) Proprietary trading — (73 ) (21 ) — (94 ) — (73 ) (21 ) — (94 ) Effect of netting and allocation of collateral (e)(f) 639 2,581 808 — 4,028 639 2,581 808 — 4,028 Commodity derivative liabilities subtotal (3 ) (455 ) (489 ) — (947 ) (3 ) (455 ) (240 ) — (698 ) Deferred compensation obligation — (137 ) — — (137 ) — (35 ) — — (35 ) Total liabilities (3 ) (592 ) (489 ) — (1,084 ) (3 ) (490 ) (240 ) — (733 ) Total net assets $ 6,570 $ 3,563 $ 907 $ 3,433 $ 14,473 $ 5,817 $ 3,602 $ 1,118 $ 3,433 $ 13,970 _________ (a) Exelon excludes cash of $347 million and $458 million at September 30, 2019 and December 31, 2018 , respectively, and restricted cash of $112 million and $80 million at September 30, 2019 and December 31, 2018 , respectively, and includes long-term restricted cash of $186 million and $185 million at September 30, 2019 and December 31, 2018 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Generation excludes cash of $183 million and $283 million at September 30, 2019 and December 31, 2018 , respectively, and restricted cash of $66 million and $39 million at September 30, 2019 and December 31, 2018 , respectively. (b) Includes $85 million and $50 million of cash received from outstanding repurchase agreements at September 30, 2019 and December 31, 2018 , respectively, and is offset by an obligation to repay upon settlement of the agreement as discussed in (d) below. (c) Includes a derivative liability of $2 million and a derivative asset of $44 million , which have total notional amounts of $864 million and $1,432 million at September 30, 2019 and December 31, 2018 , respectively. The notional principal amounts for these instruments provide one measure of the transaction volume outstanding as of the fiscal years ended and do not represent the amount of Exelon and Generation's exposure to credit or market loss. (d) Excludes net liabilities of $176 million and $130 million at September 30, 2019 and December 31, 2018 , respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, repurchase agreement obligations, and payables related to pending securities purchases. The repurchase agreements are generally short-term in nature with durations generally of 30 days or less. (e) Collateral posted/(received) from counterparties totaled $93 million , $324 million and $304 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of September 30, 2019 . Collateral posted/(received) from counterparties, net of collateral paid to counterparties, totaled $57 million , $224 million and $76 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2018 . (f) Of the collateral posted/(received), $306 million and $(94) million represents variation margin on the exchanges as of September 30, 2019 and December 31, 2018 , respectively. As of September 30, 2019 , Exelon and Generation have outstanding commitments to invest in fixed income, middle market lending, private equity and real estate investments of approximately $93 million , $241 million , $383 million , and $388 million , respectively. These commitments will be funded by Generation’s existing NDT funds. Exelon and Generation hold investments without readily determinable fair values with carrying amounts of $75 million as of September 30, 2019 . Changes were immaterial in fair value, cumulative adjustments and impairments for the three and nine months ended September 30, 2019 . Valuation Techniques Used to Determine Net Asset Value Certain NDT Fund Investments are not classified within the fair value hierarchy and are included under the heading “Not subject to leveling” in the table above. These investments are measured at fair value using NAV per share as a practical expedient and include commingled funds, mutual funds which are not publicly quoted, managed middle market funds, private equity and real estate funds. For commingled funds and mutual funds, which are not publicly quoted, the fair value is primarily derived from the quoted prices in active markets on the underlying securities and can typically be redeemed monthly with 30 or less days of notice and without further restrictions. For managed middle market funds, the fair value is determined using a combination of valuation models including cost models, market models, and income models and typically cannot be redeemed until maturity of the term loan. Private equity and real estate investments include those in limited partnerships that invest in operating companies and real estate holding companies that are not publicly traded on a stock exchange, such as, leveraged buyouts, growth capital, venture capital, distressed investments, investments in natural resources, and direct investments in pools of real estate properties. These investments typically cannot be redeemed and are generally liquidated over a period of 8 to 10 years from the initial investment date, which is based on Exelon’s understanding of the investment funds. Private equity and real estate 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, market based comparable data, and independent appraisals from sources with professional qualifications. These valuation inputs are unobservable. ComEd, PECO and BGE ComEd PECO BGE As of September 30, 2019 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 264 $ — $ — $ 264 $ 207 $ — $ — $ 207 $ 122 $ — $ — $ 122 Rabbi trust investments Mutual funds — — — — 8 — — 8 7 — — 7 Life insurance contracts — — — — — 11 — 11 — — — — Rabbi trust investments subtotal — — — — 8 11 — 19 7 — — 7 Total assets 264 — — 264 215 11 — 226 129 — — 129 Liabilities Deferred compensation obligation — (7 ) — (7 ) — (8 ) — (8 ) — (5 ) — (5 ) Mark-to-market derivative liabilities (b) — — (280 ) (280 ) — — — — — — — — Total liabilities — (7 ) (280 ) (287 ) — (8 ) — (8 ) — (5 ) — (5 ) Total net assets (liabilities) $ 264 $ (7 ) $ (280 ) $ (23 ) $ 215 $ 3 $ — $ 218 $ 129 $ (5 ) $ — $ 124 ComEd PECO BGE As of December 31, 2018 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 209 $ — $ — $ 209 $ 111 $ — $ — $ 111 $ 4 $ — $ — $ 4 Rabbi trust investments Mutual funds — — — — 7 — — 7 6 — — 6 Life insurance contracts — — — — — 10 — 10 — — — — Rabbi trust investments subtotal — — — — 7 10 — 17 6 — — 6 Total assets 209 — — 209 118 10 — 128 10 — — 10 Liabilities Deferred compensation obligation — (6 ) — (6 ) — (10 ) — (10 ) — (5 ) — (5 ) Mark-to-market derivative liabilities (b) — — (249 ) (249 ) — — — — — — — — Total liabilities — (6 ) (249 ) (255 ) — (10 ) — (10 ) — (5 ) — (5 ) Total net assets (liabilities) $ 209 $ (6 ) $ (249 ) $ (46 ) $ 118 $ — $ — $ 118 $ 10 $ (5 ) $ — $ 5 _________ (a) ComEd excludes cash of $76 million and $93 million at September 30, 2019 and December 31, 2018 , respectively, and restricted cash of $31 million and $28 million at September 30, 2019 and December 31, 2018 , respectively, and includes long-term restricted cash of $171 million and $166 million at September 30, 2019 and December 31, 2018 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. PECO excludes cash of $23 million and $24 million at September 30, 2019 and December 31, 2018 , respectively. BGE excludes cash of $8 million and $7 million at September 30, 2019 and December 31, 2018 , respectively, and restricted cash of $1 million and $2 million at September 30, 2019 and December 31, 2018 , respectively. (b) The Level 3 balance consists of the current and noncurrent liability of $27 million and $253 million , respectively, at September 30, 2019 , and $26 million and $223 million , respectively, at December 31, 2018 , related to floating-to-fixed energy swap contracts with unaffiliated suppliers. PHI, Pepco, DPL and ACE As of September 30, 2019 As of December 31, 2018 PHI Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 107 $ — $ — $ 107 $ 147 $ — $ — $ 147 Rabbi trust investments Cash equivalents 43 — — 43 42 — — 42 Mutual funds 13 — — 13 13 — — 13 Fixed income — 13 — 13 — 15 — 15 Life insurance contracts — 24 40 64 — 22 38 60 Rabbi trust investments subtotal 56 37 40 133 55 37 38 130 Total assets 163 37 40 240 202 37 38 277 Liabilities Deferred compensation obligation — (19 ) — (19 ) — (21 ) — (21 ) Total liabilities — (19 ) — (19 ) — (21 ) — (21 ) Total net assets $ 163 $ 18 $ 40 $ 221 $ 202 $ 16 $ 38 $ 256 Pepco DPL ACE As of September 30, 2019 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 34 $ — $ — $ 34 $ — $ — $ — $ — $ 18 $ — $ — $ 18 Rabbi trust investments Cash equivalents 43 — — 43 — — — — — — — — Fixed income — 3 — 3 — — — — — — — — Life insurance contracts — 24 40 64 — — — — — — — — Rabbi trust investments subtotal 43 27 40 110 — — — — — — — — Total assets 77 27 40 144 — — — — 18 — — 18 Liabilities Deferred compensation obligation — (2 ) — (2 ) — — — — — — — — Total liabilities — (2 ) — (2 ) — — — — — — — — Total net assets $ 77 $ 25 $ 40 $ 142 $ — $ — $ — $ — $ 18 $ — $ — $ 18 Pepco DPL ACE As of December 31, 2018 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 38 $ — $ — $ 38 $ 16 $ — $ — $ 16 $ 23 $ — $ — $ 23 Rabbi trust investments Cash equivalents 41 — — 41 — — — — — — — — Fixed income — 5 — 5 — — — — — — — — Life insurance contracts — 22 37 59 — — — — — — — — Rabbi trust investments subtotal 41 27 37 105 — — — — — — — — Total assets 79 27 37 143 16 — — 16 23 — — 23 Liabilities Deferred compensation obligation — (3 ) — (3 ) — (1 ) — (1 ) — — — — Total liabilities — (3 ) — (3 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 79 $ 24 $ 37 $ 140 $ 16 $ (1 ) $ — $ 15 $ 23 $ — $ — $ 23 _________ (a) PHI excludes cash of $45 million and $39 million at September 30, 2019 and December 31, 2018 , respectively, and includes long-term restricted cash of $15 million and $19 million at September 30, 2019 and December 31, 2018 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Pepco excludes cash of $18 million and $15 million at September 30, 2019 and December 31, 2018 , respectively. DPL excludes cash of $11 million and $8 million at September 30, 2019 and December 31, 2018 , respectively. ACE excludes cash of $13 million and $7 million at September 30, 2019 and December 31, 2018 , respectively, and includes long-term restricted cash of $15 million and $19 million at September 30, 2019 and December 31, 2018 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. The following tables present the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2019 and 2018 : Exelon Generation ComEd PHI and Pepco Three Months Ended September 30, 2019 Total NDT Fund Investments Mark-to-Market Derivatives Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Balance as of June 30, 2019 $ 1,179 $ 539 $ 873 $ 1,412 $ (273 ) $ 40 $ — Total realized / unrealized gains (losses) Included in net income (171 ) 2 (173 ) (a) (171 ) — — — Included in noncurrent payables to affiliates — 11 — 11 — — (11 ) Included in regulatory assets/liabilities 4 — — — (7 ) (b) — 11 Change in collateral 41 — 41 41 — — — Purchases, sales, issuances and settlements Purchases 53 1 52 53 — — — Sales (22 ) (21 ) (1 ) (22 ) — — — Settlements (18 ) (18 ) — (18 ) — — — Transfers into Level 3 1 — 1 (c) 1 — — — Transfers out of Level 3 (11 ) — (11 ) (c) (11 ) — — — Balance at September 30, 2019 $ 1,056 $ 514 $ 782 $ 1,296 $ (280 ) $ 40 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2019 $ (18 ) $ 2 $ (20 ) $ (18 ) $ — $ — $ — Exelon Generation ComEd PHI and Pepco Nine Months Ended September 30, 2019 Total NDT Fund Investments Mark-to-Market Derivatives Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Balance as of December 31, 2018 $ 907 $ 543 $ 575 $ 1,118 $ (249 ) $ 38 $ — Total realized / unrealized gains (losses) Included in net income (125 ) 5 (132 ) (a) (127 ) — 2 — Included in noncurrent payables to affiliates — 32 — 32 — — (32 ) Included in regulatory assets 1 — — — (31 ) (b) — 32 Change in collateral 227 — 227 227 — — — Purchases, sales, issuances and settlements Purchases 163 43 120 163 — — — Sales (23 ) (21 ) (2 ) (23 ) — — — Settlements (88 ) (88 ) — (88 ) — — — Transfers into Level 3 5 — 5 (c) 5 — — — Transfers out of Level 3 (11 ) — (11 ) (c) (11 ) — — — Balance as of September 30, 2019 $ 1,056 $ 514 $ 782 $ 1,296 $ (280 ) $ 40 $ — The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2019 $ 173 $ 5 $ 166 $ 171 $ — $ 2 $ — __________ (a) Includes a reduction for the reclassification of $153 million and $298 million of realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2019 , respectively. (b) Includes $7 million of decreases in fair value and an increase for 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 September 30, 2019 . Includes $31 million of decreases in fair value and an increase for realized losses due to settlements of $17 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the nine months ended September 30, 2019 . (c) Transfers into and out of Level 3 generally occur when the contract tenor becomes less and more observable respectively, primarily due to changes in market liquidity or assumptions for certain commodity contracts. Exelon Generation ComEd PHI and Pepco Three Months Ended September 30, 2018 Total NDT Fund Investments Mark-to-Market Derivatives Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Balance as of June 30, 2018 $ 1,106 $ 585 $ 737 $ 1,322 $ (252 ) $ 36 $ — Total realized / unrealized gains (losses) Included in net income (259 ) (1 ) (259 ) (a) (260 ) — 1 — Included in noncurrent payables to affiliates — (4 ) — (4 ) — — 4 Included in regulatory assets (11 ) — — — (7 ) (b) — (4 ) Change in collateral (44 ) — (44 ) (44 ) — — — Purchases, sales, issuances and settlements Purchases 96 15 81 96 — — — Settlements (29 ) (29 ) — (29 ) — — — Transfers into Level 3 3 — 3 (c) 3 — — — Transfers out of Level 3 (6 ) — (6 ) (c) (6 ) — — — Balance as of September 30, 2018 $ 856 $ 566 $ 512 $ 1,078 $ (259 ) $ 37 $ — The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2018 $ (105 ) $ (1 ) $ (104 ) $ (105 ) $ — $ — $ — Exelon Generation ComEd PHI and Pepco Nine Months Ended September 30, 2018 Total NDT Fund Investments Mark-to-Market Derivatives Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Balance as of December 31, 2017 $ 966 $ 648 $ 552 $ 1,200 $ (256 ) $ 22 $ — Total realized / unrealized gains (losses) Included in net income (186 ) (1 ) (188 ) (a) (189 ) — 3 — Included in regulatory assets (3 ) — — — (3 ) (b) — — Change in collateral 14 — 14 14 — — — Purchases, sales, issuances and settlements Purchases 215 34 181 215 — — — Sales (3 ) — (3 ) (3 ) — — — Settlements (103 ) (115 ) — (115 ) — 12 — Transfers into Level 3 (21 ) — (21 ) (c) (21 ) — — — Transfers out of Level 3 (23 ) — (23 ) (c) (23 ) — — — Balance as of September 30, 2018 $ 856 $ 566 $ 512 $ 1,078 $ (259 ) $ 37 $ — The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2018 $ 154 $ (5 ) $ 159 $ 154 $ — $ — $ — __________ (a) Includes a reduction for the reclassification of $155 million and $347 million of realized losses due to the settlement of derivative contracts for the three and nine months ended September 30, 2018 , respectively. (b) Includes $4 million of increases in fair value and an increase for realized losses due to settlements of $3 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2018 . Includes $9 million of decreases in fair value and an increase for realized losses due to settlements of $12 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the nine months ended September 30, 2018 . (c) Transfers into and out of Level 3 generally occur when the contract tenor becomes less and more observable respectively, primarily due to changes in market liquidity or assumptions for certain commodity contracts. The following tables present the income statement classification of the total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2019 and 2018 : Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total realized (losses) gains for the three months ended September 30, 2019 $ (25 ) $ (148 ) $ — $ 2 $ (25 ) $ (148 ) $ 2 $ — Total realized gains (losses) for the nine months ended September 30, 2019 122 (254 ) — 5 122 (254 ) 5 — Total unrealized gains (losses) for the three months ended September 30, 2019 99 (119 ) — 2 99 (119 ) 2 — Total unrealized gains (losses) for the nine months ended September 30, 2019 368 (202 ) 2 5 368 (202 ) 5 2 Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Revenues Purchased Power and Fuel Other, net Operating and Maintenance Total realized (losses) gains for the three months ended September 30, 2018 $ (176 ) $ (83 ) $ 1 $ (1 ) $ (176 ) $ (83 ) $ (1 ) $ 1 Total realized (losses) gains for the nine months ended September 30, 2018 (32 ) (156 ) 3 (1 ) (32 ) (156 ) (1 ) 3 Total unrealized (losses) for the three months ended September 30, 2018 (64 ) (40 ) — (1 ) (64 ) (40 ) (1 ) — Total unrealized gains (losses) for the nine months ended September 30, 2018 174 (15 ) — (5 ) 174 (15 ) (5 ) — The table below discloses the significant inputs to the forward curve used to value these positions. Type of trade Fair Value at September 30, 2019 Fair Value at December 31, 2018 Valuation Technique Unobservable Input 2019 Range 2018 Range Mark-to-market derivatives — Economic Hedges (Exelon and Generation) (a)(b) $ 411 $ 443 Discounted Forward power $11 - $167 $12 - $174 Forward gas $1.36 - $10.82 $0.78 - $12.38 Option Volatility 9% - 200% 10% - 277% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(b) $ 67 $ 56 Discounted Forward power $17 - $167 $14 - $174 Mark-to-market derivatives (Exelon and ComEd) $ (280 ) $ (249 ) Discounted Forward heat (c) 9x - 10x 10x - 11x Marketability 4% - 7% 4% - 8% Renewable 87% - 119% 86% - 120% _________ (a) The valuation techniques, unobservable inputs and ranges are the same for the asset and liability positions. (b) The fair values do not include cash collateral posted on level three positions of $304 million and $76 million as of September 30, 2019 and December 31, 2018 , respectively. (c) Quoted forward natural gas rates are utilized to project the forward power curve for the delivery of energy at specified future dates. The natural gas curve is extrapolated beyond its observable period to the end of the contract’s delivery. The inputs listed above, which are as of the balance sheet date, would have a direct impact on the fair values of the above instruments if they were adjusted. The significant unobservable inputs used in the fair value measurement of Generation’s commodity derivatives are forward commodity prices and for options is price volatility. Increases (decreases) in the forward commodity price in isolation would result in significantly higher (lower) fair values for long positions (contracts that give Generation the obligation or option to purchase a commodity), with offsetting impacts to short positions (contracts that give Generation the obligation or right to sell a commodity). Increases (decreases) in volatility would increase (decrease) the value for the holder of the option (writer of the option). Generally, a change in the estimate of forward commodity prices is unrelated to a change in the estimate of volatility of prices. An increase to the reserves listed above would decrease the fair value of the positions. An increase to the heat rate or renewable factors would increase the fair value accordingly. Generally, interrelationships exist between market prices of natural gas and power. As such, an increase in natural gas pricing would potentially have a similar impact on forward power markets.

Derivative Financial Instrument

Derivative Financial Instruments (All Registrants)	9 Months Ended
	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments (All Registrants)	Derivative Financial Instruments (All Registrants) The Registrants use derivative instruments to manage commodity price risk, interest rate risk and foreign exchange risk related to ongoing business operations. Authoritative 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 immediately. 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 NPNS, cash flow hedges and fair value hedges. All derivative economic hedges related to commodities, referred to as economic hedges, are recorded at fair value through earnings at Generation and offset by a corresponding regulatory asset or liability at ComEd. For all NPNS derivative instruments, accounts receivable or accounts payable are recorded when derivative settles and revenue or expense is recognized in earnings as the underlying physical commodity is sold or consumed. Authoritative guidance about offsetting assets and liabilities requires the fair value of derivative instruments to be shown in the Combined Notes to 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 Sheets. 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. In the tables below that present fair value balances, 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 margin on exchange positions, is aggregated in the collateral and netting columns. Generation’s and ComEd’s use of cash collateral is generally unrestricted unless Generation or ComEd are downgraded below investment grade. Cash collateral held by PECO, BGE, Pepco, DPL and ACE must be deposited in an unaffiliated major U.S. commercial bank or foreign bank with a U.S. branch office that meet certain qualifications. Commodity Price Risk (All Registrants) 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 commodity products. The Registrants believe these instruments, which are either determined to be non-derivative or classified as economic hedges, mitigate exposure to fluctuations in commodity prices. Generation. 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. 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 power purchases, natural gas transportation and pipeline capacity agreements and other energy-related products marketed and purchased. To manage these risks, Generation may enter into fixed-price derivative or non-derivative contracts to hedge the variability in future cash flows from expected sales of power and gas and purchases of power and fuel. The objectives for executing such hedges include fixing the price for a portion of anticipated future electricity sales at a level that provides an acceptable return. 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. 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 and are subject to limits established by Exelon’s RMC. Utility Registrants . The Utility Registrants procure electric and natural gas supply through a competitive procurement process approved by each of the respective state utility commissions. The Utility Registrants’ hedging programs are intended to reduce exposure to energy and natural gas price volatility and have no direct earnings impact as the costs are fully recovered from customers through regulatory-approved recovery mechanisms. The following table provides a summary of the Utility Registrants’ primary derivative hedging instruments, listed by commodity and accounting treatment. Registrant Commodity Accounting Treatment Hedging instrument ComEd Electricity NPNS Fixed price contracts based on all requirements in the IPA procurement plans. Electricity Changes in fair value of economic hedge recorded to an offsetting regulatory asset or liability (a) 20-year floating-to-fixed energy swap contracts beginning June 2012 based on the renewable energy resource procurement requirements in the Illinois Settlement Legislation of approximately 1.3 million MWhs per year. PECO (b) Gas NPNS Fixed price contracts to cover about 20% of planned natural gas purchases in support of projected firm sales. BGE Electricity NPNS Fixed price contracts for all SOS requirements through full requirements contracts. Gas NPNS Fixed price contracts for between 10-20% of forecasted system supply requirements for flowing (i.e., non-storage) gas for the November through March period. Pepco Electricity NPNS Fixed price contracts for all SOS requirements through full requirements contracts. DPL Electricity NPNS Fixed price contracts for all SOS requirements through full requirements contracts. Gas NPNS Fixed price contracts through full requirements contracts. Changes in fair value of economic hedge recorded to an offsetting regulatory asset or liability (c) Exchange traded future contracts for 50% of estimated monthly purchase requirements each month, including purchases for storage injections. ACE Electricity NPNS Fixed price contracts for all BGS requirements through full requirements contracts. __________ (a) See Note 4 - Regulatory Matters for additional information. (b) As part of its hedging program, PECO enters into electric supply procurement contracts that do not meet the definition of a derivative instrument. (c) The fair value of the DPL economic hedge is not material as of September 30, 2019 and December 31, 2018 and is not presented in the fair value tables below. The following table provides a summary of the derivative fair value balances recorded by Exelon, Generation and ComEd as of September 30, 2019 and December 31, 2018 : September 30, 2019 Exelon Generation ComEd Derivatives Total Economic Hedges Proprietary Trading Collateral (a)(b) Netting (a) Subtotal Economic Hedges Mark-to-market derivative assets (current assets) $ 602 $ 2,452 $ 143 $ 212 $ (2,205 ) $ 602 $ — Mark-to-market derivative assets (noncurrent assets) 483 1,386 67 104 (1,074 ) 483 — Total mark-to-market derivative assets 1,085 3,838 210 316 (3,279 ) 1,085 — Mark-to-market derivative liabilities (current liabilities) (224 ) (2,550 ) (101 ) 249 2,205 (197 ) (27 ) Mark-to-market derivative liabilities (noncurrent liabilities) (394 ) (1,324 ) (47 ) 156 1,074 (141 ) (253 ) Total mark-to-market derivative liabilities (618 ) (3,874 ) (148 ) 405 3,279 (338 ) (280 ) Total mark-to-market derivative net assets (liabilities) $ 467 $ (36 ) $ 62 $ 721 $ — $ 747 $ (280 ) December 31, 2018 Exelon Generation ComEd Description Total Economic Proprietary Collateral Netting (a) Subtotal Economic Mark-to-market derivative assets $ 801 $ 3,505 $ 105 $ 121 $ (2,930 ) $ 801 $ — Mark-to-market derivative assets 445 1,266 41 51 (913 ) 445 — Total mark-to-market derivative assets 1,246 4,771 146 172 (3,843 ) 1,246 — Mark-to-market derivative liabilities (473 ) (3,429 ) (74 ) 125 2,931 (447 ) (26 ) Mark-to-market derivative liabilities (474 ) (1,203 ) (20 ) 60 912 (251 ) (223 ) Total mark-to-market derivative liabilities (947 ) (4,632 ) (94 ) 185 3,843 (698 ) (249 ) Total mark-to-market derivative net assets (liabilities) $ 299 $ 139 $ 52 $ 357 $ — $ 548 $ (249 ) _________ (a) Exelon and Generation net all available amounts allowed under the derivative authoritative guidance in 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 amounts are immaterial and not reflected in the table above. (b) Of the collateral posted/(received), $306 million and $(94) million represents variation margin on the exchanges at September 30, 2019 and December 31, 2018 respectively. Economic Hedges (Commodity Price Risk) Generation. For the three and nine months ended September 30, 2019 and 2018 , Exelon and Generation recognized the following net pre-tax commodity mark-to-market gains (losses) which are also located in the Net fair value changes related to derivatives line in the Consolidated Statements of Cash Flows. Three Months Ended Nine Months Ended 2019 2018 2019 2018 Income Statement Location Gain (Loss) Gain (Loss) Operating revenues $ 76 $ 8 $ 65 $ (99 ) Purchased power and fuel (45 ) 66 (127 ) (4 ) Total Exelon and Generation $ 31 $ 74 $ (62 ) $ (103 ) In general, increases and decreases in forward market prices have a positive and negative impact, respectively, on Generation’s owned and contracted generation positions that have not been hedged. Generation hedges commodity price risk on a ratable basis over three-year periods. As of September 30, 2019 , the percentage of expected generation hedged for the Mid-Atlantic, Midwest, New York and ERCOT reportable segments is 96% - 99% , 84% - 87% and 54% - 57% for 2019 , 2020 and 2021 , respectively. Proprietary Trading (Commodity Price Risk) Generation also executes commodity derivatives for proprietary trading purposes. Proprietary trading includes all contracts executed with the intent of benefiting from shifts or changes in market prices as opposed to those executed with the intent of hedging or managing risk. Gains and losses associated with proprietary trading are reported as Operating revenues in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income and are included in the Net fair value changes related to derivatives line in the Consolidated Statements of Cash Flows. For the three and nine months ended September 30, 2019 and 2018 , net pre-tax commodity mark-to-market gains (losses) for Exelon and Generation were not material. The Utility Registrants do not execute derivatives for proprietary trading purposes. Interest Rate and Foreign Exchange Risk (Exelon and Generation) Exelon and Generation utilize interest rate swaps, which are treated as economic hedges, to manage their interest rate exposure. On July 1, 2018, Exelon de-designated its fair value hedges related to interest rate risk and Generation de-designated its cash flow hedges related to interest rate risk. The notional amounts were $1,371 million and $1,420 million at September 30, 2019 and December 31, 2018 , respectively, for Exelon and $571 million and $620 million at September 30, 2019 and December 31, 2018 , respectively, for Generation. Generation utilizes foreign currency derivatives to manage foreign exchange rate exposure associated with international commodity purchases in currencies other than U.S. dollars, which are treated as economic hedges. The notional amounts were $257 million and $268 million at September 30, 2019 and December 31, 2018 , respectively. The mark-to-market derivative assets and liabilities as of September 30, 2019 and December 31, 2018 and the mark-to-market gains and losses for the three and nine months ended September 30, 2019 and 2018 were not material for Exelon and Generation. Credit Risk (All Registrants) The Registrants would be exposed to credit-related losses in the event of non-performance by counterparties on executed derivative instruments. The credit exposure of derivative contracts, before collateral, is represented by the fair value of contracts at the reporting date. Generation. For commodity derivatives, Generation enters into enabling agreements that allow for payment netting with its counterparties, which reduces Generation’s exposure to counterparty risk by providing for the offset of amounts payable to the counterparty against amounts receivable from the counterparty. Typically, each enabling agreement is for a specific commodity and so, with respect to each individual counterparty, netting is limited to transactions involving that specific commodity product, except where master netting agreements exist with a counterparty that allow for cross product netting. In addition to payment netting language in the enabling agreement, Generation’s credit department establishes credit limits, margining thresholds and collateral requirements for each counterparty, which are defined in the derivative contracts. Counterparty credit limits are based on an internal credit review process that considers a variety of factors, including the results of a scoring model, leverage, liquidity, profitability, credit ratings by credit rating agencies, and risk management capabilities. To the extent that a counterparty’s margining thresholds are exceeded, the counterparty is required to post collateral with Generation as specified in each enabling agreement. Generation’s credit department monitors current and forward credit exposure to counterparties and their affiliates, both on an individual and an aggregate basis. The following tables provide information on Generation’s credit exposure for all derivative instruments, NPNS and applicable payables and receivables, net of collateral and instruments that are subject to master netting agreements, as of September 30, 2019 . The tables further delineate that exposure by credit rating of the counterparties and provide guidance on the concentration of credit risk to individual counterparties. The figures in the tables below exclude credit risk exposure from individual retail counterparties, nuclear fuel procurement contracts and exposure through RTOs, ISOs, NYMEX, ICE, NASDAQ, NGX and Nodal commodity exchanges. Additionally, the figures in the tables below exclude exposures with affiliates, including net receivables with ComEd, PECO, BGE, Pepco, DPL and ACE of $68 million , $30 million , $32 million , $39 million , $15 million and $8 million as of September 30, 2019 , respectively. Rating as of September 30, 2019 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 $ 693 $ 10 $ 683 — $ — Non-investment grade 74 38 36 No external ratings Internally rated — investment grade 297 1 296 Internally rated — non-investment grade 175 24 151 Total $ 1,239 $ 73 $ 1,166 — $ — Net Credit Exposure by Type of Counterparty As of Financial institutions $ 1 Investor-owned utilities, marketers, power producers 875 Energy cooperatives and municipalities 255 Other 35 Total $ 1,166 _________ (a) As of September 30, 2019 , credit collateral held from counterparties where Generation had credit exposure included $18 million of cash and $55 million of letters of credit. The credit collateral does not include non-liquid collateral. Utility Registrants. The Utility Registrants have contracts to procure electric and natural gas supply that provide suppliers with a certain amount of unsecured credit. If the exposure on the supply contract exceeds the amount of unsecured credit, the suppliers may be required to post collateral. The net credit exposure is mitigated primarily by the ability to recover procurement costs through customer rates. As of September 30, 2019 , the Utility Registrants’ counterparty credit risk with suppliers was immaterial. Credit-Risk-Related Contingent Features (All Registrants) Generation. As part of the normal course of business, Generation routinely enters into physically or financially settled contracts for the purchase and sale of electric capacity, electricity, fuels, emissions allowances and other energy-related products. Certain of Generation’s derivative instruments contain provisions that require Generation to post collateral. Generation also enters into commodity transactions on exchanges where the exchanges act as the counterparty to each trade. Transactions on the exchanges must adhere to comprehensive collateral and margining requirements. This collateral may be posted in the form of cash or credit support with thresholds contingent upon Generation’s credit rating from each of the major credit rating agencies. The collateral and credit support requirements vary by contract and by counterparty. These credit-risk-related contingent features stipulate that if Generation were to be downgraded or lose its investment grade credit rating (based on its senior unsecured debt rating), it would be required to provide additional collateral. This incremental collateral requirement allows for the offsetting of derivative instruments that are assets with the same counterparty, where the contractual right of offset exists under applicable master netting agreements. In the absence of expressly agreed-to provisions that specify the collateral that must be provided, collateral requested will be a function of the facts and circumstances of the situation at the time of the demand. In this case, Generation believes an amount of several months of future payments (i.e., capacity payments) rather than a calculation of fair value is the best estimate for the contingent collateral obligation, which has been factored into the disclosure below. 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 Features September 30, 2019 December 31, 2018 Gross fair value of derivative contracts containing this feature (a) $ (1,249 ) $ (1,723 ) Offsetting fair value of in-the-money contracts under master netting arrangements (b) 947 1,105 Net fair value of derivative contracts containing this feature (c) $ (302 ) $ (618 ) _________ (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. As of September 30, 2019 and December 31, 2018 , Exelon and Generation posted or held the following amounts of cash collateral and letters of credit on derivative contracts with external counterparties, after giving consideration to offsetting derivative and non-derivative positions under master netting agreements. September 30, 2019 December 31, 2018 Cash collateral posted $ 787 $ 418 Letters of credit posted 273 367 Cash collateral held 96 47 Letters of credit held 58 44 Additional collateral required in the event of a credit downgrade below investment grade 1,481 2,104 Generation entered into supply forward contracts with certain utilities, including PECO and BGE, with one-sided collateral postings only from Generation. If market prices fall below the benchmark price levels in these contracts, the utilities are not required to post collateral. However, when market prices rise above the benchmark price levels, counterparty suppliers, including Generation, are required to post collateral once certain unsecured credit limits are exceeded. Utility Registrants The Utility Registrants’ electric supply procurement contracts do not contain provisions that would require them to post collateral. PECO’s, BGE’s, and DPL’s natural gas procurement contracts contain provisions that could require PECO, BGE, and DPL to post collateral in the form of cash or credit support, which vary by contract and counterparty, with thresholds contingent upon PECO’s, BGE, and DPL’s credit rating. As of September 30, 2019 , PECO, BGE, and DPL were not required to post collateral for any of these agreements. If PECO, BGE or DPL lost their investment grade credit ratings as of September 30, 2019 , they could have been required to post incremental collateral to its counterparties of $28 million , $26 million and $11 million

Debt and Credit Agreements (All

Debt and Credit Agreements (All Registrants)	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Debt and Credit Agreements (All Registrants)	Debt and Credit Agreements (All Registrants) Short-Term Borrowings Exelon Corporate, ComEd, BGE, Pepco, DPL and ACE 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 Exelon intercompany money pool. PHI Corporate meets its short-term liquidity requirements primarily through the issuance of short-term notes and the Exelon intercompany money pool. The Registrants may use their respective credit facilities for general corporate purposes, including meeting short-term funding requirements and the issuance of letters of credit. Commercial Paper The following table reflects the Registrants' commercial paper programs as of September 30, 2019 and December 31, 2018 . Generation and PECO had no commercial paper borrowings as of both September 30, 2019 and December 31, 2018 . Outstanding Commercial Average Interest Rate on Commercial Paper Issuer September 30, 2019 December 31, 2018 September 30, 2019 December 31, 2018 Exelon $ 519 $ 89 2.50 % 2.15 % ComEd 387 — 2.51 % 2.14 % BGE — 35 2.49 % 2.18 % PHI 132 54 2.52 % 2.15 % PEPCO 12 40 2.61 % 2.24 % DPL 57 — 2.42 % 2.07 % ACE 63 14 2.57 % 2.21 % See Note 13 — Debt and Credit Agreements of the Exelon 2018 Form 10-K for additional information on the Registrants’ credit facilities. Short-Term Loan Agreements On March 23, 2017, Exelon Corporate entered into a term loan agreement for $500 million , which was renewed on March 22, 2018 with an expiration of March 21, 2019. The loan agreement was renewed on March 20, 2019 and will expire on March 19, 2020. Pursuant to the loan agreement, loans made thereunder bear interest at a variable rate equal to LIBOR plus 0.95% and all indebtedness thereunder is unsecured. The loan agreement is reflected in Exelon's Consolidated Balance Sheet within Short-Term borrowings. Credit Agreements On February 21, 2019, Generation entered into a credit agreement establishing a $100 million bilateral credit facility. The facility will mature in March 2021. This facility will solely be used by Generation to issue letters of credit. Long-Term Debt Issuance of Long-Term Debt During the nine months ended September 30, 2019 , the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Generation Energy Efficiency Project Financing 3.95 % August 31, 2020 $ 4 Funding to install energy conservation measures for the Fort Meade project. Generation Energy Efficiency Project Financing 3.46 % May 1, 2020 $ 39 Funding to install energy conservation measures for the Marine Corps. Logistics Project. ComEd First Mortgage Bonds, Series 126 4.00 % March 1, 2049 $ 400 Repay a portion of ComEd’s outstanding commercial paper obligations and fund other general corporate purposes. PECO First and Refunding Mortgage Bonds 3.00 % September 15, 2049 $ 325 Repay short-term borrowings and for general corporate purposes BGE Senior Notes 3.20 % September 15, 2049 $ 400 Repay commercial paper obligations and for general corporate purposes Pepco First Mortgage Bonds 3.45 % June 13, 2029 $ 150 Repay existing indebtedness and for general corporate purposes Pepco Unsecured Tax-Exempt Bonds 1.70 % September 1, 2022 $ 110 Refinance existing indebtedness ACE First Mortgage Bonds 3.50 % May 21, 2029 $ 100 Repay existing indebtedness and for general corporate purposes ACE First Mortgage Bonds 4.14 % May 21, 2049 $ 50 Repay existing indebtedness and for general corporate purposes Debt Covenants As of September 30, 2019 , the Registrants are in compliance with debt covenants, except for Antelope Valley's nonrecourse debt event of default as discussed below. Nonrecourse Debt Exelon and Generation have issued nonrecourse debt financing. Borrowings under these agreements are secured by the assets and equity of each respective project. The lenders do not have recourse against Exelon or Generation in the event of a default. Antelope Valley Solar Ranch One. In December 2011, the DOE Loan Programs Office issued a guarantee for up to $646 million for a nonrecourse loan from the Federal Financing Bank to support the financing of the construction of the Antelope Valley facility. The project became fully operational in 2014. The loan will mature on January 5, 2037. As of September 30, 2019 , approximately $495 million was outstanding. In 2017, Generation’s interests in Antelope Valley were also contributed to and are pledged as collateral for the EGR IV financing structure referenced below. Antelope Valley sells all of its output to PG&E through a PPA. On January 29, 2019, PG&E filed for protection under Chapter 11 of the U.S. Bankruptcy Code, which created an event of default for Antelope Valley’s nonrecourse debt that provides the lender with a right to accelerate amounts outstanding under the loan such that they would become immediately due and payable. As a result of the ongoing event of default and the absence of a waiver from the lender foregoing their acceleration rights, the debt was reclassified as current in Exelon’s and Generation’s Consolidated Balance Sheets in the first quarter of 2019 and continues to be classified as current as of September 30, 2019 . Further, distributions from Antelope Valley to EGR IV are currently suspended. ExGen Renewables IV. In November 2017, EGR IV, an indirect subsidiary of Exelon and Generation, entered into an $850 million nonrecourse senior secured term loan credit facility agreement. Generation’s interests in EGRP, Antelope Valley, SolGen, and Albany Green Energy were all contributed to and are pledged as collateral for this financing. The loan is scheduled to mature on November 28, 2024. As of September 30, 2019 , $796 million was outstanding. Although Antelope Valley’s debt is in default, it is nonrecourse to EGR IV. However, if in the future Antelope Valley were to file for bankruptcy protection as a result of events culminating from PG&E’s bankruptcy proceedings this would represent an event of default for EGR IV’s debt that would provide the lender with an opportunity to accelerate EGR IV’s debt. See Note 13 — Debt and Credit Agreements of the Exelon 2018 Form 10-K for additional information on nonrecourse debt.

Income Taxes (All Registrants)

Income Taxes (All Registrants)	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes (All Registrants)	Income Taxes (All Registrants) Rate Reconciliation The effective income tax rate from continuing operations varies from the U.S. Federal statutory rate principally due to the following: Three Months Ended September 30, 2019 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 6.4 5.2 8.1 (0.3) 6.3 4.8 1.9 6.6 6.9 Qualified NDT fund income 3.2 7.1 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (4.1) (8.9) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (1.7) — (1.0) (7.5) (1.1) (1.8) (2.6) (0.6) (1.9) Production tax credits and other credits (1.2) (2.7) — — — — — — — Noncontrolling interests (2.2) (4.8) — — — — — — — Excess deferred tax amortization (6.5) — (9.9) (3.6) (8.0) (17.7) (16.3) (13.5) (23.3) Other 0.7 0.5 0.4 (0.5) (0.2) 0.8 1.0 (0.1) 0.7 Effective income tax rate 15.6% 17.4% 18.4% 9.1% 17.9% 6.9% 4.9% 13.2% 3.1% Three Months Ended September 30, 2018 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit (1.2) (9.0) 8.3 (3.6) 7.3 0.2 1.0 6.6 7.3 Qualified NDT fund income 2.4 5.8 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.6) (1.1) (0.2) (0.1) — (0.2) (0.1) (0.3) (0.3) Plant basis differences (2.5) — (0.3) (15.2) (0.8) (2.0) (3.4) (0.7) (1.3) Production tax credits and other credits (1.2) (2.9) (0.1) — — — — — — Noncontrolling interests (1.1) (2.8) — — — — — — — Excess deferred tax amortization (6.8) — (7.8) (4.6) (7.9) (17.7) (21.2) (14.0) (15.4) Tax Cuts and Jobs Act of 2017 1.3 3.5 — — — 0.2 0.1 — — Other 3.2 5.6 0.3 0.9 2.6 0.6 0.3 0.6 0.3 Effective income tax rate 14.5% 20.1% 21.2% (1.6)% 22.2% 2.1% (2.3)% 13.2% 11.6% Nine Months Ended September 30, 2019 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 5.1 4.2 8.2 — 6.4 4.8 2.0 6.7 6.9 Qualified NDT fund income 5.3 11.9 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.9) (4.0) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (1.6) — (0.7) (6.8) (1.1) (1.8) (2.3) (0.6) (2.0) Production tax credits and other credits (1.0) (2.1) — — — — — — — Noncontrolling interests (1.0) (2.3) — — — — — — — Excess deferred tax amortization (6.0) — (9.2) (2.9) (7.9) (18.6) (17.3) (15.0) (23.4) Other 0.8 (0.1) 0.2 (0.2) 0.1 0.5 0.7 0.2 — Effective income tax rate 20.7% 28.6% 19.3% 11.1% 18.4% 5.7% 4.0% 12.1% 2.2% Nine Months Ended September 30, 2018 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 1.7 (2.6) 8.2 (3.6) 6.6 2.7 2.4 6.5 7.3 Qualified NDT fund income 0.9 2.6 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.9) (2.2) (0.2) (0.1) (0.1) (0.2) (0.1) (0.3) (0.3) Plant basis differences (2.7) — (0.1) (15.4) (0.7) (1.9) (2.9) (0.7) (1.3) Production tax credits and other credits (1.8) (5.1) (0.1) — — — — — — Noncontrolling interests (1.1) (3.2) — — — — — — — Excess deferred tax amortization (6.1) — (7.6) (3.4) (8.1) (14.5) (16.5) (11.0) (14.0) Tax Cuts and Jobs Act of 2017 0.2 1.3 (0.2) — — 0.3 — — — Other 0.4 2.0 0.1 — 0.9 0.3 — 0.4 0.9 Effective income tax rate 11.6% 13.8% 21.1% (1.5)% 19.6% 7.7% 3.9% 15.9% 13.6% Accounting for Uncertainty in Income Taxes Exelon, Generation, ComEd, PHI and ACE have the following unrecognized tax benefits as of September 30, 2019 and December 31, 2018 . PECO, BGE, Pepco and DPL do not have unrecognized tax benefits for the periods presented. Exelon Generation ComEd PHI ACE September 30, 2019 $ 448 $ 411 $ — $ 45 $ 14 December 31, 2018 $ 477 $ 408 $ 2 $ 45 $ 14 In 2016, the Tax Court held that Exelon was not entitled to defer a gain on its 1999 like-kind exchange transaction. In addition to the tax and interest related to the gain deferral, the Tax Court also ruled that Exelon was liable for penalties and interest on the penalties. Exelon had fully paid the amounts assessed resulting from the Tax Court decision in 2017. In September 2017, Exelon appealed the Tax Court decision to the U.S. Court of Appeals for the Seventh Circuit. In October 2018, the U.S. Court of Appeals for the Seventh Circuit affirmed the Tax Court’s decision. Exelon filed a petition seeking rehearing of the Seventh Circuit’s decision, but the Seventh Circuit denied that petition in December 2018. In the first quarter of 2019, Exelon elected not to seek a further review by the U.S. Supreme Court. As a result, Exelon's and ComEd's unrecognized tax benefits decreased by approximately $33 million and $2 million , respectively, in the first quarter of 2019. Reasonably possible the total amount of unrecognized tax benefits could significantly increase or decrease within 12 months after the reporting date Settlement of Income Tax Audits, Refund Claims, and Litigation Exelon, Generation, PHI and ACE have the following unrecognized federal and state tax benefits that could significantly decrease within the 12 months after the reporting date as a result of completing audits, potential settlements, refund claims, and the outcomes of pending court cases as of September 30, 2019 : Exelon (a) Generation (a) PHI (b) ACE (b) $ 425 $ 411 $ 14 $ 14 __________ (a) Exelon and Generation have $411 million that, if recognized, would decrease the effective tax rate. (b) The unrecognized tax benefit related to PHI and ACE, if recognized, may be included in future base rates and that portion would have no impact to the effective tax rate. Other Income Tax Matters Marginal State Income Tax Rate (Exelon, Generation) In the third quarter of 2019, Exelon reviewed and updated its marginal state income tax rates based on 2018 state apportionment rates. As a result of the rate changes, the following accounting adjustments were recorded as of September 30, 2019: Exelon Generation Increase to deferred income tax liability $ 23 $ 9 Increase to income tax expense, net of federal taxes 23 9 State Income Tax Law Changes On June 5, 2019, the Governor of Illinois signed a tax bill which would increase the Illinois corporate income tax rate from 9.50% to 10.49% effective for tax years beginning on or after January 1, 2021. The tax rate is contingent upon ratification of state constitutional amendments in November 2020. The effect of the rate change will be recognized in the period in which the new legislation is enacted. Exelon, Generation and ComEd do not expect a material impact to their financial statements as a result of the rate change.

