Exelon (EXC) 10-Q 3 Nov 20 2020 Q3 Quarterly report Financial data

Cover Page

Cover Page	9 Months Ended
	Sep. 30, 2020shares
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 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	975,572,463
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001109357
Amendment Flag	false
Exelon Generation Co L L C [Member]
Entity File Number	333-85496
Entity Registrant Name	EXELON GENERATION COMPANY, LLC
Entity Tax Identification Number	23-3064219
Entity Incorporation, State or Country Code	PA
Entity Address, Address Line One	300 Exelon Way
Entity Address, City or Town	Kennett Square
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19348-2473
City Area Code	(610)
Local Phone Number	765-5959
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Central Index Key	0001168165
Commonwealth Edison Co [Member]
Entity File Number	001-01839
Entity Registrant Name	COMMONWEALTH EDISON COMPANY
Entity Tax Identification Number	36-0938600
Entity Incorporation, State or Country Code	IL
Entity Address, Address Line One	440 South LaSalle Street
Entity Address, City or Town	Chicago
Entity Address, State or Province	IL
Entity Address, Postal Zip Code	60605-1028
City Area Code	(312)
Local Phone Number	394-4321
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock Shares Outstanding	127,021,354
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		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating revenues
Revenues from alternative revenue programs		$ (11)	$ (80)	$ (66)	$ (98)
Operating revenues from affiliates		1	0	4	0
Total operating revenues		8,853	8,929	24,925	26,096
Operating expenses
Operating and maintenance		2,732	2,072	7,370	6,419
Depreciation and amortization		1,289	1,083	3,312	3,237
Taxes other than income taxes		452	452	1,299	1,316
Total operating expenses		8,087	7,559	22,387	22,703
Gain on sales of assets and businesses		3	(17)	16	19
Operating income		769	1,353	2,554	3,412
Other income and (deductions)
Interest expense, net		(398)	(403)	(1,222)	(1,202)
Interest expense to affiliates		(6)	(6)	(19)	(19)
Other, net		421	158	352	837
Total other income and (deductions)		17	(251)	(889)	(384)
Income before income taxes		786	1,102	1,665	3,028
Income taxes		216	172	141	626
Equity in losses of unconsolidated affiliates		(1)	(170)	(5)	(182)
Net income (loss)		569	760	1,519	2,220
Net income (loss) attributable to noncontrolling interests		68	(12)	(85)	56
Net Income (Loss) Available to Common Stockholders, Basic		501	772	1,604	2,164
Other comprehensive income (loss), net of income taxes
Prior service benefit reclassified to periodic benefit cost		(10)	(16)	(30)	(49)
Actuarial loss reclassified to periodic benefit cost		49	37	142	111
Pension and non-pension postretirement benefit plan valuation adjustment		(13)	6	(17)	(32)
Unrealized (loss) gain on cash flow hedges		(1)	0	(2)	0
Unrealized (loss) gain on investments in unconsolidated affiliates		0	5	0	1
Unrealized gain (loss) on foreign currency translation		3	(2)	(3)	2
Other comprehensive income		28	30	90	33
Comprehensive income		597	790	1,609	2,253
Comprehensive income (loss) attributable to noncontrolling interests		68	(9)	(85)	57
Comprehensive income attributable to common shareholders/membership interest		$ 529	$ 799	$ 1,694	$ 2,196
Average shares of common stock outstanding:
Basic average shares of common stock outstanding		976	973	976	972
Assumed exercise and/or distributions of stock-based awards		1	1	0	1
Diluted average shares of common stock outstanding	[1]	977	974	976	973
Earnings per average common share:
Basic earnings per average common share		$ 0.51	$ 0.79	$ 1.64	$ 2.23
Diluted earnings per average common share		$ 0.51	$ 0.79	$ 1.64	$ 2.22
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		1		1
Retained Earnings [Member]
Other income and (deductions)
Net income (loss)		$ 501	$ 772
Exelon Generation Co L L C [Member]
Operating revenues
Operating revenues from affiliates		331	275	$ 932	$ 844
Total operating revenues		4,659	4,774	13,272	14,280
Operating expenses
Purchased power and/or fuel from affiliates		3	3	(6)	7
Operating and maintenance		1,605	947	3,779	3,131
Operating and maintenance from affiliates		132	140	409	439
Depreciation and amortization		558	407	1,161	1,221
Taxes other than income taxes		118	129	364	394
Total operating expenses		4,727	4,274	12,674	13,333
Gain on sales of assets and businesses		0	(18)	12	15
Operating income		(68)	482	610	962
Other income and (deductions)
Interest expense, net		(72)	(101)	(251)	(310)
Interest expense to affiliates		(8)	(8)	(26)	(26)
Other, net		367	128	199	729
Total other income and (deductions)		287	19	(78)	393
Income before income taxes		219	501	532	1,355
Income taxes		100	87	41	388
Equity in losses of unconsolidated affiliates		(2)	(170)	(6)	(183)
Net income (loss)		117	244	485	784
Net income (loss) attributable to noncontrolling interests		68	(13)	(85)	56
Net income attributable to membership interest		49	257	570	728
Other comprehensive income (loss), net of income taxes
Unrealized (loss) gain on cash flow hedges		0	0	(1)	0
Unrealized (loss) gain on investments in unconsolidated affiliates		0	5	0	1
Unrealized gain (loss) on foreign currency translation		3	(2)	(3)	2
Other comprehensive income		3	3	(4)	3
Comprehensive income		120	247	481	787
Comprehensive income (loss) attributable to noncontrolling interests		68	(10)	(85)	57
Comprehensive income attributable to common shareholders/membership interest		52	257	566	730
Commonwealth Edison Co [Member]
Operating revenues
Revenues from alternative revenue programs		(38)	(56)	(51)	(98)
Operating revenues from affiliates		15	4	31	13
Total operating revenues		1,643	1,583	4,499	4,342
Operating expenses
Purchased power and/or fuel from affiliates		71	83	252	270
Operating and maintenance		252	267	964	771
Operating and maintenance from affiliates		69	73	209	196
Depreciation and amortization		294	259	841	767
Taxes other than income taxes		81	80	227	228
Total operating expenses		1,302	1,256	3,798	3,431
Gain on sales of assets and businesses		0	1	0	4
Operating income		341	328	701	915
Other income and (deductions)
Interest expense, net		(92)	(87)	(277)	(258)
Interest expense to affiliates		(3)	(4)	(10)	(10)
Other, net		10	8	32	27
Total other income and (deductions)		(85)	(83)	(255)	(241)
Income before income taxes		256	245	446	674
Income taxes		60	45	142	130
Net income (loss)		196	200	304	544
Other comprehensive income (loss), net of income taxes
Comprehensive income		196	200	304	544
PECO Energy Co [Member]
Operating revenues
Revenues from alternative revenue programs		5	(11)	10	(16)
Operating revenues from affiliates		3	1	7	4
Total operating revenues		813	778	2,306	2,333
Operating expenses
Purchased power and/or fuel from affiliates		67	43	144	122
Operating and maintenance		214	182	628	531
Operating and maintenance from affiliates		37	37	114	112
Depreciation and amortization		85	83	259	247
Taxes other than income taxes		53	47	131	126
Total operating expenses		658	595	1,900	1,783
Operating income		155	183	406	550
Other income and (deductions)
Interest expense, net		(36)	(30)	(100)	(91)
Interest expense to affiliates		(3)	(3)	(8)	(9)
Other, net		6	4	12	11
Total other income and (deductions)		(33)	(29)	(96)	(89)
Income before income taxes		122	154	310	461
Income taxes		(16)	14	(7)	51
Net income (loss)		138	140	317	410
Other comprehensive income (loss), net of income taxes
Comprehensive income		138	140	317	410
PECO Energy Co [Member] | Retained Earnings [Member]
Other income and (deductions)
Net income (loss)		138	140
Baltimore Gas and Electric Company [Member]
Operating revenues
Revenues from alternative revenue programs		(9)	(5)	(10)	11
Operating revenues from affiliates		6	6	16	18
Total operating revenues		731	703	2,284	2,327
Operating expenses
Purchased power and/or fuel from affiliates		83	64	249	196
Operating and maintenance		152	157	445	451
Operating and maintenance from affiliates		39	39	122	118
Depreciation and amortization		133	116	405	368
Taxes other than income taxes		68	65	200	195
Total operating expenses		642	612	1,903	1,936
Operating income		89	91	381	391
Other income and (deductions)
Interest expense, net		(34)	(31)	(99)	(89)
Other, net		6	7	17	18
Total other income and (deductions)		(28)	(24)	(82)	(71)
Income before income taxes		61	67	299	320
Income taxes		8	12	26	59
Net income (loss)		53	55	273	261
Other comprehensive income (loss), net of income taxes
Comprehensive income		53	55	273	261
Baltimore Gas and Electric Company [Member] | Retained Earnings [Member]
Other income and (deductions)
Net income (loss)		53	55
Pepco Holdings LLC [Member]
Operating revenues
Revenues from alternative revenue programs		31	(9)	(15)	4
Operating revenues from affiliates		6	4	13	11
Total operating revenues		1,368	1,380	3,554	3,700
Operating expenses
Purchased power and/or fuel from affiliates		106	83	288	254
Operating and maintenance		237	254	702	706
Operating and maintenance from affiliates		38	36	111	105
Depreciation and amortization		200	193	585	562
Taxes other than income taxes		121	122	343	342
Total operating expenses		1,102	1,124	3,057	3,106
Gain on sales of assets and businesses		0	0	2	0
Operating income		266	256	499	594
Other income and (deductions)
Interest expense, net		(67)	(66)	(201)	(197)
Other, net		16	13	42	39
Total other income and (deductions)		(51)	(53)	(159)	(158)
Income before income taxes		215	203	340	436
Income taxes		(1)	14	(77)	25
Equity in losses of unconsolidated affiliates		0	0	1	1
Net income (loss)		216	189	418	412
Other comprehensive income (loss), net of income taxes
Comprehensive income attributable to common shareholders/membership interest		216	189	418	412
Potomac Electric Power Company [Member]
Operating revenues
Revenues from alternative revenue programs		18	(3)	20	10
Operating revenues from affiliates		3	2	6	5
Total operating revenues		611	642	1,650	1,748
Operating expenses
Purchased power and/or fuel from affiliates		80	65	219	188
Operating and maintenance		57	85	184	208
Operating and maintenance from affiliates		49	50	152	156
Depreciation and amortization		96	95	282	281
Taxes other than income taxes		100	104	279	286
Total operating expenses		465	515	1,364	1,444
Operating income		146	127	286	304
Other income and (deductions)
Interest expense, net		(35)	(33)	(103)	(100)
Other, net		10	9	28	22
Total other income and (deductions)		(25)	(24)	(75)	(78)
Income before income taxes		121	103	211	226
Income taxes		3	5	(16)	9
Net income (loss)		118	98	227	217
Other comprehensive income (loss), net of income taxes
Comprehensive income		118	98	227	217
Potomac Electric Power Company [Member] | Retained Earnings [Member]
Other income and (deductions)
Net income (loss)		118	98
Delmarva Power and Light Company [Member]
Operating revenues
Revenues from alternative revenue programs		8	(6)	(15)	(6)
Operating revenues from affiliates		3	1	7	5
Total operating revenues		337	319	954	987
Operating expenses
Purchased power and/or fuel from affiliates		21	14	60	50
Operating and maintenance		64	43	160	127
Operating and maintenance from affiliates		37	37	112	113
Depreciation and amortization		48	46	143	138
Taxes other than income taxes		16	15	49	43
Total operating expenses		296	268	843	820
Operating income		41	51	111	167
Other income and (deductions)
Interest expense, net		(15)	(15)	(47)	(45)
Other, net		2	2	7	10
Total other income and (deductions)		(13)	(13)	(40)	(35)
Income before income taxes		28	38	71	132
Income taxes		1	5	(20)	16
Net income (loss)		27	33	91	116
Other comprehensive income (loss), net of income taxes
Comprehensive income		27	33	91	116
Delmarva Power and Light Company [Member] | Retained Earnings [Member]
Other income and (deductions)
Net income (loss)		27	33
Atlantic City Electric Company [Member]
Operating revenues
Revenues from alternative revenue programs		5	1	(20)	0
Operating revenues from affiliates		1	1	3	2
Total operating revenues		420	419	952	966
Operating expenses
Purchased power and/or fuel from affiliates		4	3	9	16
Operating and maintenance		45	54	140	142
Operating and maintenance from affiliates		32	32	98	99
Depreciation and amortization		48	43	134	114
Taxes other than income taxes		2	1	6	4
Total operating expenses		338	340	847	838
Gain on sales of assets and businesses		0	0	2	0
Operating income		82	79	107	128
Other income and (deductions)
Interest expense, net		(15)	(15)	(45)	(44)
Other, net		1	1	5	5
Total other income and (deductions)		(14)	(14)	(40)	(39)
Income before income taxes		68	65	67	89
Income taxes		(7)	2	(39)	2
Net income (loss)		75	63	106	87
Other comprehensive income (loss), net of income taxes
Comprehensive income		75	63	106	87
Atlantic City Electric Company [Member] | Retained Earnings [Member]
Other income and (deductions)
Net income (loss)		75	63
Generation commodities and services
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,330	4,499	12,344	13,436
Operating expenses
Purchased power and/or fuel		2,311	2,648	6,967	8,142
Generation commodities and services | Exelon Generation Co L L C [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,328	4,499	12,340	13,436
Operating expenses
Purchased power and/or fuel		2,311	2,648	6,967	8,141
Rate-regulated utility revenues
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,533	4,510	12,643	12,758
Operating expenses
Purchased power and/or fuel		1,303	1,304	3,439	3,589
Electricity, US Regulated
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		4,365	4,268	11,585	11,609
Electricity, US Regulated | Commonwealth Edison Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		1,666	1,635	4,519	4,427
Operating expenses
Purchased power and/or fuel		535	494	1,305	1,199
Electricity, US Regulated | PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		751	726	1,931	1,914
Operating expenses
Purchased power and/or fuel		190	185	495	461
Electricity, US Regulated | Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		649	623	1,775	1,814
Operating expenses
Purchased power and/or fuel		155	159	376	480
Electricity, US Regulated | Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		1,308	1,365	3,440	3,570
Operating expenses
Purchased power and/or fuel		393	428	979	1,086
Electricity, US Regulated | Potomac Electric Power Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		590	643	1,624	1,733
Operating expenses
Purchased power and/or fuel		83	116	248	325
Electricity, US Regulated | Delmarva Power and Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		303	304	846	872
Operating expenses
Purchased power and/or fuel		103	105	270	298
Electricity, US Regulated | Atlantic City Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		414	417	969	964
Operating expenses
Purchased power and/or fuel		207	207	460	463
Natural Gas, US Regulated
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		159	163	990	1,046
Natural Gas, US Regulated | PECO Energy Co [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		54	62	358	431
Operating expenses
Purchased power and/or fuel		12	18	129	184
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		85	79	503	484
Operating expenses
Purchased power and/or fuel		12	12	106	128
Natural Gas, US Regulated | Pepco Holdings LLC [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		23	20	116	115
Operating expenses
Purchased power and/or fuel		7	8	49	51
Natural Gas, US Regulated | Delmarva Power and Light Company [Member]
Operating revenues
Revenue from Contract with Customer, Including Assessed Tax		23	20	116	116
Operating expenses
Purchased power and/or fuel		$ 7	$ 8	$ 49	$ 51
[1]	The number of stock options not included in the calculation of diluted common shares outstanding due to their antidilutive effect was approximately 1 million for the three and nine months ended September 30, 2020, and less than 1 million for the three and nine months ended September 30, 2019.

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities
Net income (loss)	$ 1,519	$ 2,220
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	4,419	4,393
Asset impairments	567	174
Gain on sales of assets and businesses	(16)	(15)
Deferred income taxes and amortization of investment tax credits	164	412
Net fair value changes related to derivatives	(448)	96
Net realized and unrealized losses (gains) on NDT funds	(59)	(467)
Other non-cash operating activities	988	460
Changes in assets and liabilities:
Accounts receivable	1,195	445
Inventories	(67)	(94)
Accounts payable and accrued expenses	(519)	(671)
Option premiums (paid) received, net	(131)	13
Collateral received (posted), net	644	(254)
Income taxes	(31)	143
Pension and non-pension postretirement benefit contributions	(580)	(377)
Other assets and liabilities	(3,423)	(1,079)
Net cash flows provided by operating activities	4,222	5,399
Cash flows from investing activities
Capital expenditures	(5,606)	(5,259)
Proceeds from NDT fund sales	3,370	8,443
Investment in NDT funds	(3,438)	(8,437)
Collection of deferred purchase price	2,518	0
Proceeds from sales of assets and businesses	46	17
Other investing activities	(2)	21
Net cash flows provided by (used in) investing activities	(3,112)	(5,215)
Cash flows from financing activities
Changes in short-term borrowings	(689)	430
Proceeds from short-term borrowings with maturities greater than 90 days	500	0
Repayments on short-term borrowings with maturities greater than 90 days	0	(125)
Issuance of long-term debt	6,756	1,576
Retirement of long-term debt	(5,158)	(644)
Dividends paid on common stock	(1,119)	(1,055)
Proceeds from employee stock plans	62	94
Other financing activities	(104)	(63)
Net cash flows provided by (used in) financing activities	248	213
Increase (Decrease) in cash, cash equivalents and restricted cash	1,358	397
Cash, cash equivalents and restricted cash at beginning of period	1,122	1,781
Cash, cash equivalents and restricted cash at end of period	2,480	2,178
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(11)	(96)
Increase in deferred purchase price	3,275	0
Increase in PPE related to ARO update	775	344
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income (loss)	485	784
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	2,266	2,377
Asset impairments	552	174
Gain on sales of assets and businesses	(12)	(15)
Deferred income taxes and amortization of investment tax credits	(51)	201
Net fair value changes related to derivatives	(448)	102
Net realized and unrealized losses (gains) on NDT funds	(59)	(467)
Other non-cash operating activities	293	(95)
Changes in assets and liabilities:
Accounts receivable	1,463	395
Receivables from and payables to affiliates, net	75	(12)
Inventories	(65)	(36)
Accounts payable and accrued expenses	(619)	(428)
Option premiums (paid) received, net	(131)	13
Collateral received (posted), net	640	(292)
Income taxes	112	327
Pension and non-pension postretirement benefit contributions	(249)	(165)
Other assets and liabilities	(2,889)	(390)
Net cash flows provided by operating activities	1,363	2,473
Cash flows from investing activities
Capital expenditures	(1,212)	(1,282)
Proceeds from NDT fund sales	3,370	8,443
Investment in NDT funds	(3,438)	(8,437)
Collection of deferred purchase price	2,518	0
Proceeds from sales of assets and businesses	46	17
Other investing activities	5	(6)
Net cash flows provided by (used in) investing activities	1,289	(1,265)
Cash flows from financing activities
Changes in short-term borrowings	(280)	0
Proceeds from short-term borrowings with maturities greater than 90 days	500	0
Issuance of long-term debt	2,405	41
Retirement of long-term debt	(3,613)	(196)
Changes in Exelon/PHI intercompany money pool	0	(100)
Distributions to member	(1,406)	(674)
Contributions from member	64	0
Other financing activities	(48)	(37)
Net cash flows provided by (used in) financing activities	(2,378)	(966)
Increase (Decrease) in cash, cash equivalents and restricted cash	274	242
Cash, cash equivalents and restricted cash at beginning of period	449	903
Cash, cash equivalents and restricted cash at end of period	723	1,145
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(77)	(24)
Increase in deferred purchase price	3,275	0
Increase in PPE related to ARO update	775	342
PECO Energy Co [Member]
Cash flows from operating activities
Net income (loss)	317	410
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	259	247
Deferred income taxes and amortization of investment tax credits	(5)	6
Other non-cash operating activities	27	28
Changes in assets and liabilities:
Accounts receivable	(2)	46
Receivables from and payables to affiliates, net	(7)	(12)
Inventories	(3)	(3)
Accounts payable and accrued expenses	32	(32)
Income taxes	48	(15)
Pension and non-pension postretirement benefit contributions	(18)	(26)
Other assets and liabilities	(13)	(111)
Net cash flows provided by operating activities	635	538
Cash flows from investing activities
Capital expenditures	(824)	(675)
Changes in Exelon/PHI intercompany money pool	68	0
Other investing activities	4	7
Net cash flows provided by (used in) investing activities	(752)	(668)
Cash flows from financing activities
Issuance of long-term debt	350	325
Dividends paid on common stock	(255)	(268)
Contributions from parent	248	174
Other financing activities	(4)	(6)
Net cash flows provided by (used in) financing activities	339	225
Increase (Decrease) in cash, cash equivalents and restricted cash	222	95
Cash, cash equivalents and restricted cash at beginning of period	27	135
Cash, cash equivalents and restricted cash at end of period	249	230
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	28	42
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income (loss)	273	261
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	405	368
Deferred income taxes and amortization of investment tax credits	35	66
Other non-cash operating activities	82	63
Changes in assets and liabilities:
Accounts receivable	(19)	110
Receivables from and payables to affiliates, net	(27)	(14)
Inventories	2	(5)
Accounts payable and accrued expenses	53	(28)
Collateral received (posted), net	0	(5)
Income taxes	46	(43)
Pension and non-pension postretirement benefit contributions	(74)	(45)
Other assets and liabilities	(50)	(65)
Net cash flows provided by operating activities	726	663
Cash flows from investing activities
Capital expenditures	(838)	(842)
Other investing activities	0	4
Net cash flows provided by (used in) investing activities	(838)	(838)
Cash flows from financing activities
Changes in short-term borrowings	(76)	(35)
Issuance of long-term debt	400	400
Dividends paid on common stock	(186)	(169)
Contributions from parent	284	104
Other financing activities	(8)	(7)
Net cash flows provided by (used in) financing activities	414	293
Increase (Decrease) in cash, cash equivalents and restricted cash	302	118
Cash, cash equivalents and restricted cash at beginning of period	25	13
Cash, cash equivalents and restricted cash at end of period	327	131
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	7	6
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income (loss)	418	412
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	585	562
Deferred income taxes and amortization of investment tax credits	(99)	8
Other non-cash operating activities	115	122
Changes in assets and liabilities:
Accounts receivable	(121)	(64)
Receivables from and payables to affiliates, net	(26)	1
Inventories	(2)	(36)
Accounts payable and accrued expenses	57	0
Income taxes	(14)	(11)
Pension and non-pension postretirement benefit contributions	(35)	(15)
Other assets and liabilities	(61)	(102)
Net cash flows provided by operating activities	817	877
Cash flows from investing activities
Capital expenditures	(1,072)	(1,006)
Other investing activities	3	3
Net cash flows provided by (used in) investing activities	(1,069)	(1,003)
Cash flows from financing activities
Changes in short-term borrowings	(208)	78
Repayments on short-term borrowings with maturities greater than 90 days	0	(125)
Issuance of long-term debt	601	410
Retirement of long-term debt	(119)	(130)
Changes in Exelon/PHI intercompany money pool	9	10
Distributions to member	(451)	(429)
Contributions from member	493	283
Other financing activities	(10)	(5)
Net cash flows provided by (used in) financing activities	315	92
Increase (Decrease) in cash, cash equivalents and restricted cash	63	(34)
Cash, cash equivalents and restricted cash at beginning of period	181	186
Cash, cash equivalents and restricted cash at end of period	244	152
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(5)	(62)
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income (loss)	227	217
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	282	281
Deferred income taxes and amortization of investment tax credits	(36)	12
Other non-cash operating activities	6	43
Changes in assets and liabilities:
Accounts receivable	(61)	(49)
Receivables from and payables to affiliates, net	(23)	4
Inventories	2	(23)
Accounts payable and accrued expenses	36	(12)
Income taxes	(11)	(23)
Pension and non-pension postretirement benefit contributions	(8)	(10)
Other assets and liabilities	15	(55)
Net cash flows provided by operating activities	429	385
Cash flows from investing activities
Capital expenditures	(512)	(455)
Changes in Exelon/PHI intercompany money pool	(117)	0
Other investing activities	(3)	2
Net cash flows provided by (used in) investing activities	(632)	(453)
Cash flows from financing activities
Changes in short-term borrowings	(82)	(28)
Issuance of long-term debt	300	260
Retirement of long-term debt	(2)	(118)
Dividends paid on common stock	(174)	(173)
Contributions from parent	262	129
Other financing activities	(6)	(3)
Net cash flows provided by (used in) financing activities	298	67
Increase (Decrease) in cash, cash equivalents and restricted cash	95	(1)
Cash, cash equivalents and restricted cash at beginning of period	63	53
Cash, cash equivalents and restricted cash at end of period	158	52
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(23)	(7)
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income (loss)	91	116
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	138
Deferred income taxes and amortization of investment tax credits	(20)	(2)
Other non-cash operating activities	47	21
Changes in assets and liabilities:
Accounts receivable	3	29
Receivables from and payables to affiliates, net	(5)	(7)
Inventories	(3)	(7)
Accounts payable and accrued expenses	21	3
Income taxes	(12)	11
Pension and non-pension postretirement benefit contributions	(1)	(1)
Other assets and liabilities	(25)	(22)
Net cash flows provided by operating activities	239	279
Cash flows from investing activities
Capital expenditures	(278)	(245)
Other investing activities	(3)	1
Net cash flows provided by (used in) investing activities	(281)	(244)
Cash flows from financing activities
Changes in short-term borrowings	(56)	57
Issuance of long-term debt	178	0
Retirement of long-term debt	(79)	0
Dividends paid on common stock	(99)	(105)
Contributions from parent	112	0
Other financing activities	(1)	0
Net cash flows provided by (used in) financing activities	55	(48)
Increase (Decrease) in cash, cash equivalents and restricted cash	13	(13)
Cash, cash equivalents and restricted cash at beginning of period	13	24
Cash, cash equivalents and restricted cash at end of period	26	11
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	8	(13)
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income (loss)	106	87
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	134	114
Deferred income taxes and amortization of investment tax credits	(40)	2
Other non-cash operating activities	34	21
Changes in assets and liabilities:
Accounts receivable	(62)	(44)
Receivables from and payables to affiliates, net	2	(4)
Inventories	0	(4)
Accounts payable and accrued expenses	16	27
Income taxes	4	5
Pension and non-pension postretirement benefit contributions	(3)	0
Other assets and liabilities	(53)	(18)
Net cash flows provided by operating activities	138	186
Cash flows from investing activities
Capital expenditures	(281)	(300)
Other investing activities	5	0
Net cash flows provided by (used in) investing activities	(276)	(300)
Cash flows from financing activities
Changes in short-term borrowings	(70)	49
Repayments on short-term borrowings with maturities greater than 90 days	0	(125)
Issuance of long-term debt	123	150
Retirement of long-term debt	(38)	(13)
Changes in Exelon/PHI intercompany money pool	117	0
Dividends paid on common stock	(111)	(100)
Contributions from parent	117	155
Other financing activities	(1)	(1)
Net cash flows provided by (used in) financing activities	137	115
Increase (Decrease) in cash, cash equivalents and restricted cash	(1)	1
Cash, cash equivalents and restricted cash at beginning of period	28	30
Cash, cash equivalents and restricted cash at end of period	27	31
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	9	(37)
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income (loss)	304	544
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	841	767
Asset impairments	15	0
Deferred income taxes and amortization of investment tax credits	205	115
Other non-cash operating activities	354	180
Changes in assets and liabilities:
Accounts receivable	(104)	(38)
Receivables from and payables to affiliates, net	(13)	(27)
Inventories	(2)	(16)
Accounts payable and accrued expenses	21	(132)
Collateral received (posted), net	3	43
Income taxes	(22)	25
Pension and non-pension postretirement benefit contributions	(145)	(71)
Other assets and liabilities	(380)	(245)
Net cash flows provided by operating activities	1,077	1,145
Cash flows from investing activities
Capital expenditures	(1,583)	(1,413)
Other investing activities	0	25
Net cash flows provided by (used in) investing activities	(1,583)	(1,388)
Cash flows from financing activities
Changes in short-term borrowings	11	387
Issuance of long-term debt	1,000	400
Retirement of long-term debt	(500)	(300)
Dividends paid on common stock	(374)	(380)
Contributions from parent	488	187
Other financing activities	(14)	(10)
Net cash flows provided by (used in) financing activities	611	284
Increase (Decrease) in cash, cash equivalents and restricted cash	105	41
Cash, cash equivalents and restricted cash at beginning of period	403	330
Cash, cash equivalents and restricted cash at end of period	508	371
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	$ 49	$ (52)

