Exelon Generation 10-Q 8 May 20 2020 Q1 Quarterly report Financial data

Cover Page

Cover Page	3 Months Ended
	Mar. 31, 2020shares
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
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	974,407,848
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
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	127,021,353
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 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 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
DISTRICT OF COLUMBIA | Potomac Electric Power Company [Member]
Entity Incorporation, State or Country Code	DC
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
DELAWARE | Delmarva Power and Light Company [Member]
Entity Incorporation, State or Country Code	DE

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Income (Unaudited) - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Operating revenues
Revenues from alternative revenue programs		$ 67	$ (5)
Operating revenues from affiliates		1	0
Total operating revenues		8,747	9,477
Operating expenses
Operating and maintenance		2,204	2,189
Depreciation and amortization		1,021	1,075
Taxes other than income taxes		437	445
Total operating expenses		7,529	8,262
Gain on sales of assets and businesses		2	3
Operating income		1,220	1,218
Other income and (deductions)
Interest expense, net		(404)	(397)
Interest expense to affiliates		(6)	(6)
Other, net		(725)	467
Total other income and (deductions)		(1,135)	64
Income before income taxes		85	1,282
Income taxes		(294)	310
Equity in losses of unconsolidated affiliates		(3)	(6)
Net income (loss)		376	966
Net income attributable to noncontrolling interests		(206)	59
Net income (loss) attributable to common shareholders		582	907
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost		(10)	(16)
Actuarial loss reclassified to periodic benefit cost		47	36
Pension and non-pension postretirement benefit plan valuation adjustment		(7)	(38)
Unrealized (loss) gain on cash flow hedges		(1)	0
Unrealized (loss) gain on investments in unconsolidated affiliates		0	(2)
Unrealized gain (loss) on foreign currency translation		(8)	2
Other comprehensive income		21	(18)
Comprehensive income		397	948
Comprehensive (loss) income attributable to noncontrolling interests		(206)	58
Comprehensive income attributable to common shareholders/membership interest		$ 603	$ 890
Average shares of common stock outstanding:
Basic average shares of common stock outstanding		975	971
Assumed exercise and/or distributions of stock-based awards		1	1
Diluted average shares of common stock outstanding	[1]	976	972
Earnings per average common share:
Basic earnings per average common share		$ 0.60	$ 0.93
Diluted earnings per average common share		$ 0.60	$ 0.93
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		0	0
Exelon Generation Co L L C [Member]
Operating revenues
Operating revenues from affiliates		$ 330	$ 317
Total operating revenues		4,733	5,296
Operating expenses
Purchased power and/or fuel from affiliates		(6)	1
Operating and maintenance		1,121	1,068
Operating and maintenance from affiliates		142	150
Depreciation and amortization		304	405
Taxes other than income taxes		129	135
Total operating expenses		4,400	4,963
Operating income		333	333
Other income and (deductions)
Interest expense, net		(100)	(102)
Interest expense to affiliates		(9)	(9)
Other, net		(771)	430
Total other income and (deductions)		(880)	319
Income before income taxes		(547)	652
Income taxes		(389)	224
Equity in losses of unconsolidated affiliates		(3)	(6)
Net income (loss)		(161)	422
Net income attributable to noncontrolling interests		(206)	59
Net income attributable to membership interest		45	363
Other comprehensive income (loss), net of income taxes
Unrealized (loss) gain on cash flow hedges		(1)	1
Unrealized (loss) gain on investments in unconsolidated affiliates		0	(2)
Unrealized gain (loss) on foreign currency translation		(8)	2
Other comprehensive income		(9)	1
Comprehensive income		(170)	423
Comprehensive (loss) income attributable to noncontrolling interests		(206)	58
Comprehensive income attributable to common shareholders/membership interest		36	365
Commonwealth Edison Co [Member]
Operating revenues
Revenues from alternative revenue programs		12	(28)
Operating revenues from affiliates		5	4
Total operating revenues		1,439	1,408
Operating expenses
Purchased power and/or fuel from affiliates		97	97
Operating and maintenance		243	259
Operating and maintenance from affiliates		74	62
Depreciation and amortization		273	251
Taxes other than income taxes		75	78
Total operating expenses		1,151	1,135
Gain on sales of assets and businesses		0	3
Operating income		288	276
Other income and (deductions)
Interest expense, net		(91)	(84)
Interest expense to affiliates		(3)	(3)
Other, net		10	8
Total other income and (deductions)		(84)	(79)
Income before income taxes		204	197
Income taxes		36	40
Net income (loss)		168	157
Other comprehensive income (loss), net of income taxes
Comprehensive income		168	157
PECO Energy Co [Member]
Operating revenues
Revenues from alternative revenue programs		2	(3)
Operating revenues from affiliates		2	1
Total operating revenues		813	900
Operating expenses
Purchased power and/or fuel from affiliates		36	44
Operating and maintenance		179	187
Operating and maintenance from affiliates		38	38
Depreciation and amortization		86	81
Taxes other than income taxes		39	41
Total operating expenses		625	678
Operating income		188	222
Other income and (deductions)
Interest expense, net		(33)	(30)
Interest expense to affiliates		(3)	(3)
Other, net		3	4
Total other income and (deductions)		(33)	(29)
Income before income taxes		155	193
Income taxes		15	25
Net income (loss)		140	168
Other comprehensive income (loss), net of income taxes
Comprehensive income		140	168
Baltimore Gas and Electric Company [Member]
Operating revenues
Revenues from alternative revenue programs		36	10
Operating revenues from affiliates			6
Total operating revenues		937	976
Operating expenses
Purchased power and/or fuel from affiliates		98	75
Operating and maintenance		146	153
Operating and maintenance from affiliates		42	39
Depreciation and amortization		143	136
Taxes other than income taxes		69	68
Total operating expenses		688	756
Operating income		249	220
Other income and (deductions)
Interest expense, net		(32)	(29)
Other, net		5	5
Total other income and (deductions)		(27)	(24)
Income before income taxes		222	196
Income taxes		41	36
Net income (loss)		181	160
Other comprehensive income (loss), net of income taxes
Comprehensive income		181	160
Pepco Holdings LLC [Member]
Operating revenues
Revenues from alternative revenue programs		18	15
Operating revenues from affiliates		3	3
Total operating revenues		1,171	1,228
Operating expenses
Purchased power and/or fuel from affiliates		104	101
Operating and maintenance		219	239
Operating and maintenance from affiliates		38	33
Depreciation and amortization		194	180
Taxes other than income taxes		114	111
Total operating expenses		1,000	1,053
Gain on sales of assets and businesses		2	0
Operating income		173	175
Other income and (deductions)
Interest expense, net		(67)	(65)
Other, net		13	12
Total other income and (deductions)		(54)	(53)
Income before income taxes		119	122
Income taxes		11	5
Net income (loss)		108	117
Other comprehensive income (loss), net of income taxes
Comprehensive income attributable to common shareholders/membership interest		108	117
Potomac Electric Power Company [Member]
Operating revenues
Revenues from alternative revenue programs		15	14
Operating revenues from affiliates		1	2
Total operating revenues		544	575
Operating expenses
Purchased power and/or fuel from affiliates		79	70
Operating and maintenance		60	64
Operating and maintenance from affiliates		51	54
Depreciation and amortization		95	94
Taxes other than income taxes		92	92
Total operating expenses		462	491
Operating income		82	84
Other income and (deductions)
Interest expense, net		(34)	(34)
Other, net		9	7
Total other income and (deductions)		(25)	(27)
Income before income taxes		57	57
Income taxes		5	2
Net income (loss)		52	55
Other comprehensive income (loss), net of income taxes
Comprehensive income attributable to common shareholders/membership interest		52	55
Delmarva Power and Light Company [Member]
Operating revenues
Revenues from alternative revenue programs		1	0
Operating revenues from affiliates		2	2
Total operating revenues		350	380
Operating expenses
Purchased power and/or fuel from affiliates		22	23
Operating and maintenance		42	45
Operating and maintenance from affiliates		37	39
Depreciation and amortization		48	46
Taxes other than income taxes		16	14
Total operating expenses		284	308
Operating income		66	72
Other income and (deductions)
Interest expense, net		(16)	(15)
Other, net		2	3
Total other income and (deductions)		(14)	(12)
Income before income taxes		52	60
Income taxes		7	7
Net income (loss)		45	53
Other comprehensive income (loss), net of income taxes
Comprehensive income		45	53
Atlantic City Electric Company [Member]
Operating revenues
Revenues from alternative revenue programs		1	1
Operating revenues from affiliates		1	1
Total operating revenues		276	273
Operating expenses
Purchased power and/or fuel from affiliates		2	8
Operating and maintenance		45	47
Operating and maintenance from affiliates		33	34
Depreciation and amortization		43	31
Taxes other than income taxes		2	1
Total operating expenses		251	252
Gain on sales of assets and businesses		2	0
Operating income		27	21
Other income and (deductions)
Interest expense, net		(14)	(14)
Interest expense to affiliates		(1)	0
Other, net		2	3
Total other income and (deductions)		(13)	(11)
Income before income taxes		14	10
Income taxes		1	0
Net income (loss)		13	10
Other comprehensive income (loss), net of income taxes
Comprehensive income		13	10
Generation commodities and services
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,403	4,979
Operating expenses
Purchased power and/or fuel		2,710	3,204
Generation commodities and services | Exelon Generation Co L L C [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,403	4,979
Operating expenses
Purchased power and/or fuel		2,710	3,204
Rate-regulated utility revenues
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,276	4,503
Operating expenses
Purchased power and/or fuel		1,157	1,349
Electricity, US Regulated | Commonwealth Edison Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		1,422	1,432
Operating expenses
Purchased power and/or fuel		389	388
Electricity, US Regulated | PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		600	622
Operating expenses
Purchased power and/or fuel		164	152
Electricity, US Regulated | Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		595	652
Operating expenses
Purchased power and/or fuel		114	190
Electricity, US Regulated | Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		1,086	1,139
Operating expenses
Purchased power and/or fuel		300	355
Electricity, US Regulated | Potomac Electric Power Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		528	559
Operating expenses
Purchased power and/or fuel		85	117
Electricity, US Regulated | Delmarva Power and Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		283	307
Operating expenses
Purchased power and/or fuel		88	107
Electricity, US Regulated | Atlantic City Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		274	271
Operating expenses
Purchased power and/or fuel		126	131
Natural Gas, US Regulated | PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		209	280
Operating expenses
Purchased power and/or fuel		83	135
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		300	308
Operating expenses
Purchased power and/or fuel		76	95
Natural Gas, US Regulated | Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		64	71
Operating expenses
Purchased power and/or fuel		31	34
Natural Gas, US Regulated | Delmarva Power and Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		64	71
Operating expenses
Purchased power and/or fuel		$ 31	$ 34
[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 months ended March 31, 2020 and March 31, 2019.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities
Net income (loss)	$ 376	$ 966
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	1,378	1,460
Asset impairments	8	7
Deferred income taxes and amortization of investment tax credits	(245)	187
Net fair value changes related to derivatives	(132)	31
Net realized and unrealized gains on NDT funds	651	(308)
Other non-cash operating activities	273	127
Changes in assets and liabilities:
Accounts receivable	800	79
Inventories	81	128
Accounts payable and accrued expenses	(976)	(764)
Option premiums (paid) received, net	(38)	6
Collateral (posted) received, net	(21)	(101)
Income taxes	(56)	141
Pension and non-pension postretirement benefit contributions	(531)	(328)
Other assets and liabilities	(488)	(587)
Net cash flows provided by operating activities	1,080	1,044
Cash flows from investing activities
Capital expenditures	(2,016)	(1,873)
Proceeds from NDT fund sales	1,183	3,713
Investment in NDT funds	(1,234)	(3,666)
Proceeds from sales of assets and businesses	0	8
Other investing activities	(8)	32
Net cash flows used in investing activities	(2,075)	(1,786)
Cash flows from financing activities
Changes in short-term borrowings	109	540
Proceeds from short-term borrowings with maturities greater than 90 days	500	0
Issuance of long-term debt	2,652	402
Retirement of long-term debt	(1,032)	(352)
Dividends paid on common stock	(373)	(352)
Proceeds from employee stock plans	30	51
Other financing activities	(21)	(14)
Net cash flows provided by (used in) financing activities	1,865	275
Increase (Decrease) in cash, cash equivalents and restricted cash	870	(467)
Cash, cash equivalents and restricted cash at beginning of period	1,122	1,781
Cash, cash equivalents and restricted cash at end of period	1,992	1,314
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(180)	(229)
Increase in PPE related to ARO update	0	301
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income (loss)	(161)	422
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	661	789
Asset impairments	8	7
Deferred income taxes and amortization of investment tax credits	(329)	108
Net fair value changes related to derivatives	(127)	33
Net realized and unrealized gains on NDT funds	651	(308)
Other non-cash operating activities	205	(90)
Changes in assets and liabilities:
Accounts receivable	787	197
Receivables from and payables to affiliates, net	34	(5)
Inventories	39	103
Accounts payable and accrued expenses	(614)	(411)
Option premiums (paid) received, net	(38)	6
Collateral (posted) received, net	(22)	(87)
Income taxes	(58)	146
Pension and non-pension postretirement benefit contributions	(232)	(141)
Other assets and liabilities	(184)	(187)
Net cash flows provided by operating activities	620	582
Cash flows from investing activities
Capital expenditures	(558)	(511)
Proceeds from NDT fund sales	1,183	3,713
Investment in NDT funds	(1,234)	(3,666)
Proceeds from sales of assets and businesses	0	8
Changes in Exelon/PHI intercompany money pool	(254)	0
Other investing activities	(8)	23
Net cash flows used in investing activities	(871)	(433)
Cash flows from financing activities
Changes in short-term borrowings	275	0
Proceeds from short-term borrowings with maturities greater than 90 days	500	0
Issuance of long-term debt	1,502	2
Retirement of long-term debt	(1,028)	(47)
Changes in Exelon/PHI intercompany money pool	0	(100)
Distributions to member	(468)	(225)
Other financing activities	(8)	(6)
Net cash flows provided by (used in) financing activities	773	(376)
Increase (Decrease) in cash, cash equivalents and restricted cash	522	(227)
Cash, cash equivalents and restricted cash at beginning of period	449	903
Cash, cash equivalents and restricted cash at end of period	971	676
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(56)	(93)
Increase in PPE related to ARO update	0	301
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income (loss)	168	157
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	273	251
Deferred income taxes and amortization of investment tax credits	42	34
Other non-cash operating activities	16	56
Changes in assets and liabilities:
Accounts receivable	9	14
Receivables from and payables to affiliates, net	(6)	(34)
Inventories	(2)	(3)
Accounts payable and accrued expenses	(147)	(188)
Collateral (posted) received, net	3	(13)
Income taxes	(7)	5
Pension and non-pension postretirement benefit contributions	(143)	(67)
Other assets and liabilities	(132)	(121)
Net cash flows provided by operating activities	74	91
Cash flows from investing activities
Capital expenditures	(506)	(503)
Other investing activities	5	11
Net cash flows used in investing activities	(501)	(492)
Cash flows from financing activities
Changes in short-term borrowings	(130)	322
Issuance of long-term debt	1,000	400
Retirement of long-term debt	0	(300)
Dividends paid on common stock	(125)	(127)
Contributions from parent	125	63
Other financing activities	(13)	(9)
Net cash flows provided by (used in) financing activities	857	349
Increase (Decrease) in cash, cash equivalents and restricted cash	430	(52)
Cash, cash equivalents and restricted cash at beginning of period	403	330
Cash, cash equivalents and restricted cash at end of period	833	278
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(5)	(80)
PECO Energy Co [Member]
Cash flows from operating activities
Net income (loss)	140	168
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	86	81
Deferred income taxes and amortization of investment tax credits	2	5
Other non-cash operating activities	22	16
Changes in assets and liabilities:
Accounts receivable	14	(86)
Receivables from and payables to affiliates, net	(3)	7
Inventories	15	23
Accounts payable and accrued expenses	(45)	(13)
Income taxes	14	20
Pension and non-pension postretirement benefit contributions	(16)	(25)
Other assets and liabilities	(84)	(119)
Net cash flows provided by operating activities	145	77
Cash flows from investing activities
Capital expenditures	(259)	(222)
Changes in Exelon/PHI intercompany money pool	(22)	0
Other investing activities	1	2
Net cash flows used in investing activities	(280)	(220)
Cash flows from financing activities
Dividends paid on common stock	(85)	(90)
Contributions from parent	231	145
Net cash flows provided by (used in) financing activities	146	55
Increase (Decrease) in cash, cash equivalents and restricted cash	11	(88)
Cash, cash equivalents and restricted cash at beginning of period	27	135
Cash, cash equivalents and restricted cash at end of period	38	47
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(11)	8
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income (loss)	181	160
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	143	136
Deferred income taxes and amortization of investment tax credits	33	28
Other non-cash operating activities	(8)	27
Changes in assets and liabilities:
Accounts receivable	(28)	(39)
Receivables from and payables to affiliates, net	(13)	(10)
Inventories	20	17
Accounts payable and accrued expenses	(9)	(27)
Collateral (posted) received, net	0	(1)
Income taxes	7	8
Pension and non-pension postretirement benefit contributions	(64)	(40)
Other assets and liabilities	10	(14)
Net cash flows provided by operating activities	272	245
Cash flows from investing activities
Capital expenditures	(283)	(258)
Other investing activities	(6)	1
Net cash flows used in investing activities	(289)	(257)
Cash flows from financing activities
Changes in short-term borrowings	66	71
Dividends paid on common stock	(62)	(56)
Net cash flows provided by (used in) financing activities	4	15
Increase (Decrease) in cash, cash equivalents and restricted cash	(13)	3
Cash, cash equivalents and restricted cash at beginning of period	25	13
Cash, cash equivalents and restricted cash at end of period	12	16
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(35)	2
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income (loss)	108	117
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	194	180
Deferred income taxes and amortization of investment tax credits	(4)	0
Other non-cash operating activities	7	35
Changes in assets and liabilities:
Accounts receivable	36	(11)
Receivables from and payables to affiliates, net	(17)	(8)
Inventories	8	(12)
Accounts payable and accrued expenses	(16)	(9)
Income taxes	15	4
Pension and non-pension postretirement benefit contributions	(27)	(6)
Other assets and liabilities	(72)	(61)
Net cash flows provided by operating activities	232	229
Cash flows from investing activities
Capital expenditures	(376)	(358)
Other investing activities	1	1
Net cash flows used in investing activities	(375)	(357)
Cash flows from financing activities
Changes in short-term borrowings	(100)	147
Issuance of long-term debt	150	0
Retirement of long-term debt	(6)	(5)
Changes in Exelon/PHI intercompany money pool	7	0
Distributions to member	(134)	(128)
Contributions from member	144	19
Other financing activities	(1)	0
Net cash flows provided by (used in) financing activities	60	33
Increase (Decrease) in cash, cash equivalents and restricted cash	(83)	(95)
Cash, cash equivalents and restricted cash at beginning of period	181	186
Cash, cash equivalents and restricted cash at end of period	98	91
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(57)	(55)
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income (loss)	52	55
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	95	94
Deferred income taxes and amortization of investment tax credits	(2)	(2)
Other non-cash operating activities	(11)	3
Changes in assets and liabilities:
Accounts receivable	14	(19)
Receivables from and payables to affiliates, net	(11)	3
Inventories	3	(14)
Accounts payable and accrued expenses	6	(2)
Income taxes	6	4
Pension and non-pension postretirement benefit contributions	(4)	(4)
Other assets and liabilities	(38)	(37)
Net cash flows provided by operating activities	110	81
Cash flows from investing activities
Capital expenditures	(180)	(144)
Changes in Exelon/PHI intercompany money pool	(114)	0
Other investing activities	(4)	1
Net cash flows used in investing activities	(298)	(143)
Cash flows from financing activities
Changes in short-term borrowings	(82)	65
Issuance of long-term debt	150	0
Dividends paid on common stock	(28)	(24)
Contributions from parent	137	14
Other financing activities	(1)	0
Net cash flows provided by (used in) financing activities	176	55
Increase (Decrease) in cash, cash equivalents and restricted cash	(12)	(7)
Cash, cash equivalents and restricted cash at beginning of period	63	53
Cash, cash equivalents and restricted cash at end of period	51	46
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(43)	(15)
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income (loss)	45	53
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	48	46
Deferred income taxes and amortization of investment tax credits	0	1
Other non-cash operating activities	2	11
Changes in assets and liabilities:
Accounts receivable	14	(5)
Receivables from and payables to affiliates, net	(9)	(15)
Inventories	3	1
Accounts payable and accrued expenses	4	11
Income taxes	7	5
Other assets and liabilities	(10)	(10)
Net cash flows provided by operating activities	104	98
Cash flows from investing activities
Capital expenditures	(95)	(78)
Other investing activities	(4)	0
Net cash flows used in investing activities	(99)	(78)
Cash flows from financing activities
Changes in short-term borrowings	(2)	5
Changes in Exelon/PHI intercompany money pool	37	0
Dividends paid on common stock	(52)	(41)
Contributions from parent	6	0
Net cash flows provided by (used in) financing activities	(11)	(36)
Increase (Decrease) in cash, cash equivalents and restricted cash	(6)	(16)
Cash, cash equivalents and restricted cash at beginning of period	13	24
Cash, cash equivalents and restricted cash at end of period	7	8
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(9)	(17)
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income (loss)	13	10
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	43	31
Deferred income taxes and amortization of investment tax credits	(1)	0
Other non-cash operating activities	4	5
Changes in assets and liabilities:
Accounts receivable	11	13
Receivables from and payables to affiliates, net	3	(4)
Inventories	2	1
Accounts payable and accrued expenses	3	12
Income taxes	2	(1)
Pension and non-pension postretirement benefit contributions	(2)	0
Other assets and liabilities	(22)	(7)
Net cash flows provided by operating activities	56	60
Cash flows from investing activities
Capital expenditures	(101)	(128)
Other investing activities	6	0
Net cash flows used in investing activities	(95)	(128)
Cash flows from financing activities
Changes in short-term borrowings	(16)	77
Retirement of long-term debt	(5)	(4)
Changes in Exelon/PHI intercompany money pool	77	0
Dividends paid on common stock	(23)	(12)
Contributions from parent	1	5
Net cash flows provided by (used in) financing activities	34	66
Increase (Decrease) in cash, cash equivalents and restricted cash	(5)	(2)
Cash, cash equivalents and restricted cash at beginning of period	28	30
Cash, cash equivalents and restricted cash at end of period	23	28
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	$ (4)	$ (24)

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Current Assets
Cash and cash equivalents		$ 1,457	$ 587
Restricted cash and cash equivalents		414	358
Accounts receivable
Customer accounts receivable		4,320	4,835
Customer allowance for credit losses		(278)	(243)
Customer accounts receivable, net		4,042	4,592
Other accounts receivable		1,391	1,631
Other allowance for credit losses		(52)	(48)
Other accounts receivable, net		1,339	1,583
Mark-to-market derivative assets, current		656	679
Unamortized energy contract assets, current		47	47
Inventories, net
Fossil fuel and emission allowances		224	312
Materials and supplies		1,463	1,456
Regulatory assets, current		1,205	1,170
Other		1,629	1,253
Total current assets		12,476	12,037
Property, plant and equipment, net		81,017	80,233
Deferred debits and other assets
Regulatory assets, noncurrent		8,360	8,335
Nuclear decommissioning trust funds		11,611	13,190
Investments		418	464
Goodwill		6,677	6,677
Mark-to-market derivative assets, noncurrent		625	508
Unamortized energy contract assets, noncurrent		329	336
Other		3,164	3,197
Total deferred debits and other assets		31,184	32,707
Total assets	[1]	124,677	124,977
Current Liabilities
Short-term borrowings		1,979	1,370
Long-term debt due within one year		2,848	4,710
Accounts payable		2,883	3,560
Accrued expenses		1,535	1,981
Payable to affiliates, current		5	5
Regulatory liabilities, current		412	406
Mark-to-market derivative liabilities, current		264	247
Unamortized energy contract liabilities, current		121	132
Renewable energy credit obligation		451	443
Other		1,276	1,331
Total current liabilities		11,774	14,185
Long-term debt		34,808	31,329
Long-term debt to financing trusts		390	390
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		12,242	12,351
Asset retirement obligations, noncurrent		10,951	10,846
Pension obligations		3,705	4,247
Non-pension postretirement benefit obligations		2,112	2,076
Spent nuclear fuel obligation		1,204	1,199
Regulatory liabilities, noncurrent		9,105	9,986
Mark-to-market derivative liabilities, noncurrent		436	393
Unamortized energy contract liabilities, noncurrent		317	338
Other		3,017	3,064
Total deferred credits and other liabilities		43,089	44,500
Total liabilities	[1]	90,061	90,404
Commitments and contingencies
Shareholders' equity
Common stock		19,303	19,274
Treasury stock, at cost		(123)	(123)
Retained earnings/Undistributed earnings		16,475	16,267
Accumulated other comprehensive loss, net		(3,173)	(3,194)
Total shareholders’ equity		32,482	32,224
Member’s equity
Noncontrolling Interests		2,134	2,349
Total equity		34,616	34,573
Total liabilities and shareholders’ equity		124,677	124,977
Variable Interest Entity, Consolidated, Assets, Pledged		9,056	9,532
Variable Interest Entity, Consolidated, Liabilities, No Recourse		3,412	3,473
Exelon Generation Co L L C [Member]
Current Assets
Cash and cash equivalents		821	303
Restricted cash and cash equivalents		150	146
Accounts receivable
Customer accounts receivable		2,496	2,973
Customer allowance for credit losses		(81)	(80)
Customer accounts receivable, net		2,415	2,893
Other accounts receivable		353	619
Other accounts receivable, net		353	619
Mark-to-market derivative assets, current		650	675
Receivable from affiliates, current		167	190
Receivable from Exelon intercompany pool		254	0
Unamortized energy contract assets, current		47	47
Inventories, net
Fossil fuel and emission allowances		186	236
Materials and supplies		1,038	1,026
Other		1,243	941
Total current assets		7,324	7,076
Property, plant and equipment, net		24,169	24,193
Deferred debits and other assets
Nuclear decommissioning trust funds		11,611	13,190
Investments		189	235
Goodwill		47	47
Mark-to-market derivative assets, noncurrent		625	508
Prepaid pension asset		1,638	1,438
Unamortized energy contract assets, noncurrent		328	336
Deferred income taxes		10	12
Other		1,941	1,960
Total deferred debits and other assets		16,389	17,726
Total assets	[2]	47,882	48,995
Current Liabilities
Short-term borrowings		1,095	320
Long-term debt due within one year		1,623	2,624
Long-term debt to affiliates due within one year		556	558
Accounts payable		1,195	1,692
Accrued expenses		603	786
Payable to affiliates, current		128	117
Mark-to-market derivative liabilities, current		229	215
Unamortized energy contract liabilities, current		12	17
Renewable energy credit obligation		450	443
Other		434	517
Total current liabilities		6,325	7,289
Long-term debt		5,943	4,464
Long-term debt to affiliates		327	328
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		3,424	3,752
Asset retirement obligations, noncurrent		10,709	10,603
Non-pension postretirement benefit obligations		873	878
Spent nuclear fuel obligation		1,204	1,199
Payables to affiliates, noncurrent		2,302	3,103
Mark-to-market derivative liabilities, noncurrent		158	123
Unamortized energy contract liabilities, noncurrent		10	11
Other		1,424	1,415
Total deferred credits and other liabilities		20,104	21,084
Total liabilities	[2]	32,699	33,165
Commitments and contingencies
Shareholders' equity
Retained earnings/Undistributed earnings		3,527	3,950
Accumulated other comprehensive loss, net		(41)	(32)
Member’s equity
Membership interest		9,568	9,566
Total members' equity		13,054	13,484
Noncontrolling Interests		2,129	2,346
Total equity		15,183	15,830
Total liabilities and shareholders’ equity		47,882	48,995
Variable Interest Entity, Consolidated, Assets, Pledged		9,034	9,512
Variable Interest Entity, Consolidated, Liabilities, No Recourse		3,369	3,429
Commonwealth Edison Co [Member]
Current Assets
Cash and cash equivalents		514	90
Restricted cash and cash equivalents		211	150
Accounts receivable
Customer accounts receivable		600	604
Customer allowance for credit losses		(71)	(59)
Customer accounts receivable, net		529	545
Other accounts receivable		307	306
Other allowance for credit losses		(22)	(20)
Other accounts receivable, net		285	286
Receivable from affiliates, current		18	28
Inventories, net
Inventories, net		161	159
Regulatory assets, current		290	281
Other		51	44
Total current assets		2,059	1,583
Property, plant and equipment, net		23,390	23,107
Deferred debits and other assets
Regulatory assets, noncurrent		1,567	1,480
Investments		6	6
Goodwill		2,625	2,625
Receivable from affiliates, noncurrent		2,040	2,622
Prepaid pension asset		1,108	995
Other		351	347
Total deferred debits and other assets		7,697	8,075
Total assets		33,146	32,765
Current Liabilities
Short-term borrowings		0	130
Long-term debt due within one year		500	500
Accounts payable		503	527
Accrued expenses		258	385
Payable to affiliates, current		87	103
Customer deposits		118	118
Regulatory liabilities, current		186	200
Mark-to-market derivative liabilities, current		36	32
Other		117	122
Total current liabilities		1,805	2,117
Long-term debt		8,978	7,991
Long-term debt to financing trusts		205	205
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		4,094	4,021
Asset retirement obligations, noncurrent		128	128
Non-pension postretirement benefit obligations		178	180
Regulatory liabilities, noncurrent		5,960	6,542
Mark-to-market derivative liabilities, noncurrent		278	269
Other		675	635
Total deferred credits and other liabilities		11,313	11,775
Total liabilities		22,301	22,088
Commitments and contingencies
Shareholders' equity
Common stock		1,588	1,588
Other paid-in capital		7,697	7,572
Retained deficit unappropriated		(1,639)	(1,639)
Retained earnings appropriated		3,199	3,156
Total shareholders’ equity		10,845	10,677
Member’s equity
Total liabilities and shareholders’ equity		33,146	32,765
PECO Energy Co [Member]
Current Assets
Cash and cash equivalents		31	21
Restricted cash and cash equivalents		7	6
Accounts receivable
Customer accounts receivable		394	412
Customer allowance for credit losses		(66)	(55)
Customer accounts receivable, net		328	357
Other accounts receivable		128	145
Other allowance for credit losses		(7)	(7)
Other accounts receivable, net		121	138
Receivable from affiliates, current		0	1
Receivable from Exelon intercompany pool		90	68
Inventories, net
Fossil fuel and emission allowances		21	36
Materials and supplies		35	35
Prepaid utility taxes		101	0
Regulatory assets, current		35	41
Other		20	19
Total current assets		789	722
Property, plant and equipment, net		9,462	9,292
Deferred debits and other assets
Regulatory assets, noncurrent		588	554
Investments		25	27
Receivable from affiliates, noncurrent		261	480
Prepaid pension asset		380	365
Other		30	29
Total deferred debits and other assets		1,284	1,455
Total assets		11,535	11,469
Current Liabilities
Accounts payable		357	387
Accrued expenses		76	101
Payable to affiliates, current		51	55
Customer deposits		70	69
Regulatory liabilities, current		104	91
Other		27	19
Total current liabilities		685	722
Long-term debt		3,406	3,405
Long-term debt to financing trusts		184	184
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,119	2,080
Asset retirement obligations, noncurrent		26	28
Non-pension postretirement benefit obligations		288	288
Regulatory liabilities, noncurrent		290	510
Other		73	74
Total deferred credits and other liabilities		2,796	2,980
Total liabilities		7,071	7,291
Commitments and contingencies
Shareholders' equity
Common stock		2,997	2,766
Retained earnings/Undistributed earnings		1,467	1,412
Total shareholders’ equity		4,464	4,178
Member’s equity
Total liabilities and shareholders’ equity		11,535	11,469
Baltimore Gas and Electric Company [Member]
Current Assets
Cash and cash equivalents		11	24
Restricted cash and cash equivalents		1	1
Accounts receivable
Customer accounts receivable		358	329
Customer allowance for credit losses		(18)	(12)
Customer accounts receivable, net		340	317
Other accounts receivable		143	152
Other allowance for credit losses		(5)	(5)
Other accounts receivable, net		138	147
Receivable from affiliates, current		1	1
Inventories, net
Fossil fuel and emission allowances		13	30
Materials and supplies		43	46
Prepaid utility taxes		40	78
Regulatory assets, current		201	183
Other		5	6
Total current assets		793	833
Property, plant and equipment, net		9,147	8,990
Deferred debits and other assets
Regulatory assets, noncurrent		453	454
Investments		7	7
Prepaid pension asset		308	264
Other		81	86
Total deferred debits and other assets		849	811
Total assets		10,789	10,634
Current Liabilities
Short-term borrowings		141	76
Accounts payable		224	243
Accrued expenses		127	152
Payable to affiliates, current		52	66
Customer deposits		119	120
Regulatory liabilities, current		39	33
Other		78	63
Total current liabilities		780	753
Long-term debt		3,271	3,270
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		1,457	1,396
Asset retirement obligations, noncurrent		22	22
Non-pension postretirement benefit obligations		194	199
Regulatory liabilities, noncurrent		1,163	1,195
Other		100	116
Total deferred credits and other liabilities		2,936	2,928
Total liabilities		6,987	6,951
Commitments and contingencies
Shareholders' equity
Common stock		1,907	1,907
Retained earnings/Undistributed earnings		1,895	1,776
Total shareholders’ equity		3,802	3,683
Member’s equity
Total liabilities and shareholders’ equity		10,789	10,634
Pepco Holdings LLC [Member]
Current Assets
Cash and cash equivalents		49	131
Restricted cash and cash equivalents		37	36
Accounts receivable
Customer accounts receivable		471	516
Customer allowance for credit losses		(42)	(37)
Customer accounts receivable, net		429	479
Other accounts receivable		197	190
Other allowance for credit losses		(18)	(16)
Other accounts receivable, net		179	174
Receivable from affiliates, current		1	1
Inventories, net
Fossil fuel and emission allowances		3	8
Materials and supplies		187	190
Regulatory assets, current		427	412
Other		57	49
Total current assets		1,369	1,480
Property, plant and equipment, net		14,491	14,296
Deferred debits and other assets
Regulatory assets, noncurrent		2,012	2,061
Investments		135	135
Goodwill		4,005	4,005
Prepaid pension asset		412	406
Deferred income taxes		13	13
Other		316	323
Total deferred debits and other assets		6,893	6,943
Total assets	[3]	22,753	22,719
Current Liabilities
Short-term borrowings		108	208
Long-term debt due within one year		144	103
Accounts payable		423	462
Accrued expenses		280	296
Payable to affiliates, current		82	98
Borrowings from Exelon/PHI intercompany money pool		19	12
Customer deposits		117	117
Regulatory liabilities, current		70	70
Unamortized energy contract liabilities, current		109	115
Other		129	131
Total current liabilities		1,481	1,612
Long-term debt		6,564	6,460
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,302	2,278
Asset retirement obligations, noncurrent		57	57
Non-pension postretirement benefit obligations		89	93
Regulatory liabilities, noncurrent		1,675	1,707
Unamortized energy contract liabilities, noncurrent		307	327
Other		552	577
Total deferred credits and other liabilities		4,982	5,039
Total liabilities	[3]	13,027	13,111
Commitments and contingencies
Shareholders' equity
Retained earnings/Undistributed earnings		(36)	(10)
Member’s equity
Membership interest		9,762	9,618
Total members' equity		9,726	9,608
Total equity		9,726	9,608
Total liabilities and shareholders’ equity		22,753	22,719
Variable Interest Entity, Consolidated, Assets, Pledged		22	20
Variable Interest Entity, Consolidated, Liabilities, No Recourse		43	44
Potomac Electric Power Company [Member]
Current Assets
Cash and cash equivalents		18	30
Restricted cash and cash equivalents		33	33
Accounts receivable
Customer accounts receivable		225	244
Customer allowance for credit losses		(15)	(13)
Customer accounts receivable, net		210	231
Other accounts receivable		102	98
Other allowance for credit losses		(8)	(7)
Other accounts receivable, net		94	91
Receivable from Exelon intercompany pool		114	0
Inventories, net
Inventories, net		109	112
Regulatory assets, current		198	188
Other		24	11
Total current assets		800	696
Property, plant and equipment, net		7,002	6,909
Deferred debits and other assets
Regulatory assets, noncurrent		567	584
Investments		111	110
Prepaid pension asset		293	296
Other		64	66
Total deferred debits and other assets		1,035	1,056
Total assets		8,837	8,661
Current Liabilities
Short-term borrowings		0	82
Long-term debt due within one year		3	2
Accounts payable		171	195
Accrued expenses		151	156
Payable to affiliates, current		55	66
Customer deposits		57	57
Regulatory liabilities, current		12	8
Merger related obligation		39	39
Current portion of DC PLUG obligation		30	30
Other		22	22
Total current liabilities		540	657
Long-term debt		3,012	2,862
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		1,143	1,131
Asset retirement obligations, noncurrent		41	41
Non-pension postretirement benefit obligations		16	20
Regulatory liabilities, noncurrent		731	746
Other		286	297
Total deferred credits and other liabilities		2,217	2,235
Total liabilities		5,769	5,754
Commitments and contingencies
Shareholders' equity
Common stock		1,933	1,796
Retained earnings/Undistributed earnings		1,135	1,111
Total shareholders’ equity		3,068	2,907
Member’s equity
Total liabilities and shareholders’ equity		8,837	8,661
Delmarva Power and Light Company [Member]
Current Assets
Cash and cash equivalents		7	13
Restricted cash and cash equivalents		0	0
Accounts receivable
Customer accounts receivable		139	152
Customer allowance for credit losses		(13)	(11)
Customer accounts receivable, net		126	141
Other accounts receivable		40	42
Other allowance for credit losses		(4)	(4)
Other accounts receivable, net		36	38
Receivable from affiliates, current		1	0
Inventories, net
Fossil fuel and emission allowances		3	8
Materials and supplies		46	44
Prepaid utility taxes		9	18
Regulatory assets, current		50	52
Renewable Energy Credits, Current		16	9
Other		2	2
Total current assets		296	325
Property, plant and equipment, net		4,088	4,035
Deferred debits and other assets
Regulatory assets, noncurrent		221	222
Goodwill		8	8
Prepaid pension asset		169	171
Other		67	69
Total deferred debits and other assets		465	470
Total assets		4,849	4,830
Current Liabilities
Short-term borrowings		54	56
Long-term debt due within one year		81	80
Accounts payable		98	112
Accrued expenses		62	46
Payable to affiliates, current		21	32
Borrowings from Exelon/PHI intercompany money pool		37	0
Customer deposits		35	36
Regulatory liabilities, current		35	37
Other		14	15
Total current liabilities		437	414
Long-term debt		1,494	1,487
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		665	655
Non-pension postretirement benefit obligations		15	16
Regulatory liabilities, noncurrent		561	574
Other		98	104
Total deferred credits and other liabilities		1,339	1,349
Total liabilities		3,270	3,250
Commitments and contingencies
Shareholders' equity
Common stock		983	977
Retained earnings/Undistributed earnings		596	603
Total shareholders’ equity		1,579	1,580
Member’s equity
Total liabilities and shareholders’ equity		4,849	4,830
Atlantic City Electric Company [Member]
Current Assets
Cash and cash equivalents		8	12
Restricted cash and cash equivalents		3	2
Accounts receivable
Customer accounts receivable		106	121
Customer allowance for credit losses		(14)	(13)
Customer accounts receivable, net		92	108
Other accounts receivable		54	53
Other allowance for credit losses		(6)	(5)
Other accounts receivable, net		48	48
Receivable from affiliates, current		4	4
Inventories, net
Inventories, net		32	34
Regulatory assets, current		71	57
Other		3	5
Total current assets		261	270
Property, plant and equipment, net		3,249	3,190
Deferred debits and other assets
Regulatory assets, noncurrent		366	368
Prepaid pension asset		51	52
Other		51	53
Total deferred debits and other assets		468	473
Total assets	[4]	3,978	3,933
Current Liabilities
Short-term borrowings		54	70
Long-term debt due within one year		60	20
Accounts payable		145	144
Accrued expenses		40	42
Payable to affiliates, current		27	25
Borrowings from Exelon/PHI intercompany money pool		77	0
Customer deposits		25	25
Regulatory liabilities, current		24	25
Other		8	9
Total current liabilities		460	360
Long-term debt		1,265	1,307
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		580	577
Non-pension postretirement benefit obligations		17	17
Regulatory liabilities, noncurrent		352	357
Other		37	39
Total deferred credits and other liabilities		986	990
Total liabilities	[4]	2,711	2,657
Commitments and contingencies
Shareholders' equity
Common stock		1,155	1,154
Retained earnings/Undistributed earnings		112	122
Total shareholders’ equity		1,267	1,276
Member’s equity
Total liabilities and shareholders’ equity		3,978	3,933
Variable Interest Entity, Consolidated, Assets, Pledged		15	17
Variable Interest Entity, Consolidated, Liabilities, No Recourse		$ 36	$ 41
[1]	Exelon’s consolidated assets include $9,056 million and $9,532 million at March 31, 2020 and December 31, 2019 , respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,412 million and $3,473 million at March 31, 2020 and December 31, 2019 , respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 16 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $9,034 million and $9,512 million at March 31, 2020 and December 31, 2019 , respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,369 million and $3,429 million at March 31, 2020 and December 31, 2019 , respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 16 — Variable Interest Entities for additional information.
[3]	PHI’s consolidated total assets include $22 million and $20 million at March 31, 2020 and December 31, 2019 , respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $43 million and $44 million at March 31, 2020 and December 31, 2019 , respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 16 — Variable Interest Entities for additional information.
[4]	ACE’s consolidated total assets include $15 million and $17 million at March 31, 2020 and December 31, 2019 , respectively, of ACE's consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated total liabilities include $36 million and $41 million at March 31, 2020 and December 31, 2019 , respectively, of ACE's consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 16 — Variable Interest Entities for additional information.