Nuclear Decommissioning (Exelon

Nuclear Decommissioning (Exelon and Generation)	9 Months Ended
	Sep. 30, 2019
Environmental Remediation Obligations [Abstract]
Nuclear Decommissioning (Exelon and Generation)	Nuclear Decommissioning (Exelon and Generation) Nuclear Decommissioning Asset Retirement Obligations (Exelon and Generation) 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 updates its ARO annually, 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 financial statement impact for changes in the ARO, on an individual unit basis, due to the changes in and timing of estimated cash flows generally result in a corresponding change in the unit’s ARC within Property, plant and equipment on Exelon’s and Generation’s Consolidated Balance Sheets. If the ARO decreases for a Non-Regulatory Agreement unit without any remaining ARC, the corresponding change is recorded as decrease in Operating and maintenance expense within Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. The following table provides a rollforward of the nuclear decommissioning ARO reflected in Exelon’s and Generation’s Consolidated Balance Sheets from December 31, 2018 to September 30, 2019 : Nuclear decommissioning ARO at December 31, 2018 (a)(b) $ 10,005 Sale of Oyster Creek (755 ) Accretion expense 361 Net increase due to changes in, and timing of, estimated future cash flows 211 Costs incurred related to decommissioning plants (52 ) Nuclear decommissioning ARO at September 30, 2019 (a) $ 9,770 _________ (a) Includes $127 million and $22 million as the current portion of the ARO at September 30, 2019 and December 31, 2018 , respectively, which is included in Other current liabilities in Exelon’s and Generation’s Consolidated Balance Sheets. (b) Includes $772 million of ARO related to Oyster Creek which was classified as Liabilities held for sale in Exelon's and Generation's Consolidated Balance Sheets at December 31, 2018 . See Note 3 — Mergers, Acquisitions and Dispositions for additional information. During the nine months ended September 30, 2019 , Exelon's and Generation’s total nuclear ARO decreased by approximately $235 million , primarily reflecting the sale of Oyster Creek, partially offset by the accretion of the ARO liability due to the passage of time and the net impacts of ARO updates completed during the first and third quarters of 2019. The first quarter 2019 ARO update included an increase of approximately $330 million for a change in the assumed retirement timing probabilities for certain economically challenged nuclear plants and a $110 million decrease for the impacts of revised decommissioning cost estimates for TMI which incorporate site specific decommissioning planning activities associated with the early retirement of TMI on September 20, 2019. The TMI ARO adjustment resulted in an $85 million decrease in Operating and maintenance expense within Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. See Note 8 — Early Plant Retirements for additional information. The third quarter 2019 ARO update included a decrease of approximately $300 million due to lower estimated costs to decommission Nine Mile Point, Ginna, Braidwood, Byron and LaSalle nuclear units resulting from the completion of updated cost studies, partially offset by an increase of approximately $280 million for other impacts that included updated cost escalation rates, primarily for labor, equipment and materials, and current discount rates. The third quarter ARO adjustment resulted in a $65 million decrease in Operating and maintenance expense within Exelon and Generation's Consolidated Statements of Operations and Comprehensive Income. NDT Funds (Exelon and Generation) Exelon and Generation had NDT funds totaling $12,862 million and $12,695 million at September 30, 2019 and December 31, 2018 , respectively. The NDT funds included $890 million at December 31, 2018 , related to Oyster Creek NDT funds which were classified as Assets held for sale in Exelon's and Generation's Consolidated Balance Sheets. See Note 3 — Mergers, Acquisitions and Dispositions for additional information regarding the sale of Oyster Creek. The NDT funds also include $156 million and $144 million for the current portion of the NDT funds at September 30, 2019 and December 31, 2018 , respectively, which are included in Other current assets in Exelon's and Generation's Consolidated Balance Sheets. See Note 17 — Supplemental Financial Information for additional information on activities of the NDT funds. NRC Minimum Funding Requirements (Exelon and Generation) 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 April 1, 2019 for all units except for Zion Station which is included in a separate report to the NRC submitted by ZionSolutions, LLC. The status report demonstrated adequate decommissioning funding assurance as of December 31, 2018 for all units except for Clinton and Peach Bottom Unit 1. As of February 28, 2019, Clinton demonstrated adequate minimum funding assurance due to market recovery and no further action is required. This demonstration was also included in the April 1, 2019 submittal. As a former PECO plant, financial assurance for decommissioning Peach Bottom Unit 1 is provided by the NDT fund, collections from PECO ratepayers, and the ability to adjust those collections in accordance with the approved PAPUC tariff. No additional actions are required aside from the PAPUC filing in accordance with the tariff. See Note 15 — Asset Retirement Obligations of the Exelon 2018 Form 10-K for information regarding the amount collected from PECO ratepayers for decommissioning cost.

Retirement Benefits (All Regist

Retirement Benefits (All Registrants)	9 Months Ended
	Sep. 30, 2019
Retirement Benefits [Abstract]
Retirement Benefits (All Registrants)	Retirement Benefits (All Registrants) Effective January 1, 2019, Exelon merged the Exelon Corporation Cash Balance Pension Plan (CBPP) into the Exelon Corporation Retirement Program (ECRP). The merging of the plans is not changing the benefits offered to the plan participants and, thus, has no impact on Exelon's pension obligation. However, beginning in 2019, actuarial losses and gains related to the CBPP and ECRP are being amortized over participants’ average remaining service period of the merged ECRP rather than each individual plan. Defined Benefit Pension and OPEB During the first quarter of 2019, Exelon received an updated valuation of its pension and OPEB to reflect actual census data as of January 1, 2019. This valuation resulted in an increase to the pension and OPEB obligations of $75 million and $36 million , respectively. Additionally, accumulated other comprehensive loss increased by $39 million (after-tax) and regulatory assets and liabilities increased by $53 million and decreased by $5 million , respectively. The majority of the 2019 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 4.31% . The majority of the 2019 OPEB cost is calculated using an expected long-term rate of return on plan assets of 6.67% for funded plans and a discount rate of 4.30% . A portion of the net periodic benefit cost for all plans is capitalized within the Consolidated Balance Sheets. The following table presents the components of Exelon's net periodic benefit costs, prior to capitalization, for the three and nine months ended September 30, 2019 and 2018 . Pension Benefits OPEB 2019 2018 2019 2018 Components of net periodic benefit cost: Service cost $ 89 $ 100 $ 23 $ 28 Interest cost 221 201 47 43 Expected return on assets (306 ) (312 ) (38 ) (43 ) Amortization of: Prior service benefit — — (45 ) (47 ) Actuarial loss 104 158 11 18 Settlement charges 7 — — — Contractual termination benefits 1 — — — Net periodic benefit cost $ 116 $ 147 $ (2 ) $ (1 ) Pension Benefits OPEB 2019 2018 2019 2018 Components of net periodic benefit cost: Service cost $ 267 $ 303 $ 70 $ 84 Interest cost 663 602 141 131 Expected return on assets (918 ) (939 ) (115 ) (130 ) Amortization of: Prior service cost (benefit) — 1 (134 ) (140 ) Actuarial loss 310 472 34 50 Settlement charges 7 1 — — Contractual termination benefits 1 — — — Net periodic benefit cost $ 330 $ 440 $ (4 ) $ (5 ) The amounts below represent the Registrants' allocated pension and OPEB plan costs. For Exelon, the service cost component is included in Operating and maintenance expense and Property, plant and equipment, net while the non-service cost components are included in Other, net and Regulatory assets. For Generation and the Utility Registrants, the service cost and non-service cost components are included in Operating and maintenance expense and Property, plant and equipment, net in their consolidated financial statements. Three Months Ended September 30, Nine Months Ended September 30, Pension and OPEB Costs 2019 2018 2019 2018 Exelon $ 114 $ 145 $ 326 $ 435 Generation 37 50 100 151 ComEd 23 45 70 133 PECO 4 5 9 14 BGE 16 15 47 44 PHI 23 17 71 51 Pepco 6 3 19 10 DPL 4 2 11 5 ACE 4 3 12 10 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 and/or after-tax income in accordance with specified guidelines. All Registrants match a percentage of the employee contributions up to certain limits. The following table presents the matching contributions to the savings plans during the three and nine months ended September 30, 2019 and 2018 , respectively. Three Months Ended September 30, Nine Months Ended September 30, Savings Plan Matching Contributions 2019 2018 2019 2018 Exelon $ 36 $ 44 $ 101 $ 126 Generation 14 23 41 65 ComEd 9 8 26 23 PECO 2 2 7 7 BGE 4 2 9 5 PHI 4 4 8 10 Pepco 1 1 2 2 DPL 1 1 2 2 ACE 1 1 1 2

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Income (Exelon)	9 Months Ended
	Sep. 30, 2019
Changes in Accumulated Other Comprehensive Income [Abstract]
Changes in Accumulated Other Comprehensive Income Note [Text Block]	Changes in Accumulated Other Comprehensive Income (Exelon) The following tables present changes in Exelon's AOCI, net of tax, by component: Three Months Ended September 30, 2019 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Currency Items AOCI of Investments in Unconsolidated Affiliates (b) Total Beginning balance $ (2 ) $ (2,957 ) $ (29 ) $ (2 ) $ (2,990 ) OCI before reclassifications — 6 (2 ) — 4 Amounts reclassified from AOCI — 21 — 2 23 Net current-period OCI — 27 (2 ) 2 27 Ending balance $ (2 ) $ (2,930 ) $ (31 ) $ — $ (2,963 ) Three Months Ended September 30, 2018 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Currency Items AOCI of Investments in Unconsolidated Affiliates (b) Total Beginning balance $ (2 ) $ (2,890 ) $ (29 ) $ — $ (2,921 ) OCI before reclassifications — 5 2 — 7 Amounts reclassified from AOCI — 45 — — 45 Net current-period OCI — 50 2 — 52 Ending balance $ (2 ) $ (2,840 ) $ (27 ) $ — $ (2,869 ) Nine Months Ended September 30, 2019 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Currency Items AOCI of Investments in Unconsolidated Affiliates (b) Total Beginning balance $ (2 ) $ (2,960 ) $ (33 ) $ — $ (2,995 ) OCI before reclassifications — (32 ) 2 (2 ) (32 ) Amounts reclassified from AOCI — 62 — 2 64 Net current-period OCI — 30 2 — 32 Ending balance $ (2 ) $ (2,930 ) $ (31 ) $ — $ (2,963 ) Nine Months Ended September 30, 2018 Gains (Losses) on Cash Flow Hedges Unrealized gains (losses) on Marketable Securities Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Currency Items AOCI of Investments in Unconsolidated Affiliates (b) Total Beginning balance $ (14 ) $ 10 $ (2,998 ) $ (23 ) $ (1 ) $ (3,026 ) OCI before reclassifications 11 — 22 (4 ) 1 30 Amounts reclassified from AOCI 1 — 136 — — 137 Net current-period OCI 12 — 158 (4 ) 1 167 Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard (c) — (10 ) — — — (10 ) Ending balance $ (2 ) $ — $ (2,840 ) $ (27 ) $ — $ (2,869 ) _________ (a) AOCI amounts are included in the computation of net periodic pension and OPEB cost. See Note 14 — Retirement Benefits for additional information. See Exelon's Statements of Operations and Comprehensive Income for individual components of AOCI. (b) All amounts are net of noncontrolling interests. (c) Exelon prospectively adopted the new standard Recognition and Measurement of Financial Assets and Liabilities. The standard was adopted as of January 1, 2018, which resulted in an increase to Retained earnings and Accumulated other comprehensive loss of $10 million for Exelon. The amounts reclassified related to Rabbi Trusts. The following table presents income tax benefit (expense) allocated to each component of Exelon's other comprehensive income (loss): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 6 $ 6 $ 18 $ 18 Actuarial loss reclassified to periodic benefit cost (13 ) (21 ) (39 ) (65 ) Pension and non-pension postretirement benefit plans valuation adjustment — (2 ) 14 (8 )

Commitments and Contingencies (

Commitments and Contingencies (All Registrants)	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies (All Registrants)	Commitments and Contingencies (All Registrants) The following is an update to the current status of commitments and contingencies set forth in Note 22 of the Exelon 2018 Form 10-K. See Note 5 — Mergers, Acquisitions and Dispositions of the Exelon 2018 Form 10-K for additional information on the PHI Merger commitments. Commitments PHI Merger Commitments (Exelon, PHI, Pepco, DPL and ACE). Approval of the PHI Merger in Delaware, New Jersey, Maryland and the District of Columbia was conditioned upon Exelon and PHI agreeing to certain commitments. The following amounts represent total commitment costs that have been recorded since the acquisition date and the total remaining obligations for Exelon, PHI, Pepco, DPL and ACE as of September 30, 2019 : Description Exelon PHI Pepco DPL ACE Total commitments $ 513 $ 320 $ 120 $ 89 $ 111 Remaining commitments (a) 112 82 67 9 6 _________ (a) Remaining commitments extend through 2026 and include rate credits, energy efficiency programs. and delivery system modernization. In addition, Exelon is committed to develop or to assist in the commercial development of approximately 37 MWs of new solar generation in Maryland, District of Columbia, and Delaware at an estimated cost of approximately $127 million , which will generate future earnings at Exelon and Generation. Investment costs, which are expected to be primarily capital in nature, are recognized as incurred and recorded in Exelon's and Generation's financial statements. As of September 30, 2019 , 27 MWs of new generation were developed and Exelon and Generation have incurred costs of $107 million . Exelon has also committed to purchase 100 MWs of wind energy in PJM. DPL has committed to conducting three RFPs to procure up to a total of 120 MWs of wind RECs for the purpose of meeting Delaware's renewable portfolio standards. DPL has conducted two of the three wind REC RFPs. The first 40 MW wind REC tranche was conducted in 2017 and did not result in a purchase agreement. The second 40 MW wind REC tranche was conducted in 2018 and resulted in a proposed REC purchase agreement that was approved by the DPSC in March 2019. The third and final 40 MW wind REC tranche will be conducted in 2022. Commercial Commitments (All Registrants). The Registrants’ commercial commitments as of September 30, 2019 , representing commitments potentially triggered by future events were as follow s: Expiration within Total 2019 2020 2021 2022 2023 2024 and beyond Exelon Letters of credit $ 1,718 $ 1,192 $ 515 $ 11 $ — $ — $ — Surety bonds (a) 991 315 638 38 — — — Financing trust guarantees 378 — — — — — 378 Guaranteed lease residual values (b) 26 — 2 3 4 3 15 Total commercial commitments $ 3,113 $ 1,507 $ 1,155 $ 52 $ 4 $ 3 $ 393 Generation Letters of credit $ 1,686 $ 1,179 $ 496 $ 11 $ — $ — $ — Surety bonds (a) 790 298 492 — — — — Total commercial commitments $ 2,476 $ 1,477 $ 988 $ 11 $ — $ — $ — ComEd Letters of credit $ 7 $ 4 $ 3 $ — $ — $ — $ — Surety bonds (a) 50 5 43 2 — — — Financing trust guarantees 200 — — — — — 200 Total commercial commitments $ 257 $ 9 $ 46 $ 2 $ — $ — $ 200 PECO Surety bonds (a) $ 9 $ 1 $ 8 $ — $ — $ — $ — Financing trust guarantees 178 — — — — — 178 Total commercial commitments $ 187 $ 1 $ 8 $ — $ — $ — $ 178 BGE Letters of credit $ 8 $ 2 $ 6 $ — $ — $ — $ — Surety bonds (a) 17 2 15 — — — — Total commercial commitments $ 25 $ 4 $ 21 $ — $ — $ — $ — PHI Letters of credit $ 11 $ 1 $ 10 $ — $ — $ — $ — Surety bonds (a) 24 5 19 — — — — Guaranteed lease residual values (b) 26 — 2 3 4 3 15 Total commercial commitments $ 61 $ 6 $ 31 $ 3 $ 4 $ 3 $ 15 Pepco Letters of credit $ 10 $ — $ 10 $ — $ — $ — $ — Surety bonds (a) 17 2 15 — — — — Guaranteed lease residual values (b) 9 — — 1 1 1 6 Total commercial commitments $ 36 $ 2 $ 25 $ 1 $ 1 $ 1 $ 6 DPL Letters of credit $ 1 $ 1 $ — $ — $ — $ — $ — Surety bonds (a) 4 2 2 — — — — Guaranteed lease residual values (b) 11 — 1 1 2 1 6 Total commercial commitments $ 16 $ 3 $ 3 $ 1 $ 2 $ 1 $ 6 ACE Surety bonds (a) $ 3 $ 1 $ 2 $ — $ — $ — $ — Guaranteed lease residual values (b) 7 — 1 1 1 1 3 Total commercial commitments $ 10 $ 1 $ 3 $ 1 $ 1 $ 1 $ 3 _________ (a) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (b) Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The lease term associated with these assets ranges from 1 to 8 years . The maximum potential obligation at the end of the minimum lease term would be $68 million guaranteed by Exelon and PHI, of which $22 million , $29 million and $17 million is guaranteed by Pepco, DPL and ACE, respectively. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote. Environmental Remediation Matters General (All Registrants). The Registrants’ operations have in the past, and may in the future, require substantial expenditures 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. Unless otherwise disclosed, the Registrants cannot reasonably estimate whether they will incur 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. Additional costs could have a material, unfavorable impact in the Registrants' financial statements. MGP Sites (Exelon, ComEd, PECO, BGE, PHI and DPL). ComEd, PECO, BGE and DPL have identified sites where former MGP or gas purification 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 21 sites 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 2025. • PECO has 8 sites that 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 2022. • BGE has 4 sites that currently require some level of remediation and/or ongoing activity. BGE expects the majority of the remediation at these sites to continue through at least 2021. • DPL has 1 site that is currently under study and the required cost at the site is not expected to be material. The historical nature of the MGP and gas purification sites and the fact that many of the sites have been buried and built over, impacts the ability to determine a precise estimate of the ultimate costs prior to initial sampling and determination of the exact scope and method of remedial activity. Management determines its best estimate of remediation costs using all available information at the time of each study, including probabilistic and deterministic modeling for ComEd and PECO, and the remediation standards currently required by the applicable state environmental agency. Prior to completion of any significant clean up, each site remediation plan is approved by the appropriate state environmental agency. 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. While BGE and DPL do not have riders for MGP clean-up costs, they have historically received recovery of actual clean-up costs in distribution rates. As of September 30, 2019 and December 31, 2018 , the Registrants had accrued the following undiscounted amounts for environmental liabilities in Other current liabilities and Other deferred credits and other liabilities within their respective Consolidated Balance Sheets: September 30, 2019 December 31, 2018 Total environmental investigation and remediation liabilities Portion of total related to MGP investigation and remediation Total environmental investigation and remediation liabilities Portion of total related to MGP investigation and remediation Exelon $ 507 $ 346 $ 496 $ 356 Generation 107 — 108 — ComEd 328 327 329 327 PECO 20 18 27 25 BGE 3 1 5 4 PHI 49 — 27 — Pepco 47 — 25 — DPL 1 — 1 — ACE 1 — 1 — Cotter Corporation (Exelon and Generation). The 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. In 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. Including Cotter, there are three PRPs participating in the West Lake Landfill remediation proceeding. Investigation by Generation has identified a number of other parties who also may be PRPs and could be liable to contribute to the final remedy. Further investigation is ongoing. In September 2018 the EPA issued its Record of Decision (ROD) Amendment for the selection of the final remedy. The ROD modified the EPA’s previously proposed plan for partial excavation of the radiological materials by reducing the depths of the excavation. The ROD also allows for variation in depths of excavation depending on radiological concentrations. The EPA and the PRPs have entered into a Consent Agreement to perform the Remedial Design, which is expected to be completed in the 2020 - 2021 time frame. In March 2019 the PRPs received Special Notice Letters from the EPA to perform the Remedial Action work. The EPA has established a deadline of October 2019 for the PRPs to provide a good faith offer to conduct, or finance, the Remedial Action work . This schedule can be extended by the EPA pending completion of the Remedial Design. The estimated cost of the remedy, taking into account the current EPA technical requirements and the total costs expected to be incurred by the PRPs in fully executing the remedy, is approximately $280 million , including cost escalation on an undiscounted basis, which would be allocated among the final group of PRPs. Generation has determined that a loss associated with the EPA’s partial excavation and enhanced landfill cover remedy is probable and has recorded a liability included in the table above, that reflects management’s best estimate of Cotter’s allocable share of the ultimate cost. Given the joint and several nature of this liability, the magnitude of Generation’s ultimate liability will depend on the actual costs incurred to implement the required remediation remedy as well as on the nature and terms of any cost-sharing arrangements with the final group of PRPs. Therefore, it is reasonably possible that the ultimate cost and Generation’s associated allocable share could differ significantly once these uncertainties are resolved, which could have a material impact on Exelon's and Generation's future financial statements. One of the other PRPs has indicated it will be making a contribution claim against Cotter for costs that it has incurred to prevent the subsurface fire from spreading to those areas of the West Lake Landfill where radiological materials are believed to have been disposed. At this time, Exelon and Generation do not possess sufficient information to assess this claim and therefore are unable to estimate a range of loss, if any. As such, no liability has been recorded for the potential contribution claim. It is reasonably possible, however, that resolution of this matter could have a material, unfavorable impact on Exelon’s and Generation's financial statements. In January 2018, the PRPs were advised by the EPA that it will begin an additional investigation and evaluation of groundwater conditions at the West Lake Landfill. In September 2018, the PRPs agreed to an Administrative Settlement Agreement and Order on Consent for the performance by the PRPs of the groundwater RI/FS. The purpose of this RI/FS is to define the nature and extent of any groundwater contamination from the West Lake Landfill site and evaluate remedial alternatives. Generation estimates the undiscounted cost for the groundwater RI/FS to be approximately $20 million . Generation determined a loss associated with the RI/FS is probable and has recorded a liability included in the table above that reflects management’s best estimate of Cotter’s allocable share of the cost among the PRPs. At this time Generation cannot predict the likelihood or the extent to which, if any, remediation activities may be required and therefore cannot estimate a reasonably possible range of loss for response costs beyond those associated with the RI/FS component. It is reasonably possible, however, that resolution of this matter could have a material, unfavorable impact on Exelon’s and Generation’s future financial statements. In August 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 FUSRAP. 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 from all PRPs. Pursuant to a series of annual agreements since 2011, the DOJ and the PRPs have tolled the statute of limitations until February 2020 so that settlement discussions could proceed. Generation has determined that a loss associated with this matter is probable under its indemnification agreement with Cotter and has recorded an estimated liability, which is included in the table above. Benning Road Site (Exelon, Generation, PHI and Pepco) . In September 2010, PHI received a letter from EPA identifying the Benning Road site as one of six land-based sites potentially contributing to contamination of the lower Anacostia River. A portion of the site was formerly the location of a Pepco Energy Services electric generating facility, which was deactivated in June 2012. The remaining portion of the site consists of a Pepco transmission and distribution service center that remains in operation. In December 2011, the U.S. District Court for the District of Columbia approved a Consent Decree entered into by Pepco and Pepco Energy Services with the DOEE, which requires Pepco and Pepco Energy Services to conduct a Remediation Investigation (RI)/ Feasibility Study (FS) for the Benning Road site and an approximately 10 to 15-acre portion of the adjacent Anacostia River. Since 2013, Pepco and Pepco Energy Services (now Generation, pursuant to Exelon's 2016 acquisition of PHI) have been performing RI work and have submitted multiple draft RI reports to the DOEE. Once the RI work is completed, Pepco and Generation will issue a draft “final” RI report for review and comment by DOEE and the public. Pepco and Generation will then proceed to develop a FS to evaluate possible remedial alternatives for submission to DOEE. The Court has established a schedule for completion of the RI and FS, and approval by the DOEE, by September 16, 2021. DOEE will then prepare a Proposed Plan and issue a Record of Decision identifying any further response actions determined to be necessary, after considering public comment on the Proposed Plan. PHI, Pepco and Generation have determined that a loss associated with this matter is probable and have accrued an estimated liability, which is included in the table above. Anacostia River Tidal Reach (Exelon, PHI and Pepco) . Contemporaneous with the Benning Road site RI/FS being performed by Pepco and Generation, DOEE and the National Park Service have been conducting a separate RI/FS focused on the entire tidal reach of the Anacostia River extending from just north of the Maryland-District of Columbia boundary line to the confluence of the Anacostia and Potomac Rivers. The river-wide RI incorporated the results of the river sampling performed by Pepco and Pepco Energy Services as part of the Benning RI/FS, as well as similar sampling efforts conducted by owners of other sites adjacent to this segment of the river and supplemental river sampling conducted by DOEE’s contractor. DOEE asked Pepco, along with parties responsible for other sites along the river, to participate in a "Consultative Working Group" to provide input into the process for future remedial actions and to ensure proper coordination with the other river cleanup efforts currently underway, including cleanup of the river segment adjacent to the Benning Road site resulting from the Benning Road site RI/FS. In addition, the District of Columbia Council directed DOEE to form an official advisory committee made up of members of federal, state and local environmental regulators, community and environmental groups and various academic and technical experts to provide guidance and support to DOEE as the project progressed. This group, called the Anacostia Leadership Council, has met regularly since it was formed. Pepco has participated in the Consultative Working Group. In April 2018, DOEE released a draft RI report for public review and comment. Pepco submitted written comments to the draft RI and participated in a public hearing. The District of Columbia Council has set a deadline of December 31, 2019 for completion of the Record of Decision. An appropriate liability for Pepco’s share of investigation costs has been accrued and is included in the table above. Pepco has determined that it is probable that costs for remediation will be incurred and recorded a liability in the third quarter 2019 for management’s best estimate of its share based on DOEE’s stated position following a series of meetings attended by representatives from the Anacostia Leadership Council and the Consultative Working Group. A draft FS, which Pepco believes will include the process to identify potential short-term remedies and actions based on the technical findings in the RI report and their estimated costs to the extent possible, is being prepared by DOEE and is expected later in the fourth quarter of 2019. DOEE and likely the National Park Service will continue to oversee ongoing remediation efforts and potential longer-term remedies for the Anacostia River. Pepco has concluded that incremental exposure remains reasonably possible, however management cannot reasonably estimate a range of loss beyond the amounts recorded, which are included in the table above. In addition to the activities associated with the remedial process outlined above, there is a complementary statutory program that requires an assessment to determine if any natural resources have been damaged as a result of the contamination that is being remediated, and, if so, that a plan be developed by the federal, state and local Natural Resource Damage Trustees, who are defined by CERCLA as the responsible parties for the restoration or compensation for any loss of those resources from the environmental contaminants at the site. If natural resources cannot be restored, then compensation for the injury can be sought from the responsible parties. The assessment of Natural Resource Damages (NRD) typically takes place following cleanup because cleanups sometimes also effectively restore habitat. During the second quarter of 2018, Pepco became aware that the Trustees are in the beginning stages of this process that often takes many years beyond the remedial decision to complete. Pepco has concluded that a loss associated with the eventual NRD assessment is reasonably possible. Due to the very early stage of the assessment process it cannot reasonably estimate the range of loss. Litigation and Regulatory Matters Asbestos Personal Injury Claims (Exelon and Generation). Generation maintains a reserve for claims associated with asbestos-related personal injury actions in certain facilities that are currently owned by Generation or were previously owned by ComEd and PECO. The estimated liabilities are recorded on an undiscounted basis and exclude the estimated legal costs associated with handling these matters, which could be material. At September 30, 2019 and December 31, 2018 , Exelon and Generation had recorded estimated liabilities of approximately $83 million and $79 million , respectively, in total for asbestos-related bodily injury claims. As of September 30, 2019 , approximately $25 million of this amount related to 257 open claims presented to Generation, while the remaining $58 million is for estimated future asbestos-related bodily injury claims anticipated to arise through 2055, based on actuarial assumptions and analyses, which are updated on an annual basis. On a quarterly basis, Generation monitors actual experience against the number of forecasted claims to be received and expected claim payments and evaluates whether adjustments to the estimated liabilities are necessary. It is reasonably possible that additional exposure to estimated future asbestos-related bodily injury claims in excess of the amount accrued could have a material, unfavorable impact on Exelon’s and Generation’s financial statements. City of Everett Tax Increment Financing Agreement (Exelon and Generation). On April 10, 2017, the City of Everett petitioned the Massachusetts Economic Assistance Coordinating Council (EACC) to revoke the 1999 tax increment financing agreement (TIF Agreement) relating to Mystic Units 8 and 9 on the grounds that the total investment in Mystic Units 8 and 9 materially deviates from the investment set forth in the TIF Agreement. On October 31, 2017, a three-member panel of the EACC conducted an administrative hearing on the City’s petition. On November 30, 2017, the hearing panel issued a tentative decision denying the City’s petition, finding that there was no material misrepresentation that would justify revocation of the TIF Agreement. On December 13, 2017, the tentative decision was adopted by the full EACC. On January 12, 2018, the City filed a complaint in Massachusetts Superior Court requesting, among other things, that the court set aside the EACC’s decision, grant the City’s request to decertify the Project and the TIF Agreement, and award the City damages for alleged underpaid taxes over the period of the TIF Agreement. Generation vigorously contested the City’s claims before the EACC and will continue to do so in the Massachusetts Superior Court proceeding. Generation continues to believe that the City’s claim lacks merit. Accordingly, Generation has not recorded a liability for payment resulting from such a revocation, nor can Generation estimate a reasonably possible range of loss, if any, associated with any such revocation. Further, it is reasonably possible that property taxes assessed in future periods, including those following the expiration of the current TIF Agreement in 2020, could be material to Generation’s financial statements. Subpoenas (Exelon and ComEd). Exelon and ComEd received a grand jury subpoena in the second quarter of 2019 from the U.S. Attorney’s Office for the Northern District of Illinois requiring production of information concerning their lobbying activities in the State of Illinois. On October 4, 2019, Exelon and ComEd received a second grand jury subpoena from the U.S. Attorney's Office for the Northern District of Illinois requiring production of records of any communications with certain individuals and entities. On October 22, 2019, the SEC notified Exelon and ComEd that it has also opened an investigation into their lobbying activities. Exelon and ComEd have cooperated fully and intend to continue to cooperate fully and expeditiously with the U.S. Attorney’s Office and the SEC. Exelon and ComEd cannot predict the outcome of the subpoenas or the SEC investigation. General (All Registrants). The Registrants are involved in various other litigation matters that are being defended and handled in the ordinary course of business. The assessment of whether a loss is probable or reasonably possible, and whether the loss or a range of loss is estimable, often involves a series of complex judgments about future events. The Registrants maintain accruals for such losses that are probable of being incurred and subject to reasonable estimation. Management is sometimes unable to estimate an amount or range of reasonably possible loss, particularly where (1) the damages sought are indeterminate, (2) the proceedings are in the early stages, or (3) the matters involve novel or unsettled legal theories. In such cases, there is considerable uncertainty regarding the timing or ultimate resolution of such matters, including a possible eventual loss.

Supplemental Financial Informat

Supplemental Financial Information (All Registrants)	9 Months Ended
	Sep. 30, 2019
Supplemental Financial Information [Abstract]
Supplemental Financial Information (All Registrants)	Supplemental Financial Information (All Registrants) Supplemental Statement of Operations Information The following tables provide additional information about material items recorded in the Registrants' Consolidated Statements of Operations and Comprehensive Income. Taxes other than income Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended September 30, 2019 Utility taxes (a) $ 241 $ 29 $ 66 $ 38 $ 21 $ 86 $ 81 $ 5 $ — Property 148 66 7 5 39 31 21 9 — Payroll 57 28 7 3 4 6 2 1 1 Three Months Ended September 30, 2018 Utility taxes (a) $ 253 $ 32 $ 67 $ 39 $ 23 $ 92 $ 87 $ 5 $ — Property 145 70 7 4 37 26 16 9 — Payroll 58 31 6 3 4 5 1 1 1 Nine Months Ended September 30, 2019 Utility taxes (a) $ 672 $ 87 $ 183 $ 102 $ 68 $ 231 $ 217 $ 14 $ — Property 444 205 22 12 114 91 64 25 2 Payroll 185 92 21 11 13 20 5 3 2 Nine Months Ended September 30, 2018 Utility taxes (a) $ 705 $ 92 $ 188 $ 102 $ 70 $ 253 $ 238 $ 15 $ — Property 416 204 22 12 106 71 45 24 2 Payroll 191 99 20 11 12 19 5 3 2 _________ (a) Generation’s utility tax represents gross receipts tax related to its retail operations, and the Utility Registrants' utility taxes represents municipal and state utility taxes and gross receipts taxes related to their operating revenues. The offsetting collection of utility taxes from customers is recorded in revenues in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Other, Net Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended September 30, 2019 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 67 $ 67 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 33 33 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units 89 89 — — — — — — — Non-regulatory agreement units 55 55 — — — — — — — Regulatory offset to NDT fund-related activities (b) (125 ) (125 ) — — — — — — — Decommissioning-related activities 119 119 — — — — — — — AFUDC — Equity 22 — 4 3 6 9 7 1 1 Non-service net periodic benefit cost (2 ) — — — — — — — — Three Months Ended September 30, 2018 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 214 $ 214 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 58 58 — — — — — — — Net unrealized (losses) gains on NDT funds Regulatory agreement units (66 ) (66 ) — — — — — — — Non-regulatory agreement units 72 72 — — — — — — — Regulatory offset to NDT fund-related activities (b) (110 ) (110 ) — — — — — — — Decommissioning-related activities 168 168 — — — — — — — AFUDC — Equity 16 — 4 1 5 6 6 — — Non-service net periodic benefit cost (12 ) — — — — — — — — Other, Net Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2019 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 197 $ 197 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 316 316 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units 565 565 — — — — — — — Non-regulatory agreement units 236 236 — — — — — — — Regulatory offset to NDT fund-related activities (b) (611 ) (611 ) — — — — — — — Decommissioning-related activities 703 703 — — — — — — — AFUDC — Equity 64 — 13 9 16 26 18 3 4 Non-service net periodic benefit cost 8 — — — — — — — — Nine Months Ended September 30, 2018 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 476 $ 476 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 257 257 — — — — — — — Net unrealized losses on NDT funds Regulatory agreement units (335 ) (335 ) — — — — — — — Non-regulatory agreement units (143 ) (143 ) — — — — — — — Regulatory offset to NDT fund-related activities (b) (110 ) (110 ) — — — — — — — Decommissioning-related activities 145 145 — — — — — — — AFUDC — Equity 47 — 12 3 13 19 17 2 — Non-service net periodic benefit cost (33 ) — — — — — — — — _________ (a) Realized income includes interest, dividends and realized gains and losses on sales of NDT fund investments. (b) Includes the elimination of decommissioning-related activities for the Regulatory Agreement Units, including the elimination of income taxes related to all NDT fund activity for those units. See Note 15 — Asset Retirement Obligations of the Exelon 2018 Form 10-K for additional information regarding the accounting for nuclear decommissioning. Supplemental Cash Flow Information The following tables provide additional information about material items recorded in the Registrants' Consolidated Statements of Cash Flows. Depreciation, amortization and accretion Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2019 Property, plant and equipment (a) $ 2,803 $ 1,184 $ 661 $ 225 $ 263 $ 405 $ 178 $ 109 $ 89 Amortization of regulatory assets (a) 390 — 106 22 105 157 103 29 25 Amortization of intangible assets, net (a) 44 37 — — — — — — — Amortization of energy contract assets and liabilities (b) 14 14 — — — — — — — Nuclear fuel (c) 771 771 — — — — — — — ARO accretion (d) 371 371 — — — — — — — Total depreciation, amortization and accretion $ 4,393 $ 2,377 $ 767 $ 247 $ 368 $ 562 $ 281 $ 138 $ 114 Nine Months Ended September 30, 2018 Property, plant and equipment (a) $ 2,829 $ 1,347 $ 613 $ 204 $ 249 $ 355 $ 161 $ 97 $ 70 Amortization of regulatory assets (a) 412 — 83 20 109 200 125 38 37 Amortization of intangible assets, net (a) 43 36 — — — — — — — Amortization of energy contract assets and liabilities (b) 8 8 — — — — — — — Nuclear fuel (c) 852 852 — — — — — — — ARO accretion (d) 367 365 — — — — — — — Total depreciation, amortization and accretion $ 4,511 $ 2,608 $ 696 $ 224 $ 358 $ 555 $ 286 $ 135 $ 107 _________ (a) Included in Depreciation and amortization in the Registrants' Consolidated Statements of Operations and Comprehensive Income. (b) Included in Operating revenues or Purchased power and fuel expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (c) Included in Purchased power and fuel expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (d) Included in Operating and maintenance expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Other non-cash operating activities Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2019 Pension and non-pension postretirement benefit costs $ 324 $ 98 $ 70 $ 9 $ 45 $ 71 $ 19 $ 11 $ 12 Provision for uncollectible accounts 89 20 26 22 5 16 7 2 6 Other decommissioning-related activity (a) (400 ) (400 ) — — — — — — — Energy-related options (b) 21 21 — — — — — — — Amortization of rate stabilization deferral (8 ) — — — — (8 ) (9 ) 1 — Discrete impacts from EIMA and FEJA (c) 80 — 80 — — — — — — Long-term incentive plan 33 — — — — — — — — Amortization of operating ROU asset 193 138 2 — 23 26 6 7 4 Change in environmental liabilities 23 — — — — 23 23 — — Nine Months Ended September 30, 2018 Pension and non-pension postretirement benefit costs $ 435 $ 151 $ 133 $ 14 $ 43 $ 51 $ 10 $ 5 $ 10 Provision for uncollectible accounts 133 38 30 25 6 32 12 6 14 Other decommissioning-related activity (a) (39 ) (39 ) — — — — — — — Energy-related options (b) 4 4 — — — — — — — Amortization of rate stabilization deferral — — — — — — — — — Discrete impacts from EIMA and FEJA (c) 27 — 27 — — — — — — Long-term incentive plan 84 — — — — — — — — Asset retirement costs 20 — — — — 20 22 (1 ) (1 ) _______ (a) Includes the elimination of decommissioning-related 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 2018 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 in Operating revenues and expenses. (c) Reflects the change in ComEd's distribution and energy efficiency formula rates. See Note 6 — Regulatory Matters for additional information. The following tables provide a reconciliation of cash, cash equivalents and restricted cash reported within the Registrants’ Consolidated Balance Sheets that sum to the total of the same amounts in their Consolidated Statements of Cash Flows. Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2019 Cash and cash equivalents $ 1,683 $ 1,019 $ 76 $ 224 $ 130 $ 99 $ 18 $ 11 $ 13 Restricted cash 309 126 124 6 1 38 34 — 3 Restricted cash included in other long-term assets 186 — 171 — — 15 — — 15 Total cash, cash equivalents and restricted cash $ 2,178 $ 1,145 $ 371 $ 230 $ 131 $ 152 $ 52 $ 11 $ 31 December 31, 2018 Cash and cash equivalents $ 1,349 $ 750 $ 135 $ 130 $ 7 $ 124 $ 16 $ 23 $ 7 Restricted cash 247 153 29 5 6 43 37 1 4 Restricted cash included in other long-term assets 185 — 166 — — 19 — — 19 Total cash, cash equivalents and restricted cash $ 1,781 $ 903 $ 330 $ 135 $ 13 $ 186 $ 53 $ 24 $ 30 September 30, 2018 Cash and cash equivalents $ 1,918 $ 1,187 $ 124 $ 102 $ 113 $ 153 $ 12 $ 110 $ 11 Restricted cash 240 152 12 5 3 42 35 — 7 Restricted cash included in other long-term assets 163 — 144 — — 19 — — 19 Total cash, cash equivalents and restricted cash $ 2,321 $ 1,339 $ 280 $ 107 $ 116 $ 214 $ 47 $ 110 $ 37 December 31, 2017 Cash and cash equivalents $ 898 $ 416 $ 76 $ 271 $ 17 $ 30 $ 5 $ 2 $ 2 Restricted cash 207 138 5 4 1 42 35 — 6 Restricted cash included in other long-term assets 85 — 63 — — 23 — — 23 Total cash, cash equivalents and restricted cash $ 1,190 $ 554 $ 144 $ 275 $ 18 $ 95 $ 40 $ 2 $ 31 For additional information on restricted cash see Note 1 — Significant Accounting Policies of the Exelon 2018 Form 10-K. Supplemental Balance Sheet Information The following tables provide additional information about material items recorded in the Registrants' Consolidated Balance Sheets. Unbilled customer revenues Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2019 $ 1,256 $ 676 $ 212 $ 102 $ 103 $ 163 $ 91 $ 38 $ 34 December 31, 2018 1,656 965 223 114 168 186 97 59 30 Accrued expenses Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2019 Compensation-related accruals (a) $ 880 $ 336 $ 133 $ 48 $ 63 $ 86 $ 26 $ 17 $ 13 Taxes accrued 431 247 56 13 64 80 61 17 3 Interest accrued 421 106 62 33 36 78 37 20 19 December 31, 2018 Compensation-related accruals (a) $ 1,191 $ 479 $ 187 $ 49 $ 68 $ 99 $ 29 $ 19 $ 12 Taxes accrued 412 226 71 28 46 74 58 4 5 Interest accrued 334 77 105 33 39 50 25 8 12 _________ (a) Primarily includes accrued payroll, bonuses and other incentives, vacation and benefits.