Consolidated Balance Sheets (Un

Consolidated Balance Sheets (Unaudited) - USD ($) shares in Millions, $ in Millions		Sep. 30, 2020	Dec. 31, 2019
Current Assets
Cash and cash equivalents		$ 1,858	$ 587
Restricted cash and cash equivalents		485	358
Accounts receivable
Customer accounts receivable		3,150	4,835
Customer allowance for credit losses		(358)	(243)
Customer accounts receivable, net		2,792	4,592
Other accounts receivable		1,576	1,631
Other allowance for credit losses		(75)	(48)
Other accounts receivable, net		1,501	1,583
Mark-to-market derivative assets, current		472	679
Unamortized energy contract assets, current		41	47
Inventories, net
Fossil fuel and emission allowances		311	312
Materials and supplies		1,405	1,456
Regulatory assets, current		1,170	1,170
Other		2,277	1,253
Total current assets		12,312	12,037
Accumulated depreciation and amortization		25,582	23,979
Property, plant and equipment, net		82,561	80,233
Deferred debits and other assets
Regulatory assets, noncurrent		8,485	8,335
Nuclear decommissioning trust funds		13,432	13,190
Investments		444	464
Goodwill		6,677	6,677
Mark-to-market derivative assets, noncurrent		383	508
Unamortized energy contract assets, noncurrent		308	336
Other		3,165	3,197
Total deferred debits and other assets		32,894	32,707
Total assets	[1]	127,767	124,977
Current Liabilities
Short-term borrowings		1,181	1,370
Long-term debt due within one year		2,077	4,710
Accounts payable		3,182	3,560
Accrued expenses		1,879	1,981
Payables to affiliates, current		5	5
Regulatory liabilities, current		575	406
Mark-to-market derivative liabilities, current		177	247
Unamortized energy contract liabilities, current		107	132
Renewable energy credit obligation		604	443
Other		1,475	1,331
Total current liabilities		11,262	14,185
Long-term debt		35,512	31,329
Long-term debt to financing trusts		390	390
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		13,058	12,351
Asset retirement obligations, noncurrent		11,989	10,846
Pension obligations		3,648	4,247
Non-pension postretirement benefit obligations		2,128	2,076
Spent nuclear fuel obligation		1,207	1,199
Regulatory liabilities, noncurrent		9,495	9,986
Mark-to-market derivative liabilities, noncurrent		396	393
Unamortized energy contract liabilities, noncurrent		266	338
Other		3,313	3,064
Total deferred credits and other liabilities		45,500	44,500
Total liabilities	[1]	92,664	90,404
Commitments and contingencies
Common stock, Shares, Outstanding		976	973
Shareholders' equity
Common stock, Shares Authorized		2,000	2,000
Common stock, Shares, Outstanding		976	973
Common stock		$ 19,362	$ 19,274
Treasury Stock, Shares		2	2
Treasury stock, at cost		$ (123)	$ (123)
Retained earnings/Undistributed earnings (losses)		16,749	16,267
Accumulated other comprehensive loss, net		(3,104)	(3,194)
Total shareholders’ equity		32,884	32,224
Member’s equity
Noncontrolling interests		2,219	2,349
Total equity		35,103	34,573
Total liabilities and shareholders’ equity		127,767	124,977
Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Cash and cash equivalents		148	163
Restricted cash and cash equivalents		52	88
Accounts receivable
Customer accounts receivable, net		151	151
Unamortized energy contract assets, current		22	23
Inventories, net
Materials and supplies		241	227
Other		781	32
Total current assets		1,434	723
Property, plant and equipment, net		5,865	6,022
Deferred debits and other assets
Nuclear decommissioning trust funds		2,785	2,741
Unamortized energy contract assets, noncurrent		253	250
Other		49	89
Total assets		10,386	9,825
Current Liabilities
Long-term debt due within one year		134	544
Accounts payable		81	106
Accrued expenses		63	70
Unamortized energy contract liabilities, current		5	8
Other		26	3
Total current liabilities		309	731
Long-term debt		913	527
Deferred credits and other liabilities
Asset retirement obligations, noncurrent		2,210	2,128
Unamortized energy contract liabilities, noncurrent		1	1
Other		106	89
Total liabilities		3,539	3,476
Variable Interest Entity, Primary Beneficiary [Member] | Asset Pledged as Collateral [Member]
Deferred debits and other assets
Total assets		10,102	9,532
Variable Interest Entity, Primary Beneficiary [Member] | Nonrecourse [Member]
Deferred credits and other liabilities
Total liabilities		3,531	3,473
Exelon Generation Co L L C [Member]
Current Assets
Cash and cash equivalents		623	303
Restricted cash and cash equivalents		100	146
Accounts receivable
Customer accounts receivable		1,089	2,973
Customer allowance for credit losses		(33)	(80)
Customer accounts receivable, net		1,056	2,893
Other accounts receivable		311	619
Other accounts receivable, net		311	619
Mark-to-market derivative assets, current		471	675
Receivables from affiliates, current		109	190
Unamortized energy contract assets, current		41	47
Inventories, net
Fossil fuel and emission allowances		238	236
Materials and supplies		971	1,026
Renewable energy credits, current		576	336
Other		1,387	605
Total current assets		5,883	7,076
Accumulated depreciation and amortization		12,588	12,017
Property, plant and equipment, net		23,709	24,193
Deferred debits and other assets
Nuclear decommissioning trust funds		13,432	13,190
Investments		197	235
Goodwill		47	47
Mark-to-market derivative assets, noncurrent		383	508
Prepaid pension asset		1,584	1,438
Unamortized energy contract assets, noncurrent		308	336
Deferred income taxes		9	12
Other		1,820	1,960
Total deferred debits and other assets		17,780	17,726
Total assets	[2]	47,372	48,995
Current Liabilities
Short-term borrowings		540	320
Long-term debt due within one year		203	2,624
Long-term debt to affiliates due within one year		551	558
Accounts payable		1,109	1,692
Accrued expenses		699	786
Payables to affiliates, current		113	117
Mark-to-market derivative liabilities, current		147	215
Unamortized energy contract liabilities, current		8	17
Renewable energy credit obligation		604	443
Other		437	517
Total current liabilities		4,411	7,289
Long-term debt		5,677	4,464
Long-term debt to affiliates		325	328
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		3,715	3,752
Asset retirement obligations, noncurrent		11,744	10,603
Non-pension postretirement benefit obligations		864	878
Spent nuclear fuel obligation		1,207	1,199
Payables to affiliates, noncurrent		2,888	3,103
Mark-to-market derivative liabilities, noncurrent		121	123
Unamortized energy contract liabilities, noncurrent		8	11
Other		1,488	1,415
Total deferred credits and other liabilities		22,035	21,084
Total liabilities	[2]	32,448	33,165
Commitments and contingencies
Shareholders' equity
Retained earnings/Undistributed earnings (losses)		3,114	3,950
Accumulated other comprehensive loss, net		(36)	(32)
Member’s equity
Membership interest		9,633	9,566
Total members' equity		12,711	13,484
Noncontrolling interests		2,213	2,346
Total equity		14,924	15,830
Total liabilities and shareholders’ equity		47,372	48,995
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Cash and cash equivalents		148	163
Restricted cash and cash equivalents		48	85
Accounts receivable
Customer accounts receivable, net		151	151
Unamortized energy contract assets, current		22	23
Inventories, net
Materials and supplies		241	227
Other		776	31
Total current assets		1,425	719
Property, plant and equipment, net		5,865	6,022
Deferred debits and other assets
Nuclear decommissioning trust funds		2,785	2,741
Unamortized energy contract assets, noncurrent		253	250
Other		38	73
Total assets		10,366	9,805
Current Liabilities
Long-term debt due within one year		109	523
Accounts payable		81	106
Accrued expenses		63	70
Unamortized energy contract liabilities, current		5	8
Other		26	3
Total current liabilities		284	710
Long-term debt		906	504
Deferred credits and other liabilities
Asset retirement obligations, noncurrent		2,210	2,128
Unamortized energy contract liabilities, noncurrent		1	1
Other		106	89
Total liabilities		3,507	3,432
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Asset Pledged as Collateral [Member]
Deferred debits and other assets
Total assets		10,082	9,512
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Nonrecourse [Member]
Deferred credits and other liabilities
Total liabilities		3,499	3,429
Commonwealth Edison Co [Member]
Current Assets
Cash and cash equivalents		76	90
Restricted cash and cash equivalents		305	150
Accounts receivable
Customer accounts receivable		707	604
Customer allowance for credit losses		(105)	(59)
Customer accounts receivable, net		602	545
Other accounts receivable		309	306
Other allowance for credit losses		(27)	(20)
Other accounts receivable, net		282	286
Receivables from affiliates, current		20	28
Inventories, net
Inventories, net		160	159
Regulatory assets, current		274	281
Other		59	44
Total current assets		1,778	1,583
Accumulated depreciation and amortization		5,533	5,168
Property, plant and equipment, net		24,081	23,107
Deferred debits and other assets
Regulatory assets, noncurrent		1,742	1,480
Investments		6	6
Goodwill		2,625	2,625
Receivables from affiliates, noncurrent		2,445	2,622
Prepaid pension asset		1,050	995
Other		516	347
Total deferred debits and other assets		8,384	8,075
Total assets		34,243	32,765
Current Liabilities
Short-term borrowings		141	130
Long-term debt due within one year		350	500
Accounts payable		671	527
Accrued expenses		282	385
Payables to affiliates, current		82	103
Customer deposits		100	118
Regulatory liabilities, current		251	200
Mark-to-market derivative liabilities, current		30	32
Deferred Prosecution Agreement payments		200	0
Other		140	122
Total current liabilities		2,247	2,117
Long-term debt		8,631	7,991
Long-term debt to financing trusts		205	205
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		4,299	4,021
Asset retirement obligations, noncurrent		126	128
Non-pension postretirement benefit obligations		175	180
Regulatory liabilities, noncurrent		6,420	6,542
Mark-to-market derivative liabilities, noncurrent		274	269
Other		771	635
Total deferred credits and other liabilities		12,065	11,775
Total liabilities		23,148	22,088
Commitments and contingencies
Shareholders' equity
Common stock		1,588	1,588
Other paid-in capital		8,060	7,572
Retained deficit unappropriated		(1,700)	(1,639)
Retained earnings appropriated		3,147	3,156
Total shareholders’ equity		11,095	10,677
Member’s equity
Total liabilities and shareholders’ equity		34,243	32,765
PECO Energy Co [Member]
Current Assets
Cash and cash equivalents		242	21
Restricted cash and cash equivalents		7	6
Accounts receivable
Customer accounts receivable		412	412
Customer allowance for credit losses		(96)	(55)
Customer accounts receivable, net		316	357
Other accounts receivable		126	145
Other allowance for credit losses		(7)	(7)
Other accounts receivable, net		119	138
Receivables from affiliates, current		0	1
Receivable from Exelon/PHI intercompany money pool		0	68
Inventories, net
Fossil fuel and emission allowances		36	36
Materials and supplies		37	35
Prepaid utility taxes		35	0
Regulatory assets, current		38	41
Other		23	19
Total current assets		853	722
Accumulated depreciation and amortization		3,804	3,718
Property, plant and equipment, net		9,912	9,292
Deferred debits and other assets
Regulatory assets, noncurrent		692	554
Investments		29	27
Receivables from affiliates, noncurrent		443	480
Prepaid pension asset		377	365
Other		28	29
Total deferred debits and other assets		1,569	1,455
Total assets		12,334	11,469
Current Liabilities
Long-term debt due within one year		300	0
Accounts payable		443	387
Accrued expenses		124	101
Payables to affiliates, current		47	55
Customer deposits		63	69
Regulatory liabilities, current		129	91
Other		27	19
Total current liabilities		1,133	722
Long-term debt		3,453	3,405
Long-term debt to financing trusts		184	184
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,194	2,080
Asset retirement obligations, noncurrent		29	28
Non-pension postretirement benefit obligations		286	288
Regulatory liabilities, noncurrent		471	510
Other		96	74
Total deferred credits and other liabilities		3,076	2,980
Total liabilities		7,846	7,291
Commitments and contingencies
Shareholders' equity
Common stock		3,014	2,766
Retained earnings/Undistributed earnings (losses)		1,474	1,412
Total shareholders’ equity		4,488	4,178
Member’s equity
Total liabilities and shareholders’ equity		12,334	11,469
Baltimore Gas and Electric Company [Member]
Current Assets
Cash and cash equivalents		326	24
Restricted cash and cash equivalents		1	1
Accounts receivable
Customer accounts receivable		357	329
Customer allowance for credit losses		(35)	(12)
Customer accounts receivable, net		322	317
Other accounts receivable		114	152
Other allowance for credit losses		(9)	(5)
Other accounts receivable, net		105	147
Receivables from affiliates, current		0	1
Inventories, net
Fossil fuel and emission allowances		31	30
Materials and supplies		43	46
Prepaid utility taxes		0	78
Regulatory assets, current		167	183
Other		6	6
Total current assets		1,001	833
Accumulated depreciation and amortization		3,963	3,834
Property, plant and equipment, net		9,541	8,990
Deferred debits and other assets
Regulatory assets, noncurrent		473	454
Investments		8	7
Prepaid pension asset		283	264
Other		64	86
Total deferred debits and other assets		828	811
Total assets		11,370	10,634
Current Liabilities
Short-term borrowings		0	76
Accounts payable		273	243
Accrued expenses		178	152
Payables to affiliates, current		39	66
Customer deposits		115	120
Regulatory liabilities, current		39	33
Other		76	63
Total current liabilities		720	753
Long-term debt		3,664	3,270
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		1,504	1,396
Asset retirement obligations, noncurrent		24	22
Non-pension postretirement benefit obligations		190	199
Regulatory liabilities, noncurrent		1,121	1,195
Other		93	116
Total deferred credits and other liabilities		2,932	2,928
Total liabilities		7,316	6,951
Commitments and contingencies
Shareholders' equity
Common stock		2,191	1,907
Retained earnings/Undistributed earnings (losses)		1,863	1,776
Total shareholders’ equity		4,054	3,683
Member’s equity
Total liabilities and shareholders’ equity		11,370	10,634
Pepco Holdings LLC [Member]
Current Assets
Cash and cash equivalents		196	131
Restricted cash and cash equivalents		38	36
Accounts receivable
Customer accounts receivable		584	516
Customer allowance for credit losses		(89)	(37)
Customer accounts receivable, net		495	479
Other accounts receivable		244	190
Other allowance for credit losses		(32)	(16)
Other accounts receivable, net		212	174
Receivables from affiliates, current		0	1
Inventories, net
Fossil fuel and emission allowances		7	8
Materials and supplies		194	190
Regulatory assets, current		440	412
Other		52	49
Total current assets		1,634	1,480
Accumulated depreciation and amortization		1,692	1,213
Property, plant and equipment, net		14,954	14,296
Deferred debits and other assets
Regulatory assets, noncurrent		1,972	2,061
Investments		138	135
Goodwill		4,005	4,005
Prepaid pension asset		381	406
Deferred income taxes		10	13
Other		300	323
Total deferred debits and other assets		6,806	6,943
Total assets	[3]	23,394	22,719
Current Liabilities
Short-term borrowings		0	208
Long-term debt due within one year		349	103
Accounts payable		507	462
Accrued expenses		279	296
Payables to affiliates, current		71	98
Borrowings from Exelon/PHI intercompany money pool		21	12
Customer deposits		111	117
Regulatory liabilities, current		143	70
Unamortized energy contract liabilities, current		98	115
Other		144	131
Total current liabilities		1,723	1,612
Long-term debt		6,671	6,460
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,409	2,278
Asset retirement obligations, noncurrent		58	57
Non-pension postretirement benefit obligations		85	93
Regulatory liabilities, noncurrent		1,471	1,707
Unamortized energy contract liabilities, noncurrent		258	327
Other		650	577
Total deferred credits and other liabilities		4,931	5,039
Total liabilities	[3]	13,325	13,111
Commitments and contingencies
Shareholders' equity
Retained earnings/Undistributed earnings (losses)		(43)	(10)
Member’s equity
Membership interest		10,112	9,618
Total members' equity		10,069	9,608
Total equity		10,069	9,608
Total liabilities and shareholders’ equity		23,394	22,719
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		4	3
Accounts receivable
Customer accounts receivable, net		0	0
Unamortized energy contract assets, current		0	0
Inventories, net
Materials and supplies		0	0
Other		5	1
Total current assets		9	4
Property, plant and equipment, net		0	0
Deferred debits and other assets
Nuclear decommissioning trust funds		0	0
Unamortized energy contract assets, noncurrent		0	0
Other		11	16
Total assets		20	20
Current Liabilities
Long-term debt due within one year		25	21
Accounts payable		0	0
Accrued expenses		0	0
Unamortized energy contract liabilities, current		0	0
Other		0	0
Total current liabilities		25	21
Long-term debt		7	23
Deferred credits and other liabilities
Asset retirement obligations, noncurrent		0	0
Unamortized energy contract liabilities, noncurrent		0	0
Other		0	0
Total liabilities		32	44
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Asset Pledged as Collateral [Member]
Deferred debits and other assets
Total assets		20	20
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Nonrecourse [Member]
Deferred credits and other liabilities
Total liabilities		32	44
Potomac Electric Power Company [Member]
Current Assets
Cash and cash equivalents		125	30
Restricted cash and cash equivalents		33	33
Accounts receivable
Customer accounts receivable		278	244
Customer allowance for credit losses		(35)	(13)
Customer accounts receivable, net		243	231
Other accounts receivable		129	98
Other allowance for credit losses		(13)	(7)
Other accounts receivable, net		116	91
Receivable from Exelon/PHI intercompany money pool		117	0
Inventories, net
Inventories, net		110	112
Regulatory assets, current		200	188
Other		13	11
Total current assets		957	696
Accumulated depreciation and amortization		3,651	3,517
Property, plant and equipment, net		7,236	6,909
Deferred debits and other assets
Regulatory assets, noncurrent		573	584
Investments		113	110
Prepaid pension asset		287	296
Other		61	66
Total deferred debits and other assets		1,034	1,056
Total assets		9,227	8,661
Current Liabilities
Short-term borrowings		0	82
Long-term debt due within one year		3	2
Accounts payable		206	195
Accrued expenses		144	156
Payables to affiliates, current		43	66
Customer deposits		54	57
Regulatory liabilities, current		49	8
Merger related obligation		39	39
Current portion of DC PLUG obligation		30	30
Other		29	22
Total current liabilities		597	657
Long-term debt		3,161	2,862
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		1,194	1,131
Asset retirement obligations, noncurrent		38	41
Non-pension postretirement benefit obligations		14	20
Regulatory liabilities, noncurrent		647	746
Other		354	297
Total deferred credits and other liabilities		2,247	2,235
Total liabilities		6,005	5,754
Commitments and contingencies
Shareholders' equity
Common stock		2,058	1,796
Retained earnings/Undistributed earnings (losses)		1,164	1,111
Total shareholders’ equity		3,222	2,907
Member’s equity
Total liabilities and shareholders’ equity		9,227	8,661
Delmarva Power and Light Company [Member]
Current Assets
Cash and cash equivalents		26	13
Restricted cash and cash equivalents		0	0
Accounts receivable
Customer accounts receivable		141	152
Customer allowance for credit losses		(22)	(11)
Customer accounts receivable, net		119	141
Other accounts receivable		53	42
Other allowance for credit losses		(8)	(4)
Other accounts receivable, net		45	38
Inventories, net
Fossil fuel and emission allowances		7	8
Materials and supplies		49	44
Prepaid utility taxes		17	18
Regulatory assets, current		51	52
Renewable energy credits, current		4	9
Other		3	2
Total current assets		321	325
Accumulated depreciation and amortization		1,502	1,425
Property, plant and equipment, net		4,209	4,035
Deferred debits and other assets
Regulatory assets, noncurrent		227	222
Goodwill		8	8
Prepaid pension asset		164	171
Other		63	69
Total deferred debits and other assets		462	470
Total assets		4,992	4,830
Current Liabilities
Short-term borrowings		0	56
Long-term debt due within one year		81	80
Accounts payable		126	112
Accrued expenses		50	46
Payables to affiliates, current		23	32
Customer deposits		34	36
Regulatory liabilities, current		46	37
Other		19	15
Total current liabilities		379	414
Long-term debt		1,595	1,487
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		689	655
Asset retirement obligations, noncurrent		14	12
Non-pension postretirement benefit obligations		14	16
Regulatory liabilities, noncurrent		516	574
Other		101	92
Total deferred credits and other liabilities		1,334	1,349
Total liabilities		3,308	3,250
Commitments and contingencies
Shareholders' equity
Common stock		1,089	977
Retained earnings/Undistributed earnings (losses)		595	603
Total shareholders’ equity		1,684	1,580
Member’s equity
Total liabilities and shareholders’ equity		4,992	4,830
Atlantic City Electric Company [Member]
Current Assets
Cash and cash equivalents		13	12
Restricted cash and cash equivalents		4	2
Accounts receivable
Customer accounts receivable		165	121
Customer allowance for credit losses		(32)	(13)
Customer accounts receivable, net		133	108
Other accounts receivable		65	53
Other allowance for credit losses		(11)	(5)
Other accounts receivable, net		54	48
Receivables from affiliates, current		1	4
Inventories, net
Inventories, net		34	34
Prepaid utility taxes		9	0
Regulatory assets, current		88	57
Other		4	5
Total current assets		340	270
Accumulated depreciation and amortization		1,276	1,210
Property, plant and equipment, net		3,372	3,190
Deferred debits and other assets
Regulatory assets, noncurrent		395	368
Prepaid pension asset		44	52
Other		50	53
Total deferred debits and other assets		489	473
Total assets	[4]	4,201	3,933
Current Liabilities
Short-term borrowings		0	70
Long-term debt due within one year		261	20
Accounts payable		168	144
Accrued expenses		42	42
Payables to affiliates, current		24	25
Borrowings from Exelon/PHI intercompany money pool		117	0
Customer deposits		23	25
Regulatory liabilities, current		48	25
Other		10	9
Total current liabilities		693	360
Long-term debt		1,156	1,307
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		617	577
Non-pension postretirement benefit obligations		16	17
Regulatory liabilities, noncurrent		279	357
Other		52	39
Total deferred credits and other liabilities		964	990
Total liabilities	[4]	2,813	2,657
Commitments and contingencies
Shareholders' equity
Common stock		1,271	1,154
Retained earnings/Undistributed earnings (losses)		117	122
Total shareholders’ equity		1,388	1,276
Member’s equity
Total liabilities and shareholders’ equity		4,201	3,933
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		4	3
Accounts receivable
Customer accounts receivable, net		0	0
Unamortized energy contract assets, current		0	0
Inventories, net
Materials and supplies		0	0
Other		0	0
Total current assets		4	3
Property, plant and equipment, net		0	0
Deferred debits and other assets
Nuclear decommissioning trust funds		0	0
Unamortized energy contract assets, noncurrent		0	0
Other		10	14
Total assets		14	17
Current Liabilities
Long-term debt due within one year		20	20
Accounts payable		0	0
Accrued expenses		0	0
Unamortized energy contract liabilities, current		0	0
Other		0	0
Total current liabilities		20	20
Long-term debt		6	21
Deferred credits and other liabilities
Asset retirement obligations, noncurrent		0	0
Unamortized energy contract liabilities, noncurrent		0	0
Other		0	0
Total liabilities		26	41
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Asset Pledged as Collateral [Member]
Deferred debits and other assets
Total assets		14	17
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Nonrecourse [Member]
Deferred credits and other liabilities
Total liabilities		$ 26	$ 41
[1]	Exelon’s consolidated assets include $10,102 million and $9,532 million at September 30, 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 $3,531 million and $3,473 million at September 30, 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 $10,082 million and $9,512 million at September 30, 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 $3,499 million and $3,429 million at September 30, 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 $20 million and $20 million at September 30, 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 $32 million and $44 million at September 30, 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 $14 million and $17 million at September 30, 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 $26 million and $41 million at September 30, 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 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					(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]
Common Stock, Dividends, Per Share, Declared	$ 0.36
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)	2,220							784					544						410			261			412			217			116			87
Other comprehensive income (loss), net of income taxes	$ 33				32			3
Ending balance (in shares) at Sep. 30, 2019	973,941
Ending balance at Sep. 30, 2019	$ 34,352	19,238	(123)	15,871	(2,963)	2,329
Ending Balance at Sep. 30, 2019								15,593	9,525	3,778	(36)	2,326													9,548	9,503	45
Ending Balance at Sep. 30, 2019													10,597	1,588	7,509	(1,639)	3,139		4,136	2,752	1,384	3,550	1,818	1,732				2,913	1,765	1,148	1,520	914	606	1,268	1,134	134
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Available to Common Stockholders, Basic	$ 2,164
Appropriation of retained earnings for future dividends																(157)	157	$ 0
Beginning balance (in shares) at Mar. 31, 2019	972,786
Beginning balance at Mar. 31, 2019	$ 33,704	19,171	(123)	15,321	(3,012)	2,347
Beginning Balance at Mar. 31, 2019								15,696	9,525	3,862	(36)	2,345													9,290	9,239	51
Beginning Balance at Mar. 31, 2019													10,340	1,588	7,385	(1,639)	3,006		4,043	2,723	1,320	3,458	1,714	1,744				2,785	1,650	1,135	1,521	914	607	1,129	984	145
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	$ 494			484		10		118		108		10	186			186			102		102	45		45	106		106	64		64	30		30	14		14
Stock issued during period, shares, long-term incentive plan activity	320
Stock issued during period, value, long-term incentive plan activity	$ 14	14	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	311
Stock issued during period, value, employee stock purchase plan	$ 24	24	0	0	0	0
Changes in equity of noncontrolling interests	3					3		3				3
Common stock dividends	$ (353)			(353)									(127)				(127)		(90)		(90)	(55)		(55)				(48)		(48)	(29)		(29)	(12)		(12)
Distributions to member								(224)		(224)															(88)		(88)
Contributions from parent													61		61										264	264		115	115					150	150
Other comprehensive income (loss), net of income taxes					22	(1)	21	(1)		0	0	(1)
Ending balance (in shares) at Jun. 30, 2019	973,417
Ending balance at Jun. 30, 2019	$ 33,907	19,209	(123)	15,452	(2,990)	2,359
Ending Balance at Jun. 30, 2019								15,592	9,525	3,746	(36)	2,357													9,572	9,503	69
Ending Balance at Jun. 30, 2019													10,460	1,588	7,446	(1,639)	3,065		4,055	2,723	1,332	3,448	1,714	1,734				2,916	1,765	1,151	1,522	914	608	1,281	1,134	147
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.36
Appropriation of retained earnings for future dividends																(186)	186	0
Net income (loss)	$ 760			772		(12)		244		257		(13)	200			200			140		140	55		55	189		189	98		98	33		33	63		63
Stock issued during period, shares, long-term incentive plan activity	207
Stock issued during period, value, long-term incentive plan activity	$ 10	10
Stock issued during period, shares, employee stock purchase plan	317
Stock issued during period, value, employee stock purchase plan	$ 19	19
Changes in equity of noncontrolling interests	(18)					(18)		(18)				(18)
Common stock dividends	(353)			(353)									(126)				(126)		(88)		(88)	(57)		(57)				(101)		(101)	(35)		(35)	(76)		(76)
Distributions to member								(225)		(225)															(213)		(213)
Contributions from parent													63		63				29	29		104	104
Other comprehensive income (loss), net of income taxes	$ 30				27	0	27	3
Ending balance (in shares) at Sep. 30, 2019	973,941
Ending balance at Sep. 30, 2019	$ 34,352	19,238	(123)	15,871	(2,963)	2,329
Ending Balance at Sep. 30, 2019								15,593	9,525	3,778	(36)	2,326													9,548	9,503	45
Ending Balance at Sep. 30, 2019													10,597	1,588	7,509	(1,639)	3,139		4,136	2,752	1,384	3,550	1,818	1,732				2,913	1,765	1,148	1,520	914	606	1,268	1,134	134
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.36
Net Income (Loss) Available to Common Stockholders, Basic	$ 772
Appropriation of retained earnings for future dividends																(200)	200	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	0	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													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]
Common Stock, Dividends, Per Share, Declared	$ 0.38
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)	1,519							485					304						317			273			418			227			91			106
Other comprehensive income (loss), net of income taxes	$ 90				90			(4)
Ending balance (in shares) at Sep. 30, 2020	977,405
Ending balance at Sep. 30, 2020	$ 35,103	19,362	(123)	16,749	(3,104)	2,219
Ending Balance at Sep. 30, 2020								14,924	9,633	3,114	(36)	2,213													10,069	10,112	(43)
Ending Balance at Sep. 30, 2020	32,884												11,095	1,588	8,060	(1,700)	3,147		4,488	3,014	1,474	4,054	2,191	1,863				3,222	2,058	1,164	1,684	1,089	595	1,388	1,271	117
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Available to Common Stockholders, Basic	$ 1,604
Appropriation of retained earnings for future dividends																(168)	168	0
Beginning balance (in shares) at Mar. 31, 2020	976,240
Beginning balance at Mar. 31, 2020	$ 34,616	19,303	(123)	16,475	(3,173)	2,134
Beginning Balance at Mar. 31, 2020								15,183	9,568	3,527	(41)	2,129													9,726	9,762	(36)
Beginning Balance at Mar. 31, 2020													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]
Net income (loss)	$ 574			521		53		529		476		53	(61)			(61)			39		39	39		39	94		94	57		57	19		19	18		18
Stock issued during period, shares, long-term incentive plan activity	148
Stock issued during period, value, long-term incentive plan activity	$ 17	17	0	0	0	0
Stock issued during period, shares, employee stock purchase plan	(51)
Stock issued during period, value, employee stock purchase plan	$ 15	15	0	0	0	0
Changes in equity of noncontrolling interests	(19)					(19)		(19)				(19)
Sale of noncontrolling interests	1	1						1	1
Common stock dividends	$ (374)			(374)									(124)				(124)		(85)		(85)	(62)		(62)				(73)		(73)	(14)		(14)	(12)		(12)
Distributions to member								(469)		(469)															(134)		(134)
Contributions from parent													124		124							26	26		215	215					100	100		115	115
Other comprehensive income (loss), net of income taxes					41	0	41	2		0	2	0
Ending balance (in shares) at Jun. 30, 2020	976,337
Ending balance at Jun. 30, 2020	$ 34,871	19,336	(123)	16,622	(3,132)	2,168
Ending Balance at Jun. 30, 2020								15,227	9,569	3,534	(39)	2,163													9,901	9,977	(76)
Ending Balance at Jun. 30, 2020													10,784	1,588	7,821	(1,700)	3,075		4,418	2,997	1,421	3,805	1,933	1,872				3,052	1,933	1,119	1,684	1,083	601	1,388	1,270	118
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Net income (loss)	$ 569			501		68		117		49		68	196			196			138		138	53		53	216		216	118		118	27		27	75		75
Stock issued during period, shares, long-term incentive plan activity	68
Stock issued during period, value, long-term incentive plan activity	$ 10	10
Stock issued during period, shares, employee stock purchase plan	1,000
Stock issued during period, value, employee stock purchase plan	$ 16	16
Changes in equity of noncontrolling interests	(17)					(17)		(18)				(18)
Sale of noncontrolling interests								0	0
Common stock dividends	(374)			(374)									(124)				(124)		(85)		(85)	(62)		(62)				(73)		(73)	(33)		(33)	(76)		(76)
Distributions to member								(469)		(469)															(183)		(183)
Contributions from parent								64	64				239		239				17	17		258	258		135	135		125	125		6	6		1	1
Other comprehensive income (loss), net of income taxes	$ 28				28		$ 28	3		0	3	0
Ending balance (in shares) at Sep. 30, 2020	977,405
Ending balance at Sep. 30, 2020	$ 35,103	$ 19,362	$ (123)	$ 16,749	$ (3,104)	$ 2,219
Ending Balance at Sep. 30, 2020								$ 14,924	$ 9,633	$ 3,114	$ (36)	$ 2,213													$ 10,069	$ 10,112	$ (43)
Ending Balance at Sep. 30, 2020	$ 32,884												11,095	$ 1,588	$ 8,060	(1,700)	3,147		$ 4,488	$ 3,014	$ 1,474	$ 4,054	$ 2,191	$ 1,863				$ 3,222	$ 2,058	$ 1,164	$ 1,684	$ 1,089	$ 595	$ 1,388	$ 1,271	$ 117
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared	$ 0.38
Net Income (Loss) Available to Common Stockholders, Basic	$ 501
Appropriation of retained earnings for future dividends													$ 3,147			$ (196)	$ 196	$ 0

Significant Accounting Policies

Significant Accounting Policies (All Registrants)	9 Months Ended
	Sep. 30, 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 & 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 September 30, 2020 and December 31, 2019 and for the three and nine months ended September 30, 2020 and 2019 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 Combined Notes to Consolidated Financial Statements have been prepared pursuant to the rules and regulations of the SEC for Quarterly Reports on Form 10-Q. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. COVID-19 (All Registrants) The Registrants have taken steps to mitigate the potential risks posed by the global outbreak (pandemic) of the 2019 novel coronavirus (COVID-19). 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. Management assessed certain accounting matters that require consideration of forecasted financial information, including, but not limited to, our allowance for credit losses and 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 September 30, 2020 and through the date of this report. The Registrants' future assessment of our current expectations of the magnitude and duration of COVID-19, as well as other factors, could result in material impacts to their 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 was 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 was 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, Pepco, DPL, and ACE’s Consolidated Balance Sheets. See Note 3 - Regulatory Matters of the 2019 Form 10-K for additional information regarding the regulatory recovery of credit losses on customer accounts receivable at ComEd, BGE, Pepco, DPL, 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 not material. The Registrants monitor these balances and will record an allowance if there are indicators of a decline in credit quality.