Consolidated Balance Sheets (_2

Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) shares in Millions, $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Accumulated depreciation and amortization	$ 24,449	$ 23,979
Common Stock, Shares Authorized	2,000	2,000
Common Stock, Shares, Outstanding	974	973
Treasury Stock, Shares held	2	2
Exelon Generation Co L L C [Member]
Accumulated depreciation and amortization	$ 12,114	$ 12,017
Commonwealth Edison Co [Member]
Accumulated depreciation and amortization	5,315	5,168
PECO Energy Co [Member]
Accumulated depreciation and amortization	3,753	3,718
Baltimore Gas and Electric Company [Member]
Accumulated depreciation and amortization	3,898	3,834
Pepco Holdings LLC [Member]
Accumulated depreciation and amortization	1,319	1,213
Potomac Electric Power Company [Member]
Accumulated depreciation and amortization	3,561	3,517
Delmarva Power and Light Company [Member]
Accumulated depreciation and amortization	1,452	1,425
Atlantic City Electric Company [Member]
Accumulated depreciation and amortization	$ 1,236	$ 1,210

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]	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, 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													$ 10,247	$ 1,588	$ 7,322	$ (1,639)	$ 2,976		$ 3,820	$ 2,578	$ 1,242	$ 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 (loss)	$ 966			907		59		422		363		59	157			157			168		168	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)
Distributions to member								(225)		(225)															(128)		(128)
Contributions from parent													63		63				145	145					19	19		14	14					5	5
Other comprehensive income (loss), net of income taxes	$ (18)				(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	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]
Appropriation of retained earnings for future dividends																(157)	157	$ 0
Appropriation of retained earnings for future dividends													3,156
Beginning balance (in shares) at Dec. 31, 2019	974,416
Beginning balance at Dec. 31, 2019	$ 34,573	19,274	(123)	16,267	(3,194)	2,349
Beginning Balance at Dec. 31, 2019								15,830	9,566	3,950	(32)	2,346													9,608	9,618	(10)
Beginning Balance at Dec. 31, 2019	32,224												10,677	1,588	7,572	(1,639)	3,156		4,178	2,766	1,412	3,683	1,907	1,776				2,907	1,796	1,111	1,580	977	603	1,276	1,154	122
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 376			582		(206)		(161)		45		(206)	168			168			140		140	181		181	108		108	52		52	45		45	13		13
Stock issued during period, shares, long-term incentive plan activity	1,354
Stock issued during period, value, long-term incentive plan activity	$ (4)	(4)	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	470
Stock issued during period, value, employee stock purchase plan	$ 31	31	0	0	0	0
Changes in equity of noncontrolling interests	(9)					(9)		(11)				(11)
Sale of noncontrolling interests	2	2						2	2
Common stock dividends	(374)			(374)									(125)				(125)		(85)		(85)	(62)		(62)				(28)		(28)	(52)		(52)	(23)		(23)
Distributions to member								(468)		(468)															(134)		(134)
Contributions from parent													125		125				231	231					144	144		137	137		6	6		1	1
Other comprehensive income (loss), net of income taxes	$ 21				21		$ 21	(9)		0	(9)	0
Ending balance (in shares) at Mar. 31, 2020	976,240
Ending balance at Mar. 31, 2020	$ 34,616	$ 19,303	$ (123)	$ 16,475	$ (3,173)	$ 2,134
Ending Balance at Mar. 31, 2020								$ 15,183	$ 9,568	$ 3,527	$ (41)	$ 2,129													$ 9,726	$ 9,762	$ (36)
Ending Balance at Mar. 31, 2020	$ 32,482												10,845	$ 1,588	$ 7,697	(1,639)	3,199		$ 4,464	$ 2,997	$ 1,467	$ 3,802	$ 1,907	$ 1,895				$ 3,068	$ 1,933	$ 1,135	$ 1,579	$ 983	$ 596	$ 1,267	$ 1,155	$ 112
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Appropriation of retained earnings for future dividends													$ 3,199			$ (168)	$ 168	$ 0

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Shareholders Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Stockholders' Equity [Abstract]
Common Stock, Dividends, Per Share, Declared	$ 0.38	$ 0.36

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation and Significant Accounting Policies [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 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 March 31, 2020 and 2019 and for the three 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, 2019 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, 2020 . These C ombined 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. COVID-19 (All Registrants) The Registrants are responding to the global outbreak (pandemic) of the 2019 novel coronavirus (COVID-19) and have taken steps to mitigate the potential risks to the Registrants posed by its spread. The Registrants provide a critical service to their customers and have taken measures to keep employees who operate the business safe and minimize unnecessary risk of exposure to the virus, including extra precautions for employees who work in the field. The Registrants have implemented work from home policies where appropriate and imposed travel limitations on employees. In addition, the Registrants have updated their existing business continuity plans. Management makes estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and accompanying notes, and the amounts of revenues and expenses reported during the periods covered by those financial statements and accompanying notes. We assessed certain accounting matters that require consideration of forecasted financial information, including, but not limited to, our allowance for credit losses, the carrying value of our goodwill and other long-lived assets, in context with the information reasonably available to us and the unknown future impacts of COVID-19 as of March 31, 2020 and through the date of this report. While there were no material increases in the Registrants’ allowance for credit losses and no material impairments resulting from these assessments as of and for the quarter ended March 31, 2020, our future assessment of our current expectations at that time of the magnitude and duration of COVID-19, as well as other factors, could result in material impacts to our consolidated financial statements in future reporting periods. New Accounting Standards (All Registrants) New Accounting Standards Adopted as of January 1, 2020: The following new authoritative accounting guidance issued by the FASB was adopted as of January 1, 2020 and will be reflected by the Registrants in their consolidated financial statements beginning in the first quarter of 2020. 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 was effective January 1, 2020 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' Customer accounts receivables balances. This guidance did not have a significant impact on the Registrants’ consolidated 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. The standard was effective January 1, 2020 and must be applied on a prospective basis. Exelon, Generation, ComEd, PHI and DPL will apply the new guidance for their goodwill impairment assessments in 2020 and do not expect the updated guidance to have a material impact to their financial statements. Allowance for Credit Losses on Accounts Receivables (All Registrants) The allowance for credit losses reflects the Registrants’ best estimates of losses on the customers' accounts receivable balances based on historical experience, current information, and reasonable and supportable forecasts. The allowance for credit losses for Generation’s retail customers is based on accounts receivable aging historical experience coupled with specific identification through a credit monitoring process, which considers current conditions and forward-looking information such as industry trends, macroeconomic factors, changes in the regulatory environment, external credit ratings, publicly available news, payment status, payment history, and the exercise of collateral calls. The allowance for credit losses for Generation wholesale customers is developed using a credit monitoring process, similar to that used for retail customers. When a wholesale customer’s risk characteristics are no longer aligned with the pooled population, Generation uses specific identification to develop an allowance for credit losses. Adjustments to the allowance for credit losses are recorded in Operating and maintenance expense on Generation’s Consolidated Statements of Operations and Comprehensive Income. The allowance for credit losses for the Utility Registrants’ customers is developed by applying loss rates for each Utility Registrant, based on historical loss experience, current conditions and forward-looking risk factors, to the outstanding receivable balance by customer risk segment. Utility Registrants' customer accounts are written off consistent with approved regulatory requirements. Adjustments to the allowance for credit losses are primarily recorded to Operating and maintenance expense on the Utility Registrants' Consolidated Statements of Operations and Comprehensive Income and Regulatory assets on ComEd, BGE and ACE’s Consolidated Balance Sheets. See N ote 3 - Regulatory Matters of the 2019 Form 10-K for add i tional information regarding the regulatory recovery of credit losses on customer accounts receivable at ComEd, BGE and ACE. The Registrants have certain non-customer receivables in Other Deferred debits and other assets which primarily are with governmental agencies and other high-quality counterparties with no history of default. As such, the allowance for credit losses related to these receivables is immaterial. The Registrants monitor these balances and will record an allowance if there are indicators of a decline in credit quality.

Mergers, Acquisitions and Dispo

Mergers, Acquisitions and Dispositions (Exelon and Generation)	3 Months Ended
	Mar. 31, 2020
Business Combinations [Abstract]
Mergers, Acquisitions and Dispositions Disclosures [Text Block]	<div style="font-family:Times New Roman;font-size:10pt;"><div style="line-height:120%;padding-bottom:12px;padding-top:12px;text-align:justify;padding-left:0px;text-indent:0px;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;font-weight:bold;">Mergers, Acquisitions and Dispositions</font><font style="font-family:Arial;font-size:9pt;font-weight:bold;"> (Exelon and Generation)</font></div><div style="line-height:120%;padding-left:4px;padding-bottom:12px;padding-top:12px;text-align:justify;padding-left:0px;text-indent:0px;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;font-weight:bold;">CENG Put Option (Exelon and Generation)</font></div><div style="line-height:120%;padding-bottom:12px;padding-top:12px;text-align:justify;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">Generation owns a 50.01% membership interest in CENG, a joint venture with EDF, which wholly owns the Calvert Cliffs and Ginna nuclear stations and Nine Mile Point Unit 1, in addition to an 82% undivided ownership interest in Nine Mile Point Unit 2. CENG is 100% consolidated in Exelon's and Generation's financial statements. See Note 22 — Variable Interest Entities for additional information.</font></div><div style="line-height:120%;padding-bottom:12px;padding-top:12px;text-align:justify;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">On April 1, 2014, Generation and EDF entered into various agreements including a Nuclear Operating Services Agreement, an amended LLC Operating Agreement, an Employee Matters Agreement, and a Put Option Agreement, among others. Under the amended Operating Agreement, CENG made a $400 million special distribution to EDF and committed to make preferred distributions to Generation until Generation has received aggregate distributions of $400 million plus a return of 8.50% per annum. Under the Put Option Agreement, EDF has the option to sell its 49.99% equity interest in CENG to Generation exercisable beginning on January 1, 2016 and thereafter until June 30, 2022. On November 20, 2019, Generation received notice of EDF's intention to exercise the put option to sell its interest in CENG to Generation and the put automatically exercised on January 19, 2020 at the end of the sixty-day advance notice period.</font></div><div style="line-height:120%;padding-bottom:12px;padding-top:12px;text-align:justify;font-size:9pt;"><font style="font-family:Arial;font-size:9pt;">Under the terms of the Put Option Agreement, the purchase price is to be determined by agreement of the parties, or absent such agreement, by a third-party arbitration process. The third parties determining fair market value of EDF's 49.99% interest are to take into consideration all rights and obligations under the LLC Operating Agreement and Employee Matters Agreement including but not limited to Generation's rights with respect to any unpaid aggregate preferred distributions and the related return. As of March 31, 2020, the total unpaid aggregate preferred distributions and related return owed to Generation is </font><font style="font-family:Arial;font-size:9pt;background-color:#ffff00;">$571 million</font><font style="font-family:Arial;font-size:9pt;">. At this time, Generation cannot reasonably predict the ultimate purchase price that will be paid to EDF for its interest in CENG. The transaction will require approval by the NYPSC, the FERC and the NRC. The process and regulatory approvals could take one to two years or more to complete.</font></div></div>

Regulatory Matters (All Registr

Regulatory Matters (All Registrants)	3 Months Ended
	Mar. 31, 2020
Regulated Operations [Abstract]
Regulatory Matters (All Registrants)	Regulatory Matters (All Registrants) As discussed in Note 3 — Regulatory Matters of the Exelon 2019 Form 10-K, the Registrants are involved in rate and regulatory proceedings at the FERC and their state commissions. The following discusses developments in 2020 and updates to the 2019 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 2020 . 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) (a) April 8, 2019 $ (6 ) $ (17 ) 8.91 % December 4, 2019 January 1, 2020 __________ (a) Reflects an increase of $51 million for the initial revenue requirement for 2019 and a decrease of $68 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 6.51% , inclusive of an allowed ROE of 8.91% , reflecting the average rate on 30-year treasury notes plus 580 basis points. 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 16, 2020 $ (11 ) 8.38 % Fourth quarter of 2020 Pepco - District of Columbia (Electric) (b) May 30, 2019 (amended April 8, 2020) 147 10.3 % Fourth quarter of 2020 DPL - Maryland (Electric) December 5, 2019 (amended April 23, 2020) 17 10.3 % Third quarter of 2020 DPL - Delaware (Gas) (c) February 21, 2020 (amended March 17, 2020) 9 10.3 % First quarter of 2021 DPL - Delaware (Electric) (d) March 6, 2020 (amended April 16, 2020) 24 10.3 % First quarter of 2021 __________ (a) Reflects an increase of $51 million for the initial revenue requirement for 2020 and a decrease of $62 million related to the annual reconciliation for 2019. The revenue requirement for 2020 and annual reconciliation for 2019 provides for a weighted average debt and equity return on distribution rate base of 6.28% , inclusive of an allowed ROE of 8.38% , reflecting the average rate on 30-year treasury notes plus 580 basis points. (b) Reflects a three-year cumulative multi-year plan and total requested revenue requirement increases of $77 million , $37 million and $33 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. (c) The rates will go into effect on September 21, 2020, subject to refund. (d) The rates will go into effect on October 6, 2020, subject to refund. 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. 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. In the fourth quarter of 2017, ComEd, BGE, Pepco, DPL, and ACE fully impaired their associated transmission-related income tax regulatory asset for the portion of the income tax regulatory asset that would have been previously amortized. 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 1) BGE's rehearing request of FERC's November 16, 2017 order; and 2) February 23, 2018 (as amended on July 9, 2018) filing by ComEd, Pepco, DPL and ACE for similar recovery. 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 March 27, 2020, the Court of Appeals denied BGE’s November 2, 2018 appeal. On October 1, 2018, ComEd, BGE, Pepco, DPL, and ACE submitted filings to recover only ongoing non-TCJA amortization amounts and credit TCJA transmission-related income tax regulatory liabilities to customers for the prospective period starting on October 1, 2018. 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. On April 24, 2020, ComEd, BGE, Pepco, DPL, ACE and other parties filed a settlement agreement with FERC. The settlement agreement provides for the recovery of ongoing transmission-related income tax regulatory assets and establishes the amount and amortization period for excess deferred income taxes resulting from TCJA. The accelerated amortization will result in a reduction to Operating revenues and an offsetting reduction to Income tax expense over the remaining amortization period. While FERC has no deadline by which it must rule on the settlement, a final order from FERC is expected before the end of the third quarter of 2020. Exelon cannot predict the outcome of this proceeding. 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 $81 million , $51 million , $18 million , $12 million , $4 million , $6 million and $2 million , respectively, as of March 31, 2020 . Regulatory Assets and Liabilities The Utility Registrants' regulatory assets and liabilities have not changed materially since December 31, 2019 , unless noted below. See Note 3 — Regulatory Matters of the Exelon 2019 Form 10-K for additional information on the specific regulatory assets and liabilities. ComEd . Regulatory assets increased $96 million primarily due to an increase of $45 million in Energy Efficiency Costs, $22 million in Electric Distribution Formula Rate Annual Reconciliations and $15 million due to increased Electric Energy Costs. Regulatory liabilities decreased $596 million primarily due to a decrease of $582 million in Nuclear Decommissioning. PECO. Regulatory liabilities decreased $207 million primarily due to a decrease of $219 million in Nuclear Decommissioning offset by a $16 million increase in Electric Energy and Natural Gas Costs. 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 March 31, 2020 $ 60 $ 2 $ — $ 51 $ 7 $ 4 $ 3 $ — December 31, 2019 63 3 — 53 7 4 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) New Jersey Regulatory Matters New Jersey Clean Energy Legislation. On May 23, 2018, 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. 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 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 $18 million for the three months ended March 31, 2020 . On May 15, 2019, New Jersey Rate Counsel appealed the NJBPU's decision to the New Jersey Superior Court. Exelon and Generation cannot predict the outcome of the appeal. See Note 6 — 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 to be Generation's FitzPatrick, Ginna and Nine Mile Point nuclear facilities. 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. 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 filed a notice of appeal on November 4, 2019 and originally had until May 4, 2020 to file their brief. However, on March 17, 2020, the court suspended all filing deadlines indefinitely due to COVID-19, so the new deadline will not be known until the court lifts the suspension. See Note 6 — Early Plant Retirements for additional information related to Ginna and Nine Mile Point. Federal Regulatory Matters PJM and NYISO MOPR Proceedings. PJM and NYISO capacity markets include a Minimum Offer Price Rule (MOPR). If a resource is subjected to a MOPR, its offer is adjusted to effectively remove the revenues it receives through a government-provided financial support program - resulting in a higher offer that may not clear the capacity market. Prior to December 19, 2019, the MOPR in PJM applied only to certain new gas-fired resources. Currently, the MOPR in NYISO applies only to certain resources in downstate New York. For Generation’s facilities in PJM and NYISO that are currently receiving ZEC compensation, an expanded MOPR would require exclusion of ZEC compensation when bidding into future capacity auctions, resulting in an increased risk of these facilities not receiving capacity revenues in future auctions. While FERC issued a set of orders on MOPR in NYISO on February 20, 2020, it did not expand mitigation to include Generation's nuclear assets in upstate New York. However, FERC has taken action to expand the MOPR in PJM. Specifically, on December 19, 2019, FERC issued an order in the PJM MOPR proceeding that broadly applies the MOPR to all new and existing resources including nuclear, renewables, demand response, energy efficiency, storage and all resources owned by vertically-integrated utilities, greatly expanding the breadth and scope of PJM’s MOPR, effective as of PJM’s next capacity auction. While FERC included some limited exemptions (generally available to existing renewable, energy efficiency, demand response, storage and existing vertically-integrated utility resources) in its order, no exemptions were available to state-supported nuclear resources. In addition, FERC provided no new mechanism for accommodating state-supported resources other than the existing FRR mechanism under which an entire utility zone would be removed from PJM’s capacity auction along with sufficient resources to support the load in such zone. FERC directed PJM to make a compliance filing within 90 days, which was filed on March 18, 2020. In that filing, PJM proposes tariff language interpreting and implementing FERC's directives and proposes a schedule for resuming capacity auctions that is contingent on the timing of FERC's action on the compliance filing. FERC has no deadline for such action, and FERC could accept, reject or direct further revisions to all or part of PJM's proposed tariff revisions and auction schedule. In addition, on April 16, 2020, FERC issued orders largely denying requests for rehearing of FERC's December 2019 order and another order in this proceeding. In those orders, FERC also granted a few clarifications that will require an additional PJM compliance filing that could also delay the timing for FERC to issue its compliance order(s) and PJM to resume its capacity auctions. Unless Illinois and New Jersey can implement an FRR program in their PJM zones, the MOPR will apply to Generation's owned or jointly owned nuclear plants in those states receiving a benefit under the Illinois ZES or the New Jersey ZEC program, as applicable, increasing the risk that those units may not clear the capacity market. Exelon is currently working with PJM and other stakeholders to pursue the FRR option prior to the next capacity auction in PJM. If Illinois implements the FRR option, Generation’s Illinois nuclear plants could be removed from PJM’s capacity auction and instead supply capacity and be compensated under the FRR program, which has the potential to mitigate the current economic distress being experienced by Generation's nuclear plants in Illinois, as discussed in Note 6 - Early Plant Retirements. Implementing the FRR program in Illinois will require both legislative and regulatory changes. Legislation may be introduced in New Jersey as well. Exelon cannot predict whether such legislative and regulatory changes can be implemented prior to the next capacity auction in PJM. If Generation’s state-supported nuclear plants in PJM are subjected to the MOPR or equivalent without compensation under an FRR or similar program, it could have a material adverse impact on Exelon's and Generation's financial statements, which Exelon and Generation cannot reasonably estimate at this time. 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 October 29, 2019, Generation and MDE filed with FERC a Joint Offer of Settlement (Offer of Settlement) that would resolve all outstanding issues relating to the 401 Certification. Pursuant to the Offer of Settlement, the parties submitted Proposed License Articles to FERC to be incorporated by FERC into the new license in accordance with FERC’s discretionary authority under the Federal Power Act. Among the Proposed License Articles are modifications to river flows to improve aquatic habitat, eel passage improvements and initiatives to support rare, threatened and endangered wildlife. If FERC approves the Offer of Settlement and incorporates the Proposed License Articles into the new license without modification, then MDE would waive its rights to issue a 401 Certification and Generation would agree, pursuant to a separate agreement with MDE (MDE Settlement), to implement additional environmental protection, mitigation and enhancement measures over the anticipated 50-year term of the new license. These measures address mussel restoration and other ecological and water quality matters, among other commitments. Exelon’s commitments under the various provisions of the Offer of Settlement and MDE Settlement are not effective unless and until FERC approves the Offer of Settlement and issues the new license with the Proposed License Articles. Generation cannot currently predict when FERC will issue the new license. Peach Bottom Units 2 and 3. On July 10, 2018, Generation submitted a second 20-year license renewal application with the NRC for Peach Bottom Units 2 and 3, which was approved on March 6, 2020. Peach Bottom Units 2 and 3 are now licensed to operate through 2053 and 2054, respectively.

Revenue from Contracts with Cus

Revenue from Contracts with Customers (All Registrants)	3 Months Ended
	Mar. 31, 2020
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 4 — Revenue from Contracts with Customers of the Exelon 2019 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 Customer accounts receivable, net, 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 for the three months ended March 31, 2019 and March 31, 2020 Contract Assets Contract Liabilities Exelon Generation Exelon Generation Balance as of December 31, 2018 $ 187 $ 187 $ 27 $ 42 Consideration received or due (26 ) (26 ) 21 63 Revenues recognized (a) 26 26 (23 ) (66 ) Balance at March 31, 2019 $ 187 $ 187 $ 25 $ 39 Balance as of December 31, 2019 $ 174 $ 174 $ 33 $ 71 Consideration received or due (19 ) (19 ) 20 55 Revenues recognized (b) 17 17 (24 ) (70 ) Balance at March 31, 2020 $ 172 $ 172 $ 29 $ 56 __________ (a) Revenues recognized in the three months ended March 31, 2019 , which were included in contract liabilities at December 31, 2018 , were approximately $ 5 million for both Exelon and Generation. (b) Revenues recognized in the three months ended March 31, 2020 , which were included in contract liabilities at December 31, 2019 , were approximately $ 9 million and $ 19 million for Exelon and Generation, respectively. 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 March 31, 2020 and December 31, 2019 , 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 March 31, 2020 . 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. 2020 2021 2022 2023 2024 and thereafter Total Exelon $ 273 $ 144 $ 64 $ 45 $ 198 $ 724 Generation 330 200 79 45 198 852 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 4 — Segment Information for the presentation of the Registrant's revenue disaggregation.

Segment Information (All Regist

Segment Information (All Registrants)	3 Months Ended
	Mar. 31, 2020
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 NYISO. • 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. An analysis and reconciliation of the Registrants’ reportable segment information to the respective information in the consolidated financial statements for the three months ended March 31, 2020 and 2019 is as follows: Three Months Ended March 31, 2020 and 2019 Generation (a) ComEd PECO BGE PHI Other (b) Intersegment Exelon Operating revenues (c) : 2020 Competitive businesses electric revenues $ 3,752 $ — $ — $ — $ — $ — $ (326 ) $ 3,426 Competitive businesses natural gas revenues 672 — — — — — (3 ) 669 Competitive businesses other revenues 309 — — — — — (1 ) 308 Rate-regulated electric revenues — 1,439 604 613 1,104 — (12 ) 3,748 Rate-regulated natural gas revenues — — 209 324 64 — (2 ) 595 Shared service and other revenues — — — — 3 480 (482 ) 1 Total operating revenues $ 4,733 $ 1,439 $ 813 $ 937 $ 1,171 $ 480 $ (826 ) $ 8,747 2019 Competitive businesses electric revenues $ 4,337 $ — $ — $ — $ — $ — $ (315 ) $ 4,022 Competitive businesses natural gas revenues 879 — — — — — (1 ) 878 Competitive businesses other revenues 80 — — — — — (1 ) 79 Rate-regulated electric revenues — 1,408 620 658 1,153 — (8 ) 3,831 Rate-regulated natural gas revenues — — 280 318 71 — (4 ) 665 Shared service and other revenues — — — — 4 455 (457 ) 2 Total operating revenues $ 5,296 $ 1,408 $ 900 $ 976 $ 1,228 $ 455 $ (786 ) $ 9,477 Intersegment revenues (d) : 2020 $ 330 $ 5 $ 2 $ 6 $ 3 $ 479 $ (824 ) $ 1 2019 317 4 1 6 4 453 (785 ) — Depreciation and amortization: 2020 $ 304 $ 273 $ 86 $ 143 $ 194 $ 21 $ — $ 1,021 2019 405 251 81 136 180 22 — 1,075 Operating expenses: 2020 $ 4,400 $ 1,151 $ 625 $ 688 $ 1,000 $ 481 $ (816 ) $ 7,529 2019 4,963 1,135 678 756 1,054 459 (783 ) 8,262 Interest expense, net: 2020 $ 109 $ 94 $ 36 $ 32 $ 67 $ 72 $ — $ 410 2019 111 87 33 29 65 78 — 403 Generation (a) ComEd PECO BGE PHI Other (b) Intersegment Exelon Income (loss) before income taxes: 2020 $ (547 ) $ 204 $ 155 $ 222 $ 119 $ (69 ) $ 1 $ 85 2019 652 197 193 196 122 (78 ) — 1,282 Income Taxes: 2020 $ (389 ) $ 36 $ 15 $ 41 $ 11 $ (8 ) $ — $ (294 ) 2019 224 40 25 36 5 (20 ) — 310 Net income (loss): 2020 $ (161 ) $ 168 $ 140 $ 181 $ 108 $ (61 ) $ 1 $ 376 2019 422 157 168 160 117 (58 ) — 966 Capital Expenditures 2020 $ 558 $ 506 $ 259 $ 283 $ 376 $ 34 $ — $ 2,016 2019 511 503 222 258 358 21 — 1,873 Total assets: March 31, 2020 $ 47,882 $ 33,146 $ 11,535 $ 10,789 $ 22,753 $ 8,337 $ (9,765 ) $ 124,677 December 31, 2019 48,995 32,765 11,469 10,634 22,719 8,484 (10,089 ) 124,977 __________ (a) See Note 18 — Related Party Transactions for additional information on intersegment revenues. (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) : 2020 Rate-regulated electric revenues $ 544 $ 286 $ 276 $ — $ (2 ) $ 1,104 Rate-regulated natural gas revenues — 64 — — — 64 Shared service and other revenues — — — 93 (90 ) 3 Total operating revenues $ 544 $ 350 $ 276 $ 93 $ (92 ) $ 1,171 2019 Rate-regulated electric revenues $ 575 $ 310 $ 273 $ — $ (5 ) $ 1,153 Rate-regulated natural gas revenues — 70 — — 1 71 Shared service and other revenues — — — 106 (102 ) 4 Total operating revenues $ 575 $ 380 $ 273 $ 106 $ (106 ) $ 1,228 Intersegment revenues: 2020 $ 1 $ 2 $ 1 $ 92 $ (93 ) $ 3 2019 2 2 1 105 (106 ) 4 Depreciation and amortization: 2020 $ 95 $ 48 $ 43 $ 9 $ (1 ) $ 194 2019 94 46 31 10 (1 ) 180 Operating expenses: 2020 $ 462 $ 284 $ 251 $ 93 $ (90 ) $ 1,000 2019 491 308 252 108 (105 ) 1,054 Interest expense, net: 2020 $ 34 $ 16 $ 15 $ 3 $ (1 ) $ 67 2019 34 15 14 3 (1 ) 65 Income (loss) before income taxes: 2020 $ 57 $ 52 $ 14 $ 106 $ (110 ) $ 119 2019 57 60 10 113 (118 ) 122 Income Taxes: 2020 $ 5 $ 7 $ 1 $ (2 ) $ — $ 11 2019 2 7 — (4 ) — 5 Net income (loss): 2020 $ 52 $ 45 $ 13 $ (5 ) $ 3 $ 108 2019 55 53 10 (5 ) 4 117 Capital Expenditures 2020 $ 180 $ 95 $ 101 $ — $ — $ 376 2019 144 78 128 8 — 358 Total assets: March 31, 2020 $ 8,837 $ 4,849 $ 3,978 $ 11,241 $ (6,152 ) $ 22,753 December 31, 2019 8,661 4,830 3,933 11,105 (5,810 ) 22,719 __________ (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 March 31, 2020 Revenues from external customers (a) Intersegment Revenues Total Revenues Contracts with customers Other (b) Total Mid-Atlantic $ 1,264 $ (96 ) $ 1,168 $ 6 $ 1,174 Midwest 944 64 1,008 (6 ) 1,002 New York 335 (21 ) 314 — 314 ERCOT 155 28 183 7 190 Other Power Regions 1,007 72 1,079 (7 ) 1,072 Total Competitive Businesses Electric Revenues 3,705 47 3,752 — 3,752 Competitive Businesses Natural Gas Revenues 503 169 672 — 672 Competitive Businesses Other Revenues (c) 99 210 309 — 309 Total Generation Consolidated Operating Revenues $ 4,307 $ 426 $ 4,733 $ — $ 4,733 Three Months Ended March 31, 2019 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,286 $ (24 ) $ 1,262 $ (6 ) $ 1,256 Midwest 1,055 59 1,114 (6 ) 1,108 New York 409 (16 ) 393 — 393 ERCOT 130 79 209 3 212 Other Power Regions 1,165 194 1,359 (6 ) 1,353 Total Competitive Businesses Electric Revenues 4,045 292 4,337 (15 ) 4,322 Competitive Businesses Natural Gas Revenues 584 295 879 15 894 Competitive Businesses Other Revenues (c) 120 (40 ) 80 — 80 Total Generation Consolidated Operating Revenues $ 4,749 $ 547 $ 5,296 $ — $ 5,296 __________ (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 $179 million and losses of $52 million in 2020 and 2019 , respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Three Months Ended March 31, 2020 Three Months Ended March 31, 2019 RNF from external customers (a) Intersegment RNF Total RNF RNF from external customers (a) Intersegment RNF Total RNF Mid-Atlantic $ 559 $ 8 $ 567 $ 679 $ 4 $ 683 Midwest 732 (5 ) 727 769 2 771 New York 189 4 193 262 3 265 ERCOT 76 4 80 98 (24 ) 74 Other Power Regions 177 (19 ) 158 174 (18 ) 156 Total Revenues net of purchased power and fuel expense for Reportable Segments 1,733 (8 ) 1,725 1,982 (33 ) 1,949 Other (b) 296 8 304 109 33 142 Total Generation Revenues net of purchased power and fuel expense $ 2,029 $ — $ 2,029 $ 2,091 $ — $ 2,091 __________ (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 $132 million and losses of $28 million in 2020 and 2019 , respectively and the elimination of intersegment RNF. Electric and Gas Revenue by Customer Class (Utility Registrants): Three Months Ended March 31, 2020 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 701 $ 382 $ 339 $ 534 $ 236 $ 161 $ 137 Small commercial & industrial 362 99 67 115 35 43 37 Large commercial & industrial 134 53 103 253 188 23 42 Public authorities & electric railroads 13 7 7 15 9 3 3 Other (a) 211 58 79 169 60 54 55 Total rate-regulated electric revenues (b) $ 1,421 $ 599 $ 595 $ 1,086 $ 528 $ 284 $ 274 Rate-regulated natural gas revenues Residential $ — $ 150 $ 206 $ 40 $ — $ 40 $ — Small commercial & industrial — 51 34 17 — 17 — Large commercial & industrial — — 51 1 — 1 — Transportation — 6 — 4 — 4 — Other (c) — 1 9 2 — 2 — Total rate-regulated natural gas revenues (d) $ — $ 208 $ 300 $ 64 $ — $ 64 $ — Total rate-regulated revenues from contracts with customers $ 1,421 $ 807 $ 895 $ 1,150 $ 528 $ 348 $ 274 Other revenues Revenues from alternative revenue programs $ 12 $ 2 $ 36 $ 18 $ 15 $ 1 $ 1 Other rate-regulated electric revenues (e) 6 3 3 3 1 1 1 Other rate-regulated natural gas revenues (e) — 1 3 — — — — Total other revenues $ 18 $ 6 $ 42 $ 21 $ 16 $ 2 $ 2 Total rate-regulated revenues for reportable segments $ 1,439 $ 813 $ 937 $ 1,171 $ 544 $ 350 $ 276 Three Months Ended March 31, 2019 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 710 $ 409 $ 385 $ 579 $ 256 $ 185 $ 138 Small commercial & industrial 360 96 70 120 38 48 34 Large commercial & industrial 132 48 110 267 204 24 39 Public authorities & electric railroads 13 7 7 14 8 3 3 Other (a) 217 62 80 157 53 47 57 Total rate-regulated electric revenues (b) $ 1,432 $ 622 $ 652 $ 1,137 $ 559 $ 307 $ 271 Rate-regulated natural gas revenues Residential $ — $ 198 $ 219 $ 44 $ — $ 44 $ — Small commercial & industrial — 72 35 19 — 19 — Large commercial & industrial — 1 50 1 — 1 — Transportation — 7 — 4 — 4 — Other (c) — 2 4 3 — 3 — Total rate-regulated natural gas revenues (d) $ — $ 280 $ 308 $ 71 $ — $ 71 $ — Total rate-regulated revenues from contracts with customers $ 1,432 $ 902 $ 960 $ 1,208 $ 559 $ 378 $ 271 Other revenues Revenues from alternative revenue programs $ (28 ) $ (3 ) $ 10 $ 15 $ 14 $ — $ 1 Other rate-regulated electric revenues (e) 4 1 3 4 2 1 1 Other rate-regulated natural gas revenues (e) — — 3 1 — 1 — Total other revenues $ (24 ) $ (2 ) $ 16 $ 20 $ 16 $ 2 $ 2 Total rate-regulated revenues for reportable segments $ 1,408 $ 900 $ 976 $ 1,228 $ 575 $ 380 $ 273 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates of $5 million , $2 million , $6 million , $3 million , $1 million , $2 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, in 2020 and $4 million , $1 million , $2 million , $3 million , $2 million , $2 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, in 2019 . (c) Includes revenues from off-system natural gas sales. (d) Includes operating revenues from affiliates of less than $1 million and $3 million at PECO and BGE, respectively, in 2020 and less than $1 million and $4 million at PECO and BGE, respectively, in 2019 . (e) Includes late payment charge revenues.