Segment Information (All Regist

Segment Information (All Registrants)	9 Months Ended
	Sep. 30, 2019
Segment Reporting [Abstract]
Segment Information (All Registrants)	Segment Information (All Registrants) Operating segments for each of the Registrants are determined based on information used by the CODM in deciding how to evaluate performance and allocate resources at each of the Registrants. Exelon has eleven reportable segments, which include Generation's five reportable segments consisting of the Mid-Atlantic, Midwest, New York, ERCOT and all other power regions referred to collectively as “Other Power Regions” and ComEd, PECO, BGE, and PHI's three reportable segments consisting of Pepco, DPL and ACE. ComEd, PECO, BGE, Pepco, DPL and ACE each represent a single reportable segment, and as such, no separate segment information is provided for these Registrants. Exelon, ComEd, PECO, BGE, Pepco, DPL and ACE's CODMs evaluate the performance of and allocate resources to ComEd, PECO, BGE, Pepco, DPL and ACE based on net income. The basis for Generation's reportable segments is the integrated management of its electricity business that is located in different geographic regions, and largely representative of the footprints of ISO/RTO and/or NERC regions, which utilize multiple supply sources to provide electricity through various distribution channels (wholesale and retail). Generation's hedging strategies and risk metrics are also aligned to these same geographic regions. Descriptions of each of Generation’s five reportable segments are as follows: • Mid-Atlantic represents operations in the eastern half of PJM, which includes New Jersey, Maryland, Virginia, West Virginia, Delaware, the District of Columbia and parts of Pennsylvania and North Carolina. • Midwest represents operations in the western half of PJM and the United States footprint of MISO, excluding MISO’s Southern Region. • New York represents operations within ISO-NY. • ERCOT represents operations within Electric Reliability Council of Texas. • Other Power Regions: • New England represents the operations within ISO-NE. • South represents operations in the FRCC, MISO’s Southern Region, and the remaining portions of the SERC not included within MISO or PJM. • West represents operations in the WECC, which includes California ISO. • 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 electric business activities and allocate resources based on RNF. Generation believes that RNF is a useful measurement of operational performance. RNF is not a presentation defined under GAAP and may not be comparable to other companies’ presentations or deemed more useful than the GAAP information provided elsewhere in this report. Generation’s operating revenues include all sales to third parties and affiliated sales to the Utility Registrants. Purchased power costs include all costs associated with the procurement and supply of electricity including capacity, energy and ancillary services. Fuel expense includes the fuel costs for Generation’s owned generation and fuel costs associated with tolling agreements. The results of Generation's other business activities are not regularly reviewed by the CODM and are therefore not classified as operating segments or included in the regional reportable segment amounts. These activities include natural gas, as well as other miscellaneous business activities that are not significant to Generation's overall operating revenues or results of operations. Further, Generation’s unrealized mark-to-market gains and losses on economic hedging activities and its amortization of certain intangible assets and liabilities relating to commodity contracts recorded at fair value from mergers and acquisitions are also excluded from the regional reportable segment amounts. Exelon and Generation do not use a measure of total assets in making decisions regarding allocating resources to or assessing the performance of these reportable segments. During the first quarter of 2019, due to a change in economics in our New England region, Generation changed the way that information is reviewed by the CODM. The New England region is no longer regularly reviewed as a separate region by the CODM nor is it presented separately in any external information presented to third parties. Information for the New England region is reviewed by the CODM as part of Other Power Regions. Exelon and Generation retrospectively applied this change. An analysis and reconciliation of the Registrants’ reportable segment information to the respective information in the consolidated financial statements for the three and nine months ended September 30, 2019 and 2018 is as follows: Three Months Ended September 30, 2019 and 2018 Generation (a) ComEd PECO BGE PHI Other (b) Intersegment Exelon Operating revenues (c) : 2019 Competitive businesses electric revenues $ 4,314 $ — $ — $ — $ — $ — $ (275 ) $ 4,039 Competitive businesses natural gas revenues 265 — — — — — 1 266 Competitive businesses other revenues 195 — — — — — (1 ) 194 Rate-regulated electric revenues — 1,583 716 619 1,357 — (7 ) 4,268 Rate-regulated natural gas revenues — — 62 84 20 — (3 ) 163 Shared service and other revenues — — — — 3 474 (478 ) (1 ) Total operating revenues $ 4,774 $ 1,583 $ 778 $ 703 $ 1,380 $ 474 $ (763 ) $ 8,929 Generation (a) ComEd PECO BGE PHI Other (b) Intersegment Exelon 2018 Competitive businesses electric revenues $ 4,741 $ — $ — $ — $ — $ — $ (306 ) $ 4,435 Competitive businesses natural gas revenues 397 — — — — — — 397 Competitive businesses other revenues 140 — — — — — (1 ) 139 Rate-regulated electric revenues — 1,598 700 645 1,334 — (7 ) 4,270 Rate-regulated natural gas revenues — — 57 86 24 — (5 ) 162 Shared service and other revenues — — — — 3 458 (461 ) — Total operating revenues $ 5,278 $ 1,598 $ 757 $ 731 $ 1,361 $ 458 $ (780 ) $ 9,403 Intersegment revenues (d) : 2019 $ 275 $ 4 $ 1 $ 6 $ 4 $ 474 $ (764 ) $ — 2018 308 4 2 6 3 456 (779 ) — Depreciation and amortization: 2019 $ 407 $ 259 $ 83 $ 116 $ 193 $ 25 $ — $ 1,083 2018 468 237 75 110 192 23 — 1,105 Operating expenses: 2019 $ 4,274 $ 1,256 $ 595 $ 612 $ 1,124 $ 457 $ (759 ) $ 7,559 2018 4,961 1,275 603 628 1,116 459 (790 ) 8,252 Interest expense, net: 2019 $ 109 $ 91 $ 33 $ 31 $ 66 $ 79 $ — $ 409 2018 101 85 32 27 65 83 — 393 Income (loss) before income taxes: 2019 $ 501 $ 245 $ 154 $ 67 $ 203 $ (68 ) $ — $ 1,102 2018 389 245 124 81 191 (83 ) — 947 Income Taxes: 2019 $ 87 $ 45 $ 14 $ 12 $ 14 $ — $ — $ 172 2018 78 52 (2 ) 18 4 (13 ) — 137 Net income (loss): 2019 $ 244 $ 200 $ 140 $ 55 $ 189 $ (68 ) $ — $ 760 2018 300 193 126 63 187 (69 ) — 800 Capital Expenditures 2019 $ 392 $ 452 $ 228 $ 300 $ 308 $ 7 $ — $ 1,687 2018 362 514 204 233 359 18 — 1,690 __________ (a) Intersegment revenues for Generation in 2019 include revenue from sales to PECO of $43 million , sales to BGE of $65 million , sales to Pepco of $65 million , sales to DPL of $14 million and sales to ACE of $3 million in the Mid-Atlantic region, and sales to ComEd of $83 million in the Midwest region, which eliminate upon consolidation. Intersegment revenues for Generation in 2018 include revenue from sales to PECO of $35 million , sales to BGE of $69 million , sales to Pepco of $46 million , sales to DPL of $26 million and sales to ACE of $10 million in the Mid-Atlantic region, and sales to ComEd of $122 million in the Midwest region, which eliminate upon consolidation. (b) Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities. (c) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 17 — Supplemental Financial Information for additional information on total utility taxes. (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. PHI: Pepco DPL ACE Other (b) Intersegment PHI Operating revenues (a) : 2019 Rate-regulated electric revenues $ 642 $ 299 $ 419 $ — $ (3 ) $ 1,357 Rate-regulated natural gas revenues — 20 — — — 20 Shared service and other revenues — — — 92 (89 ) 3 Total operating revenues $ 642 $ 319 $ 419 $ 92 $ (92 ) $ 1,380 2018 Rate-regulated electric revenues $ 628 $ 304 $ 406 $ — $ (4 ) $ 1,334 Rate-regulated natural gas revenues — 24 — — — 24 Shared service and other revenues — — — 103 (100 ) 3 Total operating revenues $ 628 $ 328 $ 406 $ 103 $ (104 ) $ 1,361 Intersegment revenues: 2019 $ 2 $ 1 $ 1 $ 93 $ (93 ) $ 4 2018 2 2 1 103 (105 ) 3 Depreciation and amortization: 2019 $ 95 $ 46 $ 43 $ 9 $ — $ 193 2018 99 47 38 8 — 192 Operating expenses: 2019 $ 515 $ 268 $ 340 $ 95 $ (94 ) $ 1,124 2018 516 277 322 105 (104 ) 1,116 Interest expense, net: 2019 $ 33 $ 15 $ 15 $ 3 $ — $ 66 2018 32 15 16 2 — 65 Income (loss) before income taxes: 2019 $ 103 $ 38 $ 65 $ 192 $ (195 ) $ 203 2018 87 38 69 179 (182 ) 191 Income Taxes: 2019 $ 5 $ 5 $ 2 $ 3 $ (1 ) $ 14 2018 (2 ) 5 8 (8 ) 1 4 Net income (loss): 2019 $ 98 $ 33 $ 63 $ (9 ) $ 4 $ 189 2018 89 33 61 1 3 187 Capital Expenditures 2019 $ 157 $ 85 $ 73 $ (7 ) $ — $ 308 2018 188 88 77 6 — 359 __________ (a) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 17 — Supplemental Financial Information for additional information on total utility taxes. (b) Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities. The following tables disaggregate the Registrants' revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. For Generation, the disaggregation of revenues reflects Generation’s two primary products of power sales and natural gas sales, with further disaggregation of power sales provided by geographic region. For the Utility Registrants, the disaggregation of revenues reflects the two primary utility services of rate-regulated electric sales and rate-regulated natural gas sales (where applicable), with further disaggregation of these tariff sales provided by major customer groups. Exelon’s disaggregated revenues are consistent with Generation and the Utility Registrants, but exclude any intercompany revenues. Competitive Business Revenues (Generation): Three Months Ended September 30, 2019 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,351 $ 10 $ 1,361 $ 3 $ 1,364 Midwest 1,052 47 1,099 (17 ) 1,082 New York 414 15 429 — 429 ERCOT 288 72 360 5 365 Other Power Regions 873 192 1,065 (25 ) 1,040 Total Competitive Businesses Electric Revenues 3,978 336 4,314 (34 ) 4,280 Competitive Businesses Natural Gas Revenues 160 105 265 34 299 Competitive Businesses Other Revenues (c) 112 83 195 — 195 Total Generation Consolidated Operating Revenues $ 4,250 $ 524 $ 4,774 $ — $ 4,774 Three Months Ended September 30, 2018 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,397 $ 52 $ 1,449 $ 7 $ 1,456 Midwest 1,095 26 1,121 (4 ) 1,117 New York 475 (6 ) 469 — 469 ERCOT 156 289 445 (1 ) 444 Other Power Regions 959 298 1,257 (45 ) 1,212 Total Competitive Businesses Electric Revenues 4,082 659 4,741 (43 ) 4,698 Competitive Businesses Natural Gas Revenues 200 197 397 43 440 Competitive Businesses Other Revenues (c) 130 10 140 — 140 Total Generation Consolidated Operating Revenues $ 4,412 $ 866 $ 5,278 $ — $ 5,278 __________ (a) Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants. (b) Includes revenues from derivatives and leases. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Includes unrealized mark-to-market gains of $77 million and $6 million in 2019 and 2018 , respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 RNF (a) Intersegment RNF Total RNF RNF (a) Intersegment RNF Total RNF Mid-Atlantic $ 684 $ 5 $ 689 $ 746 $ 17 $ 763 Midwest 763 (16 ) 747 763 5 768 New York 288 3 291 290 2 292 ERCOT 76 (4 ) 72 161 (63 ) 98 Other Power Regions 212 (28 ) 184 226 (46 ) 180 Total Revenues net of purchased power and fuel for Reportable Segments 2,023 (40 ) 1,983 2,186 (85 ) 2,101 Other (b) 100 40 140 112 85 197 Total Generation Revenues net of purchased power and fuel expense $ 2,123 $ — $ 2,123 $ 2,298 $ — $ 2,298 __________ (a) Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allocated to a region. See text above for a description of included activities. Includes unrealized mark-to-market gains of $17 million and $71 million in 2019 and 2018 , respectively, accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 8 — Early Plant Retirements of $3 million and $18 million decrease to RNF in 2019 and 2018 , respectively, and the elimination of intersegment RNF. Electric and Gas Revenue by Customer Class (Utility Registrants): Three Months Ended September 30, 2019 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 865 $ 479 $ 352 $ 741 $ 311 $ 178 $ 252 Small commercial & industrial 393 109 64 147 41 48 58 Large commercial & industrial 141 63 116 297 222 26 49 Public authorities & electric railroads 12 9 7 17 11 3 3 Other (a) 222 63 82 164 58 50 56 Total rate-regulated electric revenues (b) $ 1,633 $ 723 $ 621 $ 1,366 $ 643 $ 305 $ 418 Rate-regulated natural gas revenues Residential $ — $ 38 $ 49 $ 9 $ — $ 9 $ — Small commercial & industrial — 17 9 4 — 4 — Large commercial & industrial — — 20 1 — 1 — Transportation — 5 — 4 — 4 — Other (c) — 2 5 2 — 2 — Total rate-regulated natural gas revenues (d) $ — $ 62 $ 83 $ 20 $ — $ 20 $ — Total rate-regulated revenues from contracts with customers $ 1,633 $ 785 $ 704 $ 1,386 $ 643 $ 325 $ 418 Other revenues Revenues from alternative revenue programs $ (56 ) $ (11 ) $ (5 ) $ (9 ) $ (3 ) $ (6 ) $ 1 Other rate-regulated electric revenues (e) 6 4 3 3 2 — — Other rate-regulated natural gas revenues (e) — — 1 — — — — Total other revenues $ (50 ) $ (7 ) $ (1 ) $ (6 ) $ (1 ) $ (6 ) $ 1 Total rate-regulated revenues for reportable segments $ 1,583 $ 778 $ 703 $ 1,380 $ 642 $ 319 $ 419 Three Months Ended September 30, 2018 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 861 $ 458 $ 366 $ 726 $ 306 $ 180 $ 240 Small commercial & industrial 391 108 68 140 39 48 53 Large commercial & industrial 131 64 117 303 230 25 48 Public authorities & electric railroads 11 7 7 14 8 3 3 Other (a) 212 59 91 156 47 47 63 Total rate-regulated electric revenues (b) $ 1,606 $ 696 $ 649 $ 1,339 $ 630 $ 303 $ 407 Rate-regulated natural gas revenues Residential $ — $ 36 $ 46 $ 8 $ — $ 8 $ — Small commercial & industrial — 15 8 5 — 5 — Large commercial & industrial — — 17 2 — 2 — Transportation — 5 — 3 — 3 — Other (c) — 1 12 6 — 6 — Total rate-regulated natural gas revenues (d) $ — $ 57 $ 83 $ 24 $ — $ 24 $ — Total rate-regulated revenues from contracts with customers $ 1,606 $ 753 $ 732 $ 1,363 $ 630 $ 327 $ 407 Other revenues Revenues from alternative revenue programs $ (15 ) $ 1 $ (6 ) $ (5 ) $ (4 ) $ — $ (1 ) Other rate-regulated electric revenues (e) 7 3 4 3 2 1 — Other rate-regulated natural gas revenues (e) — — 1 — — — — Total other revenues $ (8 ) $ 4 $ (1 ) $ (2 ) $ (2 ) $ 1 $ (1 ) Total rate-regulated revenues for reportable segments $ 1,598 $ 757 $ 731 $ 1,361 $ 628 $ 328 $ 406 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates of $4 million , $1 million , $2 million , $4 million , $2 million , $1 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, in 2019 and $4 million , $2 million , $1 million , $3 million $2 million , $2 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, in 2018 . (c) Includes revenues from off-system natural gas sales. (d) Includes operating revenues from affiliates of less than $1 million and $4 million at PECO and BGE, respectively, in 2019 and less than $1 million and $5 million at PECO and BGE, respectively, in 2018 . (e) Includes late payment charge revenues. Nine Months Ended September 30, 2019 and 2018 Generation (a) ComEd PECO BGE PHI Other (b) Intersegment Exelon Operating revenues (c) : 2019 Competitive businesses electric revenues $ 12,365 $ — $ — $ — $ — $ — $ (840 ) $ 11,525 Competitive businesses natural gas revenues 1,479 — — — — — — 1,479 Competitive businesses other revenues 436 — — — — — (4 ) 432 Rate-regulated electric revenues — 4,342 1,901 1,817 3,574 — (25 ) 11,609 Rate-regulated natural gas revenues — — 432 510 116 — (12 ) 1,046 Shared service and other revenues — — — — 10 1,410 (1,415 ) 5 Total operating revenues $ 14,280 $ 4,342 $ 2,333 $ 2,327 $ 3,700 $ 1,410 $ (2,296 ) $ 26,096 2018 Competitive businesses electric revenues $ 13,190 $ — $ — $ — $ — $ — $ (969 ) $ 12,221 Competitive businesses natural gas revenues 1,839 — — — — — (8 ) 1,831 Competitive businesses other revenues 339 — — — — — (4 ) 335 Rate-regulated electric revenues — 4,508 1,893 1,850 3,549 — (34 ) 11,766 Rate-regulated natural gas revenues — — 382 519 129 — (13 ) 1,017 Shared service and other revenues — — — — 10 1,398 (1,408 ) — Total operating revenues $ 15,368 $ 4,508 $ 2,275 $ 2,369 $ 3,688 $ 1,398 $ (2,436 ) $ 27,170 Shared service and other revenues Intersegment revenues (d) : 2019 $ 844 $ 13 $ 4 $ 18 $ 11 $ 1,410 $ (2,300 ) $ — 2018 981 23 5 18 11 1,392 (2,430 ) — Depreciation and amortization: 2019 $ 1,221 $ 767 $ 247 $ 368 $ 562 $ 72 $ — $ 3,237 2018 1,383 696 224 358 555 68 — 3,284 Operating expenses: 2019 $ 13,333 $ 3,431 $ 1,783 $ 1,936 $ 3,106 $ 1,405 $ (2,291 ) $ 22,703 2018 14,475 3,610 1,853 2,005 3,165 1,395 (2,467 ) 24,036 Interest expense, net: 2019 $ 336 $ 268 $ 100 $ 89 $ 197 $ 231 $ — $ 1,221 2018 305 261 96 78 193 205 — 1,138 Generation (a) ComEd PECO BGE PHI Other (b) Intersegment Exelon Income (loss) before income taxes: 2019 $ 1,355 $ 674 $ 461 $ 320 $ 436 $ (218 ) $ — $ 3,028 2018 800 663 331 301 363 (195 ) — 2,263 Income Taxes: 2019 $ 388 $ 130 $ 51 $ 59 $ 25 $ (27 ) $ — $ 626 2018 110 140 (5 ) 59 28 (70 ) — 262 Net income (loss): 2019 $ 784 $ 544 $ 410 $ 261 $ 412 $ (191 ) $ — $ 2,220 2018 667 523 336 242 336 (125 ) — 1,979 Capital Expenditures 2019 $ 1,282 $ 1,413 $ 675 $ 842 $ 1,006 $ 41 $ — $ 5,259 2018 1,660 1,540 615 667 988 27 — 5,497 Total assets: September 30, 2019 $ 47,984 $ 32,326 $ 11,379 $ 10,304 $ 22,576 $ 8,254 $ (10,085 ) $ 122,738 December 31, 2018 47,556 31,213 10,642 9,716 21,984 8,355 (9,800 ) 119,666 __________ (a) Intersegment revenues for Generation in 2019 include revenue from sales to PECO of $123 million , sales to BGE of $199 million , sales to Pepco of $188 million , sales to DPL of $50 million and sales to ACE of $16 million in the Mid-Atlantic region, and sales to ComEd of $266 million in the Midwest region, which eliminate upon consolidation. Intersegment revenues for Generation in 2018 include revenue from sales to PECO of $97 million , sales to BGE of $198 million , sales to Pepco of $143 million , sales to DPL of $103 million and sales to ACE of $21 million in the Mid-Atlantic region, and sales to ComEd of $419 million in the Midwest region, which eliminate upon consolidation. (b) Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities. (c) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 17 — Supplemental Financial Information for additional information on total utility taxes. (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. PHI: Pepco DPL ACE Other (b) Intersegment PHI Operating revenues (a) : 2019 Rate-regulated electric revenues $ 1,748 $ 871 $ 966 $ (1 ) $ (10 ) $ 3,574 Rate-regulated natural gas revenues — 116 — — — 116 Shared service and other revenues — — — 298 (288 ) 10 Total operating revenues $ 1,748 $ 987 $ 966 $ 297 $ (298 ) $ 3,700 2018 Rate-regulated electric revenues $ 1,708 $ 872 $ 981 $ — $ (12 ) $ 3,549 Rate-regulated natural gas revenues — 129 — — — 129 Shared service and other revenues — — — 326 (316 ) 10 Total operating revenues $ 1,708 $ 1,001 $ 981 $ 326 $ (328 ) $ 3,688 Intersegment revenues: 2019 $ 5 $ 5 $ 2 $ 297 $ (298 ) $ 11 2018 5 6 2 325 (327 ) 11 Depreciation and amortization: 2019 $ 281 $ 138 $ 114 $ 29 $ — $ 562 2018 286 135 107 27 — 555 Operating expenses: 2019 $ 1,444 $ 820 $ 838 $ 302 $ (298 ) $ 3,106 2018 1,454 859 847 329 (324 ) 3,165 Interest expense, net: 2019 $ 100 $ 45 $ 44 $ 8 $ — $ 197 2018 96 42 48 7 — 193 Income (loss) before income taxes: 2019 $ 226 $ 132 $ 89 $ 411 $ (422 ) $ 436 2018 181 107 88 326 (339 ) 363 Income Taxes: 2019 $ 9 $ 16 $ 2 $ (1 ) $ (1 ) $ 25 2018 7 17 12 (8 ) — 28 Net income (loss): 2019 $ 217 $ 116 $ 87 $ (19 ) $ 11 $ 412 2018 174 90 76 (15 ) 11 336 Capital Expenditures 2019 $ 455 $ 245 $ 300 $ 6 $ — $ 1,006 2018 475 254 247 12 — 988 Total assets: September 30, 2019 $ 8,603 $ 4,724 $ 3,916 $ 11,071 $ (5,738 ) $ 22,576 December 31, 2018 8,299 4,588 3,699 10,819 (5,421 ) 21,984 __________ (a) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 17 — Supplemental Financial Information for additional information on total utility taxes. (b) Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities. The following tables disaggregate the Registrants' revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. For Generation, the disaggregation of revenues reflects Generation’s two primary products of power sales and natural gas sales, with further disaggregation of power sales provided by geographic region. For the Utility Registrants, the disaggregation of revenues reflects the two primary utility services of rate-regulated electric sales and rate-regulated natural gas sales (where applicable), with further disaggregation of these tariff sales provided by major customer groups. Exelon’s disaggregated revenues are consistent with Generation and the Utility Registrants, but exclude any intercompany revenues. Competitive Business Revenues (Generation): Nine Months Ended September 30, 2019 Revenues from external customers (a) Intersegment Revenues Total Revenues Contracts with customers Other (b) Total Mid-Atlantic $ 3,798 $ 9 $ 3,807 $ 2 $ 3,809 Midwest 3,083 172 3,255 (31 ) 3,224 New York 1,195 16 1,211 — 1,211 ERCOT 594 198 792 13 805 Other Power Regions 2,849 451 3,300 (46 ) 3,254 Total Competitive Businesses Electric Revenues 11,519 846 12,365 (62 ) 12,303 Competitive Businesses Natural Gas Revenues 1,041 438 1,479 62 1,541 Competitive Businesses Other Revenues (c) 343 93 436 — 436 Total Generation Consolidated Operating Revenues $ 12,903 $ 1,377 $ 14,280 $ — $ 14,280 Nine Months Ended September 30, 2018 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 3,971 $ 191 $ 4,162 $ 17 $ 4,179 Midwest 3,432 169 3,601 (8 ) 3,593 New York 1,305 (37 ) 1,268 1 1,269 ERCOT 470 459 929 1 930 Other Power Regions 2,656 574 3,230 (116 ) 3,114 Total Competitive Businesses Electric Revenues 11,834 1,356 13,190 (105 ) 13,085 Competitive Businesses Natural Gas Revenues 1,016 823 1,839 105 1,944 Competitive Businesses Other Revenues (c) 385 (46 ) 339 — 339 Total Generation Consolidated Operating Revenues $ 13,235 $ 2,133 $ 15,368 $ — $ 15,368 __________ (a) Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants. (b) Includes revenues from derivatives and leases. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Includes unrealized mark-to-market gains of $64 million and losses of $96 million in 2019 and 2018 , respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 RNF from external customers (a) Intersegment RNF Total RNF RNF from external customers (a) Intersegment RNF Total RNF Mid-Atlantic $ 2,007 $ 16 $ 2,023 $ 2,303 $ 45 $ 2,348 Midwest 2,269 (22 ) 2,247 2,381 19 2,400 New York 800 10 810 832 9 841 ERCOT 252 (27 ) 225 396 (180 ) 216 Other Power Regions 542 (64 ) 478 740 (133 ) 607 Total Revenues net of purchased power and fuel expense for Reportable Segments 5,870 (87 ) 5,783 6,652 (240 ) 6,412 Other (b) 262 87 349 164 240 404 Total Generation Revenues net of purchased power and fuel expense $ 6,132 $ — $ 6,132 $ 6,816 $ — $ 6,816 __________ (a) Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allocated to a region. See text above for a description of included activities. Includes unrealized mark-to-market losses of $84 million and $104 million in 2019 and 2018 , respectively, accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 8 — Early Plant Retirements of $13 million and $53 million decrease to RNF in 2019 and 2018 , respectively, and the elimination of intersegment RNF. Electric and Gas Revenue by Customer Class (Utility Registrants): Nine Months Ended September 30, 2019 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 2,221 $ 1,231 $ 1,019 $ 1,816 $ 792 $ 499 $ 525 Small commercial & industrial 1,103 304 193 387 114 141 132 Large commercial & industrial 399 163 335 843 633 75 135 Public authorities & electric railroads 35 23 20 47 27 10 10 Other (a) 660 186 242 481 166 151 164 Total rate-regulated electric revenues (b) 4,418 1,907 1,809 3,574 1,732 876 966 Rate-regulated natural gas revenues Residential — 285 327 64 — 64 — Small commercial & industrial — 122 55 30 — 30 — Large commercial & industrial — 1 93 4 — 4 — Transportation — 18 — 11 — 11 — Other (c) — 5 19 6 — 6 — Total rate-regulated natural gas revenues (d) — 431 494 115 — 115 — Total rate-regulated revenues from contracts with customers 4,418 2,338 2,303 3,689 1,732 991 966 Other revenues Revenues from alternative revenue programs (98 ) (16 ) 11 4 10 (6 ) — Other rate-regulated electric revenues (e) 22 10 10 7 6 1 — Other rate-regulated natural gas revenues (e) — 1 3 — — 1 — Total other revenues (76 ) (5 ) 24 11 16 (4 ) — Total rate-regulated revenues for reportable segments $ 4,342 $ 2,333 $ 2,327 $ 3,700 $ 1,748 $ 987 $ 966 Nine Months Ended September 30, 2018 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 2,277 $ 1,199 $ 1,054 $ 1,839 $ 792 $ 513 $ 534 Small commercial & industrial 1,132 306 196 370 104 138 128 Large commercial & industrial 411 174 325 845 632 74 139 Public authorities & electric railroads 36 21 21 44 24 10 10 Other (a) 656 181 246 446 145 129 174 Total rate-regulated electric revenues (b) 4,512 1,881 1,842 3,544 1,697 864 985 Rate-regulated natural gas revenues Residential — 259 345 68 — 68 — Small commercial & industrial — 102 55 31 — 31 — Large commercial & industrial — 1 88 7 — 7 — Transportation — 16 — 12 — 12 — Other (c) — 4 49 11 — 11 — Total rate-regulated natural gas revenues (d) — 382 537 129 — 129 — Total rate-regulated revenues from contracts with customers 4,512 2,263 2,379 3,673 1,697 993 985 Other revenues Revenues from alternative revenue programs (27 ) 2 (23 ) 7 6 5 (4 ) Other rate-regulated electric revenues (e) 23 10 10 8 5 3 — Other rate-regulated natural gas revenues (e) — — 3 — — — — Total other revenues (4 ) 12 (10 ) 15 11 8 (4 ) Total rate-regulated revenues for reportable segments $ 4,508 $ 2,275 $ 2,369 $ 3,688 $ 1,708 $ 1,001 $ 981 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates of $13 million , $4 million , $5 million, $11 million , $5 million , $5 million and $2 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, in 2019 and $23 million , $5 million , $5 million , $11 million $5 million , $6 million and $2 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, in 2018 . (c) Includes revenues from off-system natural gas sales. (d) Includes operating revenues from affiliates of less than $1 million and $13 million at PECO and BGE in 2019 and 2018 , respectively. (e) Includes late payment charge revenues.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	Basis of Presentation (All Registrants) Each of the Registrant’s Consolidated Financial Statements includes the accounts of its subsidiaries. All intercompany transactions have been eliminated. Through its business services subsidiary, BSC, Exelon provides its subsidiaries with a variety of support services at cost, including legal, human resources, financial, information technology and supply management services. PHI also has a business services subsidiary, PHISCO, which provides a variety of support services at cost, including legal, accounting, engineering, customer operations, distribution and transmission planning, asset management, system operations, and power procurement, to PHI operating companies. The costs of BSC and PHISCO are directly charged or allocated to the applicable subsidiaries. The results of Exelon’s corporate operations are presented as “Other” within the consolidated financial statements and include intercompany eliminations unless otherwise disclosed. The accompanying consolidated financial statements as of September 30, 2019 and 2018 and for the three and nine months then ended are unaudited but, in the opinion of the management of each Registrant include all adjustments that are considered necessary for a fair statement of the Registrants’ respective financial statements in accordance with GAAP. All adjustments are of a normal, recurring nature, except as otherwise disclosed. The December 31, 2018 Consolidated Balance Sheets were derived 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, 2019 . 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.
New Accounting Pronouncements, Policy [Policy Text Block]	New Accounting Standards (All Registrants) New Accounting Standards Adopted in 2019: In 2019, the Registrants have adopted the following new authoritative accounting guidance issued by the FASB. Leases. The Registrants applied the new guidance with the following transition practical expedients: • a "package of three" expedients that must be taken together and allow entities to (1) not reassess whether existing contracts contain leases, (2) carry forward the existing lease classification, and (3) not reassess initial direct costs associated with existing leases, • an implementation expedient which allows the requirements of the standard in the period of adoption with no restatement of prior periods, and • a land easement expedient which allows entities to not evaluate land easements under the new standard at adoption if they were not previously accounted for as leases. The standard materially impacted the Registrants' Consolidated Balance Sheets but did not have a material impact in the Registrants' Consolidated Statements of Operations and Comprehensive Income, Consolidated Statements of Cash Flows and Consolidated Statements of Changes in Shareholders' Equity. The most significant impact was the recognition of the ROU assets and lease liabilities for operating leases. The operating ROU assets and lease liabilities recognized upon adoption are materially consistent with the balances presented in the Combined Notes to the Consolidated Financial Statements. See Note 5 - Leases for additional information. See Note 1 — Significant Accounting Policies of the Exelon 2018 Form 10-K for additional information on new accounting standards issued and adopted as of January 1, 2019. New Accounting Standards Issued and Not Yet Adopted as of September 30, 2019 : The following new authoritative accounting guidance issued by the FASB has not yet been adopted and reflected by the Registrants in their consolidated financial statements as of September 30, 2019 . Unless otherwise indicated, the Registrants are currently assessing the impacts such guidance may have (which could be material) in their financial statements. The Registrants have assessed other FASB issuances of new standards which are not listed below as the Registrants do not expect such standards to have a material impact to their financial statements. Goodwill Impairment (Issued January 2017). Simplifies the accounting for goodwill impairment by removing Step 2 of the current test, which requires calculation of a hypothetical purchase price allocation. Under the revised guidance, goodwill impairment will be measured as the amount by which a reporting unit’s carrying value exceeds its fair value, not to exceed the carrying amount of goodwill (currently Step 1 of the two-step impairment test). Entities will continue to have the option to perform a qualitative assessment to determine if a quantitative impairment test is necessary. Exelon, Generation, ComEd, PHI and DPL do not expect the updated guidance to have a material impact to their financial statements. The standard is effective January 1, 2020, with early adoption permitted, and must be applied on a prospective basis. Impairment of Financial Instruments (Issued June 2016). Provides for a new Current Expected Credit Loss (CECL) impairment model for specified financial instruments including loans, trade receivables, debt securities classified as held-to-maturity investments and net investments in leases recognized by a lessor. Under the new guidance, on initial recognition and at each reporting period, an entity is required to recognize an allowance that reflects its current estimate of credit losses expected to be incurred over the life of the financial instrument based on historical experience, current conditions and reasonable and supportable forecasts. The standard will be effective January 1, 2020 (with early adoption as of January 1, 2019 permitted) and requires a modified retrospective transition approach through a cumulative-effect adjustment to retained earnings as of the beginning of the period of adoption. This standard is primarily applicable to Generation's and the Utility Registrants' trade accounts receivable balances. The Registrants do not expect that this guidance will have a significant impact on their consolidated financial statements.
Revenues [Policy Text Block]	The Registrants recognize revenue from contracts with customers to depict the transfer of goods or services to customers at an amount that the entities expect to be entitled to in exchange for those goods or services. Generation’s primary sources of revenue include competitive sales of power, natural gas, and other energy-related products and services. The Utility Registrants’ primary sources of revenue include regulated electric and gas tariff sales, distribution and transmission services.
Lessee, Leases [Policy Text Block]	Leases (All Registrants) The Registrants recognize a ROU asset and lease liability for operating leases with a term of greater than one year. The ROU asset is included in Other deferred debits and other assets and the lease liability is included in Other current liabilities and Other deferred credits and other liabilities on the Consolidated Balance Sheets. The ROU asset is measured as the sum of (1) the present value of all remaining fixed and in-substance fixed payments using each Registrant’s incremental borrowing rate, (2) any lease payments made at or before the commencement date (less any lease incentives received) and (3) any initial direct costs incurred. The lease liability is measured the same as the ROU asset, but excludes any payments made before the commencement date and initial direct costs incurred. Lease terms include options to extend or terminate the lease if it is reasonably certain they will be exercised. The Registrants include non-lease components, which are service-related costs that are not integral to the use of the asset, in the measurement of the ROU asset and lease liability. Expense for operating leases and leases with a term of one year or less is recognized on a straight-line basis over the term of the lease, unless another systematic and rational basis is more representative of the derivation of benefit from use of the leased property. Variable lease payments are recognized in the period in which the related obligation is incurred and consist primarily of payments for purchases of electricity under contracted generation and are based on the electricity produced by those generating assets. Operating lease expense and variable lease payments are recorded to Purchased power and fuel expense for contracted generation or Operating and maintenance expense for all other lease agreements on the Registrants’ Statements of Operations and Comprehensive Income. Income from operating leases, including subleases, is recognized on a straight-line basis over the term of the lease, unless another systematic and rational basis is more representative of the pattern in which income is earned over the term of the lease. Variable lease payments are recognized in the period in which the related obligation is performed and consist primarily of payments received from sales of electricity under contracted generation and are based on the electricity produced by those generating assets. Operating lease income and variable lease payments are recorded to Operating revenues on the Registrants’ Statements of Operations and Comprehensive Income. The Registrants’ operating leases consist primarily of contracted generation, real estate including office buildings, and vehicles and equipment. The Registrants generally account for contracted generation in which the generating asset is not renewable as a lease if the customer has dispatch rights and obtains substantially all of the economic benefits. For new agreements entered after January 1, 2019, the Registrants will generally not account for contracted generation in which the generating asset is renewable as a lease if the customer does not design the generating asset. The Registrants account for land right arrangements that provide for exclusive use as leases while shared use land arrangements are generally not leases. The Registrants do not account for secondary use pole attachments as leases. See Note 5 — Leases for additional information.
Fair Value of Financial Instruments, Policy [Policy Text Block]	Valuation Techniques Used to Determine Net Asset Value Certain NDT Fund Investments are not classified within the fair value hierarchy and are included under the heading “Not subject to leveling” in the table above. These investments are measured at fair value using NAV per share as a practical expedient and include commingled funds, mutual funds which are not publicly quoted, managed middle market funds, private equity and real estate funds. For commingled funds and mutual funds, which are not publicly quoted, the fair value is primarily derived from the quoted prices in active markets on the underlying securities and can typically be redeemed monthly with 30 or less days of notice and without further restrictions. For managed middle market funds, the fair value is determined using a combination of valuation models including cost models, market models, and income models and typically cannot be redeemed until maturity of the term loan. Private equity and real estate investments include those in limited partnerships that invest in operating companies and real estate holding companies that are not publicly traded on a stock exchange, such as, leveraged buyouts, growth capital, venture capital, distressed investments, investments in natural resources, and direct investments in pools of real estate properties. These investments typically cannot be redeemed and are generally liquidated over a period of 8 to 10 years from the initial investment date, which is based on Exelon’s understanding of the investment funds. Private equity and real estate 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, market based comparable data, and independent appraisals from sources with professional qualifications. These valuation inputs are unobservable.

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
	Sep. 30, 2019
Variable Interest Entity [Abstract]
VIE - Assets and Liabilities of VIEs which Creditors or Beneficiaries have no Recourse [Table Text Block]	The table below shows the carrying amounts and classification of the consolidated VIEs’ assets and liabilities included in the consolidated financial statements of Exelon, Generation, PHI and ACE as of September 30, 2019 and December 31, 2018 . The assets, except as noted in the footnotes to the table below, can only be used to settle obligations of the VIEs. The liabilities, except as noted in the footnote to the table below, are such that creditors, or beneficiaries, do not have recourse to the general credit of Exelon, Generation, PHI and ACE. September 30, 2019 December 31, 2018 Exelon Generation PHI (a) ACE Exelon Generation PHI (a) ACE Cash and cash equivalents $ 168 $ 168 $ — $ — $ 414 $ 414 $ — $ — Restricted cash and cash equivalents 76 73 3 3 66 62 4 4 Accounts receivable, net Customer 163 163 — — 146 146 — — Other 43 43 — — 23 23 — — Unamortized energy contract asset (b) 23 23 — — 25 25 — — Inventory, net Materials and supplies 222 222 — — 212 212 — — Other current assets 50 48 2 — 52 49 3 — Total current assets 745 740 5 3 938 931 7 4 Property, plant and equipment, net (c) 6,079 6,079 — — 6,188 6,188 — — NDT funds 2,636 2,636 — — 2,351 2,351 — — Unamortized energy contract asset (b) 258 258 — — 274 274 — — Other noncurrent assets 69 52 17 15 258 232 26 19 Total noncurrent assets 9,042 9,025 17 15 9,071 9,045 26 19 Total assets $ 9,787 $ 9,765 $ 22 $ 18 $ 10,009 $ 9,976 $ 33 $ 23 Long-term debt due within one year $ 556 $ 535 $ 21 $ 19 $ 87 $ 66 $ 21 $ 18 Accounts payable 148 148 — — 96 96 — — Accrued expenses 58 57 1 1 73 72 1 1 Unamortized energy contract liabilities 10 10 — — 15 15 — — Other current liabilities 30 30 — — 3 3 — — Total current liabilities 802 780 22 20 274 252 22 19 Long-term debt 532 504 28 26 1,072 1,025 47 40 Asset retirement obligations (d) 2,103 2,103 — — 2,165 2,165 — — Unamortized energy contract liabilities 1 1 — — 1 1 — — Other noncurrent liabilities 84 84 — — 42 42 — — Total noncurrent liabilities 2,720 2,692 28 26 3,280 3,233 47 40 Total liabilities $ 3,522 $ 3,472 $ 50 $ 46 $ 3,554 $ 3,485 $ 69 $ 59 _________ (a) Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity. (b) These are unrestricted assets to Exelon and Generation. (c) Exelon’s and Generation’s balances include unrestricted assets of $41 million and $43 million as of September 30, 2019 and December 31, 2018 , respectively. (d) Exelon’s and Generation’s balances include liabilities with recourse of $5 million as of September 30, 2019 and December 31, 2018 .
VIE - Summary of Unconsolidated VIEs [Table Text Block]	The following table presents summary information about Exelon's and Generation’s unconsolidated VIE entities: September 30, 2019 December 31, 2018 Commercial Agreement VIEs Equity Investment VIEs Total Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 614 $ 453 $ 1,067 $ 597 $ 472 $ 1,069 Total liabilities (a) 36 224 260 37 222 259 Exelon's ownership interest in VIE (a) — 201 201 — 223 223 Other ownership interests in VIE (a) 587 28 615 560 27 587 Registrants’ maximum exposure to loss: Carrying amount of equity method investments — 12 12 — 223 223 _________ (a) These items represent amounts in the unconsolidated VIE balance sheets, not in Exelon’s or Generation’s Consolidated Balance Sheets. These items are included to provide information regarding the relative size of the unconsolidated VIEs.

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Contract with Customer, Asset and Liability [Table Text Block]	The following table provides a rollforward of the contract assets and liabilities reflected in Exelon's and Generation's Consolidated Balance Sheets from January 1, 2018 to September 30, 2019 : Contract Assets Contract Liabilities Exelon Generation Exelon Generation Balance as of January 1, 2018 $ 283 $ 283 $ 35 $ 35 Consideration received or due (146 ) (146 ) 179 465 Revenues recognized 50 50 (187 ) (458 ) Balance at December 31, 2018 187 187 27 42 Consideration received or due (109 ) (109 ) 65 198 Revenues recognized 92 92 (66 ) (192 ) Balance at September 30, 2019 170 170 26 48
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block]	The following table shows the amounts of future revenues expected to be recorded in each year for performance obligations that are unsatisfied or partially unsatisfied as of September 30, 2019 . This disclosure only includes contracts for which the total consideration is fixed and determinable at contract inception. The average contract term varies by customer type and commodity but ranges from one month to several years. This disclosure excludes Generation's power and gas sales contracts as they contain variable volumes and/or variable pricing. This disclosure also excludes the Utility Registrants' gas and electric tariff sales contracts and transmission revenue contracts as they generally have an original expected duration of one year or less and, therefore, do not contain any future, unsatisfied performance obligations to be included in this disclosure. 2019 2020 2021 2022 2023 and thereafter Total Exelon 156 341 142 74 244 957 Generation 215 442 197 89 244 1,187

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Components of Lease Cost [Table Text Block]	The components of lease costs for the three months ended September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Operating lease costs $ 97 $ 73 $ 1 $ — $ 8 $ 12 $ 3 $ 3 $ 2 Variable lease costs 79 74 — — 1 1 — — — Short-term lease costs 5 5 — — — — — — — Total lease costs (a) $ 181 $ 152 $ 1 $ — $ 9 $ 13 $ 3 $ 3 $ 2 __________ (a) Excludes $29 million , $28 million , $1 million and $1 million of sublease income recorded at Exelon, Generation, PHI and DPL, respectively The components of lease costs for the nine months ended September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Operating lease costs $ 252 $ 180 $ 2 $ 1 $ 25 $ 35 $ 9 $ 10 $ 5 Variable lease costs 229 214 1 — 1 5 2 2 1 Short-term lease costs 16 16 — — — — — — — Total lease costs (a) $ 497 $ 410 $ 3 $ 1 $ 26 $ 40 $ 11 $ 12 $ 6 __________ (a) Excludes $48 million , $42 million , $6 million and $6 million of sublease income recorded at Exelon, Generation, PHI and DPL, respectively. The weighted average remaining lease terms, in years, and discount rates for operating leases as of September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Remaining lease term 10.1 10.6 4.7 4.3 5.6 9.0 9.6 9.5 5.3 Discount rate 4.5 % 4.8 % 3.1 % 3.3 % 3.6 % 4.0 % 3.7 % 3.7 % 3.3 %
Supplemental Balance Sheet Information Related to Lessee Right-of-Use Assets and Lease Liabilities [Table Text Block]	The following table provides additional information regarding the presentation of operating lease ROU assets and lease liabilities within the Registrants’ Consolidated Balance Sheets as of September 30, 2019 : Exelon (a) Generation (a) ComEd PECO BGE PHI Pepco DPL ACE Operating lease ROU assets Other deferred debits and other assets $ 1,374 $ 926 $ 10 $ 2 $ 83 $ 304 $ 66 $ 75 $ 24 Operating lease liabilities Other current liabilities 242 170 3 — 32 35 8 11 5 Other deferred credits and other liabilities 1,355 949 8 1 50 279 60 74 19 Total operating lease liabilities $ 1,597 $ 1,119 $ 11 $ 1 $ 82 $ 314 $ 68 $ 85 $ 24 __________ (a) Exelon's and Generation's operating ROU assets and lease liabilities include $542 million and $703 million , respectively, related to contracted generation.
Lessee, Operating Lease, Liability, Maturity [Table Text Block]	Future minimum lease payments for operating leases as of September 30, 2019 were as follows: Year Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE 2019 $ 65 $ 50 $ 1 $ — $ 1 $ 11 $ 3 $ 2 $ 2 2020 289 203 3 1 34 45 10 13 5 2021 246 162 3 — 31 43 9 12 5 2022 179 113 2 — 16 42 9 12 4 2023 148 100 1 — — 41 8 11 4 Remaining years 1,123 837 2 — 19 197 43 53 6 Total 2,050 1,465 12 1 101 379 82 103 26 Interest 453 346 1 — 19 65 14 18 2 Total operating lease liabilities $ 1,597 $ 1,119 $ 11 $ 1 $ 82 $ 314 $ 68 $ 85 $ 24
Schedule of Future Minimum Lease Payments for Operating Leases [Table Text Block]	Future minimum lease payments for operating leases under the prior lease accounting guidance as of December 31, 2018 were as follows: Year Exelon (a)(b) Generation (a)(b) ComEd (a)(c) PECO (a)(c) BGE (a)(c)(d)(e) PHI (a) Pepco (a) DPL (a)(c) ACE (a) 2019 $ 140 $ 33 $ 7 $ 5 $ 35 $ 48 $ 11 $ 14 $ 7 2020 149 46 5 5 35 46 10 13 6 2021 143 46 4 5 33 43 9 12 5 2022 126 47 4 5 18 42 8 12 5 2023 97 46 3 5 3 39 8 10 4 Remaining years 723 545 — — 19 159 40 35 5 Total minimum future lease payments $ 1,378 $ 763 $ 23 $ 25 $ 143 $ 377 $ 86 $ 96 $ 32 __________ (a) Includes amounts related to shared use land arrangements. (b) Excludes Generation’s contingent operating lease payments associated with contracted generation. (c) Amounts related to certain real estate leases and railroad licenses effectively have indefinite payment periods. As a result, ComEd, PECO, BGE and DPL have excluded these payments from the remaining years as such amounts would not be meaningful. ComEd's, PECO’s, BGE’s and DPL's average annual obligation for these arrangements, included in each of the years 2019 - 2023, was $3 million , $5 million , $1 million and $1 million respectively. Also includes amounts related to shared use land arrangements. (d) Includes all future lease payments on a 99-year real estate lease that expires in 2106. (e) The BGE column above includes minimum future lease payments associated with a 6-year lease for the Baltimore City conduit system that became effective during the fourth quarter of 2016. BGE's total commitments under the lease agreement are $26 million , $28 million , $28 million and $14 million related to years 2019 - 2022, respectively.
Schedule of Supplemental Cash Flow Information Related to Leases [Table Text Block]	Cash paid for amounts included in the measurement of lease liabilities for the nine months ended September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Operating cash flows from operating leases $ 225 $ 156 $ 2 $ — $ 32 $ 29 $ 7 $ 6 $ 4 ROU assets obtained in exchange for lease obligations for the nine months ended September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Operating leases $ 70 $ 11 $ 6 $ — $ 1 $ 20 $ 7 $ 9 $ 4
Components of Operating Lease Income [Table Text Block]	The components of lease income for the three months ended September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Operating lease income $ 30 $ 29 $ — $ — $ — $ 1 $ — $ 1 $ — Variable lease income 80 80 — — — — — — — The components of lease income for the nine months ended September 30, 2019 were as follows: Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Operating lease income $ 48 $ 44 $ — $ — $ — $ 3 $ — $ 3 $ — Variable lease income 209 206 — — — 3 — 3 —
Lessor, Operating Lease, Payments to be Received, Maturity [Table Text Block]	Future minimum lease payments to be recovered under operating leases as of September 30, 2019 were as follows: Year Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE 2019 $ 4 $ 3 $ — $ — $ — $ 1 $ — $ 1 $ — 2020 51 46 — — — 4 — 3 — 2021 50 45 — — — 4 1 3 — 2022 50 45 — — — 5 — 4 — 2023 49 45 — — — 4 — 3 — Remaining years 314 271 1 3 1 38 — 38 — Total $ 518 $ 455 $ 1 $ 3 $ 1 $ 56 $ 1 $ 52 $ —

Regulatory Matters (Tables)

Regulatory Matters (Tables)	9 Months Ended
	Sep. 30, 2019
Regulated Operations [Abstract]
Public Utilities Distribution Rate Cases [Table Text Block]	The following tables show the completed and pending distribution base rate case proceedings in 2019. Completed Distribution Base Rate Case Proceedings Registrant/Jurisdiction Filing Date Requested Revenue Requirement (Decrease) Increase Approved Revenue Requirement (Decrease) Increase Approved ROE Approval Date Rate Effective Date ComEd - Illinois (Electric) April 16, 2018 $ (23 ) $ (24 ) 8.69% December 4, 2018 January 1, 2019 PECO - Pennsylvania (Electric) March 29, 2018 $ 82 $ 25 N/A (a) December 20, 2018 January 1, 2019 BGE - Maryland (Natural Gas) June 8, 2018 (amended October 12, 2018) $ 61 $ 43 9.8% January 4, 2019 January 4, 2019 ACE - New Jersey (Electric) August 21, 2018 (amended November 19, 2018) $ 122 (b) $ 70 (b) 9.6% March 13, 2019 April 1, 2019 Pepco - Maryland (Electric) January 15, 2019 (amended May 16, 2019) $ 27 $ 10 9.6% August 12, 2019 August 13, 2019 __________ (a) The PECO rate case proceeding was resolved through a settlement agreement, which did not specify an approved ROE. (b) Requested and approved increases are before New Jersey sales and use tax. Pending Distribution Base Rate Case Proceedings Registrant/Jurisdiction Filing Date Requested Revenue Requirement (Decrease) Increase Requested ROE Expected Approval Timing ComEd - Illinois (Electric) (a) April 8, 2019 $ (6 ) 8.91 % December 2019 BGE - Maryland (Electric) (b) May 24, 2019 (amended October 4, 2019) $ 74 10.3 % December 2019 BGE - Maryland (Natural Gas) (b) May 24, 2019 (amended October 4, 2019) $ 59 10.3 % December 2019 Pepco - District of Columbia (Electric) (c) May 30, 2019 (amended September 16, 2019) $ 160 10.3 % Fourth quarter of 2020 __________ (a) Reflects an increase of $57 million for the initial revenue requirement for 2019 and a decrease of $63 million related to the annual reconciliation for 2018. The revenue requirement for 2019 and annual reconciliation for 2018 provides for a weighted average debt and equity return on distribution rate base of 6.53% . See Note 4 — Regulatory Matters of the Exelon 2018 Form 10-K for additional information on ComEd's distribution formula rate filings. (b) On October 25, 2019, BGE filed a settlement agreement with the MDPSC. The settlement provides for an increase to BGE’s annual electric and natural gas distribution rates of $18 million and $45 million , respectively. (c) Reflects a three-year cumulative multi-year plan and total requested revenue requirement increases of $84 million , $40 million and $36 million for years 2020, 2021, and 2022, respectively, to recover capital investments made in 2018 and 2019 and planned capital investments from 2020 to 2022.
Public Utilities Transmission Rate Filings [Table Text Block]	For 2019, the following total increases/(decreases) were included in ComEd’s, BGE’s, Pepco's, DPL's and ACE's electric transmission formula rate filings: Registrant (a) Initial Revenue Requirement Increase (Decrease) Annual Reconciliation (Decrease) Increase Total Revenue Requirement Increase (Decrease) Allowed Return on Rate Base (c) Allowed ROE (d) ComEd $ 21 $ (16 ) $ 5 8.21 % 11.50 % BGE (10 ) (23 ) (19 ) (b) 7.35 % 10.50 % Pepco 15 11 26 7.75 % 10.50 % DPL 17 (1 ) 16 7.14 % 10.50 % ACE 11 (2 ) 9 7.79 % 10.50 % __________ (a) All rates are effective June 2019 , subject to review by the FERC and other parties, which is due by the fourth quarter of 2019 . (b) The change in BGE's transmission revenue requirement includes a FERC approved dedicated facilities charge of $14 million to recover the costs of providing transmission service to specifically designated load by BGE. (c) Represents the weighted average debt and equity return on transmission rate bases. (d) As part of the FERC-approved settlement of ComEd’s 2007 transmission rate case, the rate of return on common equity is 11.50% , inclusive of a 50-basis-point incentive adder for being a member of a RTO, and the common equity component of the ratio used to calculate the weighted average debt and equity return for the transmission formula rate is currently capped at 55% . As part of the FERC-approved settlement of the ROE complaint against BGE, Pepco, DPL and ACE, the rate of return on common equity is 10.50% , inclusive of a 50-basis-point incentive adder for being a member of a RTO.
Public Utilities Energy Efficiency Revenue [Table Text Block]	ComEd filed its annual energy efficiency formula rate update with the ICC on May 23, 2019. The filing establishes the revenue requirement used to set the rates that will take effect in January 2020 after the ICC’s review and approval. The revenue requirement requested is based on a reconciliation of the 2018 actual costs plus projected 2019 and 2020 expenditures. Registrant Initial Revenue Requirement Increase (Decrease) Annual Reconciliation Increase (Decrease) Total Revenue Requirement Increase (Decrease) Requested Return on Rate Base Requested ROE ComEd $ 53 $ (2 ) $ 51 (a) 6.53 % 8.91 % __________ (a) The requested revenue requirement increase provides for a weighted average debt and equity return on rate base of 6.53% inclusive of an allowed ROE of 8.91% . The ROE reflects the average rate on 30-year treasury notes plus 580 basis points. The ROE applicable to the 2018 reconciliation year is 10.91% and the return on rate base is 7.49% , which include the Performance Adjustment, which can either increase or decrease the ROE by up to a maximum of 200 basis points.
Public Utilities General Disclosures [Table Text Block]	The following table presents authorized amounts capitalized for ratemaking purposes related to earnings on shareholders’ investment that are not recognized for financial reporting purposes in Exelon's and the Utility Registrant's Consolidated Balance Sheets. These amounts will be recognized as revenues in the related Consolidated Statements of Operations and Comprehensive Income in the periods they are billable to our customers. Exelon ComEd (a) PECO BGE (b) PHI Pepco (c) DPL (c) ACE September 30, 2019 $ 59 $ 4 $ — $ 47 $ 8 $ 5 $ 3 $ — December 31, 2018 $ 65 $ 8 $ — $ 49 $ 8 $ 5 $ 3 $ — _________ (a) Reflects ComEd's unrecognized equity returns earned for ratemaking purposes on its electric distribution formula rate regulatory assets. (b) BGE's authorized amounts capitalized for ratemaking purposes primarily relate to earnings on shareholders' investment on its AMI programs. (c) Pepco's and DPL's authorized amounts capitalized for ratemaking purposes relate to earnings on shareholders' investment on their respective AMI Programs and Energy Efficiency and Demand Response Programs. The earnings on energy efficiency are on Pepco DC and DPL DE programs only.