Regulatory Matters (All Registr

Regulatory Matters (All Registrants)	9 Months Ended
	Sep. 30, 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 DPL - Maryland (Electric) December 5, 2019 (amended April 23, 2020) 17 12 9.60 % July 14, 2020 July 16, 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 PECO - Pennsylvania (Natural Gas) September 30, 2020 69 10.95 % Second quarter of 2021 BGE - Maryland (Electric and Natural Gas) (b) May 15, 2020 228 10.1 % Fourth quarter of 2020 Pepco - District of Columbia (Electric) (c) May 30, 2019 (amended June 1, 2020) 136 9.7 % First quarter of 2021 Pepco - Maryland (Electric) (d) October 26, 2020 110 10.2 % Second quarter of 2021 DPL - Delaware (Natural Gas) (e) February 21, 2020 (amended October 9, 2020) 7 10.3 % First quarter of 2021 DPL - Delaware (Electric) (f) March 6, 2020 (amended October 26, 2020) 24 10.3 % Second 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 for 2021 through 2023 and total requested revenue requirement increases in 2023 of $137 million related to electric distribution and $91 million related to natural gas distribution to recover capital investments made in late 2019 and planned capital investments from 2020 to 2023. (c) Pepco filed the multi-year plan enhanced proposal as an alternative to address the impacts of COVID-19. Reflects a three-year cumulative multi-year plan for 2020 through 2022 and requested revenue requirement increases of $73 million in 2022 and $63 million in 2023, to recover capital investments made during 2018 through 2020 and planned capital investments through the end of 2022. (d) Reflects a three-year cumulative multi-year plan for April 1, 2021 through March 31, 2024 and total requested revenue requirement increases of $56 million effective April 1, 2023 and $54 million effective April 1, 2024 to recover capital investments made in 2019 and 2020 and planned capital investments through March 31, 2024. (e) The rates went into effect on September 21, 2020, subject to refund. (f) The rates went into effect on October 6, 2020, subject to refund. Transmission Formula Rates Transmission Formula Rate (Exelon and the Utility Registrants). ComEd’s, PECO's, BGE’s, Pepco's, DPL's, and ACE's transmission rates are each established based on a FERC-approved formula. ComEd, BGE, Pepco, DPL, and ACE are required to file an annual update to the FERC-approved formula on or before May 15 and PECO is required to file on or before May 31, with the resulting rates effective on June 1 of the same year. The annual update for ComEd, BGE, DPL, and ACE is based on prior year actual costs and current year projected capital additions (initial year revenue requirement). The annual update for PECO is based on prior year actual costs and current year projected capital additions, accumulated depreciation, and accumulated deferred income taxes. The annual update for Pepco is based on prior year actual costs and current year projected capital additions, accumulated depreciation, depreciation and amortization expense, and accumulated deferred income taxes. The update for ComEd, BGE, DPL, and ACE also reconciles any differences between the revenue requirement in effect beginning June 1 of the prior year and actual costs incurred for that year (annual reconciliation). The update for PECO and Pepco also reconciles any differences between the actual costs and actual revenues for the calendar year (annual reconciliation). For 2020, the following total increases/(decreases) were included in ComEd’s, PECO's, BGE’s, Pepco's, DPL's, and ACE's electric transmission formula rate filings: Registrant (a) Initial Revenue Requirement Increase (Decrease) Annual Reconciliation Decrease Total Revenue Requirement Increase (Decrease) (c) Allowed Return on Rate Base (d) Allowed ROE (e) ComEd $ 18 $ (4) $ 14 8.17 % 11.50 % PECO (b) 5 (28) (23) 7.47 % 10.35 % BGE 16 (3) 4 7.26 % 10.50 % Pepco 2 (46) (44) 7.81 % 10.50 % DPL (4) (40) (44) 7.20 % 10.50 % ACE 5 (25) (20) 7.40 % 10.50 % __________ (a) All rates are effective June 2020, subject to review by interested parties, which is anticipated to be completed by the fourth quarter of 2020 or first quarter of 2021 for ComEd, BGE, Pepco, DPL, and ACE and second quarter of 2021 for PECO. (b) PECO posted a revised filing to the PJM website on July 17, 2020 reflecting updates to the formula rate based on the FERC order dated July 9, 2020. (c) The decrease in PECO's transmission revenue requirement relates to refunds from December 1, 2017, in accordance with the settlement agreement dated July 22, 2019. The increase in BGE's transmission revenue requirement includes a $9 million reduction related to a FERC-approved dedicated facilities charge to recover the costs of providing transmission service to specifically designated load by BGE. ComEd, BGE, Pepco, DPL, and ACE’s transmission revenue requirement include a decrease related to the April 24, 2020 settlement agreement related to excess deferred income taxes. Refer to Transmission-Related Income Tax Regulatory Assets below for additional information. (d) Represents the weighted average debt and equity return on transmission rate bases. (e) As part of the FERC-approved settlements of ComEd’s 2007 and PECO's 2017 transmission rate cases, the rate of return on common equity is 11.50% and 10.35%, respectively, inclusive of a 50-basis-point incentive adder for being a member of a RTO, and the common equity component of the ratio used to calculate the weighted average debt and equity return for the transmission formula rate is currently capped at 55% and 55.75%, respectively. As part of the FERC-approved settlement of the ROE complaint against BGE, Pepco, DPL, and ACE, the rate of return on common equity is 10.50%, inclusive of a 50-basis-point incentive adder for being a member of a RTO. Other State Regulatory Matters Illinois Regulatory Matters Energy Efficiency Formula Rate (Exelon and ComEd). ComEd filed its annual energy efficiency formula rate update with the ICC on May 21, 2020. The filing establishes the revenue requirement used to set the rates that will take effect in January 2021 after the ICC’s review and approval. The revenue requirement requested is based on a reconciliation of the 2019 actual costs plus projected 2020 and 2021 expenditures. Initial Revenue Requirement Increase Annual Reconciliation Increase Total Revenue Requirement Increase Requested Return on Rate Base Requested ROE $ 45 $ 3 $ 48 (a) 6.28 % 8.38 % __________ (a) The requested revenue requirement increase provides for a weighted average debt and equity return on rate base of 6.28% inclusive of an allowed ROE of 8.38%. The ROE reflects the average rate on 30-year treasury notes plus 580 basis points. The ROE applicable to the 2019 reconciliation year is 8.96% and the return on rate base is 6.56%, which includes a performance adjustment that can either increase or decrease the ROE. New Jersey Regulatory Matters Advanced Metering Infrastructure Filing (Exelon, PHI, and ACE). On August 26, 2020, ACE filed an application with the NJBPU as was required seeking approval to deploy a smart energy network in alignment with New Jersey’s Energy Master Plan and Clean Energy Act. The proposal consists of estimated costs totaling $220 million, with deployment taking place over a 3-year implementation period from approximately 2021 to 2024 that involves the installation of an integrated system of smart meters for all customers accompanied by the requisite communications facilities and data management systems. ACE is seeking authority to recover these estimated investments through a combination of the ACE Infrastructure Investment Program rider mechanism and future distribution base rates. ACE currently expects a decision in this matter in the third quarter of 2021 but cannot predict if the NJBPU will approve the application as filed. 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) the 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, which FERC approved on September 24, 2020. 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 settlement resulted in a reduction to Operating revenues and an offsetting reduction to Income tax expense in the second quarter of 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 $255 million primarily due to an increase of $145 million in the Energy Efficiency Costs regulatory asset, $58 million in the Electric Distribution Formula Rate Significant One-time Events regulatory asset, $47 million in the ARO regulatory asset, and $18 million in the COVID-19 regulatory asset recorded in 2020, partially offset by a decrease of $37 million in the Electric Distribution Formula Rate Annual Reconciliations regulatory asset. Refer to COVID-19 disclosure below for additional information. PECO. Regulatory assets increased $135 million primarily due to an increase of $119 million in the Deferred Income Taxes regulatory asset and $20 million in new COVID-19 regulatory asset recorded in the third quarter of 2020. Refer to COVID-19 disclosure below for additional information. BGE . Regulatory liabilities decreased $68 million primarily due to a decrease of $73 million in the Deferred Income Taxes regulatory liability. Pepco . Regulatory liabilities decreased $58 million primarily due to a decrease of $99 million in the Deferred Income Taxes regulatory liability, partially offset by a $24 million increase in the Transmission FERC Formula Rate regulatory liability, and $24 million in the Electric Energy and Natural Gas Costs regulatory liability. DPL . Regulatory liabilities decreased $49 million primarily due to a decrease of $54 million in the Deferred Income Taxes regulatory liability, $4 million in the Removal Costs regulatory liability, and $3 million in the Electric Energy and Natural Gas Costs regulatory liability, partially offset by a $16 million increase in the Transmission FERC Formula Rate regulatory liability. ACE . Regulatory assets increased $58 million primarily due to an increase of $29 million in the Deferred Storm Costs regulatory asset, $19 million in the Uncollectible Deferral regulatory asset, and $17 million in the Electric Energy Costs regulatory asset, partially offset by a decrease of $9 million in the Securitized Stranded Costs regulatory asset. Regulatory liabilities decreased $55 million primarily due to a decrease of $80 million in the Deferred Income Taxes regulatory liability, partially offset by a $13 million increase in Transmission FERC Formula Rate regulatory liability, and $9 million in Stranded Costs regulatory liability. COVID-19 (Exelon and the Utility Registrants). Starting in March of 2020, the Utility Registrants temporarily suspended customer disconnections for non-payment and temporarily ceased new late payment fees for all customers and restored service to customers upon request who were disconnected in the last twelve months. The duration and extent of these measures varies by jurisdiction. While these measures are no longer in place for some jurisdictions, they are expected to continue through the first quarter of 2021 in other jurisdictions. Typically, the Utility Registrants recover credit loss expense through rate required programs or distribution base rate cases. ComEd and ACE have existing mechanisms for recovery of credit loss expense. For those jurisdictions without an existing rate required program to recover credit loss expense, the Utility Registrants are pursuing strategies to recover incremental costs being incurred as a result of COVID-19: • In the period of April to July of 2020, the MDPSC, the DCPSC, the DPSC, and the NJBPU issued orders authorizing the creation of regulatory assets to track incremental COVID-19 related costs. • In May of 2020, the PAPUC issued a Secretarial Letter authorizing the creation of regulatory assets to track incremental credit loss expense related to COVID-19. The Utility Registrants have also incurred direct costs related to COVID-19 consisting primarily of costs to acquire personal protective equipment, costs for cleaning supplies and services, and costs to hire healthcare professionals to monitor the health of their employees. The Utility Registrants have recorded regulatory assets for the impacts of COVID-19 reflecting primarily incremental credit losses and direct costs, partially offset by a decrease in travel costs at BGE and PHI. The Utility Registrants expect to seek recovery in upcoming distribution base rate cases. Exelon and the Utility Registrants recorded the following regulatory assets related to COVID-19: Exelon ComEd PECO BGE PHI Pepco DPL ACE September 30, 2020 $ 60 $ 18 $ 20 $ 11 $ 11 $ 8 $ 3 $ — Capitalized Ratemaking Amounts Not Recognized (Exelon and the Utility Registrants) The following table presents authorized amounts capitalized for ratemaking purposes related to earnings on shareholders’ investment that are not recognized for financial reporting purposes in Exelon's and the Utility Registrant's Consolidated Balance Sheets. These amounts will be recognized as revenues in the related Consolidated Statements of Operations and Comprehensive Income in the periods they are billable to our customers. Exelon ComEd (a) PECO BGE (b) PHI Pepco (c) DPL (c) ACE September 30, 2020 $ 54 $ — $ — $ 47 $ 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 $56 million and $31 million for the nine months ended September 30, 2020 and 2019, respectively. On May 15, 2019, New Jersey Rate Counsel appealed the NJBPU's decision to the New Jersey Superior Court. Briefing has been completed and oral argument is scheduled for December 9, 2020. 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. Due to COVID-19 related restrictions, the court extended the deadline to July 29, 2020. Petitioners did not file a brief by the deadline, so the case is deemed dismissed. Petitioners are permitted up to one year from July 29, 2020 to file a motion to vacate the dismissal if they can show good cause for the delay. See Note 6 — Early Plant Retirements for additional information related to Ginna and Nine Mile Point. New England Regulatory Matters Mystic Units 8 & 9 and Everett Marine Terminal Cost of Service Agreement (Exelon and Generation). On March 29, 2018, Generation notified grid operator ISO-NE of its plans to early retire Mystic Units 8 and 9 absent regulatory reforms on June 1, 2022. 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 & 9 for the period between June 1, 2022 - May 31, 2024. On December 20, 2018, FERC issued an order accepting the cost of service compensation, 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 adjacent Everett Marine Terminal acquired by Generation in October 2018. Those adjustments were reflected in a compliance filing made on 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 July 17, 2020, FERC issued three orders, which together affirmed the recovery of key elements of Mystic's cost of service compensation, including recovery of costs associated with the operation of the Everett Marine Terminal. FERC directed a downward adjustment to the rate base for Mystic Units 8 and 9, the effect of which will be partially offset by elimination of a crediting mechanism for third party gas sales during the term of the cost of service agreement. A compliance filing was submitted on September 15, 2020. Several parties filed protests to the compliance filing on the issue of how gross plant in-service was calculated, and Generation filed an answer to the protests on October 21, 2020. On July 28, 2020, FERC ordered additional briefings in the ROE proceeding. On August 25, 2020, a group of New England generators filed a complaint against Generation seeking to extend the scope of the claw back provision in the cost-of-service agreement, whereby Generation would refund certain amounts recovered during the term of the cost of service if it returns to market afterwards. On September 14, 2020, Generation filed an answer to the complaint arguing that the complaint is procedurally improper and a collateral attack on existing FERC orders and pointing out that the ISO-NE tariff contains protections against the New England generators' concerns that they failed to mention. Generation cannot predict the outcome of this proceeding. On June 10, 2020, Generation filed a complaint with FERC against ISO-NE on the grounds that ISO-NE failed to follow its tariff with respect to its evaluation of Mystic for transmission security for the 2024 to 2025 Capacity Commitment Period (FCA 15) and that the modifications that ISO-NE made to its unfiled planning procedures to avoid retaining Mystic should have been filed with FERC for approval. On July 27, 2020, ISO-NE issued a memo to NEPOOL announcing its determination pursuant to its unfiled planning procedures that Mystic Units 8 and 9 are not needed for FCA 15 for transmission security. It had previously determined Mystic Units 8 and 9 are not needed for fuel security. On August 17, 2020, FERC issued an order denying the complaint. On September 16, 2020, Generation filed a request for rehearing with FERC. The timing and the outcome of this proceeding is uncertain. See Note 6 — Early Plant Retirements and Note 8 — Asset Impairments for additional information on the impacts of Generation’s August 2020 decision to retire Mystic Units 8 & 9 upon expiration of the cost of service agreement. Federal Regulatory Matters PJM and NYISO MOPR Proceedings. PJM and NYISO capacity markets include a MOPR. If a resource is subjected to a MOPR, its offer is adjusted to effectively remove the revenues it receives through a state 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. On December 19, 2019, FERC required PJM to broadly apply the MOPR to all new and existing resources including nuclear, renewables, demand response, energy efficiency, storage, and all resources owned by vertically-integrated utilities. This greatly expands the breadth and scope of PJM’s MOPR, which is effective as of PJM’s next capacity auction. While FERC included some limited exemptions, no exemptions were available to state-supported nuclear resources. 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). In response to FERC’s order, PJM submitted a compliance filing on March 18, 2020 wherein PJM proposed tariff language interpreting and implementing FERC's directives and proposed a schedule for resuming capacity auctions that is contingent on the timing of FERC's action on the compliance filing. On April 16, 2020, FERC issued an order largely denying most requests for rehearing of FERC's December 2019 order but granting a few clarifications that required an additional PJM compliance filing which PJM submitted on June 1, 2020. On October 15, 2020, FERC issued an order denying requests for rehearing of its April 16, 2020 order and accepted PJM’s two compliance filings, subject to a further compliance filing to revise minor aspects of the proposed MOPR methodology. As part of that order, FERC also accepted PJM’s proposal to condense the schedule of activities leading up to the next capacity auction but did not specify when that schedule would commence given that a key element of the MOPR level computation remains pending before FERC in another proceeding. FERC issued an order on May 21, 2020 involving reforms to PJM’s day-ahead and real-time reserves markets that need to be reflected in the calculation of MOPR levels. In approving reforms to PJM’s reserves markets, FERC also directed PJM to develop a new methodology for estimating revenues that resources will receive for sales of energy and related services (referred to as the Energy and Ancillary Services Offset) and to use that new methodology in calculating a number of parameters and assumptions used in the capacity market, including MOPR levels. PJM submitted all elements of its new Energy and Ancillary Services Offset revenue projection methodology on August 5, 2020 . On review of this compliance filing, FERC is expected to address how these additional reforms will impact MOPR levels, the timeline for implementing the new revenue projection methodology, and the timing for commencing the capacity auction schedule. Unless Illinois and New Jersey can implement an FRR program in their PJM zones, the MOPR will apply in the next capacity auction 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 as an alternative to the PJM capacity auction. 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. Whether legislation is needed in New Jersey would depend on how the state chooses to structure an FRR program. Exelon cannot predict whether or when such legislative and regulatory changes can be implemented. On February 20, 2020, FERC issued an order rejecting requests to expand NYISO’s version of the MOPR (referred to as buyer-side mitigation rules) beyond its current limited applicability to certain resources in downstate. However, on October 14, 2020, two natural gas-fired generators in New York filed a complaint at FERC seeking to expand the MOPR in NYISO to apply to all resources, new and existing, across the entire NYISO market. Exelon plans to strenuously oppose expansion of FERC’s MOPR policies in the NYISO market. While it is too early in the proceeding to predict its outcome, if FERC follows its MOPR precedent in PJM and applies the MOPR in NYISO broadly as requested in the complaint, Generation’s facilities in NYISO that are receiving ZEC compensation may be at increased risk of not clearing the capacity auction. If Generation’s state-supported nuclear plants in PJM or NYISO 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 effec

Revenue from Contracts with Cus

Revenue from Contracts with Customers (All Registrants)	9 Months Ended
	Sep. 30, 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 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. The following table provides a rollforward of the contract assets reflected in Exelon's and Generation's Consolidated Balance Sheets for the three and nine months ended September 30, 2020 and 2019. The Utility Registrants do not have any contract assets. Exelon Generation Balance as of December 31, 2019 $ 174 $ 174 Amounts reclassified to receivables (19) (19) Revenues recognized 17 17 Balance at March 31, 2020 $ 172 $ 172 Amounts reclassified to receivables (26) (26) Revenues recognized 13 13 Balance at June 30, 2020 $ 159 $ 159 Amounts reclassified to receivables (18) (18) Revenues recognized 19 19 Balance at September 30, 2020 $ 160 $ 160 Exelon Generation Balance as of December 31, 2018 $ 187 $ 187 Amounts reclassified to receivables (26) (26) Revenues recognized 26 26 Balance at March 31, 2019 $ 187 $ 187 Amounts reclassified to receivables (18) (18) Revenues recognized 27 27 Balance at June 30, 2019 $ 196 $ 196 Amounts reclassified to receivables (65) (65) Revenues recognized 39 39 Balance at September 30, 2019 $ 170 $ 170 Contract Liabilities The Registrants record contract liabilities when consideration is received or due prior to the satisfaction of the performance obligations. The Registrants record contract liabilities within Other current liabilities and Other noncurrent liabilities within the Registrants' Consolidated Balance Sheets. For Generation, 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. On July 1, 2020, Pepco, DPL, and ACE each entered into a collaborative arrangement with an unrelated owner and manager of communication infrastructure (the Buyer). Under this arrangement, Pepco, DPL, and ACE sold a 60% undivided interest in their respective portfolios of transmission tower attachment agreements with telecommunications companies to the Buyer, in addition to transitioning management of the day-to-day operations of the jointly-owned agreements to the Buyer for 35 years, while retaining the safe and reliable operation of its utility assets. In return, Pepco, DPL, and ACE will provide the Buyer limited access on the portion of the towers where the equipment resides for the purposes of managing the agreements for the benefit of Pepco, DPL, ACE, and the Buyer. In addition, for an initial period of three years and two, two-year extensions that are subject to certain conditions, the Buyer has the exclusive right to enter into new agreements with telecommunications companies and to receive a 30% undivided interest in those new agreements. PHI, Pepco, DPL, and ACE received cash and recorded contract liabilities as of July 1, 2020 as shown in the table below. The revenue attributable to this arrangement will be recognized as operating revenue over the 35 years under the collaborative arrangement. The following table provides a rollforward of the contract liabilities reflected in Exelon's, Generation's, PHI's, Pepco's, DPL's, and ACE'S Consolidated Balance Sheets for the three and nine months ended September 30, 2020 and 2019. As of September 30, 2020 and December 31, 2019, ComEd's, PECO's, and BGE's contract liabilities were immaterial. Exelon Generation PHI Pepco DPL ACE Balance as of December 31, 2019 $ 33 $ 71 $ — $ — $ — $ — Consideration received or due 20 55 — — — — Revenues recognized (24) (70) — — — — Balance at March 31, 2020 $ 29 $ 56 $ — $ — $ — $ — Consideration received or due 13 34 — — — — Revenues recognized (22) (63) — — — — Balance at June 30, 2020 $ 20 $ 27 $ — $ — $ — $ — Consideration received or due 154 94 124 98 13 13 Revenues recognized (25) (65) (2) (2) — — Balance at September 30, 2020 $ 149 $ 56 $ 122 $ 96 $ 13 $ 13 Exelon Generation PHI Pepco DPL ACE Balance as of December 31, 2018 $ 27 $ 42 $ — $ — $ — $ — Consideration received or due 21 63 — — — — Revenues recognized (23) (66) — — — — Balance at March 31, 2019 $ 25 $ 39 $ — $ — $ — $ — Consideration received or due 17 52 — — — — Revenues recognized (21) (65) — — — — Balance at June 30, 2019 $ 21 $ 26 $ — $ — $ — $ — Consideration received or due 27 83 — — — — Revenues recognized (22) (61) — — — — Balance at September 30, 2019 $ 26 $ 48 $ — $ — $ — $ — The following table reflects revenues recognized in the three and nine months ended September 30, 2020 and 2019, which were included in contract liabilities at December 31, 2019 and 2018, respectively: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Exelon $ 2 $ 3 $ 25 $ 17 Generation 2 3 63 32 Transaction Price Allocated to Remaining Performance Obligations (All Registrants) The following table shows the amounts of future revenues expected to be recorded in each year for performance obligations that are unsatisfied or partially unsatisfied as of September 30, 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 $ 92 $ 223 $ 93 $ 53 $ 370 $ 831 Generation 136 313 123 53 275 900 PHI 2 9 8 8 95 122 Pepco 2 7 6 6 75 96 DPL — 1 1 1 10 13 ACE — 1 1 1 10 13 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)	9 Months Ended
	Sep. 30, 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 and nine months ended September 30, 2020 and 2019 is as follows: Three Months Ended September 30, 2020 and 2019 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Operating revenues (b) : 2020 Competitive businesses electric revenues $ 4,201 $ — $ — $ — $ — $ — $ (326) $ 3,875 Competitive businesses natural gas revenues 323 — — — — — — 323 Competitive businesses other revenues 135 — — — — — (3) 132 Rate-regulated electric revenues — 1,643 759 646 1,339 — (22) 4,365 Rate-regulated natural gas revenues — — 54 85 23 — (3) 159 Shared service and other revenues — — — — 6 484 (491) (1) Total operating revenues $ 4,659 $ 1,643 $ 813 $ 731 $ 1,368 $ 484 $ (845) $ 8,853 2019 Competitive businesses electric revenues $ 4,314 $ — $ — $ — $ — $ — $ (275) $ 4,039 Competitive businesses natural gas revenues 265 — — — — — 1 266 Competitive businesses other revenues 195 — — — — — (1) 194 Rate-regulated electric revenues — 1,583 716 619 1,357 — (7) 4,268 Rate-regulated natural gas revenues — — 62 84 20 — (3) 163 Shared service and other revenues — — — — 3 474 (478) (1) Total operating revenues $ 4,774 $ 1,583 $ 778 $ 703 $ 1,380 $ 474 $ (763) $ 8,929 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Intersegment revenues (c) : 2020 $ 331 $ 15 $ 3 $ 6 $ 6 $ 485 $ (845) $ 1 2019 275 4 1 6 4 474 (764) — Depreciation and amortization: 2020 $ 558 $ 294 $ 85 $ 133 $ 200 $ 19 $ — $ 1,289 2019 407 259 83 116 193 25 — 1,083 Operating expenses: 2020 $ 4,727 $ 1,302 $ 658 $ 642 $ 1,102 $ 489 $ (833) $ 8,087 2019 4,274 1,256 595 612 1,124 457 (759) 7,559 Interest expense, net: 2020 $ 80 $ 95 $ 39 $ 34 $ 67 $ 89 $ — $ 404 2019 109 91 33 31 66 79 — 409 Income (loss) before income taxes: 2020 $ 219 $ 256 $ 122 $ 61 $ 215 $ (87) $ — $ 786 2019 501 245 154 67 203 (68) — 1,102 Income Taxes: 2020 $ 100 $ 60 $ (16) $ 8 $ (1) $ 65 $ — $ 216 2019 87 45 14 12 14 — — 172 Net income (loss): 2020 $ 117 $ 196 $ 138 $ 53 $ 216 $ (151) $ — $ 569 2019 244 200 140 55 189 (68) — 760 Capital Expenditures: 2020 $ 282 $ 554 $ 312 $ 290 $ 386 $ 9 $ — $ 1,833 2019 392 452 228 300 308 7 — 1,687 __________ (a) Other primarily includes Exelon’s corporate operations, shared service entities, and other financing and investment activities. (b) 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. (c) 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. See Note 18 — Related Party Transactions for additional information on intersegment revenues. PHI: Pepco DPL ACE Other (a) Intersegment PHI Operating revenues (b) : 2020 Rate-regulated electric revenues $ 611 $ 314 $ 420 $ — $ (6) $ 1,339 Rate-regulated natural gas revenues — 23 — — — 23 Shared service and other revenues — — — 91 (85) 6 Total operating revenues $ 611 $ 337 $ 420 $ 91 $ (91) $ 1,368 2019 Rate-regulated electric revenues $ 642 $ 299 $ 419 $ — $ (3) $ 1,357 Rate-regulated natural gas revenues — 20 — — — 20 Shared service and other revenues — — — 92 (89) 3 Total operating revenues $ 642 $ 319 $ 419 $ 92 $ (92) $ 1,380 Intersegment revenues (c) : 2020 $ 3 $ 3 $ 1 $ 90 $ (91) $ 6 2019 2 1 1 93 (93) 4 Depreciation and amortization: 2020 $ 96 $ 48 $ 48 $ 8 $ — $ 200 2019 95 46 43 9 — 193 Operating expenses: 2020 $ 465 $ 296 $ 338 $ 94 $ (91) $ 1,102 2019 515 268 340 95 (94) 1,124 Interest expense, net: 2020 $ 35 $ 15 $ 15 $ 2 $ — $ 67 2019 33 15 15 3 — 66 Income (loss) before income taxes: 2020 $ 121 $ 28 $ 68 $ (2) $ — $ 215 2019 (d) 103 38 65 (3) — 203 Income Taxes: 2020 $ 3 $ 1 $ (7) $ 2 $ — $ (1) 2019 5 5 2 2 — 14 Net income (loss): 2020 $ 118 $ 27 $ 75 $ (4) $ — $ 216 2019 98 33 63 (5) — 189 Capital Expenditures: 2020 $ 188 $ 94 $ 103 $ 1 $ — $ 386 2019 157 85 73 (7) — 308 __________ (a) Other primarily includes PHI’s corporate operations, shared service entities, and other financing and investment activities. (b) 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. (c) Includes intersegment revenues with ComEd, BGE, and PECO, which are eliminated at Exelon. (d) The Income (loss) before income taxes amounts in Other and Intersegment Eliminations have been adjusted by an offsetting $195 million for consistency with the Exelon consolidating disclosure above. The following tables disaggregate the Registrants' revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. For Generation, the disaggregation of revenues reflects Generation’s two primary products of power sales and natural gas sales, with further disaggregation of power sales provided by geographic region. For the Utility Registrants, the disaggregation of revenues reflects the two primary utility services of rate-regulated electric sales and rate-regulated natural gas sales (where applicable), with further disaggregation of these tariff sales provided by major customer groups. Exelon’s disaggregated revenues are consistent with Generation and the Utility Registrants, but exclude any intercompany revenues. Competitive Business Revenues (Generation): Three Months Ended September 30, 2020 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,327 $ (20) $ 1,307 $ 6 $ 1,313 Midwest 974 68 1,042 1 1,043 New York 401 5 406 — 406 ERCOT 249 74 323 7 330 Other Power Regions 937 186 1,123 (14) 1,109 Total Competitive Businesses Electric Revenues 3,888 313 4,201 — 4,201 Competitive Businesses Natural Gas Revenues 169 154 323 — 323 Competitive Businesses Other Revenues (c) 85 50 135 — 135 Total Generation Consolidated Operating Revenues $ 4,142 $ 517 $ 4,659 $ — $ 4,659 Three Months Ended September 30, 2019 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,351 $ 10 $ 1,361 $ 3 $ 1,364 Midwest 1,052 47 1,099 (17) 1,082 New York 414 15 429 — 429 ERCOT 288 72 360 5 365 Other Power Regions 873 192 1,065 (25) 1,040 Total Competitive Businesses Electric Revenues 3,978 336 4,314 (34) 4,280 Competitive Businesses Natural Gas Revenues 160 105 265 34 299 Competitive Businesses Other Revenues (c) 112 83 195 — 195 Total Generation Consolidated Operating Revenues $ 4,250 $ 524 $ 4,774 $ — $ 4,774 __________ (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 o f $37 million and $77 million in 2020 and 2019, respectively, and the elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Three Months Ended September 30, 2020 Three Months Ended September 30, 2019 RNF from external customers (a) Intersegment Total RNF RNF from external customers (a) Intersegment Total RNF Mid-Atlantic $ 586 $ 5 $ 591 $ 684 $ 5 $ 689 Midwest 748 2 750 763 (16) 747 New York 281 4 285 288 3 291 ERCOT 141 6 147 76 (4) 72 Other Power Regions 253 (28) 225 212 (28) 184 Total Revenues net of purchased power and fuel expense for Reportable Segments 2,009 (11) 1,998 2,023 (40) 1,983 Other (b) 336 11 347 100 40 140 Total Generation Revenues net of purchased power and fuel expense $ 2,345 $ — $ 2,345 $ 2,123 $ — $ 2,123 __________ (a) Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allo cated to a region. See text above for a description of included activities. Includes unrealized mark-to-market gains of $255 million and $17 million in 2020 and 2019, respectively, accelerated nuclear fuel amortization associated with announced early pla nt retirements as discussed in Note 6 - Early Plant Retirements o f $24 million , which includes an impairment charge of $10 million , and $3 million decrease to revenue net of purchased power and fuel expense in 2020 and 2019, respectively, and the elimination of intersegment RNF. Electric and Gas Revenue by Customer Class (Utility Registrants): Three Months Ended September 30, 2020 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 920 $ 518 $ 389 $ 763 $ 307 $ 193 $ 263 Small commercial & industrial 379 104 65 134 36 45 53 Large commercial & industrial 135 66 113 262 195 21 46 Public authorities & electric railroads 10 7 7 14 8 3 3 Other (a) 234 58 78 141 47 44 50 Total rate-regulated electric revenues (b) $ 1,678 $ 753 $ 652 $ 1,314 $ 593 $ 306 $ 415 Rate-regulated natural gas revenues Residential $ — $ 32 $ 55 $ 11 $ — $ 11 $ — Small commercial & industrial — 16 9 6 — 6 — Large commercial & industrial — — 21 1 — 1 — Transportation — 6 — 3 — 3 — Other (c) — 1 3 2 — 2 — Total rate-regulated natural gas revenues (d) $ — $ 55 $ 88 $ 23 $ — $ 23 $ — Total rate-regulated revenues from contracts with customers $ 1,678 $ 808 $ 740 $ 1,337 $ 593 $ 329 $ 415 Other revenues Revenues from alternative revenue programs $ (38) $ 5 $ (9) $ 31 $ 18 $ 8 $ 5 Other rate-regulated electric revenues (e) 3 — — — — — — Other rate-regulated natural gas revenues (e) — — — — — — — Total other revenues $ (35) $ 5 $ (9) $ 31 $ 18 $ 8 $ 5 Total rate-regulated revenues for reportable segments $ 1,643 $ 813 $ 731 $ 1,368 $ 611 $ 337 $ 420 Three Months Ended September 30, 2019 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 865 $ 479 $ 352 $ 741 $ 311 $ 178 $ 252 Small commercial & industrial 393 109 64 147 41 48 58 Large commercial & industrial 141 63 116 297 222 26 49 Public authorities & electric railroads 12 9 7 17 11 3 3 Other (a) 222 63 82 164 58 50 56 Total rate-regulated electric revenues (b) $ 1,633 $ 723 $ 621 $ 1,366 $ 643 $ 305 $ 418 Rate-regulated natural gas revenues Residential $ — $ 38 $ 49 $ 9 $ — $ 9 $ — Small commercial & industrial — 17 9 4 — 4 — Large commercial & industrial — — 20 1 — 1 — Transportation — 5 — 4 — 4 — Other (c) — 2 5 2 — 2 — Total rate-regulated natural gas revenues (d) $ — $ 62 $ 83 $ 20 $ — $ 20 $ — Total rate-regulated revenues from contracts with customers $ 1,633 $ 785 $ 704 $ 1,386 $ 643 $ 325 $ 418 Other revenues Revenues from alternative revenue programs $ (56) $ (11) $ (5) $ (9) $ (3) $ (6) $ 1 Other rate-regulated electric revenues (e) 6 4 3 3 2 — — Other rate-regulated natural gas revenues (e) — — 1 — — — — Total other revenues $ (50) $ (7) $ (1) $ (6) $ (1) $ (6) $ 1 Total rate-regulated revenues for reportable segments $ 1,583 $ 778 $ 703 $ 1,380 $ 642 $ 319 $ 419 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates of $15 million, $3 million, $3 million, $6 million, $3 million, $3 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE, respectively, in 2020 and $4 million, $1 million, $2 million, $4 million, $2 million, $1 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE, respectively, in 2019. (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. Nine Months Ended September 30, 2020 and 2019 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Operating revenues (b) : 2020 Competitive businesses electric revenues $ 11,367 $ — $ — $ — $ — $ — $ (920) $ 10,447 Competitive businesses natural gas revenues 1,348 — — — — — (3) 1,345 Competitive businesses other revenues 557 — — — — — (5) 552 Rate-regulated electric revenues — 4,499 1,948 1,763 3,425 — (50) 11,585 Rate-regulated natural gas revenues — — 358 521 116 — (5) 990 Shared service and other revenues — — — — 13 1,440 (1,447) 6 Total operating revenues $ 13,272 $ 4,499 $ 2,306 $ 2,284 $ 3,554 $ 1,440 $ (2,430) $ 24,925 2019 Competitive businesses electric revenues $ 12,365 $ — $ — $ — $ — $ — $ (840) $ 11,525 Competitive businesses natural gas revenues 1,479 — — — — — — 1,479 Competitive businesses other revenues 436 — — — — — (4) 432 Rate-regulated electric revenues — 4,342 1,901 1,817 3,574 — (25) 11,609 Rate-regulated natural gas revenues — — 432 510 116 — (12) 1,046 Shared service and other revenues — — — — 10 1,410 (1,415) 5 Total operating revenues $ 14,280 $ 4,342 $ 2,333 $ 2,327 $ 3,700 $ 1,410 $ (2,296) $ 26,096 Intersegment revenues (c) : 2020 $ 932 $ 31 $ 7 $ 16 $ 13 $ 1,435 $ (2,430) $ 4 2019 844 13 4 18 11 1,410 (2,300) — Depreciation and amortization: 2020 $ 1,161 $ 841 $ 259 $ 405 $ 585 $ 61 $ — $ 3,312 2019 1,221 767 247 368 562 72 — 3,237 Operating expenses: 2020 $ 12,674 $ 3,798 $ 1,900 $ 1,903 $ 3,057 $ 1,452 $ (2,397) $ 22,387 2019 13,333 3,431 1,783 1,936 3,106 1,405 (2,291) 22,703 Interest expense, net: 2020 $ 277 $ 287 $ 108 $ 99 $ 201 $ 269 $ — $ 1,241 2019 336 268 100 89 197 231 — 1,221 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Income (loss) before income taxes: 2020 $ 532 $ 446 $ 310 $ 299 $ 340 $ (262) $ — $ 1,665 2019 1,355 674 461 320 436 (218) — 3,028 Income Taxes: 2020 $ 41 $ 142 $ (7) $ 26 $ (77) $ 16 $ — $ 141 2019 388 130 51 59 25 (27) — 626 Net income (loss): 2020 $ 485 $ 304 $ 317 $ 273 $ 418 $ (278) $ — $ 1,519 2019 784 544 410 261 412 (191) — 2,220 Capital Expenditures: 2020 $ 1,212 $ 1,583 $ 824 $ 838 $ 1,072 $ 77 $ — $ 5,606 2019 1,282 1,413 675 842 1,006 41 — 5,259 Total assets: September 30, 2020 $ 47,372 $ 34,243 $ 12,334 $ 11,370 $ 23,394 $ 9,070 $ (10,016) $ 127,767 December 31, 2019 48,995 32,765 11,469 10,634 22,719 8,484 (10,089) 124,977 __________ (a) Other primarily includes Exelon’s corporate operations, shared service entities, and other financing and investment activities. (b) 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. (c) 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. See Note 18 — Related Party Transactions for additional information on intersegment revenues. PHI: Pepco DPL ACE Other (a) Intersegment PHI Operating revenues (b) : 2020 Rate-regulated electric revenues $ 1,650 $ 838 $ 952 $ — $ (15) $ 3,425 Rate-regulated natural gas revenues — 116 — — — 116 Shared service and other revenues — — — 279 (266) 13 Total operating revenues $ 1,650 $ 954 $ 952 $ 279 $ (281) $ 3,554 2019 Rate-regulated electric revenues $ 1,748 $ 871 $ 966 $ (1) $ (10) $ 3,574 Rate-regulated natural gas revenues — 116 — — — 116 Shared service and other revenues — — — 298 (288) 10 Total operating revenues $ 1,748 $ 987 $ 966 $ 297 $ (298) $ 3,700 Intersegment revenues (c) : 2020 $ 6 $ 7 $ 3 $ 278 $ (281) $ 13 2019 5 5 2 297 (298) 11 Depreciation and amortization: 2020 $ 282 $ 143 $ 134 $ 26 $ — $ 585 2019 281 138 114 29 — 562 Operating expenses: 2020 $ 1,364 $ 843 $ 847 $ 284 $ (281) $ 3,057 2019 1,444 820 838 302 (298) 3,106 Interest expense, net: 2020 $ 103 $ 47 $ 45 $ 6 $ — $ 201 2019 100 45 44 8 — 197 Income (loss) before income taxes: 2020 $ 211 $ 71 $ 67 $ (9) $ — $ 340 2019 (d) 226 132 89 (11) — 436 Income Taxes: 2020 $ (16) $ (20) $ (39) $ (2) $ — $ (77) 2019 9 16 2 (2) — 25 Net income (loss): 2020 $ 227 $ 91 $ 106 $ (6) $ — $ 418 2019 217 116 87 (8) — 412 Capital Expenditures: 2020 $ 512 $ 278 $ 281 $ 1 $ — $ 1,072 2019 455 245 300 6 — 1,006 Total assets: September 30, 2020 $ 9,227 $ 4,992 $ 4,201 $ 5,239 $ (265) $ 23,394 December 31, 2019 (d) 8,661 4,830 3,933 5,335 (40) 22,719 __________ (a) Other primarily includes PHI’s corporate operations, shared service entities, and other financing and investment activities. (b) 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. (c) Includes intersegment revenues with ComEd, BGE, and PECO, which are eliminated at Exelon. (d) The Income (loss) before income taxes and Total assets amounts in Other and Intersegment Eliminations have been adjusted by an offsetting $422 million and $5.7 billion, respectively, for consistency with the Exelon consolidating disclosure above. The following tables disaggregate the Registrants' revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. For Generation, the disaggregation of revenues reflects Generation’s two primary products of power sales and natural gas sales, with further disaggregation of power sales provided by geographic region. For the Utility Registrants, the disaggregation of revenues reflects the two primary utility services of rate-regulated electric sales and rate-regulated natural gas sales (where applicable), with further disaggregation of these tariff sales provided by major customer groups. Exelon’s disaggregated revenues are consistent with Generation and the Utility Registrants, but exclude any intercompany revenues. Competitive Business Revenues (Generation): Nine Months Ended September 30, 2020 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 3,692 $ (152) $ 3,540 $ 21 $ 3,561 Midwest 2,773 240 3,013 (6) 3,007 New York 1,074 (12) 1,062 (1) 1,061 ERCOT 579 155 734 20 754 Other Power Regions 2,718 300 3,018 (34) 2,984 Total Competitive Businesses Electric Revenues 10,836 531 11,367 — 11,367 Competitive Businesses Natural Gas Revenues 881 467 1,348 — 1,348 Competitive Businesses Other Revenues (c) 268 289 557 — 557 Total Generation Consolidated Operating Revenues $ 11,985 $ 1,287 $ 13,272 $ — $ 13,272 Nine Months Ended September 30, 2019 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 3,798 $ 9 $ 3,807 $ 2 $ 3,809 Midwest 3,083 172 3,255 (31) 3,224 New York 1,195 16 1,211 — 1,211 ERCOT 594 198 792 13 805 Other Power Regions 2,849 451 3,300 (46) 3,254 Total Competitive Businesses Electric Revenues 11,519 846 12,365 (62) 12,303 Competitive Businesses Natural Gas Revenues 1,041 438 1,479 62 1,541 Competitive Businesses Other Revenues (c) 343 93 436 — 436 Total Generation Consolidated Operating Revenues $ 12,903 $ 1,377 $ 14,280 $ — $ 14,280 __________ (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 $238 million an d $64 million in 2020 and 2019, respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Nine Months Ended September 30, 2020 Nine Months Ended September 30, 2019 RNF from external customers (a) Intersegment Total RNF RNF from external customers (a) Intersegment Total RNF Mid-Atlantic $ 1,660 $ 23 $ 1,683 $ 2,007 $ 16 $ 2,023 Midwest 2,180 (2) 2,178 2,269 (22) 2,247 New York 714 11 725 800 10 810 ERCOT 311 14 325 252 (27) 225 Other Power Regions 608 (70) 538 542 (64) 478 Total Revenues net of purchased power and fuel expense for Reportable Segments 5,473 (24) 5,449 5,870 (87) 5,783 Other (b) 838 24 862 262 87 349 Total Generation Revenues net of purchased power and fuel expense $ 6,311 $ — $ 6,311 $ 6,132 $ — $ 6,132 __________ (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 $472 million and losses of $84 million in 2020 and 2019, respectively, accelerated nuclear fuel amortization associated with announced early pla nt retirements as discussed in Note 6 - Early Plant Retirements o f $24 million, which includes an impairment charge of $10 million , and $13 million decrease to revenue net of purchased power and fuel expense in 2020 and 2019, respectively, and the elimination of intersegment RNF. Electric and Gas Revenue by Customer Class (Utility Registrants): Nine Months Ended September 30, 2020 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 2,389 $ 1,277 $ 1,034 $ 1,825 $ 779 $ 501 $ 545 Small commercial & industrial 1,067 291 183 355 101 127 127 Large commercial & industrial 388 174 311 755 558 66 131 Public authorities & electric railroads 33 21 20 45 25 10 10 Other (a) 663 171 233 471 166 148 159 Total rate-regulated electric revenues (b) $ 4,540 $ 1,934 $ 1,781 $ 3,451 $ 1,629 $ 852 $ 972 Rate-regulated natural gas revenues Residential $ — $ 252 $ 342 $ 68 $ — $ 68 $ — Small commercial & industrial — 86 55 30 — 30 — Large commercial & industrial — — 96 3 — 3 — Transportation — 18 — 10 — 10 — Other (c) — 3 16 5 — 5 — Total rate-regulated natural gas revenues (d) $ — $ 359 $ 509 $ 116 $ — $ 116 $ — Total rate-regulated revenues from contracts with customers $ 4,540 $ 2,293 $ 2,290 $ 3,567 $ 1,629 $ 968 $ 972 Other revenues Revenues from alternative revenue programs $ (51) $ 10 $ (10) $ (15) $ 20 $ (15) $ (20) Other rate-regulated electric revenues (e) 10 3 3 2 1 1 — Other rate-regulated natural gas revenues (e) — — 1 — — — — Total other revenues $ (41) $ 13 $ (6) $ (13) $ 21 $ (14) $ (20) Total rate-regulated revenues for reportable segments $ 4,499 $ 2,306 $ 2,284 $ 3,554 $ 1,650 $ 954 $ 952 Nine Months Ended September 30, 2019 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 2,221 $ 1,231 $ 1,019 $ 1,816 $ 792 $ 499 $ 525 Small commercial & industrial 1,103 304 193 387 114 141 132 Large commercial & industrial 399 163 335 843 633 75 135 Public authorities & electric railroads 35 23 20 47 27 10 10 Other (a) 660 186 242 481 166 151 164 Total rate-regulated electric revenues (b) $ 4,418 $ 1,907 $ 1,809 $ 3,574 $ 1,732 $ 876 $ 966 Rate-regulated natural gas revenues Residential $ — $ 285 $ 327 $ 64 $ — $ 64 $ — Small commercial & industrial — 122 55 30 — 30 — Large commercial & industrial — 1 93 4 — 4 — Transportation — 18 — 11 — 11 — Other (c) — 5 19 6 — 6 — Total rate-regulated natural gas revenues (d) $ — $ 431 $ 494 $ 115 $ — $ 115 $ — Total rate-regulated revenues from contracts with customers $ 4,418 $ 2,338 $ 2,303 $ 3,689 $ 1,732 $ 991 $ 966 Other revenues Revenues from alternative revenue programs $ (98) $ (16) $ 11 $ 4 $ 10 $ (6) $ — Other rate-regulated electric revenues (e) 22 10 10 7 6 1 — Other rate-regulated natural gas revenues (e) — 1 3 — — 1 — Total other revenues $ (76) $ (5) $ 24 $ 11 $ 16 $ (4) $ — Total rate-regulated revenues for reportable segments $ 4,342 $ 2,333 $ 2,327 $ 3,700 $ 1,748 $ 987 $ 966 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates of $31 million, $6 million, $9 million, $13 million, $6 million, $7 million and $3 million at ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE, respectively, in 2020 and $13 million, $4 million, $5 million, $11 million, $5 million, $5 million and $2 million at ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE, respectively, in 2019. (c) Includes revenues from off-system natural gas sales. (d) Includes operating revenues from affiliates of $1 million and $7 million at PECO and BGE, respectively, in 2020 and less than $1 million and $13 million at PECO and BGE, respectively, in 2019. (e) Includes late payment charge revenues.