Accounts Receivable (All Regist

Accounts Receivable (All Registrants)	3 Months Ended
	Mar. 31, 2020
Credit Loss [Abstract]
Loans, Notes, Trade and Other Receivables Disclosure [Text Block]	Accounts Receivable (All Registrants) Unbilled Customer Revenue The following table provides additional information about unbilled customer revenues recorded in the Registrants' Consolidated Balance Sheets. Unbilled customer revenues (a) Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE March 31, 2020 $ 1,225 $ 698 $ 160 $ 96 $ 134 $ 137 $ 75 $ 42 $ 20 December 31, 2019 1,535 807 218 146 170 194 100 61 33 _________ (a) Unbilled customer revenues are classified in customer accounts receivables, net in the Registrants' Consolidated Balance Sheets. Allowance for Credit Losses on Accounts Receivable The following table presents the rollforward of Allowance for Credit Losses on Customer Accounts Receivable. Three Months Ended March 31, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of December 31, 2019 $ 243 $ 80 $ 59 $ 55 $ 12 $ 37 $ 13 $ 11 $ 13 Plus: Current Period Provision for Expected Credit Losses 55 4 18 18 8 7 3 2 2 Less: Write-offs, net of recoveries (a) 20 3 6 7 2 2 1 — 1 Balance as of March 31, 2020 $ 278 $ 81 $ 71 $ 66 $ 18 $ 42 $ 15 $ 13 $ 14 _________ (a) Recoveries were not material to the Registrants. The following table presents the rollforward of Allowance for Credit Losses on Other Accounts Receivable. Three Months Ended March 31, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of December 31, 2019 $ 48 $ — $ 20 $ 7 $ 5 $ 16 $ 7 $ 4 $ 5 Plus: Current Period Provision for Expected Credit Losses 8 — 3 1 2 2 1 — 1 Less: Write-offs, net of recoveries (a) 4 — 1 1 2 — — — — Balance as of March 31, 2020 $ 52 $ — $ 22 $ 7 $ 5 $ 18 $ 8 $ 4 $ 6 _________ (a) Recoveries were not material to the Registrants. Purchases and Sales of Customer and Other Accounts Receivables Generation is required, under supplier tariffs in ISO-NE, MISO, NYISO and PJM, to sell customer and other receivables to utility companies, which include the Utility Registrants. The Utility Registrants are required, under separate legislation and regulations in Illinois, Pennsylvania, Maryland, District of Columbia and New Jersey, to purchase certain receivables from alternative retail electric and, as applicable, natural gas suppliers that participate in the utilities' consolidated billing. The following tables present the total receivables purchased and sold. Three Months Ended March 31, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Total Receivables Purchased $ 781 $ — $ 280 $ 284 $ 195 $ 264 $ 165 $ 53 $ 46 Total Receivables Sold 507 749 — — — — — — — Related Party Transactions: Receivables purchased from Generation — — 34 67 69 72 51 13 8 Receivables sold to the Utility Registrants — 242 — — — — — — —

Early Plant Retirements (Exelon

Early Plant Retirements (Exelon and Generation)	3 Months Ended
	Mar. 31, 2020
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. In addition, FERC’s December 19, 2019 order on the MOPR in PJM may undermine the continued effectiveness of the Illinois ZES and the New Jersey ZEC program unless Illinois and New Jersey implement an FRR mechanism under which the Generation plants in these states would be removed from PJM’s capacity auction. See Note 2 — Regulatory Matters for additional information on the New Jersey ZEC program, New York CES and FERC's December 19, 2019 order and Note 3 — Regulatory Matters of the 2019 Form 10-K for additional information on the Illinois ZES. 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. As a result of the early nuclear plant retirement decision at TMI, 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. The total impact for the three months ended March 31, 2019 are summarized in the table below. Income statement expense (pre-tax) Three Months Ended March 31, 2019 Depreciation and amortization Accelerated depreciation $ 74 Accelerated nuclear fuel amortization 5 Operating and maintenance (a) (83 ) Total $ (4 ) _________ (a) Primarily reflects the net impacts associated with the remeasurement of the TMI ARO. See Note 9 — Asset Retirement Obligations of the 2019 Form 10-K 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. The following table provides the balance sheet amounts as of March 31, 2020 for Exelon's and Generation's significant assets and liabilities associated with these three nuclear plants. Depreciation provisions are based on the estimated useful lives of these nuclear generating stations, which reflect the first renewal of the operating licenses. Dresden Byron Braidwood Total Asset Balances Materials and supplies inventory, net $ 68 $ 68 $ 81 $ 217 Nuclear fuel inventory, net 204 172 203 579 Completed plant, net 1,084 1,343 1,390 3,817 Construction work in progress 16 22 32 70 Liability Balances Asset retirement obligation (1,301 ) (596 ) (554 ) (2,451 ) NRC License First Renewal Term 2029 (Unit 2) 2044 (Unit 1) 2046 (Unit 1) 2031 (Unit 3) 2046 (Unit 2) 2047 (Unit 2) Other Generation On March 29, 2018, Generation notified grid operator ISO-NE of its plans to early retire its Mystic Units 8 and 9 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. On January 22, 2019, Exelon and several other parties filed requests for rehearing of certain findings in the order. On March 25, 2019, ISO-NE filed the Inventoried Energy Program (IEP), 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. The IEP went into effect by operation of law on August 5, 2019 because FERC did not have a quorum at that time. On October 7, 2019, requests for rehearing were denied and several parties appealed to the D.C. Circuit Court. On April 14, 2020, FERC filed an unopposed motion asking the court for a voluntary remand of the IEP order, noting that FERC now has a quorum of Commissioners who can participate in the consideration of ISO-NE’s IEP filing. On April 15, 2020, ISO-NE filed its long-term, market-based fuel security proposal, proposing three new, day-ahead ancillary services products intended to compensate generators for operational capabilities that provide fuel security to the region. In the filing, ISO-NE also proposed to sunset the Fuel Security Retention Mechanism, through which Mystic has been retained for fuel security, and the IEP by June 1, 2024. In addition, the filing includes an alternate proposal sponsored by New England Power Pool, which includes substantive amendments to the ISO-NE proposal. ISO-NE requested a 30-day comment period and a November 1, 2020 effective date. The following table provides the balance sheet amounts as of March 31, 2020 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. March 31, 2020 Asset Balances Materials and supplies inventory $ 32 Fuel inventory 12 Property, plant and equipment, net 902 Liability Balances Asset retirement obligation (3 ) See Note 8 — Asset Impairments for impairment assessment considerations on the New England Asset Group.

Nuclear Decommissioning (Exelon

Nuclear Decommissioning (Exelon and Generation)	3 Months Ended
	Mar. 31, 2020
Environmental Remediation Obligations [Abstract]
Nuclear Decommissioning (Exelon and Generation)	Nuclear Decommissioning (Exelon and Generation) Nuclear Decommissioning Asset Retirement Obligations Generation has a legal obligation to decommission its nuclear power plants following the expiration of their operating licenses. To estimate its decommissioning obligation related to its nuclear generating stations for financial accounting and reporting purposes, Generation uses a probability-weighted, discounted cash flow model which, on a unit-by-unit basis, considers multiple outcome scenarios that include significant estimates and assumptions, and are based on decommissioning cost studies, cost escalation rates, probabilistic cash flow models and discount rates. Generation 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, 2019 to March 31, 2020 : Nuclear decommissioning ARO at December 31, 2019 (a) $ 10,504 Accretion expense 121 Costs incurred related to decommissioning plants (20 ) Nuclear decommissioning ARO at March 31, 2020 (a) $ 10,605 _________ (a) Includes $107 million and $112 million as the current portion of the ARO at March 31, 2020 and December 31, 2019 , respectively, which is included in Other current liabilities in Exelon’s and Generation’s Consolidated Balance Sheets. NDT Funds Exelon and Generation had NDT funds totaling $11,824 million and $13,353 million at March 31, 2020 and December 31, 2019 , respectively. The NDT funds also include $213 million and $163 million for the current portion of the NDT funds at March 31, 2020 and December 31, 2019 , 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 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, including its shutdown 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. On March 31, 2020, Generation filed its annual decommissioning funding status report with the NRC for Generation’s shutdown units (excluding Zion Station for the reason noted above). The annual status report demonstrated adequate decommissioning funding assurance as of December 31, 2019, for all of its shutdown reactors except for Peach Bottom Unit 1. 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 9 — Asset Retirement Obligations of the Exelon 2019 Form 10-K for information regarding the amount collected from PECO ratepayers for decommissioning cost.

Asset Impairments (Exelon and G

Asset Impairments (Exelon and Generation)	3 Months Ended
	Mar. 31, 2020
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. 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 March 31, 2020 , Generation had approximately $717 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 $1,865 million of additional net long-lived assets as of March 31, 2020 . 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 12 - Debt and Credit Agreements for additional information on the PG&E bankruptcy. New England Asset Group During the first quarter of 2018, Mystic Unit 9 did not clear in the ISO-NE capacity auction for the 2021 - 2022 planning year. On March 29, 2018, Generation notified ISO-NE of the early retirement of its Mystic Generating Station's Units 7, 8, 9 and the Mystic Jet Unit (Mystic Generating Station assets) absent regulatory reforms. These events suggested that the carrying value of its New England asset group may be impaired. In the second quarter of 2018, Generation completed a comprehensive review of the estimated undiscounted future cash flows of the New England asset group and no impairment charge was required. Generation continues to monitor developments in the region that would indicate a potential triggering event for impairment and continues to look for solutions that appropriately compensate both Mystic 8 and 9 and the Everett Marine Terminal for their contributions to the region. Further developments such as the failure of ISO-NE to adopt long-term solutions for reliability and fuel security could potentially result in material future impairments of the New England asset group. See Note 6 - Early Plant Retirements for additional information.

Income Taxes (All Registrants)

Income Taxes (All Registrants)	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 Exelon (a) Generation (a) 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 34.0 0.7 8.3 0.1 5.7 5.8 4.7 6.6 6.7 Qualified NDT fund income (235.8) 36.4 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (4.5) 0.5 (0.2) — (0.1) (0.1) — (0.2) (0.2) Plant basis differences (23.0) — (1.1) (8.4) (1.2) (1.4) (2.1) (0.7) (0.8) Production tax credits and other credits (9.9) 1.3 (0.2) — (0.2) — — — — Noncontrolling interests 10.6 (1.6) — — — — — — — Excess deferred tax amortization (71.7) — (10.5) (3.0) (7.3) (15.5) (14.2) (12.7) (18.8) Tax Settlements (79.1) 12.2 — — — — — — — Other 12.5 0.6 0.3 — 0.6 (0.6) (0.6) (0.5) (0.8) Effective income tax rate (345.9)% 71.1% 17.6% 9.7% 18.5% 9.2% 8.8% 13.5% 7.1% _________ (a) Generation recognized a loss before income taxes for the quarter ended March 31, 2020 . As a result, positive percentages represent an income tax benefit for the period presented. At the consolidated level, positive percentages represent income tax expense. Three Months Ended March 31, 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 3.9 3.1 8.2 1.0 6.3 4.7 2.1 6.5 6.7 Qualified NDT fund income 7.2 14.2 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.5) (0.9) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (1.4) — (0.5) (6.7) (0.9) (1.7) (2.0) (0.7) (2.3) Production tax credits and other credits (0.8) (1.5) — — — — — — — Noncontrolling interests (0.6) (1.1) — — — — — — — Excess deferred tax amortization (4.7) — (8.5) (2.5) (7.9) (19.4) (17.9) (15.6) (23.9) Other 0.1 (0.5) 0.3 0.2 — (0.3) 0.4 0.7 (1.2) Effective income tax rate 24.2% 34.3% 20.3% 13.0% 18.4% 4.1% 3.5% 11.7% —% Accounting for Uncertainty in Income Taxes Exelon, Generation, PHI and ACE have the following unrecognized tax benefits as of March 31, 2020 and December 31, 2019 . ComEd, PECO, BGE, Pepco and DPL's amounts are not material. Exelon Generation PHI ACE March 31, 2020 $ 98 $ 32 $ 49 $ 14 December 31, 2019 507 441 48 14 Exelon's and Generation's unrecognized federal and state tax benefits decreased in the first quarter of 2020 by approximately $411 million due to the settlement of a federal refund claim with IRS Appeals. The recognition of these tax benefits resulted in an increase to Exelon's and Generation’s net income of $76 million and $73 million, respectively, for the quarter ended March 31, 2020 , reflecting a decrease to Exelon's and Generation's income tax expense of $67 million. 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 The following table represents Exelon's, PHI's and ACE's 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 March 31, 2020 . Generation's, ComEd's, PECO's, BGE's, Pepco's and DPL's amounts are not material. Exelon PHI ACE (a) $ 14 $ 14 $ 14 _________ (a) The unrecognized tax benefit related to 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 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.

Retirement Benefits (All Regist

Retirement Benefits (All Registrants)	3 Months Ended
	Mar. 31, 2020
Retirement Benefits [Abstract]
Retirement Benefits (All Registrants)	Retirement Benefits (All Registrants) Defined Benefit Pension and OPEB During the first quarter of 2020, Exelon received an updated valuation of its pension and OPEB to reflect actual census data as of January 1, 2020. This valuation resulted in an increase to the pension and OPEB obligations of $8 million and $31 million , respectively. Additionally, accumulated other comprehensive income increased by $7 million (after-tax) and regulatory assets and liabilities increased by $19 million and decreased by $10 million , respectively. The majority of the 2020 pension benefit cost for Exelon-sponsored plans is calculated using an expected long-term rate of return on plan assets of 7.00% and a discount rate of 3.34% . The majority of the 2020 OPEB cost is calculated using an expected long-term rate of return on plan assets of 6.69% for funded plans and a discount rate of 3.31% . 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 months ended March 31, 2020 and 2019 . Pension Benefits OPEB 2020 2019 2020 2019 Components of net periodic benefit cost: Service cost $ 97 $ 89 $ 23 $ 24 Interest cost 189 221 38 47 Expected return on assets (318 ) (307 ) (41 ) (38 ) Amortization of: Prior service cost (benefit) 1 — (31 ) (45 ) Actuarial loss 128 104 12 11 Net periodic benefit cost $ 97 $ 107 $ 1 $ (1 ) 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 March 31, Pension and OPEB Costs 2020 2019 Exelon $ 98 $ 106 Generation 27 31 ComEd 28 24 PECO 1 2 BGE 16 16 PHI 17 23 Pepco 3 6 DPL 1 4 ACE 3 4 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 months ended March 31, 2020 and 2019 , respectively. Three Months Ended March 31, Savings Plan Matching Contributions 2020 2019 Exelon $ 33 $ 31 Generation 13 13 ComEd 7 7 PECO 3 2 BGE 2 2 PHI 3 4 Pepco 1 1 DPL 1 1 ACE — 1

Derivative Financial Instrument

Derivative Financial Instruments (All Registrants)	3 Months Ended
	Mar. 31, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial 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 are 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 2 - 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 March 31, 2020 and December 31, 2019 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 March 31, 2020 and December 31, 2019 : March 31, 2020 Exelon Generation ComEd Derivatives Total Economic Hedges Proprietary Trading Collateral (a)(b) Netting (a) Subtotal Economic Hedges Mark-to-market derivative assets (current assets) $ 649 $ 4,010 $ 63 $ 277 $ (3,701 ) $ 649 $ — Mark-to-market derivative assets (noncurrent assets) 625 1,878 23 112 (1,388 ) 625 — Total mark-to-market derivative assets 1,274 5,888 86 389 (5,089 ) 1,274 — Mark-to-market derivative liabilities (current liabilities) (252 ) (4,219 ) (37 ) 339 3,701 (216 ) (36 ) Mark-to-market derivative liabilities (noncurrent liabilities) (416 ) (1,676 ) (11 ) 161 1,388 (138 ) (278 ) Total mark-to-market derivative liabilities (668 ) (5,895 ) (48 ) 500 5,089 (354 ) (314 ) Total mark-to-market derivative net assets (liabilities) $ 606 $ (7 ) $ 38 $ 889 $ — $ 920 $ (314 ) December 31, 2019 Exelon Generation ComEd Description Total Economic Proprietary Collateral Netting (a) Subtotal Economic Mark-to-market derivative assets $ 675 $ 3,506 $ 72 $ 287 $ (3,190 ) $ 675 $ — Mark-to-market derivative assets 508 1,238 25 122 (877 ) 508 — Total mark-to-market derivative assets 1,183 4,744 97 409 (4,067 ) 1,183 — Mark-to-market derivative liabilities (236 ) (3,713 ) (38 ) 357 3,190 (204 ) (32 ) Mark-to-market derivative liabilities (380 ) (1,140 ) (11 ) 163 877 (111 ) (269 ) Total mark-to-market derivative liabilities (616 ) (4,853 ) (49 ) 520 4,067 (315 ) (301 ) Total mark-to-market derivative net assets (liabilities) $ 567 $ (109 ) $ 48 $ 929 $ — $ 868 $ (301 ) _________ (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), $644 million and $511 million represents variation margin on the exchanges at March 31, 2020 and December 31, 2019 respectively. Economic Hedges (Commodity Price Risk) Generation. For the three months ended March 31, 2020 and 2019 , 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 2020 2019 Income Statement Location Gain (Loss) Operating revenues $ 175 $ (50 ) Purchased power and fuel (47 ) 30 Total Exelon and Generation $ 128 $ (20 ) 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 March 31, 2020 , the percentage of expected generation hedged for the Mid-Atlantic, Midwest, New York and ERCOT reportable segments is 89% - 92% and 70% - 73% for 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 months ended March 31, 2020 and 2019 , 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 $1,268 million and $1,269 million at March 31, 2020 and December 31, 2019 , respectively, for Exelon and $568 million and $569 million at March 31, 2020 and December 31, 2019 , 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 $144 million and $231 million at March 31, 2020 and December 31, 2019 , respectively. The mark-to-market derivative assets and liabilities as of March 31, 2020 and December 31, 2019 and the mark-to-market gains and losses for the three months ended March 31, 2020 and 2019 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 payables and receivables, net of collateral and instruments that are subject to master netting agreements, as of March 31, 2020 . 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. Rating as of March 31, 2020 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 $ 915 $ 22 $ 893 — $ — Non-investment grade 60 49 11 No external ratings Internally rated — investment grade 228 1 227 Internally rated — non-investment grade 157 22 135 Total $ 1,360 $ 94 $ 1,266 — $ — Net Credit Exposure by Type of Counterparty As of Financial institutions $ 18 Investor-owned utilities, marketers, power producers 983 Energy cooperatives and municipalities 224 Other 41 Total $ 1,266 _________ (a) As of March 31, 2020 , credit collateral held from counterparties where Generation had credit exposure included $29 million of cash and $65 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 March 31, 2020 , 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 March 31, 2020 December 31, 2019 Gross fair value of derivative contracts containing this feature (a) $ (1,002 ) $ (956 ) Offsetting fair value of in-the-money contracts under master netting arrangements (b) 699 649 Net fair value of derivative contracts containing this feature (c) $ (303 ) $ (307 ) _________ (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 March 31, 2020 and December 31, 2019 , 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. March 31, 2020 December 31, 2019 Cash collateral posted $ 977 $ 982 Letters of credit posted 256 264 Cash collateral held 105 103 Letters of credit held 115 112 Additional collateral required in the event of a credit downgrade below investment grade 1,468 1,509 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 March 31, 2020 , 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 March 31, 2020 , they could have been required to post incremental collateral to its counterparties of $33 million , $34 million and $12 million

Debt and Credit Agreements (All

Debt and Credit Agreements (All Registrants)	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Debt and Credit Agreements (All Registrants)	Debt and Credit Agreements (All Registrants) Short-Term Borrowings Exelon Corporate, ComEd and BGE meet their short-term liquidity requirements primarily through the issuance of commercial paper. Generation and PECO meet their short-term liquidity requirements primarily through the issuance of commercial paper and borrowings from the Exelon intercompany money pool. Pepco, DPL, and ACE meet their short-term liquidity requirements primarily through the issuance of commercial paper and borrowings from the PHI 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 March 31, 2020 and December 31, 2019 . PECO had no commercial paper borrowings as of both March 31, 2020 and December 31, 2019 . Outstanding Commercial Average Interest Rate on Commercial Paper Issuer March 31, 2020 December 31, 2019 March 31, 2020 December 31, 2019 Exelon (a) $ 979 $ 870 2.91 % 2.25 % Generation 595 320 2.01 % 1.84 % ComEd — 130 — % 2.38 % BGE 141 76 4.45 % 2.46 % PHI (b) 108 208 4.25 % N/A PEPCO — 82 — % 2.56 % DPL 54 56 4.17 % 2.02 % ACE 54 70 4.32 % 2.43 % __________ (a) Includes outstanding commercial paper at Exelon Corporate of $135 million and $136 million with average interest rates on commercial paper borrowings of 4.20% and 1.92% at March 31, 2020 and December 31, 2019, respectively. (b) Includes the consolidated amounts of Pepco, DPL, and ACE. On March 19, 2020, Generation borrowed $1.5 billion on its revolving credit facility due to disruptions in the commercial paper markets as a result of COVID-19, which is recorded in Long-term debt on Exelon’s and Generation’s Consolidated Balance Sheet. The funds were used to refinance commercial paper. Generation repaid the $1.5 billion borrowed on the revolving credit facility on April 3, 2020. As of March 31, 2020, the available capacity on Generation’s revolving credit facility was $2.4 billion . See Note 16 — Debt and Credit Agreements of the Exelon 2019 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 . The loan agreement was renewed on March 19, 2020 and will expire on March 18, 2021. Pursuant to the loan agreement, loans made thereunder bear interest at a variable rate equal to LIBOR plus 0.65% and all indebtedness thereunder is unsecured. The loan agreement is reflected in Exelon's Consolidated Balance Sheet within Short-Term borrowings. On March 19, 2020, Generation entered into a term loan agreement for $200 million . The loan agreement has an expiration of March 18, 2021. Pursuant to the loan agreement, loans made thereunder bear interest at a variable rate equal to LIBOR plus 0.50% and all indebtedness thereunder is unsecured. The loan agreement is reflected in Generation's Consolidated Balance Sheet within Short-term borrowings. On March 31, 2020, Generation entered into a term loan agreement for $300 million . The loan agreement has an expiration of March 30, 2021. Pursuant to the loan agreement, loans made thereunder bear interest at a variable rate equal to LIBOR plus 0.75% and all indebtedness thereunder is unsecured. The loan agreement is reflected in Generation's Consolidated Balance Sheet within Short-term borrowings. Credit Agreements On April 24, 2020, Exelon Corporate entered into a credit agreement establishing a $550 million 364-day revolving credit facility at a variable interest rate of LIBOR plus 1.75% . This facility will be used by Exelon as an additional source of short-term liquidity over the next 12 months. Long-Term Debt Issuance of Long-Term Debt During the three months ended March 31, 2020 , the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Generation Energy Efficiency Project Financing (a) 3.95 % August 31, 2020 $ 2 Funding to install energy conservation measures for the Fort Meade project. Generation Energy Efficiency Project Financing (a) 2.53 % April 30, 2021 1 Funding to install energy conservation measures for the Fort AP Hill project. ComEd First Mortgage Bonds, Series 129 3.00 % March 1, 2050 650 Repay a portion of outstanding commercial paper obligations and to fund general corporate purposes. ComEd First Mortgage Bonds, Series 128 2.20 % March 1, 2030 350 Repay a portion of outstanding commercial paper obligations and fund other general corporate purposes. Pepco (b) First Mortgage Bonds 2.53 % February 25, 2030 150 Repay existing indebtedness and for general corporate purposes. __________ (a) For Energy Efficiency Project Financing, the maturity dates represent the expected date of project completion, upon which the respective customer assumes the outstanding debt. (b) On February 25, 2020, Pepco entered into a purchase agreement of First Mortgage Bonds for $150 million at 3.28% due on September 23, 2050. The closing date of the issuance is expected to occur in September 2020. On April 1, 2020, Exelon Corporate issued notes for $1.25 billion at 4.05% , which are due in 2030 and notes for $750 million at 4.70% , which are due in 2050. A portion of the net proceeds from the sale of these notes, together with available cash balances, will be used to repay $900 million of Exelon Corporate notes maturing in June of 2020. The remainder of the net proceeds will be used for general corporate purposes. Debt Covenants As of March 31, 2020 , the Registrants are in compliance with debt covenants, except for Antelope Valley's ongoing 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 March 31, 2020 , approximately $479 million was outstanding. In addition, Generation has issued letters of credit to support its equity investment in the project. As of March 31, 2020 , Generation had $37 million in letters of credit outstanding related to the project. 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 March 31, 2020 . 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 March 31, 2020 , $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 16 — Debt and Credit Agreements of the Exelon 2019 Form 10-K for additional information on nonrecourse debt.

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities (All Registrants)	3 Months Ended
	Mar. 31, 2020
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. 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 March 31, 2020 and December 31, 2019 . 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. March 31, 2020 December 31, 2019 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 $ 37,656 $ 36,908 $ 2,556 $ 39,464 $ 36,039 $ 37,453 $ 2,580 $ 40,033 Generation 8,449 7,034 1,330 8,364 7,974 7,304 1,366 8,670 ComEd 9,478 10,483 — 10,483 8,491 9,848 — 9,848 PECO 3,406 3,762 50 3,812 3,405 3,868 50 3,918 BGE 3,271 3,572 — 3,572 3,270 3,649 — 3,649 PHI 6,708 5,602 1,176 6,778 6,563 5,902 1,164 7,066 Pepco 3,015 3,009 483 3,492 2,864 3,198 388 3,586 DPL 1,575 1,334 271 1,605 1,567 1,408 311 1,719 ACE 1,325 991 421 1,412 1,327 1,026 464 1,490 Long-Term Debt to Financing Trusts (a) Exelon $ 390 $ — $ 387 $ 387 $ 390 $ — $ 428 $ 428 ComEd 205 — 204 204 205 — 227 227 PECO 184 — 183 183 184 — 201 201 SNF Obligation Exelon $ 1,204 $ 723 $ — $ 723 $ 1,199 $ 1,055 $ — $ 1,055 Generation 1,204 723 — 723 1,199 1,055 — 1,055 ____ (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 March 31, 2020 and December 31, 2019 : Exelon and Generation Exelon Generation As of March 31, 2020 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) $ 1,399 $ — $ — $ — $ 1,399 $ 591 $ — $ — $ — $ 591 NDT fund investments Cash equivalents (b) 373 79 — — 452 373 79 — — 452 Equities 2,603 1,377 — 1,080 5,060 2,603 1,377 — 1,080 5,060 Fixed income Corporate debt — 1,412 258 — 1,670 — 1,412 258 — 1,670 U.S. Treasury and agencies 1,723 141 — — 1,864 1,723 141 — — 1,864 Foreign governments — 37 — — 37 — 37 — — 37 State and municipal debt — 87 — — 87 — 87 — — 87 Other (c) — 26 — 872 898 — 26 — 872 898 Fixed income subtotal 1,723 1,703 258 872 4,556 1,723 1,703 258 872 4,556 Private credit — — 240 546 786 — — 240 546 786 Private equity — — — 444 444 — — — 444 444 Real estate — — — 636 636 — — — 636 636 NDT fund investments subtotal (d) 4,699 3,159 498 3,578 11,934 4,699 3,159 498 3,578 11,934 Rabbi trust investments Cash equivalents 51 — — — 51 4 — — — 4 Mutual funds 75 — — — 75 23 — — — 23 Fixed income — 11 — — 11 — — — — — Life insurance contracts — 72 42 — 114 — 22 — — 22 Rabbi trust investments subtotal 126 83 42 — 251 27 22 — — 49 Commodity derivative assets Economic hedges 714 3,135 2,039 — 5,888 714 3,135 2,039 — 5,888 Proprietary trading — 29 57 — 86 — 29 57 — 86 Effect of netting and allocation of collateral (e)(f) (868 ) (2,770 ) (1,062 ) — (4,700 ) (868 ) (2,770 ) (1,062 ) — (4,700 ) Commodity derivative assets subtotal (154 ) 394 1,034 — 1,274 (154 ) 394 1,034 — 1,274 Total assets 6,070 3,636 1,574 3,578 14,858 5,163 3,575 1,532 3,578 13,848 Exelon Generation As of March 31, 2020 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 (990 ) (3,476 ) (1,743 ) — (6,209 ) (990 ) (3,476 ) (1,429 ) — (5,895 ) Proprietary trading — (28 ) (20 ) — (48 ) — (28 ) (20 ) — (48 ) Effect of netting and allocation of collateral (e)(f) 994 3,318 1,277 — 5,589 994 3,318 1,277 — 5,589 Commodity derivative liabilities subtotal 4 (186 ) (486 ) — (668 ) 4 (186 ) (172 ) — (354 ) Deferred compensation obligation — (126 ) — — (126 ) — (34 ) — — (34 ) Total liabilities 4 (312 ) (486 ) — (794 ) 4 (220 ) (172 ) — (388 ) Total net assets $ 6,074 $ 3,324 $ 1,088 $ 3,578 $ 14,064 $ 5,167 $ 3,355 $ 1,360 $ 3,578 $ 13,460 Exelon Generation As of December 31, 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) $ 639 $ — $ — $ — $ 639 $ 214 $ — $ — $ — $ 214 NDT fund investments Cash equivalents (b) 365 87 — — 452 365 87 — — 452 Equities 3,353 1,753 — 1,388 6,494 3,353 1,753 — 1,388 6,494 Fixed income Corporate debt — 1,469 257 — 1,726 — 1,469 257 — 1,726 U.S. Treasury and agencies 1,808 131 — — 1,939 1,808 131 — — 1,939 Foreign governments — 42 — — 42 — 42 — — 42 State and municipal debt — 90 — — 90 — 90 — — 90 Other (c) — 33 — 953 986 — 33 — 953 986 Fixed income subtotal 1,808 1,765 257 953 4,783 1,808 1,765 257 953 4,783 Private credit — — 254 508 762 — — 254 508 762 Private equity — — — 402 402 — — — 402 402 Real estate — — — 607 607 — — — 607 607 NDT fund investments subtotal (d) 5,526 3,605 511 3,858 13,500 5,526 3,605 511 3,858 13,500 Rabbi trust investments Cash equivalents 50 — — — 50 4 — — — 4 Mutual funds 81 — — — 81 25 — — — 25 Fixed income — 12 — — 12 — — — — — Life insurance contracts — 78 41 — 119 — 25 — — 25 Rabbi trust investments subtotal 131 90 41 — 262 29 25 — — 54 Commodity derivative assets Economic hedges 768 2,491 1,485 — 4,744 768 2,491 1,485 — 4,744 Proprietary trading — 37 60 — 97 — 37 60 — 97 Effect of netting and allocation of collateral (e)(f) (908 ) (2,162 ) (588 ) — (3,658 ) (908 ) (2,162 ) (588 ) — (3,658 ) Commodity derivative assets subtotal (140 ) 366 957 — 1,183 (140 ) 366 957 — 1,183 Total assets 6,156 4,061 1,509 3,858 15,584 5,629 3,996 1,468 3,858 14,951 Exelon Generation As of December 31, 2019 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 (1,071 ) (2,855 ) (1,228 ) — (5,154 ) (1,071 ) (2,855 ) (927 ) — (4,853 ) Proprietary trading — (34 ) (15 ) — (49 ) — (34 ) (15 ) — (49 ) Effect of netting and allocation of collateral (e)(f) 1,071 2,714 802 — 4,587 1,071 2,714 802 — 4,587 Commodity derivative liabilities subtotal — (175 ) (441 ) — (616 ) — (175 ) (140 ) — (315 ) Deferred compensation obligation — (147 ) — — (147 ) — (41 ) — — (41 ) Total liabilities — (322 ) (441 ) — (763 ) — (216 ) (140 ) — (356 ) Total net assets $ 6,156 $ 3,739 $ 1,068 $ 3,858 $ 14,821 $ 5,629 $ 3,780 $ 1,328 $ 3,858 $ 14,595 _________ (a) Exelon excludes cash of $483 million and $373 million at March 31, 2020 and December 31, 2019 , respectively, and restricted cash of $110 million at both March 31, 2020 and December 31, 2019 , and includes long-term restricted cash of $121 million and $177 million at March 31, 2020 and December 31, 2019 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Generation excludes cash of $317 million and $177 million at March 31, 2020 and December 31, 2019 , respectively, and restricted cash of $63 million and $58 million at March 31, 2020 and December 31, 2019 , respectively. (b) Includes $78 million and $90 million of cash received from outstanding repurchase agreements at March 31, 2020 and December 31, 2019 , 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 $2 million , which have total notional amounts of $826 million and $724 million at March 31, 2020 and December 31, 2019 , 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 $110 million and $147 million at March 31, 2020 and December 31, 2019 , 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 $126 million , $548 million and $215 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of March 31, 2020 . Collateral posted/(received) from counterparties, net of collateral paid to counterparties, totaled $163 million , $551 million and $214 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2019 . (f) Of the collateral posted/(received), $644 million and $511 million represents variation margin on the exchanges as of March 31, 2020 and December 31, 2019 , respectively. As of March 31, 2020 , Exelon and Generation have outstanding commitments to invest in fixed income, private credit, private equity and real estate investments of approximately $80 million , $131 million , $338 million , and $428 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 $76 million and $66 million as of March 31, 2020 , respectively. Changes in fair value, cumulative adjustments and impairments were not material for the three months ended March 31, 2020 . ComEd, PECO and BGE ComEd PECO BGE As of March 31, 2020 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) $ 729 $ — $ — $ 729 $ 8 $ — $ — $ 8 $ — $ — $ — $ — Rabbi trust investments Mutual funds — — — — 7 — — 7 8 — — 8 Life insurance contracts — — — — — 10 — 10 — — 1 1 Rabbi trust investments subtotal — — — — 7 10 — 17 8 — 1 9 Total assets 729 — — 729 15 10 — 25 8 — 1 9 Liabilities Deferred compensation obligation — (7 ) — (7 ) — (8 ) — (8 ) — (5 ) — (5 ) Mark-to-market derivative liabilities (b) — — (314 ) (314 ) — — — — — — — — Total liabilities — (7 ) (314 ) (321 ) — (8 ) — (8 ) — (5 ) — (5 ) Total net assets (liabilities) $ 729 $ (7 ) $ (314 ) $ 408 $ 15 $ 2 $ — $ 17 $ 8 $ (5 ) $ 1 $ 4 ComEd PECO BGE As of December 31, 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) $ 280 $ — $ — $ 280 $ 15 $ — $ — $ 15 $ — $ — $ — $ — Rabbi trust investments Mutual funds — — — — 8 — — 8 8 — — 8 Life insurance contracts — — — — — 11 — 11 — — — — Rabbi trust investments subtotal — — — — 8 11 — 19 8 — — 8 Total assets 280 — — 280 23 11 — 34 8 — — 8 Liabilities Deferred compensation obligation — (8 ) — (8 ) — (9 ) — (9 ) — (5 ) — (5 ) Mark-to-market derivative liabilities (b) — — (301 ) (301 ) — — — — — — — — Total liabilities — (8 ) (301 ) (309 ) — (9 ) — (9 ) — (5 ) — (5 ) Total net assets (liabilities) $ 280 $ (8 ) $ (301 ) $ (29 ) $ 23 $ 2 $ — $ 25 $ 8 $ (5 ) $ — $ 3 _________ (a) ComEd excludes cash of $67 million and $90 million at March 31, 2020 and December 31, 2019 , respectively, and restricted cash of $38 million and $33 million at March 31, 2020 and December 31, 2019 , respectively, and includes long-term restricted cash of $108 million and $163 million at March 31, 2020 and December 31, 2019 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. PECO excludes cash of $30 million and $12 million at March 31, 2020 and December 31, 2019 , respectively. BGE excludes cash of $11 million and $24 million at March 31, 2020 and December 31, 2019 , respectively, and restricted cash of $1 million at both March 31, 2020 and December 31, 2019 . (b) The Level 3 balance consists of the current and noncurrent liability of $36 million and $278 million , respectively, at March 31, 2020 , and $32 million and $269 million , respectively, at December 31, 2019 , related to floating-to-fixed energy swap contracts with unaffiliated suppliers. PHI, Pepco, DPL and ACE As of March 31, 2020 As of December 31, 2019 PHI Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 63 $ — $ — $ 63 $ 124 $ — $ — $ 124 Rabbi trust investments Cash equivalents 44 — — 44 44 — — 44 Mutual funds 13 — — 13 14 — — 14 Fixed income — 11 — 11 — 12 — 12 Life insurance contracts — 25 42 67 — 24 41 65 Rabbi trust investments subtotal 57 36 42 135 58 36 41 135 Total assets 120 36 42 198 182 36 41 259 Liabilities Deferred compensation obligation — (16 ) — (16 ) — (19 ) — (19 ) Total liabilities — (16 ) — (16 ) — (19 ) — (19 ) Total net assets $ 120 $ 20 $ 42 $ 182 $ 182 $ 17 $ 41 $ 240 Pepco DPL ACE As of March 31, 2020 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 $ — $ — $ — $ — $ 15 $ — $ — $ 15 Rabbi trust investments Cash equivalents 44 — — 44 — — — — — — — — Fixed income — 1 — 1 — — — — — — — — Life insurance contracts — 25 42 67 — — — — — — — — Rabbi trust investments subtotal 44 26 42 112 — — — — — — — — Total assets 78 26 42 146 — — — — 15 — — 15 Liabilities Deferred compensation obligation — (2 ) — (2 ) — — — — — — — — Total liabilities — (2 ) — (2 ) — — — — — — — — Total net assets $ 78 $ 24 $ 42 $ 144 $ — $ — $ — $ — $ 15 $ — $ — $ 15 Pepco DPL ACE As of December 31, 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 $ — $ — $ — $ — $ 16 $ — $ — $ 16 Rabbi trust investments Cash equivalents 43 — — 43 — — — — — — — — Fixed income — 2 — 2 — — — — — — — — Life insurance contracts — 24 41 65 — — — — — — — — Rabbi trust investments subtotal 43 26 41 110 — — — — — — — — Total assets 77 26 41 144 — — — — 16 — — 16 Liabilities Deferred compensation obligation — (2 ) — (2 ) — — — — — — — — Total liabilities — (2 ) — (2 ) — — — — — — — — Total net assets (liabilities) $ 77 $ 24 $ 41 $ 142 $ — $ — $ — $ — $ 16 $ — $ — $ 16 _________ (a) PHI excludes cash of $35 million and $57 million at March 31, 2020 and December 31, 2019 , respectively, and includes long-term restricted cash of $12 million and $14 million at March 31, 2020 and December 31, 2019 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Pepco excludes cash of $17 million and $29 million at March 31, 2020 and December 31, 2019 , respectively. DPL excludes cash of $6 million and $13 million at March 31, 2020 and December 31, 2019 , respectively. ACE excludes cash of $8 million and $12 million at March 31, 2020 and December 31, 2019 , respectively, and includes long-term restricted cash of $12 million and $14 million at March 31, 2020 and December 31, 2019 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Reconciliation of Level 3 Assets and Liabilities 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 months ended March 31, 2020 and 2019 : Exelon Generation ComEd PHI and Pepco Three Months Ended March 31, 2020 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, 2019 $ 1,068 $ 511 $ 817 $ 1,328 $ (301 ) $ 41 $ — Total realized / unrealized gains (losses) Included in net income 10 (1 ) 10 (a) 9 — 1 — Included in noncurrent payables to affiliates — (1 ) — (1 ) — — 1 Included in regulatory assets (14 ) — — — (13 ) (b) — (1 ) Change in collateral 1 — 1 1 — — — Purchases, sales, issuances and settlements Purchases 42 3 39 42 — — — Sales (22 ) — (22 ) (22 ) — — — Settlements (14 ) (14 ) — (14 ) — — — Transfers into Level 3 2 — 2 (c) 2 — — — Transfers out of Level 3 15 — 15 (c) 15 — — — Balance as of March 31, 2020 $ 1,088 $ 498 $ 862 $ 1,360 $ (314 ) $ 42 $ — The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of March 31, 2020 $ 187 $ (1 ) $ 187 $ 186 $ — $ 1 $ — Exelon Generation ComEd PHI and Pepco Three Months Ended March 31, 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 (228 ) 2 (231 ) (a) (229 ) — 1 — Included in noncurrent payables to affiliates — 11 — 11 — — (11 ) Included in regulatory assets 20 — — — 9 (b) — 11 Change in collateral 81 — 81 81 — — — Purchases, sales, issuances and settlements Purchases 58 1 57 58 — — — Sales — — — — — — — Settlements (17 ) (17 ) — (17 ) — — — Transfers into Level 3 — — — (c) — — — — Transfers out of Level 3 17 — 17 (c) 17 — — — Balance as of March 31, 2019 $ 838 $ 540 $ 499 $ 1,039 $ (240 ) $ 39 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of March 31, 2019 $ (148 ) $ 2 $ (151 ) $ (149 ) $ — $ 1 $ — __________ (a) Includes a reduction for the reclassification of $177 million and $80 million of realized losses due to the settlement of derivative contracts for the three months ended March 31, 2020 and 2019 , respectively. (b) Includes $23 million of decreases in fair value and an increase for realized losses due to settlements of $10 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 2020 . Includes $14 million of decreases in fair value and an increase for realized losses due to settlements of $5 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 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. 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 months ended March 31, 2020 and 2019 : Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total realized gains (losses) for the three months ended March 31, 2020 $ 72 $ (62 ) $ 1 $ (1 ) $ 72 $ (62 ) $ (1 ) $ 1 Total unrealized gains (losses) for the three months ended March 31, 2020 205 (18 ) 1 (1 ) 205 (18 ) (1 ) 1 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 March 31, 2019 $ (128 ) $ (103 ) $ 1 $ 2 $ (128 ) $ (103 ) $ 2 $ 1 Total unrealized (losses) gains for the three months ended March 31, 2019 (91 ) (60 ) 1 2 (91 ) (60 ) 2 1 Valuation Techniques Used to Determine Fair Value 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 17 — Fair Value of Financial Assets and Liabilities of the Exelon 2019 Form 10-K. Valuation Techniques Used to Determine Net asset Value (Exelon and Generation) 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 private credit 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 private credit 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. Mark-to-Market Derivatives (Exelon, Generation and ComEd) The table below discloses the significant inputs to the forward curve used to value mark-to-market derivatives. Type of trade Fair Value at March 31, 2020 Fair Value at December 31, 2019 Valuation Technique Unobservable Input 2020 Range & Arithmetic Average 2019 Range & Arithmetic Average Mark-to-market derivatives — Economic Hedges (Exelon and Generation) (a)(b) $ 610 $ 558 Discounted Forward power $6 - $136 $27 $9 - $180 $29 Forward gas $1.02 - $8.10 $2.43 $0.83 - $10.72 $2.55 Option Volatility 8% - 304% 70% 8% - 236% 70% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(b) $ 37 $ 45 Discounted Forward power $15 - $136 $31 $25 - $180 $33 Mark-to-market derivatives (Exelon and ComEd) $ (314 ) $ (301 ) Discounted Forward heat (c) 9x - 10x 9.22x 9x - 10x 9.68x Marketability 3% - 7% 5.11% 3% - 7% 4.95% Renewable 90% - 122% 99% 91% - 123% 99% _________ (a) The valuation techniques, unobservable inputs, ranges and arithmetic averages are the same for the asset and liability positions. (b) The fair values do not include cash collateral posted on level three positions of $215 million and $214 million as of March 31, 2020 and December 31, 2019 , 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.