Early Plant Retirements (Tables

Early Plant Retirements (Tables)	9 Months Ended
	Sep. 30, 2019
Property, Plant and Equipment [Abstract]
Income statement expense (pre-tax)	As a result of these early nuclear plant retirement decisions, Exelon and Generation recognized incremental non-cash charges to earnings stemming from shortening the expected economic useful lives primarily related to accelerated depreciation of plant assets (including any ARC) and accelerated amortization of nuclear fuel, as well as operating and maintenance expenses. See Note 13 — Nuclear Decommissioning for additional information on changes to the nuclear decommissioning ARO balance. The total impact for the three and nine months ended September 30, 2019 and 2018 are summarized in the table below. Three Months Ended September 30, Nine Months Ended September 30, Income statement expense (pre-tax) 2019 2018 2019 2018 Depreciation and amortization (a) Accelerated depreciation $ 71 $ 152 $ 216 $ 441 Accelerated nuclear fuel amortization 3 18 13 52 Operating and maintenance (b) 39 4 (44 ) 32 Total $ 113 $ 174 $ 185 $ 525 _________ (a) Reflects incremental accelerated depreciation and amortization for TMI for the three and nine months ended September 30, 2019 . Reflects incremental accelerated depreciation for TMI and Oyster Creek for the three and nine months ended September 30, 2018 . The Oyster Creek amounts are from February 2, 2018 through September 17, 2018. The TMI amounts are through September 20, 2019. (b) In 2019, primarily reflects the net impacts associated with the remeasurements of the TMI ARO in the first and third quarters. See Note 13 — Nuclear Decommissioning for additional information on the first quarter 2019 TMI ARO update. In 2018, primarily reflects materials and supplies inventory reserve adjustments, employee related costs and CWIP impairments associated with the early retirement decisions for TMI and Oyster Creek. Excludes the charges in the third quarter of 2018 and second quarter of 2019 to Operating and maintenance expense for the ARO remeasurement due to the sale of Oyster Creek. See Note 3 — Mergers, Acquisitions and Dispositions for additional information.
Implications of Potential Early Plant Retirement on Balance Sheet [Table Text Block]	The following table provides the balance sheet amounts as of September 30, 2019 for Exelon's and Generation’s significant assets and liabilities associated with the Mystic Units 8 and 9 and Everett Marine Terminal assets that would potentially be impacted by the failure to adopt long-term solutions for reliability and fuel security. September 30, 2019 Asset Balances Materials and supplies inventory $ 31 Fuel inventory 5 Completed plant, net 889 Construction work in progress 7 Liability Balances Asset retirement obligation (2 )

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Liabilities Recorded at Amortized Cost	Fair Value of Financial Liabilities Recorded at Amortized Cost The following tables present the carrying amounts and fair values of the Registrants’ short-term liabilities, long-term debt, SNF obligation and trust preferred securities (long-term debt to financing trusts or junior subordinated debentures) as of September 30, 2019 and December 31, 2018 . The Registrants have no financial liabilities classified as Level 1. The carrying amounts of the Registrants’ short-term liabilities as presented on their Consolidated Balance Sheets are representative of their fair value (Level 2) because of the short-term nature of these instruments. September 30, 2019 December 31, 2018 Carrying Amount Fair Value Carrying Amount Fair Value Level 2 Level 3 Total Level 2 Level 3 Total Long-Term Debt, including amounts due within one year (a) Exelon $ 36,304 $ 38,056 $ 2,541 $ 40,597 $ 35,424 $ 33,711 $ 2,158 $ 35,869 Generation 8,613 7,962 1,398 9,360 8,793 7,467 1,443 8,910 ComEd 8,196 9,622 — 9,622 8,101 8,390 — 8,390 PECO 3,404 3,891 50 3,941 3,084 3,157 50 3,207 BGE 3,270 3,678 — 3,678 2,876 2,950 — 2,950 PHI 6,494 5,993 1,093 7,086 6,259 5,436 665 6,101 Pepco 2,860 3,249 395 3,644 2,719 2,901 196 3,097 DPL 1,495 1,437 232 1,669 1,494 1,303 193 1,496 ACE 1,324 1,034 466 1,500 1,188 987 275 1,262 Long-Term Debt to Financing Trusts (a) Exelon $ 390 $ — $ 426 $ 426 $ 390 $ — $ 400 $ 400 ComEd 205 — 223 223 205 — 209 209 PECO 184 — 203 203 184 — 191 191 SNF Obligation Exelon $ 1,193 $ 1,017 $ — $ 1,017 $ 1,171 $ 949 $ — $ 949 Generation 1,193 1,017 — 1,017 1,171 949 — 949 ____ (a) Includes unamortized debt issuance costs which are not fair valued.
Assets and liabilities measured and recorded at fair value on recurring basis	Recurring Fair Value Measurements The following tables present assets and liabilities measured and recorded at fair value in the Registrants' Consolidated Balance Sheets on a recurring basis and their level within the fair value hierarchy as of September 30, 2019 and December 31, 2018 : Exelon and Generation Exelon Generation As of September 30, 2019 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 1,719 $ — $ — $ — $ 1,719 $ 896 $ — $ — $ — $ 896 NDT fund investments Cash equivalents (b) 315 78 — — 393 315 78 — — 393 Equities 3,121 1,727 — 1,314 6,162 3,121 1,727 — 1,314 6,162 Fixed income Corporate debt — 1,473 259 — 1,732 — 1,473 259 — 1,732 U.S. Treasury and agencies 1,777 152 — — 1,929 1,777 152 — — 1,929 Foreign governments — 56 — — 56 — 56 — — 56 State and municipal debt — 85 — — 85 — 85 — — 85 Other (c) — 23 — 979 1,002 — 23 — 979 1,002 Exelon Generation As of September 30, 2019 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Fixed income subtotal 1,777 1,789 259 979 4,804 1,777 1,789 259 979 4,804 Middle market lending — — 255 445 700 — — 255 445 700 Private equity — — — 398 398 — — — 398 398 Real estate — — — 581 581 — — — 581 581 NDT fund investments subtotal (d) 5,213 3,594 514 3,717 13,038 5,213 3,594 514 3,717 13,038 Rabbi trust investments Cash equivalents 49 — — — 49 4 — — — 4 Mutual funds 77 — — — 77 24 — — — 24 Fixed income — 13 — — 13 — — — — — Life insurance contracts — 76 40 — 116 — 24 — — 24 Rabbi trust investments subtotal 126 89 40 — 255 28 24 — — 52 Commodity derivative assets Economic hedges 533 1,488 1,817 — 3,838 533 1,488 1,817 — 3,838 Proprietary trading — 54 156 — 210 — 54 156 — 210 Effect of netting and allocation of collateral (e)(f) (677 ) (1,261 ) (1,025 ) — (2,963 ) (677 ) (1,261 ) (1,025 ) — (2,963 ) Commodity derivative assets subtotal (144 ) 281 948 — 1,085 (144 ) 281 948 — 1,085 Total assets 6,914 3,964 1,502 3,717 16,097 5,993 3,899 1,462 3,717 15,071 Liabilities Commodity derivative liabilities Economic hedges (773 ) (1,695 ) (1,686 ) — (4,154 ) (773 ) (1,695 ) (1,406 ) — (3,874 ) Proprietary trading — (59 ) (89 ) — (148 ) — (59 ) (89 ) — (148 ) Effect of netting and allocation of collateral (e)(f) 770 1,585 1,329 — 3,684 770 1,585 1,329 — 3,684 Commodity derivative liabilities subtotal (3 ) (169 ) (446 ) — (618 ) (3 ) (169 ) (166 ) — (338 ) Deferred compensation obligation — (140 ) — — (140 ) — (37 ) — — (37 ) Total liabilities (3 ) (309 ) (446 ) — (758 ) (3 ) (206 ) (166 ) — (375 ) Total net assets $ 6,911 $ 3,655 $ 1,056 $ 3,717 $ 15,339 $ 5,990 $ 3,693 $ 1,296 $ 3,717 $ 14,696 Exelon Generation As of December 31, 2018 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Assets Cash equivalents (a) $ 1,243 $ — $ — $ — $ 1,243 $ 581 $ — $ — $ — $ 581 NDT fund investments Cash equivalents (b) 252 86 — — 338 252 86 — — 338 Equities 2,918 1,591 — 1,381 5,890 2,918 1,591 — 1,381 5,890 Fixed income Corporate debt — 1,593 230 — 1,823 — 1,593 230 — 1,823 U.S. Treasury and agencies 2,081 99 — — 2,180 2,081 99 — — 2,180 Foreign governments — 50 — — 50 — 50 — — 50 State and municipal debt — 149 — — 149 — 149 — — 149 Other (c) — 30 — 846 876 — 30 — 846 876 Fixed income subtotal 2,081 1,921 230 846 5,078 2,081 1,921 230 846 5,078 Middle market lending — — 313 367 680 — — 313 367 680 Private equity — — — 329 329 — — — 329 329 Real estate — — — 510 510 — — — 510 510 NDT fund investments subtotal (d) 5,251 3,598 543 3,433 12,825 5,251 3,598 543 3,433 12,825 Rabbi trust investments Cash equivalents 48 — — — 48 5 — — — 5 Mutual funds 72 — — — 72 24 — — — 24 Fixed income — 15 — — 15 — — — — — Life insurance contracts — 70 38 — 108 — 22 — — 22 Rabbi trust investments subtotal 120 85 38 — 243 29 22 — — 51 Commodity derivative assets Economic hedges 541 2,760 1,470 — 4,771 541 2,760 1,470 — 4,771 Proprietary trading — 69 77 — 146 — 69 77 — 146 Effect of netting and allocation of collateral (e)(f) (582 ) (2,357 ) (732 ) — (3,671 ) (582 ) (2,357 ) (732 ) — (3,671 ) Commodity derivative assets subtotal (41 ) 472 815 — 1,246 (41 ) 472 815 — 1,246 Total assets 6,573 4,155 1,396 3,433 15,557 5,820 4,092 1,358 3,433 14,703 Exelon Generation As of December 31, 2018 Level 1 Level 2 Level 3 Not subject to leveling Total Level 1 Level 2 Level 3 Not subject to leveling Total Liabilities Commodity derivative liabilities Economic hedges (642 ) (2,963 ) (1,276 ) — (4,881 ) (642 ) (2,963 ) (1,027 ) — (4,632 ) Proprietary trading — (73 ) (21 ) — (94 ) — (73 ) (21 ) — (94 ) Effect of netting and allocation of collateral (e)(f) 639 2,581 808 — 4,028 639 2,581 808 — 4,028 Commodity derivative liabilities subtotal (3 ) (455 ) (489 ) — (947 ) (3 ) (455 ) (240 ) — (698 ) Deferred compensation obligation — (137 ) — — (137 ) — (35 ) — — (35 ) Total liabilities (3 ) (592 ) (489 ) — (1,084 ) (3 ) (490 ) (240 ) — (733 ) Total net assets $ 6,570 $ 3,563 $ 907 $ 3,433 $ 14,473 $ 5,817 $ 3,602 $ 1,118 $ 3,433 $ 13,970 _________ (a) Exelon excludes cash of $347 million and $458 million at September 30, 2019 and December 31, 2018 , respectively, and restricted cash of $112 million and $80 million at September 30, 2019 and December 31, 2018 , respectively, and includes long-term restricted cash of $186 million and $185 million at September 30, 2019 and December 31, 2018 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Generation excludes cash of $183 million and $283 million at September 30, 2019 and December 31, 2018 , respectively, and restricted cash of $66 million and $39 million at September 30, 2019 and December 31, 2018 , respectively. (b) Includes $85 million and $50 million of cash received from outstanding repurchase agreements at September 30, 2019 and December 31, 2018 , respectively, and is offset by an obligation to repay upon settlement of the agreement as discussed in (d) below. (c) Includes a derivative liability of $2 million and a derivative asset of $44 million , which have total notional amounts of $864 million and $1,432 million at September 30, 2019 and December 31, 2018 , respectively. The notional principal amounts for these instruments provide one measure of the transaction volume outstanding as of the fiscal years ended and do not represent the amount of Exelon and Generation's exposure to credit or market loss. (d) Excludes net liabilities of $176 million and $130 million at September 30, 2019 and December 31, 2018 , respectively. These items consist of receivables related to pending securities sales, interest and dividend receivables, repurchase agreement obligations, and payables related to pending securities purchases. The repurchase agreements are generally short-term in nature with durations generally of 30 days or less. (e) Collateral posted/(received) from counterparties totaled $93 million , $324 million and $304 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of September 30, 2019 . Collateral posted/(received) from counterparties, net of collateral paid to counterparties, totaled $57 million , $224 million and $76 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2018 . (f) Of the collateral posted/(received), $306 million and $(94) million represents variation margin on the exchanges as of September 30, 2019 and December 31, 2018 , respectively. As of September 30, 2019 , Exelon and Generation have outstanding commitments to invest in fixed income, middle market lending, private equity and real estate investments of approximately $93 million , $241 million , $383 million , and $388 million , respectively. These commitments will be funded by Generation’s existing NDT funds. Exelon and Generation hold investments without readily determinable fair values with carrying amounts of $75 million as of September 30, 2019 . Changes were immaterial in fair value, cumulative adjustments and impairments for the three and nine months ended September 30, 2019 . Valuation Techniques Used to Determine Net Asset Value Certain NDT Fund Investments are not classified within the fair value hierarchy and are included under the heading “Not subject to leveling” in the table above. These investments are measured at fair value using NAV per share as a practical expedient and include commingled funds, mutual funds which are not publicly quoted, managed middle market funds, private equity and real estate funds. For commingled funds and mutual funds, which are not publicly quoted, the fair value is primarily derived from the quoted prices in active markets on the underlying securities and can typically be redeemed monthly with 30 or less days of notice and without further restrictions. For managed middle market funds, the fair value is determined using a combination of valuation models including cost models, market models, and income models and typically cannot be redeemed until maturity of the term loan. Private equity and real estate investments include those in limited partnerships that invest in operating companies and real estate holding companies that are not publicly traded on a stock exchange, such as, leveraged buyouts, growth capital, venture capital, distressed investments, investments in natural resources, and direct investments in pools of real estate properties. These investments typically cannot be redeemed and are generally liquidated over a period of 8 to 10 years from the initial investment date, which is based on Exelon’s understanding of the investment funds. Private equity and real estate 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, market based comparable data, and independent appraisals from sources with professional qualifications. These valuation inputs are unobservable. ComEd, PECO and BGE ComEd PECO BGE As of September 30, 2019 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 264 $ — $ — $ 264 $ 207 $ — $ — $ 207 $ 122 $ — $ — $ 122 Rabbi trust investments Mutual funds — — — — 8 — — 8 7 — — 7 Life insurance contracts — — — — — 11 — 11 — — — — Rabbi trust investments subtotal — — — — 8 11 — 19 7 — — 7 Total assets 264 — — 264 215 11 — 226 129 — — 129 Liabilities Deferred compensation obligation — (7 ) — (7 ) — (8 ) — (8 ) — (5 ) — (5 ) Mark-to-market derivative liabilities (b) — — (280 ) (280 ) — — — — — — — — Total liabilities — (7 ) (280 ) (287 ) — (8 ) — (8 ) — (5 ) — (5 ) Total net assets (liabilities) $ 264 $ (7 ) $ (280 ) $ (23 ) $ 215 $ 3 $ — $ 218 $ 129 $ (5 ) $ — $ 124 ComEd PECO BGE As of December 31, 2018 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 209 $ — $ — $ 209 $ 111 $ — $ — $ 111 $ 4 $ — $ — $ 4 Rabbi trust investments Mutual funds — — — — 7 — — 7 6 — — 6 Life insurance contracts — — — — — 10 — 10 — — — — Rabbi trust investments subtotal — — — — 7 10 — 17 6 — — 6 Total assets 209 — — 209 118 10 — 128 10 — — 10 Liabilities Deferred compensation obligation — (6 ) — (6 ) — (10 ) — (10 ) — (5 ) — (5 ) Mark-to-market derivative liabilities (b) — — (249 ) (249 ) — — — — — — — — Total liabilities — (6 ) (249 ) (255 ) — (10 ) — (10 ) — (5 ) — (5 ) Total net assets (liabilities) $ 209 $ (6 ) $ (249 ) $ (46 ) $ 118 $ — $ — $ 118 $ 10 $ (5 ) $ — $ 5 _________ (a) ComEd excludes cash of $76 million and $93 million at September 30, 2019 and December 31, 2018 , respectively, and restricted cash of $31 million and $28 million at September 30, 2019 and December 31, 2018 , respectively, and includes long-term restricted cash of $171 million and $166 million at September 30, 2019 and December 31, 2018 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. PECO excludes cash of $23 million and $24 million at September 30, 2019 and December 31, 2018 , respectively. BGE excludes cash of $8 million and $7 million at September 30, 2019 and December 31, 2018 , respectively, and restricted cash of $1 million and $2 million at September 30, 2019 and December 31, 2018 , respectively. (b) The Level 3 balance consists of the current and noncurrent liability of $27 million and $253 million , respectively, at September 30, 2019 , and $26 million and $223 million , respectively, at December 31, 2018 , related to floating-to-fixed energy swap contracts with unaffiliated suppliers. PHI, Pepco, DPL and ACE As of September 30, 2019 As of December 31, 2018 PHI Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 107 $ — $ — $ 107 $ 147 $ — $ — $ 147 Rabbi trust investments Cash equivalents 43 — — 43 42 — — 42 Mutual funds 13 — — 13 13 — — 13 Fixed income — 13 — 13 — 15 — 15 Life insurance contracts — 24 40 64 — 22 38 60 Rabbi trust investments subtotal 56 37 40 133 55 37 38 130 Total assets 163 37 40 240 202 37 38 277 Liabilities Deferred compensation obligation — (19 ) — (19 ) — (21 ) — (21 ) Total liabilities — (19 ) — (19 ) — (21 ) — (21 ) Total net assets $ 163 $ 18 $ 40 $ 221 $ 202 $ 16 $ 38 $ 256 Pepco DPL ACE As of September 30, 2019 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 34 $ — $ — $ 34 $ — $ — $ — $ — $ 18 $ — $ — $ 18 Rabbi trust investments Cash equivalents 43 — — 43 — — — — — — — — Fixed income — 3 — 3 — — — — — — — — Life insurance contracts — 24 40 64 — — — — — — — — Rabbi trust investments subtotal 43 27 40 110 — — — — — — — — Total assets 77 27 40 144 — — — — 18 — — 18 Liabilities Deferred compensation obligation — (2 ) — (2 ) — — — — — — — — Total liabilities — (2 ) — (2 ) — — — — — — — — Total net assets $ 77 $ 25 $ 40 $ 142 $ — $ — $ — $ — $ 18 $ — $ — $ 18 Pepco DPL ACE As of December 31, 2018 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 38 $ — $ — $ 38 $ 16 $ — $ — $ 16 $ 23 $ — $ — $ 23 Rabbi trust investments Cash equivalents 41 — — 41 — — — — — — — — Fixed income — 5 — 5 — — — — — — — — Life insurance contracts — 22 37 59 — — — — — — — — Rabbi trust investments subtotal 41 27 37 105 — — — — — — — — Total assets 79 27 37 143 16 — — 16 23 — — 23 Liabilities Deferred compensation obligation — (3 ) — (3 ) — (1 ) — (1 ) — — — — Total liabilities — (3 ) — (3 ) — (1 ) — (1 ) — — — — Total net assets (liabilities) $ 79 $ 24 $ 37 $ 140 $ 16 $ (1 ) $ — $ 15 $ 23 $ — $ — $ 23 _________ (a) PHI excludes cash of $45 million and $39 million at September 30, 2019 and December 31, 2018 , respectively, and includes long-term restricted cash of $15 million and $19 million at September 30, 2019 and December 31, 2018 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Pepco excludes cash of $18 million and $15 million at September 30, 2019 and December 31, 2018 , respectively. DPL excludes cash of $11 million and $8 million at September 30, 2019 and December 31, 2018 , respectively. ACE excludes cash of $13 million and $7 million at September 30, 2019 and December 31, 2018 , respectively, and includes long-term restricted cash of $15 million and $19 million at September 30, 2019 and December 31, 2018 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets.
Fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis	The following tables present the fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2019 and 2018 : Exelon Generation ComEd PHI and Pepco Three Months Ended September 30, 2019 Total NDT Fund Investments Mark-to-Market Derivatives Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Balance as of June 30, 2019 $ 1,179 $ 539 $ 873 $ 1,412 $ (273 ) $ 40 $ — Total realized / unrealized gains (losses) Included in net income (171 ) 2 (173 ) (a) (171 ) — — — Included in noncurrent payables to affiliates — 11 — 11 — — (11 ) Included in regulatory assets/liabilities 4 — — — (7 ) (b) — 11 Change in collateral 41 — 41 41 — — — Purchases, sales, issuances and settlements Purchases 53 1 52 53 — — — Sales (22 ) (21 ) (1 ) (22 ) — — — Settlements (18 ) (18 ) — (18 ) — — — Transfers into Level 3 1 — 1 (c) 1 — — — Transfers out of Level 3 (11 ) — (11 ) (c) (11 ) — — — Balance at September 30, 2019 $ 1,056 $ 514 $ 782 $ 1,296 $ (280 ) $ 40 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2019 $ (18 ) $ 2 $ (20 ) $ (18 ) $ — $ — $ — Exelon Generation ComEd PHI and Pepco Nine Months Ended September 30, 2019 Total NDT Fund Investments Mark-to-Market Derivatives Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Balance as of December 31, 2018 $ 907 $ 543 $ 575 $ 1,118 $ (249 ) $ 38 $ — Total realized / unrealized gains (losses) Included in net income (125 ) 5 (132 ) (a) (127 ) — 2 — Included in noncurrent payables to affiliates — 32 — 32 — — (32 ) Included in regulatory assets 1 — — — (31 ) (b) — 32 Change in collateral 227 — 227 227 — — — Purchases, sales, issuances and settlements Purchases 163 43 120 163 — — — Sales (23 ) (21 ) (2 ) (23 ) — — — Settlements (88 ) (88 ) — (88 ) — — — Transfers into Level 3 5 — 5 (c) 5 — — — Transfers out of Level 3 (11 ) — (11 ) (c) (11 ) — — — Balance as of September 30, 2019 $ 1,056 $ 514 $ 782 $ 1,296 $ (280 ) $ 40 $ — The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2019 $ 173 $ 5 $ 166 $ 171 $ — $ 2 $ — __________ (a) Includes a reduction for the reclassification of $153 million and $298 million of realized gains due to the settlement of derivative contracts for the three and nine months ended September 30, 2019 , respectively. (b) Includes $7 million of decreases in fair value and an increase for 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 September 30, 2019 . Includes $31 million of decreases in fair value and an increase for realized losses due to settlements of $17 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the nine months ended September 30, 2019 . (c) Transfers into and out of Level 3 generally occur when the contract tenor becomes less and more observable respectively, primarily due to changes in market liquidity or assumptions for certain commodity contracts. Exelon Generation ComEd PHI and Pepco Three Months Ended September 30, 2018 Total NDT Fund Investments Mark-to-Market Derivatives Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Balance as of June 30, 2018 $ 1,106 $ 585 $ 737 $ 1,322 $ (252 ) $ 36 $ — Total realized / unrealized gains (losses) Included in net income (259 ) (1 ) (259 ) (a) (260 ) — 1 — Included in noncurrent payables to affiliates — (4 ) — (4 ) — — 4 Included in regulatory assets (11 ) — — — (7 ) (b) — (4 ) Change in collateral (44 ) — (44 ) (44 ) — — — Purchases, sales, issuances and settlements Purchases 96 15 81 96 — — — Settlements (29 ) (29 ) — (29 ) — — — Transfers into Level 3 3 — 3 (c) 3 — — — Transfers out of Level 3 (6 ) — (6 ) (c) (6 ) — — — Balance as of September 30, 2018 $ 856 $ 566 $ 512 $ 1,078 $ (259 ) $ 37 $ — The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2018 $ (105 ) $ (1 ) $ (104 ) $ (105 ) $ — $ — $ — Exelon Generation ComEd PHI and Pepco Nine Months Ended September 30, 2018 Total NDT Fund Investments Mark-to-Market Derivatives Total Generation Mark-to-Market Derivatives Life Insurance Contracts Eliminated in Consolidation Balance as of December 31, 2017 $ 966 $ 648 $ 552 $ 1,200 $ (256 ) $ 22 $ — Total realized / unrealized gains (losses) Included in net income (186 ) (1 ) (188 ) (a) (189 ) — 3 — Included in regulatory assets (3 ) — — — (3 ) (b) — — Change in collateral 14 — 14 14 — — — Purchases, sales, issuances and settlements Purchases 215 34 181 215 — — — Sales (3 ) — (3 ) (3 ) — — — Settlements (103 ) (115 ) — (115 ) — 12 — Transfers into Level 3 (21 ) — (21 ) (c) (21 ) — — — Transfers out of Level 3 (23 ) — (23 ) (c) (23 ) — — — Balance as of September 30, 2018 $ 856 $ 566 $ 512 $ 1,078 $ (259 ) $ 37 $ — The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2018 $ 154 $ (5 ) $ 159 $ 154 $ — $ — $ — __________ (a) Includes a reduction for the reclassification of $155 million and $347 million of realized losses due to the settlement of derivative contracts for the three and nine months ended September 30, 2018 , respectively. (b) Includes $4 million of increases in fair value and an increase for realized losses due to settlements of $3 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended September 30, 2018 . Includes $9 million of decreases in fair value and an increase for realized losses due to settlements of $12 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the nine months ended September 30, 2018 . (c) Transfers into and out of Level 3 generally occur when the contract tenor becomes less and more observable respectively, primarily due to changes in market liquidity or assumptions for certain commodity contracts.
Total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis	The following tables present the income statement classification of the total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2019 and 2018 : Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total realized (losses) gains for the three months ended September 30, 2019 $ (25 ) $ (148 ) $ — $ 2 $ (25 ) $ (148 ) $ 2 $ — Total realized gains (losses) for the nine months ended September 30, 2019 122 (254 ) — 5 122 (254 ) 5 — Total unrealized gains (losses) for the three months ended September 30, 2019 99 (119 ) — 2 99 (119 ) 2 — Total unrealized gains (losses) for the nine months ended September 30, 2019 368 (202 ) 2 5 368 (202 ) 5 2 Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Revenues Purchased Power and Fuel Other, net Operating and Maintenance Total realized (losses) gains for the three months ended September 30, 2018 $ (176 ) $ (83 ) $ 1 $ (1 ) $ (176 ) $ (83 ) $ (1 ) $ 1 Total realized (losses) gains for the nine months ended September 30, 2018 (32 ) (156 ) 3 (1 ) (32 ) (156 ) (1 ) 3 Total unrealized (losses) for the three months ended September 30, 2018 (64 ) (40 ) — (1 ) (64 ) (40 ) (1 ) — Total unrealized gains (losses) for the nine months ended September 30, 2018 174 (15 ) — (5 ) 174 (15 ) (5 ) —
Fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis, valuation technique	The table below discloses the significant inputs to the forward curve used to value these positions. Type of trade Fair Value at September 30, 2019 Fair Value at December 31, 2018 Valuation Technique Unobservable Input 2019 Range 2018 Range Mark-to-market derivatives — Economic Hedges (Exelon and Generation) (a)(b) $ 411 $ 443 Discounted Forward power $11 - $167 $12 - $174 Forward gas $1.36 - $10.82 $0.78 - $12.38 Option Volatility 9% - 200% 10% - 277% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(b) $ 67 $ 56 Discounted Forward power $17 - $167 $14 - $174 Mark-to-market derivatives (Exelon and ComEd) $ (280 ) $ (249 ) Discounted Forward heat (c) 9x - 10x 10x - 11x Marketability 4% - 7% 4% - 8% Renewable 87% - 119% 86% - 120% _________ (a) The valuation techniques, unobservable inputs and ranges are the same for the asset and liability positions. (b) The fair values do not include cash collateral posted on level three positions of $304 million and $76 million as of September 30, 2019 and December 31, 2018 , respectively. (c) Quoted forward natural gas rates are utilized to project the forward power curve for the delivery of energy at specified future dates. The natural gas curve is extrapolated beyond its observable period to the end of the contract’s delivery.

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of the derivative fair value	The following table provides a summary of the derivative fair value balances recorded by Exelon, Generation and ComEd as of September 30, 2019 and December 31, 2018 : September 30, 2019 Exelon Generation ComEd Derivatives Total Economic Hedges Proprietary Trading Collateral (a)(b) Netting (a) Subtotal Economic Hedges Mark-to-market derivative assets (current assets) $ 602 $ 2,452 $ 143 $ 212 $ (2,205 ) $ 602 $ — Mark-to-market derivative assets (noncurrent assets) 483 1,386 67 104 (1,074 ) 483 — Total mark-to-market derivative assets 1,085 3,838 210 316 (3,279 ) 1,085 — Mark-to-market derivative liabilities (current liabilities) (224 ) (2,550 ) (101 ) 249 2,205 (197 ) (27 ) Mark-to-market derivative liabilities (noncurrent liabilities) (394 ) (1,324 ) (47 ) 156 1,074 (141 ) (253 ) Total mark-to-market derivative liabilities (618 ) (3,874 ) (148 ) 405 3,279 (338 ) (280 ) Total mark-to-market derivative net assets (liabilities) $ 467 $ (36 ) $ 62 $ 721 $ — $ 747 $ (280 ) December 31, 2018 Exelon Generation ComEd Description Total Economic Proprietary Collateral Netting (a) Subtotal Economic Mark-to-market derivative assets $ 801 $ 3,505 $ 105 $ 121 $ (2,930 ) $ 801 $ — Mark-to-market derivative assets 445 1,266 41 51 (913 ) 445 — Total mark-to-market derivative assets 1,246 4,771 146 172 (3,843 ) 1,246 — Mark-to-market derivative liabilities (473 ) (3,429 ) (74 ) 125 2,931 (447 ) (26 ) Mark-to-market derivative liabilities (474 ) (1,203 ) (20 ) 60 912 (251 ) (223 ) Total mark-to-market derivative liabilities (947 ) (4,632 ) (94 ) 185 3,843 (698 ) (249 ) Total mark-to-market derivative net assets (liabilities) $ 299 $ 139 $ 52 $ 357 $ — $ 548 $ (249 ) _________ (a) Exelon and Generation net all available amounts allowed under the derivative authoritative guidance in 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 amounts are immaterial and not reflected in the table above. (b) Of the collateral posted/(received), $306 million and $(94) million represents variation margin on the exchanges at September 30, 2019 and December 31, 2018 respectively.
Economic Hedges (Commodity Price Risk)	For the three and nine months ended September 30, 2019 and 2018 , Exelon and Generation recognized the following net pre-tax commodity mark-to-market gains (losses) which are also located in the Net fair value changes related to derivatives line in the Consolidated Statements of Cash Flows. Three Months Ended Nine Months Ended 2019 2018 2019 2018 Income Statement Location Gain (Loss) Gain (Loss) Operating revenues $ 76 $ 8 $ 65 $ (99 ) Purchased power and fuel (45 ) 66 (127 ) (4 ) Total Exelon and Generation $ 31 $ 74 $ (62 ) $ (103 )
Credit-Risk Related Contingent	The following tables provide information on Generation’s credit exposure for all derivative instruments, NPNS and applicable payables and receivables, net of collateral and instruments that are subject to master netting agreements, as of September 30, 2019 . The tables further delineate that exposure by credit rating of the counterparties and provide guidance on the concentration of credit risk to individual counterparties. The figures in the tables below exclude credit risk exposure from individual retail counterparties, nuclear fuel procurement contracts and exposure through RTOs, ISOs, NYMEX, ICE, NASDAQ, NGX and Nodal commodity exchanges. Additionally, the figures in the tables below exclude exposures with affiliates, including net receivables with ComEd, PECO, BGE, Pepco, DPL and ACE of $68 million , $30 million , $32 million , $39 million , $15 million and $8 million as of September 30, 2019 , respectively. Rating as of September 30, 2019 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 $ 693 $ 10 $ 683 — $ — Non-investment grade 74 38 36 No external ratings Internally rated — investment grade 297 1 296 Internally rated — non-investment grade 175 24 151 Total $ 1,239 $ 73 $ 1,166 — $ — Net Credit Exposure by Type of Counterparty As of Financial institutions $ 1 Investor-owned utilities, marketers, power producers 875 Energy cooperatives and municipalities 255 Other 35 Total $ 1,166 _________ (a) As of September 30, 2019 , credit collateral held from counterparties where Generation had credit exposure included $18 million of cash and $55 million of letters of credit. The credit collateral does not include non-liquid collateral.
Fair Value of Derivatives with Credit- Risk Related Contingent Features [Table Text Block] [Table Text Block]	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 Features September 30, 2019 December 31, 2018 Gross fair value of derivative contracts containing this feature (a) $ (1,249 ) $ (1,723 ) Offsetting fair value of in-the-money contracts under master netting arrangements (b) 947 1,105 Net fair value of derivative contracts containing this feature (c) $ (302 ) $ (618 ) _________ (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.
Cash Collateral and Letters of Credit on Derivative Contracts [Table Text Block]	As of September 30, 2019 and December 31, 2018 , Exelon and Generation posted or held the following amounts of cash collateral and letters of credit on derivative contracts with external counterparties, after giving consideration to offsetting derivative and non-derivative positions under master netting agreements. September 30, 2019 December 31, 2018 Cash collateral posted $ 787 $ 418 Letters of credit posted 273 367 Cash collateral held 96 47 Letters of credit held 58 44 Additional collateral required in the event of a credit downgrade below investment grade 1,481 2,104

Debt and Credit Agreements (Tab

Debt and Credit Agreements (Tables)	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Commercial Paper Borrowings	The following table reflects the Registrants' commercial paper programs as of September 30, 2019 and December 31, 2018 . Generation and PECO had no commercial paper borrowings as of both September 30, 2019 and December 31, 2018 . Outstanding Commercial Average Interest Rate on Commercial Paper Issuer September 30, 2019 December 31, 2018 September 30, 2019 December 31, 2018 Exelon $ 519 $ 89 2.50 % 2.15 % ComEd 387 — 2.51 % 2.14 % BGE — 35 2.49 % 2.18 % PHI 132 54 2.52 % 2.15 % PEPCO 12 40 2.61 % 2.24 % DPL 57 — 2.42 % 2.07 % ACE 63 14 2.57 % 2.21 %
Schedule of Long-term Debt Instruments [Table Text Block]	During the nine months ended September 30, 2019 , the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Generation Energy Efficiency Project Financing 3.95 % August 31, 2020 $ 4 Funding to install energy conservation measures for the Fort Meade project. Generation Energy Efficiency Project Financing 3.46 % May 1, 2020 $ 39 Funding to install energy conservation measures for the Marine Corps. Logistics Project. ComEd First Mortgage Bonds, Series 126 4.00 % March 1, 2049 $ 400 Repay a portion of ComEd’s outstanding commercial paper obligations and fund other general corporate purposes. PECO First and Refunding Mortgage Bonds 3.00 % September 15, 2049 $ 325 Repay short-term borrowings and for general corporate purposes BGE Senior Notes 3.20 % September 15, 2049 $ 400 Repay commercial paper obligations and for general corporate purposes Pepco First Mortgage Bonds 3.45 % June 13, 2029 $ 150 Repay existing indebtedness and for general corporate purposes Pepco Unsecured Tax-Exempt Bonds 1.70 % September 1, 2022 $ 110 Refinance existing indebtedness ACE First Mortgage Bonds 3.50 % May 21, 2029 $ 100 Repay existing indebtedness and for general corporate purposes ACE First Mortgage Bonds 4.14 % May 21, 2049 $ 50 Repay existing indebtedness and for general corporate purposes

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	The effective income tax rate from continuing operations varies from the U.S. Federal statutory rate principally due to the following: Three Months Ended September 30, 2019 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 6.4 5.2 8.1 (0.3) 6.3 4.8 1.9 6.6 6.9 Qualified NDT fund income 3.2 7.1 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (4.1) (8.9) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (1.7) — (1.0) (7.5) (1.1) (1.8) (2.6) (0.6) (1.9) Production tax credits and other credits (1.2) (2.7) — — — — — — — Noncontrolling interests (2.2) (4.8) — — — — — — — Excess deferred tax amortization (6.5) — (9.9) (3.6) (8.0) (17.7) (16.3) (13.5) (23.3) Other 0.7 0.5 0.4 (0.5) (0.2) 0.8 1.0 (0.1) 0.7 Effective income tax rate 15.6% 17.4% 18.4% 9.1% 17.9% 6.9% 4.9% 13.2% 3.1% Three Months Ended September 30, 2018 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit (1.2) (9.0) 8.3 (3.6) 7.3 0.2 1.0 6.6 7.3 Qualified NDT fund income 2.4 5.8 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.6) (1.1) (0.2) (0.1) — (0.2) (0.1) (0.3) (0.3) Plant basis differences (2.5) — (0.3) (15.2) (0.8) (2.0) (3.4) (0.7) (1.3) Production tax credits and other credits (1.2) (2.9) (0.1) — — — — — — Noncontrolling interests (1.1) (2.8) — — — — — — — Excess deferred tax amortization (6.8) — (7.8) (4.6) (7.9) (17.7) (21.2) (14.0) (15.4) Tax Cuts and Jobs Act of 2017 1.3 3.5 — — — 0.2 0.1 — — Other 3.2 5.6 0.3 0.9 2.6 0.6 0.3 0.6 0.3 Effective income tax rate 14.5% 20.1% 21.2% (1.6)% 22.2% 2.1% (2.3)% 13.2% 11.6% Nine Months Ended September 30, 2019 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 5.1 4.2 8.2 — 6.4 4.8 2.0 6.7 6.9 Qualified NDT fund income 5.3 11.9 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.9) (4.0) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (1.6) — (0.7) (6.8) (1.1) (1.8) (2.3) (0.6) (2.0) Production tax credits and other credits (1.0) (2.1) — — — — — — — Noncontrolling interests (1.0) (2.3) — — — — — — — Excess deferred tax amortization (6.0) — (9.2) (2.9) (7.9) (18.6) (17.3) (15.0) (23.4) Other 0.8 (0.1) 0.2 (0.2) 0.1 0.5 0.7 0.2 — Effective income tax rate 20.7% 28.6% 19.3% 11.1% 18.4% 5.7% 4.0% 12.1% 2.2% Nine Months Ended September 30, 2018 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 1.7 (2.6) 8.2 (3.6) 6.6 2.7 2.4 6.5 7.3 Qualified NDT fund income 0.9 2.6 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.9) (2.2) (0.2) (0.1) (0.1) (0.2) (0.1) (0.3) (0.3) Plant basis differences (2.7) — (0.1) (15.4) (0.7) (1.9) (2.9) (0.7) (1.3) Production tax credits and other credits (1.8) (5.1) (0.1) — — — — — — Noncontrolling interests (1.1) (3.2) — — — — — — — Excess deferred tax amortization (6.1) — (7.6) (3.4) (8.1) (14.5) (16.5) (11.0) (14.0) Tax Cuts and Jobs Act of 2017 0.2 1.3 (0.2) — — 0.3 — — — Other 0.4 2.0 0.1 — 0.9 0.3 — 0.4 0.9 Effective income tax rate 11.6% 13.8% 21.1% (1.5)% 19.6% 7.7% 3.9% 15.9% 13.6%
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	Exelon, Generation, ComEd, PHI and ACE have the following unrecognized tax benefits as of September 30, 2019 and December 31, 2018 . PECO, BGE, Pepco and DPL do not have unrecognized tax benefits for the periods presented. Exelon Generation ComEd PHI ACE September 30, 2019 $ 448 $ 411 $ — $ 45 $ 14 December 31, 2018 $ 477 $ 408 $ 2 $ 45 $ 14
Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table Text Block]	Exelon, Generation, PHI and ACE have the following unrecognized federal and state tax benefits that could significantly decrease within the 12 months after the reporting date as a result of completing audits, potential settlements, refund claims, and the outcomes of pending court cases as of September 30, 2019 : Exelon (a) Generation (a) PHI (b) ACE (b) $ 425 $ 411 $ 14 $ 14 __________ (a) Exelon and Generation have $411 million that, if recognized, would decrease the effective tax rate. (b) The unrecognized tax benefit related to PHI and ACE, if recognized, may be included in future base rates and that portion would have no impact to the effective tax rate.
Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]	In the third quarter of 2019, Exelon reviewed and updated its marginal state income tax rates based on 2018 state apportionment rates. As a result of the rate changes, the following accounting adjustments were recorded as of September 30, 2019: Exelon Generation Increase to deferred income tax liability $ 23 $ 9 Increase to income tax expense, net of federal taxes 23 9

Nuclear Decommissioning (Tables

Nuclear Decommissioning (Tables)	9 Months Ended
	Sep. 30, 2019
Schedule Of Nuclear Decommissioning [Line Items]
Schedule of Change in Asset Retirement Obligation [Table Text Block]	The following table provides a rollforward of the nuclear decommissioning ARO reflected in Exelon’s and Generation’s Consolidated Balance Sheets from December 31, 2018 to September 30, 2019 : Nuclear decommissioning ARO at December 31, 2018 (a)(b) $ 10,005 Sale of Oyster Creek (755 ) Accretion expense 361 Net increase due to changes in, and timing of, estimated future cash flows 211 Costs incurred related to decommissioning plants (52 ) Nuclear decommissioning ARO at September 30, 2019 (a) $ 9,770 _________ (a) Includes $127 million and $22 million as the current portion of the ARO at September 30, 2019 and December 31, 2018 , respectively, which is included in Other current liabilities in Exelon’s and Generation’s Consolidated Balance Sheets. (b) Includes $772 million of ARO related to Oyster Creek which was classified as Liabilities held for sale in Exelon's and Generation's Consolidated Balance Sheets at December 31, 2018 . See Note 3 — Mergers, Acquisitions and Dispositions for additional information.