Accounts Receivable (All Regist

Accounts Receivable (All Registrants)	9 Months Ended
	Sep. 30, 2020
Credit Loss [Abstract]
Loans, Notes, Trade and Other Receivables Disclosure [Text Block]	Accounts Receivable (All Registrants) Allowance for Credit Losses on Accounts Receivable (All Registrants) The following tables present the rollforward of Allowance for Credit Losses on Customer Accounts Receivable. Three Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of June 30, 2020 $ 261 $ 33 $ 72 $ 71 $ 23 $ 62 $ 24 $ 18 $ 20 Plus: Current Period Provision for Expected Credit Losses (a) 114 1 37 27 14 35 11 7 17 Less: Write-offs, net of recoveries (b) 17 1 4 2 2 8 — 3 5 Balance as of September 30, 2020 $ 358 $ 33 $ 105 $ 96 $ 35 $ 89 $ 35 $ 22 $ 32 Nine Months Ended September 30, 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 (a) 222 13 62 56 28 63 24 14 25 Less: Write-offs, net of recoveries (b) 51 4 16 15 5 11 2 3 6 Less: Sale of customer accounts receivable (c) 56 56 — — — — — — — Balance as of September 30, 2020 $ 358 $ 33 $ 105 $ 96 $ 35 $ 89 $ 35 $ 22 $ 32 _________ (a) For the Utility Registrants, the increase is primarily as a result of increased aging of receivables, the temporary suspension of customer disconnections for non-payment, temporary cessation of new late payment fees, and reconnection of service to customers previously disconnected due to COVID-19. (b) Recoveries were not material to the Registrants. (c) See below for additional information on the sale of customer accounts receivable at Generation in the second quarter of 2020. The following tables present the rollforward of Allowance for Credit Losses on Other Accounts Receivable. Three Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of June 30, 2020 $ 61 $ — $ 22 $ 7 $ 6 $ 26 $ 11 $ 7 $ 8 Plus: Current Period Provision for Expected Credit Losses 15 — 5 1 3 6 2 1 3 Less: Write-offs, net of recoveries (a) 1 — — 1 — — — — — Balance as of September 30, 2020 $ 75 $ — $ 27 $ 7 $ 9 $ 32 $ 13 $ 8 $ 11 Nine Months Ended September 30, 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 36 — 9 3 7 17 6 4 7 Less: Write-offs, net of recoveries (a) 9 — 2 3 3 1 — — 1 Balance as of September 30, 2020 $ 75 $ — $ 27 $ 7 $ 9 $ 32 $ 13 $ 8 $ 11 _________ (a) Recoveries were not material to the Registrants. Unbilled Customer Revenue (All Registrants) 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 September 30, 2020 $ 672 $ 139 $ 193 $ 98 $ 115 $ 127 $ 72 $ 37 $ 18 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. Sales of Customer Accounts Receivable (Exelon and Generation) 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 DPP, which is reflected in Other current assets on Exelon’s and Generation’s Consolidated Balance Sheet. On April 8, 2020, Generation derecognized and transferred approximately $1.2 billion of receivables at fair value to the Purchasers in exchange for approximately $500 million in cash purchase price and $650 million of DPP. The following table summarizes the impact of the sale of certain receivables: As of September 30, 2020 Derecognized receivables transferred at fair value (a) $ 1,232 Cash proceeds received 500 DPP 732 _________ (a) Includes additional customer accounts receivable sold into the Facility of $4,515 million since the start of the financing agreement. Three months ended September 30, 2020 Nine months ended September 30, 2020 Loss on sale of receivables (a) $ 8 $ 23 _________ (a) Reflected in Operating and maintenance expense on Exelon and Generation's Consolidated Statements of Operations and Comprehensive Income. Nine months ended September 30, 2020 Proceeds from new transfers $ 1,889 Cash collections received on DPP 2,518 Cash collections reinvested in the Facility 4,407 Generation’s risk of loss following the transfer of accounts receivable is limited to the DPP outstanding. Payment of DPP is not subject to significant risks other than delinquencies and credit losses on accounts receivable transferred, which have historically been and are expected to be immaterial. Generation continues to service the receivables sold in exchange for a servicing fee. Generation did not record a servicing asset or liability as the servicing fees were immaterial. Generation reflected the cash proceeds received upon sale in Net cash provided by operating activities in the Consolidated Statements of Cash Flows. The collection and reinvestment of DPP is recognized in Net cash provided by investing activities of the Consolidated Statements of Cash Flows. See Note 13 — Fair Value of Financial Assets and Liabilities and Note 16 — Variable Interest Entities for additional information. Other Purchases and Sales of Customer and Other Accounts Receivables (All Registrants) 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. Nine Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Total Receivables Purchased $ 2,698 $ — $ 865 $ 786 $ 508 $ 787 $ 484 $ 160 $ 143 Total Receivables Sold 542 790 — — — — — — — Related Party Transactions: Receivables purchased from Generation — — 34 67 75 72 51 13 8 Receivables sold to the Utility Registrants — 248 — — — — — — —

Early Plant Retirements (Exelon

Early Plant Retirements (Exelon and Generation)	9 Months Ended
	Sep. 30, 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 TMI 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. Generation’s Dresden, Byron, and Braidwood nuclear plants in Illinois are also showing increased signs of economic distress, 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. While all of LaSalle's capacity did clear in the 2021-2022 planning year auction, Generation has become increasingly concerned about the economic viability of this plant as well in a landscape where energy market prices remain depressed and energy market rules remain fatally flawed. On August 27, 2020, Generation announced that it intends to permanently cease generation operations at Byron in September 2021 and at Dresden in November 2021. The current NRC licenses for Byron Units 1 and 2 expire in 2044 and 2046, respectively, and the licenses for Dresden Units 2 and 3 expire in 2029 and 2031, respectively. As a result of the decision to early retire Byron and Dresden, Exelon and Generation recognized certain one-time charges in the third quarter of 2020 related to materials and supplies inventory reserve adjustments, employee-related costs including severance benefit costs further discussed below, and construction work-in-progress impairments, among other items. In addition, as a result of the decisions to early retire Byron and Dresden, there are ongoing annual financial impacts stemming from shortening the expected economic useful lives of these nuclear plants primarily related to accelerated depreciation of plant assets (including any ARC), accelerated amortization of nuclear fuel, and changes in ARO accretion expense associated with the changes in decommissioning timing and cost assumptions to reflect an earlier retirement date. See Note 7 - Nuclear Decommissioning for additional information on changes to the nuclear decommissioning ARO balance and Note 8 — Asset Impairments for impairment assessment considerations given to the Midwest asset group as a result of the early retirement decision. The total impact on Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income is summarized in the table below. Income statement expense (pre-tax) Three and Nine Months Ended September 30, 2020 (a) Three Months Ended September 30, 2019 (b) Nine Months Ended September 30, 2019 (b) Depreciation and amortization Accelerated depreciation (c) $ 254 $ 71 $ 216 Accelerated nuclear fuel amortization 14 3 13 Operating and maintenance One-time charges 220 — — Other charges (d) 34 39 (44) Contractual offset (e) (129) — — Total $ 393 $ 113 $ 185 _________ (a) Reflects expense for Byron and Dresden. (b) Reflects expense for TMI. (c) Includes the accelerated depreciation of plant assets including any ARC. (d) For Dresden, reflects the net impacts associated with the remeasurement of the ARO. See Note 7 - Nuclear Decommissioning for additional information. For TMI, primarily reflects the net impacts associated with the remeasurement of the ARO. See Note 9 - Asset Retirement Obligations of the 2019 Form 10-K for additional information. (e) Reflects contractual offset for ARO accretion, ARC depreciation, and net impacts associated with the remeasurement of the ARO. For Byron and Dresden, based on the regulatory agreement with the ICC, decommissioning-related activities are offset within Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. The offset results in an equal adjustment to the noncurrent payables to ComEd at Generation and an adjustment to the regulatory liabilities at ComEd. See Note 9 - Asset Retirement Obligations of the Exelon 2019 Form 10-K for additional information. Severance benefit costs will be provided to employees impacted by the early retirements of Byron and Dresden, to the extent they are not redeployed to other nuclear plants. In the third quarter of 2020, Exelon and Generation recorded estimated severance expense of $81 million within Operating and maintenance expense in their Consolidated Statements of Operations and Comprehensive Income. The final amount of severance benefit costs will depend on the specific employees severed. The following table provides the balance sheet amounts as of September 30, 2020 for Exelon's and Generation's significant assets and liabilities associated with the Braidwood and LaSalle nuclear plants. Current depreciation provisions are based on the estimated useful lives of these nuclear generating stations, which reflect the first renewal of the operating licenses. Braidwood LaSalle Total Asset Balances Materials and supplies inventory, net $ 82 $ 107 $ 189 Nuclear fuel inventory, net 147 218 365 Completed plant, net 1,403 1,571 2,974 Construction work in progress 18 23 41 Liability Balances Asset retirement obligation (570) (926) (1,496) NRC License First Renewal Term 2046 (Unit 1) 2042 (Unit 1) 2047 (Unit 2) 2043 (Unit 2) Exelon continues to work with stakeholders on state policy solutions, while also advocating for broader market reforms at the regional and federal level. The absence of such solutions or reforms could result in future impairments of the Midwest asset group, or accelerated depreciation for specific plants over their shortened estimated useful lives, both of which could have a material unfavorable impact on Exelon's and Generation's future results of operations. Other Generation In March 2018, Generation notified ISO-NE of its plans to early retire, among other assets, the Mystic Generating Station's units 8 and 9 (Mystic 8 and 9) absent regulatory reforms to properly value reliability and regional fuel security. Thereafter, ISO-NE identified Mystic 8 and 9 as being needed to ensure fuel security for the region and entered into a cost of service agreement with these two units for the period between June 1, 2022 - May 31, 2024. The agreement was approved by the FERC in December 2018. On June 10, 2020, Generation filed a complaint with FERC against ISO-NE stating that ISO-NE failed to follow its tariff with respect to its evaluation of Mystic 8 and 9 for transmission security for the 2024 to 2025 Capacity Commitment Period (FCA 15) and that the modifications that ISO-NE made to its unfiled planning procedures to avoid retaining Mystic 8 and 9 should have been filed with FERC for approval. On August 17, 2020, FERC issued an order denying the complaint. As a result, on August 20, 2020, Exelon determined that Generation will permanently cease generation operations at Mystic 8 and 9 at the expiration of the cost of service commitment in May 2024. See Note 2 — Regulatory Matters for additional discussion of Mystic’s cost of service agreement. As a result of the decision to early retire Mystic 8 and 9, Exelon and Generation recognized $43 million of one-time charges related to an expected long-term maintenance contract termination and materials and supplies inventory reserve adjustments, among other items. In addition, there are annual financial impacts stemming from shortening the expected economic useful life of Mystic 8 and 9 primarily related to accelerated depreciation of plant assets. Exelon and Generation recorded incremental Depreciation and amortization expense of $6 million in the third quarter of 2020. See Note 8 — Asset Impairments for impairment assessment considerations of the New England Asset Group.

Nuclear Decommissioning (Exelon

Nuclear Decommissioning (Exelon and Generation)	9 Months Ended
	Sep. 30, 2020
Asset Retirement Obligation Disclosure [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 September 30, 2020: Nuclear decommissioning ARO at December 31, 2019 (a) $ 10,504 Accretion expense 367 Net increase due to changes in, and timing of, estimated future cash flows 806 Costs incurred related to decommissioning plants (59) Nuclear decommissioning ARO at September 30, 2020 (a) $ 11,618 _________ (a) Includes $93 million and $112 million as the current portion of the ARO at September 30, 2020 and December 31, 2019, respectively, which is included in Other current liabilities in Exelon’s and Generation’s Consolidated Balance Sheets. During the nine months ended September 30, 2020, the net $806 million increase in the ARO for the changes in the amounts and timing of estimated decommissioning cash flows was driven by updates to Byron and Dresden reflecting changes in assumed retirement dates and assumed methods of decommissioning as a result of the announcement to early retire these plants in 2021. Refer to Note 6 — Early Plant Retirements for additional information. NDT Funds Exelon and Generation had NDT funds totaling $13,547 million and $13,353 million at September 30, 2020 and December 31, 2019, respectively. The NDT funds also include $115 million and $163 million for the current portion of the NDT funds at September 30, 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. Generation will file its next decommissioning funding status report with the NRC by March 31, 2021. This report will reflect the status of decommissioning funding assurance as of December 31, 2020 and will include the impact of the announced early retirement of Byron and Dresden. A shortfall could require Exelon to post parental guarantee for Generation’s share of the funding assurance. However, the amount of any required guarantee will ultimately depend on the decommissioning approach adopted at Byron and Dresden, the associated level of costs, and the decommissioning trust fund investment performance going forward.

Asset Impairments (Exelon and G

Asset Impairments (Exelon and Generation)	3 Months Ended
	Sep. 30, 2020
Impairment or Disposal of Tangible Assets Disclosure [Abstract]
Asset Impairments (Exelon and Generation)	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 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. The United States Bankruptcy Court entered an order on June 20, 2020 confirming PG&E’s plan of reorganization. On July 1, 2020 the plan became effective, and PG&E emerged from bankruptcy. Under the confirmed plan, PG&E will continue to honor the existing PPA agreement with Antelope Valley. See Note 12 - Debt and Credit Agreements for additional information. 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 grid operator ISO-NE of its plans to early retire its Mystic Units 8 and 9 absent regulatory reforms on June 1, 2022. These events suggested that the carrying value of the 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. In the third quarter of 2020, in conjunction with the retirement announcement of Mystic Units 8 and 9, Generation completed a comprehensive review of the estimated undiscounted future cash flows of the New England asset group and concluded that the estimated undiscounted future cash flows and fair value of the New England asset group were less than their carrying values. As a result, a pre-tax impairment charge of $500 million was recorded in the third quarter of 2020 within Operating and maintenance expense in Exelon’s and Generation’s Consolidated Statements of Operations and Comprehensive Income. See Note 6 - Early Plant Retirements for additional information. Midwest Asset Group In the third quarter of 2020, in conjunction with the retirement announcements of the Byron and Dresden nuclear plants, Generation completed a comprehensive review of the estimated undiscounted future cash flows of the Midwest asset group and no impairment charge was required. We will continue to monitor the recoverability of the carrying value of the Midwest asset group as certain other nuclear plants in Illinois are also showing increased signs of economic distress, which could lead to an early retirement. See Note 6 - Early Plant Retirements for additional information. Equity Method Investments in Certain Distributed Energy Companies

Income Taxes (All Registrants)

Income Taxes (All Registrants)	9 Months Ended
	Sep. 30, 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 September 30, 2020 (a) Exelon Generation ComEd PECO (b) BGE PHI (c) Pepco DPL ACE (c) 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 12.3 (10.3) 8.1 (6.2) 5.1 5.5 4.6 6.6 6.9 Qualified NDT fund income 13.2 47.4 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.4) (4.5) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (4.3) — (0.6) (23.3) (1.2) (1.5) (2.1) (0.4) (1.3) Production tax credits and other credits (3.0) (9.2) (0.4) — (0.8) (0.5) (0.5) (0.5) (0.4) Noncontrolling interests 0.8 2.9 — — — — — — — Excess deferred tax amortization (10.1) — (5.6) (3.8) (10.6) (24.9) (20.0) (23.6) (36.8) Tax settlements (0.2) (0.7) — — — — — — — Other (0.8) (0.9) 1.1 (0.8) (0.3) 0.1 (0.4) 0.7 0.6 Effective income tax rate 27.5% 45.7% 23.4% (13.1)% 13.1% (0.5)% 2.5% 3.6% (10.3)% Three Months Ended September 30, 2019 (a) Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 6.4 5.2 8.1 (0.3) 6.3 4.8 1.9 6.6 6.9 Qualified NDT fund income 3.2 7.1 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (4.1) (8.9) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (1.7) — (1.0) (7.5) (1.1) (1.8) (2.6) (0.6) (1.9) Production tax credits and other credits (1.2) (2.7) — — — — — — — Noncontrolling interests (2.2) (4.8) — — — — — — — Excess deferred tax amortization (6.5) — (9.9) (3.6) (8.0) (17.7) (16.3) (13.5) (23.3) Other 0.7 0.5 0.4 (0.5) (0.2) 0.8 1.0 (0.1) 0.7 Effective income tax rate 15.6% 17.4% 18.4% 9.1% 17.9% 6.9% 4.9% 13.2% 3.1% Nine Months Ended September 30, 2020 (a) Exelon Generation (d) ComEd (e) PECO (b) BGE (c) PHI (c) Pepco (c) DPL (c) ACE (c) 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 9.3 — 12.7 (3.4) 5.5 5.0 4.2 6.5 6.8 Qualified NDT fund income 3.2 10.0 — — — — — — — Deferred Prosecution Agreement payments 2.5 — 9.4 — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.2) (3.2) (0.3) — (0.1) (0.2) (0.1) (0.3) (0.5) Plant basis differences (4.0) — (0.9) (15.9) (1.8) (2.2) (2.4) (0.5) (3.7) Production tax credits and other credits (2.6) (7.0) (0.4) — (0.4) (0.3) (0.3) (0.2) (0.4) Noncontrolling interests 1.0 3.1 — — — — — — — Excess deferred tax amortization (15.8) — (11.8) (3.5) (15.0) (45.3) (29.2) (53.6) (81.4) Tax settlements (5.0) (15.7) — — — — — — — Other 0.1 (0.5) 2.1 (0.5) (0.5) (0.6) (0.8) (1.1) — Effective income tax rate 8.5% 7.7% 31.8% (2.3)% 8.7% (22.6)% (7.6)% (28.2)% (58.2)% Nine Months Ended September 30, 2019 (a) Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 5.1 4.2 8.2 — 6.4 4.8 2.0 6.7 6.9 Qualified NDT fund income 5.3 11.9 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.9) (4.0) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (1.6) — (0.7) (6.8) (1.1) (1.8) (2.3) (0.6) (2.0) Production tax credits and other credits (1.0) (2.1) — — — — — — — Noncontrolling interests (1.0) (2.3) — — — — — — — Excess deferred tax amortization (6.0) — (9.2) (2.9) (7.9) (18.6) (17.3) (15.0) (23.4) Other 0.8 (0.1) 0.2 (0.2) 0.1 0.5 0.7 0.2 — Effective income tax rate 20.7% 28.6% 19.3% 11.1% 18.4% 5.7% 4.0% 12.1% 2.2% __________ (a) Positive percentages represent income tax expense. Negative percentages represent income tax benefit. (b) At PECO, the lower effective tax rate is primarily related to an increase in plant basis differences attributable to storm repairs. (c) At BGE, PHI, Pepco, DPL, and ACE, the lower effective tax rate is primarily attributable to accelerated amortization of transmission related deferred income tax regulatory liabilities as a result of regulatory settlements. See Note 2 — Regulatory Matters for additional information. (d) At Generation, the lower effective tax rate is primarily attributable to tax settlements. (e) At ComEd, the higher effective tax rate is primarily related to the nondeductible Deferred Prosecution Agreement payments. See Note 14 — Commitments and Contingencies for additional information. Accounting for Uncertainty in Income Taxes Exelon, Generation, PHI, and ACE have the following unrecognized tax benefits as of September 30, 2020 and December 31, 2019. ComEd, PECO, BGE, Pepco, and DPL's amounts are not material. Exelon Generation PHI ACE September 30, 2020 $ 125 $ 49 $ 53 $ 16 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, in the first quarter of 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 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 September 30, 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. Long-Term Marginal State Income Tax Rate (All Registrants) In the third quarter of 2020 and 2019, Exelon updated its marginal state income tax rates for changes in state apportionment. The changes in marginal rates in the third quarter of 2020 resulted in an increase of $66 million and a decrease of $26 million to the deferred income tax liability at Exelon and Generation, respectively, as of September 30, 2020. The changes in marginal rates in the third quarter of 2019 resulted in an increase of $23 million and $9 million to the deferred income tax liability at Exelon and Generation, respectively, as of September 30, 2019. Exelon and Generation recorded a corresponding adjustment to income tax expense, net of federal taxes, in each of those respective periods. Allocation of Tax Benefits (All Registrants) Generation and the Utility Registrants are all party to an agreement with Exelon and other subsidiaries of Exelon that provides for the allocation of consolidated tax liabilities and benefits (Tax Sharing Agreement). The Tax Sharing Agreement provides that each party is allocated an amount of tax similar to that which would be owed had the party been separately subject to tax. In addition, any net benefit attributable to Exelon is reallocated to the other Registrants. That allocation is treated as a contribution to the capital of the party receiving the benefit. The following table presents the allocation of federal tax benefits from Exelon under the Tax Sharing Agreement. Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2020 $ 64 $ 14 $ 17 $ — $ 17 $ 8 $ 6 $ 1 December 31, 2019 41 — 14 3 7 6 1 —

Retirement Benefits (All Regist

Retirement Benefits (All Registrants)	9 Months Ended
	Sep. 30, 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 loss 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 and nine months ended September 30, 2020 and 2019. Pension Benefits OPEB Three Months Ended September 30, Three Months Ended September 30, 2020 2019 2020 2019 Components of net periodic benefit cost: Service cost $ 97 $ 89 $ 22 $ 23 Interest cost 190 221 37 47 Expected return on assets (317) (306) (41) (38) Amortization of: Prior service cost (benefit) 1 — (30) (45) Actuarial loss 128 104 12 11 Settlement charges 8 7 — — Contractual termination benefits — 1 — — Net periodic benefit cost $ 107 $ 116 $ — $ (2) Pension Benefits OPEB Nine Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Components of net periodic benefit cost: Service cost $ 290 $ 267 $ 67 $ 70 Interest cost 569 663 114 141 Expected return on assets (953) (918) (122) (115) Amortization of: Prior service cost (benefit) 3 — (92) (134) Actuarial loss 384 310 36 34 Settlement charges 14 7 — — Contractual termination benefits — 1 — — Net periodic benefit cost $ 307 $ 330 $ 3 $ (4) The amounts below represent the Registrants' allocated pension and OPEB plan costs. For Exelon, the service cost component is included in Operating and maintenance expense and Property, plant, and equipment, net while the non-service cost components are included in Other, net and Regulatory assets. For Generation and the Utility Registrants, the service cost and non-service cost components are included in Operating and maintenance expense and Property, plant, and equipment, net in their consolidated financial statements. Three Months Ended September 30, Nine Months Ended September 30, Pension and OPEB Costs 2020 2019 2020 2019 Exelon $ 107 $ 114 $ 310 $ 326 Generation 30 37 89 100 ComEd 29 23 85 70 PECO 1 4 4 9 BGE 16 16 47 47 PHI 17 23 52 71 Pepco 4 6 11 19 DPL 2 4 6 11 ACE 3 4 10 12 Defined Contribution Savings Plans The Registrants participate in various 401(k) defined contribution savings plans that are sponsored by Exelon. The plans are qualified under applicable sections of the IRC and allow employees to contribute a portion of their pre-tax and/or after-tax income in accordance with specified guidelines. All Registrants match a percentage of the employee contributions up to certain limits. The following table presents the matching contributions to the savings plans during the three and nine months ended September 30, 2020 and 2019, respectively. Three Months Ended September 30, Nine Months Ended September 30, Savings Plan Matching Contributions 2020 2019 2020 2019 Exelon $ 37 $ 36 $ 104 $ 101 Generation 14 14 41 41 ComEd 9 9 25 26 PECO 3 2 8 7 BGE 4 4 8 9 PHI 3 4 9 8 Pepco 1 1 3 2 DPL 1 1 2 2 ACE — 1 1 1

Derivative Financial Instrument

Derivative Financial Instruments (All Registrants)	9 Months Ended
	Sep. 30, 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 15% 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 and Index priced 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 3 - Regulatory Matters of the 2019 Form 10-K for additional information. (b) As part of its hedging program, PECO enters into electric supply procurement contracts that do not meet the definition of a derivative instrument. (c) The fair value of the DPL economic hedge is not material as of September 30, 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 September 30, 2020 and December 31, 2019: September 30, 2020 Exelon Generation ComEd Derivatives Total Economic Proprietary Collateral (a)(b) Netting (a) Subtotal Economic Mark-to-market derivative assets $ 471 $ 2,566 $ 58 $ 79 $ (2,232) $ 471 $ — Mark-to-market derivative assets 383 1,500 16 39 (1,172) 383 — Total mark-to-market derivative assets 854 4,066 74 118 (3,404) 854 — Mark-to-market derivative liabilities (168) (2,414) (40) 84 2,232 (138) (30) Mark-to-market derivative liabilities (378) (1,313) (12) 49 1,172 (104) (274) Total mark-to-market derivative liabilities (546) (3,727) (52) 133 3,404 (242) (304) Total mark-to-market derivative net assets (liabilities) $ 308 $ 339 $ 22 $ 251 $ — $ 612 $ (304) December 31, 2019 Exelon Generation ComEd Description Total Economic Proprietary Collateral (a)(b) 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 not material and not reflected in the table above. (b) Of the collateral posted/(received), $34 million and $511 million represents variation margin on the exchanges at September 30, 2020 and December 31, 2019 respectively. Economic Hedges (Commodity Price Risk) Generation. For the three and nine months ended September 30, 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 Nine Months Ended 2020 2019 2020 2019 Income Statement Location Gain (Loss) Gain (Loss) Operating revenues $ 39 $ 76 $ 238 $ 65 Purchased power and fuel 209 (45) 224 (127) Total Exelon and Generation $ 248 $ 31 $ 462 $ (62) In general, increases and decreases in forward market prices have a positive and negative impact, respectively, on Generation’s owned and contracted generation positions that have not been hedged. Generation hedges commodity price risk on a ratable basis over three-year periods. As of September 30, 2020, the percentage of expected generation hedged for the Mid-Atlantic, Midwest, New York, and ERCOT reportable segments is 97%-100% and 87%-90% 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 and nine months ended September 30, 2020 and 2019, net pre-tax commodity mark-to-market gains and 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 $1,217 million and $1,269 million at September 30, 2020 and December 31, 2019, respectively, for Exelon and $517 million and $569 million at September 30, 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 $171 million and $231 million at September 30, 2020 and December 31, 2019, respectively. The mark-to-market derivative assets and liabilities as of September 30, 2020 and December 31, 2019 and the mark-to-market gains and losses for the three and nine months ended September 30, 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 September 30, 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 September 30, 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 $ 638 $ 27 $ 611 — $ — Non-investment grade 4 — 4 No external ratings Internally rated — investment grade 168 1 167 Internally rated — non-investment grade 110 29 81 Total $ 920 $ 57 $ 863 — $ — Net Credit Exposure by Type of Counterparty As of September 30, 2020 Financial institutions $ 26 Investor-owned utilities, marketers, power producers 650 Energy cooperatives and municipalities 142 Other 45 Total $ 863 _________ (a) As of September 30, 2020, credit collateral held from counterparties where Generation had credit exposure included $31 million of cash and $26 million of letters of credit. The credit collateral does not include non-liquid collateral. Utility Registrants. The Utility Registrants have contracts to procure electric and natural gas supply that provide suppliers with a certain amount of unsecured credit. If the exposure on the supply contract exceeds the amount of unsecured credit, the suppliers may be required to post collateral. The net credit exposure is mitigated primarily by the ability to recover procurement costs through customer rates. As of September 30, 2020, the Utility Registrants’ counterparty credit risk with suppliers was not material. Credit-Risk-Related Contingent Features (All Registrants) Generation. As part of the normal course of business, Generation routinely enters into physically or financially settled contracts for the purchase and sale of electric capacity, electricity, fuels, emissions allowances, and other energy-related products. Certain of Generation’s derivative instruments contain provisions that require Generation to post collateral. Generation also enters into commodity transactions on exchanges where the exchanges act as the counterparty to each trade. Transactions on the exchanges must adhere to comprehensive collateral and margining requirements. This collateral may be posted in the form of cash or credit support with thresholds contingent upon Generation’s credit rating from each of the major credit rating agencies. The collateral and credit support requirements vary by contract and by counterparty. These credit-risk-related contingent features stipulate that if Generation were to be downgraded or lose its investment grade credit rating (based on its senior unsecured debt rating), it would be required to provide additional collateral. This incremental collateral requirement allows for the offsetting of derivative instruments that are assets with the same counterparty, where the contractual right of offset exists under applicable master netting agreements. In the absence of expressly agreed-to provisions that specify the collateral that must be provided, collateral requested will be a function of the facts and circumstances of the situation at the time of the demand. In this case, Generation believes an amount of several months of future payments (i.e., capacity payments) rather than a calculation of fair value is the best estimate for the contingent collateral obligation, which has been factored into the disclosure below. The aggregate fair value of all derivative instruments with credit-risk related contingent features in a liability position that are not fully collateralized (excluding transactions on the exchanges that are fully collateralized) is detailed in the table below: Credit-Risk Related Contingent Features September 30, 2020 December 31, 2019 Gross fair value of derivative contracts containing this feature (a) $ (750) $ (956) Offsetting fair value of in-the-money contracts under master netting arrangements (b) 535 649 Net fair value of derivative contracts containing this feature (c) $ (215) $ (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 September 30, 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. September 30, 2020 December 31, 2019 Cash collateral posted $ 288 $ 982 Letters of credit posted 212 264 Cash collateral held 68 103 Letters of credit held 74 112 Additional collateral required in the event of a credit downgrade below investment grade 1,287 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.