Commitments and Contingencies (

Commitments and Contingencies (All Registrants)	3 Months Ended
	Mar. 31, 2020
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 18 of the Exelon 2019 Form 10-K. 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 March 31, 2020 : Description Exelon PHI Pepco DPL ACE Total commitments $ 513 $ 320 $ 120 $ 89 $ 111 Remaining commitments (a) 95 75 62 8 5 _________ (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 March 31, 2020 , 27 MWs of new generation were developed and Exelon and Generation have incurred costs of $122 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 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 March 31, 2020 , representing commitments potentially triggered by future events were as follow s: Expiration within Total 2020 2021 2022 2023 2024 2025 and beyond Exelon Letters of credit $ 1,464 $ 1,080 $ 384 $ — $ — $ — $ — Surety bonds (a) 849 698 151 — — — — Financing trust guarantees 378 — — — — — 378 Guaranteed lease residual values (b) 27 1 2 4 3 12 5 Total commercial commitments $ 2,718 $ 1,779 $ 537 $ 4 $ 3 $ 12 $ 383 Generation Letters of credit $ 1,449 $ 1,071 $ 378 $ — $ — $ — $ — Surety bonds (a) 685 591 94 — — — — Total commercial commitments $ 2,134 $ 1,662 $ 472 $ — $ — $ — $ — ComEd Letters of credit $ 7 $ 4 $ 3 $ — $ — $ — $ — Surety bonds (a) 15 11 4 — — — — Financing trust guarantees 200 — — — — — 200 Total commercial commitments $ 222 $ 15 $ 7 $ — $ — $ — $ 200 PECO Surety bonds (a) $ 9 $ 8 $ 1 $ — $ — $ — $ — Financing trust guarantees 178 — — — — — 178 Total commercial commitments $ 187 $ 8 $ 1 $ — $ — $ — $ 178 BGE Letters of credit $ 2 $ 2 $ — $ — $ — $ — $ — Surety bonds (a) 17 16 1 — — — — Total commercial commitments $ 19 $ 18 $ 1 $ — $ — $ — $ — PHI Surety bonds (a) $ 21 $ 20 $ 1 $ — $ — $ — $ — Guaranteed lease residual values (b) 27 1 2 4 3 12 5 Total commercial commitments $ 48 $ 21 $ 3 $ 4 $ 3 $ 12 $ 5 Pepco Surety bonds (a) $ 14 $ 14 $ — $ — $ — $ — $ — Guaranteed lease residual values (b) 9 — 1 1 1 4 2 Total commercial commitments $ 23 $ 14 $ 1 $ 1 $ 1 $ 4 $ 2 DPL Surety bonds (a) $ 4 $ 3 $ 1 $ — $ — $ — $ — Guaranteed lease residual values (b) 11 — 1 2 1 5 2 Total commercial commitments $ 15 $ 3 $ 2 $ 2 $ 1 $ 5 $ 2 ACE Surety bonds (a) $ 3 $ 3 $ — $ — $ — $ — $ — Guaranteed lease residual values (b) 7 1 — 1 1 3 1 Total commercial commitments $ 10 $ 4 $ — $ 1 $ 1 $ 3 $ 1 _________ (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 $72 million guaranteed by Exelon and PHI, of which $24 million , $30 million and $18 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 on the Registrants' financial statements. MGP Sites (Exelon and the Utility Registrants). 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 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 March 31, 2020 and December 31, 2019 , 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: March 31, 2020 December 31, 2019 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 $ 472 $ 317 $ 478 $ 320 Generation 104 — 105 — ComEd 301 300 304 303 PECO 19 17 19 17 BGE 2 — 2 — PHI 46 — 48 — Pepco 44 — 46 — 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 a final remedy. The ROD Amendment modified the remedy previously selected by EPA in its 2008 ROD. While the ROD required only that the radiological materials and other wastes at the site be capped, the ROD Amendment requires partial excavation of the radiological materials in addition to the previously selected capping remedy. The ROD Amendment 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 by early 2022. In March 2019 the PRPs received Special Notice Letters from the EPA to perform the Remedial Action work. On October 8, 2019, Cotter (Generation’s indemnitee) provided a non-binding good faith offer to conduct, or finance, a portion of the remedy, subject to certain conditions. The total estimated cost of the remedy, taking into account the current EPA technical requirements and the total costs expected to be incurred collectively 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 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 Cotter'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 Remedial Investigation (RI)/Feasibility Study (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 (now Generation'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 August 31, 2020 so that settlement discussions can 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 RI/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. In September 2019, Pepco and Generation issued a draft “final” RI report which DOEE approved and on October 4, 2019 released this document for review and comment by the public. The 45 day comment period ended on November 18, 2019 and a public meeting was held by Pepco on November 2, 2019. Pepco and Generation will proceed to develop a FS to evaluate possible remedial alternatives for submission to DOEE. The Court has established a schedule for completion of the 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. 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 of those costs based on DOEE’s stated position following a series of meetings attended by representatives from the Anacostia Leadership Council and the Consultative Working Group. On December 27, 2019, DOEE released for review and comment by the public a Focused Feasibility Study (FFS) and a Proposed Plan (PP). The FFS and PP will be the basis for the Interim ROD, which is expected to be completed in September 2020. The FFS and PP are consistent with the DOEE’s stated position to follow an adaptive management approach which will allow several identified “hot spots” in the river to be addressed first while continuing to conduct studies and to monitor the river to evaluate improvements and determine potential future remediation plans. The adaptive management process chosen by DOEE is less intrusive, provides more long term environmental certainty, is less costly, and allows for site specific remediation plans already underway, including the plan for the Benning Road site to proceed to conclusion. Pepco 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, CERCLA separately requires federal and state (here including Washington, D.C.) Natural Resource Trustees (federal or state agencies designated by the President or the relevant state, respectively, or Indian tribes) to conduct an assessment of any damages to natural resources within their jurisdiction as a result of the contamination that is being remediated. The Trustees can seek compensation from responsible parties for such damages, including restoration costs. The Natural Resource Damages (NRD) assessment typically takes place following cleanup because cleanups sometimes also effectively restore affected natural resources. 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, Pepco 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 March 31, 2020 and December 31, 2019 , Exelon and Generation had recorded estimated liabilities of approximately $82 million and $83 million , respectively, in total for asbestos-related bodily injury claims. As of March 31, 2020 , approximately $27 million of this amount related to 268 open claims presented to Generation, while the remaining $55 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. However, management cannot reasonably estimate a range of loss beyond the amounts recorded. 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. On January 8, 2020, the Massachusetts Superior Court affirmed the decision of the EACC denying the City's petition. The City had until March 9, 2020 to appeal the decision and did not. As a result, the decision is final and the case is resolved. 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 U.S. Attorney's Office or the SEC investigations. No loss contingency has been reflected in Exelon's and ComEd's consolidated financial statements as this contingency is neither probable nor reasonably estimable at this time. Management is currently unable to estimate a range of reasonably possible loss as these matters are subject to change. Subsequent to Exelon announcing the receipt of the subpoenas, a putative class action lawsuit has been filed against Exelon and certain officers of Exelon and ComEd alleging misrepresentations or omissions by Exelon purporting to relate to matters that are the subject of the subpoenas and the SEC investigation. In addition, a derivative shareholder lawsuit has been filed against Exelon, its directors and certain officers alleging, among other things, a breach of fiduciary duties also purporting to relate to matters that are the subject of the subpoenas and the SEC investigation. Exelon believes that these claims lack merit and intends to defend against them, and though the costs or any loss associated with the lawsuits cannot be reasonably estimated at this time, Exelon does not believe that the lawsuits, either individually or collectively, will have a material adverse impact on Exelon’s or ComEd’s consolidated financial statements. 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.

Changes in Accumulated Other Co

Changes in Accumulated Other Comprehensive Income (Exelon)	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Currency Items Total Beginning balance $ (2 ) $ (3,165 ) $ (27 ) $ (3,194 ) OCI before reclassifications (1 ) (7 ) (8 ) (16 ) Amounts reclassified from AOCI — 37 — 37 Net current-period OCI (1 ) 30 (8 ) 21 Ending balance $ (3 ) $ (3,135 ) $ (35 ) $ (3,173 ) Three Months Ended March 31, 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 — (38 ) 2 (1 ) (37 ) Amounts reclassified from AOCI — 20 — — 20 Net current-period OCI — (18 ) 2 (1 ) (17 ) Ending balance $ (2 ) $ (2,978 ) $ (31 ) $ (1 ) $ (3,012 ) _________ (a) AOCI amounts are included in the computation of net periodic pension and OPEB cost. See Note 10 — 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. The following table presents income tax benefit (expense) allocated to each component of Exelon's other comprehensive income (loss): Three Months Ended March 31, 2020 2019 Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 4 $ 6 Actuarial loss reclassified to periodic benefit cost (17 ) (13 ) Pension and non-pension postretirement benefit plans valuation adjustment 3 14

Variable Interest Entities (Exe

Variable Interest Entities (Exelon, Generation, PHI and ACE)	3 Months Ended
	Mar. 31, 2020
Variable Interest Entity [Abstract]
Variable Interest Entites (Exelon, Generation, PHI and ACE)	Variable Interest Entities (Exelon, Generation, PHI and ACE) At March 31, 2020 and December 31, 2019 , 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 March 31, 2020 and December 31, 2019 . 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. March 31, 2020 December 31, 2019 Exelon Generation PHI (a) ACE Exelon Generation PHI (a) ACE Cash and cash equivalents $ 51 $ 51 $ — $ — $ 163 $ 163 $ — $ — Restricted cash and cash equivalents 84 81 3 3 88 85 3 3 Accounts receivable Customer 131 131 — — 151 151 — — Other 44 44 — — 39 39 — — Unamortized energy contract assets (b) 22 22 — — 23 23 — — Inventories, net Materials and supplies 231 231 — — 227 227 — — Other current assets 42 38 4 — 32 31 1 — Total current assets 605 598 7 3 723 719 4 3 Property, plant and equipment, net (c) 6,017 6,017 — — 6,022 6,022 — — Nuclear decommissioning trust funds 2,405 2,405 — — 2,741 2,741 — — Unamortized energy contract assets (b) 264 264 — — 250 250 — — Other noncurrent assets 71 56 15 12 89 73 16 14 Total noncurrent assets 8,757 8,742 15 12 9,102 9,086 16 14 Total assets $ 9,362 $ 9,340 $ 22 $ 15 $ 9,825 $ 9,805 $ 20 $ 17 Long-term debt due within one year $ 543 $ 519 $ 24 $ 20 $ 544 $ 523 $ 21 $ 20 Accounts payable 121 121 — — 106 106 — — Accrued expenses 46 46 — — 70 70 — — Unamortized energy contract liabilities 7 7 — — 8 8 — — Other current liabilities 3 3 — — 3 3 — — Total current liabilities 720 696 24 20 731 710 21 20 Long-term debt 502 483 19 16 527 504 23 21 Asset retirement obligations (d) 2,156 2,156 — — 2,128 2,128 — — Unamortized energy contract liabilities 1 1 — — 1 1 — — Other noncurrent liabilities 37 37 — — 89 89 — — Total noncurrent liabilities 2,696 2,677 19 16 2,745 2,722 23 21 Total liabilities $ 3,416 $ 3,373 $ 43 $ 36 $ 3,476 $ 3,432 $ 44 $ 41 _________ (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 $20 million as of March 31, 2020 and December 31, 2019 . (d) Exelon’s and Generation’s balances include liabilities with recourse of $4 million and $3 million as of March 31, 2020 and December 31, 2019 , respectively. As of March 31, 2020 and December 31, 2019 , 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 11— Asset Impairments of the Exelon 2019 Form 10-K 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. EDF has the option to sell its 49.99% equity interest in CENG to Generation exercisable beginning on January 1, 2016 and thereafter until June 30, 2022. On November 20, 2019, Generation received notice of EDF's intention to exercise the put option to sell its interest in CENG to Generation and the put automatically exercised on January 19, 2020 at the end of the sixty-day advance notice period. At this time, Generation cannot reasonably predict the ultimate purchase price that will be paid to EDF for its interest in CENG. The transaction will require approval by the NYPSC, the FERC and the NRC. The process and regulatory approvals could take one to two years or more to complete. See Note 2 - Mergers, Acquisitions and Dispositions of the Exelon 2019 Form 10-K for additional information regarding the Put Option Agreement with EDF. Exelon and Generation, where indicated, provide the following support to CENG: • 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 18 — Commitments and Contingencies of the Exelon 2019 Form 10-K for more details, • 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, and • Exelon has executed an agreement to provide up to $245 million to support the operations of CENG as well as a $165 million guarantee of CENG’s cash pooling agreement with its subsidiaries. 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 ExGen Renewables IV non-recourse debt project financing structure. Refer to Note 12 — Debt and Credit Agreements for additional information on ExGen Renewables IV. As of March 31, 2020 and December 31, 2019 , 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 March 31, 2020 and December 31, 2019 , 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 significant unconsolidated VIE entities: March 31, 2020 December 31, 2019 Commercial Agreement VIEs Equity Investment VIEs Total Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 695 $ 431 $ 1,126 $ 636 $ 443 $ 1,079 Total liabilities (a) 158 223 381 33 227 260 Exelon's ownership interest in VIE (a) — 183 183 — 191 191 Other ownership interests in VIE (a) 538 25 563 604 25 629 _________ (a) These items represent amounts on 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. Exelon and Generation do not have any exposure to loss as they do not have a carrying amount in the equity investment VIEs as of March 31, 2020 and December 31, 2019 . As of March 31, 2020 and December 31, 2019 , 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 this investment in the third quarter of 2019. See Note 11— Asset Impairments of the Exelon 2019 Form 10-K 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.

Supplemental Financial Informat

Supplemental Financial Information (All Registrants)	3 Months Ended
	Mar. 31, 2020
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. Operating revenues Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended March 31, 2020 Operating lease income $ 5 $ 3 $ — $ — $ — $ 1 $ — $ 1 $ — Variable lease income 69 69 — — — — — — — Three Months Ended March 31, 2019 Operating lease income $ 4 $ 3 $ — $ — $ — $ 1 $ — $ 1 $ — Variable lease income 52 52 — — — — — — — Taxes other than income taxes Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended March 31, 2020 Utility taxes (a) $ 218 $ 26 $ 60 $ 31 $ 26 $ 75 $ 69 $ 6 $ — Property 150 69 7 4 39 31 21 9 1 Payroll 63 31 7 4 4 8 2 1 1 Three Months Ended March 31, 2019 Utility taxes (a) $ 223 $ 26 $ 62 $ 34 $ 27 $ 74 $ 69 $ 5 $ — Property 149 71 7 3 37 29 21 8 — Payroll 65 33 7 4 4 7 2 1 1 _________ (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 March 31, 2020 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 47 $ 47 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 82 82 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units (932 ) (932 ) — — — — — — — Non-regulatory agreement units (706 ) (706 ) — — — — — — — Regulatory offset to NDT fund-related activities (b) 709 709 — — — — — — — Decommissioning-related activities (800 ) (800 ) — — — — — — — AFUDC — Equity 23 — 6 3 5 9 6 1 2 Non-service net periodic benefit cost 10 — — — — — — — — Three Months Ended March 31, 2019 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 54 $ 54 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 54 54 — — — — — — — Net unrealized losses on NDT funds Regulatory agreement units 379 379 — — — — — — — Non-regulatory agreement units 280 280 — — — — — — — Regulatory offset to NDT fund-related activities (b) (348 ) (348 ) — — — — — — — Decommissioning-related activities 419 419 — — — — — — — AFUDC — Equity 22 — 5 3 5 9 6 1 2 Non-service net periodic benefit cost 5 — — — — — — — — _________ (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 9 — Asset Retirement Obligations of the Exelon 2019 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 Three Months Ended March 31, 2020 Property, plant and equipment (a) $ 856 $ 290 $ 228 $ 79 $ 97 $ 144 $ 64 $ 38 $ 34 Amortization of regulatory assets (a) 149 — 45 7 46 50 31 10 9 Amortization of intangible assets, net (a) 16 14 — — — — — — — Amortization of energy contract assets and liabilities (b) 2 2 — — — — — — — Nuclear fuel (c) 231 231 — — — — — — — ARO accretion (d) 124 124 — — — — — — — Total depreciation, amortization and accretion $ 1,378 $ 661 $ 273 $ 86 $ 143 $ 194 $ 95 $ 48 $ 43 Three Months Ended March 31, 2019 Property, plant and equipment (a) $ 917 $ 392 $ 219 $ 74 $ 85 $ 127 $ 58 $ 35 $ 25 Amortization of regulatory assets (a) 143 — 32 7 51 53 36 11 6 Amortization of intangible assets, net (a) 15 13 — — — — — — — Nuclear fuel (c) 261 261 — — — — — — — ARO accretion (d) 124 123 — — — — — — — Total depreciation, amortization and accretion $ 1,460 $ 789 $ 251 $ 81 $ 136 $ 180 $ 94 $ 46 $ 31 _________ (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 Three Months Ended March 31, 2020 Pension and non-pension postretirement benefit costs $ 98 $ 27 $ 28 $ 1 $ 15 $ 17 $ 3 $ 1 $ 3 Provision for uncollectible accounts 45 4 7 17 7 10 4 3 3 Other decommissioning-related activity (a) 128 128 — — — — — — — Energy-related options (b) 6 6 — — — — — — — Amortization of rate stabilization deferral (54 ) — — — (35 ) (19 ) (15 ) (4 ) — Discrete impacts from EIMA and FEJA (c) (17 ) — (17 ) — — — — — — Long-term incentive plan (7 ) — — — — — — — — Amortization of operating ROU asset 51 35 — — 8 5 2 2 1 Three Months Ended March 31, 2019 Pension and non-pension postretirement benefit costs $ 106 $ 31 $ 24 $ 2 $ 15 $ 23 $ 6 $ 4 $ 4 Provision for uncollectible accounts 43 — 9 16 8 10 4 4 2 Other decommissioning-related activity (a) (202 ) (202 ) — — — — — — — Energy-related options (b) 37 37 — — — — — — — Amortization of rate stabilization deferral (6 ) — — — — (6 ) (7 ) 1 — Discrete impacts from EIMA and FEJA (c) 28 — 28 — — — — — — Long-term incentive plan 25 — — — — — — — — Amortization of operating ROU asset 53 34 1 — 8 9 2 2 1 _______ (a) Includes the elimination of decommissioning-related activities 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 9 — Asset Retirement Obligations of the Exelon 2019 Form 10-K for additional information regarding the accounting for nuclear decommissioning. (b) Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations. (c) Reflects the change in ComEd's distribution and energy efficiency formula rates. See Note 2 — 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 March 31, 2020 Cash and cash equivalents $ 1,457 $ 821 $ 514 $ 31 $ 11 $ 49 $ 18 $ 7 $ 8 Restricted cash 414 150 211 7 1 37 33 — 3 Restricted cash included in other long-term assets 121 — 108 — — 12 — — 12 Total cash, cash equivalents and restricted cash $ 1,992 $ 971 $ 833 $ 38 $ 12 $ 98 $ 51 $ 7 $ 23 December 31, 2019 Cash and cash equivalents $ 587 $ 303 $ 90 $ 21 $ 24 $ 131 $ 30 $ 13 $ 12 Restricted cash 358 146 150 6 1 36 33 — 2 Restricted cash included in other long-term assets 177 — 163 — — 14 — — 14 Total cash, cash equivalents and restricted cash $ 1,122 $ 449 $ 403 $ 27 $ 25 $ 181 $ 63 $ 13 $ 28 March 31, 2019 Cash and cash equivalents $ 880 $ 537 $ 68 $ 41 $ 12 $ 33 $ 11 $ 7 $ 6 Restricted cash 223 139 17 6 4 39 35 1 3 Restricted cash included in other long-term assets 211 — 193 — — 19 — — 19 Total cash, cash equivalents and restricted cash $ 1,314 $ 676 $ 278 $ 47 $ 16 $ 91 $ 46 $ 8 $ 28 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 For additional information on restricted cash see Note 1 — Significant Accounting Policies of the Exelon 2019 Form 10-K. Supplemental Balance Sheet Information The following tables provide additional information about material items recorded in the Registrants' Consolidated Balance Sheets. Accrued expenses Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE March 31, 2020 Compensation-related accruals (a) $ 557 $ 207 $ 87 $ 39 $ 44 $ 63 $ 22 $ 14 $ 10 Taxes accrued 442 244 85 1 43 114 79 25 7 Interest accrued 407 84 69 33 38 78 37 20 19 December 31, 2019 Compensation-related accruals (a) $ 1,052 $ 422 $ 171 $ 58 $ 78 $ 101 $ 28 $ 19 $ 15 Taxes accrued 414 222 83 3 26 117 90 14 8 Interest accrued 337 65 110 37 46 49 23 8 12 _________ (a) Primarily includes accrued payroll, bonuses and other incentives, vacation and benefits.

Related Party Transactions (All

Related Party Transactions (All Registrants)	3 Months Ended
	Mar. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions (All Registrants)	Related Party Transactions (All Registrants) Operating revenues from affiliates Generation The following table presents Generation’s Operating revenues from affiliates, which are primarily recorded as Purchased power from affiliates and an immaterial amount recorded as Operating and maintenance expense from affiliates at the Utility Registrants: Three Months Ended March 31, 2020 2019 Operating revenues from affiliates: ComEd (a)(b) $ 90 $ 94 PECO (c) 37 45 BGE (d) 99 76 PHI 103 101 Pepco (e) 79 70 DPL (f) 22 23 ACE (g) 2 8 Other 1 1 Total operating revenues from affiliates (Generation) $ 330 $ 317 __________ (a) Generation has an ICC-approved RFP contract with ComEd to provide a portion of ComEd’s electricity supply requirements. Generation also sells RECs and ZECs to ComEd. (b) For the three months ended March 31, 2020 , ComEd’s Purchased power from Generation of $97 million is recorded as Operating revenues from ComEd of $90 million and Purchased power and fuel from ComEd of $7 million at Generation. For the three months ended March 31, 2019 , ComEd’s Purchased power from Generation of $97 million is recorded as Operating revenues from ComEd of $94 million and Purchased power and fuel from ComEd of $3 million at Generation. (c) Generation provides electric supply to PECO under contracts executed through PECO’s competitive procurement process. In addition, Generation has a ten-year agreement with PECO to sell solar AECs. (d) Generation provides a portion of BGE’s energy requirements under its MDPSC-approved market-based SOS and gas commodity programs. (e) Generation provides electric supply to Pepco under contracts executed through Pepco's competitive procurement process approved by the MDPSC and DCPSC. (f) Generation provides a portion of DPL's energy requirements under its MDPSC and DPSC approved market based SOS and gas commodity programs. (g) Generation provides electric supply to ACE under contracts executed through ACE's competitive procurement process. PHI PHI’s Operating revenues from affiliates are primarily with BSC for services that PHISCO provides to BSC. Operating and maintenance expense from affiliates The Registrants receive a variety of corporate support services from BSC. Pepco, DPL and ACE also receive corporate support services from PHISCO. See Note 1 - Significant Accounting Policies for additional information regarding BSC and PHISCO. The following table presents the service company costs allocated to the Registrants: Operating and maintenance from affiliates Capitalized costs Three Months Ended March 31, Three Months Ended March 31, 2020 2019 2020 2019 Exelon BSC $ 113 $ 99 PHISCO 14 22 Generation BSC $ 140 $ 149 11 11 ComEd BSC 72 62 42 25 PECO BSC 37 37 16 22 BGE BSC 41 38 28 21 PHI BSC 37 32 16 19 PHISCO — — 14 22 Pepco BSC 21 21 6 8 PHISCO 30 33 6 9 DPL BSC 13 13 5 5 PHISCO 24 26 4 7 ACE BSC 11 11 4 4 PHISCO 22 23 4 6 Current Receivables from/Payables to affiliates The following tables present current receivables from affiliates and current payables to affiliates: March 31, 2020 Receivables from affiliates: Payables to affiliates: Generation Comed PECO BGE DPL ACE BSC PHISCO Other Total Generation $ 17 $ — $ — $ 1 $ — $ 67 $ — $ 43 $ 128 ComEd $ 69 (a) — — — — 42 — 3 114 PECO 25 — — — — 19 — 7 51 BGE 22 — — — — 27 — 3 52 PHI — — — — — — 3 — 10 13 Pepco 29 — — 1 — — 11 12 2 55 DPL 1 — — — 3 7 9 1 21 ACE 12 — — — — 5 9 1 27 Other 9 1 — — — 1 — — 11 Total $ 167 $ 18 $ — $ 1 $ 1 $ 4 $ 181 $ 30 $ 70 $ 472 December 31, 2019 Receivables from affiliates: Payables to affiliates: Generation Comed PECO BGE DPL ACE BSC PHISCO Other Total Generation $ 27 $ — $ — $ — $ — $ 67 $ — $ 23 $ 117 ComEd $ 78 (a) — — — — 54 — 8 140 PECO 27 — — — — 25 — 3 55 BGE 28 — — — — 34 — 4 66 PHI — — — — — — 4 — 10 14 Pepco 34 — — — — — 16 15 1 66 DPL 7 — — — 3 10 11 1 32 ACE 7 — — — — 7 10 1 25 Other 9 1 1 1 — 1 — — 13 Total $ 190 $ 28 $ 1 $ 1 $ — $ 4 $ 217 $ 36 $ 51 $ 528 __________ (a) At March 31, 2020 and December 31, 2019 , Generation also had a contract liability with ComEd for $27 million and $37 million , respectively, that was included in Other liabilities on Generation’s Consolidated Balance Sheets. At March 31, 2020 and December 31, 2019 , ComEd had a Current Payable to Generation of $42 million and $41 million , respectively, on its Consolidated Balance Sheets, which consisted of Generation’s Current Receivable from ComEd, partially offset by Generation’s contract liability with ComEd. Borrowings from Exelon/PHI intercompany money pool To provide an additional short-term borrowing option that will generally be more favorable to the borrowing participants than the cost of external financing both Exelon and PHI operate an intercompany money pool. Generation, ComEd, PECO, and PHI Corporate participate in the Exelon money pool. Pepco, DPL and ACE participate in the PHI intercompany money pool. Noncurrent Receivables from/Payables to affiliates Generation has long-term payables to ComEd and PECO as a result of the nuclear decommissioning contractual construct whereby, to the extent NDT funds are greater than the underlying ARO at the end of decommissioning, such amounts are due back to ComEd and PECO, as applicable, for payment to their respective customers. See Note 9 — Asset Retirement Obligations of the Exelon 2019 Form 10-K for additional information . The following table presents noncurrent receivables from affiliates at ComEd and PECO which are recorded as noncurrent payables to affiliates at Generation: March 31, 2020 December 31, 2019 ComEd $ 2,040 $ 2,622 PECO 261 480 Other 1 1 Total: $ 2,302 $ 3,103 Long-term debt to financing trusts The following table presents Long-term debt to financing trusts: March 31, 2020 December 31, 2019 Exelon ComEd PECO Exelon ComEd PECO ComEd Financing III $ 206 $ 205 $ — $ 206 $ 205 $ — PECO Trust III 81 — 81 81 — 81 PECO Trust IV 103 — 103 103 — 103 Total $ 390 $ 205 $ 184 $ 390 $ 205 $ 184 Long-term debt to affiliates In connection with the debt obligations assumed by Exelon as part of the Constellation merger, Exelon and subsidiaries of Generation (former Constellation subsidiaries) assumed intercompany loan agreements that mirror the terms and amounts of the third-party debt obligations of Exelon, resulting in intercompany notes payable included in Long-term debt to affiliates in Generation’s Consolidated Balance Sheets and intercompany notes receivable at Exelon Corporate.

Subsequent Events (Exelon and G

Subsequent Events (Exelon and Generation)	3 Months Ended
	Mar. 31, 2020
Subsequent Event [Line Items]
Subsequent Events [Text Block]	Subsequent Events (Exelon and Generation) Sales of Customer Accounts Receivable On April 8, 2020, NER, a bankruptcy remote, special purpose entity, which is wholly-owned by Generation, entered into a revolving accounts receivable financing arrangement with a number of financial institutions and a commercial paper conduit (the Purchasers) to sell certain customer accounts receivable (the Facility). The Facility, whose maximum capacity is $750 million , is scheduled to expire on April 7, 2021, unless renewed by the mutual consent of the parties in accordance with its terms. Under the Facility, NER may sell eligible short-term customer accounts receivable to the Purchasers in exchange for cash and subordinated interest. The transfers are reported as sales of receivables in Exelon’s and Generation’s consolidated financial statements. The subordinated interest in collections upon the receivables sold to the Purchasers is referred to as the deferred purchase price (DPP). Generation continues to service the receivables sold in exchange for a servicing fee. On April 8, 2020, NER received approximately $500 million in cash purchase price in accordance with the initial sale of approximately $1.2 billion

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Description of Business and Basis of Presentation (All Registrants) [Policy Text Block]	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 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 March 31, 2020 and 2019 and for the three 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, 2019 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, 2020 . These C ombined 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) [Policy Text Block]	New Accounting Standards (All Registrants) New Accounting Standards Adopted as of January 1, 2020: The following new authoritative accounting guidance issued by the FASB was adopted as of January 1, 2020 and will be reflected by the Registrants in their consolidated financial statements beginning in the first quarter of 2020. 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 was effective January 1, 2020 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' Customer accounts receivables balances. This guidance did not have a significant impact on the Registrants’ consolidated 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. The standard was effective January 1, 2020 and must be applied on a prospective basis. Exelon, Generation, ComEd, PHI and DPL will apply the new guidance for their goodwill impairment assessments in 2020 and do not expect the updated guidance to have a material impact to their financial statements.
Allowance for Credit Losses on Accounts Receivables (All Registrants) [Policy Text Block]	Allowance for Credit Losses on Accounts Receivables (All Registrants) The allowance for credit losses reflects the Registrants’ best estimates of losses on the customers' accounts receivable balances based on historical experience, current information, and reasonable and supportable forecasts. The allowance for credit losses for Generation’s retail customers is based on accounts receivable aging historical experience coupled with specific identification through a credit monitoring process, which considers current conditions and forward-looking information such as industry trends, macroeconomic factors, changes in the regulatory environment, external credit ratings, publicly available news, payment status, payment history, and the exercise of collateral calls. The allowance for credit losses for Generation wholesale customers is developed using a credit monitoring process, similar to that used for retail customers. When a wholesale customer’s risk characteristics are no longer aligned with the pooled population, Generation uses specific identification to develop an allowance for credit losses. Adjustments to the allowance for credit losses are recorded in Operating and maintenance expense on Generation’s Consolidated Statements of Operations and Comprehensive Income. The allowance for credit losses for the Utility Registrants’ customers is developed by applying loss rates for each Utility Registrant, based on historical loss experience, current conditions and forward-looking risk factors, to the outstanding receivable balance by customer risk segment. Utility Registrants' customer accounts are written off consistent with approved regulatory requirements. Adjustments to the allowance for credit losses are primarily recorded to Operating and maintenance expense on the Utility Registrants' Consolidated Statements of Operations and Comprehensive Income and Regulatory assets on ComEd, BGE and ACE’s Consolidated Balance Sheets. See N ote 3 - Regulatory Matters of the 2019 Form 10-K for add i tional information regarding the regulatory recovery of credit losses on customer accounts receivable at ComEd, BGE and ACE. The Registrants have certain non-customer receivables in Other Deferred debits and other assets which primarily are with governmental agencies and other high-quality counterparties with no history of default. As such, the allowance for credit losses related to these receivables is immaterial. The Registrants monitor these balances and will record an allowance if there are indicators of a decline in credit quality.
Revenue [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.

Regulatory Matters (Tables)

Regulatory Matters (Tables)	3 Months Ended
	Mar. 31, 2020
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 2020 . 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) (a) April 8, 2019 $ (6 ) $ (17 ) 8.91 % December 4, 2019 January 1, 2020 __________ (a) Reflects an increase of $51 million for the initial revenue requirement for 2019 and a decrease of $68 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 6.51% , inclusive of an allowed ROE of 8.91% , reflecting the average rate on 30-year treasury notes plus 580 basis points. 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 16, 2020 $ (11 ) 8.38 % Fourth quarter of 2020 Pepco - District of Columbia (Electric) (b) May 30, 2019 (amended April 8, 2020) 147 10.3 % Fourth quarter of 2020 DPL - Maryland (Electric) December 5, 2019 (amended April 23, 2020) 17 10.3 % Third quarter of 2020 DPL - Delaware (Gas) (c) February 21, 2020 (amended March 17, 2020) 9 10.3 % First quarter of 2021 DPL - Delaware (Electric) (d) March 6, 2020 (amended April 16, 2020) 24 10.3 % First quarter of 2021 __________ (a) Reflects an increase of $51 million for the initial revenue requirement for 2020 and a decrease of $62 million related to the annual reconciliation for 2019. The revenue requirement for 2020 and annual reconciliation for 2019 provides for a weighted average debt and equity return on distribution rate base of 6.28% , inclusive of an allowed ROE of 8.38% , reflecting the average rate on 30-year treasury notes plus 580 basis points. (b) Reflects a three-year cumulative multi-year plan and total requested revenue requirement increases of $77 million , $37 million and $33 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. (c) The rates will go into effect on September 21, 2020, subject to refund. (d) The rates will go into effect on October 6, 2020, subject to refund.
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 March 31, 2020 $ 60 $ 2 $ — $ 51 $ 7 $ 4 $ 3 $ — December 31, 2019 63 3 — 53 7 4 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.