Retirement Benefits (Tables)

Retirement Benefits (Tables)	9 Months Ended
	Sep. 30, 2019
Retirement Benefits [Abstract]
Calculation of Net Periodic Benefit Costs	A portion of the net periodic benefit cost for all plans is capitalized within the Consolidated Balance Sheets. The following table presents the components of Exelon's net periodic benefit costs, prior to capitalization, for the three and nine months ended September 30, 2019 and 2018 . Pension Benefits OPEB 2019 2018 2019 2018 Components of net periodic benefit cost: Service cost $ 89 $ 100 $ 23 $ 28 Interest cost 221 201 47 43 Expected return on assets (306 ) (312 ) (38 ) (43 ) Amortization of: Prior service benefit — — (45 ) (47 ) Actuarial loss 104 158 11 18 Settlement charges 7 — — — Contractual termination benefits 1 — — — Net periodic benefit cost $ 116 $ 147 $ (2 ) $ (1 ) Pension Benefits OPEB 2019 2018 2019 2018 Components of net periodic benefit cost: Service cost $ 267 $ 303 $ 70 $ 84 Interest cost 663 602 141 131 Expected return on assets (918 ) (939 ) (115 ) (130 ) Amortization of: Prior service cost (benefit) — 1 (134 ) (140 ) Actuarial loss 310 472 34 50 Settlement charges 7 1 — — Contractual termination benefits 1 — — — Net periodic benefit cost $ 330 $ 440 $ (4 ) $ (5 )
Allocated Portion of Pension and Postretirement Benefit Costs	The amounts below represent the Registrants' allocated pension and OPEB plan costs. For Exelon, the service cost component is included in Operating and maintenance expense and Property, plant and equipment, net while the non-service cost components are included in Other, net and Regulatory assets. For Generation and the Utility Registrants, the service cost and non-service cost components are included in Operating and maintenance expense and Property, plant and equipment, net in their consolidated financial statements. Three Months Ended September 30, Nine Months Ended September 30, Pension and OPEB Costs 2019 2018 2019 2018 Exelon $ 114 $ 145 $ 326 $ 435 Generation 37 50 100 151 ComEd 23 45 70 133 PECO 4 5 9 14 BGE 16 15 47 44 PHI 23 17 71 51 Pepco 6 3 19 10 DPL 4 2 11 5 ACE 4 3 12 10
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 and/or after-tax income in accordance with specified guidelines. All Registrants match a percentage of the employee contributions up to certain limits. The following table presents the matching contributions to the savings plans during the three and nine months ended September 30, 2019 and 2018 , respectively. Three Months Ended September 30, Nine Months Ended September 30, Savings Plan Matching Contributions 2019 2018 2019 2018 Exelon $ 36 $ 44 $ 101 $ 126 Generation 14 23 41 65 ComEd 9 8 26 23 PECO 2 2 7 7 BGE 4 2 9 5 PHI 4 4 8 10 Pepco 1 1 2 2 DPL 1 1 2 2 ACE 1 1 1 2

Changes in Accumulated Other _2

Changes in Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 2019
Changes in Accumulated Other Comprehensive Income [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following tables present changes in Exelon's AOCI, net of tax, by component: Three Months Ended September 30, 2019 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Currency Items AOCI of Investments in Unconsolidated Affiliates (b) Total Beginning balance $ (2 ) $ (2,957 ) $ (29 ) $ (2 ) $ (2,990 ) OCI before reclassifications — 6 (2 ) — 4 Amounts reclassified from AOCI — 21 — 2 23 Net current-period OCI — 27 (2 ) 2 27 Ending balance $ (2 ) $ (2,930 ) $ (31 ) $ — $ (2,963 ) Three Months Ended September 30, 2018 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Currency Items AOCI of Investments in Unconsolidated Affiliates (b) Total Beginning balance $ (2 ) $ (2,890 ) $ (29 ) $ — $ (2,921 ) OCI before reclassifications — 5 2 — 7 Amounts reclassified from AOCI — 45 — — 45 Net current-period OCI — 50 2 — 52 Ending balance $ (2 ) $ (2,840 ) $ (27 ) $ — $ (2,869 ) Nine Months Ended September 30, 2019 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Currency Items AOCI of Investments in Unconsolidated Affiliates (b) Total Beginning balance $ (2 ) $ (2,960 ) $ (33 ) $ — $ (2,995 ) OCI before reclassifications — (32 ) 2 (2 ) (32 ) Amounts reclassified from AOCI — 62 — 2 64 Net current-period OCI — 30 2 — 32 Ending balance $ (2 ) $ (2,930 ) $ (31 ) $ — $ (2,963 ) Nine Months Ended September 30, 2018 Gains (Losses) on Cash Flow Hedges Unrealized gains (losses) on Marketable Securities Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Currency Items AOCI of Investments in Unconsolidated Affiliates (b) Total Beginning balance $ (14 ) $ 10 $ (2,998 ) $ (23 ) $ (1 ) $ (3,026 ) OCI before reclassifications 11 — 22 (4 ) 1 30 Amounts reclassified from AOCI 1 — 136 — — 137 Net current-period OCI 12 — 158 (4 ) 1 167 Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard (c) — (10 ) — — — (10 ) Ending balance $ (2 ) $ — $ (2,840 ) $ (27 ) $ — $ (2,869 ) _________ (a) AOCI amounts are included in the computation of net periodic pension and OPEB cost. See Note 14 — Retirement Benefits for additional information. See Exelon's Statements of Operations and Comprehensive Income for individual components of AOCI. (b) All amounts are net of noncontrolling interests. (c) Exelon prospectively adopted the new standard Recognition and Measurement of Financial Assets and Liabilities. The standard was adopted as of January 1, 2018, which resulted in an increase to Retained earnings and Accumulated other comprehensive loss of $10 million for Exelon. The amounts reclassified related to Rabbi Trusts.
Schedule Of Other Comprehensive Income Loss Tax	The following table presents income tax benefit (expense) allocated to each component of Exelon's other comprehensive income (loss): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 6 $ 6 $ 18 $ 18 Actuarial loss reclassified to periodic benefit cost (13 ) (21 ) (39 ) (65 ) Pension and non-pension postretirement benefit plans valuation adjustment — (2 ) 14 (8 )

Commitments and Contingencies_2

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
PHI Merger Commitments	The following amounts represent total commitment costs that have been recorded since the acquisition date and the total remaining obligations for Exelon, PHI, Pepco, DPL and ACE as of September 30, 2019 : Description Exelon PHI Pepco DPL ACE Total commitments $ 513 $ 320 $ 120 $ 89 $ 111 Remaining commitments (a) 112 82 67 9 6
Commercial Commitments	The Registrants’ commercial commitments as of September 30, 2019 , representing commitments potentially triggered by future events were as follow s: Expiration within Total 2019 2020 2021 2022 2023 2024 and beyond Exelon Letters of credit $ 1,718 $ 1,192 $ 515 $ 11 $ — $ — $ — Surety bonds (a) 991 315 638 38 — — — Financing trust guarantees 378 — — — — — 378 Guaranteed lease residual values (b) 26 — 2 3 4 3 15 Total commercial commitments $ 3,113 $ 1,507 $ 1,155 $ 52 $ 4 $ 3 $ 393 Generation Letters of credit $ 1,686 $ 1,179 $ 496 $ 11 $ — $ — $ — Surety bonds (a) 790 298 492 — — — — Total commercial commitments $ 2,476 $ 1,477 $ 988 $ 11 $ — $ — $ — ComEd Letters of credit $ 7 $ 4 $ 3 $ — $ — $ — $ — Surety bonds (a) 50 5 43 2 — — — Financing trust guarantees 200 — — — — — 200 Total commercial commitments $ 257 $ 9 $ 46 $ 2 $ — $ — $ 200 PECO Surety bonds (a) $ 9 $ 1 $ 8 $ — $ — $ — $ — Financing trust guarantees 178 — — — — — 178 Total commercial commitments $ 187 $ 1 $ 8 $ — $ — $ — $ 178 BGE Letters of credit $ 8 $ 2 $ 6 $ — $ — $ — $ — Surety bonds (a) 17 2 15 — — — — Total commercial commitments $ 25 $ 4 $ 21 $ — $ — $ — $ — PHI Letters of credit $ 11 $ 1 $ 10 $ — $ — $ — $ — Surety bonds (a) 24 5 19 — — — — Guaranteed lease residual values (b) 26 — 2 3 4 3 15 Total commercial commitments $ 61 $ 6 $ 31 $ 3 $ 4 $ 3 $ 15 Pepco Letters of credit $ 10 $ — $ 10 $ — $ — $ — $ — Surety bonds (a) 17 2 15 — — — — Guaranteed lease residual values (b) 9 — — 1 1 1 6 Total commercial commitments $ 36 $ 2 $ 25 $ 1 $ 1 $ 1 $ 6 DPL Letters of credit $ 1 $ 1 $ — $ — $ — $ — $ — Surety bonds (a) 4 2 2 — — — — Guaranteed lease residual values (b) 11 — 1 1 2 1 6 Total commercial commitments $ 16 $ 3 $ 3 $ 1 $ 2 $ 1 $ 6 ACE Surety bonds (a) $ 3 $ 1 $ 2 $ — $ — $ — $ — Guaranteed lease residual values (b) 7 — 1 1 1 1 3 Total commercial commitments $ 10 $ 1 $ 3 $ 1 $ 1 $ 1 $ 3 _________ (a) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (b) Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The lease term associated with these assets ranges from 1 to 8 years . The maximum potential obligation at the end of the minimum lease term would be $68 million guaranteed by Exelon and PHI, of which $22 million , $29 million and $17 million is guaranteed by Pepco, DPL and ACE, respectively. Historically, payments under the guarantees have not been made and PHI believes the likelihood of payments being required under the guarantees is remote.
Accrued environmental liabilities	As of September 30, 2019 and December 31, 2018 , the Registrants had accrued the following undiscounted amounts for environmental liabilities in Other current liabilities and Other deferred credits and other liabilities within their respective Consolidated Balance Sheets: September 30, 2019 December 31, 2018 Total environmental investigation and remediation liabilities Portion of total related to MGP investigation and remediation Total environmental investigation and remediation liabilities Portion of total related to MGP investigation and remediation Exelon $ 507 $ 346 $ 496 $ 356 Generation 107 — 108 — ComEd 328 327 329 327 PECO 20 18 27 25 BGE 3 1 5 4 PHI 49 — 27 — Pepco 47 — 25 — DPL 1 — 1 — ACE 1 — 1 —

Supplemental Financial Inform_2

Supplemental Financial Information (Tables)	9 Months Ended
	Sep. 30, 2019
Supplemental Financial Information [Abstract]
Taxes Other Than Income	The following tables provide additional information about material items recorded in the Registrants' Consolidated Statements of Operations and Comprehensive Income. Taxes other than income Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended September 30, 2019 Utility taxes (a) $ 241 $ 29 $ 66 $ 38 $ 21 $ 86 $ 81 $ 5 $ — Property 148 66 7 5 39 31 21 9 — Payroll 57 28 7 3 4 6 2 1 1 Three Months Ended September 30, 2018 Utility taxes (a) $ 253 $ 32 $ 67 $ 39 $ 23 $ 92 $ 87 $ 5 $ — Property 145 70 7 4 37 26 16 9 — Payroll 58 31 6 3 4 5 1 1 1 Nine Months Ended September 30, 2019 Utility taxes (a) $ 672 $ 87 $ 183 $ 102 $ 68 $ 231 $ 217 $ 14 $ — Property 444 205 22 12 114 91 64 25 2 Payroll 185 92 21 11 13 20 5 3 2 Nine Months Ended September 30, 2018 Utility taxes (a) $ 705 $ 92 $ 188 $ 102 $ 70 $ 253 $ 238 $ 15 $ — Property 416 204 22 12 106 71 45 24 2 Payroll 191 99 20 11 12 19 5 3 2 _________ (a) Generation’s utility tax represents gross receipts tax related to its retail operations, and the Utility Registrants' utility taxes represents municipal and state utility taxes and gross receipts taxes related to their operating revenues. The offsetting collection of utility taxes from customers is recorded in revenues in the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
Schedule of Other Nonoperating Income, by Component	Other, Net Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended September 30, 2019 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 67 $ 67 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 33 33 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units 89 89 — — — — — — — Non-regulatory agreement units 55 55 — — — — — — — Regulatory offset to NDT fund-related activities (b) (125 ) (125 ) — — — — — — — Decommissioning-related activities 119 119 — — — — — — — AFUDC — Equity 22 — 4 3 6 9 7 1 1 Non-service net periodic benefit cost (2 ) — — — — — — — — Three Months Ended September 30, 2018 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 214 $ 214 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 58 58 — — — — — — — Net unrealized (losses) gains on NDT funds Regulatory agreement units (66 ) (66 ) — — — — — — — Non-regulatory agreement units 72 72 — — — — — — — Regulatory offset to NDT fund-related activities (b) (110 ) (110 ) — — — — — — — Decommissioning-related activities 168 168 — — — — — — — AFUDC — Equity 16 — 4 1 5 6 6 — — Non-service net periodic benefit cost (12 ) — — — — — — — — Other, Net Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2019 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 197 $ 197 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 316 316 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units 565 565 — — — — — — — Non-regulatory agreement units 236 236 — — — — — — — Regulatory offset to NDT fund-related activities (b) (611 ) (611 ) — — — — — — — Decommissioning-related activities 703 703 — — — — — — — AFUDC — Equity 64 — 13 9 16 26 18 3 4 Non-service net periodic benefit cost 8 — — — — — — — — Nine Months Ended September 30, 2018 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 476 $ 476 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 257 257 — — — — — — — Net unrealized losses on NDT funds Regulatory agreement units (335 ) (335 ) — — — — — — — Non-regulatory agreement units (143 ) (143 ) — — — — — — — Regulatory offset to NDT fund-related activities (b) (110 ) (110 ) — — — — — — — Decommissioning-related activities 145 145 — — — — — — — AFUDC — Equity 47 — 12 3 13 19 17 2 — Non-service net periodic benefit cost (33 ) — — — — — — — — _________ (a) Realized income includes interest, dividends and realized gains and losses on sales of NDT fund investments. (b) Includes the elimination of decommissioning-related activities for the Regulatory Agreement Units, including the elimination of income taxes related to all NDT fund activity for those units. See Note 15 — Asset Retirement Obligations of the Exelon 2018 Form 10-K for additional information regarding the accounting for nuclear decommissioning.
Cash Flow Supplemental Disclosures	The following tables provide additional information about material items recorded in the Registrants' Consolidated Statements of Cash Flows. Depreciation, amortization and accretion Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2019 Property, plant and equipment (a) $ 2,803 $ 1,184 $ 661 $ 225 $ 263 $ 405 $ 178 $ 109 $ 89 Amortization of regulatory assets (a) 390 — 106 22 105 157 103 29 25 Amortization of intangible assets, net (a) 44 37 — — — — — — — Amortization of energy contract assets and liabilities (b) 14 14 — — — — — — — Nuclear fuel (c) 771 771 — — — — — — — ARO accretion (d) 371 371 — — — — — — — Total depreciation, amortization and accretion $ 4,393 $ 2,377 $ 767 $ 247 $ 368 $ 562 $ 281 $ 138 $ 114 Nine Months Ended September 30, 2018 Property, plant and equipment (a) $ 2,829 $ 1,347 $ 613 $ 204 $ 249 $ 355 $ 161 $ 97 $ 70 Amortization of regulatory assets (a) 412 — 83 20 109 200 125 38 37 Amortization of intangible assets, net (a) 43 36 — — — — — — — Amortization of energy contract assets and liabilities (b) 8 8 — — — — — — — Nuclear fuel (c) 852 852 — — — — — — — ARO accretion (d) 367 365 — — — — — — — Total depreciation, amortization and accretion $ 4,511 $ 2,608 $ 696 $ 224 $ 358 $ 555 $ 286 $ 135 $ 107 _________ (a) Included in Depreciation and amortization in the Registrants' Consolidated Statements of Operations and Comprehensive Income. (b) Included in Operating revenues or Purchased power and fuel expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (c) Included in Purchased power and fuel expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (d) Included in Operating and maintenance expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Other non-cash operating activities Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2019 Pension and non-pension postretirement benefit costs $ 324 $ 98 $ 70 $ 9 $ 45 $ 71 $ 19 $ 11 $ 12 Provision for uncollectible accounts 89 20 26 22 5 16 7 2 6 Other decommissioning-related activity (a) (400 ) (400 ) — — — — — — — Energy-related options (b) 21 21 — — — — — — — Amortization of rate stabilization deferral (8 ) — — — — (8 ) (9 ) 1 — Discrete impacts from EIMA and FEJA (c) 80 — 80 — — — — — — Long-term incentive plan 33 — — — — — — — — Amortization of operating ROU asset 193 138 2 — 23 26 6 7 4 Change in environmental liabilities 23 — — — — 23 23 — — Nine Months Ended September 30, 2018 Pension and non-pension postretirement benefit costs $ 435 $ 151 $ 133 $ 14 $ 43 $ 51 $ 10 $ 5 $ 10 Provision for uncollectible accounts 133 38 30 25 6 32 12 6 14 Other decommissioning-related activity (a) (39 ) (39 ) — — — — — — — Energy-related options (b) 4 4 — — — — — — — Amortization of rate stabilization deferral — — — — — — — — — Discrete impacts from EIMA and FEJA (c) 27 — 27 — — — — — — Long-term incentive plan 84 — — — — — — — — Asset retirement costs 20 — — — — 20 22 (1 ) (1 ) _______ (a) Includes the elimination of decommissioning-related 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 2018 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 in Operating revenues and expenses. (c) Reflects the change in ComEd's distribution and energy efficiency formula rates. See Note 6 — Regulatory Matters for additional information. The following tables provide a reconciliation of cash, cash equivalents and restricted cash reported within the Registrants’ Consolidated Balance Sheets that sum to the total of the same amounts in their Consolidated Statements of Cash Flows. Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2019 Cash and cash equivalents $ 1,683 $ 1,019 $ 76 $ 224 $ 130 $ 99 $ 18 $ 11 $ 13 Restricted cash 309 126 124 6 1 38 34 — 3 Restricted cash included in other long-term assets 186 — 171 — — 15 — — 15 Total cash, cash equivalents and restricted cash $ 2,178 $ 1,145 $ 371 $ 230 $ 131 $ 152 $ 52 $ 11 $ 31 December 31, 2018 Cash and cash equivalents $ 1,349 $ 750 $ 135 $ 130 $ 7 $ 124 $ 16 $ 23 $ 7 Restricted cash 247 153 29 5 6 43 37 1 4 Restricted cash included in other long-term assets 185 — 166 — — 19 — — 19 Total cash, cash equivalents and restricted cash $ 1,781 $ 903 $ 330 $ 135 $ 13 $ 186 $ 53 $ 24 $ 30 September 30, 2018 Cash and cash equivalents $ 1,918 $ 1,187 $ 124 $ 102 $ 113 $ 153 $ 12 $ 110 $ 11 Restricted cash 240 152 12 5 3 42 35 — 7 Restricted cash included in other long-term assets 163 — 144 — — 19 — — 19 Total cash, cash equivalents and restricted cash $ 2,321 $ 1,339 $ 280 $ 107 $ 116 $ 214 $ 47 $ 110 $ 37 December 31, 2017 Cash and cash equivalents $ 898 $ 416 $ 76 $ 271 $ 17 $ 30 $ 5 $ 2 $ 2 Restricted cash 207 138 5 4 1 42 35 — 6 Restricted cash included in other long-term assets 85 — 63 — — 23 — — 23 Total cash, cash equivalents and restricted cash $ 1,190 $ 554 $ 144 $ 275 $ 18 $ 95 $ 40 $ 2 $ 31 For additional information on restricted cash see Note 1 — Significant Accounting Policies of the Exelon 2018 Form 10-K.
Supplemental Balance Sheet Disclosures	The following tables provide additional information about material items recorded in the Registrants' Consolidated Balance Sheets. Unbilled customer revenues Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2019 $ 1,256 $ 676 $ 212 $ 102 $ 103 $ 163 $ 91 $ 38 $ 34 December 31, 2018 1,656 965 223 114 168 186 97 59 30 Accrued expenses Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2019 Compensation-related accruals (a) $ 880 $ 336 $ 133 $ 48 $ 63 $ 86 $ 26 $ 17 $ 13 Taxes accrued 431 247 56 13 64 80 61 17 3 Interest accrued 421 106 62 33 36 78 37 20 19 December 31, 2018 Compensation-related accruals (a) $ 1,191 $ 479 $ 187 $ 49 $ 68 $ 99 $ 29 $ 19 $ 12 Taxes accrued 412 226 71 28 46 74 58 4 5 Interest accrued 334 77 105 33 39 50 25 8 12 _________ (a) Primarily includes accrued payroll, bonuses and other incentives, vacation and benefits.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Segment Reporting [Abstract]
Analysis and reconciliation of reportable segment information	An analysis and reconciliation of the Registrants’ reportable segment information to the respective information in the consolidated financial statements for the three and nine months ended September 30, 2019 and 2018 is as follows: Three Months Ended September 30, 2019 and 2018 Generation (a) ComEd PECO BGE PHI Other (b) Intersegment Exelon Operating revenues (c) : 2019 Competitive businesses electric revenues $ 4,314 $ — $ — $ — $ — $ — $ (275 ) $ 4,039 Competitive businesses natural gas revenues 265 — — — — — 1 266 Competitive businesses other revenues 195 — — — — — (1 ) 194 Rate-regulated electric revenues — 1,583 716 619 1,357 — (7 ) 4,268 Rate-regulated natural gas revenues — — 62 84 20 — (3 ) 163 Shared service and other revenues — — — — 3 474 (478 ) (1 ) Total operating revenues $ 4,774 $ 1,583 $ 778 $ 703 $ 1,380 $ 474 $ (763 ) $ 8,929 Generation (a) ComEd PECO BGE PHI Other (b) Intersegment Exelon 2018 Competitive businesses electric revenues $ 4,741 $ — $ — $ — $ — $ — $ (306 ) $ 4,435 Competitive businesses natural gas revenues 397 — — — — — — 397 Competitive businesses other revenues 140 — — — — — (1 ) 139 Rate-regulated electric revenues — 1,598 700 645 1,334 — (7 ) 4,270 Rate-regulated natural gas revenues — — 57 86 24 — (5 ) 162 Shared service and other revenues — — — — 3 458 (461 ) — Total operating revenues $ 5,278 $ 1,598 $ 757 $ 731 $ 1,361 $ 458 $ (780 ) $ 9,403 Intersegment revenues (d) : 2019 $ 275 $ 4 $ 1 $ 6 $ 4 $ 474 $ (764 ) $ — 2018 308 4 2 6 3 456 (779 ) — Depreciation and amortization: 2019 $ 407 $ 259 $ 83 $ 116 $ 193 $ 25 $ — $ 1,083 2018 468 237 75 110 192 23 — 1,105 Operating expenses: 2019 $ 4,274 $ 1,256 $ 595 $ 612 $ 1,124 $ 457 $ (759 ) $ 7,559 2018 4,961 1,275 603 628 1,116 459 (790 ) 8,252 Interest expense, net: 2019 $ 109 $ 91 $ 33 $ 31 $ 66 $ 79 $ — $ 409 2018 101 85 32 27 65 83 — 393 Income (loss) before income taxes: 2019 $ 501 $ 245 $ 154 $ 67 $ 203 $ (68 ) $ — $ 1,102 2018 389 245 124 81 191 (83 ) — 947 Income Taxes: 2019 $ 87 $ 45 $ 14 $ 12 $ 14 $ — $ — $ 172 2018 78 52 (2 ) 18 4 (13 ) — 137 Net income (loss): 2019 $ 244 $ 200 $ 140 $ 55 $ 189 $ (68 ) $ — $ 760 2018 300 193 126 63 187 (69 ) — 800 Capital Expenditures 2019 $ 392 $ 452 $ 228 $ 300 $ 308 $ 7 $ — $ 1,687 2018 362 514 204 233 359 18 — 1,690 __________ (a) Intersegment revenues for Generation in 2019 include revenue from sales to PECO of $43 million , sales to BGE of $65 million , sales to Pepco of $65 million , sales to DPL of $14 million and sales to ACE of $3 million in the Mid-Atlantic region, and sales to ComEd of $83 million in the Midwest region, which eliminate upon consolidation. Intersegment revenues for Generation in 2018 include revenue from sales to PECO of $35 million , sales to BGE of $69 million , sales to Pepco of $46 million , sales to DPL of $26 million and sales to ACE of $10 million in the Mid-Atlantic region, and sales to ComEd of $122 million in the Midwest region, which eliminate upon consolidation. (b) Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities. (c) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 17 — Supplemental Financial Information for additional information on total utility taxes. (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. PHI: Pepco DPL ACE Other (b) Intersegment PHI Operating revenues (a) : 2019 Rate-regulated electric revenues $ 642 $ 299 $ 419 $ — $ (3 ) $ 1,357 Rate-regulated natural gas revenues — 20 — — — 20 Shared service and other revenues — — — 92 (89 ) 3 Total operating revenues $ 642 $ 319 $ 419 $ 92 $ (92 ) $ 1,380 2018 Rate-regulated electric revenues $ 628 $ 304 $ 406 $ — $ (4 ) $ 1,334 Rate-regulated natural gas revenues — 24 — — — 24 Shared service and other revenues — — — 103 (100 ) 3 Total operating revenues $ 628 $ 328 $ 406 $ 103 $ (104 ) $ 1,361 Intersegment revenues: 2019 $ 2 $ 1 $ 1 $ 93 $ (93 ) $ 4 2018 2 2 1 103 (105 ) 3 Depreciation and amortization: 2019 $ 95 $ 46 $ 43 $ 9 $ — $ 193 2018 99 47 38 8 — 192 Operating expenses: 2019 $ 515 $ 268 $ 340 $ 95 $ (94 ) $ 1,124 2018 516 277 322 105 (104 ) 1,116 Interest expense, net: 2019 $ 33 $ 15 $ 15 $ 3 $ — $ 66 2018 32 15 16 2 — 65 Income (loss) before income taxes: 2019 $ 103 $ 38 $ 65 $ 192 $ (195 ) $ 203 2018 87 38 69 179 (182 ) 191 Income Taxes: 2019 $ 5 $ 5 $ 2 $ 3 $ (1 ) $ 14 2018 (2 ) 5 8 (8 ) 1 4 Net income (loss): 2019 $ 98 $ 33 $ 63 $ (9 ) $ 4 $ 189 2018 89 33 61 1 3 187 Capital Expenditures 2019 $ 157 $ 85 $ 73 $ (7 ) $ — $ 308 2018 188 88 77 6 — 359 __________ (a) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 17 — Supplemental Financial Information for additional information on total utility taxes. (b) Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities.	Nine Months Ended September 30, 2019 and 2018 Generation (a) ComEd PECO BGE PHI Other (b) Intersegment Exelon Operating revenues (c) : 2019 Competitive businesses electric revenues $ 12,365 $ — $ — $ — $ — $ — $ (840 ) $ 11,525 Competitive businesses natural gas revenues 1,479 — — — — — — 1,479 Competitive businesses other revenues 436 — — — — — (4 ) 432 Rate-regulated electric revenues — 4,342 1,901 1,817 3,574 — (25 ) 11,609 Rate-regulated natural gas revenues — — 432 510 116 — (12 ) 1,046 Shared service and other revenues — — — — 10 1,410 (1,415 ) 5 Total operating revenues $ 14,280 $ 4,342 $ 2,333 $ 2,327 $ 3,700 $ 1,410 $ (2,296 ) $ 26,096 2018 Competitive businesses electric revenues $ 13,190 $ — $ — $ — $ — $ — $ (969 ) $ 12,221 Competitive businesses natural gas revenues 1,839 — — — — — (8 ) 1,831 Competitive businesses other revenues 339 — — — — — (4 ) 335 Rate-regulated electric revenues — 4,508 1,893 1,850 3,549 — (34 ) 11,766 Rate-regulated natural gas revenues — — 382 519 129 — (13 ) 1,017 Shared service and other revenues — — — — 10 1,398 (1,408 ) — Total operating revenues $ 15,368 $ 4,508 $ 2,275 $ 2,369 $ 3,688 $ 1,398 $ (2,436 ) $ 27,170 Shared service and other revenues Intersegment revenues (d) : 2019 $ 844 $ 13 $ 4 $ 18 $ 11 $ 1,410 $ (2,300 ) $ — 2018 981 23 5 18 11 1,392 (2,430 ) — Depreciation and amortization: 2019 $ 1,221 $ 767 $ 247 $ 368 $ 562 $ 72 $ — $ 3,237 2018 1,383 696 224 358 555 68 — 3,284 Operating expenses: 2019 $ 13,333 $ 3,431 $ 1,783 $ 1,936 $ 3,106 $ 1,405 $ (2,291 ) $ 22,703 2018 14,475 3,610 1,853 2,005 3,165 1,395 (2,467 ) 24,036 Interest expense, net: 2019 $ 336 $ 268 $ 100 $ 89 $ 197 $ 231 $ — $ 1,221 2018 305 261 96 78 193 205 — 1,138 Generation (a) ComEd PECO BGE PHI Other (b) Intersegment Exelon Income (loss) before income taxes: 2019 $ 1,355 $ 674 $ 461 $ 320 $ 436 $ (218 ) $ — $ 3,028 2018 800 663 331 301 363 (195 ) — 2,263 Income Taxes: 2019 $ 388 $ 130 $ 51 $ 59 $ 25 $ (27 ) $ — $ 626 2018 110 140 (5 ) 59 28 (70 ) — 262 Net income (loss): 2019 $ 784 $ 544 $ 410 $ 261 $ 412 $ (191 ) $ — $ 2,220 2018 667 523 336 242 336 (125 ) — 1,979 Capital Expenditures 2019 $ 1,282 $ 1,413 $ 675 $ 842 $ 1,006 $ 41 $ — $ 5,259 2018 1,660 1,540 615 667 988 27 — 5,497 Total assets: September 30, 2019 $ 47,984 $ 32,326 $ 11,379 $ 10,304 $ 22,576 $ 8,254 $ (10,085 ) $ 122,738 December 31, 2018 47,556 31,213 10,642 9,716 21,984 8,355 (9,800 ) 119,666 __________ (a) Intersegment revenues for Generation in 2019 include revenue from sales to PECO of $123 million , sales to BGE of $199 million , sales to Pepco of $188 million , sales to DPL of $50 million and sales to ACE of $16 million in the Mid-Atlantic region, and sales to ComEd of $266 million in the Midwest region, which eliminate upon consolidation. Intersegment revenues for Generation in 2018 include revenue from sales to PECO of $97 million , sales to BGE of $198 million , sales to Pepco of $143 million , sales to DPL of $103 million and sales to ACE of $21 million in the Mid-Atlantic region, and sales to ComEd of $419 million in the Midwest region, which eliminate upon consolidation. (b) Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities. (c) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 17 — Supplemental Financial Information for additional information on total utility taxes. (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. PHI: Pepco DPL ACE Other (b) Intersegment PHI Operating revenues (a) : 2019 Rate-regulated electric revenues $ 1,748 $ 871 $ 966 $ (1 ) $ (10 ) $ 3,574 Rate-regulated natural gas revenues — 116 — — — 116 Shared service and other revenues — — — 298 (288 ) 10 Total operating revenues $ 1,748 $ 987 $ 966 $ 297 $ (298 ) $ 3,700 2018 Rate-regulated electric revenues $ 1,708 $ 872 $ 981 $ — $ (12 ) $ 3,549 Rate-regulated natural gas revenues — 129 — — — 129 Shared service and other revenues — — — 326 (316 ) 10 Total operating revenues $ 1,708 $ 1,001 $ 981 $ 326 $ (328 ) $ 3,688 Intersegment revenues: 2019 $ 5 $ 5 $ 2 $ 297 $ (298 ) $ 11 2018 5 6 2 325 (327 ) 11 Depreciation and amortization: 2019 $ 281 $ 138 $ 114 $ 29 $ — $ 562 2018 286 135 107 27 — 555 Operating expenses: 2019 $ 1,444 $ 820 $ 838 $ 302 $ (298 ) $ 3,106 2018 1,454 859 847 329 (324 ) 3,165 Interest expense, net: 2019 $ 100 $ 45 $ 44 $ 8 $ — $ 197 2018 96 42 48 7 — 193 Income (loss) before income taxes: 2019 $ 226 $ 132 $ 89 $ 411 $ (422 ) $ 436 2018 181 107 88 326 (339 ) 363 Income Taxes: 2019 $ 9 $ 16 $ 2 $ (1 ) $ (1 ) $ 25 2018 7 17 12 (8 ) — 28 Net income (loss): 2019 $ 217 $ 116 $ 87 $ (19 ) $ 11 $ 412 2018 174 90 76 (15 ) 11 336 Capital Expenditures 2019 $ 455 $ 245 $ 300 $ 6 $ — $ 1,006 2018 475 254 247 12 — 988 Total assets: September 30, 2019 $ 8,603 $ 4,724 $ 3,916 $ 11,071 $ (5,738 ) $ 22,576 December 31, 2018 8,299 4,588 3,699 10,819 (5,421 ) 21,984 __________ (a) Includes gross utility tax receipts from customers. The offsetting remittance of utility taxes to the governing bodies is recorded in expenses in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. See Note 17 — Supplemental Financial Information for additional information on total utility taxes. (b) Other primarily includes PHI’s corporate operations, shared service entities and other financing and investment activities.
Analysis and reconciliation of reportable segment revenues for Generation	The following tables disaggregate the Registrants' revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. For Generation, the disaggregation of revenues reflects Generation’s two primary products of power sales and natural gas sales, with further disaggregation of power sales provided by geographic region. For the Utility Registrants, the disaggregation of revenues reflects the two primary utility services of rate-regulated electric sales and rate-regulated natural gas sales (where applicable), with further disaggregation of these tariff sales provided by major customer groups. Exelon’s disaggregated revenues are consistent with Generation and the Utility Registrants, but exclude any intercompany revenues. Competitive Business Revenues (Generation): Three Months Ended September 30, 2019 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,351 $ 10 $ 1,361 $ 3 $ 1,364 Midwest 1,052 47 1,099 (17 ) 1,082 New York 414 15 429 — 429 ERCOT 288 72 360 5 365 Other Power Regions 873 192 1,065 (25 ) 1,040 Total Competitive Businesses Electric Revenues 3,978 336 4,314 (34 ) 4,280 Competitive Businesses Natural Gas Revenues 160 105 265 34 299 Competitive Businesses Other Revenues (c) 112 83 195 — 195 Total Generation Consolidated Operating Revenues $ 4,250 $ 524 $ 4,774 $ — $ 4,774 Three Months Ended September 30, 2018 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,397 $ 52 $ 1,449 $ 7 $ 1,456 Midwest 1,095 26 1,121 (4 ) 1,117 New York 475 (6 ) 469 — 469 ERCOT 156 289 445 (1 ) 444 Other Power Regions 959 298 1,257 (45 ) 1,212 Total Competitive Businesses Electric Revenues 4,082 659 4,741 (43 ) 4,698 Competitive Businesses Natural Gas Revenues 200 197 397 43 440 Competitive Businesses Other Revenues (c) 130 10 140 — 140 Total Generation Consolidated Operating Revenues $ 4,412 $ 866 $ 5,278 $ — $ 5,278 __________ (a) Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants. (b) Includes revenues from derivatives and leases. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Includes unrealized mark-to-market gains of $77 million and $6 million in 2019 and 2018 , respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Three Months Ended September 30, 2019 Three Months Ended September 30, 2018 RNF (a) Intersegment RNF Total RNF RNF (a) Intersegment RNF Total RNF Mid-Atlantic $ 684 $ 5 $ 689 $ 746 $ 17 $ 763 Midwest 763 (16 ) 747 763 5 768 New York 288 3 291 290 2 292 ERCOT 76 (4 ) 72 161 (63 ) 98 Other Power Regions 212 (28 ) 184 226 (46 ) 180 Total Revenues net of purchased power and fuel for Reportable Segments 2,023 (40 ) 1,983 2,186 (85 ) 2,101 Other (b) 100 40 140 112 85 197 Total Generation Revenues net of purchased power and fuel expense $ 2,123 $ — $ 2,123 $ 2,298 $ — $ 2,298 __________ (a) Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allocated to a region. See text above for a description of included activities. Includes unrealized mark-to-market gains of $17 million and $71 million in 2019 and 2018 , respectively, accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 8 — Early Plant Retirements of $3 million and $18 million decrease to RNF in 2019 and 2018 , respectively, and the elimination of intersegment RNF.	The following tables disaggregate the Registrants' revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. For Generation, the disaggregation of revenues reflects Generation’s two primary products of power sales and natural gas sales, with further disaggregation of power sales provided by geographic region. For the Utility Registrants, the disaggregation of revenues reflects the two primary utility services of rate-regulated electric sales and rate-regulated natural gas sales (where applicable), with further disaggregation of these tariff sales provided by major customer groups. Exelon’s disaggregated revenues are consistent with Generation and the Utility Registrants, but exclude any intercompany revenues. Competitive Business Revenues (Generation): Nine Months Ended September 30, 2019 Revenues from external customers (a) Intersegment Revenues Total Revenues Contracts with customers Other (b) Total Mid-Atlantic $ 3,798 $ 9 $ 3,807 $ 2 $ 3,809 Midwest 3,083 172 3,255 (31 ) 3,224 New York 1,195 16 1,211 — 1,211 ERCOT 594 198 792 13 805 Other Power Regions 2,849 451 3,300 (46 ) 3,254 Total Competitive Businesses Electric Revenues 11,519 846 12,365 (62 ) 12,303 Competitive Businesses Natural Gas Revenues 1,041 438 1,479 62 1,541 Competitive Businesses Other Revenues (c) 343 93 436 — 436 Total Generation Consolidated Operating Revenues $ 12,903 $ 1,377 $ 14,280 $ — $ 14,280 Nine Months Ended September 30, 2018 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 3,971 $ 191 $ 4,162 $ 17 $ 4,179 Midwest 3,432 169 3,601 (8 ) 3,593 New York 1,305 (37 ) 1,268 1 1,269 ERCOT 470 459 929 1 930 Other Power Regions 2,656 574 3,230 (116 ) 3,114 Total Competitive Businesses Electric Revenues 11,834 1,356 13,190 (105 ) 13,085 Competitive Businesses Natural Gas Revenues 1,016 823 1,839 105 1,944 Competitive Businesses Other Revenues (c) 385 (46 ) 339 — 339 Total Generation Consolidated Operating Revenues $ 13,235 $ 2,133 $ 15,368 $ — $ 15,368 __________ (a) Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants. (b) Includes revenues from derivatives and leases. (c) Other represents activities not allocated to a region. See text above for a description of included activities. Includes unrealized mark-to-market gains of $64 million and losses of $96 million in 2019 and 2018 , respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Nine Months Ended September 30, 2019 Nine Months Ended September 30, 2018 RNF from external customers (a) Intersegment RNF Total RNF RNF from external customers (a) Intersegment RNF Total RNF Mid-Atlantic $ 2,007 $ 16 $ 2,023 $ 2,303 $ 45 $ 2,348 Midwest 2,269 (22 ) 2,247 2,381 19 2,400 New York 800 10 810 832 9 841 ERCOT 252 (27 ) 225 396 (180 ) 216 Other Power Regions 542 (64 ) 478 740 (133 ) 607 Total Revenues net of purchased power and fuel expense for Reportable Segments 5,870 (87 ) 5,783 6,652 (240 ) 6,412 Other (b) 262 87 349 164 240 404 Total Generation Revenues net of purchased power and fuel expense $ 6,132 $ — $ 6,132 $ 6,816 $ — $ 6,816 __________ (a) Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allocated to a region. See text above for a description of included activities. Includes unrealized mark-to-market losses of $84 million and $104 million in 2019 and 2018 , respectively, accelerated nuclear fuel amortization associated with announced early plant retirements as discussed in Note 8 — Early Plant Retirements of $13 million and $53 million decrease to RNF in 2019 and 2018 , respectively, and the elimination of intersegment RNF.
Schedule of Revenue by Major Customers by Reporting Segments [Table Text Block]	Electric and Gas Revenue by Customer Class (Utility Registrants): Three Months Ended September 30, 2019 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 865 $ 479 $ 352 $ 741 $ 311 $ 178 $ 252 Small commercial & industrial 393 109 64 147 41 48 58 Large commercial & industrial 141 63 116 297 222 26 49 Public authorities & electric railroads 12 9 7 17 11 3 3 Other (a) 222 63 82 164 58 50 56 Total rate-regulated electric revenues (b) $ 1,633 $ 723 $ 621 $ 1,366 $ 643 $ 305 $ 418 Rate-regulated natural gas revenues Residential $ — $ 38 $ 49 $ 9 $ — $ 9 $ — Small commercial & industrial — 17 9 4 — 4 — Large commercial & industrial — — 20 1 — 1 — Transportation — 5 — 4 — 4 — Other (c) — 2 5 2 — 2 — Total rate-regulated natural gas revenues (d) $ — $ 62 $ 83 $ 20 $ — $ 20 $ — Total rate-regulated revenues from contracts with customers $ 1,633 $ 785 $ 704 $ 1,386 $ 643 $ 325 $ 418 Other revenues Revenues from alternative revenue programs $ (56 ) $ (11 ) $ (5 ) $ (9 ) $ (3 ) $ (6 ) $ 1 Other rate-regulated electric revenues (e) 6 4 3 3 2 — — Other rate-regulated natural gas revenues (e) — — 1 — — — — Total other revenues $ (50 ) $ (7 ) $ (1 ) $ (6 ) $ (1 ) $ (6 ) $ 1 Total rate-regulated revenues for reportable segments $ 1,583 $ 778 $ 703 $ 1,380 $ 642 $ 319 $ 419 Three Months Ended September 30, 2018 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 861 $ 458 $ 366 $ 726 $ 306 $ 180 $ 240 Small commercial & industrial 391 108 68 140 39 48 53 Large commercial & industrial 131 64 117 303 230 25 48 Public authorities & electric railroads 11 7 7 14 8 3 3 Other (a) 212 59 91 156 47 47 63 Total rate-regulated electric revenues (b) $ 1,606 $ 696 $ 649 $ 1,339 $ 630 $ 303 $ 407 Rate-regulated natural gas revenues Residential $ — $ 36 $ 46 $ 8 $ — $ 8 $ — Small commercial & industrial — 15 8 5 — 5 — Large commercial & industrial — — 17 2 — 2 — Transportation — 5 — 3 — 3 — Other (c) — 1 12 6 — 6 — Total rate-regulated natural gas revenues (d) $ — $ 57 $ 83 $ 24 $ — $ 24 $ — Total rate-regulated revenues from contracts with customers $ 1,606 $ 753 $ 732 $ 1,363 $ 630 $ 327 $ 407 Other revenues Revenues from alternative revenue programs $ (15 ) $ 1 $ (6 ) $ (5 ) $ (4 ) $ — $ (1 ) Other rate-regulated electric revenues (e) 7 3 4 3 2 1 — Other rate-regulated natural gas revenues (e) — — 1 — — — — Total other revenues $ (8 ) $ 4 $ (1 ) $ (2 ) $ (2 ) $ 1 $ (1 ) Total rate-regulated revenues for reportable segments $ 1,598 $ 757 $ 731 $ 1,361 $ 628 $ 328 $ 406 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates of $4 million , $1 million , $2 million , $4 million , $2 million , $1 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, in 2019 and $4 million , $2 million , $1 million , $3 million $2 million , $2 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, in 2018 . (c) Includes revenues from off-system natural gas sales. (d) Includes operating revenues from affiliates of less than $1 million and $4 million at PECO and BGE, respectively, in 2019 and less than $1 million and $5 million at PECO and BGE, respectively, in 2018 . (e) Includes late payment charge revenues.	Electric and Gas Revenue by Customer Class (Utility Registrants): Nine Months Ended September 30, 2019 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 2,221 $ 1,231 $ 1,019 $ 1,816 $ 792 $ 499 $ 525 Small commercial & industrial 1,103 304 193 387 114 141 132 Large commercial & industrial 399 163 335 843 633 75 135 Public authorities & electric railroads 35 23 20 47 27 10 10 Other (a) 660 186 242 481 166 151 164 Total rate-regulated electric revenues (b) 4,418 1,907 1,809 3,574 1,732 876 966 Rate-regulated natural gas revenues Residential — 285 327 64 — 64 — Small commercial & industrial — 122 55 30 — 30 — Large commercial & industrial — 1 93 4 — 4 — Transportation — 18 — 11 — 11 — Other (c) — 5 19 6 — 6 — Total rate-regulated natural gas revenues (d) — 431 494 115 — 115 — Total rate-regulated revenues from contracts with customers 4,418 2,338 2,303 3,689 1,732 991 966 Other revenues Revenues from alternative revenue programs (98 ) (16 ) 11 4 10 (6 ) — Other rate-regulated electric revenues (e) 22 10 10 7 6 1 — Other rate-regulated natural gas revenues (e) — 1 3 — — 1 — Total other revenues (76 ) (5 ) 24 11 16 (4 ) — Total rate-regulated revenues for reportable segments $ 4,342 $ 2,333 $ 2,327 $ 3,700 $ 1,748 $ 987 $ 966 Nine Months Ended September 30, 2018 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 2,277 $ 1,199 $ 1,054 $ 1,839 $ 792 $ 513 $ 534 Small commercial & industrial 1,132 306 196 370 104 138 128 Large commercial & industrial 411 174 325 845 632 74 139 Public authorities & electric railroads 36 21 21 44 24 10 10 Other (a) 656 181 246 446 145 129 174 Total rate-regulated electric revenues (b) 4,512 1,881 1,842 3,544 1,697 864 985 Rate-regulated natural gas revenues Residential — 259 345 68 — 68 — Small commercial & industrial — 102 55 31 — 31 — Large commercial & industrial — 1 88 7 — 7 — Transportation — 16 — 12 — 12 — Other (c) — 4 49 11 — 11 — Total rate-regulated natural gas revenues (d) — 382 537 129 — 129 — Total rate-regulated revenues from contracts with customers 4,512 2,263 2,379 3,673 1,697 993 985 Other revenues Revenues from alternative revenue programs (27 ) 2 (23 ) 7 6 5 (4 ) Other rate-regulated electric revenues (e) 23 10 10 8 5 3 — Other rate-regulated natural gas revenues (e) — — 3 — — — — Total other revenues (4 ) 12 (10 ) 15 11 8 (4 ) Total rate-regulated revenues for reportable segments $ 4,508 $ 2,275 $ 2,369 $ 3,688 $ 1,708 $ 1,001 $ 981 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates of $13 million , $4 million , $5 million, $11 million , $5 million , $5 million and $2 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, in 2019 and $23 million , $5 million , $5 million , $11 million $5 million , $6 million and $2 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, in 2018 . (c) Includes revenues from off-system natural gas sales. (d) Includes operating revenues from affiliates of less than $1 million and $13 million at PECO and BGE in 2019 and 2018 , respectively. (e) Includes late payment charge revenues.