Debt and Credit Agreements (All

Debt and Credit Agreements (All Registrants)	9 Months Ended
	Sep. 30, 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 September 30, 2020 and December 31, 2019. PECO had no commercial paper borrowings as of both September 30, 2020 and December 31, 2019. Outstanding Commercial Average Interest Rate on Commercial Paper Issuer September 30, 2020 December 31, 2019 September 30, 2020 December 31, 2019 Exelon (a) $ 141 $ 870 0.16 % 2.25 % Generation — 320 — % 1.84 % ComEd 141 130 0.16 % 2.38 % BGE — 76 — % 2.46 % PHI (b) — 208 — % N/A PEPCO — 82 — % 2.56 % DPL — 56 — % 2.02 % ACE — 70 — % 2.43 % __________ (a) Includes outstanding commercial paper at Exelon Corporate of $136 million with average interest rates on commercial paper borrowings of 1.92% at December 31, 2019. Exelon Corporate had no outstanding commercial paper borrowings as of September 30, 2020. (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. 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 September 30, 2020, the available capacity on Generation’s revolving credit facility was $4.9 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. Revolving 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 as needed. Bilateral Credit Agreements On May 15, 2020, Generation entered into a credit agreement establishing a $100 million bilateral credit facility. This facility will solely be used by Generation to issue letters of credit, and the maturity date is automatically renewed based on the contingency standards set within the agreement. During the second and third quarters of 2020, CENG drew on its bilateral credit facility. As of September 30, 2020, there was $40 million outstanding at this facility. The bilateral credit facility with CENG is incorporated within Generation, and supports the issuance of letters of credit and funding for working capital. Long-Term Debt Issuance of Long-Term Debt During the nine months ended September 30, 2020, the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Exelon Notes 4.05 % April 15, 2030 $ 1,250 Repay existing indebtedness and for general corporate purposes. Exelon Notes 4.70 % April 15, 2050 750 Repay existing indebtedness and for general corporate purposes. Generation Senior Notes 3.25 % June 1, 2025 900 Repay existing indebtedness and for general corporate purposes. Generation Energy Efficiency Project Financing (a) 3.95 % December 31, 2020 3 Funding to install energy conservation measures for the Fort Meade project. Generation Energy Efficiency Project Financing (a) 2.53 % April 30, 2021 2 Funding to install energy conservation measures for the Fort AP Hill project. 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. 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. PECO First and Refunding Mortgage Bonds 2.80 % June 15, 2050 350 Funding for general corporate purposes. BGE Senior Notes 2.90 % June 15, 2050 400 Repay commercial paper obligations and for general corporate purposes. Pepco First Mortgage Bonds 2.53 % February 25, 2030 150 Repay existing indebtedness and for general corporate purposes. Pepco First Mortgage Bonds 3.28 % September 23, 2050 150 Repay existing indebtedness and for general corporate purposes. DPL First Mortgage Bonds 2.53 % June 9, 2030 100 Repay existing indebtedness and for general corporate purposes. DPL (b) Tax-Exempt Bonds 1.05 % January 1, 2031 78 Refinance existing indebtedness. ACE Tax-Exempt First Mortgage Bonds 2.25 % June 1, 2029 23 Refinance existing indebtedness. ACE First Mortgage Bonds 3.24 % June 9, 2050 100 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) The bonds have a 1.05% interest rate through July 2025. Debt Covenants As of September 30, 2020, the Registrants are in compliance with debt covenants. Nonrecourse Debt Exelon and Generation have issued nonrecourse debt financing. Borrowings under these agreements are secured by the assets and equity of each respective project. The lenders do not have recourse against Exelon or Generation in the event of a default. Antelope Valley Solar Ranch One. In December 2011, the DOE Loan Programs Office issued a guarantee for up to $646 million for a nonrecourse loan from the Federal Financing Bank to support the financing of the construction of the Antelope Valley facility. The project became fully operational in 2014. The loan will mature on January 5, 2037. As of September 30, 2020, approximately $470 million was outstanding. In addition, Generation has issued letters of credit to support its equity investment in the project. As of September 30, 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 provided 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 event of default and in 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. Further, distributions from Antelope Valley to EGR IV were suspended. The United States Bankruptcy Court entered an order on June 20, 2020 confirming PG&E’s plan of reorganization. On July 1, 2020 the plan became effective, and PG&E emerged from bankruptcy. On July 21, 2020, Antelope Valley received a waiver from the DOE for the event of default and, as such, distributions from Antelope Valley to EGR IV were permitted and the debt was classified as noncurrent as of June 30, 2020. The debt continues to be presented as noncurrent as of September 30, 2020. See Note 8 — Asset Impairments for additional information. ExGen Renewables IV. In November 2017, EGR IV, an indirect subsidiary of Exelon and Generation, entered into an $850 million nonrecourse senior secured term loan credit facility agreement. Generation’s interests in EGRP, Antelope Valley, SolGen, and Albany Green Energy were all contributed to and are pledged as collateral for this financing. The loan is scheduled to mature on November 28, 2024. As of September 30, 2020, approximately $710 million was outstanding. 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)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities (All Registrants)	Fair Value of Financial Assets and Liabilities (All Registrants) Exelon 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 September 30, 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. September 30, 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 $ 37,589 $ 40,816 $ 3,237 $ 44,053 $ 36,039 $ 37,453 $ 2,580 $ 40,033 Generation 6,756 6,250 1,401 7,651 7,974 7,304 1,366 8,670 ComEd 8,981 10,970 — 10,970 8,491 9,848 — 9,848 PECO 3,753 4,498 50 4,548 3,405 3,868 50 3,918 BGE 3,664 4,263 — 4,263 3,270 3,649 — 3,649 PHI 7,020 6,082 1,786 7,868 6,563 5,902 1,164 7,066 Pepco 3,164 3,343 739 4,082 2,864 3,198 388 3,586 DPL 1,676 1,463 449 1,912 1,567 1,408 311 1,719 ACE 1,417 1,017 598 1,615 1,327 1,026 464 1,490 Long-Term Debt to Financing Trusts (a) Exelon $ 390 $ — $ 467 $ 467 $ 390 $ — $ 428 $ 428 ComEd 205 — 246 246 205 — 227 227 PECO 184 — 221 221 184 — 201 201 SNF Obligation Exelon $ 1,207 $ 1,042 $ — $ 1,042 $ 1,199 $ 1,055 $ — $ 1,055 Generation 1,207 1,042 — 1,042 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 September 30, 2020 and December 31, 2019: Exelon and Generation Exelon Generation As of September 30, 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) $ 1,687 $ — $ — $ — $ 1,687 $ 270 $ — $ — $ — $ 270 NDT fund investments Cash equivalents (b) 313 91 — — 404 313 91 — — 404 Equities 3,345 1,794 — 1,370 6,509 3,345 1,794 — 1,370 6,509 Fixed income Corporate debt — 1,516 280 — 1,796 — 1,516 280 — 1,796 U.S. Treasury and agencies 1,843 137 — — 1,980 1,843 137 — — 1,980 Foreign governments — 52 — — 52 — 52 — — 52 State and municipal debt — 104 — — 104 — 104 — — 104 Other — 40 — 1,010 1,050 — 40 — 1,010 1,050 Fixed income subtotal 1,843 1,849 280 1,010 4,982 1,843 1,849 280 1,010 4,982 Private credit — — 238 533 771 — — 238 533 771 Private equity — — — 439 439 — — — 439 439 Real estate — — — 650 650 — — — 650 650 NDT fund investments subtotal (c)(d) 5,501 3,734 518 4,002 13,755 5,501 3,734 518 4,002 13,755 Rabbi trust investments Cash equivalents 58 — — — 58 4 — — — 4 Mutual funds 88 — — — 88 28 — — — 28 Fixed income — 11 — — 11 — — — — — Life insurance contracts — 84 34 — 118 — 27 — — 27 Rabbi trust investments subtotal 146 95 34 — 275 32 27 — — 59 Commodity derivative assets Economic hedges 776 1,737 1,553 — 4,066 776 1,737 1,553 — 4,066 Proprietary trading — 37 37 — 74 — 37 37 — 74 Effect of netting and allocation of collateral (e)(f) (656) (1,594) (1,036) — (3,286) (656) (1,594) (1,036) — (3,286) Commodity derivative assets subtotal 120 180 554 — 854 120 180 554 — 854 DPP consideration — 732 — — 732 — 732 — — 732 Total assets 7,454 4,741 1,106 4,002 17,303 5,923 4,673 1,072 4,002 15,670 Exelon Generation As of September 30, 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 (700) (1,692) (1,639) — (4,031) (700) (1,692) (1,335) — (3,727) Proprietary trading — (36) (16) — (52) — (36) (16) — (52) Effect of netting and allocation of collateral (e)(f) 699 1,708 1,130 — 3,537 699 1,708 1,130 — 3,537 Commodity derivative liabilities subtotal (1) (20) (525) — (546) (1) (20) (221) — (242) Deferred compensation obligation — (135) — — (135) — (37) — — (37) Total liabilities (1) (155) (525) — (681) (1) (57) (221) — (279) Total net assets $ 7,453 $ 4,586 $ 581 $ 4,002 $ 16,622 $ 5,922 $ 4,616 $ 851 $ 4,002 $ 15,391 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 — 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 (c)(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 $677 million and $373 million at September 30, 2020 and December 31, 2019, respectively, and restricted cash of $116 million and $110 million at September 30, 2020 and December 31, 2019, respectively, and includes long-term restricted cash of $137 million and $177 million at September 30, 2020 and December 31, 2019, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Generation excludes cash of $408 million and $177 million at September 30, 2020 and December 31, 2019, respectively, and restricted cash of $45 million and $58 million at September 30, 2020 and December 31, 2019, respectively. (b) Includes $121 million and $90 million of cash received from outstanding repurchase agreements at September 30, 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 derivative assets of less than $1 million and $2 million, which have total notional amounts of $658 million and $724 million at September 30, 2020 and December 31, 2019, respectively. The notional principal amounts for these instruments provide one measure of the transaction volume outstanding as of the periods ended and do not represent the amount of Exelon and Generation's exposure to credit or market loss. (d) Excludes net liabilities of $208 million and $147 million at September 30, 2020 and December 31, 2019, respectively, which include certain derivative assets that have notional amounts of $153 million and $99 million at September 30, 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, net of collateral paid to counterparties, totaled $43 million, $114 million, and $94 million allocated to Level 1, Level 2, and Level 3 mark-to-market derivatives, respectively, as of September 30, 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), $34 million and $511 million represents variation margin on the exchanges as of September 30, 2020 and December 31, 2019, respectively. As of September 30, 2020, Exelon and Generation have outstanding commitments to invest in fixed income, private credit, private equity and real estate investments of approximately $52 million, $119 million, $299 million, and $395 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 September 30, 2020, respectively. Changes in fair value, cumulative adjustments, and impairments were not material for the three and nine months ended September 30, 2020. ComEd, PECO and BGE ComEd PECO BGE As of September 30, 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) $ 396 $ — $ — $ 396 $ 184 $ — $ — $ 184 $ 298 $ — $ — $ 298 Rabbi trust investments Mutual funds — — — — 9 — — 9 9 — — 9 Life insurance contracts — — — — — 13 — 13 — — — — Rabbi trust investments subtotal — — — — 9 13 — 22 9 — — 9 Total assets 396 — — 396 193 13 — 206 307 — — 307 Liabilities Deferred compensation obligation — (7) — (7) — (8) — (8) — (5) — (5) Mark-to-market derivative liabilities (b) — — (304) (304) — — — — — — — — Total liabilities — (7) (304) (311) — (8) — (8) — (5) — (5) Total net assets (liabilities) $ 396 $ (7) $ (304) $ 85 $ 193 $ 5 $ — $ 198 $ 307 $ (5) $ — $ 302 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 $76 million and $90 million at September 30, 2020 and December 31, 2019, respectively, and restricted cash of $36 million and $33 million at September 30, 2020 and December 31, 2019, respectively, and includes long-term restricted cash of $127 million and $163 million at September 30, 2020 and December 31, 2019, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. PECO excludes cash of $65 million and $12 million at September 30, 2020 and December 31, 2019, respectively. BGE excludes cash of $28 million and $24 million at September 30, 2020 and December 31, 2019, respectively, and restricted cash of $1 million at both September 30, 2020 and December 31, 2019. (b) The Level 3 balance consists of the current and noncurrent liability of $30 million and $274 million, respectively, at September 30, 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 September 30, 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) $ 166 $ — $ — $ 166 $ 124 $ — $ — $ 124 Rabbi trust investments Cash equivalents 52 — — 52 44 — — 44 Mutual funds 14 — — 14 14 — — 14 Fixed income — 11 — 11 — 12 — 12 Life insurance contracts — 26 34 60 — 24 41 65 Rabbi trust investments subtotal 66 37 34 137 58 36 41 135 Total assets 232 37 34 303 182 36 41 259 Liabilities Deferred compensation obligation — (17) — (17) — (19) — (19) Total liabilities — (17) — (17) — (19) — (19) Total net assets $ 232 $ 20 $ 34 $ 286 $ 182 $ 17 $ 41 $ 240 Pepco DPL ACE As of September 30, 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) $ 112 $ — $ — $ 112 $ 17 $ — $ — $ 17 $ 14 $ — $ — $ 14 Rabbi trust investments Cash equivalents 51 — — 51 — — — — — — — — Fixed income — 2 — 2 — — — — — — — — Life insurance contracts — 26 34 60 — — — — — — — — Rabbi trust investments subtotal 51 28 34 113 — — — — — — — — Total assets 163 28 34 225 17 — — 17 14 — — 14 Liabilities Deferred compensation obligation — (2) — (2) — — — — — — — — Total liabilities — (2) — (2) — — — — — — — — Total net assets $ 163 $ 26 $ 34 $ 223 $ 17 $ — $ — $ 17 $ 14 $ — $ — $ 14 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 $78 million and $57 million at September 30, 2020 and December 31, 2019, respectively, and includes long-term restricted cash of $10 million and $14 million at September 30, 2020 and December 31, 2019, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Pepco excludes cash of $46 million and $29 million at September 30, 2020 and December 31, 2019, respectively. DPL excludes cash of $9 million and $13 million at September 30, 2020 and December 31, 2019, respectively. ACE excludes cash of $13 million and $12 million at September 30, 2020 and December 31, 2019, respectively, and includes long-term restricted cash of $10 million and $14 million at September 30, 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 and nine months ended September 30, 2020 and 2019: Exelon Generation ComEd PHI and Pepco Three Months Ended September 30, 2020 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of June 30, 2020 $ 883 $ 499 $ 659 $ 1,158 $ (318) $ 43 $ — Total realized / unrealized gains (losses) Included in net income (327) 3 (318) (a) (315) — (12) — Included in noncurrent payables to affiliates — 18 — 18 — — (18) Included in regulatory assets/liabilities 32 — — — 14 (b) — 18 Change in collateral (79) — (79) (79) — — — Purchases, sales, issuances and settlements Purchases 66 1 65 66 — — — Sales (3) — (3) (3) — — — Settlements — (3) — (3) — 3 — Transfers out of Level 3 9 — 9 (c) 9 — — — Balance at September 30, 2020 $ 581 $ 518 $ 333 $ 851 $ (304) $ 34 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2020 $ (222) $ 3 $ (213) $ (210) $ — $ (12) $ — Exelon Generation ComEd PHI and Pepco Nine months ended September 30, 2020 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market 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 (483) 1 (474) (a) (473) — (10) — Included in noncurrent payables to affiliates — 17 — 17 — — (17) Included in regulatory assets 14 — — — (3) (b) — 17 Change in collateral (120) — (120) (120) — — — Purchases, sales, issuances and settlements Purchases 136 6 130 136 — — — Sales (27) — (27) (27) — — — Settlements (15) (18) — (18) — 3 — Transfers into Level 3 (5) 1 (6) (c) (5) — — — Transfers out of Level 3 13 — 13 (c) 13 — — — Balance as of September 30, 2020 $ 581 $ 518 $ 333 $ 851 $ (304) $ 34 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2020 $ (107) $ 1 $ (98) $ (97) $ — $ (10) $ — Exelon Generation ComEd PHI and Pepco Three Months Ended September 30, 2019 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of June 30, 2019 $ 1,179 $ 539 $ 873 $ 1,412 $ (273) $ 40 $ — Total realized / unrealized gains (losses) Included in net income (171) 2 (173) (a) (171) — — — Included in noncurrent payables to affiliates — 11 — 11 — — (11) Included in regulatory assets 4 — — — (7) (b) — 11 Change in collateral 41 — 41 41 — — — Purchases, sales, issuances and settlements Purchases 53 1 52 53 — — — Sales (22) (21) (1) (22) — — — Settlements (18) (18) — (18) — — — Transfers into Level 3 1 — 1 (c) 1 — — — Transfers out of Level 3 (11) — (11) (c) (11) — — — Balance as of September 30, 2019 $ 1,056 $ 514 $ 782 $ 1,296 $ (280) $ 40 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2019 $ (18) $ 2 $ (20) $ (18) $ — $ — $ — Exelon Generation ComEd PHI and Pepco Nine Months Ended September 30, 2019 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of December 31, 2018 $ 907 $ 543 $ 575 $ 1,118 $ (249) $ 38 $ — Total realized / unrealized gains (losses) Included in net income (125) 5 (132) (a) (127) — 2 — Included in noncurrent payables to affiliates — 32 — 32 — — (32) Included in regulatory assets 1 — — — (31) (b) — 32 Change in collateral 227 — 227 227 — — — Purchases, sales, issuances and settlements Purchases 163 43 120 163 — — — Sales (23) (21) (2) (23) — — — Settlements (88) (88) — (88) — — — Transfers into Level 3 5 — 5 (c) 5 — — — Transfers out of Level 3 (11) — (11) (c) (11) — — — Balance as of September 30, 2019 $ 1,056 $ 514 $ 782 $ 1,296 $ (280) $ 40 $ — The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2019 $ 173 $ 5 $ 166 $ 171 $ — $ 2 $ — __________ (a) Includes a reduction for the reclassification of $105 million and $376 million of realized losses due to the settlement of derivative contracts for the three and nine months ended September 30, 2020. Includes a reduction for the reclassification of $153 million and $298 million of realized losses due to the settlement of derivative contracts for the three and nine months ended September 30, 2019. (b) Includes 1) an increase in fair value of $9 million for the three months ended September 30, 2020 and a decrease in fair value of $7 million, $26 million, and $31 million for the three months ended September 30, 2019, nine months ended September 30, 2020, and nine months ended September 30, 2019, respectively, and 2) an increase in realized losses recorded in purchased power expense due to settlements associated with floating-to-fixed energy swap contracts with unaffiliated suppliers of $5 million, $4 million, $23 million, and $17 million for the three months ended September 30, 2020, three months ended September 30, 2019, nine months ended September 30, 2020, and nine months ended September 30, 2019, respectively. (c) Transfers into and out of Level 3 generally occur when the contract tenor becomes less and more observable respectively, primarily due to changes in market liquidity or assumptions for certain commodity contracts. The following tables present the income statement classification of the total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2020 and 2019: Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total realized losses for the three months ended September 30, 2020 $ (305) $ (13) $ (12) $ — $ (305) $ (13) $ — $ (12) Total realized losses for the nine months ended September 30, 2020 (370) (104) (10) — (370) (104) — (10) Total unrealized (losses) gains for the three months ended September 30, 2020 (216) 3 (12) 3 (216) 3 3 (12) Total unrealized (losses) gains for the nine months ended September 30, 2020 (50) (48) (10) 1 (50) (48) 1 (10) Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total realized (losses) gains for the three months ended September 30, 2019 $ (25) $ (148) $ — $ 2 $ (25) $ (148) $ 2 $ — Total realized gains (losses) for the nine months ended September 30, 2019 122 (254) — 5 122 (254) 5 — Total unrealized gains (losses) for the three months ended September 30, 2019 99 (119) — 2 99 (119) 2 — Total unrealized gains (losses) gains for the nine months ended September 30, 2019 368 (202) 2 5 368 (202) 5 2 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. Deferred Purchase Price Consideration (Exelon and Generation) Exelon and Generation have DPP consideration for the sale of certain receivables of retail electricity at Generation. This amount is valued based on the sales price of the receivables net of allowance for credit losses 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. Since the DPP consideration is based on the sales price of the receivables, it is categorized as Level 2 in the fair value hierarchy. See Note 5 - Accounts Receivable for additional information on the sale of certain receivables. 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 September 30, 2020 Fair Value at December 31, 2019 Valuation Unobservable 2020 Range & Arithmetic Average 2019 Range & Arithmetic Average Mark-to-market derivatives — Economic Hedges (Exelon and Generation) (a)(b) $ 218 $ 558 Discounted Forward power $9 - $113 $29 $9 - $180 $29 Forward gas $1.84 - $4.69 $2.77 $0.83 - $10.72 $2.55 Option Volatility 10% - 160% 57% 8% - 236% 70% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(b) $ 21 $ 45 Discounted Forward power $9 - $115 $31 $25 - $180 $33 Mark-to-market derivatives (Exelon and ComEd) $ (304) $ (301) Discounted Forward heat (c) 8x - 9x 8.85x 9x - 10x 9.68x Marketability 3% - 8% 4.93% 3% - 7% 4.95% Renewable 91% - 123% 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 $94 million and $214 million as of September 30, 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)	9 Months Ended
	Sep. 30, 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 September 30, 2020: Description Exelon PHI Pepco DPL ACE Total commitments $ 513 $ 320 $ 120 $ 89 $ 111 Remaining commitments (a) 87 69 57 7 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 $135 million, which will generate future earnings at Exelon and Generation. Investment costs, which are expected to be primarily capital in nature, are recognized as incurred and recorded in Exelon's and Generation's financial statements. As of September 30, 2020, 27 MWs of new generation were developed and Exelon and Generation have incurred costs of $118 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 September 30, 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 $ 1,462 $ 224 $ 1,238 $ — $ — $ — $ — Surety bonds (a) 1,056 388 641 27 — — — Financing trust guarantees 378 — — — — — 378 Guaranteed lease residual values (b) 28 — 2 3 3 6 14 Total commercial commitments $ 2,924 $ 612 $ 1,881 $ 30 $ 3 $ 6 $ 392 Generation Letters of credit $ 1,447 $ 220 $ 1,227 $ — $ — $ — $ — Surety bonds (a) 912 374 511 27 — — — Total commercial commitments $ 2,359 $ 594 $ 1,738 $ 27 $ — $ — $ — ComEd Letters of credit $ 7 $ — $ 7 $ — $ — $ — $ — Surety bonds (a) 16 5 11 — — — — Financing trust guarantees 200 — — — — — 200 Total commercial commitments $ 223 $ 5 $ 18 $ — $ — $ — $ 200 PECO Surety bonds (a) $ 2 $ — $ 2 $ — $ — $ — $ — Financing trust guarantees 178 — — — — — 178 Total commercial commitments $ 180 $ — $ 2 $ — $ — $ — $ 178 BGE Letters of credit $ 2 $ 2 $ — $ — $ — $ — $ — Surety bonds (a) 3 1 2 — — — — Total commercial commitments $ 5 $ 3 $ 2 $ — $ — $ — $ — PHI Surety bonds (a) $ 21 $ 3 $ 18 $ — $ — $ — $ — Guaranteed lease residual values (b) 28 — 2 3 3 6 14 Total commercial commitments $ 49 $ 3 $ 20 $ 3 $ 3 $ 6 $ 14 Pepco Surety bonds (a) $ 14 $ — $ 14 $ — $ — $ — $ — Guaranteed lease residual values (b) 9 — — 1 1 2 5 Total commercial commitments $ 23 $ — $ 14 $ 1 $ 1 $ 2 $ 5 DPL Surety bonds (a) $ 4 $ 2 $ 2 $ — $ — $ — $ — Guaranteed lease residual values (b) 12 — 1 1 1 3 6 Total commercial commitments $ 16 $ 2 $ 3 $ 1 $ 1 $ 3 $ 6 ACE Surety bonds (a) $ 3 $ 1 $ 2 $ — $ — $ — $ — Guaranteed lease residual values (b) 7 — 1 1 1 1 3 Total commercial commitments $ 10 $ 1 $ 3 $ 1 $ 1 $ 1 $ 3 __________ (a) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (b) Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The lease term associated with these assets ranges from 1 to 8 years . The maximum potential obligation at the end of the minimum lease term would be $74 million guaranteed by Exelon and PHI, of which $25 million , $31 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 leas t 2025. • PECO h as 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 2023. • 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 2023. • DPL has 1 site that is currently under study and the required cost at the site is not expected to be material. The historical nature of the MGP and gas purification sites and the fact that many of the sites have been buried and built over, impacts the ability to determine a precise estimate of the ultimate costs prior to initial sampling and determination of the exact scope and method of remedial activity. Management determines its best estimate of remediation costs using all available information at the time of each study, including probabilistic and deterministic modeling for ComEd and PECO, and the remediation standards currently required by the applicable state environmental agency. Prior to completion of any significant clean up, each site remediation plan is approved by the appropriate state environmental agency. ComEd, pursuant to an ICC order, and PECO, pursuant to settlements of natural gas distribution rate cases with the PAPUC, are currently recovering environmental remediation costs of former MGP facility sites through customer rates. While BGE and DPL do not have riders for MGP clean-up costs, they have historically received recovery of actual clean-up costs in distribution rates. As of September 30, 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: September 30, 2020 December 31, 2019 Total environmental Portion of total related to Total environmental Portion of total related to Exelon $ 494 $ 320 $ 478 $ 320 Generation 125 — 105 — ComEd 299 298 304 303 PECO 23 22 19 17 BGE 2 — 2 — PHI 45 — 48 — Pepco 43 — 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 $30 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. Pursuant to a series of annual agreements since 2011, the DOJ and the PRPs have tolled the statute of limitations until February 28, 2021 so that settlement discussions can proceed. On August 3, 2020, the DOJ advised Cotter and the other PRPs that it is seeking approximately $90 million from all the PRPs and that the PRPs must submit a good faith joint proposed settlement offer by December 1, 2020. 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 on February 3, 2020, following a 45-day public comment period and a public meeting. Pepco and Generation are developing 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), and on September 30, 2020, DOEE released its Interim ROD. The Interim ROD reflects an adaptive management approach which will require 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 September 30, 2020 and December 31, 2019, Exelon and Generation had recorded estimated liabilities of approximately $91 million and $83 million, respectively, in total for asbestos-related bodily injury claims. As of September 30, 2020, approximately $27 million of this amount related to 274 open claims presented to Generation, while the remaining $64 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 TIF Agreement on June 30, 2020, could be material to Generation’s financial statements. Deferred Prosecution Agreement (DPA) and Related Matters (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 (USAO) 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 USAO requiring production of records of any communications with certain individuals and entities. On October 22, 2019, the SEC notified Exelon and ComEd that it had also opened an investigation into their lobbying activities. On July 17, 2020, ComEd entered into a DPA with the USAO to resolve the USAO investigation. Under the DPA, the USAO filed a single charge alleging that ComEd improperly gave and offered to give jobs, vendor subcontracts, and payments associated with those jobs and subcontracts for the benefit of the Speaker of the Illinois House of Representatives and the Speaker’s associates, with the intent to influence the Speaker’s action regarding legislation affecting ComEd’s interests. The DPA provides that the USAO will defer any prosecution of such charge and any other criminal or civil case against ComEd in connection with the matters identified therein for a three-year period subject to certain obligations of ComEd, including payment to the U.S. Treasury of $200 million, with $100 million payable within thirty days of the filing of the DPA with the United States District Court for the Northern District of Illinois and an additional $100 million within ninety days of such filing date. The payments were recorded within Operating and maintenance expense in Exelon’s and ComEd’s Consolidated Statements of Operations and Comprehensive Income in the second quarter of 2020. The payments will not be recovered in rates or charged to customers and ComEd will not seek or accept reimbursement or indemnification from any source other than Exelon . Exelon made equity contributions to ComEd of $100 million in August 2020 and $100 million in October 2020. On August 13, 2020, a motion was filed in the U.S. District Court for the Northern District of Illinois by and on behalf of ComEd customers seeking to enjoin ComEd from paying these funds to the U.S. Treasury and requiring the U.S. government to establish a victims’ restitution fund from which the $200 million would be disbursed to ComEd customers. The U.S. government and ComEd filed briefs in opposition to this motion. The motion remains pending, and at the U.S. government's direction, the $200 million payment will not be transferred to the U.S. Treasury until the court rules on the motion. $100 million was recorded as Restricted cash and cash equivalents on Exelon’s and ComEd’s Consolidated Balance Sheets as of September 30, 2020 and $100 million was recorded as restricted cash in October 2020. Exelon was not made a party to the DPA, and therefore the investigation by the USAO into Exelon’s activities ends with no charges being brought against Exelon. The SEC’s investigation remains ongoing and Exelon and ComEd have cooperated fully and intend to continue to cooperate fully with the SEC. Exelon and ComEd cannot predict the outcome of the SEC investigation. No loss contingency has been reflected in Exelon's and ComEd's consolidated financial statements with respect to the SEC investigation, as this contingency is neither probable nor reasonably estimable at this time. Subsequent to Exelon announcing the receipt of the subpoenas, various lawsuits have been filed and two demand letters have been received related to the subject of the subpoenas, the conduct described in the DPA and the SEC's investigation, including: • A putative class action lawsuit against Exelon and certain officers of Exelon and ComEd was filed in federal court in December 2019 alleging misrepresentations and omissions in Exelon’s SEC filings related to ComEd’s lobbying activities and the related investigations. The complaint was amended on September 16, 2020, to dismiss two of the original defendants and add other defendants, including ComEd. • A derivative shareholder lawsuit was filed against Exelon, its directors and certain officers of Exelon and ComEd in April 2020 alleging, among other things, breaches of fiduciary duties also purporting to relate to matters that are the subject of the subpoenas and the SEC investigation. The plaintiff voluntarily dismissed this derivative action without prejudice to refile on July 28, 2020. • Three putative class action lawsuits against ComEd and Exelon were filed in Illinois state court in the third quarter of 2020 seeking restitution and compensatory damages on behalf of ComEd customers. T hese three state cases were consolidated into a single action in October of 2020. In addition, on November 2, 2020, the Citizens Utility Board (CUB) filed a motion to intervene in the state cases pursuant to an Illinois statute allowing the CUB to intervene as a party or otherwise participate on behalf of utility consumers in any proceeding which affects the interest of utility consumers. The CUB has requested that the court stay the state cases pending the resolution of the federal cases, described below. • Four putative class action lawsuits against ComEd and Exelon were filed in federal court in the third quarter of 2020 alleging, among other things, civil violations of federal racketeering laws. In addition, the CUB filed a motion to intervene in these cases on October 22, 2020 and filed a proposed complaint against ComEd in conjunction with that motion alleging Racketeer Influenced and Corrupt Organization Act (RICO) and other causes of action on October 29, 2020. • Two shareholders sent letters to the Exelon Board of Directors in the third quarter of 2020 demanding, among other things, that the Exelon Board of Directors investigate and address alleged breaches of fiduciary duties and other alleged violations by Exelon and ComEd officers and directors related to the conduct described in the DPA. No loss contingencies have been reflec ted in Exelon’s and ComEd’s consolidated financial statements with respect to these matters, as such contingencies are neither probable nor reasonably estimable at this time. 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)	9 Months Ended
	Sep. 30, 2020
Changes in Accumulated Other Comprehensive Income [Abstract]
Changes in Accumulated Other Comprehensive Income [Text Block]	Changes in Accumulated Other Comprehensive Income (Exelon) The following tables present changes in Exelon's AOCI, net of tax, by component: Three Months Ended September 30, 2020 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Total Beginning balance $ (3) $ (3,096) $ (33) $ (3,132) OCI before reclassifications (1) (13) 3 (11) Amounts reclassified from AOCI — 39 — 39 Net current-period OCI (1) 26 3 28 Ending balance $ (4) $ (3,070) $ (30) $ (3,104) Three Months Ended September 30, 2019 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign AOCI of Investments in Unconsolidated Affiliates (b) Total Beginning balance $ (2) $ (2,957) $ (29) $ (2) $ (2,990) OCI before reclassifications — 6 (2) — 4 Amounts reclassified from AOCI — 21 — 2 23 Net current-period OCI — 27 (2) 2 27 Ending balance $ (2) $ (2,930) $ (31) $ — $ (2,963) Nine Months Ended September 30, 2020 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Total Beginning balance $ (2) $ (3,165) $ (27) $ (3,194) OCI before reclassifications (2) (17) (3) (22) Amounts reclassified from AOCI — 112 — 112 Net current-period OCI (2) 95 (3) 90 Ending balance $ (4) $ (3,070) $ (30) $ (3,104) Nine Months Ended September 30, 2019 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign AOCI of Investments in Unconsolidated Affiliates (b) Total Beginning balance $ (2) $ (2,960) $ (33) $ — $ (2,995) OCI before reclassifications — (32) 2 (2) (32) Amounts reclassified from AOCI — 62 — 2 64 Net current-period OCI — 30 2 — 32 Ending balance $ (2) $ (2,930) $ (31) $ — $ (2,963) _________ (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 September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 4 $ 6 $ 12 $ 18 Actuarial loss reclassified to periodic benefit cost (16) (13) (50) (39) Pension and non-pension postretirement benefit plans valuation adjustment 3 — 6 14