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	3 Months Ended
	Mar. 31, 2020
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 for the three months ended March 31, 2019 and March 31, 2020 Contract Assets Contract Liabilities Exelon Generation Exelon Generation Balance as of December 31, 2018 $ 187 $ 187 $ 27 $ 42 Consideration received or due (26 ) (26 ) 21 63 Revenues recognized (a) 26 26 (23 ) (66 ) Balance at March 31, 2019 $ 187 $ 187 $ 25 $ 39 Balance as of December 31, 2019 $ 174 $ 174 $ 33 $ 71 Consideration received or due (19 ) (19 ) 20 55 Revenues recognized (b) 17 17 (24 ) (70 ) Balance at March 31, 2020 $ 172 $ 172 $ 29 $ 56 __________ (a) Revenues recognized in the three months ended March 31, 2019 , which were included in contract liabilities at December 31, 2018 , were approximately $ 5 million for both Exelon and Generation. (b) Revenues recognized in the three months ended March 31, 2020 , which were included in contract liabilities at December 31, 2019 , were approximately $ 9 million and $ 19 million for Exelon and Generation, respectively.
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 March 31, 2020 . 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. 2020 2021 2022 2023 2024 and thereafter Total Exelon $ 273 $ 144 $ 64 $ 45 $ 198 $ 724 Generation 330 200 79 45 198 852

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2020
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 months ended March 31, 2020 and 2019 is as follows: Three Months Ended March 31, 2020 and 2019 Generation (a) ComEd PECO BGE PHI Other (b) Intersegment Exelon Operating revenues (c) : 2020 Competitive businesses electric revenues $ 3,752 $ — $ — $ — $ — $ — $ (326 ) $ 3,426 Competitive businesses natural gas revenues 672 — — — — — (3 ) 669 Competitive businesses other revenues 309 — — — — — (1 ) 308 Rate-regulated electric revenues — 1,439 604 613 1,104 — (12 ) 3,748 Rate-regulated natural gas revenues — — 209 324 64 — (2 ) 595 Shared service and other revenues — — — — 3 480 (482 ) 1 Total operating revenues $ 4,733 $ 1,439 $ 813 $ 937 $ 1,171 $ 480 $ (826 ) $ 8,747 2019 Competitive businesses electric revenues $ 4,337 $ — $ — $ — $ — $ — $ (315 ) $ 4,022 Competitive businesses natural gas revenues 879 — — — — — (1 ) 878 Competitive businesses other revenues 80 — — — — — (1 ) 79 Rate-regulated electric revenues — 1,408 620 658 1,153 — (8 ) 3,831 Rate-regulated natural gas revenues — — 280 318 71 — (4 ) 665 Shared service and other revenues — — — — 4 455 (457 ) 2 Total operating revenues $ 5,296 $ 1,408 $ 900 $ 976 $ 1,228 $ 455 $ (786 ) $ 9,477 Intersegment revenues (d) : 2020 $ 330 $ 5 $ 2 $ 6 $ 3 $ 479 $ (824 ) $ 1 2019 317 4 1 6 4 453 (785 ) — Depreciation and amortization: 2020 $ 304 $ 273 $ 86 $ 143 $ 194 $ 21 $ — $ 1,021 2019 405 251 81 136 180 22 — 1,075 Operating expenses: 2020 $ 4,400 $ 1,151 $ 625 $ 688 $ 1,000 $ 481 $ (816 ) $ 7,529 2019 4,963 1,135 678 756 1,054 459 (783 ) 8,262 Interest expense, net: 2020 $ 109 $ 94 $ 36 $ 32 $ 67 $ 72 $ — $ 410 2019 111 87 33 29 65 78 — 403 Generation (a) ComEd PECO BGE PHI Other (b) Intersegment Exelon Income (loss) before income taxes: 2020 $ (547 ) $ 204 $ 155 $ 222 $ 119 $ (69 ) $ 1 $ 85 2019 652 197 193 196 122 (78 ) — 1,282 Income Taxes: 2020 $ (389 ) $ 36 $ 15 $ 41 $ 11 $ (8 ) $ — $ (294 ) 2019 224 40 25 36 5 (20 ) — 310 Net income (loss): 2020 $ (161 ) $ 168 $ 140 $ 181 $ 108 $ (61 ) $ 1 $ 376 2019 422 157 168 160 117 (58 ) — 966 Capital Expenditures 2020 $ 558 $ 506 $ 259 $ 283 $ 376 $ 34 $ — $ 2,016 2019 511 503 222 258 358 21 — 1,873 Total assets: March 31, 2020 $ 47,882 $ 33,146 $ 11,535 $ 10,789 $ 22,753 $ 8,337 $ (9,765 ) $ 124,677 December 31, 2019 48,995 32,765 11,469 10,634 22,719 8,484 (10,089 ) 124,977 __________ (a) See Note 18 — Related Party Transactions for additional information on intersegment revenues. (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) : 2020 Rate-regulated electric revenues $ 544 $ 286 $ 276 $ — $ (2 ) $ 1,104 Rate-regulated natural gas revenues — 64 — — — 64 Shared service and other revenues — — — 93 (90 ) 3 Total operating revenues $ 544 $ 350 $ 276 $ 93 $ (92 ) $ 1,171 2019 Rate-regulated electric revenues $ 575 $ 310 $ 273 $ — $ (5 ) $ 1,153 Rate-regulated natural gas revenues — 70 — — 1 71 Shared service and other revenues — — — 106 (102 ) 4 Total operating revenues $ 575 $ 380 $ 273 $ 106 $ (106 ) $ 1,228 Intersegment revenues: 2020 $ 1 $ 2 $ 1 $ 92 $ (93 ) $ 3 2019 2 2 1 105 (106 ) 4 Depreciation and amortization: 2020 $ 95 $ 48 $ 43 $ 9 $ (1 ) $ 194 2019 94 46 31 10 (1 ) 180 Operating expenses: 2020 $ 462 $ 284 $ 251 $ 93 $ (90 ) $ 1,000 2019 491 308 252 108 (105 ) 1,054 Interest expense, net: 2020 $ 34 $ 16 $ 15 $ 3 $ (1 ) $ 67 2019 34 15 14 3 (1 ) 65 Income (loss) before income taxes: 2020 $ 57 $ 52 $ 14 $ 106 $ (110 ) $ 119 2019 57 60 10 113 (118 ) 122 Income Taxes: 2020 $ 5 $ 7 $ 1 $ (2 ) $ — $ 11 2019 2 7 — (4 ) — 5 Net income (loss): 2020 $ 52 $ 45 $ 13 $ (5 ) $ 3 $ 108 2019 55 53 10 (5 ) 4 117 Capital Expenditures 2020 $ 180 $ 95 $ 101 $ — $ — $ 376 2019 144 78 128 8 — 358 Total assets: March 31, 2020 $ 8,837 $ 4,849 $ 3,978 $ 11,241 $ (6,152 ) $ 22,753 December 31, 2019 8,661 4,830 3,933 11,105 (5,810 ) 22,719 __________ (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 March 31, 2020 Revenues from external customers (a) Intersegment Revenues Total Revenues Contracts with customers Other (b) Total Mid-Atlantic $ 1,264 $ (96 ) $ 1,168 $ 6 $ 1,174 Midwest 944 64 1,008 (6 ) 1,002 New York 335 (21 ) 314 — 314 ERCOT 155 28 183 7 190 Other Power Regions 1,007 72 1,079 (7 ) 1,072 Total Competitive Businesses Electric Revenues 3,705 47 3,752 — 3,752 Competitive Businesses Natural Gas Revenues 503 169 672 — 672 Competitive Businesses Other Revenues (c) 99 210 309 — 309 Total Generation Consolidated Operating Revenues $ 4,307 $ 426 $ 4,733 $ — $ 4,733 Three Months Ended March 31, 2019 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,286 $ (24 ) $ 1,262 $ (6 ) $ 1,256 Midwest 1,055 59 1,114 (6 ) 1,108 New York 409 (16 ) 393 — 393 ERCOT 130 79 209 3 212 Other Power Regions 1,165 194 1,359 (6 ) 1,353 Total Competitive Businesses Electric Revenues 4,045 292 4,337 (15 ) 4,322 Competitive Businesses Natural Gas Revenues 584 295 879 15 894 Competitive Businesses Other Revenues (c) 120 (40 ) 80 — 80 Total Generation Consolidated Operating Revenues $ 4,749 $ 547 $ 5,296 $ — $ 5,296 __________ (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 $179 million and losses of $52 million in 2020 and 2019 , respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Three Months Ended March 31, 2020 Three Months Ended March 31, 2019 RNF from external customers (a) Intersegment RNF Total RNF RNF from external customers (a) Intersegment RNF Total RNF Mid-Atlantic $ 559 $ 8 $ 567 $ 679 $ 4 $ 683 Midwest 732 (5 ) 727 769 2 771 New York 189 4 193 262 3 265 ERCOT 76 4 80 98 (24 ) 74 Other Power Regions 177 (19 ) 158 174 (18 ) 156 Total Revenues net of purchased power and fuel expense for Reportable Segments 1,733 (8 ) 1,725 1,982 (33 ) 1,949 Other (b) 296 8 304 109 33 142 Total Generation Revenues net of purchased power and fuel expense $ 2,029 $ — $ 2,029 $ 2,091 $ — $ 2,091 __________ (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 $132 million and losses of $28 million in 2020 and 2019 , 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 March 31, 2020 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 701 $ 382 $ 339 $ 534 $ 236 $ 161 $ 137 Small commercial & industrial 362 99 67 115 35 43 37 Large commercial & industrial 134 53 103 253 188 23 42 Public authorities & electric railroads 13 7 7 15 9 3 3 Other (a) 211 58 79 169 60 54 55 Total rate-regulated electric revenues (b) $ 1,421 $ 599 $ 595 $ 1,086 $ 528 $ 284 $ 274 Rate-regulated natural gas revenues Residential $ — $ 150 $ 206 $ 40 $ — $ 40 $ — Small commercial & industrial — 51 34 17 — 17 — Large commercial & industrial — — 51 1 — 1 — Transportation — 6 — 4 — 4 — Other (c) — 1 9 2 — 2 — Total rate-regulated natural gas revenues (d) $ — $ 208 $ 300 $ 64 $ — $ 64 $ — Total rate-regulated revenues from contracts with customers $ 1,421 $ 807 $ 895 $ 1,150 $ 528 $ 348 $ 274 Other revenues Revenues from alternative revenue programs $ 12 $ 2 $ 36 $ 18 $ 15 $ 1 $ 1 Other rate-regulated electric revenues (e) 6 3 3 3 1 1 1 Other rate-regulated natural gas revenues (e) — 1 3 — — — — Total other revenues $ 18 $ 6 $ 42 $ 21 $ 16 $ 2 $ 2 Total rate-regulated revenues for reportable segments $ 1,439 $ 813 $ 937 $ 1,171 $ 544 $ 350 $ 276 Three Months Ended March 31, 2019 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 710 $ 409 $ 385 $ 579 $ 256 $ 185 $ 138 Small commercial & industrial 360 96 70 120 38 48 34 Large commercial & industrial 132 48 110 267 204 24 39 Public authorities & electric railroads 13 7 7 14 8 3 3 Other (a) 217 62 80 157 53 47 57 Total rate-regulated electric revenues (b) $ 1,432 $ 622 $ 652 $ 1,137 $ 559 $ 307 $ 271 Rate-regulated natural gas revenues Residential $ — $ 198 $ 219 $ 44 $ — $ 44 $ — Small commercial & industrial — 72 35 19 — 19 — Large commercial & industrial — 1 50 1 — 1 — Transportation — 7 — 4 — 4 — Other (c) — 2 4 3 — 3 — Total rate-regulated natural gas revenues (d) $ — $ 280 $ 308 $ 71 $ — $ 71 $ — Total rate-regulated revenues from contracts with customers $ 1,432 $ 902 $ 960 $ 1,208 $ 559 $ 378 $ 271 Other revenues Revenues from alternative revenue programs $ (28 ) $ (3 ) $ 10 $ 15 $ 14 $ — $ 1 Other rate-regulated electric revenues (e) 4 1 3 4 2 1 1 Other rate-regulated natural gas revenues (e) — — 3 1 — 1 — Total other revenues $ (24 ) $ (2 ) $ 16 $ 20 $ 16 $ 2 $ 2 Total rate-regulated revenues for reportable segments $ 1,408 $ 900 $ 976 $ 1,228 $ 575 $ 380 $ 273 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates of $5 million , $2 million , $6 million , $3 million , $1 million , $2 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, in 2020 and $4 million , $1 million , $2 million , $3 million , $2 million , $2 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL and ACE, respectively, in 2019 . (c) Includes revenues from off-system natural gas sales. (d) Includes operating revenues from affiliates of less than $1 million and $3 million at PECO and BGE, respectively, in 2020 and less than $1 million and $4 million at PECO and BGE, respectively, in 2019 . (e) Includes late payment charge revenues.

Accounts Receivable (Tables)

Accounts Receivable (Tables)	3 Months Ended
	Mar. 31, 2020
Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]
Unbilled customer revenue	The following table provides additional information about unbilled customer revenues recorded in the Registrants' Consolidated Balance Sheets. Unbilled customer revenues (a) Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE March 31, 2020 $ 1,225 $ 698 $ 160 $ 96 $ 134 $ 137 $ 75 $ 42 $ 20 December 31, 2019 1,535 807 218 146 170 194 100 61 33 _________ (a) Unbilled customer revenues are classified in customer accounts receivables, net in the Registrants' Consolidated Balance Sheets.
Allowance for credit loss rollforward	Allowance for Credit Losses on Accounts Receivable The following table presents the rollforward of Allowance for Credit Losses on Customer Accounts Receivable. Three Months Ended March 31, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of December 31, 2019 $ 243 $ 80 $ 59 $ 55 $ 12 $ 37 $ 13 $ 11 $ 13 Plus: Current Period Provision for Expected Credit Losses 55 4 18 18 8 7 3 2 2 Less: Write-offs, net of recoveries (a) 20 3 6 7 2 2 1 — 1 Balance as of March 31, 2020 $ 278 $ 81 $ 71 $ 66 $ 18 $ 42 $ 15 $ 13 $ 14 _________ (a) Recoveries were not material to the Registrants. The following table presents the rollforward of Allowance for Credit Losses on Other Accounts Receivable. Three Months Ended March 31, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of December 31, 2019 $ 48 $ — $ 20 $ 7 $ 5 $ 16 $ 7 $ 4 $ 5 Plus: Current Period Provision for Expected Credit Losses 8 — 3 1 2 2 1 — 1 Less: Write-offs, net of recoveries (a) 4 — 1 1 2 — — — — Balance as of March 31, 2020 $ 52 $ — $ 22 $ 7 $ 5 $ 18 $ 8 $ 4 $ 6 _________ (a) Recoveries were not material to the Registrants.
Purchases and sales of accounts receivable	Generation is required, under supplier tariffs in ISO-NE, MISO, NYISO and PJM, to sell customer and other receivables to utility companies, which include the Utility Registrants. The Utility Registrants are required, under separate legislation and regulations in Illinois, Pennsylvania, Maryland, District of Columbia and New Jersey, to purchase certain receivables from alternative retail electric and, as applicable, natural gas suppliers that participate in the utilities' consolidated billing. The following tables present the total receivables purchased and sold. Three Months Ended March 31, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Total Receivables Purchased $ 781 $ — $ 280 $ 284 $ 195 $ 264 $ 165 $ 53 $ 46 Total Receivables Sold 507 749 — — — — — — — Related Party Transactions: Receivables purchased from Generation — — 34 67 69 72 51 13 8 Receivables sold to the Utility Registrants — 242 — — — — — — —

Early Plant Retirements (Tables

Early Plant Retirements (Tables)	3 Months Ended
	Mar. 31, 2020
Property, Plant and Equipment [Abstract]
Restructuring and Related Costs [Table Text Block]	As a result of the early nuclear plant retirement decision at TMI, 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. The total impact for the three months ended March 31, 2019 are summarized in the table below. Income statement expense (pre-tax) Three Months Ended March 31, 2019 Depreciation and amortization Accelerated depreciation $ 74 Accelerated nuclear fuel amortization 5 Operating and maintenance (a) (83 ) Total $ (4 ) _________ (a) Primarily reflects the net impacts associated with the remeasurement of the TMI ARO. See Note 9 — Asset Retirement Obligations of the 2019 Form 10-K 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 March 31, 2020 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. March 31, 2020 Asset Balances Materials and supplies inventory $ 32 Fuel inventory 12 Property, plant and equipment, net 902 Liability Balances Asset retirement obligation (3 ) The following table provides the balance sheet amounts as of March 31, 2020 for Exelon's and Generation's significant assets and liabilities associated with these three nuclear plants. Depreciation provisions are based on the estimated useful lives of these nuclear generating stations, which reflect the first renewal of the operating licenses. Dresden Byron Braidwood Total Asset Balances Materials and supplies inventory, net $ 68 $ 68 $ 81 $ 217 Nuclear fuel inventory, net 204 172 203 579 Completed plant, net 1,084 1,343 1,390 3,817 Construction work in progress 16 22 32 70 Liability Balances Asset retirement obligation (1,301 ) (596 ) (554 ) (2,451 ) NRC License First Renewal Term 2029 (Unit 2) 2044 (Unit 1) 2046 (Unit 1) 2031 (Unit 3) 2046 (Unit 2) 2047 (Unit 2)

Nuclear Decommissioning (Tables

Nuclear Decommissioning (Tables)	3 Months Ended
	Mar. 31, 2020
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, 2019 to March 31, 2020 : Nuclear decommissioning ARO at December 31, 2019 (a) $ 10,504 Accretion expense 121 Costs incurred related to decommissioning plants (20 ) Nuclear decommissioning ARO at March 31, 2020 (a) $ 10,605 _________ (a) Includes $107 million and $112 million as the current portion of the ARO at March 31, 2020 and December 31, 2019 , respectively, which is included in Other current liabilities in Exelon’s and Generation’s Consolidated Balance Sheets.

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2020
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
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 March 31, 2020 Exelon (a) Generation (a) 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 34.0 0.7 8.3 0.1 5.7 5.8 4.7 6.6 6.7 Qualified NDT fund income (235.8) 36.4 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (4.5) 0.5 (0.2) — (0.1) (0.1) — (0.2) (0.2) Plant basis differences (23.0) — (1.1) (8.4) (1.2) (1.4) (2.1) (0.7) (0.8) Production tax credits and other credits (9.9) 1.3 (0.2) — (0.2) — — — — Noncontrolling interests 10.6 (1.6) — — — — — — — Excess deferred tax amortization (71.7) — (10.5) (3.0) (7.3) (15.5) (14.2) (12.7) (18.8) Tax Settlements (79.1) 12.2 — — — — — — — Other 12.5 0.6 0.3 — 0.6 (0.6) (0.6) (0.5) (0.8) Effective income tax rate (345.9)% 71.1% 17.6% 9.7% 18.5% 9.2% 8.8% 13.5% 7.1% _________ (a) Generation recognized a loss before income taxes for the quarter ended March 31, 2020 . As a result, positive percentages represent an income tax benefit for the period presented. At the consolidated level, positive percentages represent income tax expense. Three Months Ended March 31, 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 3.9 3.1 8.2 1.0 6.3 4.7 2.1 6.5 6.7 Qualified NDT fund income 7.2 14.2 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (0.5) (0.9) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (1.4) — (0.5) (6.7) (0.9) (1.7) (2.0) (0.7) (2.3) Production tax credits and other credits (0.8) (1.5) — — — — — — — Noncontrolling interests (0.6) (1.1) — — — — — — — Excess deferred tax amortization (4.7) — (8.5) (2.5) (7.9) (19.4) (17.9) (15.6) (23.9) Other 0.1 (0.5) 0.3 0.2 — (0.3) 0.4 0.7 (1.2) Effective income tax rate 24.2% 34.3% 20.3% 13.0% 18.4% 4.1% 3.5% 11.7% —%
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	Exelon, Generation, PHI and ACE have the following unrecognized tax benefits as of March 31, 2020 and December 31, 2019 . ComEd, PECO, BGE, Pepco and DPL's amounts are not material. Exelon Generation PHI ACE March 31, 2020 $ 98 $ 32 $ 49 $ 14 December 31, 2019 507 441 48 14
Summary of Positions for which Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Table Text Block]	The following table represents Exelon's, PHI's and ACE's 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 March 31, 2020 . Generation's, ComEd's, PECO's, BGE's, Pepco's and DPL's amounts are not material. Exelon PHI ACE (a) $ 14 $ 14 $ 14 _________ (a) The unrecognized tax benefit related to ACE, if recognized, may be included in future base rates and that portion would have no impact to the effective tax rate.

Retirement Benefits (Tables)

Retirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2020
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 months ended March 31, 2020 and 2019 . Pension Benefits OPEB 2020 2019 2020 2019 Components of net periodic benefit cost: Service cost $ 97 $ 89 $ 23 $ 24 Interest cost 189 221 38 47 Expected return on assets (318 ) (307 ) (41 ) (38 ) Amortization of: Prior service cost (benefit) 1 — (31 ) (45 ) Actuarial loss 128 104 12 11 Net periodic benefit cost $ 97 $ 107 $ 1 $ (1 )
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 March 31, Pension and OPEB Costs 2020 2019 Exelon $ 98 $ 106 Generation 27 31 ComEd 28 24 PECO 1 2 BGE 16 16 PHI 17 23 Pepco 3 6 DPL 1 4 ACE 3 4
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 months ended March 31, 2020 and 2019 , respectively. Three Months Ended March 31, Savings Plan Matching Contributions 2020 2019 Exelon $ 33 $ 31 Generation 13 13 ComEd 7 7 PECO 3 2 BGE 2 2 PHI 3 4 Pepco 1 1 DPL 1 1 ACE — 1

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 and December 31, 2019 : March 31, 2020 Exelon Generation ComEd Derivatives Total Economic Hedges Proprietary Trading Collateral (a)(b) Netting (a) Subtotal Economic Hedges Mark-to-market derivative assets (current assets) $ 649 $ 4,010 $ 63 $ 277 $ (3,701 ) $ 649 $ — Mark-to-market derivative assets (noncurrent assets) 625 1,878 23 112 (1,388 ) 625 — Total mark-to-market derivative assets 1,274 5,888 86 389 (5,089 ) 1,274 — Mark-to-market derivative liabilities (current liabilities) (252 ) (4,219 ) (37 ) 339 3,701 (216 ) (36 ) Mark-to-market derivative liabilities (noncurrent liabilities) (416 ) (1,676 ) (11 ) 161 1,388 (138 ) (278 ) Total mark-to-market derivative liabilities (668 ) (5,895 ) (48 ) 500 5,089 (354 ) (314 ) Total mark-to-market derivative net assets (liabilities) $ 606 $ (7 ) $ 38 $ 889 $ — $ 920 $ (314 ) December 31, 2019 Exelon Generation ComEd Description Total Economic Proprietary Collateral Netting (a) Subtotal Economic Mark-to-market derivative assets $ 675 $ 3,506 $ 72 $ 287 $ (3,190 ) $ 675 $ — Mark-to-market derivative assets 508 1,238 25 122 (877 ) 508 — Total mark-to-market derivative assets 1,183 4,744 97 409 (4,067 ) 1,183 — Mark-to-market derivative liabilities (236 ) (3,713 ) (38 ) 357 3,190 (204 ) (32 ) Mark-to-market derivative liabilities (380 ) (1,140 ) (11 ) 163 877 (111 ) (269 ) Total mark-to-market derivative liabilities (616 ) (4,853 ) (49 ) 520 4,067 (315 ) (301 ) Total mark-to-market derivative net assets (liabilities) $ 567 $ (109 ) $ 48 $ 929 $ — $ 868 $ (301 ) _________ (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), $644 million and $511 million represents variation margin on the exchanges at March 31, 2020 and December 31, 2019 respectively.
Economic Hedges (Commodity Price Risk)	For the three months ended March 31, 2020 and 2019 , 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 2020 2019 Income Statement Location Gain (Loss) Operating revenues $ 175 $ (50 ) Purchased power and fuel (47 ) 30 Total Exelon and Generation $ 128 $ (20 )
Disclosure of Credit Derivatives [Table Text Block]	The following tables provide information on Generation’s credit exposure for all derivative instruments, NPNS and payables and receivables, net of collateral and instruments that are subject to master netting agreements, as of March 31, 2020 . 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. Rating as of March 31, 2020 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 $ 915 $ 22 $ 893 — $ — Non-investment grade 60 49 11 No external ratings Internally rated — investment grade 228 1 227 Internally rated — non-investment grade 157 22 135 Total $ 1,360 $ 94 $ 1,266 — $ — Net Credit Exposure by Type of Counterparty As of Financial institutions $ 18 Investor-owned utilities, marketers, power producers 983 Energy cooperatives and municipalities 224 Other 41 Total $ 1,266 _________ (a) As of March 31, 2020 , credit collateral held from counterparties where Generation had credit exposure included $29 million of cash and $65 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 March 31, 2020 December 31, 2019 Gross fair value of derivative contracts containing this feature (a) $ (1,002 ) $ (956 ) Offsetting fair value of in-the-money contracts under master netting arrangements (b) 699 649 Net fair value of derivative contracts containing this feature (c) $ (303 ) $ (307 ) _________ (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 March 31, 2020 and December 31, 2019 , 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. March 31, 2020 December 31, 2019 Cash collateral posted $ 977 $ 982 Letters of credit posted 256 264 Cash collateral held 105 103 Letters of credit held 115 112 Additional collateral required in the event of a credit downgrade below investment grade 1,468 1,509

Debt and Credit Agreements (Tab

Debt and Credit Agreements (Tables)	3 Months Ended
	Mar. 31, 2020
Line of Credit Facility [Line Items]
Schedule of Long-term Debt Instruments [Table Text Block]	During the three months ended March 31, 2020 , the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Generation Energy Efficiency Project Financing (a) 3.95 % August 31, 2020 $ 2 Funding to install energy conservation measures for the Fort Meade project. Generation Energy Efficiency Project Financing (a) 2.53 % April 30, 2021 1 Funding to install energy conservation measures for the Fort AP Hill project. ComEd First Mortgage Bonds, Series 129 3.00 % March 1, 2050 650 Repay a portion of outstanding commercial paper obligations and to fund general corporate purposes. ComEd First Mortgage Bonds, Series 128 2.20 % March 1, 2030 350 Repay a portion of outstanding commercial paper obligations and fund other general corporate purposes. Pepco (b) First Mortgage Bonds 2.53 % February 25, 2030 150 Repay existing indebtedness and for general corporate purposes. __________ (a) For Energy Efficiency Project Financing, the maturity dates represent the expected date of project completion, upon which the respective customer assumes the outstanding debt. (b) On February 25, 2020, Pepco entered into a purchase agreement of First Mortgage Bonds for $150 million at 3.28% due on September 23, 2050. The closing date of the issuance is expected to occur in September 2020.
Commercial Paper [Member]
Line of Credit Facility [Line Items]
Schedule of Commercial Paper Borrowings [Table Text Block]	The following table reflects the Registrants' commercial paper programs as of March 31, 2020 and December 31, 2019 . PECO had no commercial paper borrowings as of both March 31, 2020 and December 31, 2019 . Outstanding Commercial Average Interest Rate on Commercial Paper Issuer March 31, 2020 December 31, 2019 March 31, 2020 December 31, 2019 Exelon (a) $ 979 $ 870 2.91 % 2.25 % Generation 595 320 2.01 % 1.84 % ComEd — 130 — % 2.38 % BGE 141 76 4.45 % 2.46 % PHI (b) 108 208 4.25 % N/A PEPCO — 82 — % 2.56 % DPL 54 56 4.17 % 2.02 % ACE 54 70 4.32 % 2.43 % __________ (a) Includes outstanding commercial paper at Exelon Corporate of $135 million and $136 million with average interest rates on commercial paper borrowings of 4.20% and 1.92% at March 31, 2020 and December 31, 2019, respectively. (b) Includes the consolidated amounts of Pepco, DPL, and ACE.

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 and December 31, 2019 . 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. March 31, 2020 December 31, 2019 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 $ 37,656 $ 36,908 $ 2,556 $ 39,464 $ 36,039 $ 37,453 $ 2,580 $ 40,033 Generation 8,449 7,034 1,330 8,364 7,974 7,304 1,366 8,670 ComEd 9,478 10,483 — 10,483 8,491 9,848 — 9,848 PECO 3,406 3,762 50 3,812 3,405 3,868 50 3,918 BGE 3,271 3,572 — 3,572 3,270 3,649 — 3,649 PHI 6,708 5,602 1,176 6,778 6,563 5,902 1,164 7,066 Pepco 3,015 3,009 483 3,492 2,864 3,198 388 3,586 DPL 1,575 1,334 271 1,605 1,567 1,408 311 1,719 ACE 1,325 991 421 1,412 1,327 1,026 464 1,490 Long-Term Debt to Financing Trusts (a) Exelon $ 390 $ — $ 387 $ 387 $ 390 $ — $ 428 $ 428 ComEd 205 — 204 204 205 — 227 227 PECO 184 — 183 183 184 — 201 201 SNF Obligation Exelon $ 1,204 $ 723 $ — $ 723 $ 1,199 $ 1,055 $ — $ 1,055 Generation 1,204 723 — 723 1,199 1,055 — 1,055 ____ (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 March 31, 2020 and December 31, 2019 : Exelon and Generation Exelon Generation As of March 31, 2020 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) $ 1,399 $ — $ — $ — $ 1,399 $ 591 $ — $ — $ — $ 591 NDT fund investments Cash equivalents (b) 373 79 — — 452 373 79 — — 452 Equities 2,603 1,377 — 1,080 5,060 2,603 1,377 — 1,080 5,060 Fixed income Corporate debt — 1,412 258 — 1,670 — 1,412 258 — 1,670 U.S. Treasury and agencies 1,723 141 — — 1,864 1,723 141 — — 1,864 Foreign governments — 37 — — 37 — 37 — — 37 State and municipal debt — 87 — — 87 — 87 — — 87 Other (c) — 26 — 872 898 — 26 — 872 898 Fixed income subtotal 1,723 1,703 258 872 4,556 1,723 1,703 258 872 4,556 Private credit — — 240 546 786 — — 240 546 786 Private equity — — — 444 444 — — — 444 444 Real estate — — — 636 636 — — — 636 636 NDT fund investments subtotal (d) 4,699 3,159 498 3,578 11,934 4,699 3,159 498 3,578 11,934 Rabbi trust investments Cash equivalents 51 — — — 51 4 — — — 4 Mutual funds 75 — — — 75 23 — — — 23 Fixed income — 11 — — 11 — — — — — Life insurance contracts — 72 42 — 114 — 22 — — 22 Rabbi trust investments subtotal 126 83 42 — 251 27 22 — — 49 Commodity derivative assets Economic hedges 714 3,135 2,039 — 5,888 714 3,135 2,039 — 5,888 Proprietary trading — 29 57 — 86 — 29 57 — 86 Effect of netting and allocation of collateral (e)(f) (868 ) (2,770 ) (1,062 ) — (4,700 ) (868 ) (2,770 ) (1,062 ) — (4,700 ) Commodity derivative assets subtotal (154 ) 394 1,034 — 1,274 (154 ) 394 1,034 — 1,274 Total assets 6,070 3,636 1,574 3,578 14,858 5,163 3,575 1,532 3,578 13,848 Exelon Generation As of March 31, 2020 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 (990 ) (3,476 ) (1,743 ) — (6,209 ) (990 ) (3,476 ) (1,429 ) — (5,895 ) Proprietary trading — (28 ) (20 ) — (48 ) — (28 ) (20 ) — (48 ) Effect of netting and allocation of collateral (e)(f) 994 3,318 1,277 — 5,589 994 3,318 1,277 — 5,589 Commodity derivative liabilities subtotal 4 (186 ) (486 ) — (668 ) 4 (186 ) (172 ) — (354 ) Deferred compensation obligation — (126 ) — — (126 ) — (34 ) — — (34 ) Total liabilities 4 (312 ) (486 ) — (794 ) 4 (220 ) (172 ) — (388 ) Total net assets $ 6,074 $ 3,324 $ 1,088 $ 3,578 $ 14,064 $ 5,167 $ 3,355 $ 1,360 $ 3,578 $ 13,460 Exelon Generation As of December 31, 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) $ 639 $ — $ — $ — $ 639 $ 214 $ — $ — $ — $ 214 NDT fund investments Cash equivalents (b) 365 87 — — 452 365 87 — — 452 Equities 3,353 1,753 — 1,388 6,494 3,353 1,753 — 1,388 6,494 Fixed income Corporate debt — 1,469 257 — 1,726 — 1,469 257 — 1,726 U.S. Treasury and agencies 1,808 131 — — 1,939 1,808 131 — — 1,939 Foreign governments — 42 — — 42 — 42 — — 42 State and municipal debt — 90 — — 90 — 90 — — 90 Other (c) — 33 — 953 986 — 33 — 953 986 Fixed income subtotal 1,808 1,765 257 953 4,783 1,808 1,765 257 953 4,783 Private credit — — 254 508 762 — — 254 508 762 Private equity — — — 402 402 — — — 402 402 Real estate — — — 607 607 — — — 607 607 NDT fund investments subtotal (d) 5,526 3,605 511 3,858 13,500 5,526 3,605 511 3,858 13,500 Rabbi trust investments Cash equivalents 50 — — — 50 4 — — — 4 Mutual funds 81 — — — 81 25 — — — 25 Fixed income — 12 — — 12 — — — — — Life insurance contracts — 78 41 — 119 — 25 — — 25 Rabbi trust investments subtotal 131 90 41 — 262 29 25 — — 54 Commodity derivative assets Economic hedges 768 2,491 1,485 — 4,744 768 2,491 1,485 — 4,744 Proprietary trading — 37 60 — 97 — 37 60 — 97 Effect of netting and allocation of collateral (e)(f) (908 ) (2,162 ) (588 ) — (3,658 ) (908 ) (2,162 ) (588 ) — (3,658 ) Commodity derivative assets subtotal (140 ) 366 957 — 1,183 (140 ) 366 957 — 1,183 Total assets 6,156 4,061 1,509 3,858 15,584 5,629 3,996 1,468 3,858 14,951 Exelon Generation As of December 31, 2019 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 (1,071 ) (2,855 ) (1,228 ) — (5,154 ) (1,071 ) (2,855 ) (927 ) — (4,853 ) Proprietary trading — (34 ) (15 ) — (49 ) — (34 ) (15 ) — (49 ) Effect of netting and allocation of collateral (e)(f) 1,071 2,714 802 — 4,587 1,071 2,714 802 — 4,587 Commodity derivative liabilities subtotal — (175 ) (441 ) — (616 ) — (175 ) (140 ) — (315 ) Deferred compensation obligation — (147 ) — — (147 ) — (41 ) — — (41 ) Total liabilities — (322 ) (441 ) — (763 ) — (216 ) (140 ) — (356 ) Total net assets $ 6,156 $ 3,739 $ 1,068 $ 3,858 $ 14,821 $ 5,629 $ 3,780 $ 1,328 $ 3,858 $ 14,595 _________ (a) Exelon excludes cash of $483 million and $373 million at March 31, 2020 and December 31, 2019 , respectively, and restricted cash of $110 million at both March 31, 2020 and December 31, 2019 , and includes long-term restricted cash of $121 million and $177 million at March 31, 2020 and December 31, 2019 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Generation excludes cash of $317 million and $177 million at March 31, 2020 and December 31, 2019 , respectively, and restricted cash of $63 million and $58 million at March 31, 2020 and December 31, 2019 , respectively. (b) Includes $78 million and $90 million of cash received from outstanding repurchase agreements at March 31, 2020 and December 31, 2019 , 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 $2 million , which have total notional amounts of $826 million and $724 million at March 31, 2020 and December 31, 2019 , 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 $110 million and $147 million at March 31, 2020 and December 31, 2019 , 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 $126 million , $548 million and $215 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of March 31, 2020 . Collateral posted/(received) from counterparties, net of collateral paid to counterparties, totaled $163 million , $551 million and $214 million allocated to Level 1, Level 2 and Level 3 mark-to-market derivatives, respectively, as of December 31, 2019 . (f) Of the collateral posted/(received), $644 million and $511 million represents variation margin on the exchanges as of March 31, 2020 and December 31, 2019 , respectively. As of March 31, 2020 , Exelon and Generation have outstanding commitments to invest in fixed income, private credit, private equity and real estate investments of approximately $80 million , $131 million , $338 million , and $428 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 $76 million and $66 million as of March 31, 2020 , respectively. Changes in fair value, cumulative adjustments and impairments were not material for the three months ended March 31, 2020 . ComEd, PECO and BGE ComEd PECO BGE As of March 31, 2020 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) $ 729 $ — $ — $ 729 $ 8 $ — $ — $ 8 $ — $ — $ — $ — Rabbi trust investments Mutual funds — — — — 7 — — 7 8 — — 8 Life insurance contracts — — — — — 10 — 10 — — 1 1 Rabbi trust investments subtotal — — — — 7 10 — 17 8 — 1 9 Total assets 729 — — 729 15 10 — 25 8 — 1 9 Liabilities Deferred compensation obligation — (7 ) — (7 ) — (8 ) — (8 ) — (5 ) — (5 ) Mark-to-market derivative liabilities (b) — — (314 ) (314 ) — — — — — — — — Total liabilities — (7 ) (314 ) (321 ) — (8 ) — (8 ) — (5 ) — (5 ) Total net assets (liabilities) $ 729 $ (7 ) $ (314 ) $ 408 $ 15 $ 2 $ — $ 17 $ 8 $ (5 ) $ 1 $ 4 ComEd PECO BGE As of December 31, 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) $ 280 $ — $ — $ 280 $ 15 $ — $ — $ 15 $ — $ — $ — $ — Rabbi trust investments Mutual funds — — — — 8 — — 8 8 — — 8 Life insurance contracts — — — — — 11 — 11 — — — — Rabbi trust investments subtotal — — — — 8 11 — 19 8 — — 8 Total assets 280 — — 280 23 11 — 34 8 — — 8 Liabilities Deferred compensation obligation — (8 ) — (8 ) — (9 ) — (9 ) — (5 ) — (5 ) Mark-to-market derivative liabilities (b) — — (301 ) (301 ) — — — — — — — — Total liabilities — (8 ) (301 ) (309 ) — (9 ) — (9 ) — (5 ) — (5 ) Total net assets (liabilities) $ 280 $ (8 ) $ (301 ) $ (29 ) $ 23 $ 2 $ — $ 25 $ 8 $ (5 ) $ — $ 3 _________ (a) ComEd excludes cash of $67 million and $90 million at March 31, 2020 and December 31, 2019 , respectively, and restricted cash of $38 million and $33 million at March 31, 2020 and December 31, 2019 , respectively, and includes long-term restricted cash of $108 million and $163 million at March 31, 2020 and December 31, 2019 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. PECO excludes cash of $30 million and $12 million at March 31, 2020 and December 31, 2019 , respectively. BGE excludes cash of $11 million and $24 million at March 31, 2020 and December 31, 2019 , respectively, and restricted cash of $1 million at both March 31, 2020 and December 31, 2019 . (b) The Level 3 balance consists of the current and noncurrent liability of $36 million and $278 million , respectively, at March 31, 2020 , and $32 million and $269 million , respectively, at December 31, 2019 , related to floating-to-fixed energy swap contracts with unaffiliated suppliers. PHI, Pepco, DPL and ACE As of March 31, 2020 As of December 31, 2019 PHI Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Assets Cash equivalents (a) $ 63 $ — $ — $ 63 $ 124 $ — $ — $ 124 Rabbi trust investments Cash equivalents 44 — — 44 44 — — 44 Mutual funds 13 — — 13 14 — — 14 Fixed income — 11 — 11 — 12 — 12 Life insurance contracts — 25 42 67 — 24 41 65 Rabbi trust investments subtotal 57 36 42 135 58 36 41 135 Total assets 120 36 42 198 182 36 41 259 Liabilities Deferred compensation obligation — (16 ) — (16 ) — (19 ) — (19 ) Total liabilities — (16 ) — (16 ) — (19 ) — (19 ) Total net assets $ 120 $ 20 $ 42 $ 182 $ 182 $ 17 $ 41 $ 240 Pepco DPL ACE As of March 31, 2020 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 $ — $ — $ — $ — $ 15 $ — $ — $ 15 Rabbi trust investments Cash equivalents 44 — — 44 — — — — — — — — Fixed income — 1 — 1 — — — — — — — — Life insurance contracts — 25 42 67 — — — — — — — — Rabbi trust investments subtotal 44 26 42 112 — — — — — — — — Total assets 78 26 42 146 — — — — 15 — — 15 Liabilities Deferred compensation obligation — (2 ) — (2 ) — — — — — — — — Total liabilities — (2 ) — (2 ) — — — — — — — — Total net assets $ 78 $ 24 $ 42 $ 144 $ — $ — $ — $ — $ 15 $ — $ — $ 15 Pepco DPL ACE As of December 31, 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 $ — $ — $ — $ — $ 16 $ — $ — $ 16 Rabbi trust investments Cash equivalents 43 — — 43 — — — — — — — — Fixed income — 2 — 2 — — — — — — — — Life insurance contracts — 24 41 65 — — — — — — — — Rabbi trust investments subtotal 43 26 41 110 — — — — — — — — Total assets 77 26 41 144 — — — — 16 — — 16 Liabilities Deferred compensation obligation — (2 ) — (2 ) — — — — — — — — Total liabilities — (2 ) — (2 ) — — — — — — — — Total net assets (liabilities) $ 77 $ 24 $ 41 $ 142 $ — $ — $ — $ — $ 16 $ — $ — $ 16 _________ (a) PHI excludes cash of $35 million and $57 million at March 31, 2020 and December 31, 2019 , respectively, and includes long-term restricted cash of $12 million and $14 million at March 31, 2020 and December 31, 2019 , respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Pepco excludes cash of $17 million and $29 million at March 31, 2020 and December 31, 2019 , respectively. DPL excludes cash of $6 million and $13 million at March 31, 2020 and December 31, 2019 , respectively. ACE excludes cash of $8 million and $12 million at March 31, 2020 and December 31, 2019 , respectively, and includes long-term restricted cash of $12 million and $14 million at March 31, 2020 and December 31, 2019 , 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 months ended March 31, 2020 and 2019 : Exelon Generation ComEd PHI and Pepco Three Months Ended March 31, 2020 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, 2019 $ 1,068 $ 511 $ 817 $ 1,328 $ (301 ) $ 41 $ — Total realized / unrealized gains (losses) Included in net income 10 (1 ) 10 (a) 9 — 1 — Included in noncurrent payables to affiliates — (1 ) — (1 ) — — 1 Included in regulatory assets (14 ) — — — (13 ) (b) — (1 ) Change in collateral 1 — 1 1 — — — Purchases, sales, issuances and settlements Purchases 42 3 39 42 — — — Sales (22 ) — (22 ) (22 ) — — — Settlements (14 ) (14 ) — (14 ) — — — Transfers into Level 3 2 — 2 (c) 2 — — — Transfers out of Level 3 15 — 15 (c) 15 — — — Balance as of March 31, 2020 $ 1,088 $ 498 $ 862 $ 1,360 $ (314 ) $ 42 $ — The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of March 31, 2020 $ 187 $ (1 ) $ 187 $ 186 $ — $ 1 $ — Exelon Generation ComEd PHI and Pepco Three Months Ended March 31, 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 (228 ) 2 (231 ) (a) (229 ) — 1 — Included in noncurrent payables to affiliates — 11 — 11 — — (11 ) Included in regulatory assets 20 — — — 9 (b) — 11 Change in collateral 81 — 81 81 — — — Purchases, sales, issuances and settlements Purchases 58 1 57 58 — — — Sales — — — — — — — Settlements (17 ) (17 ) — (17 ) — — — Transfers into Level 3 — — — (c) — — — — Transfers out of Level 3 17 — 17 (c) 17 — — — Balance as of March 31, 2019 $ 838 $ 540 $ 499 $ 1,039 $ (240 ) $ 39 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of March 31, 2019 $ (148 ) $ 2 $ (151 ) $ (149 ) $ — $ 1 $ — __________ (a) Includes a reduction for the reclassification of $177 million and $80 million of realized losses due to the settlement of derivative contracts for the three months ended March 31, 2020 and 2019 , respectively. (b) Includes $23 million of decreases in fair value and an increase for realized losses due to settlements of $10 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 2020 . Includes $14 million of decreases in fair value and an increase for realized losses due to settlements of $5 million recorded in purchased power expense associated with floating-to-fixed energy swap contracts with unaffiliated suppliers for the three months ended March 31, 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.
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 months ended March 31, 2020 and 2019 : Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total realized gains (losses) for the three months ended March 31, 2020 $ 72 $ (62 ) $ 1 $ (1 ) $ 72 $ (62 ) $ (1 ) $ 1 Total unrealized gains (losses) for the three months ended March 31, 2020 205 (18 ) 1 (1 ) 205 (18 ) (1 ) 1 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 March 31, 2019 $ (128 ) $ (103 ) $ 1 $ 2 $ (128 ) $ (103 ) $ 2 $ 1 Total unrealized (losses) gains for the three months ended March 31, 2019 (91 ) (60 ) 1 2 (91 ) (60 ) 2 1
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 mark-to-market derivatives. Type of trade Fair Value at March 31, 2020 Fair Value at December 31, 2019 Valuation Technique Unobservable Input 2020 Range & Arithmetic Average 2019 Range & Arithmetic Average Mark-to-market derivatives — Economic Hedges (Exelon and Generation) (a)(b) $ 610 $ 558 Discounted Forward power $6 - $136 $27 $9 - $180 $29 Forward gas $1.02 - $8.10 $2.43 $0.83 - $10.72 $2.55 Option Volatility 8% - 304% 70% 8% - 236% 70% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(b) $ 37 $ 45 Discounted Forward power $15 - $136 $31 $25 - $180 $33 Mark-to-market derivatives (Exelon and ComEd) $ (314 ) $ (301 ) Discounted Forward heat (c) 9x - 10x 9.22x 9x - 10x 9.68x Marketability 3% - 7% 5.11% 3% - 7% 4.95% Renewable 90% - 122% 99% 91% - 123% 99% _________ (a) The valuation techniques, unobservable inputs, ranges and arithmetic averages are the same for the asset and liability positions. (b) The fair values do not include cash collateral posted on level three positions of $215 million and $214 million as of March 31, 2020 and December 31, 2019 , 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.