Variable Interest Entities - Na

Variable Interest Entities - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2019	Apr. 01, 2014
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 68
Payment Guarantee [Member] | CENG [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		$ 245
Financial Guarantee [Member] | CENG [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted		165
Exelon Generation Co L L C [Member] | CENG [Member]
Variable Interest Entity [Line Items]
Due from Affiliates		$ 400
Guarantor Obligations, Current Carrying Value	688
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	17
Pepco Holdings LLC [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 68

Variable Interest Entities - As

Variable Interest Entities - Assets and Liabilities of VIES which Creditors or Beneficiaries have no Recourse (Details) - USD ($) $ in Millions		Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 1,683	$ 1,349	$ 1,918	$ 898
Restricted cash and cash equivalents		309	247	240	207
Accounts receivable, net
Customer		4,188	4,607
Other		1,085	1,256
Unamortized energy contract asset		49	48
Inventory, net
Materials and supplies		1,458	1,351
Other current assets		1,296	1,238
Total current assets		12,206	13,360
Property, plant and equipment, net		78,593	76,707
NDT funds		12,706	11,661
Unamortized energy contract asset		353	372
Other Assets, Noncurrent		3,123	1,575
Total assets	[1]	122,738	119,666
Long-term debt due within one year		4,248	1,349
Accounts payable		3,348	3,800
Accrued expenses		1,877	2,112
Unamortized energy contract liabilities		138	149
Other Liabilities, Current		1,425	1,035
Total current liabilities		13,085	11,404
Long-term debt		32,056	34,075
Asset retirement obligations, noncurrent		10,089	9,679
Unamortized energy contract liabilities		368	463
Other Liabilities, Noncurrent		3,123	2,130
Total liabilities	[1]	88,386	86,596
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		168	414
Restricted cash and cash equivalents		76	66
Accounts receivable, net
Customer		163	146
Other		43	23
Unamortized energy contract asset		23	25
Inventory, net
Materials and supplies		222	212
Other current assets		50	52
Total current assets		745	938
Property, plant and equipment, net		6,079	6,188
NDT funds		2,636	2,351
Unamortized energy contract asset		258	274
Other Assets, Noncurrent		69	258
Total noncurrent assets		9,042	9,071
Total assets		9,787	10,009
Long-term debt due within one year		556	87
Accounts payable		148	96
Accrued expenses		58	73
Unamortized energy contract liabilities		10	15
Other Liabilities, Current		30	3
Total current liabilities		802	274
Long-term debt		532	1,072
Asset retirement obligations, noncurrent		2,103	2,165
Unamortized energy contract liabilities		1	1
Other Liabilities, Noncurrent		84	42
Total noncurrent liabilities		2,720	3,280
Total liabilities		3,522	3,554
PP&E - unrestricted asset		41	43
Variable Interest Entity, Consolidated, Liabilities, Recourse		5	5
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		1,019	750	1,187	416
Restricted cash and cash equivalents		126	153	152	138
Accounts receivable, net
Customer		2,587	2,941
Other		337	562
Unamortized energy contract asset		49	49
Inventory, net
Materials and supplies		1,010	963
Other current assets		1,002	883
Total current assets		7,159	8,433
Property, plant and equipment, net		23,591	23,981
NDT funds		12,706	11,661
Unamortized energy contract asset		352	371
Other Assets, Noncurrent		1,915	755
Total assets	[2]	47,984	47,556
Long-term debt due within one year		2,706	906
Accounts payable		1,583	1,847
Accrued expenses		762	898
Unamortized energy contract liabilities		21	31
Other Liabilities, Current		541	279
Total current liabilities		6,344	5,769
Long-term debt		5,018	6,989
Asset retirement obligations, noncurrent		9,855	9,450
Unamortized energy contract liabilities		11	20
Other Liabilities, Noncurrent		1,466	610
Total liabilities	[2]	32,391	32,048
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		168	414
Restricted cash and cash equivalents		73	62
Accounts receivable, net
Customer		163	146
Other		43	23
Unamortized energy contract asset		23	25
Inventory, net
Materials and supplies		222	212
Other current assets		48	49
Total current assets		740	931
Property, plant and equipment, net		6,079	6,188
NDT funds		2,636	2,351
Unamortized energy contract asset		258	274
Other Assets, Noncurrent		52	232
Total noncurrent assets		9,025	9,045
Total assets		9,765	9,976
Long-term debt due within one year		535	66
Accounts payable		148	96
Accrued expenses		57	72
Unamortized energy contract liabilities		10	15
Other Liabilities, Current		30	3
Total current liabilities		780	252
Long-term debt		504	1,025
Asset retirement obligations, noncurrent		2,103	2,165
Unamortized energy contract liabilities		1	1
Other Liabilities, Noncurrent		84	42
Total noncurrent liabilities		2,692	3,233
Total liabilities		3,472	3,485
PP&E - unrestricted asset		41	43
Variable Interest Entity, Consolidated, Liabilities, Recourse		5	5
Pepco Holdings LLC [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		99	124	153	30
Restricted cash and cash equivalents		38	43	42	42
Accounts receivable, net
Customer		512	453
Other		189	177
Inventory, net
Materials and supplies		203	163
Other current assets		50	75
Total current assets		1,578	1,533
Property, plant and equipment, net		13,968	13,446
Other Assets, Noncurrent		356	60
Total assets	[3]	22,576	21,984
Long-term debt due within one year		118	125
Accounts payable		416	496
Accrued expenses		279	256
Unamortized energy contract liabilities		117	119
Other Liabilities, Current		152	123
Total current liabilities		1,515	1,592
Long-term debt		6,376	6,134
Asset retirement obligations, noncurrent		57	52
Unamortized energy contract liabilities		357	442
Other Liabilities, Noncurrent		610	369
Total liabilities	[3]	13,028	12,702
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		3	4
Accounts receivable, net
Customer		0	0
Other		0	0
Unamortized energy contract asset		0	0
Inventory, net
Materials and supplies		0	0
Other current assets		2	3
Total current assets		5	7
Property, plant and equipment, net		0	0
NDT funds		0	0
Unamortized energy contract asset		0	0
Other Assets, Noncurrent		17	26
Total noncurrent assets		17	26
Total assets		22	33
Long-term debt due within one year		21	21
Accounts payable		0	0
Accrued expenses		1	1
Unamortized energy contract liabilities		0	0
Other Liabilities, Current		0	0
Total current liabilities		22	22
Long-term debt		28	47
Asset retirement obligations, noncurrent		0	0
Unamortized energy contract liabilities		0	0
Other Liabilities, Noncurrent		0	0
Total noncurrent liabilities		28	47
Total liabilities		50	69
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		13	7	11	2
Restricted cash and cash equivalents		3	4	$ 7	$ 6
Accounts receivable, net
Customer		142	95
Other		47	55
Inventory, net
Other current assets		7	5
Total current assets		307	240
Property, plant and equipment, net		3,124	2,966
Other Assets, Noncurrent		59	40
Total assets	[4]	3,916	3,699
Long-term debt due within one year		19	18
Accounts payable		139	154
Accrued expenses		40	35
Other Liabilities, Current		11	4
Total current liabilities		347	422
Long-term debt		1,305	1,170
Other Liabilities, Noncurrent		44	27
Total liabilities	[4]	2,648	2,573
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		3	4
Accounts receivable, net
Customer		0	0
Other		0	0
Unamortized energy contract asset		0	0
Inventory, net
Materials and supplies		0	0
Other current assets		0	0
Total current assets		3	4
Property, plant and equipment, net		0	0
NDT funds		0	0
Unamortized energy contract asset		0	0
Other Assets, Noncurrent		15	19
Total noncurrent assets		15	19
Total assets		18	23
Long-term debt due within one year		19	18
Accounts payable		0	0
Accrued expenses		1	1
Unamortized energy contract liabilities		0	0
Other Liabilities, Current		0	0
Total current liabilities		20	19
Long-term debt		26	40
Asset retirement obligations, noncurrent		0	0
Unamortized energy contract liabilities		0	0
Other Liabilities, Noncurrent		0	0
Total noncurrent liabilities		26	40
Total liabilities		$ 46	$ 59
[1]	Exelon’s consolidated assets include $9,465 million and $9,667 million at September 30, 2019 and December 31, 2018 , respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,517 million and $3,548 million at September 30, 2019 and December 31, 2018 , respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 2 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $9,443 million and $9,634 million at September 30, 2019 and December 31, 2018 , respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,467 million and $3,480 million at September 30, 2019 and December 31, 2018 , respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 2 — Variable Interest Entities for additional information.
[3]	PHI’s consolidated total assets include $22 million and $33 million at September 30, 2019 and December 31, 2018 , respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $50 million and $69 million at September 30, 2019 and December 31, 2018 , respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 2 — Variable Interest Entities for additional information.
[4]	ACE’s consolidated total assets include $18 million and $23 million at September 30, 2019 and December 31, 2018 , respectively, of ACE's consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated total liabilities include $46 million and $59 million at September 30, 2019 and December 31, 2018 , respectively, of ACE's consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 2 — Variable Interest Entities for additional information.

Variable Interest Entities - Su

Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Total assets	$ 1,067	$ 1,069
Total liabilities	260	259
Exelon's ownership interest in VIE	201	223
Other ownership interests in VIE	615	587
Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	12	223
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	614	597
Total liabilities	36	37
Exelon's ownership interest in VIE	0	0
Other ownership interests in VIE	587	560
Commercial Agreement Variable Interest Entities [Member] | Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	0	0
Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Total assets	453	472
Total liabilities	224	222
Exelon's ownership interest in VIE	201	223
Other ownership interests in VIE	28	27
Equity Investment VIE [Member] | Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	12	223
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets	1,067	1,069
Total liabilities	260	259
Exelon's ownership interest in VIE	201	223
Other ownership interests in VIE	615	587
Exelon Generation Co L L C [Member] | Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	12	223
Exelon Generation Co L L C [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	614	597
Total liabilities	36	37
Exelon's ownership interest in VIE	0	0
Other ownership interests in VIE	587	560
Exelon Generation Co L L C [Member] | Commercial Agreement Variable Interest Entities [Member] | Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	0	0
Exelon Generation Co L L C [Member] | Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Total assets	453	472
Total liabilities	224	222
Exelon's ownership interest in VIE	201	223
Other ownership interests in VIE	28	27
Exelon Generation Co L L C [Member] | Equity Investment VIE [Member] | Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	$ 12	$ 223

Mergers, Acquisitions and Dis_2

Mergers, Acquisitions and Dispositions - Acquisitions Narrative (Details) - USD ($) $ in Millions	Apr. 04, 2018	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		$ 0	$ 57
Handley [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 62
Exelon Generation Co L L C [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		$ 0	$ 57
Exelon Generation Co L L C [Member] | Handley [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	$ 62

Mergers, Acquisitions and Dis_3

Mergers, Acquisitions and Dispositions - Dispositions Narrative (Details) - USD ($) $ in Millions	Feb. 28, 2018	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2018
Business Dispositions [Line Items]
Assets held for sale		$ 18					$ 904
Liabilities held for sale		11					777
Asset Retirement Obligation, Revision of Estimate		(300)		$ 330		$ 20
Exelon Generation Co L L C [Member]
Business Dispositions [Line Items]
Assets held for sale		18					904
Liabilities held for sale		11					777
Asset Retirement Obligation, Revision of Estimate		(300)		$ 330		$ 0
Oyster Creek [Member]
Business Dispositions [Line Items]
Assets held for sale							897
Liabilities held for sale							777
Oyster Creek [Member] | Exelon Generation Co L L C [Member]
Business Dispositions [Line Items]
Assets held for sale							897
Liabilities held for sale							$ 777
Electrical Contracting Business [Member]
Business Dispositions [Line Items]
Proceeds from Divestiture of Businesses	$ 87
Electrical Contracting Business [Member] | Exelon Generation Co L L C [Member]
Business Dispositions [Line Items]
Proceeds from Divestiture of Businesses	$ 87
Operating Expense [Member]
Business Dispositions [Line Items]
Asset Retirement Obligation, Revision of Estimate		(65)
Operating Expense [Member] | Exelon Generation Co L L C [Member]
Business Dispositions [Line Items]
Asset Retirement Obligation, Revision of Estimate		$ (65)
Operating Expense [Member] | Oyster Creek [Member]
Business Dispositions [Line Items]
Asset Retirement Obligation, Revision of Estimate			$ 9		$ 84
Operating Expense [Member] | Oyster Creek [Member] | Exelon Generation Co L L C [Member]
Business Dispositions [Line Items]
Asset Retirement Obligation, Revision of Estimate			$ 9		$ 84

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Change in Contract with Customer, Asset and Liability (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in Contract with Customer, Asset and Liability [Line Items]
Contract Assets	$ 170	$ 187	$ 283
Contract Liabilities	26	27	35
Consideration (received) due, contract assets	(109)	(146)
Consideration received (due), contract liabilities	65	179
Revenues recognized, contract assets	92	50
Revenues recognized, contract liabilities	(66)	(187)
Exelon Generation Co L L C [Member]
Change in Contract with Customer, Asset and Liability [Line Items]
Contract Assets	170	187	283
Contract Liabilities	48	42	$ 35
Consideration (received) due, contract assets	(109)	(146)
Consideration received (due), contract liabilities	198	465
Revenues recognized, contract assets	92	50
Revenues recognized, contract liabilities	$ (192)	$ (458)

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Performance Obligations (Details) $ in Millions	Sep. 30, 2019USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 156
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01 | Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	215
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	341
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01 | Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	442
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	142
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 | Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	197
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	74
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 | Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	89
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	244
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 | Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	244
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	957
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil) | Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 1,187

Leases Lessee - Narrative (Deta

Leases Lessee - Narrative (Details)	9 Months Ended
	Sep. 30, 2019
Contracted Generation [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Real Estate [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Vehicles & Equipment [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 year
Options to extend the term	3 years
Options to terminate within	2 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	87 years
Options to extend the term	30 years
Options to terminate within	14 years
Exelon Generation Co L L C [Member] | Contracted Generation [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Exelon Generation Co L L C [Member] | Real Estate [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Exelon Generation Co L L C [Member] | Vehicles & Equipment [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Exelon Generation Co L L C [Member] | Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 year
Options to extend the term	3 years
Options to terminate within	2 years
Exelon Generation Co L L C [Member] | Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	37 years
Options to extend the term	30 years
Options to terminate within	2 years
Commonwealth Edison Co [Member] | Real Estate [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Commonwealth Edison Co [Member] | Vehicles & Equipment [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Commonwealth Edison Co [Member] | Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 year
Options to extend the term	5 years
Options to terminate within	4 years
Commonwealth Edison Co [Member] | Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	6 years
Options to extend the term	5 years
Options to terminate within	4 years
PECO Energy Co [Member] | Real Estate [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
PECO Energy Co [Member] | Vehicles & Equipment [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
PECO Energy Co [Member] | Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 year
PECO Energy Co [Member] | Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	15 years
Baltimore Gas and Electric Company [Member] | Real Estate [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Baltimore Gas and Electric Company [Member] | Vehicles & Equipment [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Baltimore Gas and Electric Company [Member] | Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 year
Options to terminate within	3 years
Baltimore Gas and Electric Company [Member] | Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	87 years
Options to terminate within	3 years
Pepco Holdings LLC [Member] | Real Estate [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Pepco Holdings LLC [Member] | Vehicles & Equipment [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Pepco Holdings LLC [Member] | Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 year
Options to extend the term	3 years
Pepco Holdings LLC [Member] | Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	13 years
Options to extend the term	30 years
Potomac Electric Power Company [Member] | Real Estate [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Potomac Electric Power Company [Member] | Vehicles & Equipment [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Potomac Electric Power Company [Member] | Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 year
Options to extend the term	5 years
Potomac Electric Power Company [Member] | Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	13 years
Options to extend the term	5 years
Delmarva Power and Light Company [Member] | Real Estate [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Delmarva Power and Light Company [Member] | Vehicles & Equipment [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Delmarva Power and Light Company [Member] | Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 year
Options to extend the term	3 years
Delmarva Power and Light Company [Member] | Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	13 years
Options to extend the term	30 years
Atlantic City Electric Company [Member] | Real Estate [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Atlantic City Electric Company [Member] | Vehicles & Equipment [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Description	●
Atlantic City Electric Company [Member] | Minimum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	1 year
Atlantic City Electric Company [Member] | Maximum [Member]
Lessee, Lease, Description [Line Items]
Remaining lease terms	8 years

Leases Lessee - Components of L

Leases Lessee - Components of Lease Cost (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2019USD ($)
Schedule of Components of Lease Cost [Line Items]
Operating Lease Costs	$ 97	$ 252
Variable Lease Costs	79	229
Short-term Lease Costs	5	16
Total Lease Costs	181	497
Sublease Income	$ 29	$ 48
Operating Lease, Weighted Average Remaining Lease Term	10 years 1 month 6 days	10 years 1 month 6 days
Operating Lease Weighted Average Discount Rate, Percent	4.50%	4.50%
Exelon Generation Co L L C [Member]
Schedule of Components of Lease Cost [Line Items]
Operating Lease Costs	$ 73	$ 180
Variable Lease Costs	74	214
Short-term Lease Costs	5	16
Total Lease Costs	152	410
Sublease Income	$ 28	$ 42
Operating Lease, Weighted Average Remaining Lease Term	10 years 7 months 6 days	10 years 7 months 6 days
Operating Lease Weighted Average Discount Rate, Percent	4.80%	4.80%
Commonwealth Edison Co [Member]
Schedule of Components of Lease Cost [Line Items]
Operating Lease Costs	$ 1	$ 2
Variable Lease Costs	0	1
Short-term Lease Costs	0	0
Total Lease Costs	$ 1	$ 3
Operating Lease, Weighted Average Remaining Lease Term	4 years 8 months 12 days	4 years 8 months 12 days
Operating Lease Weighted Average Discount Rate, Percent	3.10%	3.10%
PECO Energy Co [Member]
Schedule of Components of Lease Cost [Line Items]
Operating Lease Costs	$ 0	$ 1
Variable Lease Costs	0	0
Short-term Lease Costs	0	0
Total Lease Costs	$ 0	$ 1
Operating Lease, Weighted Average Remaining Lease Term	4 years 3 months 18 days	4 years 3 months 18 days
Operating Lease Weighted Average Discount Rate, Percent	3.30%	3.30%
Baltimore Gas and Electric Company [Member]
Schedule of Components of Lease Cost [Line Items]
Operating Lease Costs	$ 8	$ 25
Variable Lease Costs	1	1
Short-term Lease Costs	0	0
Total Lease Costs	$ 9	$ 26
Operating Lease, Weighted Average Remaining Lease Term	5 years 7 months 6 days	5 years 7 months 6 days
Operating Lease Weighted Average Discount Rate, Percent	3.60%	3.60%
Pepco Holdings LLC [Member]
Schedule of Components of Lease Cost [Line Items]
Operating Lease Costs	$ 12	$ 35
Variable Lease Costs	1	5
Short-term Lease Costs	0	0
Total Lease Costs	13	40
Sublease Income	$ 1	$ 6
Operating Lease, Weighted Average Remaining Lease Term	9 years	9 years
Operating Lease Weighted Average Discount Rate, Percent	4.00%	4.00%
Potomac Electric Power Company [Member]
Schedule of Components of Lease Cost [Line Items]
Operating Lease Costs	$ 3	$ 9
Variable Lease Costs	0	2
Short-term Lease Costs	0	0
Total Lease Costs	$ 3	$ 11
Operating Lease, Weighted Average Remaining Lease Term	9 years 7 months 6 days	9 years 7 months 6 days
Operating Lease Weighted Average Discount Rate, Percent	3.70%	3.70%
Delmarva Power and Light Company [Member]
Schedule of Components of Lease Cost [Line Items]
Operating Lease Costs	$ 3	$ 10
Variable Lease Costs	0	2
Short-term Lease Costs	0	0
Total Lease Costs	3	12
Sublease Income	$ 1	$ 6
Operating Lease, Weighted Average Remaining Lease Term	9 years 6 months	9 years 6 months
Operating Lease Weighted Average Discount Rate, Percent	3.70%	3.70%
Atlantic City Electric Company [Member]
Schedule of Components of Lease Cost [Line Items]
Operating Lease Costs	$ 2	$ 5
Variable Lease Costs	0	1
Short-term Lease Costs	0	0
Total Lease Costs	$ 2	$ 6
Operating Lease, Weighted Average Remaining Lease Term	5 years 3 months 18 days	5 years 3 months 18 days
Operating Lease Weighted Average Discount Rate, Percent	3.30%	3.30%

Leases Lessee - Supplemental Ba

Leases Lessee - Supplemental Balance Sheet Information Related to Lessee Right-of-Use Assets and Lease Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	$ 3,123	$ 1,575
Other current liabilities	1,425	1,035
Other deferred credits and other liabilities	3,123	2,130
Total Operating Lease Liabilities	1,597
Exelon Generation Co L L C [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	1,915	755
Other current liabilities	541	279
Other deferred credits and other liabilities	1,466	610
Total Operating Lease Liabilities	1,119
Commonwealth Edison Co [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	351	395
Other current liabilities	138	96
Other deferred credits and other liabilities	621	630
Total Operating Lease Liabilities	11
PECO Energy Co [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	30	27
Other current liabilities	27	24
Other deferred credits and other liabilities	79	76
Total Operating Lease Liabilities	1
Baltimore Gas and Electric Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	88	5
Other current liabilities	63	27
Other deferred credits and other liabilities	112	73
Total Operating Lease Liabilities	82
Pepco Holdings LLC [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	356	60
Other current liabilities	152	123
Other deferred credits and other liabilities	610	369
Total Operating Lease Liabilities	314
Potomac Electric Power Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	76	15
Other current liabilities	25	42
Other deferred credits and other liabilities	311	275
Total Operating Lease Liabilities	68
Delmarva Power and Light Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	82	6
Other current liabilities	33	7
Other deferred credits and other liabilities	114	50
Total Operating Lease Liabilities	85
Atlantic City Electric Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	59	40
Other current liabilities	11	4
Other deferred credits and other liabilities	44	$ 27
Total Operating Lease Liabilities	24
Contracted Generation [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	542
Total Operating Lease Liabilities	703
Contracted Generation [Member] | Exelon Generation Co L L C [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	542
Total Operating Lease Liabilities	703
Other Deferred Debits and Other Assets [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	1,374
Other Deferred Debits and Other Assets [Member] | Exelon Generation Co L L C [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	926
Other Deferred Debits and Other Assets [Member] | Commonwealth Edison Co [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	10
Other Deferred Debits and Other Assets [Member] | PECO Energy Co [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	2
Other Deferred Debits and Other Assets [Member] | Baltimore Gas and Electric Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	83
Other Deferred Debits and Other Assets [Member] | Pepco Holdings LLC [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	304
Other Deferred Debits and Other Assets [Member] | Potomac Electric Power Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	66
Other Deferred Debits and Other Assets [Member] | Delmarva Power and Light Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	75
Other Deferred Debits and Other Assets [Member] | Atlantic City Electric Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred debits and other assets	24
Other Current Liabilities [Member]
Supplemental Balance Sheet Information [Line Items]
Other current liabilities	242
Other Current Liabilities [Member] | Exelon Generation Co L L C [Member]
Supplemental Balance Sheet Information [Line Items]
Other current liabilities	170
Other Current Liabilities [Member] | Commonwealth Edison Co [Member]
Supplemental Balance Sheet Information [Line Items]
Other current liabilities	3
Other Current Liabilities [Member] | PECO Energy Co [Member]
Supplemental Balance Sheet Information [Line Items]
Other current liabilities	0
Other Current Liabilities [Member] | Baltimore Gas and Electric Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other current liabilities	32
Other Current Liabilities [Member] | Pepco Holdings LLC [Member]
Supplemental Balance Sheet Information [Line Items]
Other current liabilities	35
Other Current Liabilities [Member] | Potomac Electric Power Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other current liabilities	8
Other Current Liabilities [Member] | Delmarva Power and Light Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other current liabilities	11
Other Current Liabilities [Member] | Atlantic City Electric Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other current liabilities	5
Other Deferred Credits and Other Liabilities [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred credits and other liabilities	1,355
Other Deferred Credits and Other Liabilities [Member] | Exelon Generation Co L L C [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred credits and other liabilities	949
Other Deferred Credits and Other Liabilities [Member] | Commonwealth Edison Co [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred credits and other liabilities	8
Other Deferred Credits and Other Liabilities [Member] | PECO Energy Co [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred credits and other liabilities	1
Other Deferred Credits and Other Liabilities [Member] | Baltimore Gas and Electric Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred credits and other liabilities	50
Other Deferred Credits and Other Liabilities [Member] | Pepco Holdings LLC [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred credits and other liabilities	279
Other Deferred Credits and Other Liabilities [Member] | Potomac Electric Power Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred credits and other liabilities	60
Other Deferred Credits and Other Liabilities [Member] | Delmarva Power and Light Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred credits and other liabilities	74
Other Deferred Credits and Other Liabilities [Member] | Atlantic City Electric Company [Member]
Supplemental Balance Sheet Information [Line Items]
Other deferred credits and other liabilities	$ 19

Leases Lessee - Future Minimum

Leases Lessee - Future Minimum Operating Lease Maturity Payments (Details) $ in Millions	Sep. 30, 2019USD ($)
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	$ 65
2020	289
2021	246
2022	179
2023	148
Remaining Years	1,123
Total	2,050
Interest	453
Total Operating Lease Liabilities	1,597
Exelon Generation Co L L C [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	50
2020	203
2021	162
2022	113
2023	100
Remaining Years	837
Total	1,465
Interest	346
Total Operating Lease Liabilities	1,119
Commonwealth Edison Co [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	1
2020	3
2021	3
2022	2
2023	1
Remaining Years	2
Total	12
Interest	1
Total Operating Lease Liabilities	11
PECO Energy Co [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	0
2020	1
2021	0
2022	0
2023	0
Remaining Years	0
Total	1
Interest	0
Total Operating Lease Liabilities	1
Baltimore Gas and Electric Company [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	1
2020	34
2021	31
2022	16
2023	0
Remaining Years	19
Total	101
Interest	19
Total Operating Lease Liabilities	82
Pepco Holdings LLC [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	11
2020	45
2021	43
2022	42
2023	41
Remaining Years	197
Total	379
Interest	65
Total Operating Lease Liabilities	314
Potomac Electric Power Company [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	3
2020	10
2021	9
2022	9
2023	8
Remaining Years	43
Total	82
Interest	14
Total Operating Lease Liabilities	68
Delmarva Power and Light Company [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	2
2020	13
2021	12
2022	12
2023	11
Remaining Years	53
Total	103
Interest	18
Total Operating Lease Liabilities	85
Atlantic City Electric Company [Member]
Schedule of Lessee, Operating Lease, Liability, Maturity [Line Items]
2019	2
2020	5
2021	5
2022	4
2023	4
Remaining Years	6
Total	26
Interest	2
Total Operating Lease Liabilities	$ 24

Leases Lessee - 2018 Schedule o

Leases Lessee - 2018 Schedule of Minimum Future Operating Lease Payments (Details) $ in Millions	Dec. 31, 2018USD ($)
Operating Leases Future Minimum Payments Due [Line Items]
2019	$ 140
2020	149
2021	143
2022	126
2023	97
Remaining Years	723
Total Minimum Future Lease Payments	1,378
Exelon Generation Co L L C [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	33
2020	46
2021	46
2022	47
2023	46
Remaining Years	545
Total Minimum Future Lease Payments	763
Commonwealth Edison Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	7
2020	5
2021	4
2022	4
2023	3
Remaining Years	0
Total Minimum Future Lease Payments	23
PECO Energy Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	5
2020	5
2021	5
2022	5
2023	5
Remaining Years	0
Total Minimum Future Lease Payments	25
Baltimore Gas and Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	35
2020	35
2021	33
2022	18
2023	3
Remaining Years	19
Total Minimum Future Lease Payments	143
Pepco Holdings LLC [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	48
2020	46
2021	43
2022	42
2023	39
Remaining Years	159
Total Minimum Future Lease Payments	377
Potomac Electric Power Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	11
2020	10
2021	9
2022	8
2023	8
Remaining Years	40
Total Minimum Future Lease Payments	86
Delmarva Power and Light Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	14
2020	13
2021	12
2022	12
2023	10
Remaining Years	35
Total Minimum Future Lease Payments	96
Atlantic City Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	7
2020	6
2021	5
2022	5
2023	4
Remaining Years	5
Total Minimum Future Lease Payments	32
Real Estate Leases and Railroad Licenses [Member] | Commonwealth Edison Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total Minimum Future Lease Payments	3
Real Estate Leases and Railroad Licenses [Member] | PECO Energy Co [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total Minimum Future Lease Payments	5
Real Estate Leases and Railroad Licenses [Member] | Baltimore Gas and Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total Minimum Future Lease Payments	1
Real Estate Leases and Railroad Licenses [Member] | Delmarva Power and Light Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
Total Minimum Future Lease Payments	1
Electrical Conduit System [Member] | Baltimore Gas and Electric Company [Member]
Operating Leases Future Minimum Payments Due [Line Items]
2019	26
2020	28
2021	28
2022	$ 14

Leases Lessee - Supplemental Ca

Leases Lessee - Supplemental Cash Flow Information Related to Leases (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)
Supplemental Cash Flow Information [Line Items]
Operating cash flows from operating leases	$ 225
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	70
Exelon Generation Co L L C [Member]
Supplemental Cash Flow Information [Line Items]
Operating cash flows from operating leases	156
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	11
Commonwealth Edison Co [Member]
Supplemental Cash Flow Information [Line Items]
Operating cash flows from operating leases	2
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	6
PECO Energy Co [Member]
Supplemental Cash Flow Information [Line Items]
Operating cash flows from operating leases	0
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	0
Baltimore Gas and Electric Company [Member]
Supplemental Cash Flow Information [Line Items]
Operating cash flows from operating leases	32
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	1
Pepco Holdings LLC [Member]
Supplemental Cash Flow Information [Line Items]
Operating cash flows from operating leases	29
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	20
Potomac Electric Power Company [Member]
Supplemental Cash Flow Information [Line Items]
Operating cash flows from operating leases	7
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	7
Delmarva Power and Light Company [Member]
Supplemental Cash Flow Information [Line Items]
Operating cash flows from operating leases	6
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	9
Atlantic City Electric Company [Member]
Supplemental Cash Flow Information [Line Items]
Operating cash flows from operating leases	4
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 4

Leases Lessor - Narrative (Deta

Leases Lessor - Narrative (Details)	9 Months Ended
	Sep. 30, 2019
Contracted Generation [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Real Estate [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	1 year
Options to extend the term	1 years
Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	84 years
Options to extend the term	79 years
Exelon Generation Co L L C [Member] | Contracted Generation [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Exelon Generation Co L L C [Member] | Real Estate [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Exelon Generation Co L L C [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	1 year
Options to extend the term	1 years
Exelon Generation Co L L C [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	33 years
Options to extend the term	5 years
Commonwealth Edison Co [Member] | Real Estate [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Commonwealth Edison Co [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	1 year
Options to extend the term	5 years
Commonwealth Edison Co [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	18 years
Options to extend the term	79 years
PECO Energy Co [Member] | Real Estate [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
PECO Energy Co [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	1 year
Options to extend the term	5 years
PECO Energy Co [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	84 years
Options to extend the term	50 years
Baltimore Gas and Electric Company [Member] | Real Estate [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Baltimore Gas and Electric Company [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	24 years
Baltimore Gas and Electric Company [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	24 years
Pepco Holdings LLC [Member] | Real Estate [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Pepco Holdings LLC [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	1 year
Options to extend the term	5 years
Pepco Holdings LLC [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	14 years
Options to extend the term	5 years
Potomac Electric Power Company [Member] | Real Estate [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Potomac Electric Power Company [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	2 years
Potomac Electric Power Company [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	7 years
Delmarva Power and Light Company [Member] | Real Estate [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Delmarva Power and Light Company [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	13 years
Delmarva Power and Light Company [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	14 years
Atlantic City Electric Company [Member] | Real Estate [Member]
Lessor, Lease, Description [Line Items]
Lessor, Operating Lease, Description	●
Atlantic City Electric Company [Member] | Minimum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	1 year
Atlantic City Electric Company [Member] | Maximum [Member]
Lessor, Lease, Description [Line Items]
Remaining lease terms	3 years

Leases Lessor - Components of O

Leases Lessor - Components of Operating Lease Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	$ 30	$ 48
Variable Lease Income	80	209
Exelon Generation Co L L C [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	29	44
Variable Lease Income	80	206
Commonwealth Edison Co [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	0	0
Variable Lease Income	0	0
PECO Energy Co [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	0	0
Variable Lease Income	0	0
Baltimore Gas and Electric Company [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	0	0
Variable Lease Income	0	0
Pepco Holdings LLC [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	1	3
Variable Lease Income	0	3
Potomac Electric Power Company [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	0	0
Variable Lease Income	0	0
Delmarva Power and Light Company [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	1	3
Variable Lease Income	0	3
Atlantic City Electric Company [Member]
Schedule of Operating Lease, Lease Income [Line Items]
Operating Lease Income	0	0
Variable Lease Income	$ 0	$ 0

Leases Lessor - Future Minimum

Leases Lessor - Future Minimum Operating Lease Maturity Payments (Details) $ in Millions	Sep. 30, 2019USD ($)
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	$ 4
2020	51
2021	50
2022	50
2023	49
Remaining years	314
Total	518
Exelon Generation Co L L C [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	3
2020	46
2021	45
2022	45
2023	45
Remaining years	271
Total	455
Commonwealth Edison Co [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	0
2020	0
2021	0
2022	0
2023	0
Remaining years	1
Total	1
PECO Energy Co [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	0
2020	0
2021	0
2022	0
2023	0
Remaining years	3
Total	3
Baltimore Gas and Electric Company [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	0
2020	0
2021	0
2022	0
2023	0
Remaining years	1
Total	1
Pepco Holdings LLC [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	1
2020	4
2021	4
2022	5
2023	4
Remaining years	38
Total	56
Potomac Electric Power Company [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	0
2020	0
2021	1
2022	0
2023	0
Remaining years	0
Total	1
Delmarva Power and Light Company [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	1
2020	3
2021	3
2022	4
2023	3
Remaining years	38
Total	52
Atlantic City Electric Company [Member]
Schedule of Lessor, Operating Lease, Payments to be Received, Maturity [Line Items]
2019	0
2020	0
2021	0
2022	0
2023	0
Remaining years	0
Total	$ 0

Regulatory Matters - Narrative

Regulatory Matters - Narrative (Details) - USD ($) $ in Millions	Oct. 29, 2019	Jul. 22, 2019	May 23, 2019	Apr. 18, 2019	Feb. 28, 2019	May 01, 2017	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018
Regulatory Matters Additional Narrative Information [Line Items]
Payments to Acquire Property, Plant, and Equipment							$ 1,687	$ 1,690		$ 5,259	$ 5,497
Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets							80			80
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount						$ 22
Public Utilities, Requested Equity Capital Structure, Percentage		10.35%				11.00%
Revenue										8	6
Payments to Acquire Property, Plant, and Equipment										675	615
Increase (Decrease) in Regulatory Assets										62
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 51							5
Revenue			$ (2)							(16)
Payments to Acquire Property, Plant, and Equipment										1,413	1,540
Increase (Decrease) in Regulatory Assets										122
Commonwealth Edison Co [Member] | Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets							52			52
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										(19)
Revenue										(23)
Payments to Acquire Property, Plant, and Equipment										842	667
Increase (Decrease) in Regulatory Liabilities										(90)
Baltimore Gas and Electric Company [Member] | Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets							16			16
Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Payments to Acquire Property, Plant, and Equipment										1,006	988
Pepco Holdings LLC [Member] | Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets							12			12
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										26
Revenue										11
Payments to Acquire Property, Plant, and Equipment										455	475
Increase (Decrease) in Regulatory Assets										(84)
Increase (Decrease) in Regulatory Liabilities										(71)
Potomac Electric Power Company [Member] | Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets							4			4
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										9
Revenue										(2)
Payments to Acquire Property, Plant, and Equipment				$ 96	$ 338					300	247
Increase (Decrease) in Regulatory Liabilities										(30)
Atlantic City Electric Company [Member] | Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets							2			2
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount										16
Revenue										(1)
Payments to Acquire Property, Plant, and Equipment										245	254
Increase (Decrease) in Regulatory Liabilities										(42)
Delmarva Power and Light Company [Member] | Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets							6			6
Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Payments to Acquire Property, Plant, and Equipment										1,282	1,660
Deferred Income Tax Charge [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets										95
Deferred Income Tax Charge [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities										(40)
Deferred Income Tax Charge [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities										(73)
Deferred Income Tax Charge [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities										(32)
Deferred Income Tax Charge [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities										(29)
Removal Costs [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities										(43)
Clean Energy Legislation [Member] | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Competitive businesses other revenues							$ 21			$ 31
Nuclear Plant [Member] | Exelon Generation Co L L C [Member] | Salem [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Interest, percentage							42.59%			42.59%
Generation commodities and services
Regulatory Matters Additional Narrative Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax							$ 4,499	4,971		$ 13,436	14,387
Generation commodities and services | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax							4,499	$ 4,970		13,436	$ 14,389
Generation commodities and services | Zero Emission Standard [Member] | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax									$ 150
License and Service [Member] | Conowingo [Member]
Regulatory Matters Additional Narrative Information [Line Items]
License Costs							41			41
License and Service [Member] | Conowingo [Member] | Subsequent Event [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Environmental Remediation Expense	$ 14
License and Service [Member] | Conowingo [Member] | Subsequent Event [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Environmental Remediation Expense	11
License and Service [Member] | Conowingo [Member] | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
License Costs							$ 41			41
License and Service [Member] | Conowingo [Member] | Exelon Generation Co L L C [Member] | Subsequent Event [Member] | Maximum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Environmental Remediation Expense	14
License and Service [Member] | Conowingo [Member] | Exelon Generation Co L L C [Member] | Subsequent Event [Member] | Minimum [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Environmental Remediation Expense	$ 11
Energy Efficiency Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets										(34)
Energy Efficiency Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets										186
Renewable Energy Program [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets										32
Electric Distribution Formula Rate Annual Reconciliations [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets										(97)
Under Recovered Energy and Natural Gas Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets										(39)
Under Recovered Energy and Natural Gas Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities										(10)
DC PLUG Charge [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets										(26)
Advanced Metering Infrastructure Legacy Meter Costs [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets										$ (14)

Regulatory Matters Schedule of

Regulatory Matters Schedule of Completed Rate Cases (Details) (Details) - USD ($) $ in Millions

Aug. 12, 2019

May 24, 2019

May 23, 2019

Apr. 08, 2019

Mar. 13, 2019

Jan. 15, 2019

Jan. 04, 2019

Dec. 20, 2018

Dec. 04, 2018

Nov. 19, 2018

Jun. 08, 2018

Apr. 16, 2018

Mar. 29, 2018

Sep. 30, 2019

Dec. 31, 2018

Commonwealth Edison Co [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 53

$ 21

Approved Return on Equity, Percentage

11.50%

10.91%

Commonwealth Edison Co [Member] | Electric Distribution [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ (6)

$ (23)

$ 57

Approved Revenue Requirement Increase (Decrease)

$ (24)

$ (63)

Approved Return on Equity, Percentage

8.69%

PECO Energy Co [Member] | Electricity [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 82

Approved Revenue Requirement Increase (Decrease)

$ 25

Baltimore Gas and Electric Company [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ (10)

Approved Return on Equity, Percentage

10.50%

Baltimore Gas and Electric Company [Member] | Electric Distribution [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 74

Baltimore Gas and Electric Company [Member] | Gas Distribution [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 59

$ 61

Approved Revenue Requirement Increase (Decrease)

$ 43

Approved Return on Equity, Percentage

9.80%

Atlantic City Electric Company [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 11

Approved Return on Equity, Percentage

10.50%

Atlantic City Electric Company [Member] | Electric Distribution [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 122

Approved Revenue Requirement Increase (Decrease)

$ 70

Approved Return on Equity, Percentage

9.60%

Potomac Electric Power Company [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 15

Approved Return on Equity, Percentage

10.50%

MARYLAND | Potomac Electric Power Company [Member] | Electric Distribution [Member]

Regulatory Matters Completed Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 27

Approved Revenue Requirement Increase (Decrease)

$ 10

Approved Return on Equity, Percentage

9.60%

Regulatory Matters Schedule o_2

Regulatory Matters Schedule of Pending Rate Cases (Details) (Details) - USD ($) $ in Millions

Oct. 25, 2019

Aug. 12, 2019

May 30, 2019

May 24, 2019

May 23, 2019

Apr. 08, 2019

Jan. 15, 2019

Jan. 04, 2019

Dec. 04, 2018

Jun. 08, 2018

Apr. 16, 2018

Sep. 30, 2019

Dec. 31, 2022

Dec. 31, 2021

Dec. 31, 2020

Dec. 31, 2018

Potomac Electric Power Company [Member]

Regulatory Matters Pending Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease), Amended

$ 26

Requested Revenue Requirement Increase (Decrease)

15

Commonwealth Edison Co [Member]

Regulatory Matters Pending Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease), Amended

$ 51

5

Requested Revenue Requirement Increase (Decrease)

$ 53

21

Requested Return on Equity, Percentage

8.91%

Baltimore Gas and Electric Company [Member]

Regulatory Matters Pending Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease), Amended

(19)

Requested Revenue Requirement Increase (Decrease)

(10)

Electric Distribution [Member] | Commonwealth Edison Co [Member]

Regulatory Matters Pending Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ (6)

$ (23)

$ 57

Requested Return on Equity, Percentage

8.91%

Approved Revenue Requirement Increase (Decrease)

$ (24)

$ (63)

Requested Return on Distribution Rate Base, Percentage

6.53%

6.53%

Electric Distribution [Member] | Baltimore Gas and Electric Company [Member]

Regulatory Matters Pending Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 74

Requested Return on Equity, Percentage

10.30%

Electric Distribution [Member] | Baltimore Gas and Electric Company [Member] | Subsequent Event [Member]

Regulatory Matters Pending Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 18

Requested Return on Equity, Percentage

4500000000.00%

Gas Distribution [Member] | Baltimore Gas and Electric Company [Member]

Regulatory Matters Pending Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 59

$ 61

Requested Return on Equity, Percentage

10.30%

Approved Revenue Requirement Increase (Decrease)

$ 43

MARYLAND | Electric Distribution [Member] | Potomac Electric Power Company [Member]

Regulatory Matters Pending Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 27

Approved Revenue Requirement Increase (Decrease)

$ 10

DISTRICT OF COLUMBIA | Electric Distribution [Member] | Potomac Electric Power Company [Member]

Regulatory Matters Pending Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 160

Requested Return on Equity, Percentage

10.30%

DISTRICT OF COLUMBIA | Forecast [Member] | Electric Distribution [Member] | Potomac Electric Power Company [Member]

Regulatory Matters Pending Rate Cases [Line Items]

Requested Revenue Requirement Increase (Decrease)

$ 36

$ 40

$ 84

Regulatory Matters - Annual Ele

Regulatory Matters - Annual Electric Transmission Fillings (Details) - USD ($) $ in Millions	May 23, 2019	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
Initial Revenue Requirement Increase (Decrease)	$ 53		$ 21
Annual Reconciliation Increase (Decrease)	(2)		(16)
Total Revenue Requirement Increase (Decrease)	$ 51		$ 5
Allowed Return on Rate Base, Percentage			8.21%
Allowed Return on Equity, Percentage			11.50%	10.91%
Cap on Equity Component of Rate of Return on Common Equity in Federal Energy Regulatory Committee Complaint			55.00%
Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Initial Revenue Requirement Increase (Decrease)			$ (10)
Annual Reconciliation Increase (Decrease)			(23)
Total Revenue Requirement Increase (Decrease)			$ (19)
Allowed Return on Rate Base, Percentage			7.35%
Allowed Return on Equity, Percentage			10.50%
Proposed Capital Expenditure			$ 14
Potomac Electric Power Company [Member]
Public Utilities, General Disclosures [Line Items]
Initial Revenue Requirement Increase (Decrease)			15
Annual Reconciliation Increase (Decrease)			11
Total Revenue Requirement Increase (Decrease)			$ 26
Allowed Return on Rate Base, Percentage			7.75%
Allowed Return on Equity, Percentage			10.50%
Delmarva Power and Light Company [Member]
Public Utilities, General Disclosures [Line Items]
Initial Revenue Requirement Increase (Decrease)			$ 17
Annual Reconciliation Increase (Decrease)			(1)
Total Revenue Requirement Increase (Decrease)			$ 16
Allowed Return on Rate Base, Percentage			7.14%
Allowed Return on Equity, Percentage			10.50%
Atlantic City Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Initial Revenue Requirement Increase (Decrease)			$ 11
Annual Reconciliation Increase (Decrease)			(2)
Total Revenue Requirement Increase (Decrease)			$ 9
Allowed Return on Rate Base, Percentage			7.79%
Allowed Return on Equity, Percentage			10.50%
Clean Energy Legislation [Member] | Exelon Generation Co L L C [Member]
Public Utilities, General Disclosures [Line Items]
Other Operating Income		$ 21	$ 31

Regulatory Matters Energy Effic

Regulatory Matters Energy Efficiency Formula Rate (Details) - Commonwealth Edison Co [Member] - USD ($) $ in Millions	May 23, 2019	Apr. 08, 2019	Dec. 04, 2018	Apr. 16, 2018	Sep. 30, 2019	Dec. 31, 2018
Schedule of Energy Efficiency Formula Rate Updates [Line Items]
Initial Revenue Requirement Increase (Decrease)	$ 53				$ 21
Annual Reconciliation Increase (Decrease)	(2)				(16)
Total Revenue Requirement Increase (Decrease)	$ 51				$ 5
Requested Return on Equity, Percentage	8.91%
Allowed Return on Equity, Percentage					11.50%	10.91%
Allowed Return on Rate Base, Percentage					8.21%
Electric Distribution [Member]
Schedule of Energy Efficiency Formula Rate Updates [Line Items]
Initial Revenue Requirement Increase (Decrease)		$ (6)		$ (23)	$ 57
Requested Return on Distribution Rate Base, Percentage	6.53%					6.53%
Requested Return on Equity, Percentage		8.91%
Allowed Return on Equity, Percentage			8.69%
Allowed Return on Rate Base, Percentage						7.49%

Regulatory Matters - Capitalize

Regulatory Matters - Capitalized Ratemaking Amount Not Recognized (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	$ 59	$ 65
Commonwealth Edison Co [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	4	8
PECO Energy Co [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	0	0
Baltimore Gas and Electric Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	47	49
Pepco Holdings LLC [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	8	8
Potomac Electric Power Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	5	5
Delmarva Power and Light Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	3	3
Atlantic City Electric Company [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	$ 0	$ 0