Variable Interest Entities (Exe

Variable Interest Entities (Exelon, Generation, PHI and ACE)	9 Months Ended
	Sep. 30, 2020
Variable Interest Entity [Abstract]
Variable Interest Entity Disclosure	Variable Interest Entities (Exelon, Generation, PHI and ACE) At September 30, 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 September 30, 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. September 30, 2020 December 31, 2019 Exelon Generation PHI (a) ACE Exelon Generation PHI (a) ACE Cash and cash equivalents $ 148 $ 148 $ — $ — $ 163 $ 163 $ — $ — Restricted cash and cash equivalents 52 48 4 4 88 85 3 3 Accounts receivable Customer 151 151 — — 151 151 — — Other 39 39 — — 39 39 — — Unamortized energy contract assets 22 22 — — 23 23 — — Inventories, net Materials and supplies 241 241 — — 227 227 — — Other current assets 781 776 5 — 32 31 1 — Total current assets 1,434 1,425 9 4 723 719 4 3 Property, plant, and equipment, net 5,865 5,865 — — 6,022 6,022 — — Nuclear decommissioning trust funds 2,785 2,785 — — 2,741 2,741 — — Unamortized energy contract assets 253 253 — — 250 250 — — Other noncurrent assets 49 38 11 10 89 73 16 14 Total noncurrent assets 8,952 8,941 11 10 9,102 9,086 16 14 Total assets (b) $ 10,386 $ 10,366 $ 20 $ 14 $ 9,825 $ 9,805 $ 20 $ 17 Long-term debt due within one year $ 134 $ 109 $ 25 $ 20 $ 544 $ 523 $ 21 $ 20 Accounts payable 81 81 — — 106 106 — — Accrued expenses 63 63 — — 70 70 — — Unamortized energy contract liabilities 5 5 — — 8 8 — — Other current liabilities 26 26 — — 3 3 — — Total current liabilities 309 284 25 20 731 710 21 20 Long-term debt 913 906 7 6 527 504 23 21 Asset retirement obligations 2,210 2,210 — — 2,128 2,128 — — Unamortized energy contract liabilities 1 1 — — 1 1 — — Other noncurrent liabilities 106 106 — — 89 89 — — Total noncurrent liabilities 3,230 3,223 7 6 2,745 2,722 23 21 Total liabilities (c) $ 3,539 $ 3,507 $ 32 $ 26 $ 3,476 $ 3,432 $ 44 $ 41 _________ (a) Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity. (b) Exelon’s and Generation’s balances include unrestricted assets for current unamortized energy contract assets of $22 million and $23 million, Property, plant, and equipment of $1 million and $20 million, non-current unamortized energy contract assets of $253 million and $250 million, and other unrestricted assets of $8 million and $0 million as of September 30, 2020 and December 31, 2019, respectively (c) Exelon’s and Generation’s balances include liabilities with recourse of $8 million and $3 million as of September 30, 2020 and December 31, 2019, respectively. As of September 30, 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 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. NER - A bankruptcy remote, special purpose entity which is 100% owned by Generation, which purchases certain of Generation’s customer accounts receivable arising from the sale of retail electricity. NER’s assets will be available first and foremost to satisfy the claims of the creditors of NER. See Note 5 - Accounts Receivable for additional information on the sale of receivables. Equity capitalization is insufficient to support its operations. Generation conducts all 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 and the FERC. The FERC approval was obtained on July 30, 2020. From the date the put was exercised, the process and regulatory approvals could take one to two years 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 September 30, 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 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 ATF. The bondholders also have a variable interest for the investment made to purchase the Transition Bonds. ACE controls the servicing activities. Unconsolidated VIEs Exelon’s and Generation’s variable interests in unconsolidated VIEs generally include equity investments and energy purchase and sale contracts. For the equity investments, the carrying amount of the investments is reflected in Exelon’s and Generation’s Consolidated Balance Sheets in Investments. For the energy purchase and sale contracts (commercial agreements), the carrying amount of assets and liabilities in Exelon’s and Generation’s Consolidated Balance Sheets that relate to their involvement with the VIEs are predominately related to working capital accounts and generally represent the amounts owed by, or owed to, Exelon and Generation for the deliveries associated with the current billing cycles under the commercial agreements. As of September 30, 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: September 30, 2020 December 31, 2019 Commercial Equity Total Commercial Equity Total Total assets (a) $ 736 $ 409 $ 1,145 $ 636 $ 443 $ 1,079 Total liabilities (a) 216 225 441 33 227 260 Exelon's ownership interest in VIE (a) — 163 163 — 191 191 Other ownership interests in VIE (a) 520 21 541 604 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 September 30, 2020 and December 31, 2019. As of September 30, 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)	9 Months Ended
	Sep. 30, 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 PHI DPL Three Months Ended September 30, 2020 Operating lease income $ 30 $ 28 $ 1 $ 1 Variable lease income 76 76 — — Three Months Ended September 30, 2019 Operating lease income $ 30 $ 29 $ 1 $ 1 Variable lease income 80 80 — — Nine Months Ended September 30, 2020 Operating lease income $ 48 $ 43 $ 3 $ 3 Variable lease income 225 224 1 1 Nine Months Ended September 30, 2019 Operating lease income $ 48 $ 44 $ 3 $ 3 Variable lease income 209 206 3 3 Taxes other than income taxes Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended September 30, 2020 Utility taxes (a) $ 237 $ 26 $ 66 $ 41 $ 21 $ 83 $ 77 $ 5 $ 1 Property 152 66 7 4 42 32 21 10 1 Payroll 59 29 7 4 4 6 2 1 1 Three Months Ended September 30, 2019 Utility taxes (a) $ 241 $ 29 $ 66 $ 38 $ 21 $ 86 $ 81 $ 5 $ — Property 148 66 7 5 39 31 21 9 — Payroll 57 28 7 3 4 6 2 1 1 Nine Months Ended September 30, 2020 Utility taxes (a) $ 651 $ 75 $ 181 $ 102 $ 65 $ 228 $ 210 $ 16 $ 2 Property 449 199 23 12 121 94 63 29 2 Payroll 183 88 21 12 13 21 6 4 3 Nine Months Ended September 30, 2019 Utility taxes (a) $ 672 $ 87 $ 183 $ 102 $ 68 $ 231 $ 217 $ 14 $ — Property 444 205 22 12 114 91 64 25 2 Payroll 185 92 21 11 13 20 5 3 2 __________ (a) Generation’s utility tax represents gross receipts tax related to its retail operations, and the Utility Registrants' utility taxes represents municipal and state utility taxes and gross receipts taxes related to their operating revenues. The offsetting collection of utility taxes from customers is recorded in revenues in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Other, Net Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended September 30, 2020 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 50 $ 50 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 23 23 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units 398 398 — — — — — — — Non-regulatory agreement units 254 254 — — — — — — — Regulatory offset to NDT fund-related activities (b) (359) (359) — — — — — — — Decommissioning-related activities 366 366 — — — — — — — AFUDC — Equity 27 — 7 5 6 9 7 1 1 Non-service net periodic benefit cost 15 — — — — — — — — Three Months Ended September 30, 2019 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 67 $ 67 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 33 33 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units 89 89 — — — — — — — Non-regulatory agreement units 55 55 — — — — — — — Regulatory offset to NDT fund-related activities (b) (125) (125) — — — — — — — Decommissioning-related activities 119 119 — — — — — — — AFUDC — Equity 22 — 4 3 6 9 7 1 1 Non-service net periodic benefit cost (2) — — — — — — — — Other, net Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2020 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 127 $ 127 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 127 127 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units 111 111 — — — — — — — Non-regulatory agreement units 1 1 — — — — — — — Regulatory offset to NDT fund-related activities (b) (192) (192) — — — — — — — Decommissioning-related activities 174 174 — — — — — — — AFUDC — Equity 76 — 22 12 16 26 20 3 3 Non-service net periodic benefit cost 38 — — — — — — — — Nine Months Ended September 30, 2019 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 197 $ 197 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 316 316 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units 565 565 — — — — — — — Non-regulatory agreement units 236 236 — — — — — — — Regulatory offset to NDT fund-related activities (b) (611) (611) — — — — — — — Decommissioning-related activities 703 703 — — — — — — — AFUDC — Equity 64 — 13 9 16 26 18 3 4 Non-service net periodic benefit cost 8 — — — — — — — — __________ (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 Nine Months Ended September 30, 2020 Property, plant, and equipment (a) $ 2,831 $ 1,121 $ 689 $ 238 $ 293 $ 436 $ 191 $ 116 $ 104 Amortization of regulatory assets (a) 434 — 152 21 112 149 91 27 30 Amortization of intangible assets, net (a) 47 40 — — — — — — — Amortization of energy contract assets and liabilities (b) 24 22 — — — — — — — Nuclear fuel (c) 708 708 — — — — — — — ARO accretion (d) 375 375 — — — — — — — Total depreciation, amortization and accretion $ 4,419 $ 2,266 $ 841 $ 259 $ 405 $ 585 $ 282 $ 143 $ 134 Nine Months Ended September 30, 2019 Property, plant, and equipment (a) $ 2,803 $ 1,184 $ 661 $ 225 $ 263 $ 405 $ 178 $ 109 $ 89 Amortization of regulatory assets (a) 390 — 106 22 105 157 103 29 25 Amortization of intangible assets, net (a) 44 37 — — — — — — — Amortization of energy contract assets and liabilities (b) 14 14 — — — — — — — Nuclear fuel (c) 771 771 — — — — — — — ARO accretion (d) 371 371 — — — — — — — Total depreciation, amortization and accretion $ 4,393 $ 2,377 $ 767 $ 247 $ 368 $ 562 $ 281 $ 138 $ 114 __________ (a) Included in Depreciation and amortization in the Registrants' Consolidated Statements of Operations and Comprehensive Income. (b) Included in Operating revenues or Purchased power and fuel expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (c) Included in Purchased power and fuel expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (d) Included in Operating and maintenance expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Other non-cash operating activities Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2020 Pension and non-pension postretirement benefit costs $ 310 $ 89 $ 85 $ 4 $ 46 $ 52 $ 11 $ 6 $ 10 Provision for uncollectible accounts 130 16 23 38 12 41 24 15 2 Other decommissioning-related activity (a) (301) (301) — — — — — — — Energy-related options (b) 79 79 — — — — — — — True-up adjustments to decoupling mechanisms and formula rates (c) 66 — 51 (10) 10 15 (20) 15 20 Severance Costs 96 88 1 — — — — — — Provision for excess and obsolete inventory 119 118 1 1 — (1) — (1) — Long-term incentive plan (8) — — — — — — — — Amortization of operating ROU asset 185 135 1 — 23 21 5 6 2 Deferred Prosecution Agreement payments (d) 200 — 200 — — — — — — Nine Months Ended September 30, 2019 Pension and non-pension postretirement benefit costs $ 324 $ 98 $ 70 $ 9 $ 45 $ 71 $ 19 $ 11 $ 12 Provision for uncollectible accounts 89 20 26 22 5 16 7 2 6 Other decommissioning-related activity (a) (400) (400) — — — — — — — Energy-related options (b) 21 21 — — — — — — — True-up adjustments to decoupling mechanisms and formula rates (e) 72 — 80 — — (8) (9) 1 — Long-term incentive plan 33 — — — — — — — — Amortization of operating ROU asset 193 138 2 — 23 26 6 7 4 Change in environmental liabilities 23 — — — — 23 23 — — __________ (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) For ComEd, reflects the true-up adjustments in regulatory assets and liabilities associated with its distribution, energy efficiency, distributed generation, and transmission formula rates. For BGE, Pepco, and DPL, reflects the change in regulatory assets and liabilities associated with their decoupling mechanisms and transmission formula rates. For PECO and ACE, reflects the change in regulatory assets and liabilities associated with their transmission formula rates. See Note 2 — Regulatory Matters for additional information. (d) See Note 14 — Commitments and Contingencies for additional information related to the Deferred Prosecution Agreement. (e) For ComEd, reflects the true-up adjustments in regulatory assets and liabilities associated with its distribution and energy efficiency formula rates. For Pepco and DPL, reflects the change in regulatory assets and liabilities associated with their decoupling mechanisms. 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 September 30, 2020 Cash and cash equivalents $ 1,858 $ 623 $ 76 $ 242 $ 326 $ 196 $ 125 $ 26 $ 13 Restricted cash 485 100 305 7 1 38 33 — 4 Restricted cash included in other long-term assets 137 — 127 — — 10 — — 10 Total cash, cash equivalents and restricted cash $ 2,480 $ 723 $ 508 $ 249 $ 327 $ 244 $ 158 $ 26 $ 27 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 September 30, 2019 Cash and cash equivalents $ 1,683 $ 1,019 $ 76 $ 224 $ 130 $ 99 $ 18 $ 11 $ 13 Restricted cash 309 126 124 6 1 38 34 — 3 Restricted cash included in other long-term assets 186 — 171 — — 15 — — 15 Total cash, cash equivalents and restricted cash $ 2,178 $ 1,145 $ 371 $ 230 $ 131 $ 152 $ 52 $ 11 $ 31 December 31, 2018 Cash and cash equivalents $ 1,349 $ 750 $ 135 $ 130 $ 7 $ 124 $ 16 $ 23 $ 7 Restricted cash 247 153 29 5 6 43 37 1 4 Restricted cash included in other long-term assets 185 — 166 — — 19 — — 19 Total cash, cash equivalents and restricted cash $ 1,781 $ 903 $ 330 $ 135 $ 13 $ 186 $ 53 $ 24 $ 30 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 September 30, 2020 Compensation-related accruals (a) $ 898 $ 352 $ 147 $ 60 $ 72 $ 95 $ 31 $ 16 $ 14 Taxes accrued 403 183 55 25 63 84 65 10 3 Interest accrued 440 79 64 36 40 80 38 21 21 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)	9 Months Ended
	Sep. 30, 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 September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Operating revenues from affiliates: ComEd (a)(b) $ 71 $ 83 $ 241 $ 266 PECO (c) 68 43 146 123 BGE (d) 84 65 252 199 PHI 105 83 288 254 Pepco (e) 80 66 219 188 DPL (f) 21 14 60 50 ACE (g) 4 3 9 16 Other 3 1 5 2 Total operating revenues from affiliates (Generation) $ 331 $ 275 $ 932 $ 844 __________ (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 and nine months ended September 30, 2020 , respectively, ComEd’s Purchased power from Generation of $71 million and $252 million is recorded as Operating revenues from ComEd of $71 million and $241 million and as Purchased power and fuel from ComEd of less than $1 million and $11 million at Generation. For the three and nine months ended September 30, 2019 , respectively, ComEd’s Purchased power from Generation of $83 million and $270 million is recorded as Operating revenues from ComEd of $83 million and $266 million and as Purchased power and fuel from ComEd of less than $1 million and $4 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 September 30, Nine Months Ended September 30, Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 2020 2019 2020 2019 Exelon BSC $ 148 $ 125 $ 390 $ 357 PHISCO 15 16 45 57 Generation BSC $ 133 $ 138 $ 406 $ 434 13 18 37 44 ComEd BSC 65 72 204 195 49 37 133 98 PECO BSC 34 36 107 110 20 22 53 68 BGE BSC 38 38 120 116 30 30 88 89 PHI BSC 36 35 107 102 36 18 79 58 PHISCO — — — — 15 16 45 57 Pepco BSC 20 21 61 64 14 8 29 25 PHISCO 28 29 90 92 7 8 20 26 DPL BSC 13 13 38 39 12 5 26 16 PHISCO 24 24 73 74 4 4 13 16 ACE BSC 11 10 32 31 10 4 22 13 PHISCO 21 22 65 67 4 4 12 15 Current Receivables from/Payables to affiliates The following tables present current receivables from affiliates and current payables to affiliates: September 30, 2020 Receivables from affiliates: Payables to affiliates: Generation ComEd PECO BGE ACE BSC PHISCO Other Total Generation $ 19 $ — $ — $ — $ 69 $ — $ 25 $ 113 ComEd $ 56 (a) — — — 49 — 5 110 PECO 17 — — — 24 — 6 47 BGE 8 — — — 29 — 2 39 PHI — — — — — 3 — 10 13 Pepco 13 — — — — 16 12 2 43 DPL 2 — — — — 11 9 1 23 ACE 4 — — — 10 10 — 24 Other 9 1 — — 1 — — 11 Total $ 109 $ 20 $ — $ — $ 1 $ 211 $ 31 $ 51 $ 423 December 31, 2019 Receivables from affiliates: Payables to affiliates: Generation ComEd PECO BGE 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) As of September 30, 2020 and December 31, 2019, Generation had a contract liability with ComEd for $28 million and $37 million, respectively, that was included in Other current liabilities on Generation’s Consolidated Balance Sheets. At September 30, 2020 and December 31, 2019, ComEd had a Current Payable to Generation of $28 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: September 30, 2020 December 31, 2019 ComEd $ 2,445 $ 2,622 PECO 443 480 Other — 1 Total: $ 2,888 $ 3,103 Long-term debt to financing trusts The following table presents Long-term debt to financing trusts: September 30, 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.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 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 & 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 September 30, 2020 and December 31, 2019 and for the three and nine months ended September 30, 2020 and 2019 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 Combined
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 was 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 was 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, Pepco, DPL, and ACE’s Consolidated Balance Sheets. See Note 3 - Regulatory Matters of the 2019 Form 10-K for additional information regarding the regulatory recovery of credit losses on customer accounts receivable at ComEd, BGE, Pepco, DPL, 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 not material. 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)	9 Months Ended
	Sep. 30, 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 DPL - Maryland (Electric) December 5, 2019 (amended April 23, 2020) 17 12 9.60 % July 14, 2020 July 16, 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 PECO - Pennsylvania (Natural Gas) September 30, 2020 69 10.95 % Second quarter of 2021 BGE - Maryland (Electric and Natural Gas) (b) May 15, 2020 228 10.1 % Fourth quarter of 2020 Pepco - District of Columbia (Electric) (c) May 30, 2019 (amended June 1, 2020) 136 9.7 % First quarter of 2021 Pepco - Maryland (Electric) (d) October 26, 2020 110 10.2 % Second quarter of 2021 DPL - Delaware (Natural Gas) (e) February 21, 2020 (amended October 9, 2020) 7 10.3 % First quarter of 2021 DPL - Delaware (Electric) (f) March 6, 2020 (amended October 26, 2020) 24 10.3 % Second 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 for 2021 through 2023 and total requested revenue requirement increases in 2023 of $137 million related to electric distribution and $91 million related to natural gas distribution to recover capital investments made in late 2019 and planned capital investments from 2020 to 2023. (c) Pepco filed the multi-year plan enhanced proposal as an alternative to address the impacts of COVID-19. Reflects a three-year cumulative multi-year plan for 2020 through 2022 and requested revenue requirement increases of $73 million in 2022 and $63 million in 2023, to recover capital investments made during 2018 through 2020 and planned capital investments through the end of 2022. (d) Reflects a three-year cumulative multi-year plan for April 1, 2021 through March 31, 2024 and total requested revenue requirement increases of $56 million effective April 1, 2023 and $54 million effective April 1, 2024 to recover capital investments made in 2019 and 2020 and planned capital investments through March 31, 2024. (e) The rates went into effect on September 21, 2020, subject to refund. (f) The rates went into effect on October 6, 2020, subject to refund.
Public Utilities Transmission Rate Filings [Table Text Block]	For 2020, the following total increases/(decreases) were included in ComEd’s, PECO's, BGE’s, Pepco's, DPL's, and ACE's electric transmission formula rate filings: Registrant (a) Initial Revenue Requirement Increase (Decrease) Annual Reconciliation Decrease Total Revenue Requirement Increase (Decrease) (c) Allowed Return on Rate Base (d) Allowed ROE (e) ComEd $ 18 $ (4) $ 14 8.17 % 11.50 % PECO (b) 5 (28) (23) 7.47 % 10.35 % BGE 16 (3) 4 7.26 % 10.50 % Pepco 2 (46) (44) 7.81 % 10.50 % DPL (4) (40) (44) 7.20 % 10.50 % ACE 5 (25) (20) 7.40 % 10.50 % __________ (a) All rates are effective June 2020, subject to review by interested parties, which is anticipated to be completed by the fourth quarter of 2020 or first quarter of 2021 for ComEd, BGE, Pepco, DPL, and ACE and second quarter of 2021 for PECO. (b) PECO posted a revised filing to the PJM website on July 17, 2020 reflecting updates to the formula rate based on the FERC order dated July 9, 2020. (c) The decrease in PECO's transmission revenue requirement relates to refunds from December 1, 2017, in accordance with the settlement agreement dated July 22, 2019. The increase in BGE's transmission revenue requirement includes a $9 million reduction related to a FERC-approved dedicated facilities charge to recover the costs of providing transmission service to specifically designated load by BGE. ComEd, BGE, Pepco, DPL, and ACE’s transmission revenue requirement include a decrease related to the April 24, 2020 settlement agreement related to excess deferred income taxes. Refer to Transmission-Related Income Tax Regulatory Assets below for additional information. (d) Represents the weighted average debt and equity return on transmission rate bases. (e) As part of the FERC-approved settlements of ComEd’s 2007 and PECO's 2017 transmission rate cases, the rate of return on common equity is 11.50% and 10.35%, respectively, inclusive of a 50-basis-point incentive adder for being a member of a RTO, and the common equity component of the ratio used to calculate the weighted average debt and equity return for the transmission formula rate is currently capped at 55% and 55.75%, respectively. As part of the FERC-approved settlement of the ROE complaint against BGE, Pepco, DPL, and ACE, the rate of return on common equity is 10.50%, inclusive of a 50-basis-point incentive adder for being a member of a RTO.
Public Utilities Energy Efficiency Revenue [Table Text Block]	Energy Efficiency Formula Rate (Exelon and ComEd). ComEd filed its annual energy efficiency formula rate update with the ICC on May 21, 2020. The filing establishes the revenue requirement used to set the rates that will take effect in January 2021 after the ICC’s review and approval. The revenue requirement requested is based on a reconciliation of the 2019 actual costs plus projected 2020 and 2021 expenditures. Initial Revenue Requirement Increase Annual Reconciliation Increase Total Revenue Requirement Increase Requested Return on Rate Base Requested ROE $ 45 $ 3 $ 48 (a) 6.28 % 8.38 % __________
Regulatory Assets - COVID-19 [Table Text Block]	Exelon and the Utility Registrants recorded the following regulatory assets related to COVID-19: Exelon ComEd PECO BGE PHI Pepco DPL ACE September 30, 2020 $ 60 $ 18 $ 20 $ 11 $ 11 $ 8 $ 3 $ —
Public Utilities General Disclosures [Table Text Block]	The following table presents authorized amounts capitalized for ratemaking purposes related to earnings on shareholders’ investment that are not recognized for financial reporting purposes in Exelon's and the Utility Registrant's Consolidated Balance Sheets. These amounts will be recognized as revenues in the related Consolidated Statements of Operations and Comprehensive Income in the periods they are billable to our customers. Exelon ComEd (a) PECO BGE (b) PHI Pepco (c) DPL (c) ACE September 30, 2020 $ 54 $ — $ — $ 47 $ 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)	9 Months Ended
	Sep. 30, 2020
Contracts with Customers [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table Text Block]	The following table shows the amounts of future revenues expected to be recorded in each year for performance obligations that are unsatisfied or partially unsatisfied as of September 30, 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 $ 92 $ 223 $ 93 $ 53 $ 370 $ 831 Generation 136 313 123 53 275 900 PHI 2 9 8 8 95 122 Pepco 2 7 6 6 75 96 DPL — 1 1 1 10 13 ACE — 1 1 1 10 13
Contract Assets [Member]
Contracts with Customers [Line Items]
Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block]	The following table provides a rollforward of the contract assets reflected in Exelon's and Generation's Consolidated Balance Sheets for the three and nine months ended September 30, 2020 and 2019. The Utility Registrants do not have any contract assets. Exelon Generation Balance as of December 31, 2019 $ 174 $ 174 Amounts reclassified to receivables (19) (19) Revenues recognized 17 17 Balance at March 31, 2020 $ 172 $ 172 Amounts reclassified to receivables (26) (26) Revenues recognized 13 13 Balance at June 30, 2020 $ 159 $ 159 Amounts reclassified to receivables (18) (18) Revenues recognized 19 19 Balance at September 30, 2020 $ 160 $ 160 Exelon Generation Balance as of December 31, 2018 $ 187 $ 187 Amounts reclassified to receivables (26) (26) Revenues recognized 26 26 Balance at March 31, 2019 $ 187 $ 187 Amounts reclassified to receivables (18) (18) Revenues recognized 27 27 Balance at June 30, 2019 $ 196 $ 196 Amounts reclassified to receivables (65) (65) Revenues recognized 39 39 Balance at September 30, 2019 $ 170 $ 170
Contract Liabilities [Member]
Contracts with Customers [Line Items]
Contract with Customer, Contract Asset, Contract Liability, and Receivable [Table Text Block]	The following table provides a rollforward of the contract liabilities reflected in Exelon's, Generation's, PHI's, Pepco's, DPL's, and ACE'S Consolidated Balance Sheets for the three and nine months ended September 30, 2020 and 2019. As of September 30, 2020 and December 31, 2019, ComEd's, PECO's, and BGE's contract liabilities were immaterial. Exelon Generation PHI Pepco DPL ACE Balance as of December 31, 2019 $ 33 $ 71 $ — $ — $ — $ — Consideration received or due 20 55 — — — — Revenues recognized (24) (70) — — — — Balance at March 31, 2020 $ 29 $ 56 $ — $ — $ — $ — Consideration received or due 13 34 — — — — Revenues recognized (22) (63) — — — — Balance at June 30, 2020 $ 20 $ 27 $ — $ — $ — $ — Consideration received or due 154 94 124 98 13 13 Revenues recognized (25) (65) (2) (2) — — Balance at September 30, 2020 $ 149 $ 56 $ 122 $ 96 $ 13 $ 13 Exelon Generation PHI Pepco DPL ACE Balance as of December 31, 2018 $ 27 $ 42 $ — $ — $ — $ — Consideration received or due 21 63 — — — — Revenues recognized (23) (66) — — — — Balance at March 31, 2019 $ 25 $ 39 $ — $ — $ — $ — Consideration received or due 17 52 — — — — Revenues recognized (21) (65) — — — — Balance at June 30, 2019 $ 21 $ 26 $ — $ — $ — $ — Consideration received or due 27 83 — — — — Revenues recognized (22) (61) — — — — Balance at September 30, 2019 $ 26 $ 48 $ — $ — $ — $ — The following table reflects revenues recognized in the three and nine months ended September 30, 2020 and 2019, which were included in contract liabilities at December 31, 2019 and 2018, respectively: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Exelon $ 2 $ 3 $ 25 $ 17 Generation 2 3 63 32

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2020
Segment Tables [Line Items]
Analysis and reconciliation of reportable segment information	An analysis and reconciliation of the Registrants’ reportable segment information to the respective information in the consolidated financial statements for the three and nine months ended September 30, 2020 and 2019 is as follows: Three Months Ended September 30, 2020 and 2019 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Operating revenues (b) : 2020 Competitive businesses electric revenues $ 4,201 $ — $ — $ — $ — $ — $ (326) $ 3,875 Competitive businesses natural gas revenues 323 — — — — — — 323 Competitive businesses other revenues 135 — — — — — (3) 132 Rate-regulated electric revenues — 1,643 759 646 1,339 — (22) 4,365 Rate-regulated natural gas revenues — — 54 85 23 — (3) 159 Shared service and other revenues — — — — 6 484 (491) (1) Total operating revenues $ 4,659 $ 1,643 $ 813 $ 731 $ 1,368 $ 484 $ (845) $ 8,853 2019 Competitive businesses electric revenues $ 4,314 $ — $ — $ — $ — $ — $ (275) $ 4,039 Competitive businesses natural gas revenues 265 — — — — — 1 266 Competitive businesses other revenues 195 — — — — — (1) 194 Rate-regulated electric revenues — 1,583 716 619 1,357 — (7) 4,268 Rate-regulated natural gas revenues — — 62 84 20 — (3) 163 Shared service and other revenues — — — — 3 474 (478) (1) Total operating revenues $ 4,774 $ 1,583 $ 778 $ 703 $ 1,380 $ 474 $ (763) $ 8,929 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Intersegment revenues (c) : 2020 $ 331 $ 15 $ 3 $ 6 $ 6 $ 485 $ (845) $ 1 2019 275 4 1 6 4 474 (764) — Depreciation and amortization: 2020 $ 558 $ 294 $ 85 $ 133 $ 200 $ 19 $ — $ 1,289 2019 407 259 83 116 193 25 — 1,083 Operating expenses: 2020 $ 4,727 $ 1,302 $ 658 $ 642 $ 1,102 $ 489 $ (833) $ 8,087 2019 4,274 1,256 595 612 1,124 457 (759) 7,559 Interest expense, net: 2020 $ 80 $ 95 $ 39 $ 34 $ 67 $ 89 $ — $ 404 2019 109 91 33 31 66 79 — 409 Income (loss) before income taxes: 2020 $ 219 $ 256 $ 122 $ 61 $ 215 $ (87) $ — $ 786 2019 501 245 154 67 203 (68) — 1,102 Income Taxes: 2020 $ 100 $ 60 $ (16) $ 8 $ (1) $ 65 $ — $ 216 2019 87 45 14 12 14 — — 172 Net income (loss): 2020 $ 117 $ 196 $ 138 $ 53 $ 216 $ (151) $ — $ 569 2019 244 200 140 55 189 (68) — 760 Capital Expenditures: 2020 $ 282 $ 554 $ 312 $ 290 $ 386 $ 9 $ — $ 1,833 2019 392 452 228 300 308 7 — 1,687 __________ (a) Other primarily includes Exelon’s corporate operations, shared service entities, and other financing and investment activities. (b) 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. (c) 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. See Note 18 — Related Party Transactions for additional information on intersegment revenues. PHI: Pepco DPL ACE Other (a) Intersegment PHI Operating revenues (b) : 2020 Rate-regulated electric revenues $ 611 $ 314 $ 420 $ — $ (6) $ 1,339 Rate-regulated natural gas revenues — 23 — — — 23 Shared service and other revenues — — — 91 (85) 6 Total operating revenues $ 611 $ 337 $ 420 $ 91 $ (91) $ 1,368 2019 Rate-regulated electric revenues $ 642 $ 299 $ 419 $ — $ (3) $ 1,357 Rate-regulated natural gas revenues — 20 — — — 20 Shared service and other revenues — — — 92 (89) 3 Total operating revenues $ 642 $ 319 $ 419 $ 92 $ (92) $ 1,380 Intersegment revenues (c) : 2020 $ 3 $ 3 $ 1 $ 90 $ (91) $ 6 2019 2 1 1 93 (93) 4 Depreciation and amortization: 2020 $ 96 $ 48 $ 48 $ 8 $ — $ 200 2019 95 46 43 9 — 193 Operating expenses: 2020 $ 465 $ 296 $ 338 $ 94 $ (91) $ 1,102 2019 515 268 340 95 (94) 1,124 Interest expense, net: 2020 $ 35 $ 15 $ 15 $ 2 $ — $ 67 2019 33 15 15 3 — 66 Income (loss) before income taxes: 2020 $ 121 $ 28 $ 68 $ (2) $ — $ 215 2019 (d) 103 38 65 (3) — 203 Income Taxes: 2020 $ 3 $ 1 $ (7) $ 2 $ — $ (1) 2019 5 5 2 2 — 14 Net income (loss): 2020 $ 118 $ 27 $ 75 $ (4) $ — $ 216 2019 98 33 63 (5) — 189 Capital Expenditures: 2020 $ 188 $ 94 $ 103 $ 1 $ — $ 386 2019 157 85 73 (7) — 308 __________ (a) Other primarily includes PHI’s corporate operations, shared service entities, and other financing and investment activities. (b) 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. (c) Includes intersegment revenues with ComEd, BGE, and PECO, which are eliminated at Exelon. (d) The Income (loss) before income taxes amounts in Other and Intersegment Eliminations have been adjusted by an offsetting $195 million for consistency with the Exelon consolidating disclosure above.
Analysis and reconciliation of reportable segment revenues for Generation	The following tables disaggregate the Registrants' revenue recognized from contracts with customers into categories that depict how the nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factors. For Generation, the disaggregation of revenues reflects Generation’s two primary products of power sales and natural gas sales, with further disaggregation of power sales provided by geographic region. For the Utility Registrants, the disaggregation of revenues reflects the two primary utility services of rate-regulated electric sales and rate-regulated natural gas sales (where applicable), with further disaggregation of these tariff sales provided by major customer groups. Exelon’s disaggregated revenues are consistent with Generation and the Utility Registrants, but exclude any intercompany revenues. Competitive Business Revenues (Generation): Three Months Ended September 30, 2020 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,327 $ (20) $ 1,307 $ 6 $ 1,313 Midwest 974 68 1,042 1 1,043 New York 401 5 406 — 406 ERCOT 249 74 323 7 330 Other Power Regions 937 186 1,123 (14) 1,109 Total Competitive Businesses Electric Revenues 3,888 313 4,201 — 4,201 Competitive Businesses Natural Gas Revenues 169 154 323 — 323 Competitive Businesses Other Revenues (c) 85 50 135 — 135 Total Generation Consolidated Operating Revenues $ 4,142 $ 517 $ 4,659 $ — $ 4,659 Three Months Ended September 30, 2019 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 1,351 $ 10 $ 1,361 $ 3 $ 1,364 Midwest 1,052 47 1,099 (17) 1,082 New York 414 15 429 — 429 ERCOT 288 72 360 5 365 Other Power Regions 873 192 1,065 (25) 1,040 Total Competitive Businesses Electric Revenues 3,978 336 4,314 (34) 4,280 Competitive Businesses Natural Gas Revenues 160 105 265 34 299 Competitive Businesses Other Revenues (c) 112 83 195 — 195 Total Generation Consolidated Operating Revenues $ 4,250 $ 524 $ 4,774 $ — $ 4,774 __________ (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 o f $37 million and $77 million in 2020 and 2019, respectively, and the elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Three Months Ended September 30, 2020 Three Months Ended September 30, 2019 RNF from external customers (a) Intersegment Total RNF RNF from external customers (a) Intersegment Total RNF Mid-Atlantic $ 586 $ 5 $ 591 $ 684 $ 5 $ 689 Midwest 748 2 750 763 (16) 747 New York 281 4 285 288 3 291 ERCOT 141 6 147 76 (4) 72 Other Power Regions 253 (28) 225 212 (28) 184 Total Revenues net of purchased power and fuel expense for Reportable Segments 2,009 (11) 1,998 2,023 (40) 1,983 Other (b) 336 11 347 100 40 140 Total Generation Revenues net of purchased power and fuel expense $ 2,345 $ — $ 2,345 $ 2,123 $ — $ 2,123 __________ (a) Includes purchases and sales from/to third parties and affiliated sales to the Utility Registrants. (b) Other represents activities not allo cated to a region. See text above for a description of included activities. Includes unrealized mark-to-market gains of $255 million and $17 million in 2020 and 2019, respectively, accelerated nuclear fuel amortization associated with announced early pla nt retirements as discussed in Note 6 - Early Plant Retirements o f $24 million , which includes an impairment charge of $10 million , and $3 million decrease to revenue net of purchased power and fuel expense 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 September 30, 2020 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 920 $ 518 $ 389 $ 763 $ 307 $ 193 $ 263 Small commercial & industrial 379 104 65 134 36 45 53 Large commercial & industrial 135 66 113 262 195 21 46 Public authorities & electric railroads 10 7 7 14 8 3 3 Other (a) 234 58 78 141 47 44 50 Total rate-regulated electric revenues (b) $ 1,678 $ 753 $ 652 $ 1,314 $ 593 $ 306 $ 415 Rate-regulated natural gas revenues Residential $ — $ 32 $ 55 $ 11 $ — $ 11 $ — Small commercial & industrial — 16 9 6 — 6 — Large commercial & industrial — — 21 1 — 1 — Transportation — 6 — 3 — 3 — Other (c) — 1 3 2 — 2 — Total rate-regulated natural gas revenues (d) $ — $ 55 $ 88 $ 23 $ — $ 23 $ — Total rate-regulated revenues from contracts with customers $ 1,678 $ 808 $ 740 $ 1,337 $ 593 $ 329 $ 415 Other revenues Revenues from alternative revenue programs $ (38) $ 5 $ (9) $ 31 $ 18 $ 8 $ 5 Other rate-regulated electric revenues (e) 3 — — — — — — Other rate-regulated natural gas revenues (e) — — — — — — — Total other revenues $ (35) $ 5 $ (9) $ 31 $ 18 $ 8 $ 5 Total rate-regulated revenues for reportable segments $ 1,643 $ 813 $ 731 $ 1,368 $ 611 $ 337 $ 420 Three Months Ended September 30, 2019 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 865 $ 479 $ 352 $ 741 $ 311 $ 178 $ 252 Small commercial & industrial 393 109 64 147 41 48 58 Large commercial & industrial 141 63 116 297 222 26 49 Public authorities & electric railroads 12 9 7 17 11 3 3 Other (a) 222 63 82 164 58 50 56 Total rate-regulated electric revenues (b) $ 1,633 $ 723 $ 621 $ 1,366 $ 643 $ 305 $ 418 Rate-regulated natural gas revenues Residential $ — $ 38 $ 49 $ 9 $ — $ 9 $ — Small commercial & industrial — 17 9 4 — 4 — Large commercial & industrial — — 20 1 — 1 — Transportation — 5 — 4 — 4 — Other (c) — 2 5 2 — 2 — Total rate-regulated natural gas revenues (d) $ — $ 62 $ 83 $ 20 $ — $ 20 $ — Total rate-regulated revenues from contracts with customers $ 1,633 $ 785 $ 704 $ 1,386 $ 643 $ 325 $ 418 Other revenues Revenues from alternative revenue programs $ (56) $ (11) $ (5) $ (9) $ (3) $ (6) $ 1 Other rate-regulated electric revenues (e) 6 4 3 3 2 — — Other rate-regulated natural gas revenues (e) — — 1 — — — — Total other revenues $ (50) $ (7) $ (1) $ (6) $ (1) $ (6) $ 1 Total rate-regulated revenues for reportable segments $ 1,583 $ 778 $ 703 $ 1,380 $ 642 $ 319 $ 419 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates of $15 million, $3 million, $3 million, $6 million, $3 million, $3 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE, respectively, in 2020 and $4 million, $1 million, $2 million, $4 million, $2 million, $1 million and $1 million at ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE, respectively, in 2019. (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. Electric and Gas Revenue by Customer Class (Utility Registrants): Nine Months Ended September 30, 2020 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 2,389 $ 1,277 $ 1,034 $ 1,825 $ 779 $ 501 $ 545 Small commercial & industrial 1,067 291 183 355 101 127 127 Large commercial & industrial 388 174 311 755 558 66 131 Public authorities & electric railroads 33 21 20 45 25 10 10 Other (a) 663 171 233 471 166 148 159 Total rate-regulated electric revenues (b) $ 4,540 $ 1,934 $ 1,781 $ 3,451 $ 1,629 $ 852 $ 972 Rate-regulated natural gas revenues Residential $ — $ 252 $ 342 $ 68 $ — $ 68 $ — Small commercial & industrial — 86 55 30 — 30 — Large commercial & industrial — — 96 3 — 3 — Transportation — 18 — 10 — 10 — Other (c) — 3 16 5 — 5 — Total rate-regulated natural gas revenues (d) $ — $ 359 $ 509 $ 116 $ — $ 116 $ — Total rate-regulated revenues from contracts with customers $ 4,540 $ 2,293 $ 2,290 $ 3,567 $ 1,629 $ 968 $ 972 Other revenues Revenues from alternative revenue programs $ (51) $ 10 $ (10) $ (15) $ 20 $ (15) $ (20) Other rate-regulated electric revenues (e) 10 3 3 2 1 1 — Other rate-regulated natural gas revenues (e) — — 1 — — — — Total other revenues $ (41) $ 13 $ (6) $ (13) $ 21 $ (14) $ (20) Total rate-regulated revenues for reportable segments $ 4,499 $ 2,306 $ 2,284 $ 3,554 $ 1,650 $ 954 $ 952 Nine Months Ended September 30, 2019 Revenues from contracts with customers ComEd PECO BGE PHI Pepco DPL ACE Rate-regulated electric revenues Residential $ 2,221 $ 1,231 $ 1,019 $ 1,816 $ 792 $ 499 $ 525 Small commercial & industrial 1,103 304 193 387 114 141 132 Large commercial & industrial 399 163 335 843 633 75 135 Public authorities & electric railroads 35 23 20 47 27 10 10 Other (a) 660 186 242 481 166 151 164 Total rate-regulated electric revenues (b) $ 4,418 $ 1,907 $ 1,809 $ 3,574 $ 1,732 $ 876 $ 966 Rate-regulated natural gas revenues Residential $ — $ 285 $ 327 $ 64 $ — $ 64 $ — Small commercial & industrial — 122 55 30 — 30 — Large commercial & industrial — 1 93 4 — 4 — Transportation — 18 — 11 — 11 — Other (c) — 5 19 6 — 6 — Total rate-regulated natural gas revenues (d) $ — $ 431 $ 494 $ 115 $ — $ 115 $ — Total rate-regulated revenues from contracts with customers $ 4,418 $ 2,338 $ 2,303 $ 3,689 $ 1,732 $ 991 $ 966 Other revenues Revenues from alternative revenue programs $ (98) $ (16) $ 11 $ 4 $ 10 $ (6) $ — Other rate-regulated electric revenues (e) 22 10 10 7 6 1 — Other rate-regulated natural gas revenues (e) — 1 3 — — 1 — Total other revenues $ (76) $ (5) $ 24 $ 11 $ 16 $ (4) $ — Total rate-regulated revenues for reportable segments $ 4,342 $ 2,333 $ 2,327 $ 3,700 $ 1,748 $ 987 $ 966 __________ (a) Includes revenues from transmission revenue from PJM, wholesale electric revenue and mutual assistance revenue. (b) Includes operating revenues from affiliates of $31 million, $6 million, $9 million, $13 million, $6 million, $7 million and $3 million at ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE, respectively, in 2020 and $13 million, $4 million, $5 million, $11 million, $5 million, $5 million and $2 million at ComEd, PECO, BGE, PHI, Pepco, DPL, and ACE, respectively, in 2019. (c) Includes revenues from off-system natural gas sales. (d) Includes operating revenues from affiliates of $1 million and $7 million at PECO and BGE, respectively, in 2020 and less than $1 million and $13 million at PECO and BGE, respectively, in 2019. (e) Includes late payment charge revenues.
Year to Date [Member]
Segment Tables [Line Items]
Analysis and reconciliation of reportable segment information	Nine Months Ended September 30, 2020 and 2019 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Operating revenues (b) : 2020 Competitive businesses electric revenues $ 11,367 $ — $ — $ — $ — $ — $ (920) $ 10,447 Competitive businesses natural gas revenues 1,348 — — — — — (3) 1,345 Competitive businesses other revenues 557 — — — — — (5) 552 Rate-regulated electric revenues — 4,499 1,948 1,763 3,425 — (50) 11,585 Rate-regulated natural gas revenues — — 358 521 116 — (5) 990 Shared service and other revenues — — — — 13 1,440 (1,447) 6 Total operating revenues $ 13,272 $ 4,499 $ 2,306 $ 2,284 $ 3,554 $ 1,440 $ (2,430) $ 24,925 2019 Competitive businesses electric revenues $ 12,365 $ — $ — $ — $ — $ — $ (840) $ 11,525 Competitive businesses natural gas revenues 1,479 — — — — — — 1,479 Competitive businesses other revenues 436 — — — — — (4) 432 Rate-regulated electric revenues — 4,342 1,901 1,817 3,574 — (25) 11,609 Rate-regulated natural gas revenues — — 432 510 116 — (12) 1,046 Shared service and other revenues — — — — 10 1,410 (1,415) 5 Total operating revenues $ 14,280 $ 4,342 $ 2,333 $ 2,327 $ 3,700 $ 1,410 $ (2,296) $ 26,096 Intersegment revenues (c) : 2020 $ 932 $ 31 $ 7 $ 16 $ 13 $ 1,435 $ (2,430) $ 4 2019 844 13 4 18 11 1,410 (2,300) — Depreciation and amortization: 2020 $ 1,161 $ 841 $ 259 $ 405 $ 585 $ 61 $ — $ 3,312 2019 1,221 767 247 368 562 72 — 3,237 Operating expenses: 2020 $ 12,674 $ 3,798 $ 1,900 $ 1,903 $ 3,057 $ 1,452 $ (2,397) $ 22,387 2019 13,333 3,431 1,783 1,936 3,106 1,405 (2,291) 22,703 Interest expense, net: 2020 $ 277 $ 287 $ 108 $ 99 $ 201 $ 269 $ — $ 1,241 2019 336 268 100 89 197 231 — 1,221 Generation ComEd PECO BGE PHI Other (a) Intersegment Exelon Income (loss) before income taxes: 2020 $ 532 $ 446 $ 310 $ 299 $ 340 $ (262) $ — $ 1,665 2019 1,355 674 461 320 436 (218) — 3,028 Income Taxes: 2020 $ 41 $ 142 $ (7) $ 26 $ (77) $ 16 $ — $ 141 2019 388 130 51 59 25 (27) — 626 Net income (loss): 2020 $ 485 $ 304 $ 317 $ 273 $ 418 $ (278) $ — $ 1,519 2019 784 544 410 261 412 (191) — 2,220 Capital Expenditures: 2020 $ 1,212 $ 1,583 $ 824 $ 838 $ 1,072 $ 77 $ — $ 5,606 2019 1,282 1,413 675 842 1,006 41 — 5,259 Total assets: September 30, 2020 $ 47,372 $ 34,243 $ 12,334 $ 11,370 $ 23,394 $ 9,070 $ (10,016) $ 127,767 December 31, 2019 48,995 32,765 11,469 10,634 22,719 8,484 (10,089) 124,977 __________ (a) Other primarily includes Exelon’s corporate operations, shared service entities, and other financing and investment activities. (b) 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. (c) 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. See Note 18 — Related Party Transactions for additional information on intersegment revenues. PHI: Pepco DPL ACE Other (a) Intersegment PHI Operating revenues (b) : 2020 Rate-regulated electric revenues $ 1,650 $ 838 $ 952 $ — $ (15) $ 3,425 Rate-regulated natural gas revenues — 116 — — — 116 Shared service and other revenues — — — 279 (266) 13 Total operating revenues $ 1,650 $ 954 $ 952 $ 279 $ (281) $ 3,554 2019 Rate-regulated electric revenues $ 1,748 $ 871 $ 966 $ (1) $ (10) $ 3,574 Rate-regulated natural gas revenues — 116 — — — 116 Shared service and other revenues — — — 298 (288) 10 Total operating revenues $ 1,748 $ 987 $ 966 $ 297 $ (298) $ 3,700 Intersegment revenues (c) : 2020 $ 6 $ 7 $ 3 $ 278 $ (281) $ 13 2019 5 5 2 297 (298) 11 Depreciation and amortization: 2020 $ 282 $ 143 $ 134 $ 26 $ — $ 585 2019 281 138 114 29 — 562 Operating expenses: 2020 $ 1,364 $ 843 $ 847 $ 284 $ (281) $ 3,057 2019 1,444 820 838 302 (298) 3,106 Interest expense, net: 2020 $ 103 $ 47 $ 45 $ 6 $ — $ 201 2019 100 45 44 8 — 197 Income (loss) before income taxes: 2020 $ 211 $ 71 $ 67 $ (9) $ — $ 340 2019 (d) 226 132 89 (11) — 436 Income Taxes: 2020 $ (16) $ (20) $ (39) $ (2) $ — $ (77) 2019 9 16 2 (2) — 25 Net income (loss): 2020 $ 227 $ 91 $ 106 $ (6) $ — $ 418 2019 217 116 87 (8) — 412 Capital Expenditures: 2020 $ 512 $ 278 $ 281 $ 1 $ — $ 1,072 2019 455 245 300 6 — 1,006 Total assets: September 30, 2020 $ 9,227 $ 4,992 $ 4,201 $ 5,239 $ (265) $ 23,394 December 31, 2019 (d) 8,661 4,830 3,933 5,335 (40) 22,719 __________ (a) Other primarily includes PHI’s corporate operations, shared service entities, and other financing and investment activities. (b) 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. (c) Includes intersegment revenues with ComEd, BGE, and PECO, which are eliminated at Exelon. (d) The Income (loss) before income taxes and Total assets amounts in Other and Intersegment Eliminations have been adjusted by an offsetting $422 million and $5.7 billion, respectively, for consistency with the Exelon consolidating disclosure above.
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): Nine Months Ended September 30, 2020 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 3,692 $ (152) $ 3,540 $ 21 $ 3,561 Midwest 2,773 240 3,013 (6) 3,007 New York 1,074 (12) 1,062 (1) 1,061 ERCOT 579 155 734 20 754 Other Power Regions 2,718 300 3,018 (34) 2,984 Total Competitive Businesses Electric Revenues 10,836 531 11,367 — 11,367 Competitive Businesses Natural Gas Revenues 881 467 1,348 — 1,348 Competitive Businesses Other Revenues (c) 268 289 557 — 557 Total Generation Consolidated Operating Revenues $ 11,985 $ 1,287 $ 13,272 $ — $ 13,272 Nine Months Ended September 30, 2019 Revenues from external customers (a) Intersegment Total Contracts with customers Other (b) Total Mid-Atlantic $ 3,798 $ 9 $ 3,807 $ 2 $ 3,809 Midwest 3,083 172 3,255 (31) 3,224 New York 1,195 16 1,211 — 1,211 ERCOT 594 198 792 13 805 Other Power Regions 2,849 451 3,300 (46) 3,254 Total Competitive Businesses Electric Revenues 11,519 846 12,365 (62) 12,303 Competitive Businesses Natural Gas Revenues 1,041 438 1,479 62 1,541 Competitive Businesses Other Revenues (c) 343 93 436 — 436 Total Generation Consolidated Operating Revenues $ 12,903 $ 1,377 $ 14,280 $ — $ 14,280 __________ (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 $238 million an d $64 million in 2020 and 2019, respectively, and elimination of intersegment revenues. Revenues net of purchased power and fuel expense (Generation): Nine Months Ended September 30, 2020 Nine Months Ended September 30, 2019 RNF from external customers (a) Intersegment Total RNF RNF from external customers (a) Intersegment Total RNF Mid-Atlantic $ 1,660 $ 23 $ 1,683 $ 2,007 $ 16 $ 2,023 Midwest 2,180 (2) 2,178 2,269 (22) 2,247 New York 714 11 725 800 10 810 ERCOT 311 14 325 252 (27) 225 Other Power Regions 608 (70) 538 542 (64) 478 Total Revenues net of purchased power and fuel expense for Reportable Segments 5,473 (24) 5,449 5,870 (87) 5,783 Other (b) 838 24 862 262 87 349 Total Generation Revenues net of purchased power and fuel expense $ 6,311 $ — $ 6,311 $ 6,132 $ — $ 6,132 __________ (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 $472 million and losses of $84 million in 2020 and 2019, respectively, accelerated nuclear fuel amortization associated with announced early pla nt retirements as discussed in Note 6 - Early Plant Retirements o f $24 million, which includes an impairment charge of $10 million , and $13 million decrease to revenue net of purchased power and fuel expense in 2020 and 2019, respectively, and the elimination of intersegment RNF.