Commitments and Contingencies_2

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2020
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 March 31, 2020 : Description Exelon PHI Pepco DPL ACE Total commitments $ 513 $ 320 $ 120 $ 89 $ 111 Remaining commitments (a) 95 75 62 8 5 _________ (a) Remaining commitments extend through 2026 and include rate credits, energy efficiency programs and delivery system modernization.
Commercial Commitments	The Registrants’ commercial commitments as of March 31, 2020 , representing commitments potentially triggered by future events were as follow s: Expiration within Total 2020 2021 2022 2023 2024 2025 and beyond Exelon Letters of credit $ 1,464 $ 1,080 $ 384 $ — $ — $ — $ — Surety bonds (a) 849 698 151 — — — — Financing trust guarantees 378 — — — — — 378 Guaranteed lease residual values (b) 27 1 2 4 3 12 5 Total commercial commitments $ 2,718 $ 1,779 $ 537 $ 4 $ 3 $ 12 $ 383 Generation Letters of credit $ 1,449 $ 1,071 $ 378 $ — $ — $ — $ — Surety bonds (a) 685 591 94 — — — — Total commercial commitments $ 2,134 $ 1,662 $ 472 $ — $ — $ — $ — ComEd Letters of credit $ 7 $ 4 $ 3 $ — $ — $ — $ — Surety bonds (a) 15 11 4 — — — — Financing trust guarantees 200 — — — — — 200 Total commercial commitments $ 222 $ 15 $ 7 $ — $ — $ — $ 200 PECO Surety bonds (a) $ 9 $ 8 $ 1 $ — $ — $ — $ — Financing trust guarantees 178 — — — — — 178 Total commercial commitments $ 187 $ 8 $ 1 $ — $ — $ — $ 178 BGE Letters of credit $ 2 $ 2 $ — $ — $ — $ — $ — Surety bonds (a) 17 16 1 — — — — Total commercial commitments $ 19 $ 18 $ 1 $ — $ — $ — $ — PHI Surety bonds (a) $ 21 $ 20 $ 1 $ — $ — $ — $ — Guaranteed lease residual values (b) 27 1 2 4 3 12 5 Total commercial commitments $ 48 $ 21 $ 3 $ 4 $ 3 $ 12 $ 5 Pepco Surety bonds (a) $ 14 $ 14 $ — $ — $ — $ — $ — Guaranteed lease residual values (b) 9 — 1 1 1 4 2 Total commercial commitments $ 23 $ 14 $ 1 $ 1 $ 1 $ 4 $ 2 DPL Surety bonds (a) $ 4 $ 3 $ 1 $ — $ — $ — $ — Guaranteed lease residual values (b) 11 — 1 2 1 5 2 Total commercial commitments $ 15 $ 3 $ 2 $ 2 $ 1 $ 5 $ 2 ACE Surety bonds (a) $ 3 $ 3 $ — $ — $ — $ — $ — Guaranteed lease residual values (b) 7 1 — 1 1 3 1 Total commercial commitments $ 10 $ 4 $ — $ 1 $ 1 $ 3 $ 1 _________ (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 $72 million guaranteed by Exelon and PHI, of which $24 million , $30 million and $18 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 March 31, 2020 and December 31, 2019 , 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: March 31, 2020 December 31, 2019 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 $ 472 $ 317 $ 478 $ 320 Generation 104 — 105 — ComEd 301 300 304 303 PECO 19 17 19 17 BGE 2 — 2 — PHI 46 — 48 — Pepco 44 — 46 — DPL 1 — 1 — ACE 1 — 1 —

Changes in Accumulated Other _2

Changes in Accumulated Other Comprehensive Income (Tables)	3 Months Ended
	Mar. 31, 2020
Changes in Accumulated Other Comprehensive Income [Abstract]
Schedule of Changes in Accumulated Other Comprehensive Income (Loss)	The following tables present changes in Exelon's AOCI, net of tax, by component: Three Months Ended March 31, 2020 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Currency Items Total Beginning balance $ (2 ) $ (3,165 ) $ (27 ) $ (3,194 ) OCI before reclassifications (1 ) (7 ) (8 ) (16 ) Amounts reclassified from AOCI — 37 — 37 Net current-period OCI (1 ) 30 (8 ) 21 Ending balance $ (3 ) $ (3,135 ) $ (35 ) $ (3,173 ) Three Months Ended March 31, 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 — (38 ) 2 (1 ) (37 ) Amounts reclassified from AOCI — 20 — — 20 Net current-period OCI — (18 ) 2 (1 ) (17 ) Ending balance $ (2 ) $ (2,978 ) $ (31 ) $ (1 ) $ (3,012 ) _________ (a) AOCI amounts are included in the computation of net periodic pension and OPEB cost. See Note 10 — 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.
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 March 31, 2020 2019 Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 4 $ 6 Actuarial loss reclassified to periodic benefit cost (17 ) (13 ) Pension and non-pension postretirement benefit plans valuation adjustment 3 14

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	3 Months Ended
	Mar. 31, 2020
Variable Interest Entity [Abstract]
VIE - Assets and Liabilities of VIEs which Creditors or Beneficiaries have no Recourse	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 March 31, 2020 and December 31, 2019 . 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. March 31, 2020 December 31, 2019 Exelon Generation PHI (a) ACE Exelon Generation PHI (a) ACE Cash and cash equivalents $ 51 $ 51 $ — $ — $ 163 $ 163 $ — $ — Restricted cash and cash equivalents 84 81 3 3 88 85 3 3 Accounts receivable Customer 131 131 — — 151 151 — — Other 44 44 — — 39 39 — — Unamortized energy contract assets (b) 22 22 — — 23 23 — — Inventories, net Materials and supplies 231 231 — — 227 227 — — Other current assets 42 38 4 — 32 31 1 — Total current assets 605 598 7 3 723 719 4 3 Property, plant and equipment, net (c) 6,017 6,017 — — 6,022 6,022 — — Nuclear decommissioning trust funds 2,405 2,405 — — 2,741 2,741 — — Unamortized energy contract assets (b) 264 264 — — 250 250 — — Other noncurrent assets 71 56 15 12 89 73 16 14 Total noncurrent assets 8,757 8,742 15 12 9,102 9,086 16 14 Total assets $ 9,362 $ 9,340 $ 22 $ 15 $ 9,825 $ 9,805 $ 20 $ 17 Long-term debt due within one year $ 543 $ 519 $ 24 $ 20 $ 544 $ 523 $ 21 $ 20 Accounts payable 121 121 — — 106 106 — — Accrued expenses 46 46 — — 70 70 — — Unamortized energy contract liabilities 7 7 — — 8 8 — — Other current liabilities 3 3 — — 3 3 — — Total current liabilities 720 696 24 20 731 710 21 20 Long-term debt 502 483 19 16 527 504 23 21 Asset retirement obligations (d) 2,156 2,156 — — 2,128 2,128 — — Unamortized energy contract liabilities 1 1 — — 1 1 — — Other noncurrent liabilities 37 37 — — 89 89 — — Total noncurrent liabilities 2,696 2,677 19 16 2,745 2,722 23 21 Total liabilities $ 3,416 $ 3,373 $ 43 $ 36 $ 3,476 $ 3,432 $ 44 $ 41 _________ (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 $20 million as of March 31, 2020 and December 31, 2019 . (d) Exelon’s and Generation’s balances include liabilities with recourse of $4 million and $3 million as of March 31, 2020 and December 31, 2019 , respectively.
VIE - Summary of Unconsolidated VIEs	The following table presents summary information about Exelon's and Generation’s significant unconsolidated VIE entities: March 31, 2020 December 31, 2019 Commercial Agreement VIEs Equity Investment VIEs Total Commercial Agreement VIEs Equity Investment VIEs Total Total assets (a) $ 695 $ 431 $ 1,126 $ 636 $ 443 $ 1,079 Total liabilities (a) 158 223 381 33 227 260 Exelon's ownership interest in VIE (a) — 183 183 — 191 191 Other ownership interests in VIE (a) 538 25 563 604 25 629 _________ (a)

Supplemental Financial Inform_2

Supplemental Financial Information (Tables)	3 Months Ended
	Mar. 31, 2020
Supplemental Financial Information [Abstract]
Components of Operating Lease Income	The following tables provide additional information about material items recorded in the Registrants' Consolidated Statements of Operations and Comprehensive Income. Operating revenues Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended March 31, 2020 Operating lease income $ 5 $ 3 $ — $ — $ — $ 1 $ — $ 1 $ — Variable lease income 69 69 — — — — — — — Three Months Ended March 31, 2019 Operating lease income $ 4 $ 3 $ — $ — $ — $ 1 $ — $ 1 $ — Variable lease income 52 52 — — — — — — —
Taxes Other Than Income Taxes	Taxes other than income taxes Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended March 31, 2020 Utility taxes (a) $ 218 $ 26 $ 60 $ 31 $ 26 $ 75 $ 69 $ 6 $ — Property 150 69 7 4 39 31 21 9 1 Payroll 63 31 7 4 4 8 2 1 1 Three Months Ended March 31, 2019 Utility taxes (a) $ 223 $ 26 $ 62 $ 34 $ 27 $ 74 $ 69 $ 5 $ — Property 149 71 7 3 37 29 21 8 — Payroll 65 33 7 4 4 7 2 1 1 _________ (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 March 31, 2020 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 47 $ 47 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 82 82 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units (932 ) (932 ) — — — — — — — Non-regulatory agreement units (706 ) (706 ) — — — — — — — Regulatory offset to NDT fund-related activities (b) 709 709 — — — — — — — Decommissioning-related activities (800 ) (800 ) — — — — — — — AFUDC — Equity 23 — 6 3 5 9 6 1 2 Non-service net periodic benefit cost 10 — — — — — — — — Three Months Ended March 31, 2019 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 54 $ 54 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 54 54 — — — — — — — Net unrealized losses on NDT funds Regulatory agreement units 379 379 — — — — — — — Non-regulatory agreement units 280 280 — — — — — — — Regulatory offset to NDT fund-related activities (b) (348 ) (348 ) — — — — — — — Decommissioning-related activities 419 419 — — — — — — — AFUDC — Equity 22 — 5 3 5 9 6 1 2 Non-service net periodic benefit cost 5 — — — — — — — — _________ (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 9 — Asset Retirement Obligations of the Exelon 2019 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 Three Months Ended March 31, 2020 Property, plant and equipment (a) $ 856 $ 290 $ 228 $ 79 $ 97 $ 144 $ 64 $ 38 $ 34 Amortization of regulatory assets (a) 149 — 45 7 46 50 31 10 9 Amortization of intangible assets, net (a) 16 14 — — — — — — — Amortization of energy contract assets and liabilities (b) 2 2 — — — — — — — Nuclear fuel (c) 231 231 — — — — — — — ARO accretion (d) 124 124 — — — — — — — Total depreciation, amortization and accretion $ 1,378 $ 661 $ 273 $ 86 $ 143 $ 194 $ 95 $ 48 $ 43 Three Months Ended March 31, 2019 Property, plant and equipment (a) $ 917 $ 392 $ 219 $ 74 $ 85 $ 127 $ 58 $ 35 $ 25 Amortization of regulatory assets (a) 143 — 32 7 51 53 36 11 6 Amortization of intangible assets, net (a) 15 13 — — — — — — — Nuclear fuel (c) 261 261 — — — — — — — ARO accretion (d) 124 123 — — — — — — — Total depreciation, amortization and accretion $ 1,460 $ 789 $ 251 $ 81 $ 136 $ 180 $ 94 $ 46 $ 31 _________ (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 Three Months Ended March 31, 2020 Pension and non-pension postretirement benefit costs $ 98 $ 27 $ 28 $ 1 $ 15 $ 17 $ 3 $ 1 $ 3 Provision for uncollectible accounts 45 4 7 17 7 10 4 3 3 Other decommissioning-related activity (a) 128 128 — — — — — — — Energy-related options (b) 6 6 — — — — — — — Amortization of rate stabilization deferral (54 ) — — — (35 ) (19 ) (15 ) (4 ) — Discrete impacts from EIMA and FEJA (c) (17 ) — (17 ) — — — — — — Long-term incentive plan (7 ) — — — — — — — — Amortization of operating ROU asset 51 35 — — 8 5 2 2 1 Three Months Ended March 31, 2019 Pension and non-pension postretirement benefit costs $ 106 $ 31 $ 24 $ 2 $ 15 $ 23 $ 6 $ 4 $ 4 Provision for uncollectible accounts 43 — 9 16 8 10 4 4 2 Other decommissioning-related activity (a) (202 ) (202 ) — — — — — — — Energy-related options (b) 37 37 — — — — — — — Amortization of rate stabilization deferral (6 ) — — — — (6 ) (7 ) 1 — Discrete impacts from EIMA and FEJA (c) 28 — 28 — — — — — — Long-term incentive plan 25 — — — — — — — — Amortization of operating ROU asset 53 34 1 — 8 9 2 2 1 _______ (a) Includes the elimination of decommissioning-related activities 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 9 — Asset Retirement Obligations of the Exelon 2019 Form 10-K for additional information regarding the accounting for nuclear decommissioning. (b) Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations. (c) Reflects the change in ComEd's distribution and energy efficiency formula rates. See Note 2 — 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 March 31, 2020 Cash and cash equivalents $ 1,457 $ 821 $ 514 $ 31 $ 11 $ 49 $ 18 $ 7 $ 8 Restricted cash 414 150 211 7 1 37 33 — 3 Restricted cash included in other long-term assets 121 — 108 — — 12 — — 12 Total cash, cash equivalents and restricted cash $ 1,992 $ 971 $ 833 $ 38 $ 12 $ 98 $ 51 $ 7 $ 23 December 31, 2019 Cash and cash equivalents $ 587 $ 303 $ 90 $ 21 $ 24 $ 131 $ 30 $ 13 $ 12 Restricted cash 358 146 150 6 1 36 33 — 2 Restricted cash included in other long-term assets 177 — 163 — — 14 — — 14 Total cash, cash equivalents and restricted cash $ 1,122 $ 449 $ 403 $ 27 $ 25 $ 181 $ 63 $ 13 $ 28 March 31, 2019 Cash and cash equivalents $ 880 $ 537 $ 68 $ 41 $ 12 $ 33 $ 11 $ 7 $ 6 Restricted cash 223 139 17 6 4 39 35 1 3 Restricted cash included in other long-term assets 211 — 193 — — 19 — — 19 Total cash, cash equivalents and restricted cash $ 1,314 $ 676 $ 278 $ 47 $ 16 $ 91 $ 46 $ 8 $ 28 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 For additional information on restricted cash see Note 1 — Significant Accounting Policies of the Exelon 2019 Form 10-K.
Supplemental Balance Sheet Disclosures	The following tables provide additional information about material items recorded in the Registrants' Consolidated Balance Sheets. Accrued expenses Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE March 31, 2020 Compensation-related accruals (a) $ 557 $ 207 $ 87 $ 39 $ 44 $ 63 $ 22 $ 14 $ 10 Taxes accrued 442 244 85 1 43 114 79 25 7 Interest accrued 407 84 69 33 38 78 37 20 19 December 31, 2019 Compensation-related accruals (a) $ 1,052 $ 422 $ 171 $ 58 $ 78 $ 101 $ 28 $ 19 $ 15 Taxes accrued 414 222 83 3 26 117 90 14 8 Interest accrued 337 65 110 37 46 49 23 8 12 _________ (a) Primarily includes accrued payroll, bonuses and other incentives, vacation and benefits.

Related Party Transactions (Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2020
Related Party Transactions [Abstract]
Operating Revenues and Purchased Power and Fuel	The following table presents Generation’s Operating revenues from affiliates, which are primarily recorded as Purchased power from affiliates and an immaterial amount recorded as Operating and maintenance expense from affiliates at the Utility Registrants: Three Months Ended March 31, 2020 2019 Operating revenues from affiliates: ComEd (a)(b) $ 90 $ 94 PECO (c) 37 45 BGE (d) 99 76 PHI 103 101 Pepco (e) 79 70 DPL (f) 22 23 ACE (g) 2 8 Other 1 1 Total operating revenues from affiliates (Generation) $ 330 $ 317 __________ (a) Generation has an ICC-approved RFP contract with ComEd to provide a portion of ComEd’s electricity supply requirements. Generation also sells RECs and ZECs to ComEd. (b) For the three months ended March 31, 2020 , ComEd’s Purchased power from Generation of $97 million is recorded as Operating revenues from ComEd of $90 million and Purchased power and fuel from ComEd of $7 million at Generation. For the three months ended March 31, 2019 , ComEd’s Purchased power from Generation of $97 million is recorded as Operating revenues from ComEd of $94 million and Purchased power and fuel from ComEd of $3 million at Generation. (c) Generation provides electric supply to PECO under contracts executed through PECO’s competitive procurement process. In addition, Generation has a ten-year agreement with PECO to sell solar AECs. (d) Generation provides a portion of BGE’s energy requirements under its MDPSC-approved market-based SOS and gas commodity programs. (e) Generation provides electric supply to Pepco under contracts executed through Pepco's competitive procurement process approved by the MDPSC and DCPSC. (f) Generation provides a portion of DPL's energy requirements under its MDPSC and DPSC approved market based SOS and gas commodity programs. (g) Generation provides electric supply to ACE under contracts executed through ACE's competitive procurement process.
BSC and PHISCO Service Companies	The following table presents the service company costs allocated to the Registrants: Operating and maintenance from affiliates Capitalized costs Three Months Ended March 31, Three Months Ended March 31, 2020 2019 2020 2019 Exelon BSC $ 113 $ 99 PHISCO 14 22 Generation BSC $ 140 $ 149 11 11 ComEd BSC 72 62 42 25 PECO BSC 37 37 16 22 BGE BSC 41 38 28 21 PHI BSC 37 32 16 19 PHISCO — — 14 22 Pepco BSC 21 21 6 8 PHISCO 30 33 6 9 DPL BSC 13 13 5 5 PHISCO 24 26 4 7 ACE BSC 11 11 4 4 PHISCO 22 23 4 6
Current Receivables From/Payables To Affiliates	The following tables present current receivables from affiliates and current payables to affiliates: March 31, 2020 Receivables from affiliates: Payables to affiliates: Generation Comed PECO BGE DPL ACE BSC PHISCO Other Total Generation $ 17 $ — $ — $ 1 $ — $ 67 $ — $ 43 $ 128 ComEd $ 69 (a) — — — — 42 — 3 114 PECO 25 — — — — 19 — 7 51 BGE 22 — — — — 27 — 3 52 PHI — — — — — — 3 — 10 13 Pepco 29 — — 1 — — 11 12 2 55 DPL 1 — — — 3 7 9 1 21 ACE 12 — — — — 5 9 1 27 Other 9 1 — — — 1 — — 11 Total $ 167 $ 18 $ — $ 1 $ 1 $ 4 $ 181 $ 30 $ 70 $ 472 December 31, 2019 Receivables from affiliates: Payables to affiliates: Generation Comed PECO BGE DPL ACE BSC PHISCO Other Total Generation $ 27 $ — $ — $ — $ — $ 67 $ — $ 23 $ 117 ComEd $ 78 (a) — — — — 54 — 8 140 PECO 27 — — — — 25 — 3 55 BGE 28 — — — — 34 — 4 66 PHI — — — — — — 4 — 10 14 Pepco 34 — — — — — 16 15 1 66 DPL 7 — — — 3 10 11 1 32 ACE 7 — — — — 7 10 1 25 Other 9 1 1 1 — 1 — — 13 Total $ 190 $ 28 $ 1 $ 1 $ — $ 4 $ 217 $ 36 $ 51 $ 528 __________ (a) At March 31, 2020 and December 31, 2019 , Generation also had a contract liability with ComEd for $27 million and $37 million , respectively, that was included in Other liabilities on Generation’s Consolidated Balance Sheets. At March 31, 2020 and December 31, 2019 , ComEd had a Current Payable to Generation of $42 million and $41 million , respectively, on its Consolidated Balance Sheets, which consisted of Generation’s Current Receivable from ComEd, partially offset by Generation’s contract liability with ComEd.
Noncurrent Receivables from/Payables to affiliates	The following table presents noncurrent receivables from affiliates at ComEd and PECO which are recorded as noncurrent payables to affiliates at Generation: March 31, 2020 December 31, 2019 ComEd $ 2,040 $ 2,622 PECO 261 480 Other 1 1 Total: $ 2,302 $ 3,103
Long Term Debt to Financing Trusts	The following table presents Long-term debt to financing trusts: March 31, 2020 December 31, 2019 Exelon ComEd PECO Exelon ComEd PECO ComEd Financing III $ 206 $ 205 $ — $ 206 $ 205 $ — PECO Trust III 81 — 81 81 — 81 PECO Trust IV 103 — 103 103 — 103 Total $ 390 $ 205 $ 184 $ 390 $ 205 $ 184

Mergers, Acquisitions and Dis_2

Mergers, Acquisitions and Dispositions - Acquisitions Narrative (Details) $ in Millions	Apr. 04, 2018USD ($)
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	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2019
Oyster Creek [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
Operating Expense [Member] | Oyster Creek [Member]
Business Dispositions [Line Items]
Asset Retirement Obligation, Revision of Estimate		$ 9	$ 84

Regulatory Matters - Narrative

Regulatory Matters - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Maximum [Member] | One-Time Revenue Adjustment [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Amount of Impairment to Carrying Amount of Regulatory Assets	$ 81
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets	96
Increase (Decrease) in Regulatory Liabilities	(596)
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	51
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities	(207)
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	18
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
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
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
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
Energy Efficiency Costs [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities	16
Nuclear Decommissioning [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities	(582)
Nuclear Decommissioning [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities	(219)
Clean Energy Legislation [Member] | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Competitive businesses other revenues	18
Energy Efficiency Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets	45
Electric Distribution Formula Rate Annual Reconciliations [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets	22
Under Recovered Energy and Natural Gas Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets	$ 15

Regulatory Matters - Schedule o

Regulatory Matters - Schedule of Completed Rate Cases (Details) (Details) - Illinois 2019 Electric Distribution Base Rate Case [Member] - Commonwealth Edison Co [Member] - USD ($) $ in Millions	Dec. 04, 2019	Apr. 08, 2019
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)		$ (6)
Approved Revenue Requirement Increase (Decrease)	$ (17)
Public Utilities, Interim Rate Increase (Decrease), Amount	51
Public Utilities Requested Rate Increase (Decrease), Prior Year Annual Reconciliation	$ (68)
Public Utilities, Approved Equity Capital Structure, Percentage	6.51%
Approved Return on Equity, Percentage	8.91%
Basis points for ComEd's Revenue Requirement	580

Regulatory Matters - Schedule_2

Regulatory Matters - Schedule of Pending Rate Cases (Details) (Details) - USD ($) $ in Millions	Apr. 23, 2020	Apr. 16, 2020	Apr. 08, 2020	Mar. 17, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Illinois 2020 Electric Distribution Base Rate Case [Member] | Commonwealth Edison Co [Member] | Subsequent Event [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)		$ (11)
Public Utilities, Requested Rate Increase (Decrease), Initial Revenue Requirement, Amount		51
Public Utilities Requested Rate Increase (Decrease), Prior Year Annual Reconciliation		$ (62)
Requested Return on Equity, Percentage		8.38%
Requested Return on Distribution Rate Base, Percentage		6.28%
Basis points for ComEd's Revenue Requirement		580
District of Columbia 2019 Electric Distribution Base Rate Case [Member] | Potomac Electric Power Company [Member] | Subsequent Event [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended			$ 147
Requested Return on Equity, Percentage			10.30%
District of Columbia 2019 Electric Distribution Base Rate Case [Member] | Forecast [Member] | Potomac Electric Power Company [Member] | Subsequent Event [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended					$ 33	$ 37	$ 77
Maryland 2019 Electric Distribution Base Rate Case [Member] | Delmarva Power and Light Company [Member] | Subsequent Event [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended	$ 17
Requested Return on Equity, Percentage	10.30%
Delaware 2020 Gas Distribution Base Rate Case [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended				$ 9
Requested Return on Equity, Percentage				10.30%
Delaware 2020 Electric Distribution Base Rate Case [Member] | Delmarva Power and Light Company [Member] | Subsequent Event [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended		$ 24
Requested Return on Equity, Percentage		10.30%

Regulatory Matters - Capitalize

Regulatory Matters - Capitalized Ratemaking Amount Not Recognized (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Public Utilities, Amount of Allowance for Earnings on Equity Capitalized for Rate Making Purposes	$ 60	$ 63
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	2	3
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	51	53
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	7	7
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	4	4
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

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Change in Contract with Customer, Asset and Liability (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Change in Contract with Customer, Asset and Liability [Line Items]
Contract Assets	$ 172	$ 187	$ 174	$ 187
Contract Liabilities	29	25	33	27
Consideration (received) due, contract assets	(19)	(26)
Consideration received (due), contract liabilities	20	21
Revenues recognized, contract assets	17	26
Contract with Customer, Liability, Revenue Recognized	(24)	(23)
Contract with Customer, Performance Obligation Satisfied in Previous Period	9	5
Exelon Generation Co L L C [Member]
Change in Contract with Customer, Asset and Liability [Line Items]
Contract Assets	172	187	174	187
Contract Liabilities	56	39	$ 71	$ 42
Consideration (received) due, contract assets	(19)	(26)
Consideration received (due), contract liabilities	55	63
Revenues recognized, contract assets	17	26
Contract with Customer, Liability, Revenue Recognized	(70)	(66)
Contract with Customer, Performance Obligation Satisfied in Previous Period	$ 19	$ 5

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Performance Obligations (Details) $ in Millions	Mar. 31, 2020USD ($)
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	$ 273
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	144
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	64
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	45
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	198
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	724
Exelon Generation Co L L C [Member] | 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	330
Exelon Generation Co L L C [Member] | 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	200
Exelon Generation Co L L C [Member] | 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	79
Exelon Generation Co L L C [Member] | 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	45
Exelon Generation Co L L C [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	198
Exelon Generation Co L L C [Member] | 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	$ 852

Segment Information - Narrative

Segment Information - Narrative (Details)	3 Months Ended
	Mar. 31, 2020Reportable_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
		Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Revenues		$ 8,747	$ 9,477
Revenue from Related Parties		1	0
Depreciation and Amortization		1,021	1,075
Operating Expenses		7,529	8,262
Interest expense, net		410	403
Income (Loss) before income taxes		85	1,282
Income taxes		(294)	310
Net income (loss)		376	966
Capital expenditures		2,016	1,873
Assets	[1]	124,677		$ 124,977
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenues		4,733	5,296
Revenue from Related Parties		330	317
Income (Loss) before income taxes		(547)	652
Income taxes		(389)	224
Net income (loss)		(161)	422
Capital expenditures		558	511
Assets	[2]	47,882		48,995
Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		1,171	1,228
Revenue from Related Parties		3	3
Income (Loss) before income taxes		119	122
Income taxes		11	5
Net income (loss)		108	117
Capital expenditures		376	358
Assets	[3]	22,753		22,719
PECO Energy Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		37	45
Baltimore Gas And Electric Company Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		99	76
Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		90	94
Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		308	79
Revenues		8,747	9,477
Net income (loss)		376	966
Assets		124,677		124,977
Operating Segments [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		18	15
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		(1)	(1)
Revenues		(826)	(786)
Revenue from Related Parties		(824)	(785)
Depreciation and Amortization		0	0
Operating Expenses		(816)	(783)
Interest expense, net		0	0
Income (Loss) before income taxes		1	0
Income taxes		0	0
Net income (loss)		1	0
Capital expenditures		0	0
Assets		(9,765)		(10,089)
Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		(92)	(106)
Revenue from Related Parties		(93)	(106)
Depreciation and Amortization		(1)	(1)
Operating Expenses		(90)	(105)
Interest expense, net		(1)	(1)
Income (Loss) before income taxes		(110)	(118)
Income taxes		0	0
Net income (loss)		3	4
Capital expenditures		0	0
Assets		(6,152)		(5,810)
Exelon Generation Co L L C [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		309	80
Revenues		4,733	5,296
Depreciation and Amortization		304	405
Operating Expenses		4,400	4,963
Interest expense, net		109	111
Income (Loss) before income taxes		(547)	652
Income taxes		(389)	224
Net income (loss)		(161)	422
Capital expenditures		558	511
Assets		47,882		48,995
Exelon Generation Co L L C [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		330	317
Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0	0
Revenues		1,439	1,408
Depreciation and Amortization		273	251
Operating Expenses		1,151	1,135
Interest expense, net		94	87
Income (Loss) before income taxes		204	197
Income taxes		36	40
Net income (loss)		168	157
Capital expenditures		506	503
Assets		33,146		32,765
Commonwealth Edison Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		5	4
PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0	0
Revenues		813	900
Depreciation and Amortization		86	81
Operating Expenses		625	678
Interest expense, net		36	33
Income (Loss) before income taxes		155	193
Income taxes		15	25
Net income (loss)		140	168
Capital expenditures		259	222
Assets		11,535		11,469
PECO Energy Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		2	1
Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0	0
Revenues		937	976
Depreciation and Amortization		143	136
Operating Expenses		688	756
Interest expense, net		32	29
Income (Loss) before income taxes		222	196
Income taxes		41	36
Net income (loss)		181	160
Capital expenditures		283	258
Assets		10,789		10,634
Baltimore Gas and Electric Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		6	6
Pepco Holdings LLC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0	0
Revenues		1,171	1,228
Depreciation and Amortization		194	180
Operating Expenses		1,000	1,054
Interest expense, net		67	65
Income (Loss) before income taxes		119	122
Income taxes		11	5
Net income (loss)		108	117
Capital expenditures		376	358
Assets		22,753		22,719
Pepco Holdings LLC [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		3	4
Potomac Electric Power Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		544	575
Depreciation and Amortization		95	94
Operating Expenses		462	491
Interest expense, net		34	34
Income (Loss) before income taxes		57	57
Income taxes		5	2
Net income (loss)		52	55
Capital expenditures		180	144
Assets		8,837		8,661
Potomac Electric Power Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		1	2
Delmarva Power and Light Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		350	380
Depreciation and Amortization		48	46
Operating Expenses		284	308
Interest expense, net		16	15
Income (Loss) before income taxes		52	60
Income taxes		7	7
Net income (loss)		45	53
Capital expenditures		95	78
Assets		4,849		4,830
Delmarva Power and Light Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		2	2
Atlantic City Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		276	273
Depreciation and Amortization		43	31
Operating Expenses		251	252
Interest expense, net		15	14
Income (Loss) before income taxes		14	10
Income taxes		1	0
Net income (loss)		13	10
Capital expenditures		101	128
Assets		3,978		3,933
Atlantic City Electric Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		1	1
Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0	0
Revenues		480	455
Depreciation and Amortization		21	22
Operating Expenses		481	459
Interest expense, net		72	78
Income (Loss) before income taxes		(69)	(78)
Income taxes		(8)	(20)
Net income (loss)		(61)	(58)
Capital expenditures		34	21
Assets		8,337		8,484
Corporate and Other [Member] | Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		93	106
Depreciation and Amortization		9	10
Operating Expenses		93	108
Interest expense, net		3	3
Income (Loss) before income taxes		106	113
Income taxes		(2)	(4)
Net income (loss)		(5)	(5)
Capital expenditures		0	8
Assets		11,241		$ 11,105
Corporate and Other [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		479	453
Corporate and Other [Member] | Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		92	105
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues		1,174	1,256
Generation Mid Atlantic [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		1,168	1,262
Generation Mid Atlantic [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		6	(6)
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues		1,002	1,108
Generation Midwest [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues		1,008	1,114
Generation Midwest [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		(6)	(6)
Electricity, Generation [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		3,426	4,022
Electricity, Generation [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(326)	(315)
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		3,752	4,337
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
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
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
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
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
Oil and Gas, Purchased [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		669	878
Oil and Gas, Purchased [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(3)	(1)
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		672	879
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
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
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
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
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
Electricity, US Regulated | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,086	1,139
Electricity, US Regulated | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		3,748	3,831
Electricity, US Regulated | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(12)	(8)
Electricity, US Regulated | Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(2)	(5)
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
Electricity, US Regulated | Commonwealth Edison Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,439	1,408
Electricity, US Regulated | PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		604	620
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		613	658
Electricity, US Regulated | Pepco Holdings LLC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,104	1,153
Electricity, US Regulated | Potomac Electric Power Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		544	575
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		286	310
Electricity, US Regulated | Atlantic City Electric Company [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		276	273
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
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
Natural Gas, US Regulated | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		64	71
Natural Gas, US Regulated | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		595	665
Natural Gas, US Regulated | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(2)	(4)
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	1
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
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
Natural Gas, US Regulated | PECO Energy Co [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		209	280
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		324	318
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		64	71
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
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		64	70
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
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
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
Service, Other [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1	2
Service, Other [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(482)	(457)
Service, Other [Member] | Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(90)	(102)
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
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
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
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
Service, Other [Member] | Pepco Holdings LLC [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		3	4
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
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
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
Service, Other [Member] | Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		480	455
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		$ 93	$ 106
[1]	Exelon’s consolidated assets include $9,056 million and $9,532 million at March 31, 2020 and December 31, 2019 , respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,412 million and $3,473 million at March 31, 2020 and December 31, 2019 , respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 16 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $9,034 million and $9,512 million at March 31, 2020 and December 31, 2019 , respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,369 million and $3,429 million at March 31, 2020 and December 31, 2019 , respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 16 — Variable Interest Entities for additional information.
[3]	PHI’s consolidated total assets include $22 million and $20 million at March 31, 2020 and December 31, 2019 , respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $43 million and $44 million at March 31, 2020 and December 31, 2019 , respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 16 — Variable Interest Entities for additional information.