Asset Impairments - Narrative (

Asset Impairments - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)MW	Sep. 30, 2018USD ($)
Property, Plant and Equipment [Line Items]
Net Income (Loss) Attributable to Noncontrolling Interest	$ (12)	$ 67	$ 56	$ 121
Deferred Income Taxes and Tax Credits			412	97
Impairment of long-lived assets			174	49
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Net Income (Loss) Attributable to Noncontrolling Interest	(13)	$ 66	56	120
Deferred Income Taxes and Tax Credits			201	(278)
Impairment of long-lived assets			174	$ 49
Antelope Valley [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	730		730
Impairment of long-lived assets			$ 0
Antelope Valley [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Capacity Of Facility Of Company Owned Solar Distribution Generation Facilities | MW			242
Long-lived assets	730		$ 730
Impairment of long-lived assets			0
ExGen Renewables IV, LLC [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	1,930		1,930
ExGen Renewables IV, LLC [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	1,930		$ 1,930
Certain Distributed Energy Companies [Member]
Property, Plant and Equipment [Line Items]
Equity Method Investment, Other than Temporary Impairment	164
Net Income (Loss) Attributable to Noncontrolling Interest	96
Deferred Income Taxes and Tax Credits	(46)
Income (Loss) from Equity Method Investments	(15)
Certain Distributed Energy Companies [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Equity Method Investment, Other than Temporary Impairment	164
Net Income (Loss) Attributable to Noncontrolling Interest	96
Deferred Income Taxes and Tax Credits	(46)
Income (Loss) from Equity Method Investments	$ (15)

Early Plant Retirements - Narra

Early Plant Retirements - Narrative (Details)	Sep. 30, 2019
Salem [Member] | Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Jointly Owned Utility Plant, Proportionate Ownership Share	42.59%

Early Plant Retirements - Preta

Early Plant Retirements - Pretax Expense (Details) - Facility Closing [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Three Mile Island [Member]
Accelerated depreciation	$ 71		$ 216
Accelerated nuclear fuel amortization	3		13
Operating and maintenance	39		(44)
Restructuring and Related Cost, Incurred Cost	113		185
TMI,OysterCreek [Member]
Accelerated depreciation		$ 152		$ 441
Accelerated nuclear fuel amortization		18		52
Operating and maintenance		4		32
Restructuring and Related Cost, Incurred Cost		174		525
Exelon Generation Co L L C [Member] | Three Mile Island [Member]
Accelerated depreciation	71		216
Accelerated nuclear fuel amortization	3		13
Operating and maintenance	39		(44)
Restructuring and Related Cost, Incurred Cost	$ 113		$ 185
Exelon Generation Co L L C [Member] | TMI,OysterCreek [Member]
Accelerated depreciation		152		441
Accelerated nuclear fuel amortization		18		52
Operating and maintenance		4		32
Restructuring and Related Cost, Incurred Cost		$ 174		$ 525

Early Plant Retirements - Impli

Early Plant Retirements - Implications of Potential Early Plant Retirement on Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Implications of Potential Early Plant Retirement [Line Items]
Completed plant, net	$ 78,593	$ 76,707
Mystic Generating Station [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory	31
Fuel inventory	5
Completed plant, net	889
Construction work in progress	7
Asset retirement obligation	(2)
Exelon Generation Co L L C [Member]
Implications of Potential Early Plant Retirement [Line Items]
Completed plant, net	23,591	$ 23,981
Exelon Generation Co L L C [Member] | Mystic Generating Station [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory	31
Fuel inventory	5
Completed plant, net	889
Construction work in progress	7
Asset retirement obligation	$ (2)

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Narrative (Details) $ in Millions	Sep. 30, 2019USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities without Readily Determinable Fair Value, Amount	$ 75
Exelon Generation Co L L C [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities without Readily Determinable Fair Value, Amount	75
Fixed Income Securities [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	93
Fixed Income Securities [Member] | 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	93
Middle Market Lending [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	241
Middle Market Lending [Member] | 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	241
Private Equity Funds [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	383
Private Equity Funds [Member] | 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	383
Real Estate Funds [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	388
Real Estate Funds [Member] | 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	$ 388

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities - Fair Value of Financial Liabilities Recorded at Amortized Cost (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt to financing trust	$ 390	$ 390
Spent Nuclear Fuel Obligation, Noncurrent	1,193	1,171
Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	36,304	35,424
Long-term debt to financing trust	390	390
Spent Nuclear Fuel Obligation, Noncurrent	1,193	1,171
Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	40,597	35,869
Long-term debt to financing trust	426	400
Spent Nuclear Fuel Obligation, Noncurrent	1,017	949
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
Long-term debt to financing trust	0	0
Spent Nuclear Fuel Obligation, Noncurrent	0	0
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)	38,056	33,711
Long-term debt to financing trust	0	0
Spent Nuclear Fuel Obligation, Noncurrent	1,017	949
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)	2,541	2,158
Long-term debt to financing trust	426	400
Spent Nuclear Fuel Obligation, Noncurrent	0	0
Exelon Generation Co L L C [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Spent Nuclear Fuel Obligation, Noncurrent	1,193	1,171
Exelon Generation Co L L C [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	8,613	8,793
Spent Nuclear Fuel Obligation, Noncurrent	1,193	1,171
Exelon Generation Co L L C [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	9,360	8,910
Spent Nuclear Fuel Obligation, Noncurrent	1,017	949
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]
Long-term debt (including amounts due within one year)	0	0
Spent Nuclear Fuel Obligation, Noncurrent	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]
Long-term debt (including amounts due within one year)	7,962	7,467
Spent Nuclear Fuel Obligation, Noncurrent	1,017	949
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]
Long-term debt (including amounts due within one year)	1,398	1,443
Spent Nuclear Fuel Obligation, Noncurrent	0	0
Commonwealth Edison Co [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt to financing trust	205	205
Commonwealth Edison Co [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	8,196	8,101
Long-term debt to financing trust	205	205
Commonwealth Edison 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)	9,622	8,390
Long-term debt to financing trust	223	209
Commonwealth Edison 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
Long-term debt to financing trust	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]
Long-term debt (including amounts due within one year)	9,622	8,390
Long-term debt to financing trust	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]
Long-term debt (including amounts due within one year)	0	0
Long-term debt to financing trust	223	209
PECO Energy Co [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt to financing trust	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)	3,404	3,084
Long-term debt to financing trust	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)	3,941	3,207
Long-term debt to financing trust	203	191
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
Long-term debt to financing trust	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)	3,891	3,157
Long-term debt to financing trust	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)	50	50
Long-term debt to financing trust	203	191
Baltimore Gas and Electric Company [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	3,270	2,876
Baltimore Gas and Electric Company [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	3,678	2,950
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]
Long-term debt (including amounts due within one year)	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]
Long-term debt (including amounts due within one year)	3,678	2,950
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]
Long-term debt (including amounts due within one year)	0	0
Pepco Holdings LLC [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	6,494	6,259
Pepco Holdings LLC [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	7,086	6,101
Pepco Holdings LLC [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
Pepco Holdings LLC [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)	5,993	5,436
Pepco Holdings LLC [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)	1,093	665
Potomac Electric Power Company [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	2,860	2,719
Potomac Electric Power Company [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	3,644	3,097
Potomac Electric Power Company [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
Potomac Electric Power Company [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)	3,249	2,901
Potomac Electric Power Company [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)	395	196
Delmarva Power and Light Company [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,495	1,494
Delmarva Power and Light Company [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,669	1,496
Delmarva Power and Light Company [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
Delmarva Power and Light Company [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)	1,437	1,303
Delmarva Power and Light Company [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)	232	193
Atlantic City Electric Company [Member] | Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,324	1,188
Atlantic City Electric Company [Member] | Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	1,500	1,262
Atlantic City Electric Company [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
Atlantic City Electric Company [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)	1,034	987
Atlantic City Electric Company [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)	$ 466	$ 275

Fair Value of Financial Asset_5

Fair Value of Financial Assets and Liabilities - Fair Value Measurements of Assets and Liabilities, Recurring and Nonrecurring (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)	$ 239	$ 475
Derivative Liability, Noncurrent	416	479
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	2
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value		44
Derivative Asset, Notional Amount	864	1,432
Margin Deposit Liabilities		(94)
Margin Deposit Assets	306
Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	347	458
Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	112	80
Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	186	185
Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	176	130
Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	1,719	1,243
Assets, Fair Value Disclosure	16,097	15,557
Deferred Compensation Liability, Current and Noncurrent	(140)	(137)
Total Liabilities	(758)	(1,084)
Fair Value, Net Asset (Liability)	15,339	14,473
Fair Value, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(618)	(947)
Fair Value, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(4,154)	(4,881)
Fair Value, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(148)	(94)
Fair Value, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	3,684	4,028
Fair Value, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	13,038	12,825
Fair Value, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	393	338
Fair Value, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	6,162	5,890
Fair Value, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,804	5,078
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,732	1,823
Fair Value, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,929	2,180
Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	56	50
Fair Value, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	85	149
Fair Value, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,002	876
Fair Value, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	700	680
Fair Value, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	398	329
Fair Value, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	581	510
Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	255	243
Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	49	48
Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	72
Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	13	15
Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	116	108
Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	3,838	4,771
Fair Value, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	210	146
Fair Value, Recurring [Member] | Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(2,963)	(3,671)
Fair Value, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,085	1,246
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	93	57
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	1,719	1,243
Assets, Fair Value Disclosure	6,914	6,573
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(3)	(3)
Fair Value, Net Asset (Liability)	6,911	6,570
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(3)	(3)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(773)	(642)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	770	639
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,213	5,251
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	315	252
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3,121	2,918
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,777	2,081
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,777	2,081
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, 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
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	126	120
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	49	48
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	77	72
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	533	541
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Proprietary Trading [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, Recurring [Member] | Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(677)	(582)
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(144)	(41)
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	324	224
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	3,964	4,155
Deferred Compensation Liability, Current and Noncurrent	(140)	(137)
Total Liabilities	(309)	(592)
Fair Value, Net Asset (Liability)	3,655	3,563
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(169)	(455)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(1,695)	(2,963)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(59)	(73)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	1,585	2,581
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3,594	3,598
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	78	86
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,727	1,591
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,789	1,921
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,473	1,593
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	152	99
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	56	50
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	85	149
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	23	30
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	89	85
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	13	15
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	76	70
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,488	2,760
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	54	69
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,261)	(2,357)
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	281	472
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	304	76
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	1,502	1,396
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(446)	(489)
Fair Value, Net Asset (Liability)	1,056	907
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(446)	(489)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(1,686)	(1,276)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(89)	(21)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	1,329	808
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	514	543
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	259	230
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	259	230
Fair Value, Inputs, Level 3 [Member] | Fair Value, 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
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, 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
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	255	313
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	40	38
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	40	38
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,817	1,470
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	156	77
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,025)	(732)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	948	815
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	3,717	3,433
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	3,717	3,433
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3,717	3,433
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,314	1,381
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	979	846
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, 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
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, 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
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	979	846
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	445	367
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	398	329
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	581	510
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Commodity 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, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)	212	449
Derivative Liability, Noncurrent	163	252
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	2
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value		44
Derivative Asset, Notional Amount	864	1,432
Margin Deposit Liabilities		(94)
Margin Deposit Assets	306
Exelon Generation Co L L C [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	183	283
Exelon Generation Co L L C [Member] | Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	66	39
Exelon Generation Co L L C [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Net assets (liabilities) excluded from nuclear decommissioning trust fund investments	176	130
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	896	581
Assets, Fair Value Disclosure	15,071	14,703
Deferred Compensation Liability, Current and Noncurrent	(37)	(35)
Total Liabilities	(375)	(733)
Fair Value, Net Asset (Liability)	14,696	13,970
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(338)	(698)
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(3,874)	(4,632)
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(148)	(94)
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	3,684	4,028
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	13,038	12,825
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	393	338
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	6,162	5,890
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,804	5,078
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,732	1,823
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,929	2,180
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	56	50
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	85	149
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,002	876
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	700	680
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	398	329
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	581	510
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	52	51
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4	5
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	24	24
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	24	22
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	3,838	4,771
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	210	146
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(2,963)	(3,671)
Exelon Generation Co L L C [Member] | Fair Value, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,085	1,246
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	93	57
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	896	581
Assets, Fair Value Disclosure	5,993	5,820
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(3)	(3)
Fair Value, Net Asset (Liability)	5,990	5,817
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(3)	(3)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(773)	(642)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0	0
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	770	639
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,213	5,251
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	315	252
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3,121	2,918
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,777	2,081
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,777	2,081
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, 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
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	28	29
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4	5
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	24	24
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	533	541
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Proprietary Trading [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, Recurring [Member] | Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(677)	(582)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(144)	(41)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	324	224
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	3,899	4,092
Deferred Compensation Liability, Current and Noncurrent	(37)	(35)
Total Liabilities	(206)	(490)
Fair Value, Net Asset (Liability)	3,693	3,602
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(169)	(455)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(1,695)	(2,963)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(59)	(73)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	1,585	2,581
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3,594	3,598
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	78	86
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,727	1,591
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,789	1,921
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,473	1,593
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | US Treasury and Government [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	152	99
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	56	50
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | State and municipal debt [Domain]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	85	149
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	23	30
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	24	22
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	24	22
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,488	2,760
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	54	69
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,261)	(2,357)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	281	472
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Collateral received from counterparties, net of collateral paid to counterparties	304	76
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	1,462	1,358
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(166)	(240)
Fair Value, Net Asset (Liability)	1,296	1,118
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(166)	(240)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(1,406)	(1,027)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	(89)	(21)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	1,329	808
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	514	543
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	259	230
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	259	230
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, 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
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, 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
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	255	313
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,817	1,470
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	156	77
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Effects of netting and allocation of collateral [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	(1,025)	(732)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	948	815
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	3,717	3,433
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	3,717	3,433
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Commodity Derivative Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0	0
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0	0
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Proprietary Trading Liabilities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0	0
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Effects of Netting and Allocation of Collateral Liabilites [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Total mark-to-market derivative liabilities	0	0
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3,717	3,433
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,314	1,381
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	979	846
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, 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
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Debt Security, Government, Non-US [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, 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
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	979	846
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	445	367
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	398	329
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	581	510
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Exelon Generation Co L L C [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Economic 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 Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Proprietary Trading [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 Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Effects of netting and allocation of collateral [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 Measured at Net Asset Value Per Share [Member] | Fair Value, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	0	0
Commonwealth Edison Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)	27	26
Derivative Liability, Noncurrent	253	223
Commonwealth Edison Co [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	76	93
Commonwealth Edison Co [Member] | Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	31	28
Commonwealth Edison Co [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	171	166
Commonwealth Edison Co [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	264	209
Assets, Fair Value Disclosure	264	209
Total mark-to-market derivative liabilities	(280)	(249)
Deferred Compensation Liability, Current and Noncurrent	(7)	(6)
Total Liabilities	(287)	(255)
Fair Value, Net Asset (Liability)	(23)	(46)
Commonwealth Edison Co [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	264	209
Assets, Fair Value Disclosure	264	209
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	264	209
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	0	0
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	(7)	(6)
Total Liabilities	(7)	(6)
Fair Value, Net Asset (Liability)	(7)	(6)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	0	0
Total mark-to-market derivative liabilities	(280)	(249)
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(280)	(249)
Fair Value, Net Asset (Liability)	(280)	(249)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
PECO Energy Co [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	23	24
PECO Energy Co [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	207	111
Assets, Fair Value Disclosure	226	128
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	(8)	(10)
Total Liabilities	(8)	(10)
Fair Value, Net Asset (Liability)	218	118
PECO Energy Co [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	19	17
PECO Energy Co [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	8	7
PECO Energy Co [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	11	10
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	207	111
Assets, Fair Value Disclosure	215	118
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	215	118
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	8	7
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	8	7
PECO Energy Co [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	11	10
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	(8)	(10)
Total Liabilities	(8)	(10)
Fair Value, Net Asset (Liability)	3	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	11	10
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	11	10
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	0	0
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
PECO Energy Co [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	8	7
Baltimore Gas and Electric Company [Member] | Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	1	2
Baltimore Gas and Electric Company [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	122	4
Assets, Fair Value Disclosure	129	10
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	(5)	(5)
Total Liabilities	(5)	(5)
Fair Value, Net Asset (Liability)	124	5
Baltimore Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7	6
Baltimore Gas and Electric Company [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7	6
Baltimore Gas and Electric Company [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	122	4
Assets, Fair Value Disclosure	129	10
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	129	10
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7	6
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	7	6
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	0	0
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	(5)	(5)
Total Liabilities	(5)	(5)
Fair Value, Net Asset (Liability)	(5)	(5)
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	0	0
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity 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, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Pepco Holdings LLC [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	45	39
Pepco Holdings LLC [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	15	19
Pepco Holdings LLC [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	107	147
Assets, Fair Value Disclosure	240	277
Deferred Compensation Liability, Current and Noncurrent	(19)	(21)
Total Liabilities	(19)	(21)
Fair Value, Net Asset (Liability)	221	256
Pepco Holdings LLC [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	133	130
Pepco Holdings LLC [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	43	42
Pepco Holdings LLC [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	13	13
Pepco Holdings LLC [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	13	15
Pepco Holdings LLC [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	64	60
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	107	147
Assets, Fair Value Disclosure	163	202
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	163	202
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	56	55
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	43	42
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	13	13
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	37	37
Deferred Compensation Liability, Current and Noncurrent	(19)	(21)
Total Liabilities	(19)	(21)
Fair Value, Net Asset (Liability)	18	16
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	37	37
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	13	15
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	24	22
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	40	38
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	40	38
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	40	38
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	40	38
Potomac Electric Power Company [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	18	15
Potomac Electric Power Company [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	34	38
Assets, Fair Value Disclosure	144	143
Deferred Compensation Liability, Current and Noncurrent	(2)	(3)
Total Liabilities	(2)	(3)
Fair Value, Net Asset (Liability)	142	140
Potomac Electric Power Company [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	110	105
Potomac Electric Power Company [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	43	41
Potomac Electric Power Company [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3	5
Potomac Electric Power Company [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	64	59
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	34	38
Assets, Fair Value Disclosure	77	79
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	77	79
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	43	41
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	43	41
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	27	27
Deferred Compensation Liability, Current and Noncurrent	(2)	(3)
Total Liabilities	(2)	(3)
Fair Value, Net Asset (Liability)	25	24
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	27	27
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	3	5
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	24	22
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	40	37
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	40	37
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	40	37
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	40	37
Delmarva Power and Light Company [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	11	8
Delmarva Power and Light Company [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	16
Assets, Fair Value Disclosure	0	16
Deferred Compensation Liability, Current and Noncurrent	0	(1)
Total Liabilities	0	(1)
Fair Value, Net Asset (Liability)	0	15
Delmarva Power and Light Company [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	16
Assets, Fair Value Disclosure	0	16
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	0	16
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	(1)
Total Liabilities	0	(1)
Fair Value, Net Asset (Liability)	0	(1)
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Delmarva Power and Light Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	13	7
Atlantic City Electric Company [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	15	19
Atlantic City Electric Company [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	18	23
Assets, Fair Value Disclosure	18	23
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	18	23
Atlantic City Electric Company [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	18	23
Assets, Fair Value Disclosure	18	23
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	18	23
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	0	0
Assets, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Atlantic City Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Maturity Less than 30 Days [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative, Collateral, Right to Reclaim Cash	85	50
Maturity Less than 30 Days [Member] | Exelon Generation Co L L C [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative, Collateral, Right to Reclaim Cash	$ 85	$ 50

Fair Value of Financial Asset_6

Fair Value of Financial Assets and Liabilities - Fair Value Assets Liabilities Measured On Recurring Basis Unobservable Input Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 1,179	$ 1,106	$ 907	$ 966
Total realized / unrealized gains (losses)
Included in net income	(171)	(259)	(125)	(186)
Included in noncurrent payables to affiliates	0	0	0
Included in regulatory assets	4	(11)	1	(3)
Change in collateral	41	(44)	227	14
Purchases, sales, issuances and settlements
Purchases	53	96	163	215
Sales	(22)		(23)	(3)
Settlements	(18)	(29)	(88)	(103)
Transfers into Level 3	1	3	5	(21)
Transfers out of Level 3	(11)	(6)	(11)	(23)
Ending Balance	1,056	856	1,056	856
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(18)	(105)	173	154
Fair Value, Inputs, Level 3 [Member] | Consolidation, Eliminations [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	0	0	0	0
Total realized / unrealized gains (losses)
Included in net income	0	0	0	0
Included in noncurrent payables to affiliates	(11)	4	(32)
Included in regulatory assets	11	(4)	32	0
Change in collateral	0		0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0		0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	0	0	0	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0	0	0
Exelon Generation Co L L C [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings	153	155	298	347
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	1,412	1,322	1,118	1,200
Total realized / unrealized gains (losses)
Included in net income	(171)	(260)	(127)	(189)
Included in noncurrent payables to affiliates	11	(4)	32
Included in regulatory assets	0	0	0	0
Change in collateral	41	(44)	227	14
Purchases, sales, issuances and settlements
Purchases	53	96	163	215
Sales	(22)		(23)	(3)
Settlements	(18)	(29)	(88)	(115)
Transfers into Level 3	1	3	5	(21)
Transfers out of Level 3	(11)	(6)	(11)	(23)
Ending Balance	1,296	1,078	1,296	1,078
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(18)	(105)	171	154
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Nuclear Decommissioning Trust Fund Investments [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	539	585	543	648
Total realized / unrealized gains (losses)
Included in net income	2	(1)	5	(1)
Included in noncurrent payables to affiliates	11	(4)	32
Included in regulatory assets	0	0	0	0
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	1	15	43	34
Sales	(21)		(21)	0
Settlements	(18)	(29)	(88)	(115)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	514	566	514	566
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	2	(1)	5	(5)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	873	737	575	552
Total realized / unrealized gains (losses)
Included in net income	(173)	(259)	(132)	(188)
Included in noncurrent payables to affiliates	0	0	0
Included in regulatory assets	0	0		0
Change in collateral	41	(44)	227	14
Purchases, sales, issuances and settlements
Purchases	52	81	120	181
Sales	(1)		(2)	(3)
Settlements	0	0	0	0
Transfers into Level 3	1	3	5	(21)
Transfers out of Level 3	(11)	(6)	(11)	(23)
Ending Balance	782	512	782	512
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(20)	(104)	166	159
Commonwealth Edison Co [Member] | Derivative [Member] | Interest Rate Swap [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Realized Investment Gains (Losses)	4	3	17	12
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	(273)	(252)	(249)	(256)
Total realized / unrealized gains (losses)
Included in net income	0	0	0	0
Included in noncurrent payables to affiliates	0	0	0
Included in regulatory assets	(7)	(7)	(31)	(3)
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0		0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	(280)	(259)	(280)	(259)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Period Increase (Decrease)	(7)	4	(31)	(9)
Pepco Holdings LLC [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	40	36	38	22
Total realized / unrealized gains (losses)
Included in net income	0	1	2	3
Included in noncurrent payables to affiliates	0	0	0
Included in regulatory assets	0	0	0	0
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0		0	0
Settlements	0	0	0	12
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	40	37	40	37
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0	2	0
Potomac Electric Power Company [Member] | Fair Value, Inputs, Level 3 [Member] | 6311 Life Insurance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	40	36	38	22
Total realized / unrealized gains (losses)
Included in net income	0	1	2	3
Included in noncurrent payables to affiliates	0	0	0	0
Included in regulatory assets	0	0	0	0
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	12
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0
Ending Balance	40	37	40	37
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 0	$ 0	$ 2	$ 0

Fair Value of Financial Asset_7

Fair Value of Financial Assets and Liabilities - Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
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	$ 171	$ 259	$ 125	$ 186
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(18)	(105)	173	154
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	(25)	(176)	122	(32)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	99	(64)	368	174
Purchased Power And Fuel [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	(148)	(83)	(254)	(156)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(119)	(40)	(202)	(15)
Operating and Maintenance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	1	0	3
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0	2	0
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	(1)	5	(1)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	2	(1)	5	(5)
Exelon Generation Co L L C [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	171	260	127	189
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(18)	(105)	171	154
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	(25)	(176)	122	(32)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	99	(64)	368	174
Exelon Generation Co L L C [Member] | Purchased Power And Fuel [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	(148)	(83)	(254)	(156)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(119)	(40)	(202)	(15)
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	(1)	5	(1)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	2	(1)	5	(5)
Pepco Holdings LLC [Member] | Operating and Maintenance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	1	0	3
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0	2	0
Potomac Electric Power Company [Member] | Operating and Maintenance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	1	0	3
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 0	$ 0	$ 2	$ 0

Fair Value of Financial Asset_8

Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2019USD ($)	Dec. 31, 2018USD ($)
Fair Value, Inputs, Level 3 [Member]
Derivatives Fair Value Footnotes [Abstract]
Cash Collateral Posted	$ 304,000,000	$ 76,000,000
Fair Value, Inputs, Level 3 [Member] | Economic Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	411,000,000	443,000,000
Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ (280,000,000)	$ (249,000,000)
Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	11	12
Forward gas price assets	1.36	0.78
Forward heat rate	900.00%	1000.00%
Derivative Asset (Liability) Net, Measurement Input	0.04	0.04
Fair Value Inputs Renewable Factor	87.00%	86.00%
Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	167	174
Forward gas price assets	10.82	12.38
Forward heat rate	1000.00%	1100.00%
Derivative Asset (Liability) Net, Measurement Input	0.07	0.08
Fair Value Inputs Renewable Factor	119.00%	120.00%
Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Option Model Valuation Technique [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	0.09	0.10
Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Option Model Valuation Technique [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	2	2.77
Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 67,000,000	$ 56,000,000
Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	17	14
Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	167	174
Exelon Generation Co L L C [Member]
Derivatives Fair Value Footnotes [Abstract]
Cash Collateral Posted	$ 18,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives Fair Value Footnotes [Abstract]
Cash Collateral Posted	304,000,000	$ 76,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Economic Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 411,000,000	$ 443,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	11	12
Forward gas price assets	1.36	0.78
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	167	174
Forward gas price assets	10.82	12.38
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Option Model Valuation Technique [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	0.09	0.10
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Option Model Valuation Technique [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	2	2.77
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 67,000,000	$ 56,000,000
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	17	14
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	167	174
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	$ (280,000,000)	$ (249,000,000)
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward heat rate	900.00%	1000.00%
Derivative Asset (Liability) Net, Measurement Input	0.04	0.04
Fair Value Inputs Renewable Factor	87.00%	86.00%
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward heat rate	1000.00%	1100.00%
Derivative Asset (Liability) Net, Measurement Input	0.07	0.08
Fair Value Inputs Renewable Factor	119.00%	120.00%

Derivative Financial Instrume_3

Derivative Financial Instruments - Summary of Derivative Fair Value Balances (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Mark-to-market derivatives assets	$ 601	$ 804
Derivative Asset, Noncurrent	487	452
Derivative Liability, Current	(239)	(475)
Derivative Liability, Noncurrent	(416)	(479)
Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivatives assets	602	801
Derivative Asset, Noncurrent	483	445
Total mark-to-market derivative assets	1,085	1,246
Derivative Liability, Current	(224)	(473)
Derivative Liability, Noncurrent	(394)	(474)
Total mark-to-market derivative liabilities	(618)	(947)
Total mark-to-market derivative net assets (liabilities)	467	299
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivatives assets	602	804
Derivative Asset, Noncurrent	483	452
Derivative Liability, Current	(212)	(449)
Derivative Liability, Noncurrent	(163)	(252)
Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivatives assets	602	801
Derivative Asset, Noncurrent	483	445
Total mark-to-market derivative assets	1,085	1,246
Derivative Liability, Current	(197)	(447)
Derivative Liability, Noncurrent	(141)	(251)
Total mark-to-market derivative liabilities	(338)	(698)
Total mark-to-market derivative net assets (liabilities)	747	548
Commonwealth Edison Co [Member]
Derivative [Line Items]
Derivative Liability, Current	(27)	(26)
Derivative Liability, Noncurrent	(253)	(223)
Collateral [Member] | Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivatives assets	212	121
Derivative Asset, Noncurrent	104	51
Total mark-to-market derivative assets	316	172
Derivative Liability, Current	249	125
Derivative Liability, Noncurrent	156	60
Total mark-to-market derivative liabilities	405	185
Total mark-to-market derivative net assets (liabilities)	721	357
Netting [Member] | Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivatives assets	(2,205)	(2,930)
Derivative Asset, Noncurrent	(1,074)	(913)
Total mark-to-market derivative assets	(3,279)	(3,843)
Derivative Liability, Current	2,205	2,931
Derivative Liability, Noncurrent	1,074	912
Total mark-to-market derivative liabilities	3,279	3,843
Total mark-to-market derivative net assets (liabilities)	0	0
Not Designated as Hedging Instrument, Economic Hedge [Member] | Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivatives assets	2,452	3,505
Derivative Asset, Noncurrent	1,386	1,266
Total mark-to-market derivative assets	3,838	4,771
Derivative Liability, Current	(2,550)	(3,429)
Derivative Liability, Noncurrent	(1,324)	(1,203)
Total mark-to-market derivative liabilities	(3,874)	(4,632)
Total mark-to-market derivative net assets (liabilities)	(36)	139
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commonwealth Edison Co [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivatives assets	0	0
Derivative Asset, Noncurrent	0	0
Total mark-to-market derivative assets	0	0
Derivative Liability, Current	(27)	(26)
Derivative Liability, Noncurrent	(253)	(223)
Total mark-to-market derivative liabilities	(280)	(249)
Total mark-to-market derivative net assets (liabilities)	(280)	(249)
Not Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivatives assets	143	105
Derivative Asset, Noncurrent	67	41
Total mark-to-market derivative assets	210	146
Derivative Liability, Current	(101)	(74)
Derivative Liability, Noncurrent	(47)	(20)
Total mark-to-market derivative liabilities	(148)	(94)
Total mark-to-market derivative net assets (liabilities)	62	52
Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member] | Other Current Assets [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Amount Offset Against Collateral	$ 306	$ (94)

Derivative Financial Instrume_4

Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			$ (96)	$ (67)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			(102)	(73)
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 31	$ 74	(62)	(103)
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Operating Revenue [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	76	8	65	(99)
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Purchased Power And Fuel [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ (45)	$ 66	$ (127)	$ (4)

Derivative Financial Instrume_5

Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) - Exelon Generation Co L L C [Member] $ in Millions	Sep. 30, 2019USD ($)
Derivative [Line Items]
Cash Collateral Posted	$ 18
Financial institutions	1
Investor-owned utilities, marketers and power producers	875
Energy Cooperatives And Municipalities	255
Other	35
Letters Of Credit Posted	55
Total Exposure Before Credit Collateral [Member]
Derivative [Line Items]
Investment grade	693
Non-investment grade	74
No external ratings - internally rated - investment grade	297
No external ratings - internally rated - non-investment grade	175
Total	1,239
Credit Collateral [Member]
Derivative [Line Items]
Investment grade	10
Non-investment grade	38
No external ratings - internally rated - investment grade	1
No external ratings - internally rated - non-investment grade	24
Total	73
Net Exposure [Member]
Derivative [Line Items]
Investment grade	683
Non-investment grade	36
No external ratings - internally rated - investment grade	296
No external ratings - internally rated - non-investment grade	151
Total	1,166
Number Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Investment grade	0
Non-investment grade
No external ratings - internally rated - investment grade
No external ratings - internally rated - non-investment grade
Total	0
Net Exposure Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Investment grade	0
Non-investment grade
No external ratings - internally rated - investment grade
No external ratings - internally rated - non-investment grade
Total	$ 0

Derivative Financial Instrume_6

Derivative Financial Instruments - Summary of Credit Risk Related Contingent Features (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Aggregate fair value of derivatives with credit-risk-related contingent features	$ (1,249)	$ (1,723)
Offsetting fair value of in-the-money contracts under master netting agreements	947	1,105
Net liability position after contractual right of offset	$ (302)	$ (618)

Derivative Financial Instrume_7

Derivative Financial Instruments - Narrative (Details) MWh in Millions, $ in Millions	1 Months Ended	9 Months Ended
	Jun. 30, 2012MWh	Sep. 30, 2019USD ($)	Dec. 31, 2018USD ($)
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		$ 1,481	$ 2,104
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		1,481	2,104
Commonwealth Edison Co [Member]
Derivative [Line Items]
Long-term Purchase Commitment, Minimum Energy Volume Required | MWh	1.3
Delmarva Power and Light Company [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		11
Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		26
PECO Energy Co [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		$ 28
Minimum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months		96.00%
Expected Generation Hedged In Year Two		84.00%
Expected generation Hedged In Year Three		54.00%
Maximum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months		99.00%
Expected Generation Hedged In Year Two		87.00%
Expected generation Hedged In Year Three		57.00%
Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		$ 68
PECO Energy Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from affiliated electric and gas utility		30
Baltimore Gas And Electric Company Affiliate [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from affiliated electric and gas utility		32
Potomac Electric Power Company [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		39
Delmarva Power and Light Company [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		15
Atlantic City Electric Company [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Net receivable from electric utility		8
Not Designated as Hedging Instrument, Economic Hedge [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount		1,371	1,420
Not Designated as Hedging Instrument, Economic Hedge [Member] | Interest Rate Swap [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Notional Amount		571	620
Not Designated as Hedging Instrument, Economic Hedge [Member] | Foreign Exchange Contract [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Notional Amount		$ 257	$ 268

Derivative Financial Instrume_8

Derivative Financial Instruments Derivative Financial Instruments - Summary of Cash Collateral and Letters of Credit (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 787	$ 418
Derivative, Collateral, Right to Reclaim Securities	273	367
Derivative, Collateral, Obligation to Return Cash	96	47
Derivative, Collateral, Obligation to Return Securities	58	44
Incremental Collateral For Loss Of Investment Grade Credit Rating	1,481	2,104
Exelon Generation Co L L C [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Collateral, Right to Reclaim Cash	787	418
Derivative, Collateral, Right to Reclaim Securities	273	367
Derivative, Collateral, Obligation to Return Cash	96	47
Derivative, Collateral, Obligation to Return Securities	58	44
Incremental Collateral For Loss Of Investment Grade Credit Rating	$ 1,481	$ 2,104

Debt and Credit Agreements - Na

Debt and Credit Agreements - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)
Corporate, Non-Segment [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	$ 500
Debt Instrument, Interest Rate Terms	LIBOR plus 0.95%
Exelon Generation Co L L C [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 100
DOE Project Financing, 2.82% January 5, 2037 [Member] | Non Recourse Debt [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	646
Non-Recourse Debt	495
DOE Project Financing, 2.82% January 5, 2037 [Member] | Exelon Generation Co L L C [Member] | Non Recourse Debt [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	646
Non-Recourse Debt	495
ExGenRenewablesIVNov2024 [Member] | Non Recourse Debt [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	850
Non-Recourse Debt	796
ExGenRenewablesIVNov2024 [Member] | Exelon Generation Co L L C [Member] | Non Recourse Debt [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	850
Non-Recourse Debt	$ 796

Debt and Credit Agreements - Co

Debt and Credit Agreements - Commercial Paper Borrowings (Details) - Commercial Paper [Member] - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 519	$ 89
Average Interest Rate on Commercial Paper Borrowings	2.50%	2.15%
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 0	$ 0
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 387	$ 0
Average Interest Rate on Commercial Paper Borrowings	2.51%	2.14%
PECO Energy Co [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 0	$ 0
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 0	$ 35
Average Interest Rate on Commercial Paper Borrowings	2.49%	2.18%
Pepco Holdings LLC [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 132	$ 54
Average Interest Rate on Commercial Paper Borrowings	2.52%	2.15%
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 12	$ 40
Average Interest Rate on Commercial Paper Borrowings	2.61%	2.24%
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 57	$ 0
Average Interest Rate on Commercial Paper Borrowings	2.42%	2.07%
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 63	$ 14
Average Interest Rate on Commercial Paper Borrowings	2.57%	2.21%

Debt and Credit Agreements - Is

Debt and Credit Agreements - Issuance of Long-Term Debt (Details) $ in Millions	Sep. 30, 2019USD ($)
Exelon Generation Co L L C [Member] | EEPF395Aug2020 [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Interest Rate	3.95%
Debt Instrument, Face Amount	$ 4
Exelon Generation Co L L C [Member] | EEPF346May2020 [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Interest Rate	3.46%
Debt Instrument, Face Amount	$ 39
Commonwealth Edison Co [Member] | FMB400Mar2049 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	4.00%
Debt Instrument, Face Amount	$ 400
PECO Energy Co [Member] | FRMB300Sep2049 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.00%
Debt Instrument, Face Amount	$ 325
Baltimore Gas and Electric Company [Member] | SN320Sep2049 [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Interest Rate	3.20%
Debt Instrument, Face Amount	$ 400
Potomac Electric Power Company [Member] | FMB345Jun2029 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.45%
Debt Instrument, Face Amount	$ 150
Potomac Electric Power Company [Member] | Medco170Sep2022 [Member] | Tax-exempt Money Market Funds [Member]
Debt Instrument [Line Items]
Interest Rate	1.70%
Debt Instrument, Face Amount	$ 110
Atlantic City Electric Company [Member] | FMB350May2029 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.50%
Debt Instrument, Face Amount	$ 100
Atlantic City Electric Company [Member] | FMB414May2049 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	4.14%
Debt Instrument, Face Amount	$ 50

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	Jun. 05, 2019	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits, Period Increase (Decrease)			$ (33)
Effective income tax rate		15.60%		14.50%	20.70%	11.60%
Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		17.40%		20.10%	28.60%	13.80%
Commonwealth Edison Co [Member]
Income Tax Additional Narrative Information [Line Items]
Unrecognized Tax Benefits, Period Increase (Decrease)			$ (2)
Effective income tax rate		18.40%		21.20%	19.30%	21.10%
PECO Energy Co [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		9.10%		(1.60%)	11.10%	(1.50%)
Baltimore Gas and Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		17.90%		22.20%	18.40%	19.60%
Pepco Holdings LLC [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		6.90%		2.10%	5.70%	7.70%
Potomac Electric Power Company [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		4.90%		(2.30%)	4.00%	3.90%
Delmarva Power and Light Company [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		13.20%		13.20%	12.10%	15.90%
Atlantic City Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		3.10%		11.60%	2.20%	13.60%
ILLINOIS
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate	10.49%				9.50%

Income Taxes - Reconciliation t

Income Taxes - Reconciliation to Effective Tax Rate (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.40%	(1.20%)	5.10%	1.70%
Qualified nuclear decommissioning trust fund income	3.20%	2.40%	5.30%	0.90%
Amortization of investment tax credit, including deferred taxes on basis difference	(4.10%)	(0.60%)	(1.90%)	(0.90%)
Plant basis differences	(1.70%)	(2.50%)	(1.60%)	(2.70%)
Production tax credits and other credits	(1.20%)	(1.20%)	(1.00%)	(1.80%)
Noncontrolling interests	(2.20%)	(1.10%)	(1.00%)	(1.10%)
Excess deferred tax amortization	(6.50%)	(6.80%)	(6.00%)	(6.10%)
Tax Cuts and Jobs Act of 2017		1.30%		0.20%
Other	0.70%	3.20%	0.80%	0.40%
Effective income tax rate	15.60%	14.50%	20.70%	11.60%
Exelon Generation Co L L C [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	5.20%	(9.00%)	4.20%	(2.60%)
Qualified nuclear decommissioning trust fund income	7.10%	5.80%	11.90%	2.60%
Amortization of investment tax credit, including deferred taxes on basis difference	(8.90%)	(1.10%)	(4.00%)	(2.20%)
Plant basis differences	0.00%	0.00%	0.00%	0.00%
Production tax credits and other credits	(2.70%)	(2.90%)	(2.10%)	(5.10%)
Noncontrolling interests	(4.80%)	(2.80%)	(2.30%)	(3.20%)
Excess deferred tax amortization	0.00%	0.00%	0.00%	0.00%
Tax Cuts and Jobs Act of 2017		3.50%		1.30%
Other	0.50%	5.60%	(0.10%)	2.00%
Effective income tax rate	17.40%	20.10%	28.60%	13.80%
Commonwealth Edison Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	8.10%	8.30%	8.20%	8.20%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.20%)	(0.20%)	(0.20%)
Plant basis differences	(1.00%)	(0.30%)	(0.70%)	(0.10%)
Production tax credits and other credits	0.00%	(0.10%)	0.00%	(0.10%)
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(9.90%)	(7.80%)	(9.20%)	(7.60%)
Tax Cuts and Jobs Act of 2017		0.00%		(0.20%)
Other	0.40%	0.30%	0.20%	0.10%
Effective income tax rate	18.40%	21.20%	19.30%	21.10%
PECO Energy Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	(0.30%)	(3.60%)	0.00%	(3.60%)
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	0.00%	(0.10%)	0.00%	(0.10%)
Plant basis differences	(7.50%)	(15.20%)	(6.80%)	(15.40%)
Production tax credits and other credits	0.00%	0.00%	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(3.60%)	(4.60%)	(2.90%)	(3.40%)
Tax Cuts and Jobs Act of 2017		0.00%		0.00%
Other	(0.50%)	0.90%	(0.20%)	0.00%
Effective income tax rate	9.10%	(1.60%)	11.10%	(1.50%)
Baltimore Gas and Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.30%	7.30%	6.40%	6.60%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	0.00%	(0.10%)	(0.10%)
Plant basis differences	(1.10%)	(0.80%)	(1.10%)	(0.70%)
Production tax credits and other credits	0.00%	0.00%	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(8.00%)	(7.90%)	(7.90%)	(8.10%)
Tax Cuts and Jobs Act of 2017		0.00%		0.00%
Other	(0.20%)	2.60%	0.10%	0.90%
Effective income tax rate	17.90%	22.20%	18.40%	19.60%
Pepco Holdings LLC [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	4.80%	0.20%	4.80%	2.70%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.20%)	(0.20%)	(0.20%)
Plant basis differences	(1.80%)	(2.00%)	(1.80%)	(1.90%)
Production tax credits and other credits	0.00%	0.00%	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(17.70%)	(17.70%)	(18.60%)	(14.50%)
Tax Cuts and Jobs Act of 2017		0.20%		0.30%
Other	0.80%	0.60%	0.50%	0.30%
Effective income tax rate	6.90%	2.10%	5.70%	7.70%
Potomac Electric Power Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	1.90%	1.00%	2.00%	2.40%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.10%)	(0.10%)	(0.10%)
Plant basis differences	(2.60%)	(3.40%)	(2.30%)	(2.90%)
Production tax credits and other credits	0.00%	0.00%	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(16.30%)	(21.20%)	(17.30%)	(16.50%)
Tax Cuts and Jobs Act of 2017		0.10%		0.00%
Other	1.00%	0.30%	0.70%	0.00%
Effective income tax rate	4.90%	(2.30%)	4.00%	3.90%
Delmarva Power and Light Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.60%	6.60%	6.70%	6.50%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.30%)	(0.20%)	(0.30%)
Plant basis differences	(0.60%)	(0.70%)	(0.60%)	(0.70%)
Production tax credits and other credits	0.00%	0.00%	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(13.50%)	(14.00%)	(15.00%)	(11.00%)
Tax Cuts and Jobs Act of 2017		0.00%		0.00%
Other	(0.10%)	0.60%	0.20%	0.40%
Effective income tax rate	13.20%	13.20%	12.10%	15.90%
Atlantic City Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.90%	7.30%	6.90%	7.30%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.30%)	(0.30%)	(0.30%)	(0.30%)
Plant basis differences	(1.90%)	(1.30%)	(2.00%)	(1.30%)
Production tax credits and other credits	0.00%	0.00%	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(23.30%)	(15.40%)	(23.40%)	(14.00%)
Tax Cuts and Jobs Act of 2017		0.00%		0.00%
Other	0.70%	0.30%	0.00%	0.90%
Effective income tax rate	3.10%	11.60%	2.20%	13.60%

Income Taxes - Accounting for U

Income Taxes - Accounting for Uncertainty in Income Taxes (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 448	$ 477
Exelon Generation Co L L C [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	411	408
Commonwealth Edison Co [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	0	2
Pepco Holdings LLC [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	45	45
Atlantic City Electric Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 14	$ 14

Income Taxes Income Taxes - Rea

Income Taxes Income Taxes - Reasonably possible the total amount of unrecognized tax benefits could significantly increase or decrease within 12 months after the reporting date (Details) $ in Millions	Sep. 30, 2019USD ($)
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 425
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	411
Exelon Generation Co L L C [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	411
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	411
Pepco Holdings LLC [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	14
Atlantic City Electric Company [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Decrease in Unrecognized Tax Benefits is Reasonably Possible	$ 14

Income Taxes Income Taxes - Oth

Income Taxes Income Taxes - Other Income Tax Matters (Details) - State and Local Jurisdiction [Member]	3 Months Ended
	Sep. 30, 2019USD ($)
Schedule of Components of Income Tax Expense (Benefit) [Line Items]
Increase (Decrease) in Deferred Income Taxes	$ 23
Increase (Decrease) in Income Taxes	23
Exelon Generation Co L L C [Member]
Schedule of Components of Income Tax Expense (Benefit) [Line Items]
Increase (Decrease) in Deferred Income Taxes	9
Increase (Decrease) in Income Taxes	$ 9

Nuclear Decommissioning - Narra

Nuclear Decommissioning - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)	$ 280		$ (235)
Asset Retirement Obligation, Revision of Estimate	(300)	$ 330		$ 20
Decommissioning Fund Investments	12,706		12,706		$ 11,661
Assets held for sale	18		18		904
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)	280		(235)
Asset Retirement Obligation, Revision of Estimate	(300)	330		0
Decommissioning Fund Investments	12,706		12,706		11,661
Assets held for sale	18		18		904
Potomac Electric Power Company [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Revision of Estimate				$ 22
Nuclear Decommissioning [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Revision of Estimate			211
Nuclear Decommissioning [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Revision of Estimate			211
Three Mile Island [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)		(110)
Three Mile Island [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Period Increase (Decrease)		(110)
Assets, Total [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	12,862		12,862		12,695
Assets, Total [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	12,862		12,862		12,695
Nuclear Decommissioning Trust Fund Investments [Member] | Oyster Creek [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Assets held for sale					890
Nuclear Decommissioning Trust Fund Investments [Member] | Oyster Creek [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Assets held for sale					890
Other Current Assets [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	156		156		144
Other Current Assets [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	156		$ 156		$ 144
Operating Expense [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Revision of Estimate	(65)
Operating Expense [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Revision of Estimate	$ (65)
Operating Expense [Member] | Three Mile Island [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Revision of Estimate		(85)
Operating Expense [Member] | Three Mile Island [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Asset Retirement Obligation, Revision of Estimate		$ (85)