Accounts Receivable (Tables)

Accounts Receivable (Tables)	9 Months Ended
	Sep. 30, 2020
Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]
Allowance for credit loss rollforward	The following tables present the rollforward of Allowance for Credit Losses on Customer Accounts Receivable. Three Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of June 30, 2020 $ 261 $ 33 $ 72 $ 71 $ 23 $ 62 $ 24 $ 18 $ 20 Plus: Current Period Provision for Expected Credit Losses (a) 114 1 37 27 14 35 11 7 17 Less: Write-offs, net of recoveries (b) 17 1 4 2 2 8 — 3 5 Balance as of September 30, 2020 $ 358 $ 33 $ 105 $ 96 $ 35 $ 89 $ 35 $ 22 $ 32 Nine Months Ended September 30, 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 (a) 222 13 62 56 28 63 24 14 25 Less: Write-offs, net of recoveries (b) 51 4 16 15 5 11 2 3 6 Less: Sale of customer accounts receivable (c) 56 56 — — — — — — — Balance as of September 30, 2020 $ 358 $ 33 $ 105 $ 96 $ 35 $ 89 $ 35 $ 22 $ 32 _________ (a) For the Utility Registrants, the increase is primarily as a result of increased aging of receivables, the temporary suspension of customer disconnections for non-payment, temporary cessation of new late payment fees, and reconnection of service to customers previously disconnected due to COVID-19. (b) Recoveries were not material to the Registrants. (c) See below for additional information on the sale of customer accounts receivable at Generation in the second quarter of 2020. The following tables present the rollforward of Allowance for Credit Losses on Other Accounts Receivable. Three Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Balance as of June 30, 2020 $ 61 $ — $ 22 $ 7 $ 6 $ 26 $ 11 $ 7 $ 8 Plus: Current Period Provision for Expected Credit Losses 15 — 5 1 3 6 2 1 3 Less: Write-offs, net of recoveries (a) 1 — — 1 — — — — — Balance as of September 30, 2020 $ 75 $ — $ 27 $ 7 $ 9 $ 32 $ 13 $ 8 $ 11 Nine Months Ended September 30, 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 36 — 9 3 7 17 6 4 7 Less: Write-offs, net of recoveries (a) 9 — 2 3 3 1 — — 1 Balance as of September 30, 2020 $ 75 $ — $ 27 $ 7 $ 9 $ 32 $ 13 $ 8 $ 11 _________ (a) Recoveries were not material to the 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 September 30, 2020 $ 672 $ 139 $ 193 $ 98 $ 115 $ 127 $ 72 $ 37 $ 18 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.
Purchases and sales of accounts receivable	The following table summarizes the impact of the sale of certain receivables: As of September 30, 2020 Derecognized receivables transferred at fair value (a) $ 1,232 Cash proceeds received 500 DPP 732 _________ (a) Includes additional customer accounts receivable sold into the Facility of $4,515 million since the start of the financing agreement. Three months ended September 30, 2020 Nine months ended September 30, 2020 Loss on sale of receivables (a) $ 8 $ 23 _________ (a) Reflected in Operating and maintenance expense on Exelon and Generation's Consolidated Statements of Operations and Comprehensive Income. Nine months ended September 30, 2020 Proceeds from new transfers $ 1,889 Cash collections received on DPP 2,518 Cash collections reinvested in the Facility 4,407 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. Nine Months Ended September 30, 2020 Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Total Receivables Purchased $ 2,698 $ — $ 865 $ 786 $ 508 $ 787 $ 484 $ 160 $ 143 Total Receivables Sold 542 790 — — — — — — — Related Party Transactions: Receivables purchased from Generation — — 34 67 75 72 51 13 8 Receivables sold to the Utility Registrants — 248 — — — — — — —

Early Plant Retirements (Tables

Early Plant Retirements (Tables)	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Restructuring and Related Costs [Table Text Block]	As a result of the decision to early retire Byron and Dresden, Exelon and Generation recognized certain one-time charges in the third quarter of 2020 related to materials and supplies inventory reserve adjustments, employee-related costs including severance benefit costs further discussed below, and construction work-in-progress impairments, among other items. In addition, as a result of the decisions to early retire Byron and Dresden, there are ongoing annual financial impacts stemming from shortening the expected economic useful lives of these nuclear plants primarily related to accelerated depreciation of plant assets (including any ARC), accelerated amortization of nuclear fuel, and changes in ARO accretion expense associated with the changes in decommissioning timing and cost assumptions to reflect an earlier retirement date. See Note 7 - Nuclear Decommissioning for additional information on changes to the nuclear decommissioning ARO balance and Note 8 — Asset Impairments for impairment assessment considerations given to the Midwest asset group as a result of the early retirement decision. The total impact on Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income is summarized in the table below. Income statement expense (pre-tax) Three and Nine Months Ended September 30, 2020 (a) Three Months Ended September 30, 2019 (b) Nine Months Ended September 30, 2019 (b) Depreciation and amortization Accelerated depreciation (c) $ 254 $ 71 $ 216 Accelerated nuclear fuel amortization 14 3 13 Operating and maintenance One-time charges 220 — — Other charges (d) 34 39 (44) Contractual offset (e) (129) — — Total $ 393 $ 113 $ 185 _________ (a) Reflects expense for Byron and Dresden. (b) Reflects expense for TMI. (c) Includes the accelerated depreciation of plant assets including any ARC. (d) For Dresden, reflects the net impacts associated with the remeasurement of the ARO. See Note 7 - Nuclear Decommissioning for additional information. For TMI, primarily reflects the net impacts associated with the remeasurement of the ARO. See Note 9 - Asset Retirement Obligations of the 2019 Form 10-K for additional information. (e) Reflects contractual offset for ARO accretion, ARC depreciation, and net impacts associated with the remeasurement of the ARO. For Byron and Dresden, based on the regulatory agreement with the ICC, decommissioning-related activities are offset within Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income. The offset results in an equal adjustment to the noncurrent payables to ComEd at Generation and an adjustment to the regulatory liabilities at ComEd. See Note 9 - Asset Retirement Obligations of the Exelon 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 September 30, 2020 for Exelon's and Generation's significant assets and liabilities associated with the Braidwood and LaSalle nuclear plants. Current depreciation provisions are based on the estimated useful lives of these nuclear generating stations, which reflect the first renewal of the operating licenses. Braidwood LaSalle Total Asset Balances Materials and supplies inventory, net $ 82 $ 107 $ 189 Nuclear fuel inventory, net 147 218 365 Completed plant, net 1,403 1,571 2,974 Construction work in progress 18 23 41 Liability Balances Asset retirement obligation (570) (926) (1,496) NRC License First Renewal Term 2046 (Unit 1) 2042 (Unit 1) 2047 (Unit 2) 2043 (Unit 2)

Nuclear Decommissioning (Tables

Nuclear Decommissioning (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2020: Nuclear decommissioning ARO at December 31, 2019 (a) $ 10,504 Accretion expense 367 Net increase due to changes in, and timing of, estimated future cash flows 806 Costs incurred related to decommissioning plants (59) Nuclear decommissioning ARO at September 30, 2020 (a) $ 11,618 _________ (a) Includes $93 million and $112 million as the current portion of the ARO at September 30, 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)	9 Months Ended
	Sep. 30, 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 September 30, 2020 (a) Exelon Generation ComEd PECO (b) BGE PHI (c) Pepco DPL ACE (c) 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 12.3 (10.3) 8.1 (6.2) 5.1 5.5 4.6 6.6 6.9 Qualified NDT fund income 13.2 47.4 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.4) (4.5) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (4.3) — (0.6) (23.3) (1.2) (1.5) (2.1) (0.4) (1.3) Production tax credits and other credits (3.0) (9.2) (0.4) — (0.8) (0.5) (0.5) (0.5) (0.4) Noncontrolling interests 0.8 2.9 — — — — — — — Excess deferred tax amortization (10.1) — (5.6) (3.8) (10.6) (24.9) (20.0) (23.6) (36.8) Tax settlements (0.2) (0.7) — — — — — — — Other (0.8) (0.9) 1.1 (0.8) (0.3) 0.1 (0.4) 0.7 0.6 Effective income tax rate 27.5% 45.7% 23.4% (13.1)% 13.1% (0.5)% 2.5% 3.6% (10.3)% Three Months Ended September 30, 2019 (a) Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 6.4 5.2 8.1 (0.3) 6.3 4.8 1.9 6.6 6.9 Qualified NDT fund income 3.2 7.1 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (4.1) (8.9) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (1.7) — (1.0) (7.5) (1.1) (1.8) (2.6) (0.6) (1.9) Production tax credits and other credits (1.2) (2.7) — — — — — — — Noncontrolling interests (2.2) (4.8) — — — — — — — Excess deferred tax amortization (6.5) — (9.9) (3.6) (8.0) (17.7) (16.3) (13.5) (23.3) Other 0.7 0.5 0.4 (0.5) (0.2) 0.8 1.0 (0.1) 0.7 Effective income tax rate 15.6% 17.4% 18.4% 9.1% 17.9% 6.9% 4.9% 13.2% 3.1% Nine Months Ended September 30, 2020 (a) Exelon Generation (d) ComEd (e) PECO (b) BGE (c) PHI (c) Pepco (c) DPL (c) ACE (c) 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 9.3 — 12.7 (3.4) 5.5 5.0 4.2 6.5 6.8 Qualified NDT fund income 3.2 10.0 — — — — — — — Deferred Prosecution Agreement payments 2.5 — 9.4 — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.2) (3.2) (0.3) — (0.1) (0.2) (0.1) (0.3) (0.5) Plant basis differences (4.0) — (0.9) (15.9) (1.8) (2.2) (2.4) (0.5) (3.7) Production tax credits and other credits (2.6) (7.0) (0.4) — (0.4) (0.3) (0.3) (0.2) (0.4) Noncontrolling interests 1.0 3.1 — — — — — — — Excess deferred tax amortization (15.8) — (11.8) (3.5) (15.0) (45.3) (29.2) (53.6) (81.4) Tax settlements (5.0) (15.7) — — — — — — — Other 0.1 (0.5) 2.1 (0.5) (0.5) (0.6) (0.8) (1.1) — Effective income tax rate 8.5% 7.7% 31.8% (2.3)% 8.7% (22.6)% (7.6)% (28.2)% (58.2)% Nine Months Ended September 30, 2019 (a) Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE U.S. Federal statutory rate 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% 21.0% Increase (decrease) due to: State income taxes, net of Federal income tax benefit 5.1 4.2 8.2 — 6.4 4.8 2.0 6.7 6.9 Qualified NDT fund income 5.3 11.9 — — — — — — — Amortization of investment tax credit, including deferred taxes on basis difference (1.9) (4.0) (0.2) — (0.1) (0.2) (0.1) (0.2) (0.3) Plant basis differences (1.6) — (0.7) (6.8) (1.1) (1.8) (2.3) (0.6) (2.0) Production tax credits and other credits (1.0) (2.1) — — — — — — — Noncontrolling interests (1.0) (2.3) — — — — — — — Excess deferred tax amortization (6.0) — (9.2) (2.9) (7.9) (18.6) (17.3) (15.0) (23.4) Other 0.8 (0.1) 0.2 (0.2) 0.1 0.5 0.7 0.2 — Effective income tax rate 20.7% 28.6% 19.3% 11.1% 18.4% 5.7% 4.0% 12.1% 2.2% __________ (a) Positive percentages represent income tax expense. Negative percentages represent income tax benefit. (b) At PECO, the lower effective tax rate is primarily related to an increase in plant basis differences attributable to storm repairs. (c) At BGE, PHI, Pepco, DPL, and ACE, the lower effective tax rate is primarily attributable to accelerated amortization of transmission related deferred income tax regulatory liabilities as a result of regulatory settlements. See Note 2 — Regulatory Matters for additional information. (d) At Generation, the lower effective tax rate is primarily attributable to tax settlements. (e) At ComEd, the higher effective tax rate is primarily related to the nondeductible Deferred Prosecution Agreement payments. See Note 14 — Commitments and Contingencies for additional information.
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	Exelon, Generation, PHI, and ACE have the following unrecognized tax benefits as of September 30, 2020 and December 31, 2019. ComEd, PECO, BGE, Pepco, and DPL's amounts are not material. Exelon Generation PHI ACE September 30, 2020 $ 125 $ 49 $ 53 $ 16 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 September 30, 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.
Allocation of Tax Benefits	The following table presents the allocation of federal tax benefits from Exelon under the Tax Sharing Agreement. Generation ComEd PECO BGE PHI Pepco DPL ACE September 30, 2020 $ 64 $ 14 $ 17 $ — $ 17 $ 8 $ 6 $ 1 December 31, 2019 41 — 14 3 7 6 1 —

Retirement Benefits (Tables)

Retirement Benefits (Tables)	9 Months Ended
	Sep. 30, 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 and nine months ended September 30, 2020 and 2019. Pension Benefits OPEB Three Months Ended September 30, Three Months Ended September 30, 2020 2019 2020 2019 Components of net periodic benefit cost: Service cost $ 97 $ 89 $ 22 $ 23 Interest cost 190 221 37 47 Expected return on assets (317) (306) (41) (38) Amortization of: Prior service cost (benefit) 1 — (30) (45) Actuarial loss 128 104 12 11 Settlement charges 8 7 — — Contractual termination benefits — 1 — — Net periodic benefit cost $ 107 $ 116 $ — $ (2) Pension Benefits OPEB Nine Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Components of net periodic benefit cost: Service cost $ 290 $ 267 $ 67 $ 70 Interest cost 569 663 114 141 Expected return on assets (953) (918) (122) (115) Amortization of: Prior service cost (benefit) 3 — (92) (134) Actuarial loss 384 310 36 34 Settlement charges 14 7 — — Contractual termination benefits — 1 — — Net periodic benefit cost $ 307 $ 330 $ 3 $ (4)
Allocated Portion of Pension and Postretirement Benefit Costs	The amounts below represent the Registrants' allocated pension and OPEB plan costs. For Exelon, the service cost component is included in Operating and maintenance expense and Property, plant, and equipment, net while the non-service cost components are included in Other, net and Regulatory assets. For Generation and the Utility Registrants, the service cost and non-service cost components are included in Operating and maintenance expense and Property, plant, and equipment, net in their consolidated financial statements. Three Months Ended September 30, Nine Months Ended September 30, Pension and OPEB Costs 2020 2019 2020 2019 Exelon $ 107 $ 114 $ 310 $ 326 Generation 30 37 89 100 ComEd 29 23 85 70 PECO 1 4 4 9 BGE 16 16 47 47 PHI 17 23 52 71 Pepco 4 6 11 19 DPL 2 4 6 11 ACE 3 4 10 12
Defined Contribution Savings Plans	The Registrants participate in various 401(k) defined contribution savings plans that are sponsored by Exelon. The plans are qualified under applicable sections of the IRC and allow employees to contribute a portion of their pre-tax and/or after-tax income in accordance with specified guidelines. All Registrants match a percentage of the employee contributions up to certain limits. The following table presents the matching contributions to the savings plans during the three and nine months ended September 30, 2020 and 2019, respectively. Three Months Ended September 30, Nine Months Ended September 30, Savings Plan Matching Contributions 2020 2019 2020 2019 Exelon $ 37 $ 36 $ 104 $ 101 Generation 14 14 41 41 ComEd 9 9 25 26 PECO 3 2 8 7 BGE 4 4 8 9 PHI 3 4 9 8 Pepco 1 1 3 2 DPL 1 1 2 2 ACE — 1 1 1

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2020 and December 31, 2019: September 30, 2020 Exelon Generation ComEd Derivatives Total Economic Proprietary Collateral (a)(b) Netting (a) Subtotal Economic Mark-to-market derivative assets $ 471 $ 2,566 $ 58 $ 79 $ (2,232) $ 471 $ — Mark-to-market derivative assets 383 1,500 16 39 (1,172) 383 — Total mark-to-market derivative assets 854 4,066 74 118 (3,404) 854 — Mark-to-market derivative liabilities (168) (2,414) (40) 84 2,232 (138) (30) Mark-to-market derivative liabilities (378) (1,313) (12) 49 1,172 (104) (274) Total mark-to-market derivative liabilities (546) (3,727) (52) 133 3,404 (242) (304) Total mark-to-market derivative net assets (liabilities) $ 308 $ 339 $ 22 $ 251 $ — $ 612 $ (304) December 31, 2019 Exelon Generation ComEd Description Total Economic Proprietary Collateral (a)(b) 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 not material and not reflected in the table above. (b) Of the collateral posted/(received), $34 million and $511 million represents variation margin on the exchanges at September 30, 2020 and December 31, 2019 respectively.
Economic Hedges (Commodity Price Risk)	For the three and nine months ended September 30, 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 Nine Months Ended 2020 2019 2020 2019 Income Statement Location Gain (Loss) Gain (Loss) Operating revenues $ 39 $ 76 $ 238 $ 65 Purchased power and fuel 209 (45) 224 (127) Total Exelon and Generation $ 248 $ 31 $ 462 $ (62)
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 September 30, 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 September 30, 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 $ 638 $ 27 $ 611 — $ — Non-investment grade 4 — 4 No external ratings Internally rated — investment grade 168 1 167 Internally rated — non-investment grade 110 29 81 Total $ 920 $ 57 $ 863 — $ — Net Credit Exposure by Type of Counterparty As of September 30, 2020 Financial institutions $ 26 Investor-owned utilities, marketers, power producers 650 Energy cooperatives and municipalities 142 Other 45 Total $ 863 _________ (a) As of September 30, 2020, credit collateral held from counterparties where Generation had credit exposure included $31 million of cash and $26 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]	The aggregate fair value of all derivative instruments with credit-risk related contingent features in a liability position that are not fully collateralized (excluding transactions on the exchanges that are fully collateralized) is detailed in the table below: Credit-Risk Related Contingent Features September 30, 2020 December 31, 2019 Gross fair value of derivative contracts containing this feature (a) $ (750) $ (956) Offsetting fair value of in-the-money contracts under master netting arrangements (b) 535 649 Net fair value of derivative contracts containing this feature (c) $ (215) $ (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 September 30, 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. September 30, 2020 December 31, 2019 Cash collateral posted $ 288 $ 982 Letters of credit posted 212 264 Cash collateral held 68 103 Letters of credit held 74 112 Additional collateral required in the event of a credit downgrade below investment grade 1,287 1,509

Debt and Credit Agreements (Tab

Debt and Credit Agreements (Tables)	9 Months Ended
	Sep. 30, 2020
Line of Credit Facility [Line Items]
Schedule of Long-term Debt Instruments [Table Text Block]	During the nine months ended September 30, 2020, the following long-term debt was issued: Company Type Interest Rate Maturity Amount Use of Proceeds Exelon Notes 4.05 % April 15, 2030 $ 1,250 Repay existing indebtedness and for general corporate purposes. Exelon Notes 4.70 % April 15, 2050 750 Repay existing indebtedness and for general corporate purposes. Generation Senior Notes 3.25 % June 1, 2025 900 Repay existing indebtedness and for general corporate purposes. Generation Energy Efficiency Project Financing (a) 3.95 % December 31, 2020 3 Funding to install energy conservation measures for the Fort Meade project. Generation Energy Efficiency Project Financing (a) 2.53 % April 30, 2021 2 Funding to install energy conservation measures for the Fort AP Hill project. 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. 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. PECO First and Refunding Mortgage Bonds 2.80 % June 15, 2050 350 Funding for general corporate purposes. BGE Senior Notes 2.90 % June 15, 2050 400 Repay commercial paper obligations and for general corporate purposes. Pepco First Mortgage Bonds 2.53 % February 25, 2030 150 Repay existing indebtedness and for general corporate purposes. Pepco First Mortgage Bonds 3.28 % September 23, 2050 150 Repay existing indebtedness and for general corporate purposes. DPL First Mortgage Bonds 2.53 % June 9, 2030 100 Repay existing indebtedness and for general corporate purposes. DPL (b) Tax-Exempt Bonds 1.05 % January 1, 2031 78 Refinance existing indebtedness. ACE Tax-Exempt First Mortgage Bonds 2.25 % June 1, 2029 23 Refinance existing indebtedness. ACE First Mortgage Bonds 3.24 % June 9, 2050 100 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) The bonds have a 1.05% interest rate through July 2025.
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 September 30, 2020 and December 31, 2019. PECO had no commercial paper borrowings as of both September 30, 2020 and December 31, 2019. Outstanding Commercial Average Interest Rate on Commercial Paper Issuer September 30, 2020 December 31, 2019 September 30, 2020 December 31, 2019 Exelon (a) $ 141 $ 870 0.16 % 2.25 % Generation — 320 — % 1.84 % ComEd 141 130 0.16 % 2.38 % BGE — 76 — % 2.46 % PHI (b) — 208 — % N/A PEPCO — 82 — % 2.56 % DPL — 56 — % 2.02 % ACE — 70 — % 2.43 % __________ (a) Includes outstanding commercial paper at Exelon Corporate of $136 million with average interest rates on commercial paper borrowings of 1.92% at December 31, 2019. Exelon Corporate had no outstanding commercial paper borrowings as of September 30, 2020. (b) Includes the consolidated amounts of Pepco, DPL, and ACE.