Segment Information - Generatio

Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Revenues	$ 8,747	$ 9,477
Revenue from Related Parties	1	0
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,174	1,256
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	1,002	1,108
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	314	393
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	190	212
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	1,072	1,353
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	3,752	4,322
Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	672	894
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	309	80
Unrealized Gain (Loss) on Securities	179	52
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,733	5,296
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenues	8,747	9,477
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,168	1,262
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	1,008	1,114
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	314	393
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	183	209
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	1,079	1,359
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	3,752	4,337
Operating Segments [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	672	879
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Unrealized Gain (Loss) on Securities	132	28
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,733	5,296
Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	309	80
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(826)	(786)
Revenue from Related Parties	(824)	(785)
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	6	(6)
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	(6)	(6)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	7	3
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	(7)	(6)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	(15)
Intersegment Eliminations [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	15
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,264	1,286
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	944	1,055
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	335	409
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	155	130
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	1,007	1,165
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	3,705	4,045
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	503	584
Revenue from Contract with Customer [Member] | Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,307	4,749
Revenue from Contract with Customer [Member] | Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	99	120
Other [Member] | Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	(96)	(24)
Other [Member] | Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	64	59
Other [Member] | Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	(21)	(16)
Other [Member] | Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	28	79
Other [Member] | Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	72	194
Other [Member] | Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	47	292
Other [Member] | Operating Segments [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	169	295
Other [Member] | Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	426	547
Other [Member] | Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	$ 210	$ (40)

Segment Information - Generat_2

Segment Information - Generation Total Revenues Net of Purchased Power and Fuel Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	$ 567	$ 683
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	727	771
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	193	265
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	80	74
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	158	156
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	1,725	1,949
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	304	142
Unrealized Gain (Loss) on Securities	179	52
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	2,029	2,091
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
RNF from external customers	559	679
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
RNF from external customers	732	769
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
RNF from external customers	189	262
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
RNF from external customers	76	98
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
RNF from external customers	177	174
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
RNF from external customers	1,733	1,982
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	296	109
Unrealized Gain (Loss) on Securities	132	28
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
RNF from external customers	2,029	2,091
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	8	4
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(5)	2
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	4	3
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	4	(24)
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(19)	(18)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(8)	(33)
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	8	33
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	$ 0	$ 0

Segment Information - Electric

Segment Information - Electric and Gas Revenue by Customer Class (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue, Major Customer [Line Items]
Revenues	$ 8,747	$ 9,477
Revenue from Related Parties	1	0
Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenues	8,747	9,477
Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenues	1,439	1,408
Revenue from Related Parties	5	4
Commonwealth Edison Co [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	12	(28)
Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,421	1,432
Commonwealth Edison Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	18	(24)
PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenues	813	900
Revenue from Related Parties	2	1
PECO Energy Co [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2	(3)
PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	807	902
PECO Energy Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	6	(2)
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	2	1
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	0	0
Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenues	937	976
Revenue from Related Parties		6
Baltimore Gas and Electric Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	36	10
Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	895	960
Baltimore Gas and Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	42	16
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	6	2
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	3	4
Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenues	1,171	1,228
Revenue from Related Parties	3	3
Pepco Holdings LLC [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	18	15
Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,150	1,208
Pepco Holdings LLC [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	21	20
Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenues	544	575
Revenue from Related Parties	1	2
Potomac Electric Power Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	15	14
Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	528	559
Potomac Electric Power Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	16	16
Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenues	350	380
Revenue from Related Parties	2	2
Delmarva Power and Light Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	0
Delmarva Power and Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	348	378
Delmarva Power and Light Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	2	2
Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenues	276	273
Revenue from Related Parties	1	1
Atlantic City Electric Company [Member] | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1	1
Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	274	271
Atlantic City Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	2	2
Electricity, US Regulated | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,748	3,831
Electricity, US Regulated | Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,422	1,432
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,421	1,432
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	4
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	701	710
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	362	360
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	134	132
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	13	13
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	211	217
Electricity, US Regulated | PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	600	622
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	599	622
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	3	1
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	382	409
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	99	96
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	53	48
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	7	7
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	58	62
Electricity, US Regulated | Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	595	652
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	595	652
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	3
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	339	385
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	67	70
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	103	110
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
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	79	80
Electricity, US Regulated | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,086	1,139
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,086	1,137
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	4
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	534	579
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	115	120
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	253	267
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	15	14
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	169	157
Electricity, US Regulated | Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	528	559
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	528	559
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	1	2
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	236	256
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	35	38
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	188	204
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	9	8
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	60	53
Electricity, US Regulated | Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	283	307
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	284	307
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	1	1
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	161	185
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	43	48
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	23	24
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
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	54	47
Electricity, US Regulated | Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	274	271
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	274	271
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	1	1
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	137	138
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	37	34
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	42	39
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
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	55	57
Natural Gas, US Regulated | Operating Segments [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	595	665
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
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
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
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
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
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
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
Natural Gas, US Regulated | PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	209	280
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	208	280
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	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	150	198
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	51	72
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	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	6	7
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	1	2
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	300	308
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	300	308
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	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	206	219
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	34	35
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	51	50
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
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	9	4
Natural Gas, US Regulated | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	64	71
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	64	71
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	1
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	40	44
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	17	19
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	1
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	4
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	3
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
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
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
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
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
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
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
Natural Gas, US Regulated | Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	64	71
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	64	71
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	1
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	40	44
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	17	19
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	1
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	4
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	3
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
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
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
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
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
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
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

Accounts Receivable - Unbilled

Accounts Receivable - Unbilled Customer Revenue (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	$ 1,225	$ 1,535
Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	698	807
Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	160	218
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	96	146
Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	134	170
Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	137	194
Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	75	100
Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	42	61
Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	$ 20	$ 33

Accounts Receivable - Allowance

Accounts Receivable - Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	$ (45)	$ (43)
Exelon Generation Co L L C [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(4)	0
Commonwealth Edison Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(7)	(9)
PECO Energy Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(17)	(16)
Baltimore Gas and Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(7)	(8)
Pepco Holdings LLC [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(10)	(10)
Potomac Electric Power Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(4)	(4)
Delmarva Power and Light Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(3)	(4)
Atlantic City Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses	(3)	$ (2)
Customer accounts receivable
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	243
Current Period Provision for Expected Credit Losses	55
Writeoffs, net of recoveries	(20)
Ending balance	278
Customer accounts receivable | Exelon Generation Co L L C [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	80
Current Period Provision for Expected Credit Losses	4
Writeoffs, net of recoveries	(3)
Ending balance	81
Customer accounts receivable | Commonwealth Edison Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	59
Current Period Provision for Expected Credit Losses	18
Writeoffs, net of recoveries	(6)
Ending balance	71
Customer accounts receivable | PECO Energy Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	55
Current Period Provision for Expected Credit Losses	18
Writeoffs, net of recoveries	(7)
Ending balance	66
Customer accounts receivable | Baltimore Gas and Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	12
Current Period Provision for Expected Credit Losses	8
Writeoffs, net of recoveries	(2)
Ending balance	18
Customer accounts receivable | Pepco Holdings LLC [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	37
Current Period Provision for Expected Credit Losses	7
Writeoffs, net of recoveries	(2)
Ending balance	42
Customer accounts receivable | Potomac Electric Power Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	13
Current Period Provision for Expected Credit Losses	3
Writeoffs, net of recoveries	(1)
Ending balance	15
Customer accounts receivable | Delmarva Power and Light Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	11
Current Period Provision for Expected Credit Losses	2
Writeoffs, net of recoveries	0
Ending balance	13
Customer accounts receivable | Atlantic City Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	13
Current Period Provision for Expected Credit Losses	2
Writeoffs, net of recoveries	(1)
Ending balance	14
Other receivables
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	48
Current Period Provision for Expected Credit Losses	8
Writeoffs, net of recoveries	(4)
Ending balance	52
Other receivables | Exelon Generation Co L L C [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	0
Current Period Provision for Expected Credit Losses	0
Writeoffs, net of recoveries	0
Ending balance	0
Other receivables | Commonwealth Edison Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	20
Current Period Provision for Expected Credit Losses	3
Writeoffs, net of recoveries	(1)
Ending balance	22
Other receivables | PECO Energy Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	7
Current Period Provision for Expected Credit Losses	1
Writeoffs, net of recoveries	(1)
Ending balance	7
Other receivables | Baltimore Gas and Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	5
Current Period Provision for Expected Credit Losses	2
Writeoffs, net of recoveries	(2)
Ending balance	5
Other receivables | Pepco Holdings LLC [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	16
Current Period Provision for Expected Credit Losses	2
Writeoffs, net of recoveries	0
Ending balance	18
Other receivables | Potomac Electric Power Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	7
Current Period Provision for Expected Credit Losses	1
Writeoffs, net of recoveries	0
Ending balance	8
Other receivables | Delmarva Power and Light Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	4
Current Period Provision for Expected Credit Losses	0
Writeoffs, net of recoveries	0
Ending balance	4
Other receivables | Atlantic City Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	5
Current Period Provision for Expected Credit Losses	1
Writeoffs, net of recoveries	0
Ending balance	$ 6

Accounts Receivable - Purchases

Accounts Receivable - Purchases and Sales of Accounts Receivable (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase	$ 781
Accounts Receivable, Sale	507
Exelon Generation Co L L C [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase	0
Accounts Receivable, Sale	749
Commonwealth Edison Co [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase	280
Accounts Receivable, Sale	0
PECO Energy Co [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase	284
Accounts Receivable, Sale	0
Baltimore Gas and Electric Company [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase	195
Accounts Receivable, Sale	0
Pepco Holdings LLC [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase	264
Accounts Receivable, Sale	0
Potomac Electric Power Company [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase	165
Accounts Receivable, Sale	0
Delmarva Power and Light Company [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase	53
Accounts Receivable, Sale	0
Atlantic City Electric Company [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase	46
Accounts Receivable, Sale	0
Exelon Generation Co LLC Affiliate [Member] | Commonwealth Edison Co [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase	34
Exelon Generation Co LLC Affiliate [Member] | PECO Energy Co [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase	67
Exelon Generation Co LLC Affiliate [Member] | Baltimore Gas and Electric Company [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase	69
Exelon Generation Co LLC Affiliate [Member] | Pepco Holdings LLC [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase	72
Exelon Generation Co LLC Affiliate [Member] | Potomac Electric Power Company [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase	51
Exelon Generation Co LLC Affiliate [Member] | Delmarva Power and Light Company [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase	13
Exelon Generation Co LLC Affiliate [Member] | Atlantic City Electric Company [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Related Parties, Purchase	8
Exelon Utility Registrants Affiliates [Member] | Exelon Generation Co L L C [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Related Parties, Sale	$ 242

Early Plant Retirements - Narra

Early Plant Retirements - Narrative (Details)	Mar. 31, 2020
Salem [Member] | Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Ownership interest	42.59%

Early Plant Retirements - Preta

Early Plant Retirements - Pretax Expense (Details) - Facility Closing [Member] - Three Mile Island [Member] $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Accelerated depreciation	$ 74
Accelerated nuclear fuel amortization	5
Operating and maintenance	(83)
Restructuring and Related Cost, Incurred Cost	(4)
Exelon Generation Co L L C [Member]
Accelerated depreciation	74
Accelerated nuclear fuel amortization	5
Operating and maintenance	(83)
Restructuring and Related Cost, Incurred Cost	$ (4)

Early Plant Retirements - Impli

Early Plant Retirements - Implications of Potential Early Plant Retirement on Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	$ 1,463	$ 1,456
Property, plant and equipment, net	81,017	80,233
Dresden [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	68
Nuclear fuel inventory, net	204
Property, plant and equipment, net	1,084
Construction work in progress	16
Asset retirement obligation	(1,301)
Byron [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	68
Nuclear fuel inventory, net	172
Property, plant and equipment, net	1,343
Construction work in progress	22
Asset retirement obligation	(596)
Braidwood [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	81
Nuclear fuel inventory, net	203
Property, plant and equipment, net	1,390
Construction work in progress	32
Asset retirement obligation	(554)
Dresden Byron Braidwood [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	217
Nuclear fuel inventory, net	579
Property, plant and equipment, net	3,817
Construction work in progress	70
Asset retirement obligation	(2,451)
Mystic Generating Station [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory	32
Fuel inventory	12
Property, plant and equipment, net	902
Asset retirement obligation	(3)
Exelon Generation Co L L C [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	1,038	1,026
Property, plant and equipment, net	24,169	$ 24,193
Exelon Generation Co L L C [Member] | Dresden [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	68
Nuclear fuel inventory, net	204
Property, plant and equipment, net	1,084
Construction work in progress	16
Asset retirement obligation	(1,301)
Exelon Generation Co L L C [Member] | Byron [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	68
Nuclear fuel inventory, net	172
Property, plant and equipment, net	1,343
Construction work in progress	22
Asset retirement obligation	(596)
Exelon Generation Co L L C [Member] | Braidwood [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	81
Nuclear fuel inventory, net	203
Property, plant and equipment, net	1,390
Construction work in progress	32
Asset retirement obligation	(554)
Exelon Generation Co L L C [Member] | Dresden Byron Braidwood [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	217
Nuclear fuel inventory, net	579
Property, plant and equipment, net	3,817
Construction work in progress	70
Asset retirement obligation	(2,451)
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	32
Fuel inventory	12
Property, plant and equipment, net	902
Asset retirement obligation	$ (3)

Nuclear Decommissioning - Narra

Nuclear Decommissioning - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	$ 11,611	$ 13,190
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	11,611	13,190
Assets, Total [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	11,824	13,353
Assets, Total [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	11,824	13,353
Other Current Assets [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	213	163
Other Current Assets [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Decommissioning Fund Investments	$ 213	$ 163

Nuclear Decommissioning - Rollf

Nuclear Decommissioning - Rollforward of Nuclear Decommissioning ARO (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Accretion expense	$ 124	$ 124
Nuclear Decommissioning [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance	10,504
Accretion expense	121
Costs incurred related to decommissioning plants	(20)
ARO ending balance	10,605
Current portion of ARO	107		$ 112
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Accretion expense	124	$ 123
Exelon Generation Co L L C [Member] | Nuclear Decommissioning [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance	10,504
Accretion expense	121
Costs incurred related to decommissioning plants	(20)
ARO ending balance	10,605
Current portion of ARO	$ 107		$ 112

Asset Impairments - Narrative (

Asset Impairments - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)MW	Mar. 31, 2019USD ($)
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	$ 8	$ 7
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	8	$ 7
Antelope Valley [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	717
Impairment of Long-Lived Assets Held-for-use	$ 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	$ 717
Impairment of Long-Lived Assets Held-for-use	0
ExGen Renewables IV, LLC [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	1,865
ExGen Renewables IV, LLC [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Long-lived assets	$ 1,865

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	Jun. 05, 2019	Mar. 31, 2020	Mar. 31, 2019
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		(345.90%)	24.20%
Decrease in Unrecognized Tax Benefits is Reasonably Possible		$ 411
Tax Adjustments, Settlements, and Unusual Provisions		76
Income Tax Expense (Benefit)		$ (294)	$ 310
Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		71.10%	34.30%
Decrease in Unrecognized Tax Benefits is Reasonably Possible		$ 411
Tax Adjustments, Settlements, and Unusual Provisions		73
Income Tax Expense (Benefit)		$ (389)	$ 224
Commonwealth Edison Co [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		17.60%	20.30%
Income Tax Expense (Benefit)		$ 36	$ 40
PECO Energy Co [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		9.70%	13.00%
Income Tax Expense (Benefit)		$ 15	$ 25
Baltimore Gas and Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		18.50%	18.40%
Income Tax Expense (Benefit)		$ 41	$ 36
Pepco Holdings LLC [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		9.20%	4.10%
Income Tax Expense (Benefit)		$ 11	$ 5
Potomac Electric Power Company [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		8.80%	3.50%
Income Tax Expense (Benefit)		$ 5	$ 2
Delmarva Power and Light Company [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		13.50%	11.70%
Income Tax Expense (Benefit)		$ 7	$ 7
Atlantic City Electric Company [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		7.10%	0.00%
Income Tax Expense (Benefit)		$ 1	$ 0
Internal Revenue Service (IRS) [Member]
Income Tax Additional Narrative Information [Line Items]
Income Tax Expense (Benefit)		(67)
Internal Revenue Service (IRS) [Member] | Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Income Tax Expense (Benefit)		$ (67)
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
	Mar. 31, 2020	Mar. 31, 2019
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	34.00%	3.90%
Qualified nuclear decommissioning trust fund income	(235.80%)	7.20%
Amortization of investment tax credit, including deferred taxes on basis difference	(4.50%)	(0.50%)
Plant basis differences	(23.00%)	(1.40%)
Production tax credits and other credits	(9.90%)	(0.80%)
Noncontrolling interests	10.60%	(0.60%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	(79.10%)
Excess deferred tax amortization	(71.70%)	(4.70%)
Other	12.50%	0.10%
Effective income tax rate	(345.90%)	24.20%
Exelon Generation Co L L C [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	0.70%	3.10%
Qualified nuclear decommissioning trust fund income	36.40%	14.20%
Amortization of investment tax credit, including deferred taxes on basis difference	0.50%	(0.90%)
Plant basis differences	0.00%	0.00%
Production tax credits and other credits	1.30%	(1.50%)
Noncontrolling interests	(1.60%)	(1.10%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	12.20%
Excess deferred tax amortization	0.00%	0.00%
Other	0.60%	(0.50%)
Effective income tax rate	71.10%	34.30%
Commonwealth Edison Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	8.30%	8.20%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.20%)
Plant basis differences	(1.10%)	(0.50%)
Production tax credits and other credits	(0.20%)	0.00%
Noncontrolling interests	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%
Excess deferred tax amortization	(10.50%)	(8.50%)
Other	0.30%	0.30%
Effective income tax rate	17.60%	20.30%
PECO Energy Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	0.10%	1.00%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	0.00%	0.00%
Plant basis differences	(8.40%)	(6.70%)
Production tax credits and other credits	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%
Excess deferred tax amortization	(3.00%)	(2.50%)
Other	0.00%	0.20%
Effective income tax rate	9.70%	13.00%
Baltimore Gas and Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	5.70%	6.30%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.10%)
Plant basis differences	(1.20%)	(0.90%)
Production tax credits and other credits	(0.20%)	0.00%
Noncontrolling interests	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%
Excess deferred tax amortization	(7.30%)	(7.90%)
Other	0.60%	0.00%
Effective income tax rate	18.50%	18.40%
Pepco Holdings LLC [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	5.80%	4.70%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.20%)
Plant basis differences	(1.40%)	(1.70%)
Production tax credits and other credits	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%
Excess deferred tax amortization	(15.50%)	(19.40%)
Other	(0.60%)	(0.30%)
Effective income tax rate	9.20%	4.10%
Potomac Electric Power Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	4.70%	2.10%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	0.00%	(0.10%)
Plant basis differences	(2.10%)	(2.00%)
Production tax credits and other credits	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%
Excess deferred tax amortization	(14.20%)	(17.90%)
Other	(0.60%)	0.40%
Effective income tax rate	8.80%	3.50%
Delmarva Power and Light Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.60%	6.50%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.20%)
Plant basis differences	(0.70%)	(0.70%)
Production tax credits and other credits	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%
Excess deferred tax amortization	(12.70%)	(15.60%)
Other	(0.50%)	0.70%
Effective income tax rate	13.50%	11.70%
Atlantic City Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.70%	6.70%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.30%)
Plant basis differences	(0.80%)	(2.30%)
Production tax credits and other credits	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%
Excess deferred tax amortization	(18.80%)	(23.90%)
Other	(0.80%)	(1.20%)
Effective income tax rate	7.10%	0.00%

Income Taxes - Accounting for U

Income Taxes - Accounting for Uncertainty in Income Taxes (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 98	$ 507
Exelon Generation Co L L C [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	32	441
Commonwealth Edison Co [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	0	0
PECO Energy Co [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	0	0
Baltimore Gas and Electric Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	0	0
Pepco Holdings LLC [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	49	48
Potomac Electric Power Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	0	0
Delmarva Power and Light Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	0	0
Atlantic City Electric Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 14	$ 14

Income Taxes - Settlement of In

Income Taxes - Settlement of Income Tax Audits, Refund Claims, and Litigation (Details) $ in Millions	Mar. 31, 2020USD ($)
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	$ 14
State and Local Jurisdiction [Member] | Exelon Generation Co L L C [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	0
State and Local Jurisdiction [Member] | Commonwealth Edison Co [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	0
State and Local Jurisdiction [Member] | PECO Energy Co [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	0
State and Local Jurisdiction [Member] | Baltimore Gas and Electric Company [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	0
State and Local Jurisdiction [Member] | Pepco Holdings LLC [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	14
State and Local Jurisdiction [Member] | Potomac Electric Power Company [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	0
State and Local Jurisdiction [Member] | Delmarva Power and Light Company [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	0
State and Local Jurisdiction [Member] | Atlantic City Electric Company [Member]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	$ 14

Retirement Benefits - Narrative

Retirement Benefits - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Defined Benefit Plan Disclosure [Line Items]
Increase (Decrease) in Obligation, Pension Benefits	$ 8
Increase (Decrease) in Obligation, Other Postretirement Benefits	31
Accumulated Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Tax	(7)
Defined Benefit Plan Amounts Recognized In Regulatory Assets Before Tax	19
Defined Benefit Plan Amounts Recognized In Regulatory Liabilities Before Tax	$ (10)
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on assets	7.00%
Discount rate	3.34%
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on assets	6.69%
Discount rate	3.31%

Retirement Benefits - Calculati

Retirement Benefits - Calculation of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Amortization of:
Net periodic benefit cost	$ (10)	$ (5)
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	97	89
Interest cost	189	221
Expected return on assets	(318)	(307)
Amortization of:
Prior service cost (benefit)	1	0
Actuarial loss	128	104
Net periodic benefit cost	97	107
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	23	24
Interest cost	38	47
Expected return on assets	(41)	(38)
Amortization of:
Prior service cost (benefit)	(31)	(45)
Actuarial loss	12	11
Net periodic benefit cost	$ 1	$ (1)

Retirement Benefits - Allocated

Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	$ 98	$ 106
Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	98	106
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	27	31
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)	27	31
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	28	24
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)	28	24
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	1	2
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)	1	2
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	15	15
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	16
Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	17	23
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)	17	23
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	3	6
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)	3	6
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	1	4
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)	1	4
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	3	4
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)	$ 3	$ 4

Retirement Benefits - Defined C

Retirement Benefits - Defined Contribution Savings Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	$ 33	$ 31
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	13	13
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	7	7
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	3	2
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	2	2
Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	3	4
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	1	1
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	1	1
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	$ 0	$ 1

Derivative Financial Instrume_3

Derivative Financial Instruments - Narrative (Details) MWh in Millions, $ in Millions	1 Months Ended	3 Months Ended
	Jun. 30, 2012MWh	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		$ 1,468	$ 1,509
Derivative, Collateral, Right to Reclaim Cash		977	982
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		1,468	1,509
Derivative, Collateral, Right to Reclaim Cash		977	982
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		12
Derivative, Collateral, Right to Reclaim Cash		0
Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		34
Derivative, Collateral, Right to Reclaim Cash		0
PECO Energy Co [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		33
Derivative, Collateral, Right to Reclaim Cash		$ 0
Minimum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months		89.00%
Expected Generation Hedged In Year Two		70.00%
Maximum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months		92.00%
Expected Generation Hedged In Year Two		73.00%
Not Designated as Hedging Instrument, Economic Hedge [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount		$ 1,268	1,269
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		568	569
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		$ 144	$ 231

Derivative Financial Instrume_4

Derivative Financial Instruments - Summary of Derivative Fair Value Balances (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Mark-to-market derivative assets, current	$ 656	$ 679
Derivative Asset, Noncurrent	625	508
Mark-to-market derivative liabilities, current	(264)	(247)
Mark-to-market derivative liabilities, noncurrent	(436)	(393)
Margin Deposit Assets	644	511
Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	649	675
Derivative Asset, Noncurrent	625	508
Total mark-to-market derivative assets	1,274	1,183
Mark-to-market derivative liabilities, current	(252)	(236)
Mark-to-market derivative liabilities, noncurrent	(416)	(380)
Total mark-to-market derivative liabilities	(668)	(616)
Total mark-to-market derivative net assets (liabilities)	606	567
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	650	675
Derivative Asset, Noncurrent	625	508
Mark-to-market derivative liabilities, current	(229)	(215)
Mark-to-market derivative liabilities, noncurrent	(158)	(123)
Margin Deposit Assets	644	511
Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	649	675
Derivative Asset, Noncurrent	625	508
Total mark-to-market derivative assets	1,274	1,183
Mark-to-market derivative liabilities, current	(216)	(204)
Mark-to-market derivative liabilities, noncurrent	(138)	(111)
Total mark-to-market derivative liabilities	(354)	(315)
Total mark-to-market derivative net assets (liabilities)	920	868
Commonwealth Edison Co [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities, current	(36)	(32)
Mark-to-market derivative liabilities, noncurrent	(278)	(269)
Collateral [Member] | Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	277	287
Derivative Asset, Noncurrent	112	122
Total mark-to-market derivative assets	389	409
Mark-to-market derivative liabilities, current	339	357
Mark-to-market derivative liabilities, noncurrent	161	163
Total mark-to-market derivative liabilities	500	520
Total mark-to-market derivative net assets (liabilities)	889	929
Netting [Member] | Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	(3,701)	(3,190)
Derivative Asset, Noncurrent	(1,388)	(877)
Total mark-to-market derivative assets	(5,089)	(4,067)
Mark-to-market derivative liabilities, current	3,701	3,190
Mark-to-market derivative liabilities, noncurrent	1,388	877
Total mark-to-market derivative liabilities	5,089	4,067
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 derivative assets, current	4,010	3,506
Derivative Asset, Noncurrent	1,878	1,238
Total mark-to-market derivative assets	5,888	4,744
Mark-to-market derivative liabilities, current	(4,219)	(3,713)
Mark-to-market derivative liabilities, noncurrent	(1,676)	(1,140)
Total mark-to-market derivative liabilities	(5,895)	(4,853)
Total mark-to-market derivative net assets (liabilities)	(7)	(109)
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commonwealth Edison Co [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	0	0
Derivative Asset, Noncurrent	0	0
Total mark-to-market derivative assets	0	0
Mark-to-market derivative liabilities, current	(36)	(32)
Mark-to-market derivative liabilities, noncurrent	(278)	(269)
Total mark-to-market derivative liabilities	(314)	(301)
Total mark-to-market derivative net assets (liabilities)	(314)	(301)
Not Designated as Hedging Instrument [Member] | Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	63	72
Derivative Asset, Noncurrent	23	25
Total mark-to-market derivative assets	86	97
Mark-to-market derivative liabilities, current	(37)	(38)
Mark-to-market derivative liabilities, noncurrent	(11)	(11)
Total mark-to-market derivative liabilities	(48)	(49)
Total mark-to-market derivative net assets (liabilities)	$ 38	$ 48

Derivative Financial Instrume_5

Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 132	$ (31)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	127	(33)
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	128	(20)
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	128	(20)
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	175	(50)
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	175	(50)
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Purchased Power And Fuel [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	(47)	30
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	$ (47)	$ 30

Derivative Financial Instrume_6

Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) $ in Millions	Mar. 31, 2020USD ($)
Derivative [Line Items]
Cash Collateral Held	$ 29
Letters Of Credit Held	65
Exelon Generation Co L L C [Member] | Total Exposure Before Credit Collateral [Member]
Derivative [Line Items]
Investment grade	915
Non-investment grade	60
Internally rated - investment grade	228
Internally rated - non-investment grade	157
Total	1,360
Exelon Generation Co L L C [Member] | Credit Collateral [Member]
Derivative [Line Items]
Investment grade	22
Non-investment grade	49
Internally rated - investment grade	1
Internally rated - non-investment grade	22
Total	94
Exelon Generation Co L L C [Member] | Net Exposure [Member]
Derivative [Line Items]
Investment grade	893
Non-investment grade	11
Internally rated - investment grade	227
Internally rated - non-investment grade	135
Total	1,266
Financial institutions	18
Investor-owned utilities, marketers and power producers	983
Energy Cooperatives And Municipalities	224
Other	41
Exelon Generation Co L L C [Member] | Number Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Investment grade	0
Total	0
Exelon Generation Co L L C [Member] | Net Exposure Of Counterparties Greater Than Ten Percent Of Net Exposure [Member]
Derivative [Line Items]
Investment grade	0
Total	$ 0

Derivative Financial Instrume_7

Derivative Financial Instruments - Summary of Credit Risk Related Contingent Features (Details) - Exelon Generation Co L L C [Member] - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Liability	$ (1,002)	$ (956)
Offsetting Fair Value of In-the-Money Contracts Under Master Netting Agreements	699	649
Derivative liabilities, fair value	$ 303	$ 307

Derivative Financial Instrume_8

Derivative Financial Instruments Derivative Financial Instruments - Summary of Cash Collateral and Letters of Credit (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 977	$ 982
Derivative, Collateral, Right to Reclaim Securities	256	264
Derivative, Collateral, Obligation to Return Cash	105	103
Derivative, Collateral, Obligation to Return Securities	115	112
Incremental Collateral For Loss Of Investment Grade Credit Rating	1,468	1,509
Exelon Generation Co L L C [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Collateral, Right to Reclaim Cash	977	982
Derivative, Collateral, Right to Reclaim Securities	256	264
Derivative, Collateral, Obligation to Return Cash	105	103
Derivative, Collateral, Obligation to Return Securities	115	112
Incremental Collateral For Loss Of Investment Grade Credit Rating	$ 1,468	$ 1,509

Debt and Credit Agreements - Na

Debt and Credit Agreements - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Sep. 30, 2015
Parent Company [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 900
Parent Company [Member] | Corporate, Non-Segment [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 550
Short-term Bank Loans and Notes Payable	500
Note405Mar2030 [Member] [Domain] | Parent Company [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 1,250
Interest Rate	4.05%
Note470Mar2050 [Member] | Parent Company [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 750
Interest Rate	4.70%
Short-term Debt [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	$ 200
DOE Project Financing, 2.82% January 5, 2037 [Member] | Non Recourse Debt [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	37
Long-term Line of Credit	646
Non-Recourse Debt	479
DOE Project Financing, 2.82% January 5, 2037 [Member] | Exelon Generation Co L L C [Member] | Non Recourse Debt [Member]
Debt Instrument [Line Items]
Letters of Credit Outstanding, Amount	37
Long-term Line of Credit	646
Non-Recourse Debt	479
ExGenRenewablesIVNov2024 [Member] | Non Recourse Debt [Member]
Debt Instrument [Line Items]
Non-Recourse Debt	796
Long-term Debt	850
ExGenRenewablesIVNov2024 [Member] | Exelon Generation Co L L C [Member] | Non Recourse Debt [Member]
Debt Instrument [Line Items]
Non-Recourse Debt	796
Long-term Debt	850
ShortTermDebt300 [Member] [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Short-term Bank Loans and Notes Payable	$ 300
London Interbank Offered Rate (LIBOR) [Member] | Corporate, Non-Segment [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.65%
Line of Credit Facility, Interest Rate Description	LIBOR plus 1.75%
London Interbank Offered Rate (LIBOR) [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.75%
London Interbank Offered Rate (LIBOR) 1 [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.50%
Revolving Credit Facility [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,500
Letters of Credit Outstanding, Amount	$ 2,400

Debt and Credit Agreements - Co

Debt and Credit Agreements - Commercial Paper Borrowings (Details) - Commercial Paper [Member] - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 979	$ 870
Average Interest Rate on Commercial Paper Borrowings	2.91%	2.25%
Parent Company [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 135	$ 136
Average Interest Rate on Commercial Paper Borrowings	4.20%	1.92%
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 595	$ 320
Average Interest Rate on Commercial Paper Borrowings	2.01%	1.84%
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 0	$ 130
Average Interest Rate on Commercial Paper Borrowings	0.00%	2.38%
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	$ 141	$ 76
Average Interest Rate on Commercial Paper Borrowings	4.45%	2.46%
Pepco Holdings LLC [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 108	$ 208
Average Interest Rate on Commercial Paper Borrowings	4.25%
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 0	$ 82
Average Interest Rate on Commercial Paper Borrowings	0.00%	2.56%
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 54	$ 56
Average Interest Rate on Commercial Paper Borrowings	4.17%	2.02%
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Outstanding Commercial Paper	$ 54	$ 70
Average Interest Rate on Commercial Paper Borrowings	4.32%	2.43%

Debt and Credit Agreements - Is

Debt and Credit Agreements - Issuance of Long-Term Debt (Details) $ in Millions	Mar. 31, 2020USD ($)
Exelon Generation Co L L C [Member] | EEPF395Aug2020 [Member] | Energy Efficiency Project Financing [Member]
Debt Instrument [Line Items]
Interest Rate	3.95%
Debt Instrument, Face Amount	$ 2
Exelon Generation Co L L C [Member] | EEPF253April2021 [Member] | Energy Efficiency Project Financing [Member]
Debt Instrument [Line Items]
Interest Rate	2.53%
Debt Instrument, Face Amount	$ 1
Commonwealth Edison Co [Member] | FMB300March2050 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.00%
Debt Instrument, Face Amount	$ 650
Commonwealth Edison Co [Member] | FMB220Mar2030 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.20%
Debt Instrument, Face Amount	$ 350
Potomac Electric Power Company [Member] | FMB253Feb2030 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.53%
Debt Instrument, Face Amount	$ 150
Potomac Electric Power Company [Member] | FMB328Sep2050 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.28%
Debt Instrument, Face Amount	$ 150

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Narrative (Details) $ in Millions	Mar. 31, 2020USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Equity Securities without Readily Determinable Fair Value, Amount	$ 76
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	66
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	80
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	80
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	131
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	131
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	338
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	338
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	428
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	$ 428

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	Mar. 31, 2020	Dec. 31, 2019
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt to financing trust	$ 390	$ 390
Spent Nuclear Fuel Obligation, Noncurrent	1,204	1,199
Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	37,656	36,039
Long-term debt to financing trust	390	390
Spent Nuclear Fuel Obligation, Noncurrent	1,204	1,199
Estimate of Fair Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	39,464	40,033
Long-term debt to financing trust	387	428
Spent Nuclear Fuel Obligation, Noncurrent	723	1,055
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)	36,908	37,453
Long-term debt to financing trust	0	0
Spent Nuclear Fuel Obligation, Noncurrent	723	1,055
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)	2,556	2,580
Long-term debt to financing trust	387	428
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	1,204	1,199
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)	8,449	7,974
Spent Nuclear Fuel Obligation, Noncurrent	1,204	1,199
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)	8,364	8,670
Spent Nuclear Fuel Obligation, Noncurrent	723	1,055
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)	7,034	7,304
Spent Nuclear Fuel Obligation, Noncurrent	723	1,055
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)	1,330	1,366
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)	9,478	8,491
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)	10,483	9,848
Long-term debt to financing trust	204	227
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)	10,483	9,848
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	204	227
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)	3,406	3,405
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)	3,812	3,918
Long-term debt to financing trust	183	201
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)	3,762	3,868
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	183	201
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)	3,271	3,270
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)	3,572	3,649
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)	3,572	3,649
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)	6,708	6,563
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)	6,778	7,066
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)	5,602	5,902
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)	1,176	1,164
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)	3,015	2,864
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)	3,492	3,586
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)	3,009	3,198
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)	483	388
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)	1,575	1,567
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)	1,605	1,719
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)	1,334	1,408
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)	271	311
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)	1,325	1,327
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)	1,412	1,490
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)	991	1,026
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)	$ 421	$ 464

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	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)	$ 264		$ 247
Derivative Liability, Noncurrent	436		393
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	2
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value			2
Derivative Asset, Notional Amount	826		724
Margin Deposit Assets	644		511
Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	483		373
Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	110		110
Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	121		177
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	110		147
Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	1,399		639
Assets, Fair Value Disclosure	14,858		15,584
Deferred Compensation Liability, Current and Noncurrent	(126)		(147)
Total Liabilities	(794)		(763)
Fair Value, Net Asset (Liability)	14,064		14,821
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	(668)		(616)
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	(6,209)		(5,154)
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	(48)		(49)
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	5,589		4,587
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	11,934		13,500
Fair Value, Recurring [Member] | Cash Equivalents NDT [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	452		452
Fair Value, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	5,060		6,494
Fair Value, Recurring [Member] | Fixed Income Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	4,556		4,783
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	1,670		1,726
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	1,864		1,939
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	37		42
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	87		90
Fair Value, Recurring [Member] | Other Fixed Income [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	898		986
Fair Value, Recurring [Member] | Middle Market Lending [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	786		762
Fair Value, Recurring [Member] | Private Equity Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	444		402
Fair Value, Recurring [Member] | Real Estate Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	636		607
Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	251		262
Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	51		50
Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	75		81
Fair Value, Recurring [Member] | Fixed Income Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	11		12
Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	114		119
Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	5,888		4,744
Fair Value, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	86		97
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	(4,700)		(3,658)
Fair Value, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,274		1,183
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	126		163
Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	1,399		639
Assets, Fair Value Disclosure	6,070		6,156
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	4		0
Fair Value, Net Asset (Liability)	6,074		6,156
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	4		0
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	(990)		(1,071)
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	994		1,071
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	4,699		5,526
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	373		365
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	2,603		3,353
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	1,723		1,808
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	1,723		1,808
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		131
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	51		50
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	75		81
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	714		768
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	(868)		(908)
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	(154)		(140)
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	548		551
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	3,636		4,061
Deferred Compensation Liability, Current and Noncurrent	(126)		(147)
Total Liabilities	(312)		(322)
Fair Value, Net Asset (Liability)	3,324		3,739
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	(186)		(175)
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	(3,476)		(2,855)
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	(28)		(34)
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	3,318		2,714
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	3,159		3,605
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	79		87
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	1,377		1,753
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	1,703		1,765
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	1,412		1,469
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	141		131
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	37		42
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	87		90
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	26		33
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	83		90
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	11		12
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	72		78
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	3,135		2,491
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	29		37
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	(2,770)		(2,162)
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	394		366
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	215		214
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	1,574		1,509
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	(486)		(441)
Fair Value, Net Asset (Liability)	1,088		1,068
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	(486)		(441)
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	(1,743)		(1,228)
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	(20)		(15)
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	1,277		802
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	498		511
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	258		257
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	258		257
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	240		254
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	42		41
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	42		41
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	2,039		1,485
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	57		60
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	(1,062)		(588)
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	1,034		957
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	3,578		3,858
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	0		0
Fair Value, Net Asset (Liability)	3,578		3,858
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	3,578		3,858
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	1,080		1,388
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	872		953
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	872		953
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	546		508
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	444		402
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	636		607
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 And Liabilities Measured On Recurring Basis Financial Statement Captions [Line Items]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings	177	$ 80
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(303)		(307)
Mark-to-market derivative liabilities (current liabilities)	229		215
Derivative Liability, Noncurrent	158		123
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	(2)
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value			2
Derivative Asset, Notional Amount	826		724
Margin Deposit Assets	644		511
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	317		177
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	63		58
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	110		147
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	591		214
Assets, Fair Value Disclosure	13,848		14,951
Deferred Compensation Liability, Current and Noncurrent	(34)		(41)
Total Liabilities	(388)		(356)
Fair Value, Net Asset (Liability)	13,460		14,595
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	(354)		(315)
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	(5,895)		(4,853)
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	(48)		(49)
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	5,589		4,587
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	11,934		13,500
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	452		452
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	5,060		6,494
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	4,556		4,783
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	1,670		1,726
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	1,864		1,939
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	37		42
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	87		90
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	898		986
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	786		762
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	444		402
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	636		607
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	49		54
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		4
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	23		25
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	22		25
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	5,888		4,744
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	86		97
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	(4,700)		(3,658)
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	1,274		1,183
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	126		163
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	591		214
Assets, Fair Value Disclosure	5,163		5,629
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	4		0
Fair Value, Net Asset (Liability)	5,167		5,629
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	4		0
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	(990)		(1,071)
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	994		1,071
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	4,699		5,526
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	373		365
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	2,603		3,353
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	1,723		1,808
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	1,723		1,808
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	27		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		4
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	23		25
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	714		768
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	(868)		(908)
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	(154)		(140)
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	548		551
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	3,575		3,996
Deferred Compensation Liability, Current and Noncurrent	(34)		(41)
Total Liabilities	(220)		(216)
Fair Value, Net Asset (Liability)	3,355		3,780
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	(186)		(175)
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	(3,476)		(2,855)
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	(28)		(34)
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	3,318		2,714
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	3,159		3,605
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	79		87
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	1,377		1,753
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	1,703		1,765
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	1,412		1,469
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	141		131
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	37		42
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	87		90
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	26		33
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	22		25
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	22		25
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	3,135		2,491
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	29		37
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	(2,770)		(2,162)
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	394		366
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	215		214
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	1,532		1,468
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	(172)		(140)
Fair Value, Net Asset (Liability)	1,360		1,328
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	(172)		(140)
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	(1,429)		(927)
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	(20)		(15)
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	1,277		802
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	498		511
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	258		257
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	258		257
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	240		254
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	2,039		1,485
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	57		60
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	(1,062)		(588)
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	1,034		957
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	3,578		3,858
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	0		0
Fair Value, Net Asset (Liability)	3,578		3,858
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	3,578		3,858
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	1,080		1,388
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	872		953
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	872		953
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	546		508
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	444		402
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	636		607
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)	36		32
Derivative Liability, Noncurrent	278		269
Commonwealth Edison Co [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	67		90
Commonwealth Edison Co [Member] | Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	38		33
Commonwealth Edison Co [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	108		163
Commonwealth Edison Co [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	729		280
Assets, Fair Value Disclosure	729		280
Total mark-to-market derivative liabilities	(314)		(301)
Deferred Compensation Liability, Current and Noncurrent	(7)		(8)
Total Liabilities	(321)		(309)
Fair Value, Net Asset (Liability)	408		(29)
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	729		280
Assets, Fair Value Disclosure	729		280
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)	729		280
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)		(8)
Total Liabilities	(7)		(8)
Fair Value, Net Asset (Liability)	(7)		(8)
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	(314)		(301)
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	(314)		(301)
Fair Value, Net Asset (Liability)	(314)		(301)
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	30		12
PECO Energy Co [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	8		15
Assets, Fair Value Disclosure	25		34
Total mark-to-market derivative liabilities	0		0
Deferred Compensation Liability, Current and Noncurrent	(8)		(9)
Total Liabilities	(8)		(9)
Fair Value, Net Asset (Liability)	17		25
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	17		19
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	7		8
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	10		11
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	8		15
Assets, Fair Value Disclosure	15		23
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)	15		23
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	7		8
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	7		8
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	10		11
Total mark-to-market derivative liabilities	0		0
Deferred Compensation Liability, Current and Noncurrent	(8)		(9)
Total Liabilities	(8)		(9)
Fair Value, Net Asset (Liability)	2		2
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	10		11
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	10		11
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	11		24
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		1
Baltimore Gas and Electric Company [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	9		8
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)	4		3
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	9		8
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	8		8
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	1		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	0		0
Assets, Fair Value Disclosure	8		8
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)	8		8
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	8		8
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	8		8
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	1		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)	1		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	1		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	1		0
Pepco Holdings LLC [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	35		57
Pepco Holdings LLC [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	12		14
Pepco Holdings LLC [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	63		124
Assets, Fair Value Disclosure	198		259
Deferred Compensation Liability, Current and Noncurrent	(16)		(19)
Total Liabilities	(16)		(19)
Fair Value, Net Asset (Liability)	182		240
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	135		135
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	44		44
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		14
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	11		12
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	67		65
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	63		124
Assets, Fair Value Disclosure	120		182
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	0		0
Fair Value, Net Asset (Liability)	120		182
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	57		58
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	44		44
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		14
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	36		36
Deferred Compensation Liability, Current and Noncurrent	(16)		(19)
Total Liabilities	(16)		(19)
Fair Value, Net Asset (Liability)	20		17
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	36		36
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	11		12
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	25		24
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	42		41
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	0		0
Fair Value, Net Asset (Liability)	42		41
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	42		41
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	42		41
Potomac Electric Power Company [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	17		29
Potomac Electric Power Company [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	34		34
Assets, Fair Value Disclosure	146		144
Deferred Compensation Liability, Current and Noncurrent	(2)		(2)
Total Liabilities	(2)		(2)
Fair Value, Net Asset (Liability)	144		142
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	112		110
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	44		43
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	1		2
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	67		65
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		34
Assets, Fair Value Disclosure	78		77
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	0		0
Fair Value, Net Asset (Liability)	78		77
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	44		43
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	44		43
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	26		26
Deferred Compensation Liability, Current and Noncurrent	(2)		(2)
Total Liabilities	(2)		(2)
Fair Value, Net Asset (Liability)	24		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	26		26
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	1		2
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	25		24
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	42		41
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	0		0
Fair Value, Net Asset (Liability)	42		41
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	42		41
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	42		41
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	6		13
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		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, 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		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 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		0
Total Liabilities	0		0
Fair Value, Net Asset (Liability)	0		0
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	8		12
Atlantic City Electric Company [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	12		14
Atlantic City Electric Company [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	15		16
Assets, Fair Value Disclosure	15		16
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	0		0
Fair Value, Net Asset (Liability)	15		16
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	15		16
Assets, Fair Value Disclosure	15		16
Deferred Compensation Liability, Current and Noncurrent	0		0
Total Liabilities	0		0
Fair Value, Net Asset (Liability)	15		16
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	78		90
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	$ 78		$ 90