Nuclear Decommissioning - Rollf

Nuclear Decommissioning - Rollforward of Nuclear Decommissioning ARO (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Accretion expense			$ 371	$ 367
Asset Retirement Obligation, Revision of Estimate	$ (300)	$ 330		20
Liabilities held for sale	11		11		$ 777
Nuclear Decommissioning [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Nuclear decommissioning ARO, beginning balance		10,005	10,005
Asset Retirement Obligation, Liabilities Settled			(755)
Accretion expense			361
Asset Retirement Obligation, Revision of Estimate			211
Costs incurred related to decommissioning plants			(52)
Nuclear decommissioning ARO, ending balance	9,770		9,770
Current portion of ARO	127		127		22
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Accretion expense			371	365
Asset Retirement Obligation, Revision of Estimate	(300)	330		$ 0
Liabilities held for sale	11		11		777
Exelon Generation Co L L C [Member] | Nuclear Decommissioning [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Nuclear decommissioning ARO, beginning balance		10,005	10,005
Asset Retirement Obligation, Liabilities Settled			(755)
Accretion expense			361
Asset Retirement Obligation, Revision of Estimate			211
Costs incurred related to decommissioning plants			(52)
Nuclear decommissioning ARO, ending balance	9,770		9,770
Current portion of ARO	127		$ 127		22
Nuclear Decommissioning Asset Retirement Obligation [Member] | Oyster Creek [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Liabilities held for sale					772
Nuclear Decommissioning Asset Retirement Obligation [Member] | Exelon Generation Co L L C [Member] | Oyster Creek [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Liabilities held for sale					$ 772
Operating Expense [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate	(65)
Operating Expense [Member] | Three Mile Island [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate		(85)
Operating Expense [Member] | Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate	$ (65)
Operating Expense [Member] | Exelon Generation Co L L C [Member] | Three Mile Island [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset Retirement Obligation, Revision of Estimate		$ (85)

Retirement Benefits - Narrative

Retirement Benefits - Narrative (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2019USD ($)
Defined Benefit Plan Disclosure [Line Items]
Increase (Decrease) in Obligation, Pension Benefits	$ 75
Increase (Decrease) in Obligation, Other Postretirement Benefits	36
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax	(39)	$ (39)
Defined Benefit Plan Amounts Recognized In Regulatory Assets Before Tax	53
Defined Benefit Plan Amounts Recognized In Regulatory Liabilities Before Tax	$ (5)
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on assets		7.00%
Discount rate		4.31%
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on assets		6.67%
Discount rate		4.30%

Retirement Benefits - Calculati

Retirement Benefits - Calculation of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Amortization of:
Net periodic benefit cost	$ 2	$ 12	$ (8)	$ 33
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	89	100	267	303
Interest cost	221	201	663	602
Expected return on assets	(306)	(312)	(918)	(939)
Amortization of:
Prior service cost (benefit)	0	0	0	1
Actuarial loss	104	158	310	472
Settlement charges	7	0	7	1
Contractual Termination Benefits	1	0	1	0
Net periodic benefit cost	116	147	330	440
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	23	28	70	84
Interest cost	47	43	141	131
Expected return on assets	(38)	(43)	(115)	(130)
Amortization of:
Prior service cost (benefit)	(45)	(47)	(134)	(140)
Actuarial loss	11	18	34	50
Settlement charges	0	0	0	0
Contractual Termination Benefits	0	0	0	0
Net periodic benefit cost	$ (2)	$ (1)	$ (4)	$ (5)

Retirement Benefits - Allocated

Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			$ 324	$ 435
Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	$ 114	$ 145	326	435
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			98	151
Exelon Generation Co L L C [Member] | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	37	50	100	151
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			70	133
Commonwealth Edison Co [Member] | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	23	45	70	133
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			9	14
PECO Energy Co [Member] | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	4	5	9	14
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			45	43
Baltimore Gas and Electric Company [Member] | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	16	15	47	44
Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			71	51
Pepco Holdings LLC [Member] | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	23	17	71	51
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			19	10
Potomac Electric Power Company [Member] | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	6	3	19	10
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			11	5
Delmarva Power and Light Company [Member] | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	4	2	11	5
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			12	10
Atlantic City Electric Company [Member] | Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	$ 4	$ 3	$ 12	$ 10

Retirement Benefits - Defined C

Retirement Benefits - Defined Contribution Savings Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	$ 36	$ 44	$ 101	$ 126
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	14	23	41	65
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	9	8	26	23
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	2	2	7	7
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	4	2	9	5
Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	4	4	8	10
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	1	1	2	2
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	1	1	2	2
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	$ 1	$ 1	$ 1	$ 2

Changes in Accumulated Other _3

Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 33,907	$ 33,704	$ 33,070	$ 32,839	$ 32,565	$ 32,187	$ 33,070	$ 32,187
Beginning Balance			30,764				30,764
Other comprehensive income	30			52			33	169
Ending balance	34,352	33,907	33,704	33,388	32,839	32,565	34,352	33,388
Ending Balance	32,023						32,023
Gains (Losses) on Cash Flow Hedges
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2)		(2)	(2)		(14)	(2)	(14)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0			0			0	11
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0			0			0	1
Other comprehensive income	0			0			0	12
Ending balance	(2)	(2)		(2)	(2)		(2)	(2)
Gains (Losses) on Cash Flow Hedges | Accounting Standards Update 2016-01 [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard(c)								0
Unrealized Gains (Losses) on Marketable Securities
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance						10		10
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax								0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax								0
Other comprehensive income								0
Ending balance				0				0
Unrealized Gains (Losses) on Marketable Securities | Accounting Standards Update 2016-01 [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard(c)								(10)
Pension and Non-Pension Postretirement Benefit Plan Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2,957)		(2,960)	(2,890)		(2,998)	(2,960)	(2,998)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	6			5			(32)	22
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	21			45			62	136
Other comprehensive income	27			50			30	158
Ending balance	(2,930)	(2,957)		(2,840)	(2,890)		(2,930)	(2,840)
Pension and Non-Pension Postretirement Benefit Plan Items | Accounting Standards Update 2016-01 [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard(c)								0
Foreign Currency Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(29)		(33)	(29)		(23)	(33)	(23)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(2)			2			2	(4)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	0			0			0	0
Other comprehensive income	(2)			2			2	(4)
Ending balance	(31)	(29)		(27)	(29)		(31)	(27)
Foreign Currency Items | Accounting Standards Update 2016-01 [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard(c)								0
AOCI of Investments in Unconsolidated Affiliates
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2)		0	0		(1)	0	(1)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0			0			(2)	1
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	2			0			2	0
Other comprehensive income	2			0			0	1
Ending balance	0	(2)		0	0		0	0
AOCI of Investments in Unconsolidated Affiliates | Accounting Standards Update 2016-01 [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard(c)								0
Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2,990)	(3,012)	(2,995)	(2,921)	(2,965)	(3,026)	(2,995)	(3,026)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	4			7			(32)	30
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	23			45			64	137
Other comprehensive income	27	22	(17)	52	44	71	32	167
Ending balance	$ (2,963)	$ (2,990)	$ (3,012)	$ (2,869)	$ (2,921)	$ (2,965)	$ (2,963)	(2,869)
Total | Accounting Standards Update 2016-01 [Member]
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Impact of adoption of Recognition and Measurement of Financial Assets and Liabilities standard(c)								$ (10)

Changes in Accumulated Other _4

Changes in Accumulated Other Comprehensive Income - Components of Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Prior service costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ 6	$ 6	$ 18	$ 18
Actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(13)	(21)	(39)	(65)
Pension and Non-Pension Postretirement Benefit Plan Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ 0	$ (2)	$ 14	$ (8)

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	Mar. 23, 2016USD ($)MW	Sep. 30, 2019USD ($)MGPSiteOpen_claimMW	Dec. 31, 2022MW	Dec. 31, 2018USD ($)MW	Dec. 31, 2017MW
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 3,113
Accrual for Environmental Loss Contingencies, Gross		507		$ 496
Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		2,476
Accrual for Environmental Loss Contingencies, Gross		107		108
Liability for Asbestos and Environmental Claims, Gross		83		79
Commonwealth Edison Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 257
Mgp Site Contingency Monitoring Count | MGPSite		21
Accrual for Environmental Loss Contingencies, Gross		$ 328		329
PECO Energy Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 187
Mgp Site Contingency Monitoring Count | MGPSite		8
Accrual for Environmental Loss Contingencies, Gross		$ 20		27
Baltimore Gas and Electric Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 25
Mgp Site Contingency Monitoring Count | MGPSite		4
Accrual for Environmental Loss Contingencies, Gross		$ 3		5
Pepco Holdings LLC [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		61
Accrual for Environmental Loss Contingencies, Gross		49		27
Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		36
Accrual for Environmental Loss Contingencies, Gross		47		25
Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 16
Mgp Site Contingency Count | MGPSite		1
Accrual for Environmental Loss Contingencies, Gross		$ 1		$ 1
Open Claims [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Liability for Asbestos and Environmental Claims, Gross		$ 25
Open Asbestos Related Personal Injury Claims | Open_claim		257
Estimated Future Claims [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Liability for Asbestos and Environmental Claims, Gross		$ 58
Pepco Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		513
Pepco Holdings Inc [Member] | Pepco Holdings LLC [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		320
Pepco Holdings Inc [Member] | Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		120
Pepco Holdings Inc [Member] | Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		89
West Lake [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		280
West Lake [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross		20
Accrual for Environmental Loss Contingencies, Component Amount		90
Other Solar Projects [Member] | Pepco Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Business Acquisition, Expected New Generation Mwh | MW	37
Other Commitment	$ 127	$ 107
Other Non-Financial Commitment | MW		27
Other Solar Projects [Member] | Pepco Holdings Inc [Member] | Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 107
Wind Assets [Member] | Pepco Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Non-Financial Commitment | MW	100
Wind Assets [Member] | Pepco Holdings Inc [Member] | Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Purchase Commitment | MW	120			40	40
Subsequent Event [Member] | Wind Assets [Member] | Pepco Holdings Inc [Member] | Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Purchase Commitment | MW			40

Commitments and Contingencies_3

Commitments and Contingencies - Merger Commitment (Details) $ in Millions	Sep. 30, 2019USD ($)
Other Commitments [Line Items]
Other Commitment	$ 3,113
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	61
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	36
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	16
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	10
Pepco Holdings Inc [Member]
Other Commitments [Line Items]
Other Commitment	513
Pepco Holdings Inc [Member] | Remaining commitment
Other Commitments [Line Items]
Other Commitment	112
Pepco Holdings Inc [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	320
Pepco Holdings Inc [Member] | Pepco Holdings LLC [Member] | Remaining commitment
Other Commitments [Line Items]
Other Commitment	82
Pepco Holdings Inc [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	120
Pepco Holdings Inc [Member] | Potomac Electric Power Company [Member] | Remaining commitment
Other Commitments [Line Items]
Other Commitment	67
Pepco Holdings Inc [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	89
Pepco Holdings Inc [Member] | Delmarva Power and Light Company [Member] | Remaining commitment
Other Commitments [Line Items]
Other Commitment	9
Pepco Holdings Inc [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	111
Pepco Holdings Inc [Member] | Atlantic City Electric Company [Member] | Remaining commitment
Other Commitments [Line Items]
Other Commitment	$ 6

Commitments and Contingencies_4

Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Sep. 30, 2019USD ($)
Other Commitments [Line Items]
Other Commitment	$ 3,113
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1,507
Other Commitment, Due in Second Year	1,155
Other Commitment, Due in Third Year	52
Other Commitment, Due in Fourth Year	4
Other Commitment, Due in Fifth Year	3
Other Commitment, Due after Fifth Year	393
Guarantor Obligations, Maximum Exposure, Undiscounted	68
Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,718
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1,192
Other Commitment, Due in Second Year	515
Other Commitment, Due in Third Year	11
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Surety Bonds
Other Commitments [Line Items]
Other Commitment	991
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	315
Other Commitment, Due in Second Year	638
Other Commitment, Due in Third Year	38
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	378
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	378
Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	26
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	2
Other Commitment, Due in Third Year	3
Other Commitment, Due in Fourth Year	4
Other Commitment, Due in Fifth Year	3
Other Commitment, Due after Fifth Year	15
Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Other Commitment	2,476
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1,477
Other Commitment, Due in Second Year	988
Other Commitment, Due in Third Year	11
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Exelon Generation Co L L C [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,686
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1,179
Other Commitment, Due in Second Year	496
Other Commitment, Due in Third Year	11
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Exelon Generation Co L L C [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	790
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	298
Other Commitment, Due in Second Year	492
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Other Commitment	257
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	9
Other Commitment, Due in Second Year	46
Other Commitment, Due in Third Year	2
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	200
Commonwealth Edison Co [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	7
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	4
Other Commitment, Due in Second Year	3
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Commonwealth Edison Co [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	50
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	5
Other Commitment, Due in Second Year	43
Other Commitment, Due in Third Year	2
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Commonwealth Edison Co [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	200
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	200
PECO Energy Co [Member]
Other Commitments [Line Items]
Other Commitment	187
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1
Other Commitment, Due in Second Year	8
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	178
PECO Energy Co [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	9
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1
Other Commitment, Due in Second Year	8
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
PECO Energy Co [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	178
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	178
Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	25
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	4
Other Commitment, Due in Second Year	21
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Baltimore Gas and Electric Company [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	8
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	2
Other Commitment, Due in Second Year	6
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Baltimore Gas and Electric Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	17
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	2
Other Commitment, Due in Second Year	15
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	61
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	6
Other Commitment, Due in Second Year	31
Other Commitment, Due in Third Year	3
Other Commitment, Due in Fourth Year	4
Other Commitment, Due in Fifth Year	3
Other Commitment, Due after Fifth Year	15
Guarantor Obligations, Maximum Exposure, Undiscounted	68
Pepco Holdings LLC [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	11
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1
Other Commitment, Due in Second Year	10
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Pepco Holdings LLC [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	24
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	5
Other Commitment, Due in Second Year	19
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Pepco Holdings LLC [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	26
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	2
Other Commitment, Due in Third Year	3
Other Commitment, Due in Fourth Year	4
Other Commitment, Due in Fifth Year	3
Other Commitment, Due after Fifth Year	15
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	36
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	2
Other Commitment, Due in Second Year	25
Other Commitment, Due in Third Year	1
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	1
Other Commitment, Due after Fifth Year	6
Guarantor Obligations, Maximum Exposure, Undiscounted	22
Potomac Electric Power Company [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	10
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	10
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Potomac Electric Power Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	17
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	2
Other Commitment, Due in Second Year	15
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Potomac Electric Power Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	9
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	1
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	1
Other Commitment, Due after Fifth Year	6
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	16
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	3
Other Commitment, Due in Second Year	3
Other Commitment, Due in Third Year	1
Other Commitment, Due in Fourth Year	2
Other Commitment, Due in Fifth Year	1
Other Commitment, Due after Fifth Year	6
Guarantor Obligations, Maximum Exposure, Undiscounted	29
Delmarva Power and Light Company [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	1
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1
Other Commitment, Due in Second Year	0
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Delmarva Power and Light Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	4
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	2
Other Commitment, Due in Second Year	2
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Delmarva Power and Light Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	11
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	1
Other Commitment, Due in Third Year	1
Other Commitment, Due in Fourth Year	2
Other Commitment, Due in Fifth Year	1
Other Commitment, Due after Fifth Year	6
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	10
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1
Other Commitment, Due in Second Year	3
Other Commitment, Due in Third Year	1
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	1
Other Commitment, Due after Fifth Year	3
Guarantor Obligations, Maximum Exposure, Undiscounted	17
Atlantic City Electric Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	3
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1
Other Commitment, Due in Second Year	2
Other Commitment, Due in Third Year	0
Other Commitment, Due in Fourth Year	0
Other Commitment, Due in Fifth Year	0
Other Commitment, Due after Fifth Year	0
Atlantic City Electric Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	7
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	0
Other Commitment, Due in Second Year	1
Other Commitment, Due in Third Year	1
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	1
Other Commitment, Due after Fifth Year	$ 3
Maximum [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	84 years
Maximum [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	8 years
Maximum [Member] | Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	33 years
Maximum [Member] | Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	18 years
Maximum [Member] | PECO Energy Co [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	84 years
Maximum [Member] | Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	24 years
Maximum [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	14 years
Maximum [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	7 years
Maximum [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	14 years
Maximum [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	3 years
Minimum [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | PECO Energy Co [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	24 years
Minimum [Member] | Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year
Minimum [Member] | Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	2 years
Minimum [Member] | Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	13 years
Minimum [Member] | Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	1 year

Commitments and Contingencies_5

Commitments and Contingencies - Schedule of Accruals for Environmental Matters (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	$ 507	$ 496
Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	107	108
Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	328	329
PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	20	27
Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	3	5
Pepco Holdings LLC [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	49	27
Potomac Electric Power Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	47	25
Delmarva Power and Light Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	1	1
Atlantic City Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	1	1
Accrual For MGP Investigation And Remediation [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	346	356
Accrual For MGP Investigation And Remediation [Member] | Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	0	0
Accrual For MGP Investigation And Remediation [Member] | Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	327	327
Accrual For MGP Investigation And Remediation [Member] | PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	18	25
Accrual For MGP Investigation And Remediation [Member] | Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	1	4
Accrual For MGP Investigation And Remediation [Member] | Pepco Holdings LLC [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	0	0
Accrual For MGP Investigation And Remediation [Member] | Potomac Electric Power Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	0	0
Accrual For MGP Investigation And Remediation [Member] | Delmarva Power and Light Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	0	0
Accrual For MGP Investigation And Remediation [Member] | Atlantic City Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	$ 0	$ 0

Supplemental Financial Inform_3

Supplemental Financial Information - Utility Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Supplemental Statement of Operations Information [Line Items]
Utility taxes	$ 241	$ 253	$ 672	$ 705
Property	148	145	444	416
Payroll	57	58	185	191
Exelon Generation Co L L C [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	29	32	87	92
Property	66	70	205	204
Payroll	28	31	92	99
Commonwealth Edison Co [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	66	67	183	188
Property	7	7	22	22
Payroll	7	6	21	20
PECO Energy Co [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	38	39	102	102
Property	5	4	12	12
Payroll	3	3	11	11
Baltimore Gas and Electric Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	21	23	68	70
Property	39	37	114	106
Payroll	4	4	13	12
Pepco Holdings LLC [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	86	92	231	253
Property	31	26	91	71
Payroll	6	5	20	19
Potomac Electric Power Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	81	87	217	238
Property	21	16	64	45
Payroll	2	1	5	5
Delmarva Power and Light Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	5	5	14	15
Property	9	9	25	24
Payroll	1	1	3	3
Atlantic City Electric Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	0	0	0	0
Property	0	0	2	2
Payroll	$ 1	$ 1	$ 2	$ 2

Supplemental Financial Inform_4

Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	$ 67	$ 214	$ 197	$ 476
Net realized income on NDT funds - Non-regulatory agreement units	33	58	316	257
Net unrealized (losses) gains on NDT funds - Regulatory agreement units	89	(66)	565	(335)
Net unrealized (losses) gains on NDT funds - Non-regulatory agreement units	55	72	236	(143)
Regulatory offset to NDT fund-related activities	(125)	(110)	(611)	(110)
Decommissioning-related activities	119	168	703	145
AFUDC - Equity	22	16	64	47
Non-service net periodic benefit cost	(2)	(12)	8	(33)
Exelon Generation Co L L C [Member]
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	67	214	197	476
Net realized income on NDT funds - Non-regulatory agreement units	33	58	316	257
Net unrealized (losses) gains on NDT funds - Regulatory agreement units	89	(66)	565	(335)
Net unrealized (losses) gains on NDT funds - Non-regulatory agreement units	55	72	236	(143)
Regulatory offset to NDT fund-related activities	(125)	(110)	(611)	(110)
Decommissioning-related activities	119	168	703	145
AFUDC - Equity	0	0	0	0
Commonwealth Edison Co [Member]
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	4	4	13	12
PECO Energy Co [Member]
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	3	1	9	3
Baltimore Gas and Electric Company [Member]
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	6	5	16	13
Pepco Holdings LLC [Member]
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	9	6	26	19
Potomac Electric Power Company [Member]
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	7	6	18	17
Delmarva Power and Light Company [Member]
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	1	0	3	2
Atlantic City Electric Company [Member]
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	$ 1	$ 0	$ 4	$ 0

Supplemental Financial Inform_5

Supplemental Financial Information - Cash Flow (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2019	Sep. 30, 2018
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			$ 2,803	$ 2,829
Amortization of regulatory assets			390	412
Amortization of intangible assets, net			44	43
Amortization of energy contract assets and liabilities			14	8
Nuclear fuel			771	852
ARO accretion			371	367
Total depreciation, amortization and accretion			4,393	4,511
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			324	435
Provision for uncollectible accounts			89	133
Other decommissioning-related activity			(400)	(39)
Energy-related options			21	4
Amortization of rate stabilization deferral			(8)	0
Discrete impacts from EIMA and FEJA			80	27
Long-term incentive plan			33	84
Amortization of operating ROU asset			193
Change in environmental liabilities			23
Asset retirement costs	$ (300)	$ 330		20
Exelon Generation Co L L C [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			1,184	1,347
Amortization of regulatory assets			0	0
Amortization of intangible assets, net			37	36
Amortization of energy contract assets and liabilities			14	8
Nuclear fuel			771	852
ARO accretion			371	365
Total depreciation, amortization and accretion			2,377	2,608
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			98	151
Provision for uncollectible accounts			20	38
Other decommissioning-related activity			(400)	(39)
Energy-related options			21	4
Amortization of rate stabilization deferral			0	0
Amortization of operating ROU asset			138
Change in environmental liabilities			0
Asset retirement costs	$ (300)	$ 330		0
Commonwealth Edison Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			661	613
Amortization of regulatory assets			106	83
Amortization of intangible assets, net			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			767	696
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			70	133
Provision for uncollectible accounts			26	30
Amortization of rate stabilization deferral			0	0
Discrete impacts from EIMA and FEJA			80	27
Amortization of operating ROU asset			2
Change in environmental liabilities			0
Asset retirement costs				0
PECO Energy Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			225	204
Amortization of regulatory assets			22	20
Amortization of intangible assets, net			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			247	224
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			9	14
Provision for uncollectible accounts			22	25
Amortization of rate stabilization deferral			0	0
Amortization of operating ROU asset			0
Change in environmental liabilities			0
Asset retirement costs				0
Baltimore Gas and Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			263	249
Amortization of regulatory assets			105	109
Amortization of intangible assets, net			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			368	358
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			45	43
Provision for uncollectible accounts			5	6
Amortization of rate stabilization deferral			0	0
Amortization of operating ROU asset			23
Change in environmental liabilities			0
Asset retirement costs				0
Pepco Holdings LLC [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			405	355
Amortization of regulatory assets			157	200
Amortization of intangible assets, net			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			562	555
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			71	51
Provision for uncollectible accounts			16	32
Amortization of rate stabilization deferral			(8)	0
Amortization of operating ROU asset			26
Change in environmental liabilities			23
Asset retirement costs				20
Potomac Electric Power Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			178	161
Amortization of regulatory assets			103	125
Amortization of intangible assets, net			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			281	286
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			19	10
Provision for uncollectible accounts			7	12
Amortization of rate stabilization deferral			(9)	0
Amortization of operating ROU asset			6
Change in environmental liabilities			23
Asset retirement costs				22
Delmarva Power and Light Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			109	97
Amortization of regulatory assets			29	38
Amortization of intangible assets, net			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			138	135
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			11	5
Provision for uncollectible accounts			2	6
Amortization of rate stabilization deferral			1	0
Amortization of operating ROU asset			7
Change in environmental liabilities			0
Asset retirement costs				(1)
Atlantic City Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment			89	70
Amortization of regulatory assets			25	37
Amortization of intangible assets, net			0	0
ARO accretion			0	0
Total depreciation, amortization and accretion			114	107
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs			12	10
Provision for uncollectible accounts			6	14
Amortization of rate stabilization deferral			0	0
Amortization of operating ROU asset			4
Change in environmental liabilities			$ 0
Asset retirement costs				$ (1)

Supplemental Financial Inform_6

Supplemental Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 1,683	$ 1,349	$ 1,918	$ 898
Restricted cash	309	247	240	207
Restricted cash included in other long-term assets	186	185	163	85
Total cash, cash equivalents and restricted cash	2,178	1,781	2,321	1,190
Receivables [Abstract]
Unbilled customer revenues	1,256	1,656
Accrued Expenses [Abstract]
Compensation-related accruals	880	1,191
Taxes accrued	431	412
Interest accrued	421	334
Exelon Generation Co L L C [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	1,019	750	1,187	416
Restricted cash	126	153	152	138
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	1,145	903	1,339	554
Receivables [Abstract]
Unbilled customer revenues	676	965
Accrued Expenses [Abstract]
Compensation-related accruals	336	479
Taxes accrued	247	226
Interest accrued	106	77
Commonwealth Edison Co [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	76	135	124	76
Restricted cash	124	29	12	5
Restricted cash included in other long-term assets	171	166	144	63
Total cash, cash equivalents and restricted cash	371	330	280	144
Receivables [Abstract]
Unbilled customer revenues	212	223
Accrued Expenses [Abstract]
Compensation-related accruals	133	187
Taxes accrued	56	71
Interest accrued	62	105
PECO Energy Co [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	224	130	102	271
Restricted cash	6	5	5	4
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	230	135	107	275
Receivables [Abstract]
Unbilled customer revenues	102	114
Accrued Expenses [Abstract]
Compensation-related accruals	48	49
Taxes accrued	13	28
Interest accrued	33	33
Baltimore Gas and Electric Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	130	7	113	17
Restricted cash	1	6	3	1
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	131	13	116	18
Receivables [Abstract]
Unbilled customer revenues	103	168
Accrued Expenses [Abstract]
Compensation-related accruals	63	68
Taxes accrued	64	46
Interest accrued	36	39
Pepco Holdings LLC [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	99	124	153	30
Restricted cash	38	43	42	42
Restricted cash included in other long-term assets	15	19	19	23
Total cash, cash equivalents and restricted cash	152	186	214	95
Receivables [Abstract]
Unbilled customer revenues	163	186
Accrued Expenses [Abstract]
Compensation-related accruals	86	99
Taxes accrued	80	74
Interest accrued	78	50
Potomac Electric Power Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	18	16	12	5
Restricted cash	34	37	35	35
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	52	53	47	40
Receivables [Abstract]
Unbilled customer revenues	91	97
Accrued Expenses [Abstract]
Compensation-related accruals	26	29
Taxes accrued	61	58
Interest accrued	37	25
Delmarva Power and Light Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	11	23	110	2
Restricted cash	0	1	0	0
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	11	24	110	2
Receivables [Abstract]
Unbilled customer revenues	38	59
Accrued Expenses [Abstract]
Compensation-related accruals	17	19
Taxes accrued	17	4
Interest accrued	20	8
Atlantic City Electric Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	13	7	11	2
Restricted cash	3	4	7	6
Restricted cash included in other long-term assets	15	19	19	23
Total cash, cash equivalents and restricted cash	31	30	$ 37	$ 31
Receivables [Abstract]
Unbilled customer revenues	34	30
Accrued Expenses [Abstract]
Compensation-related accruals	13	12
Taxes accrued	3	5
Interest accrued	$ 19	$ 12

Segment Information - Narrative

Segment Information - Narrative (Details)	9 Months Ended
	Sep. 30, 2019Reportable_segment
Segment Reporting Information [Line Items]
Number of reportable segments	11
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	5
Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Number of reportable segments	3

Segment Information - Reconcili

Segment Information - Reconciliation to Consolidated Financial Statements (Details) - USD ($) $ in Millions		3 Months Ended						9 Months Ended
		Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues		$ 8,929			$ 9,403			$ 26,096	$ 27,170
Operating revenues from affiliates		0			0			0	0
Depreciation, Depletion and Amortization		1,083			1,105			3,237	3,284
Operating Expenses		7,559			8,252			22,703	24,036
Interest Revenue (Expense), Net		409			393			1,221	1,138
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		1,102			947			3,028	2,263
Income taxes		172			137			626	262
Net income (loss)		760	$ 494	$ 966	800	$ 542	$ 636	2,220	1,979
Payments to Acquire Property, Plant, and Equipment		1,687			1,690			5,259	5,497
Assets	[1]	122,738						122,738		$ 119,666
Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		1,380			1,361			3,700	3,688
Operating revenues from affiliates		4			3			11	11
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		203			191			436	363
Income taxes		14			4			25	28
Net income (loss)		189	106	117	187	84	65	412	336
Payments to Acquire Property, Plant, and Equipment								1,006	988
Assets	[2]	22,576						22,576		21,984
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenues		4,774			5,278			14,280	15,368
Operating revenues from affiliates		275			308			844	979
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		501			389			1,355	800
Income taxes		87			78			388	110
Net income (loss)		244	$ 118	$ 422	300	$ 181	$ 186	784	667
Payments to Acquire Property, Plant, and Equipment								1,282	1,660
Assets	[3]	47,984						47,984		47,556
Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		194			139			432	335
Revenues		8,929			9,403			26,096	27,170
Net income (loss)		760			800			2,220	1,979
Assets		122,738						122,738		119,666
Operating Segments [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(9)			(5)			4	7
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		(1)			(1)			(4)	(4)
Revenues		(763)			(780)			(2,296)	(2,436)
Operating revenues from affiliates		(764)			(779)			(2,300)	(2,430)
Depreciation, Depletion and Amortization		0			0			0	0
Operating Expenses		(759)			(790)			(2,291)	(2,467)
Interest Revenue (Expense), Net		0			0			0	0
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		0			0			0	0
Income taxes		0			0			0	0
Net income (loss)		0			0			0	0
Payments to Acquire Property, Plant, and Equipment		0			0			0	0
Assets		(10,085)						(10,085)		(9,800)
Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		(92)			(104)			(298)	(328)
Operating revenues from affiliates		(93)			(105)			(298)	(327)
Depreciation, Depletion and Amortization		0			0			0	0
Operating Expenses		(94)			(104)			(298)	(324)
Interest Revenue (Expense), Net		0			0			0	0
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		(195)			(182)			(422)	(339)
Income taxes		(1)			1			(1)	0
Net income (loss)		4			3			11	11
Payments to Acquire Property, Plant, and Equipment		0			0			0	0
Assets		(5,738)						(5,738)		(5,421)
Exelon Generation Co L L C [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		195			140			436	339
Revenues		4,774			5,278			14,280	15,368
Depreciation, Depletion and Amortization		407			468			1,221	1,383
Operating Expenses		4,274			4,961			13,333	14,475
Interest Revenue (Expense), Net		109			101			336	305
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		501			389			1,355	800
Income taxes		87			78			388	110
Net income (loss)		244			300			784	667
Payments to Acquire Property, Plant, and Equipment		392			362			1,282	1,660
Assets		47,984						47,984		47,556
Exelon Generation Co L L C [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		275			308			844	981
Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Revenues		1,583			1,598			4,342	4,508
Depreciation, Depletion and Amortization		259			237			767	696
Operating Expenses		1,256			1,275			3,431	3,610
Interest Revenue (Expense), Net		91			85			268	261
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		245			245			674	663
Income taxes		45			52			130	140
Net income (loss)		200			193			544	523
Payments to Acquire Property, Plant, and Equipment		452			514			1,413	1,540
Assets		32,326						32,326		31,213
Commonwealth Edison Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		4			4			13	23
PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Revenues		778			757			2,333	2,275
Depreciation, Depletion and Amortization		83			75			247	224
Operating Expenses		595			603			1,783	1,853
Interest Revenue (Expense), Net		33			32			100	96
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		154			124			461	331
Income taxes		14			(2)			51	(5)
Net income (loss)		140			126			410	336
Payments to Acquire Property, Plant, and Equipment		228			204			675	615
Assets		11,379						11,379		10,642
PECO Energy Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		1			2			4	5
Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Revenues		703			731			2,327	2,369
Depreciation, Depletion and Amortization		116			110			368	358
Operating Expenses		612			628			1,936	2,005
Interest Revenue (Expense), Net		31			27			89	78
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		67			81			320	301
Income taxes		12			18			59	59
Net income (loss)		55			63			261	242
Payments to Acquire Property, Plant, and Equipment		300			233			842	667
Assets		10,304						10,304		9,716
Baltimore Gas and Electric Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		6			6			18	18
Pepco Holdings LLC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Revenues		1,380			1,361			3,700	3,688
Depreciation, Depletion and Amortization		193			192			562	555
Operating Expenses		1,124			1,116			3,106	3,165
Interest Revenue (Expense), Net		66			65			197	193
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		203			191			436	363
Income taxes		14			4			25	28
Net income (loss)		189			187			412	336
Payments to Acquire Property, Plant, and Equipment		308			359			1,006	988
Assets		22,576						22,576		21,984
Pepco Holdings LLC [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		4			3			11	11
Potomac Electric Power Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		642			628			1,748	1,708
Depreciation, Depletion and Amortization		95			99			281	286
Operating Expenses		515			516			1,444	1,454
Interest Revenue (Expense), Net		33			32			100	96
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		103			87			226	181
Income taxes		5			(2)			9	7
Net income (loss)		98			89			217	174
Payments to Acquire Property, Plant, and Equipment		157			188			455	475
Assets		8,603						8,603		8,299
Potomac Electric Power Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		2			2			5	5
Delmarva Power and Light Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		319			328			987	1,001
Depreciation, Depletion and Amortization		46			47			138	135
Operating Expenses		268			277			820	859
Interest Revenue (Expense), Net		15			15			45	42
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		38			38			132	107
Income taxes		5			5			16	17
Net income (loss)		33			33			116	90
Payments to Acquire Property, Plant, and Equipment		85			88			245	254
Assets		4,724						4,724		4,588
Delmarva Power and Light Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		1			2			5	6
Atlantic City Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		419			406			966	981
Depreciation, Depletion and Amortization		43			38			114	107
Operating Expenses		340			322			838	847
Interest Revenue (Expense), Net		15			16			44	48
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		65			69			89	88
Income taxes		2			8			2	12
Net income (loss)		63			61			87	76
Payments to Acquire Property, Plant, and Equipment		73			77			300	247
Assets		3,916						3,916		3,699
Atlantic City Electric Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		1			1			2	2
Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Revenues		474			458			1,410	1,398
Depreciation, Depletion and Amortization		25			23			72	68
Operating Expenses		457			459			1,405	1,395
Interest Revenue (Expense), Net		79			83			231	205
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		(68)			(83)			(218)	(195)
Income taxes		0			(13)			(27)	(70)
Net income (loss)		(68)			(69)			(191)	(125)
Payments to Acquire Property, Plant, and Equipment		7			18			41	27
Assets		8,254						8,254		8,355
Corporate and Other [Member] | Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		92			103			297	326
Depreciation, Depletion and Amortization		9			8			29	27
Operating Expenses		95			105			302	329
Interest Revenue (Expense), Net		3			2			8	7
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest		192			179			411	326
Income taxes		3			(8)			(1)	(8)
Net income (loss)		(9)			1			(19)	(15)
Payments to Acquire Property, Plant, and Equipment		(7)			6			6	12
Assets		11,071						11,071		$ 10,819
Corporate and Other [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		474			456			1,410	1,392
Corporate and Other [Member] | Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		93			103			297	325
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues		1,364			1,456			3,809	4,179
Generation Mid Atlantic [Member] | PECO Energy Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		43			35			123	97
Generation Mid Atlantic [Member] | Baltimore Gas And Electric Company Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		65			69			199	198
Generation Mid Atlantic [Member] | PotomacElectricPowerCompanyAffiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		65			46			188	143
Generation Mid Atlantic [Member] | DelmarvaPowerandLightCompanyAffiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		14			26			50	103
Generation Mid Atlantic [Member] | AtlanticCityElectricCompanyAffiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		3			10			16	21
Generation Mid Atlantic [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		1,361			1,449			3,807	4,162
Generation Mid Atlantic [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		3			7			2	17
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues		1,082			1,117			3,224	3,593
Generation Midwest [Member] | Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		83			122			266	419
Generation Midwest [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		1,099			1,121			3,255	3,601
Generation Midwest [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		(17)			(4)			(31)	(8)
Oil and Gas, Purchased [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		266			397			1,479	1,831
Oil and Gas, Purchased [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1			0			0	(8)
Oil and Gas, Purchased [Member] | Exelon Generation Co L L C [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		265			397			1,479	1,839
Oil and Gas, Purchased [Member] | Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Oil and Gas, Purchased [Member] | PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Oil and Gas, Purchased [Member] | Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Oil and Gas, Purchased [Member] | Pepco Holdings LLC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Oil and Gas, Purchased [Member] | Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, US Regulated | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,365			1,340			3,570	3,541
Electricity, US Regulated | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		4,268			4,270			11,609	11,766
Electricity, US Regulated | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(7)			(7)			(25)	(34)
Electricity, US Regulated | Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(3)			(4)			(10)	(12)
Electricity, US Regulated | Exelon Generation Co L L C [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, US Regulated | Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,583			1,598			4,342	4,508
Electricity, US Regulated | PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		716			700			1,901	1,893
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		619			645			1,817	1,850
Electricity, US Regulated | Pepco Holdings LLC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,357			1,334			3,574	3,549
Electricity, US Regulated | Potomac Electric Power Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		642			628			1,748	1,708
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		299			304			871	872
Electricity, US Regulated | Atlantic City Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		419			406			966	981
Electricity, US Regulated | Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, US Regulated | Corporate and Other [Member] | Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			(1)	0
Electricity, Generation [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		4,039			4,435			11,525	12,221
Electricity, Generation [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(275)			(306)			(840)	(969)
Electricity, Generation [Member] | Exelon Generation Co L L C [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		4,314			4,741			12,365	13,190
Electricity, Generation [Member] | Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, Generation [Member] | PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, Generation [Member] | Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, Generation [Member] | Pepco Holdings LLC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, Generation [Member] | Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		20			23			115	129
Natural Gas, US Regulated | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		163			162			1,046	1,017
Natural Gas, US Regulated | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(3)			(5)			(12)	(13)
Natural Gas, US Regulated | Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | Exelon Generation Co L L C [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		62			57			432	382
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		84			86			510	519
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		20			24			116	129
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		20			24			116	129
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | Corporate and Other [Member] | Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(1)			0			5	0
Service, Other [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(478)			(461)			(1,415)	(1,408)
Service, Other [Member] | Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(89)			(100)			(288)	(316)
Service, Other [Member] | Exelon Generation Co L L C [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Pepco Holdings LLC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		3			3			10	10
Service, Other [Member] | Potomac Electric Power Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Delmarva Power and Light Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Atlantic City Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		474			458			1,410	1,398
Service, Other [Member] | Corporate and Other [Member] | Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		$ 92			$ 103			$ 298	$ 326
[1]	Exelon’s consolidated assets include $9,465 million and $9,667 million at September 30, 2019 and December 31, 2018 , respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,517 million and $3,548 million at September 30, 2019 and December 31, 2018 , respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 2 — Variable Interest Entities for additional information.
[2]	PHI’s consolidated total assets include $22 million and $33 million at September 30, 2019 and December 31, 2018 , respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $50 million and $69 million at September 30, 2019 and December 31, 2018 , respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 2 — Variable Interest Entities for additional information.
[3]	Generation’s consolidated assets include $9,443 million and $9,634 million at September 30, 2019 and December 31, 2018 , respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,467 million and $3,480 million at September 30, 2019 and December 31, 2018 , respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 2 — Variable Interest Entities for additional information.

Segment Information - Generatio

Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Revenues	$ 8,929	$ 9,403	$ 26,096	$ 27,170
Operating revenues from affiliates	0	0	0	0
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,364	1,456	3,809	4,179
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	1,082	1,117	3,224	3,593
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	429	469	1,211	1,269
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	365	444	805	930
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	1,040	1,212	3,254	3,114
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	4,280	4,698	12,303	13,085
Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	299	440	1,541	1,944
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	195	140	436	339
Unrealized Gain (Loss) on Securities	77	6	64	96
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,774	5,278	14,280	15,368
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	8,929	9,403	26,096	27,170
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,361	1,449	3,807	4,162
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	1,099	1,121	3,255	3,601
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	429	469	1,211	1,268
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	360	445	792	929
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	1,065	1,257	3,300	3,230
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	4,314	4,741	12,365	13,190
Operating Segments [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	265	397	1,479	1,839
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Unrealized Gain (Loss) on Securities	17	71	84	104
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,774	5,278	14,280	15,368
Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	195	140	436	339
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(763)	(780)	(2,296)	(2,436)
Operating revenues from affiliates	(764)	(779)	(2,300)	(2,430)
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	3	7	2	17
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(17)	(4)	(31)	(8)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	0	0	0	1
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	5	(1)	13	1
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(25)	(45)	(46)	(116)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(34)	(43)	(62)	(105)
Intersegment Eliminations [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	34	43	62	105
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	0	0	0	0
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	0	0	0	0
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,351	1,397	3,798	3,971
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	1,052	1,095	3,083	3,432
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	414	475	1,195	1,305
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	288	156	594	470
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	873	959	2,849	2,656
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	3,978	4,082	11,519	11,834
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	160	200	1,041	1,016
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,250	4,412	12,903	13,235
Revenue from Contract with Customer [Member] | Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	112	130	343	385
Other [Member] | Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	10	52	9	191
Other [Member] | Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	47	26	172	169
Other [Member] | Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	15	(6)	16	(37)
Other [Member] | Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	72	289	198	459
Other [Member] | Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	192	298	451	574
Other [Member] | Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	336	659	846	1,356
Other [Member] | Operating Segments [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	105	197	438	823
Other [Member] | Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	524	866	1,377	2,133
Other [Member] | Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	$ 83	$ 10	$ 93	$ (46)

Segment Information - Generat_2

Segment Information - Generation Total Revenues Net of Purchased Power and Fuel Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	$ 689	$ 763	$ 2,023	$ 2,348
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	747	768	2,247	2,400
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	291	292	810	841
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	72	98	225	216
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	184	180	478	607
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	1,983	2,101	5,783	6,412
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	140	197	349	404
Unrealized Gain (Loss) on Securities	77	6	64	96
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	2,123	2,298	6,132	6,816
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	684	746	2,007	2,303
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	763	763	2,269	2,381
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	288	290	800	832
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	76	161	252	396
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	212	226	542	740
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	2,023	2,186	5,870	6,652
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	100	112	262	164
Unrealized Gain (Loss) on Securities	17	71	84	104
Nuclear Fuel Amortization	3	18	13	53
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue Net Of Purchase Power And Fuel From External Customers	2,123	2,298	6,132	6,816
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	5	17	16	45
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(16)	5	(22)	19
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	3	2	10	9
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(4)	(63)	(27)	(180)
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(28)	(46)	(64)	(133)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(40)	(85)	(87)	(240)
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	40	85	87	240
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	$ 0	$ 0	$ 0	$ 0

Segment Information - Electric

Segment Information - Electric and Gas Revenue by Customer Class (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue, Major Customer [Line Items]
Revenue from Related Parties	$ 0	$ 0	$ 0	$ 0
Revenues	8,929	9,403	26,096	27,170
Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenues	8,929	9,403	26,096	27,170
Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	4	4	13	23
Revenues	1,583	1,598	4,342	4,508
Commonwealth Edison Co [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(56)	(15)	(98)	(27)
Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,633	1,606	4,418	4,512
Commonwealth Edison Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(50)	(8)	(76)	(4)
PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	1	2	4	5
Revenues	778	757	2,333	2,275
PECO Energy Co [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(11)	1	(16)	2
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	1	2	4	5
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	0	0	0	0
PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	785	753	2,338	2,263
PECO Energy Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(7)	4	(5)	12
Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	6	6	18	18
Revenues	703	731	2,327	2,369
Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(5)	(6)	11	(23)
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	2	1	5	5
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	4	5	13	0
Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	704	732	2,303	2,379
Baltimore Gas and Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(1)	(1)	24	(10)
Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	4	3	11	11
Revenues	1,380	1,361	3,700	3,688
Pepco Holdings LLC [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(9)	(5)	4	7
Pepco Holdings LLC [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties		3
Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,386	1,363	3,689	3,673
Pepco Holdings LLC [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(6)	(2)	11	15
Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	2	2	5	5
Revenues	642	628	1,748	1,708
Potomac Electric Power Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(3)	(4)	10	6
Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	643	630	1,732	1,697
Potomac Electric Power Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(1)	(2)	16	11
Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	1	2	5	6
Revenues	319	328	987	1,001
Delmarva Power and Light Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(6)	0	(6)	5
Delmarva Power and Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	325	327	991	993
Delmarva Power and Light Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(6)	1	(4)	8
Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	1	1	2	2
Revenues	419	406	966	981
Atlantic City Electric Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	(1)	0	(4)
Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	418	407	966	985
Atlantic City Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	1	(1)	0	(4)
Electricity, US Regulated | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4,268	4,270	11,609	11,766
Electricity, US Regulated | Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,635	1,609	4,427	4,512
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,633	1,606	4,418	4,512
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	6	7	22	23
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	865	861	2,221	2,277
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	393	391	1,103	1,132
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	141	131	399	411
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	12	11	35	36
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	222	212	660	656
Electricity, US Regulated | PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	726	697	1,914	1,886
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	723	696	1,907	1,881
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4	3	10	10
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	479	458	1,231	1,199
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	109	108	304	306
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	63	64	163	174
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9	7	23	21
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	63	59	186	181
Electricity, US Regulated | Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	623	652	1,814	1,847
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	621	649	1,809	1,842
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	4	10	10
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	352	366	1,019	1,054
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	64	68	193	196
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	116	117	335	325
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	7	7	20	21
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	82	91	242	246
Electricity, US Regulated | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,365	1,340	3,570	3,541
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,366	1,339	3,574	3,544
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	3	7	8
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	741	726	1,816	1,839
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	147	140	387	370
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	297	303	843	845
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	17	14	47	44
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	164	156	481	446
Electricity, US Regulated | Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	643	630	1,733	1,697
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	643	630	1,732	1,697
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	2	6	5
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	311	306	792	792
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	41	39	114	104
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	222	230	633	632
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	11	8	27	24
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	58	47	166	145
Electricity, US Regulated | Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	304	302	872	861
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	305	303	876	864
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	1	1	3
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	178	180	499	513
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	48	48	141	138
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	26	25	75	74
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	3	10	10
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	50	47	151	129
Electricity, US Regulated | Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	417	406	964	983
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	418	407	966	985
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	252	240	525	534
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	58	53	132	128
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	49	48	135	139
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	3	10	10
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	56	63	164	174
Natural Gas, US Regulated | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	163	162	1,046	1,017
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	62	57	431	382
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	62	57	431	382
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	1	0
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	38	36	285	259
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	17	15	122	102
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	1	1
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5	5	18	16
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	1	5	4
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	79	79	484	527
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	83	83	494	537
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	1	3	3
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	49	46	327	345
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9	8	55	55
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	20	17	93	88
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5	12	19	49
Natural Gas, US Regulated | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	20	23	115	129
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	20	24	115	129
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9	8	64	68
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4	5	30	31
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	2	4	7
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4	3	11	12
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	6	6	11
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	20	24	116	129
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	20	24	115	129
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	1	0
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9	8	64	68
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4	5	30	31
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	2	4	7
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4	3	11	12
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	6	6	11
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 0	$ 0	$ 0	$ 0