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
	Mar. 31, 2020	Mar. 31, 2019
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 1,068	$ 907
Total realized / unrealized gains (losses)
Included in net income	10	(228)
Included in noncurrent payables to affiliates	0	0
Included in regulatory assets	(14)	20
Change in collateral	1	81
Purchases, sales, issuances and settlements
Purchases	42	58
Sales	(22)	0
Settlements	(14)	(17)
Transfers into Level 3	2	0
Transfers out of Level 3	15	17
Ending Balance	1,088	838
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	187	(148)
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
Total realized / unrealized gains (losses)
Included in net income	0	0
Included in noncurrent payables to affiliates	1	(11)
Included in regulatory assets	(1)	11
Change in collateral	0	0
Purchases, sales, issuances and settlements
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending Balance	0	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	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	177	80
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	1,328	1,118
Total realized / unrealized gains (losses)
Included in net income	9	(229)
Included in noncurrent payables to affiliates	(1)	11
Included in regulatory assets	0	0
Change in collateral	1	81
Purchases, sales, issuances and settlements
Purchases	42	58
Sales	(22)	0
Settlements	(14)	(17)
Transfers into Level 3	2	0
Transfers out of Level 3	15	17
Ending Balance	1,360	1,039
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	186	(149)
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	511	543
Total realized / unrealized gains (losses)
Included in net income	(1)	2
Included in noncurrent payables to affiliates	(1)	11
Included in regulatory assets	0	0
Change in collateral	0	0
Purchases, sales, issuances and settlements
Purchases	3	1
Sales	0	0
Settlements	(14)	(17)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending Balance	498	540
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(1)	2
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	817	575
Total realized / unrealized gains (losses)
Included in net income	10	(231)
Included in noncurrent payables to affiliates	0	0
Included in regulatory assets		0
Change in collateral	1	81
Purchases, sales, issuances and settlements
Purchases	39	57
Sales	(22)	0
Settlements	0	0
Transfers into Level 3	2	0
Transfers out of Level 3	15	17
Ending Balance	862	499
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	187	(151)
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)	10	5
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	(301)	(249)
Total realized / unrealized gains (losses)
Included in net income	0	0
Included in noncurrent payables to affiliates	0	0
Included in regulatory assets	(13)	9
Change in collateral	0	0
Purchases, sales, issuances and settlements
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending Balance	(314)	(240)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	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)	(23)	(14)
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	41	38
Total realized / unrealized gains (losses)
Included in net income	(1)	1
Included in noncurrent payables to affiliates	0	0
Included in regulatory assets	0	0
Change in collateral	0	0
Purchases, sales, issuances and settlements
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending Balance	42	39
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	1	1
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	41	38
Total realized / unrealized gains (losses)
Included in net income	1	1
Included in noncurrent payables to affiliates	0	0
Included in regulatory assets	0	0
Change in collateral	0	0
Purchases, sales, issuances and settlements
Purchases	0	0
Sales	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Ending Balance	42	39
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 1	$ 1

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
	Mar. 31, 2020	Mar. 31, 2019
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	$ (10)	$ 228
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	187	(148)
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	72	(128)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	205	(91)
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	(62)	(103)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(18)	(60)
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	1	1
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	1	1
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	(1)	2
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(1)	2
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	(9)	229
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	186	(149)
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	72	(128)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	205	(91)
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	(62)	(103)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(18)	(60)
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	(1)	2
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(1)	2
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	1	1
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	1	1
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	1	1
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 1	$ 1

Fair Value of Financial Asset_8

Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Fair Value, Inputs, Level 3 [Member]
Derivatives Fair Value Footnotes [Abstract]
Cash Collateral Posted	$ 215,000,000	$ 214,000,000
Fair Value, Inputs, Level 3 [Member] | Economic Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	610,000,000	558,000,000
Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ (314,000,000)	$ (301,000,000)
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	6	9
Forward gas price assets	1.02	0.83
Forward heat rate	900.00%	900.00%
Derivative Asset (Liability) Net, Measurement Input	0.03	0.03
Fair Value Inputs Renewable Factor	90.00%	91.00%
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	136	180
Forward gas price assets	8.10	10.72
Forward heat rate	1000.00%	1000.00%
Derivative Asset (Liability) Net, Measurement Input	0.07	0.07
Fair Value Inputs Renewable Factor	122.00%	123.00%
Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	27	29
Forward gas price assets	2.43	2.55
Forward heat rate	922.00%	968.00%
Derivative Asset (Liability) Net, Measurement Input	0.05	0.05
Fair Value Inputs Renewable Factor	99.00%	99.00%
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	0.08	0.08
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	3.04	2.36
Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Option Model Valuation Technique [Member] | Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	0.70	0.70
Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 37,000,000	$ 45,000,000
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	15	25
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	136	180
Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	31	33
Exelon Generation Co L L C [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	$ (303,000,000)	$ (307,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives Fair Value Footnotes [Abstract]
Cash Collateral Posted	215,000,000	214,000,000
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	$ 610,000,000	$ 558,000,000
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	6	9
Forward gas price assets	1.02	0.83
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	136	180
Forward gas price assets	8.10	10.72
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	27	29
Forward gas price assets	2.43	2.55
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	0.08	0.08
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	3.04	2.36
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Option Model Valuation Technique [Member] | Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Derivative Asset (Liability) Net, Measurement Input	0.70	0.70
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	$ 37,000,000	$ 45,000,000
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	15	25
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	136	180
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Proprietary Trading [Member] | Discounted Cash Flow [Member] | Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward power price assets	31	33
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	$ (314,000,000)	$ (301,000,000)
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%	900.00%
Derivative Asset (Liability) Net, Measurement Input	0.03	0.03
Fair Value Inputs Renewable Factor	90.00%	91.00%
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%	1000.00%
Derivative Asset (Liability) Net, Measurement Input	0.07	0.07
Fair Value Inputs Renewable Factor	122.00%	123.00%
Commonwealth Edison Co [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member] | Discounted Cash Flow [Member] | Arithmetic Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Abstract]
Forward heat rate	922.00%	968.00%
Derivative Asset (Liability) Net, Measurement Input	0.0511	0.0495
Fair Value Inputs Renewable Factor	99.00%	99.00%

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	Mar. 23, 2016USD ($)MW	Mar. 31, 2020USD ($)MGPSiteOpen_claimMW	Mar. 31, 2019MW	Dec. 31, 2022MW	Dec. 31, 2017MW	Dec. 31, 2019USD ($)
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 2,718
Accrual for Environmental Loss Contingencies, Gross		472				$ 478
Liability for Asbestos and Environmental Claims, Gross		82				83
Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		2,134
Accrual for Environmental Loss Contingencies, Gross		104				105
Liability for Asbestos and Environmental Claims, Gross		82				83
Commonwealth Edison Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 222
Mgp Site Contingency Monitoring Count | MGPSite		21
Accrual for Environmental Loss Contingencies, Gross		$ 301				304
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		$ 19				19
Baltimore Gas and Electric Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 19
Mgp Site Contingency Monitoring Count | MGPSite		4
Accrual for Environmental Loss Contingencies, Gross		$ 2				2
Pepco Holdings LLC [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		48
Accrual for Environmental Loss Contingencies, Gross		46				48
Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		23
Accrual for Environmental Loss Contingencies, Gross		44				46
Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment		$ 15
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		$ 27
Open Asbestos Related Personal Injury Claims | Open_claim		268
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		$ 55
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	$ 122
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		$ 122
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	Mar. 31, 2020USD ($)
Other Commitments [Line Items]
Other Commitment	$ 2,718
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	48
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	23
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	15
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	95
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	75
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	62
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	8
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	$ 5

Commitments and Contingencies_4

Commitments and Contingencies - Schedule of Commercial Commitments (Details) $ in Millions	Mar. 31, 2020USD ($)
Other Commitments [Line Items]
Other Commitment	$ 2,718
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1,779
Other Commitment, Due in Second Year	537
Other Commitment, Due in Third Year	4
Other Commitment, Due in Fourth Year	3
Other Commitment, Due in Fifth Year	12
Other Commitment, Due after Fifth Year	383
Guarantor Obligations, Maximum Exposure, Undiscounted	72
Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,464
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1,080
Other Commitment, Due in Second Year	384
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
Surety Bonds
Other Commitments [Line Items]
Other Commitment	849
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	698
Other Commitment, Due in Second Year	151
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
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	27
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1
Other Commitment, Due in Second Year	2
Other Commitment, Due in Third Year	4
Other Commitment, Due in Fourth Year	3
Other Commitment, Due in Fifth Year	12
Other Commitment, Due after Fifth Year	5
Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Other Commitment	2,134
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1,662
Other Commitment, Due in Second Year	472
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
Exelon Generation Co L L C [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,449
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1,071
Other Commitment, Due in Second Year	378
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
Exelon Generation Co L L C [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	685
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	591
Other Commitment, Due in Second Year	94
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	222
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	15
Other Commitment, Due in Second Year	7
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
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	15
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	11
Other Commitment, Due in Second Year	4
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] | 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	8
Other Commitment, Due in Second Year	1
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	8
Other Commitment, Due in Second Year	1
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	19
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	18
Other Commitment, Due in Second Year	1
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	2
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	2
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
Baltimore Gas and Electric Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	17
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	16
Other Commitment, Due in Second Year	1
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	48
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	21
Other Commitment, Due in Second Year	3
Other Commitment, Due in Third Year	4
Other Commitment, Due in Fourth Year	3
Other Commitment, Due in Fifth Year	12
Other Commitment, Due after Fifth Year	5
Guarantor Obligations, Maximum Exposure, Undiscounted	72
Pepco Holdings LLC [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	21
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	20
Other Commitment, Due in Second Year	1
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	27
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	1
Other Commitment, Due in Second Year	2
Other Commitment, Due in Third Year	4
Other Commitment, Due in Fourth Year	3
Other Commitment, Due in Fifth Year	12
Other Commitment, Due after Fifth Year	5
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	23
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	14
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	4
Other Commitment, Due after Fifth Year	2
Guarantor Obligations, Maximum Exposure, Undiscounted	24
Potomac Electric Power Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	14
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	14
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
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	1
Other Commitment, Due in Third Year	1
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	4
Other Commitment, Due after Fifth Year	2
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	15
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	3
Other Commitment, Due in Second Year	2
Other Commitment, Due in Third Year	2
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	5
Other Commitment, Due after Fifth Year	2
Guarantor Obligations, Maximum Exposure, Undiscounted	30
Delmarva Power and Light Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	4
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	3
Other Commitment, Due in Second Year	1
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	2
Other Commitment, Due in Fourth Year	1
Other Commitment, Due in Fifth Year	5
Other Commitment, Due after Fifth Year	2
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	10
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	4
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	3
Other Commitment, Due after Fifth Year	1
Guarantor Obligations, Maximum Exposure, Undiscounted	18
Atlantic City Electric Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	3
Other Commitments, Future Minimum Payments, Remainder of Fiscal Year	3
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
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	1
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	3
Other Commitment, Due after Fifth Year	$ 1
Maximum [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Lessor, Operating Lease, Term of Contract	8 years
Minimum [Member] | Guaranteed lease residual values
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	Mar. 31, 2020	Dec. 31, 2019
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	$ 472	$ 478
Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	104	105
Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	301	304
PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	19	19
Baltimore Gas and Electric Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	2	2
Pepco Holdings LLC [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	46	48
Potomac Electric Power Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	44	46
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	317	320
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	300	303
Accrual For MGP Investigation And Remediation [Member] | PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	17	17
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	0	0
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

Changes in Accumulated Other _3

Changes in Accumulated Other Comprehensive Income - Schedule of Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 34,573	$ 33,070
Other comprehensive income	21	(18)
Ending balance	34,616	33,704
Gains (Losses) on Cash Flow Hedges
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2)	(2)
OCI before reclassifications	(1)	0
Amounts reclassified from AOCI	0	0
Other comprehensive income	(1)	0
Ending balance	(3)	(2)
Pension and Non-Pension Postretirement Benefit Plan Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(3,165)	(2,960)
OCI before reclassifications	(7)	(38)
Amounts reclassified from AOCI	37	20
Other comprehensive income	30	(18)
Ending balance	(3,135)	(2,978)
Foreign Currency Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(27)	(33)
OCI before reclassifications	(8)	2
Amounts reclassified from AOCI	0	0
Other comprehensive income	(8)	2
Ending balance	(35)	(31)
AOCI of Investments in Unconsolidated Affiliates
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance		0
OCI before reclassifications		(1)
Amounts reclassified from AOCI		0
Other comprehensive income		(1)
Ending balance		(1)
Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(3,194)	(2,995)
OCI before reclassifications	(16)	(37)
Amounts reclassified from AOCI	37	20
Other comprehensive income	21	(17)
Ending balance	$ (3,173)	$ (3,012)

Changes in Accumulated Other _4

Changes in Accumulated Other Comprehensive Income - Income Taxes Allocated to Other Comprehensive Income (Loss) Components (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Prior service costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ 4	$ 6
Actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(17)	(13)
Pension and Non-Pension Postretirement Benefit Plan Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ 3	$ 14

Variable Interest Entities - Na

Variable Interest Entities - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Apr. 01, 2014
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 72
CENG [Member] | Payment Guarantee [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			$ 245
CENG [Member] | Financial Guarantee [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]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		49.99%
Guarantor Obligations, Current Carrying Value	$ 688

Variable Interest Entities - As

Variable Interest Entities - Assets and Liabilities of VIES which Creditors or Beneficiaries have no Recourse (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 1,457	$ 587	$ 880	$ 1,349
Restricted cash and cash equivalents		414	358	223	247
Accounts receivable, net
Customer		4,042	4,592
Unamortized energy contract asset		47	47
Inventory, net
Materials and supplies		1,463	1,456
Other current assets		1,629	1,253
Total current assets		12,476	12,037
Property, plant and equipment, net		81,017	80,233
NDT funds		11,611	13,190
Unamortized energy contract asset		329	336
Other Assets, Noncurrent		3,164	3,197
Total assets	[1]	124,677	124,977
Long-term debt due within one year		2,848	4,710
Accounts payable		2,883	3,560
Accrued expenses		1,535	1,981
Unamortized energy contract liabilities		121	132
Other Liabilities, Current		1,276	1,331
Total current liabilities		11,774	14,185
Long-term debt		34,808	31,329
Asset retirement obligations, noncurrent		10,951	10,846
Unamortized energy contract liabilities		317	338
Other Liabilities, Noncurrent		3,017	3,064
Total liabilities	[1]	90,061	90,404
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		51	163
Restricted cash and cash equivalents		84	88
Accounts receivable, net
Customer		131	151
Other		44	39
Unamortized energy contract asset		22	23
Inventory, net
Materials and supplies		231	227
Other current assets		42	32
Total current assets		605	723
Property, plant and equipment, net		6,017	6,022
NDT funds		2,405	2,741
Unamortized energy contract asset		264	250
Other Assets, Noncurrent		71	89
Total noncurrent assets		8,757	9,102
Total assets		9,362	9,825
Long-term debt due within one year		543	544
Accounts payable		121	106
Accrued expenses		46	70
Unamortized energy contract liabilities		7	8
Other Liabilities, Current		3	3
Total current liabilities		720	731
Long-term debt		502	527
Asset retirement obligations, noncurrent		2,156	2,128
Unamortized energy contract liabilities		1	1
Other Liabilities, Noncurrent		37	89
Total noncurrent liabilities		2,696	2,745
Total liabilities		3,416	3,476
PP&E - unrestricted asset		20	20
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		821	303	537	750
Restricted cash and cash equivalents		150	146	139	153
Accounts receivable, net
Customer		2,415	2,893
Unamortized energy contract asset		47	47
Inventory, net
Materials and supplies		1,038	1,026
Other current assets		1,243	941
Total current assets		7,324	7,076
Property, plant and equipment, net		24,169	24,193
NDT funds		11,611	13,190
Unamortized energy contract asset		328	336
Other Assets, Noncurrent		1,941	1,960
Total assets	[2]	47,882	48,995
Long-term debt due within one year		1,623	2,624
Accounts payable		1,195	1,692
Accrued expenses		603	786
Unamortized energy contract liabilities		12	17
Other Liabilities, Current		434	517
Total current liabilities		6,325	7,289
Long-term debt		5,943	4,464
Asset retirement obligations, noncurrent		10,709	10,603
Unamortized energy contract liabilities		10	11
Other Liabilities, Noncurrent		1,424	1,415
Total liabilities	[2]	32,699	33,165
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		51	163
Restricted cash and cash equivalents		81	85
Accounts receivable, net
Customer		131	151
Other		44	39
Unamortized energy contract asset		22	23
Inventory, net
Materials and supplies		231	227
Other current assets		38	31
Total current assets		598	719
Property, plant and equipment, net		6,017	6,022
NDT funds		2,405	2,741
Unamortized energy contract asset		264	250
Other Assets, Noncurrent		56	73
Total noncurrent assets		8,742	9,086
Total assets		9,340	9,805
Long-term debt due within one year		519	523
Accounts payable		121	106
Accrued expenses		46	70
Unamortized energy contract liabilities		7	8
Other Liabilities, Current		3	3
Total current liabilities		696	710
Long-term debt		483	504
Asset retirement obligations, noncurrent		2,156	2,128
Unamortized energy contract liabilities		1	1
Other Liabilities, Noncurrent		37	89
Total noncurrent liabilities		2,677	2,722
Total liabilities		3,373	3,432
PP&E - unrestricted asset		20	20
Variable Interest Entity, Consolidated, Liabilities, Recourse		4	3
Pepco Holdings LLC [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		49	131	33	124
Restricted cash and cash equivalents		37	36	39	43
Accounts receivable, net
Customer		429	479
Inventory, net
Materials and supplies		187	190
Other current assets		57	49
Total current assets		1,369	1,480
Property, plant and equipment, net		14,491	14,296
Other Assets, Noncurrent		316	323
Total assets	[3]	22,753	22,719
Long-term debt due within one year		144	103
Accounts payable		423	462
Accrued expenses		280	296
Unamortized energy contract liabilities		109	115
Other Liabilities, Current		129	131
Total current liabilities		1,481	1,612
Long-term debt		6,564	6,460
Asset retirement obligations, noncurrent		57	57
Unamortized energy contract liabilities		307	327
Other Liabilities, Noncurrent		552	577
Total liabilities	[3]	13,027	13,111
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	3
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		4	1
Total current assets		7	4
Property, plant and equipment, net		0	0
NDT funds		0	0
Unamortized energy contract asset		0	0
Other Assets, Noncurrent		15	16
Total noncurrent assets		15	16
Total assets		22	20
Long-term debt due within one year		24	21
Accounts payable		0	0
Accrued expenses		0	0
Unamortized energy contract liabilities		0	0
Other Liabilities, Current		0	0
Total current liabilities		24	21
Long-term debt		19	23
Asset retirement obligations, noncurrent		0	0
Unamortized energy contract liabilities		0	0
Other Liabilities, Noncurrent		0	0
Total noncurrent liabilities		19	23
Total liabilities		43	44
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		8	12	6	7
Restricted cash and cash equivalents		3	2	$ 3	$ 4
Accounts receivable, net
Customer		92	108
Inventory, net
Other current assets		3	5
Total current assets		261	270
Property, plant and equipment, net		3,249	3,190
Other Assets, Noncurrent		51	53
Total assets	[4]	3,978	3,933
Long-term debt due within one year		60	20
Accounts payable		145	144
Accrued expenses		40	42
Other Liabilities, Current		8	9
Total current liabilities		460	360
Long-term debt		1,265	1,307
Other Liabilities, Noncurrent		37	39
Total liabilities	[4]	2,711	2,657
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	3
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	3
Property, plant and equipment, net		0	0
NDT funds		0	0
Unamortized energy contract asset		0	0
Other Assets, Noncurrent		12	14
Total noncurrent assets		12	14
Total assets		15	17
Long-term debt due within one year		20	20
Accounts payable		0	0
Accrued expenses		0	0
Unamortized energy contract liabilities		0	0
Other Liabilities, Current		0	0
Total current liabilities		20	20
Long-term debt		16	21
Asset retirement obligations, noncurrent		0	0
Unamortized energy contract liabilities		0	0
Other Liabilities, Noncurrent		0	0
Total noncurrent liabilities		16	21
Total liabilities		$ 36	$ 41
[1]	Exelon’s consolidated assets include $9,056 million and $9,532 million at March 31, 2020 and December 31, 2019 , respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,412 million and $3,473 million at March 31, 2020 and December 31, 2019 , respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 16 — Variable Interest Entities for additional information.
[2]	Generation’s consolidated assets include $9,034 million and $9,512 million at March 31, 2020 and December 31, 2019 , respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,369 million and $3,429 million at March 31, 2020 and December 31, 2019 , respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 16 — Variable Interest Entities for additional information.
[3]	PHI’s consolidated total assets include $22 million and $20 million at March 31, 2020 and December 31, 2019 , respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $43 million and $44 million at March 31, 2020 and December 31, 2019 , respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 16 — Variable Interest Entities for additional information.
[4]	ACE’s consolidated total assets include $15 million and $17 million at March 31, 2020 and December 31, 2019 , respectively, of ACE's consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated total liabilities include $36 million and $41 million at March 31, 2020 and December 31, 2019 , respectively, of ACE's consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 16 — Variable Interest Entities for additional information.

Variable Interest Entities - Su

Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Total assets	$ 1,126	$ 1,079
Total liabilities	381	260
Exelon's ownership interest in VIE	183	191
Other ownership interests in VIE	563	629
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	695	636
Total liabilities	158	33
Exelon's ownership interest in VIE	0	0
Other ownership interests in VIE	538	604
Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Total assets	431	443
Total liabilities	223	227
Exelon's ownership interest in VIE	183	191
Other ownership interests in VIE	25	25
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets	1,126	1,079
Total liabilities	381	260
Exelon's ownership interest in VIE	183	191
Other ownership interests in VIE	563	629
Exelon Generation Co L L C [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] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	695	636
Total liabilities	158	33
Exelon's ownership interest in VIE	0	0
Other ownership interests in VIE	538	604
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	431	443
Total liabilities	223	227
Exelon's ownership interest in VIE	183	191
Other ownership interests in VIE	25	25
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	$ 0	$ 0

Supplemental Financial Inform_3

Supplemental Financial Information - Taxes Other Than Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Supplemental Statement of Operations Information [Line Items]
Utility taxes	$ 218	$ 223
Property	150	149
Payroll	63	65
Exelon Generation Co L L C [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	26	26
Property	69	71
Payroll	31	33
Commonwealth Edison Co [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	60	62
Property	7	7
Payroll	7	7
PECO Energy Co [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	31	34
Property	4	3
Payroll	4	4
Baltimore Gas and Electric Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	26	27
Property	39	37
Payroll	4	4
Pepco Holdings LLC [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	75	74
Property	31	29
Payroll	8	7
Potomac Electric Power Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	69	69
Property	21	21
Payroll	2	2
Delmarva Power and Light Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	6	5
Property	9	8
Payroll	1	1
Atlantic City Electric Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	0	0
Property	1	0
Payroll	$ 1	$ 1

Supplemental Financial Inform_4

Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	$ 5	$ 4
Variable Lease Income	69	52
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	47	54
Net realized income on NDT funds - Non-regulatory agreement units	82	54
Net unrealized (losses) gains on NDT funds - Regulatory agreement units	(932)	379
Net unrealized (losses) gains on NDT funds - Non-regulatory agreement units	(706)	280
Regulatory offset to NDT fund-related activities	709	(348)
Decommissioning-related activities	(800)	419
AFUDC - Equity	23	22
Non-service net periodic benefit cost	10	5
Exelon Generation Co L L C [Member]
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	3	3
Variable Lease Income	69	52
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	47	54
Net realized income on NDT funds - Non-regulatory agreement units	82	54
Net unrealized (losses) gains on NDT funds - Regulatory agreement units	(932)	379
Net unrealized (losses) gains on NDT funds - Non-regulatory agreement units	(706)	280
Regulatory offset to NDT fund-related activities	709	(348)
Decommissioning-related activities	(800)	419
AFUDC - Equity	0	0
Commonwealth Edison Co [Member]
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	0	0
Variable Lease Income	0	0
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	6	5
PECO Energy Co [Member]
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	0	0
Variable Lease Income	0	0
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	3	3
Baltimore Gas and Electric Company [Member]
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	0	0
Variable Lease Income	0	0
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	5	5
Pepco Holdings LLC [Member]
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	1	1
Variable Lease Income	0	0
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	9	9
Potomac Electric Power Company [Member]
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	0	0
Variable Lease Income	0	0
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	6	6
Delmarva Power and Light Company [Member]
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	1	1
Variable Lease Income	0	0
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	1	1
Atlantic City Electric Company [Member]
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	0	0
Variable Lease Income	0	0
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	$ 2	$ 2

Supplemental Financial Inform_5

Supplemental Financial Information - Cash Flow (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	$ 856	$ 917
Amortization of regulatory assets	149	143
Amortization of intangible assets, net	16	15
Amortization of energy contract assets and liabilities	2
Nuclear fuel	231	261
ARO accretion	124	124
Total depreciation, amortization and accretion	1,378	1,460
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	98	106
Provision for uncollectible accounts	45	43
Other decommissioning-related activity	128	(202)
Energy-related options	6	37
Amortization of rate stabilization deferral	(54)	(6)
Discrete impacts from EIMA and FEJA	(17)	28
Long-term incentive plan	(7)	25
Amortization of operating ROU asset	51	53
Exelon Generation Co L L C [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	290	392
Amortization of regulatory assets	0	0
Amortization of intangible assets, net	14	13
Amortization of energy contract assets and liabilities	2
Nuclear fuel	231	261
ARO accretion	124	123
Total depreciation, amortization and accretion	661	789
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	27	31
Provision for uncollectible accounts	4	0
Other decommissioning-related activity	128	(202)
Energy-related options	6	37
Amortization of rate stabilization deferral	0	0
Amortization of operating ROU asset	35	34
Commonwealth Edison Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	228	219
Amortization of regulatory assets	45	32
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	273	251
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	28	24
Provision for uncollectible accounts	7	9
Amortization of rate stabilization deferral	0	0
Discrete impacts from EIMA and FEJA	(17)	28
Amortization of operating ROU asset	0	1
PECO Energy Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	79	74
Amortization of regulatory assets	7	7
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	86	81
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	1	2
Provision for uncollectible accounts	17	16
Amortization of rate stabilization deferral	0	0
Amortization of operating ROU asset	0	0
Baltimore Gas and Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	97	85
Amortization of regulatory assets	46	51
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	143	136
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	15	15
Provision for uncollectible accounts	7	8
Amortization of rate stabilization deferral	(35)	0
Amortization of operating ROU asset	8	8
Pepco Holdings LLC [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	144	127
Amortization of regulatory assets	50	53
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	194	180
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	17	23
Provision for uncollectible accounts	10	10
Amortization of rate stabilization deferral	(19)	(6)
Amortization of operating ROU asset	5	9
Potomac Electric Power Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	64	58
Amortization of regulatory assets	31	36
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	95	94
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	3	6
Provision for uncollectible accounts	4	4
Amortization of rate stabilization deferral	(15)	(7)
Amortization of operating ROU asset	2	2
Delmarva Power and Light Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	38	35
Amortization of regulatory assets	10	11
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	48	46
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	1	4
Provision for uncollectible accounts	3	4
Amortization of rate stabilization deferral	(4)	1
Amortization of operating ROU asset	2	2
Atlantic City Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	34	25
Amortization of regulatory assets	9	6
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	43	31
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	3	4
Provision for uncollectible accounts	3	2
Amortization of rate stabilization deferral	0	0
Amortization of operating ROU asset	$ 1	$ 1

Supplemental Financial Inform_6

Supplemental Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 1,457	$ 587	$ 880	$ 1,349
Restricted cash	414	358	223	247
Restricted cash included in other long-term assets	121	177	211	185
Total cash, cash equivalents and restricted cash	1,992	1,122	1,314	1,781
Accrued Expenses [Abstract]
Compensation-related accruals	557	1,052
Taxes accrued	442	414
Interest accrued	407	337
Exelon Generation Co L L C [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	821	303	537	750
Restricted cash	150	146	139	153
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	971	449	676	903
Accrued Expenses [Abstract]
Compensation-related accruals	207	422
Taxes accrued	244	222
Interest accrued	84	65
Commonwealth Edison Co [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	514	90	68	135
Restricted cash	211	150	17	29
Restricted cash included in other long-term assets	108	163	193	166
Total cash, cash equivalents and restricted cash	833	403	278	330
Accrued Expenses [Abstract]
Compensation-related accruals	87	171
Taxes accrued	85	83
Interest accrued	69	110
PECO Energy Co [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	31	21	41	130
Restricted cash	7	6	6	5
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	38	27	47	135
Accrued Expenses [Abstract]
Compensation-related accruals	39	58
Taxes accrued	1	3
Interest accrued	33	37
Baltimore Gas and Electric Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	11	24	12	7
Restricted cash	1	1	4	6
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	12	25	16	13
Accrued Expenses [Abstract]
Compensation-related accruals	44	78
Taxes accrued	43	26
Interest accrued	38	46
Pepco Holdings LLC [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	49	131	33	124
Restricted cash	37	36	39	43
Restricted cash included in other long-term assets	12	14	19	19
Total cash, cash equivalents and restricted cash	98	181	91	186
Accrued Expenses [Abstract]
Compensation-related accruals	63	101
Taxes accrued	114	117
Interest accrued	78	49
Potomac Electric Power Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	18	30	11	16
Restricted cash	33	33	35	37
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	51	63	46	53
Accrued Expenses [Abstract]
Compensation-related accruals	22	28
Taxes accrued	79	90
Interest accrued	37	23
Delmarva Power and Light Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	7	13	7	23
Restricted cash	0	0	1	1
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	7	13	8	24
Accrued Expenses [Abstract]
Compensation-related accruals	14	19
Taxes accrued	25	14
Interest accrued	20	8
Atlantic City Electric Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	8	12	6	7
Restricted cash	3	2	3	4
Restricted cash included in other long-term assets	12	14	19	19
Total cash, cash equivalents and restricted cash	23	28	$ 28	$ 30
Accrued Expenses [Abstract]
Compensation-related accruals	10	15
Taxes accrued	7	8
Interest accrued	$ 19	$ 12

Related Party Transactions - Op

Related Party Transactions - Operating Revenues and Purchased Power and Fuel (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Related Party Transaction [Line Items]
Revenue from Related Parties	$ 1	$ 0
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	330	317
Purchased power and/or fuel from affiliates	(6)	1
Exelon Generation Co L L C [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	90	94
Purchased power and/or fuel from affiliates	7	3
Exelon Generation Co L L C [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	37	45
Exelon Generation Co L L C [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	99	76
Exelon Generation Co L L C [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	103	101
Exelon Generation Co L L C [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	79	70
Exelon Generation Co L L C [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	22	23
Exelon Generation Co L L C [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	2	8
Exelon Generation Co L L C [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	1	1
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	5	4
Purchased power and/or fuel from affiliates	97	97
Commonwealth Edison Co [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Purchased power and/or fuel from affiliates	$ 97	$ 97

Related Party Transactions - BS

Related Party Transactions - BSC and PHISCO Service Companies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	$ 113	$ 99
PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	14	22
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	142	150
Exelon Generation Co L L C [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	11	11
Related Party Transaction, Expenses from Transactions with Related Party	140	149
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	74	62
Commonwealth Edison Co [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	42	25
Related Party Transaction, Expenses from Transactions with Related Party	72	62
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	38	38
PECO Energy Co [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	16	22
Related Party Transaction, Expenses from Transactions with Related Party	37	37
Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	42	39
Baltimore Gas and Electric Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	28	21
Related Party Transaction, Expenses from Transactions with Related Party	41	38
Pepco Holdings LLC [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	38	33
Pepco Holdings LLC [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	16	19
Related Party Transaction, Expenses from Transactions with Related Party	37	32
Pepco Holdings LLC [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	14	22
Related Party Transaction, Expenses from Transactions with Related Party	0	0
Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	51	54
Potomac Electric Power Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	6	8
Related Party Transaction, Expenses from Transactions with Related Party	21	21
Potomac Electric Power Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	6	9
Related Party Transaction, Expenses from Transactions with Related Party	30	33
Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	37	39
Delmarva Power and Light Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	5	5
Related Party Transaction, Expenses from Transactions with Related Party	13	13
Delmarva Power and Light Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	4	7
Related Party Transaction, Expenses from Transactions with Related Party	24	26
Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	33	34
Atlantic City Electric Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	4	4
Related Party Transaction, Expenses from Transactions with Related Party	11	11
Atlantic City Electric Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	4	6
Related Party Transaction, Expenses from Transactions with Related Party	$ 22	$ 23

Related Party Transactions - Cu

Related Party Transactions - Current Receivables From/Payables To Affiliates (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ 472	$ 528
Accounts Payable, Related Parties, Current	5	5
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	128	117
Accounts Receivable, Related Parties, Current	167	190
Exelon Generation Co L L C [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	69	78
Due to Related Parties, Current	27	37
Exelon Generation Co L L C [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	25	27
Exelon Generation Co L L C [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	22	28
Exelon Generation Co L L C [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Exelon Generation Co L L C [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	29	34
Exelon Generation Co L L C [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	1	7
Exelon Generation Co L L C [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	12	7
Exelon Generation Co L L C [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	9	9
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	87	103
Accounts Receivable, Related Parties, Current	18	28
Commonwealth Edison Co [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	17	27
Accounts Payable, Related Parties, Current	42	41
Commonwealth Edison Co [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	114	140
Commonwealth Edison Co [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Commonwealth Edison Co [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	1	1
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	51	55
Accounts Receivable, Related Parties, Current	0	1
PECO Energy Co [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PECO Energy Co [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	1
Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	52	66
Accounts Receivable, Related Parties, Current	1	1
Baltimore Gas and Electric Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	1	0
Baltimore Gas and Electric Company [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Baltimore Gas and Electric Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	1
Pepco Holdings LLC [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	82	98
Accounts Receivable, Related Parties, Current	1	1
Pepco Holdings LLC [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	13	14
Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	55	66
Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	21	32
Accounts Receivable, Related Parties, Current	1	0
Delmarva Power and Light Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	1	0
Delmarva Power and Light Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Delmarva Power and Light Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	27	25
Accounts Receivable, Related Parties, Current	4	4
Atlantic City Electric Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Atlantic City Electric Company [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	3	3
Atlantic City Electric Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	1	1
Business Services Company [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	181	217
Business Services Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	67	67
Business Services Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	42	54
Business Services Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	19	25
Business Services Company [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	27	34
Business Services Company [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	3	4
Business Services Company [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	11	16
Business Services Company [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	7	10
Business Services Company [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	5	7
Business Services Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member]
Related Party Transaction [Line Items]
Accounts Receivable, Related Parties, Current	30	36
PHI Service Company [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
PHI Service Company [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	12	15
PHI Service Company [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	9	11
PHI Service Company [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	9	10
PHI Service Company [Member] | Other Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	0	0
Other Legal Entities [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	11	13
Accounts Receivable, Related Parties, Current	70	51
Other Legal Entities [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	43	23
Other Legal Entities [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	3	8
Other Legal Entities [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	7	3
Other Legal Entities [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	3	4
Other Legal Entities [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	10	10
Other Legal Entities [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	2	1
Other Legal Entities [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	1	1
Other Legal Entities [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ 1	$ 1

Related Party Transactions - No

Related Party Transactions - Noncurrent Receivables from/Payables to affiliates (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	$ 2,302	$ 3,103
Exelon Generation Co L L C [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	2,040	2,622
Exelon Generation Co L L C [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	261	480
Other Legal Entities [Member] | Business Services Corporation [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	$ 1	$ 1

Related Party Transactions - Lo

Related Party Transactions - Long Term Debt to Financing Trusts (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Long-term debt to financing trust	$ 390	$ 390
ComEd Financing Three Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	206	206
PECO Trust Three Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	81	81
PECO Trust Four Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	103	103
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	205	205
Commonwealth Edison Co [Member] | ComEd Financing Three Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	205	205
Commonwealth Edison Co [Member] | PECO Trust Three Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	0	0
Commonwealth Edison Co [Member] | PECO Trust Four Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	0	0
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	184	184
PECO Energy Co [Member] | ComEd Financing Three Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	0	0
PECO Energy Co [Member] | PECO Trust Three Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	81	81
PECO Energy Co [Member] | PECO Trust Four Affiliate [Member]
Related Party Transaction [Line Items]
Long-term debt to financing trust	$ 103	$ 103

Subsequent Events - Narrative (

Subsequent Events - Narrative (Details) - Sale of accounts receivable [Member] - Subsequent Event [Member] $ in Millions	Apr. 08, 2020USD ($)
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 750
Transfer of Financial Assets Accounted for as Sales, Cash Proceeds Received for Assets Derecognized, Amount	500
Transfer of Financial Assets Accounted for as Sales, Amount Derecognized	1,200
Exelon Generation Co L L C [Member]
Subsequent Event [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	750
Transfer of Financial Assets Accounted for as Sales, Cash Proceeds Received for Assets Derecognized, Amount	500
Transfer of Financial Assets Accounted for as Sales, Amount Derecognized	$ 1,200