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 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. September 30, 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 $ 37,589 $ 40,816 $ 3,237 $ 44,053 $ 36,039 $ 37,453 $ 2,580 $ 40,033 Generation 6,756 6,250 1,401 7,651 7,974 7,304 1,366 8,670 ComEd 8,981 10,970 — 10,970 8,491 9,848 — 9,848 PECO 3,753 4,498 50 4,548 3,405 3,868 50 3,918 BGE 3,664 4,263 — 4,263 3,270 3,649 — 3,649 PHI 7,020 6,082 1,786 7,868 6,563 5,902 1,164 7,066 Pepco 3,164 3,343 739 4,082 2,864 3,198 388 3,586 DPL 1,676 1,463 449 1,912 1,567 1,408 311 1,719 ACE 1,417 1,017 598 1,615 1,327 1,026 464 1,490 Long-Term Debt to Financing Trusts (a) Exelon $ 390 $ — $ 467 $ 467 $ 390 $ — $ 428 $ 428 ComEd 205 — 246 246 205 — 227 227 PECO 184 — 221 221 184 — 201 201 SNF Obligation Exelon $ 1,207 $ 1,042 $ — $ 1,042 $ 1,199 $ 1,055 $ — $ 1,055 Generation 1,207 1,042 — 1,042 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 September 30, 2020 and December 31, 2019: Exelon and Generation Exelon Generation As of September 30, 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) $ 1,687 $ — $ — $ — $ 1,687 $ 270 $ — $ — $ — $ 270 NDT fund investments Cash equivalents (b) 313 91 — — 404 313 91 — — 404 Equities 3,345 1,794 — 1,370 6,509 3,345 1,794 — 1,370 6,509 Fixed income Corporate debt — 1,516 280 — 1,796 — 1,516 280 — 1,796 U.S. Treasury and agencies 1,843 137 — — 1,980 1,843 137 — — 1,980 Foreign governments — 52 — — 52 — 52 — — 52 State and municipal debt — 104 — — 104 — 104 — — 104 Other — 40 — 1,010 1,050 — 40 — 1,010 1,050 Fixed income subtotal 1,843 1,849 280 1,010 4,982 1,843 1,849 280 1,010 4,982 Private credit — — 238 533 771 — — 238 533 771 Private equity — — — 439 439 — — — 439 439 Real estate — — — 650 650 — — — 650 650 NDT fund investments subtotal (c)(d) 5,501 3,734 518 4,002 13,755 5,501 3,734 518 4,002 13,755 Rabbi trust investments Cash equivalents 58 — — — 58 4 — — — 4 Mutual funds 88 — — — 88 28 — — — 28 Fixed income — 11 — — 11 — — — — — Life insurance contracts — 84 34 — 118 — 27 — — 27 Rabbi trust investments subtotal 146 95 34 — 275 32 27 — — 59 Commodity derivative assets Economic hedges 776 1,737 1,553 — 4,066 776 1,737 1,553 — 4,066 Proprietary trading — 37 37 — 74 — 37 37 — 74 Effect of netting and allocation of collateral (e)(f) (656) (1,594) (1,036) — (3,286) (656) (1,594) (1,036) — (3,286) Commodity derivative assets subtotal 120 180 554 — 854 120 180 554 — 854 DPP consideration — 732 — — 732 — 732 — — 732 Total assets 7,454 4,741 1,106 4,002 17,303 5,923 4,673 1,072 4,002 15,670 Exelon Generation As of September 30, 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 (700) (1,692) (1,639) — (4,031) (700) (1,692) (1,335) — (3,727) Proprietary trading — (36) (16) — (52) — (36) (16) — (52) Effect of netting and allocation of collateral (e)(f) 699 1,708 1,130 — 3,537 699 1,708 1,130 — 3,537 Commodity derivative liabilities subtotal (1) (20) (525) — (546) (1) (20) (221) — (242) Deferred compensation obligation — (135) — — (135) — (37) — — (37) Total liabilities (1) (155) (525) — (681) (1) (57) (221) — (279) Total net assets $ 7,453 $ 4,586 $ 581 $ 4,002 $ 16,622 $ 5,922 $ 4,616 $ 851 $ 4,002 $ 15,391 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 — 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 (c)(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 $677 million and $373 million at September 30, 2020 and December 31, 2019, respectively, and restricted cash of $116 million and $110 million at September 30, 2020 and December 31, 2019, respectively, and includes long-term restricted cash of $137 million and $177 million at September 30, 2020 and December 31, 2019, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Generation excludes cash of $408 million and $177 million at September 30, 2020 and December 31, 2019, respectively, and restricted cash of $45 million and $58 million at September 30, 2020 and December 31, 2019, respectively. (b) Includes $121 million and $90 million of cash received from outstanding repurchase agreements at September 30, 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 derivative assets of less than $1 million and $2 million, which have total notional amounts of $658 million and $724 million at September 30, 2020 and December 31, 2019, respectively. The notional principal amounts for these instruments provide one measure of the transaction volume outstanding as of the periods ended and do not represent the amount of Exelon and Generation's exposure to credit or market loss. (d) Excludes net liabilities of $208 million and $147 million at September 30, 2020 and December 31, 2019, respectively, which include certain derivative assets that have notional amounts of $153 million and $99 million at September 30, 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, net of collateral paid to counterparties, totaled $43 million, $114 million, and $94 million allocated to Level 1, Level 2, and Level 3 mark-to-market derivatives, respectively, as of September 30, 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), $34 million and $511 million represents variation margin on the exchanges as of September 30, 2020 and December 31, 2019, respectively. As of September 30, 2020, Exelon and Generation have outstanding commitments to invest in fixed income, private credit, private equity and real estate investments of approximately $52 million, $119 million, $299 million, and $395 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 September 30, 2020, respectively. Changes in fair value, cumulative adjustments, and impairments were not material for the three and nine months ended September 30, 2020. ComEd, PECO and BGE ComEd PECO BGE As of September 30, 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) $ 396 $ — $ — $ 396 $ 184 $ — $ — $ 184 $ 298 $ — $ — $ 298 Rabbi trust investments Mutual funds — — — — 9 — — 9 9 — — 9 Life insurance contracts — — — — — 13 — 13 — — — — Rabbi trust investments subtotal — — — — 9 13 — 22 9 — — 9 Total assets 396 — — 396 193 13 — 206 307 — — 307 Liabilities Deferred compensation obligation — (7) — (7) — (8) — (8) — (5) — (5) Mark-to-market derivative liabilities (b) — — (304) (304) — — — — — — — — Total liabilities — (7) (304) (311) — (8) — (8) — (5) — (5) Total net assets (liabilities) $ 396 $ (7) $ (304) $ 85 $ 193 $ 5 $ — $ 198 $ 307 $ (5) $ — $ 302 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 $76 million and $90 million at September 30, 2020 and December 31, 2019, respectively, and restricted cash of $36 million and $33 million at September 30, 2020 and December 31, 2019, respectively, and includes long-term restricted cash of $127 million and $163 million at September 30, 2020 and December 31, 2019, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. PECO excludes cash of $65 million and $12 million at September 30, 2020 and December 31, 2019, respectively. BGE excludes cash of $28 million and $24 million at September 30, 2020 and December 31, 2019, respectively, and restricted cash of $1 million at both September 30, 2020 and December 31, 2019. (b) The Level 3 balance consists of the current and noncurrent liability of $30 million and $274 million, respectively, at September 30, 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 September 30, 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) $ 166 $ — $ — $ 166 $ 124 $ — $ — $ 124 Rabbi trust investments Cash equivalents 52 — — 52 44 — — 44 Mutual funds 14 — — 14 14 — — 14 Fixed income — 11 — 11 — 12 — 12 Life insurance contracts — 26 34 60 — 24 41 65 Rabbi trust investments subtotal 66 37 34 137 58 36 41 135 Total assets 232 37 34 303 182 36 41 259 Liabilities Deferred compensation obligation — (17) — (17) — (19) — (19) Total liabilities — (17) — (17) — (19) — (19) Total net assets $ 232 $ 20 $ 34 $ 286 $ 182 $ 17 $ 41 $ 240 Pepco DPL ACE As of September 30, 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) $ 112 $ — $ — $ 112 $ 17 $ — $ — $ 17 $ 14 $ — $ — $ 14 Rabbi trust investments Cash equivalents 51 — — 51 — — — — — — — — Fixed income — 2 — 2 — — — — — — — — Life insurance contracts — 26 34 60 — — — — — — — — Rabbi trust investments subtotal 51 28 34 113 — — — — — — — — Total assets 163 28 34 225 17 — — 17 14 — — 14 Liabilities Deferred compensation obligation — (2) — (2) — — — — — — — — Total liabilities — (2) — (2) — — — — — — — — Total net assets $ 163 $ 26 $ 34 $ 223 $ 17 $ — $ — $ 17 $ 14 $ — $ — $ 14 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 $78 million and $57 million at September 30, 2020 and December 31, 2019, respectively, and includes long-term restricted cash of $10 million and $14 million at September 30, 2020 and December 31, 2019, respectively, which is reported in Other deferred debits in the Consolidated Balance Sheets. Pepco excludes cash of $46 million and $29 million at September 30, 2020 and December 31, 2019, respectively. DPL excludes cash of $9 million and $13 million at September 30, 2020 and December 31, 2019, respectively. ACE excludes cash of $13 million and $12 million at September 30, 2020 and December 31, 2019, respectively, and includes long-term restricted cash of $10 million and $14 million at September 30, 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	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 and nine months ended September 30, 2020 and 2019: Exelon Generation ComEd PHI and Pepco Three Months Ended September 30, 2020 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of June 30, 2020 $ 883 $ 499 $ 659 $ 1,158 $ (318) $ 43 $ — Total realized / unrealized gains (losses) Included in net income (327) 3 (318) (a) (315) — (12) — Included in noncurrent payables to affiliates — 18 — 18 — — (18) Included in regulatory assets/liabilities 32 — — — 14 (b) — 18 Change in collateral (79) — (79) (79) — — — Purchases, sales, issuances and settlements Purchases 66 1 65 66 — — — Sales (3) — (3) (3) — — — Settlements — (3) — (3) — 3 — Transfers out of Level 3 9 — 9 (c) 9 — — — Balance at September 30, 2020 $ 581 $ 518 $ 333 $ 851 $ (304) $ 34 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2020 $ (222) $ 3 $ (213) $ (210) $ — $ (12) $ — Exelon Generation ComEd PHI and Pepco Nine months ended September 30, 2020 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market 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 (483) 1 (474) (a) (473) — (10) — Included in noncurrent payables to affiliates — 17 — 17 — — (17) Included in regulatory assets 14 — — — (3) (b) — 17 Change in collateral (120) — (120) (120) — — — Purchases, sales, issuances and settlements Purchases 136 6 130 136 — — — Sales (27) — (27) (27) — — — Settlements (15) (18) — (18) — 3 — Transfers into Level 3 (5) 1 (6) (c) (5) — — — Transfers out of Level 3 13 — 13 (c) 13 — — — Balance as of September 30, 2020 $ 581 $ 518 $ 333 $ 851 $ (304) $ 34 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2020 $ (107) $ 1 $ (98) $ (97) $ — $ (10) $ — Exelon Generation ComEd PHI and Pepco Three Months Ended September 30, 2019 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of June 30, 2019 $ 1,179 $ 539 $ 873 $ 1,412 $ (273) $ 40 $ — Total realized / unrealized gains (losses) Included in net income (171) 2 (173) (a) (171) — — — Included in noncurrent payables to affiliates — 11 — 11 — — (11) Included in regulatory assets 4 — — — (7) (b) — 11 Change in collateral 41 — 41 41 — — — Purchases, sales, issuances and settlements Purchases 53 1 52 53 — — — Sales (22) (21) (1) (22) — — — Settlements (18) (18) — (18) — — — Transfers into Level 3 1 — 1 (c) 1 — — — Transfers out of Level 3 (11) — (11) (c) (11) — — — Balance as of September 30, 2019 $ 1,056 $ 514 $ 782 $ 1,296 $ (280) $ 40 $ — The amount of total (losses) gains included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2019 $ (18) $ 2 $ (20) $ (18) $ — $ — $ — Exelon Generation ComEd PHI and Pepco Nine Months Ended September 30, 2019 Total NDT Fund Mark-to-Market Total Generation Mark-to-Market Life Insurance Contracts Eliminated in Consolidation Balance as of December 31, 2018 $ 907 $ 543 $ 575 $ 1,118 $ (249) $ 38 $ — Total realized / unrealized gains (losses) Included in net income (125) 5 (132) (a) (127) — 2 — Included in noncurrent payables to affiliates — 32 — 32 — — (32) Included in regulatory assets 1 — — — (31) (b) — 32 Change in collateral 227 — 227 227 — — — Purchases, sales, issuances and settlements Purchases 163 43 120 163 — — — Sales (23) (21) (2) (23) — — — Settlements (88) (88) — (88) — — — Transfers into Level 3 5 — 5 (c) 5 — — — Transfers out of Level 3 (11) — (11) (c) (11) — — — Balance as of September 30, 2019 $ 1,056 $ 514 $ 782 $ 1,296 $ (280) $ 40 $ — The amount of total gains (losses) included in income attributed to the change in unrealized gains (losses) related to assets and liabilities as of September 30, 2019 $ 173 $ 5 $ 166 $ 171 $ — $ 2 $ — __________ (a) Includes a reduction for the reclassification of $105 million and $376 million of realized losses due to the settlement of derivative contracts for the three and nine months ended September 30, 2020. Includes a reduction for the reclassification of $153 million and $298 million of realized losses due to the settlement of derivative contracts for the three and nine months ended September 30, 2019. (b) Includes 1) an increase in fair value of $9 million for the three months ended September 30, 2020 and a decrease in fair value of $7 million, $26 million, and $31 million for the three months ended September 30, 2019, nine months ended September 30, 2020, and nine months ended September 30, 2019, respectively, and 2) an increase in realized losses recorded in purchased power expense due to settlements associated with floating-to-fixed energy swap contracts with unaffiliated suppliers of $5 million, $4 million, $23 million, and $17 million for the three months ended September 30, 2020, three months ended September 30, 2019, nine months ended September 30, 2020, and nine months ended September 30, 2019, respectively. (c) Transfers into and out of Level 3 generally occur when the contract tenor becomes less and more observable respectively, primarily due to changes in market liquidity or assumptions for certain commodity contracts.
Total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis	The following tables present the income statement classification of the total realized and unrealized gains (losses) included in income for Level 3 assets and liabilities measured at fair value on a recurring basis during the three and nine months ended September 30, 2020 and 2019: Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total realized losses for the three months ended September 30, 2020 $ (305) $ (13) $ (12) $ — $ (305) $ (13) $ — $ (12) Total realized losses for the nine months ended September 30, 2020 (370) (104) (10) — (370) (104) — (10) Total unrealized (losses) gains for the three months ended September 30, 2020 (216) 3 (12) 3 (216) 3 3 (12) Total unrealized (losses) gains for the nine months ended September 30, 2020 (50) (48) (10) 1 (50) (48) 1 (10) Exelon Generation PHI and Pepco Operating Purchased Operating and Maintenance Other, net Operating Purchased Other, net Operating and Maintenance Total realized (losses) gains for the three months ended September 30, 2019 $ (25) $ (148) $ — $ 2 $ (25) $ (148) $ 2 $ — Total realized gains (losses) for the nine months ended September 30, 2019 122 (254) — 5 122 (254) 5 — Total unrealized gains (losses) for the three months ended September 30, 2019 99 (119) — 2 99 (119) 2 — Total unrealized gains (losses) gains for the nine months ended September 30, 2019 368 (202) 2 5 368 (202) 5 2
Fair value reconciliation of Level 3 assets and liabilities measured at fair value on a recurring basis, valuation technique	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 September 30, 2020 Fair Value at December 31, 2019 Valuation Unobservable 2020 Range & Arithmetic Average 2019 Range & Arithmetic Average Mark-to-market derivatives — Economic Hedges (Exelon and Generation) (a)(b) $ 218 $ 558 Discounted Forward power $9 - $113 $29 $9 - $180 $29 Forward gas $1.84 - $4.69 $2.77 $0.83 - $10.72 $2.55 Option Volatility 10% - 160% 57% 8% - 236% 70% Mark-to-market derivatives — Proprietary trading (Exelon and Generation) (a)(b) $ 21 $ 45 Discounted Forward power $9 - $115 $31 $25 - $180 $33 Mark-to-market derivatives (Exelon and ComEd) $ (304) $ (301) Discounted Forward heat (c) 8x - 9x 8.85x 9x - 10x 9.68x Marketability 3% - 8% 4.93% 3% - 7% 4.95% Renewable 91% - 123% 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 $94 million and $214 million as of September 30, 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)	9 Months Ended
	Sep. 30, 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 September 30, 2020: Description Exelon PHI Pepco DPL ACE Total commitments $ 513 $ 320 $ 120 $ 89 $ 111 Remaining commitments (a) 87 69 57 7 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 September 30, 2020, representing commitments potentially triggered by future events were as follows: Expiration within Total 2020 2021 2022 2023 2024 2025 and beyond Exelon Letters of credit $ 1,462 $ 224 $ 1,238 $ — $ — $ — $ — Surety bonds (a) 1,056 388 641 27 — — — Financing trust guarantees 378 — — — — — 378 Guaranteed lease residual values (b) 28 — 2 3 3 6 14 Total commercial commitments $ 2,924 $ 612 $ 1,881 $ 30 $ 3 $ 6 $ 392 Generation Letters of credit $ 1,447 $ 220 $ 1,227 $ — $ — $ — $ — Surety bonds (a) 912 374 511 27 — — — Total commercial commitments $ 2,359 $ 594 $ 1,738 $ 27 $ — $ — $ — ComEd Letters of credit $ 7 $ — $ 7 $ — $ — $ — $ — Surety bonds (a) 16 5 11 — — — — Financing trust guarantees 200 — — — — — 200 Total commercial commitments $ 223 $ 5 $ 18 $ — $ — $ — $ 200 PECO Surety bonds (a) $ 2 $ — $ 2 $ — $ — $ — $ — Financing trust guarantees 178 — — — — — 178 Total commercial commitments $ 180 $ — $ 2 $ — $ — $ — $ 178 BGE Letters of credit $ 2 $ 2 $ — $ — $ — $ — $ — Surety bonds (a) 3 1 2 — — — — Total commercial commitments $ 5 $ 3 $ 2 $ — $ — $ — $ — PHI Surety bonds (a) $ 21 $ 3 $ 18 $ — $ — $ — $ — Guaranteed lease residual values (b) 28 — 2 3 3 6 14 Total commercial commitments $ 49 $ 3 $ 20 $ 3 $ 3 $ 6 $ 14 Pepco Surety bonds (a) $ 14 $ — $ 14 $ — $ — $ — $ — Guaranteed lease residual values (b) 9 — — 1 1 2 5 Total commercial commitments $ 23 $ — $ 14 $ 1 $ 1 $ 2 $ 5 DPL Surety bonds (a) $ 4 $ 2 $ 2 $ — $ — $ — $ — Guaranteed lease residual values (b) 12 — 1 1 1 3 6 Total commercial commitments $ 16 $ 2 $ 3 $ 1 $ 1 $ 3 $ 6 ACE Surety bonds (a) $ 3 $ 1 $ 2 $ — $ — $ — $ — Guaranteed lease residual values (b) 7 — 1 1 1 1 3 Total commercial commitments $ 10 $ 1 $ 3 $ 1 $ 1 $ 1 $ 3 __________ (a) Surety bonds—Guarantees issued related to contract and commercial agreements, excluding bid bonds. (b) Represents the maximum potential obligation in the event that the fair value of certain leased equipment and fleet vehicles is zero at the end of the maximum lease term. The lease term associated with these assets ranges from 1 to 8 years . The maximum potential obligation at the end of the minimum lease term would be $74 million guaranteed by Exelon and PHI, of which $25 million , $31 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 September 30, 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: September 30, 2020 December 31, 2019 Total environmental Portion of total related to Total environmental Portion of total related to Exelon $ 494 $ 320 $ 478 $ 320 Generation 125 — 105 — ComEd 299 298 304 303 PECO 23 22 19 17 BGE 2 — 2 — PHI 45 — 48 — Pepco 43 — 46 — DPL 1 — 1 — ACE 1 — 1 —

Changes in Accumulated Other _2

Changes in Accumulated Other Comprehensive Income (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2020 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Total Beginning balance $ (3) $ (3,096) $ (33) $ (3,132) OCI before reclassifications (1) (13) 3 (11) Amounts reclassified from AOCI — 39 — 39 Net current-period OCI (1) 26 3 28 Ending balance $ (4) $ (3,070) $ (30) $ (3,104) Three Months Ended September 30, 2019 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign AOCI of Investments in Unconsolidated Affiliates (b) Total Beginning balance $ (2) $ (2,957) $ (29) $ (2) $ (2,990) OCI before reclassifications — 6 (2) — 4 Amounts reclassified from AOCI — 21 — 2 23 Net current-period OCI — 27 (2) 2 27 Ending balance $ (2) $ (2,930) $ (31) $ — $ (2,963) Nine Months Ended September 30, 2020 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign Total Beginning balance $ (2) $ (3,165) $ (27) $ (3,194) OCI before reclassifications (2) (17) (3) (22) Amounts reclassified from AOCI — 112 — 112 Net current-period OCI (2) 95 (3) 90 Ending balance $ (4) $ (3,070) $ (30) $ (3,104) Nine Months Ended September 30, 2019 Losses on Cash Flow Hedges Pension and Non-Pension Postretirement Benefit Plan Items (a) Foreign AOCI of Investments in Unconsolidated Affiliates (b) Total Beginning balance $ (2) $ (2,960) $ (33) $ — $ (2,995) OCI before reclassifications — (32) 2 (2) (32) Amounts reclassified from AOCI — 62 — 2 64 Net current-period OCI — 30 2 — 32 Ending balance $ (2) $ (2,930) $ (31) $ — $ (2,963) _________ (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.
Schedule Of Other Comprehensive Income (Loss) Tax	The following table presents income tax benefit (expense) allocated to each component of Exelon's other comprehensive income (loss): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Pension and non-pension postretirement benefit plans: Prior service benefit reclassified to periodic benefit cost $ 4 $ 6 $ 12 $ 18 Actuarial loss reclassified to periodic benefit cost (16) (13) (50) (39) Pension and non-pension postretirement benefit plans valuation adjustment 3 — 6 14

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
	Sep. 30, 2020
Variable Interest Entity [Abstract]
VIE - Assets and Liabilities of VIEs which Creditors or Beneficiaries have no Recourse	Consolidated VIEs The table below shows the carrying amounts and classification of the consolidated VIEs’ assets and liabilities included in the consolidated financial statements of Exelon, Generation, PHI, and ACE as of September 30, 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. September 30, 2020 December 31, 2019 Exelon Generation PHI (a) ACE Exelon Generation PHI (a) ACE Cash and cash equivalents $ 148 $ 148 $ — $ — $ 163 $ 163 $ — $ — Restricted cash and cash equivalents 52 48 4 4 88 85 3 3 Accounts receivable Customer 151 151 — — 151 151 — — Other 39 39 — — 39 39 — — Unamortized energy contract assets 22 22 — — 23 23 — — Inventories, net Materials and supplies 241 241 — — 227 227 — — Other current assets 781 776 5 — 32 31 1 — Total current assets 1,434 1,425 9 4 723 719 4 3 Property, plant, and equipment, net 5,865 5,865 — — 6,022 6,022 — — Nuclear decommissioning trust funds 2,785 2,785 — — 2,741 2,741 — — Unamortized energy contract assets 253 253 — — 250 250 — — Other noncurrent assets 49 38 11 10 89 73 16 14 Total noncurrent assets 8,952 8,941 11 10 9,102 9,086 16 14 Total assets (b) $ 10,386 $ 10,366 $ 20 $ 14 $ 9,825 $ 9,805 $ 20 $ 17 Long-term debt due within one year $ 134 $ 109 $ 25 $ 20 $ 544 $ 523 $ 21 $ 20 Accounts payable 81 81 — — 106 106 — — Accrued expenses 63 63 — — 70 70 — — Unamortized energy contract liabilities 5 5 — — 8 8 — — Other current liabilities 26 26 — — 3 3 — — Total current liabilities 309 284 25 20 731 710 21 20 Long-term debt 913 906 7 6 527 504 23 21 Asset retirement obligations 2,210 2,210 — — 2,128 2,128 — — Unamortized energy contract liabilities 1 1 — — 1 1 — — Other noncurrent liabilities 106 106 — — 89 89 — — Total noncurrent liabilities 3,230 3,223 7 6 2,745 2,722 23 21 Total liabilities (c) $ 3,539 $ 3,507 $ 32 $ 26 $ 3,476 $ 3,432 $ 44 $ 41 _________ (a) Includes certain purchase accounting adjustments not pushed down to the ACE standalone entity. (b) Exelon’s and Generation’s balances include unrestricted assets for current unamortized energy contract assets of $22 million and $23 million, Property, plant, and equipment of $1 million and $20 million, non-current unamortized energy contract assets of $253 million and $250 million, and other unrestricted assets of $8 million and $0 million as of September 30, 2020 and December 31, 2019, respectively (c) Exelon’s and Generation’s balances include liabilities with recourse of $8 million and $3 million as of September 30, 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: September 30, 2020 December 31, 2019 Commercial Equity Total Commercial Equity Total Total assets (a) $ 736 $ 409 $ 1,145 $ 636 $ 443 $ 1,079 Total liabilities (a) 216 225 441 33 227 260 Exelon's ownership interest in VIE (a) — 163 163 — 191 191 Other ownership interests in VIE (a) 520 21 541 604 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 September 30, 2020 and December 31, 2019.

Supplemental Financial Inform_2

Supplemental Financial Information (Tables)	9 Months Ended
	Sep. 30, 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 PHI DPL Three Months Ended September 30, 2020 Operating lease income $ 30 $ 28 $ 1 $ 1 Variable lease income 76 76 — — Three Months Ended September 30, 2019 Operating lease income $ 30 $ 29 $ 1 $ 1 Variable lease income 80 80 — — Nine Months Ended September 30, 2020 Operating lease income $ 48 $ 43 $ 3 $ 3 Variable lease income 225 224 1 1 Nine Months Ended September 30, 2019 Operating lease income $ 48 $ 44 $ 3 $ 3 Variable lease income 209 206 3 3
Taxes Other Than Income Taxes	Taxes other than income taxes Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended September 30, 2020 Utility taxes (a) $ 237 $ 26 $ 66 $ 41 $ 21 $ 83 $ 77 $ 5 $ 1 Property 152 66 7 4 42 32 21 10 1 Payroll 59 29 7 4 4 6 2 1 1 Three Months Ended September 30, 2019 Utility taxes (a) $ 241 $ 29 $ 66 $ 38 $ 21 $ 86 $ 81 $ 5 $ — Property 148 66 7 5 39 31 21 9 — Payroll 57 28 7 3 4 6 2 1 1 Nine Months Ended September 30, 2020 Utility taxes (a) $ 651 $ 75 $ 181 $ 102 $ 65 $ 228 $ 210 $ 16 $ 2 Property 449 199 23 12 121 94 63 29 2 Payroll 183 88 21 12 13 21 6 4 3 Nine Months Ended September 30, 2019 Utility taxes (a) $ 672 $ 87 $ 183 $ 102 $ 68 $ 231 $ 217 $ 14 $ — Property 444 205 22 12 114 91 64 25 2 Payroll 185 92 21 11 13 20 5 3 2 __________ (a) Generation’s utility tax represents gross receipts tax related to its retail operations, and the Utility Registrants' utility taxes represents municipal and state utility taxes and gross receipts taxes related to their operating revenues. The offsetting collection of utility taxes from customers is recorded in revenues in the Registrants’ Consolidated Statements of Operations and Comprehensive Income.
Schedule of Other Nonoperating Income, by Component	Other, Net Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Three Months Ended September 30, 2020 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 50 $ 50 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 23 23 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units 398 398 — — — — — — — Non-regulatory agreement units 254 254 — — — — — — — Regulatory offset to NDT fund-related activities (b) (359) (359) — — — — — — — Decommissioning-related activities 366 366 — — — — — — — AFUDC — Equity 27 — 7 5 6 9 7 1 1 Non-service net periodic benefit cost 15 — — — — — — — — Three Months Ended September 30, 2019 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 67 $ 67 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 33 33 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units 89 89 — — — — — — — Non-regulatory agreement units 55 55 — — — — — — — Regulatory offset to NDT fund-related activities (b) (125) (125) — — — — — — — Decommissioning-related activities 119 119 — — — — — — — AFUDC — Equity 22 — 4 3 6 9 7 1 1 Non-service net periodic benefit cost (2) — — — — — — — — Other, net Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2020 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 127 $ 127 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 127 127 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units 111 111 — — — — — — — Non-regulatory agreement units 1 1 — — — — — — — Regulatory offset to NDT fund-related activities (b) (192) (192) — — — — — — — Decommissioning-related activities 174 174 — — — — — — — AFUDC — Equity 76 — 22 12 16 26 20 3 3 Non-service net periodic benefit cost 38 — — — — — — — — Nine Months Ended September 30, 2019 Decommissioning-related activities: Net realized income on NDT funds (a) Regulatory agreement units $ 197 $ 197 $ — $ — $ — $ — $ — $ — $ — Non-regulatory agreement units 316 316 — — — — — — — Net unrealized gains on NDT funds Regulatory agreement units 565 565 — — — — — — — Non-regulatory agreement units 236 236 — — — — — — — Regulatory offset to NDT fund-related activities (b) (611) (611) — — — — — — — Decommissioning-related activities 703 703 — — — — — — — AFUDC — Equity 64 — 13 9 16 26 18 3 4 Non-service net periodic benefit cost 8 — — — — — — — — __________ (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 Nine Months Ended September 30, 2020 Property, plant, and equipment (a) $ 2,831 $ 1,121 $ 689 $ 238 $ 293 $ 436 $ 191 $ 116 $ 104 Amortization of regulatory assets (a) 434 — 152 21 112 149 91 27 30 Amortization of intangible assets, net (a) 47 40 — — — — — — — Amortization of energy contract assets and liabilities (b) 24 22 — — — — — — — Nuclear fuel (c) 708 708 — — — — — — — ARO accretion (d) 375 375 — — — — — — — Total depreciation, amortization and accretion $ 4,419 $ 2,266 $ 841 $ 259 $ 405 $ 585 $ 282 $ 143 $ 134 Nine Months Ended September 30, 2019 Property, plant, and equipment (a) $ 2,803 $ 1,184 $ 661 $ 225 $ 263 $ 405 $ 178 $ 109 $ 89 Amortization of regulatory assets (a) 390 — 106 22 105 157 103 29 25 Amortization of intangible assets, net (a) 44 37 — — — — — — — Amortization of energy contract assets and liabilities (b) 14 14 — — — — — — — Nuclear fuel (c) 771 771 — — — — — — — ARO accretion (d) 371 371 — — — — — — — Total depreciation, amortization and accretion $ 4,393 $ 2,377 $ 767 $ 247 $ 368 $ 562 $ 281 $ 138 $ 114 __________ (a) Included in Depreciation and amortization in the Registrants' Consolidated Statements of Operations and Comprehensive Income. (b) Included in Operating revenues or Purchased power and fuel expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (c) Included in Purchased power and fuel expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. (d) Included in Operating and maintenance expense in the Registrants’ Consolidated Statements of Operations and Comprehensive Income. Other non-cash operating activities Exelon Generation ComEd PECO BGE PHI Pepco DPL ACE Nine Months Ended September 30, 2020 Pension and non-pension postretirement benefit costs $ 310 $ 89 $ 85 $ 4 $ 46 $ 52 $ 11 $ 6 $ 10 Provision for uncollectible accounts 130 16 23 38 12 41 24 15 2 Other decommissioning-related activity (a) (301) (301) — — — — — — — Energy-related options (b) 79 79 — — — — — — — True-up adjustments to decoupling mechanisms and formula rates (c) 66 — 51 (10) 10 15 (20) 15 20 Severance Costs 96 88 1 — — — — — — Provision for excess and obsolete inventory 119 118 1 1 — (1) — (1) — Long-term incentive plan (8) — — — — — — — — Amortization of operating ROU asset 185 135 1 — 23 21 5 6 2 Deferred Prosecution Agreement payments (d) 200 — 200 — — — — — — Nine Months Ended September 30, 2019 Pension and non-pension postretirement benefit costs $ 324 $ 98 $ 70 $ 9 $ 45 $ 71 $ 19 $ 11 $ 12 Provision for uncollectible accounts 89 20 26 22 5 16 7 2 6 Other decommissioning-related activity (a) (400) (400) — — — — — — — Energy-related options (b) 21 21 — — — — — — — True-up adjustments to decoupling mechanisms and formula rates (e) 72 — 80 — — (8) (9) 1 — Long-term incentive plan 33 — — — — — — — — Amortization of operating ROU asset 193 138 2 — 23 26 6 7 4 Change in environmental liabilities 23 — — — — 23 23 — — __________ (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) For ComEd, reflects the true-up adjustments in regulatory assets and liabilities associated with its distribution, energy efficiency, distributed generation, and transmission formula rates. For BGE, Pepco, and DPL, reflects the change in regulatory assets and liabilities associated with their decoupling mechanisms and transmission formula rates. For PECO and ACE, reflects the change in regulatory assets and liabilities associated with their transmission formula rates. See Note 2 — Regulatory Matters for additional information. (d) See Note 14 — Commitments and Contingencies for additional information related to the Deferred Prosecution Agreement. (e) For ComEd, reflects the true-up adjustments in regulatory assets and liabilities associated with its distribution and energy efficiency formula rates. For Pepco and DPL, reflects the change in regulatory assets and liabilities associated with their decoupling mechanisms. 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 September 30, 2020 Cash and cash equivalents $ 1,858 $ 623 $ 76 $ 242 $ 326 $ 196 $ 125 $ 26 $ 13 Restricted cash 485 100 305 7 1 38 33 — 4 Restricted cash included in other long-term assets 137 — 127 — — 10 — — 10 Total cash, cash equivalents and restricted cash $ 2,480 $ 723 $ 508 $ 249 $ 327 $ 244 $ 158 $ 26 $ 27 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 September 30, 2019 Cash and cash equivalents $ 1,683 $ 1,019 $ 76 $ 224 $ 130 $ 99 $ 18 $ 11 $ 13 Restricted cash 309 126 124 6 1 38 34 — 3 Restricted cash included in other long-term assets 186 — 171 — — 15 — — 15 Total cash, cash equivalents and restricted cash $ 2,178 $ 1,145 $ 371 $ 230 $ 131 $ 152 $ 52 $ 11 $ 31 December 31, 2018 Cash and cash equivalents $ 1,349 $ 750 $ 135 $ 130 $ 7 $ 124 $ 16 $ 23 $ 7 Restricted cash 247 153 29 5 6 43 37 1 4 Restricted cash included in other long-term assets 185 — 166 — — 19 — — 19 Total cash, cash equivalents and restricted cash $ 1,781 $ 903 $ 330 $ 135 $ 13 $ 186 $ 53 $ 24 $ 30 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 September 30, 2020 Compensation-related accruals (a) $ 898 $ 352 $ 147 $ 60 $ 72 $ 95 $ 31 $ 16 $ 14 Taxes accrued 403 183 55 25 63 84 65 10 3 Interest accrued 440 79 64 36 40 80 38 21 21 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)	9 Months Ended
	Sep. 30, 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 September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Operating revenues from affiliates: ComEd (a)(b) $ 71 $ 83 $ 241 $ 266 PECO (c) 68 43 146 123 BGE (d) 84 65 252 199 PHI 105 83 288 254 Pepco (e) 80 66 219 188 DPL (f) 21 14 60 50 ACE (g) 4 3 9 16 Other 3 1 5 2 Total operating revenues from affiliates (Generation) $ 331 $ 275 $ 932 $ 844 __________ (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 and nine months ended September 30, 2020 , respectively, ComEd’s Purchased power from Generation of $71 million and $252 million is recorded as Operating revenues from ComEd of $71 million and $241 million and as Purchased power and fuel from ComEd of less than $1 million and $11 million at Generation. For the three and nine months ended September 30, 2019 , respectively, ComEd’s Purchased power from Generation of $83 million and $270 million is recorded as Operating revenues from ComEd of $83 million and $266 million and as Purchased power and fuel from ComEd of less than $1 million and $4 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 September 30, Nine Months Ended September 30, Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 2020 2019 2020 2019 Exelon BSC $ 148 $ 125 $ 390 $ 357 PHISCO 15 16 45 57 Generation BSC $ 133 $ 138 $ 406 $ 434 13 18 37 44 ComEd BSC 65 72 204 195 49 37 133 98 PECO BSC 34 36 107 110 20 22 53 68 BGE BSC 38 38 120 116 30 30 88 89 PHI BSC 36 35 107 102 36 18 79 58 PHISCO — — — — 15 16 45 57 Pepco BSC 20 21 61 64 14 8 29 25 PHISCO 28 29 90 92 7 8 20 26 DPL BSC 13 13 38 39 12 5 26 16 PHISCO 24 24 73 74 4 4 13 16 ACE BSC 11 10 32 31 10 4 22 13 PHISCO 21 22 65 67 4 4 12 15
Current Receivables From/Payables To Affiliates	The following tables present current receivables from affiliates and current payables to affiliates: September 30, 2020 Receivables from affiliates: Payables to affiliates: Generation ComEd PECO BGE ACE BSC PHISCO Other Total Generation $ 19 $ — $ — $ — $ 69 $ — $ 25 $ 113 ComEd $ 56 (a) — — — 49 — 5 110 PECO 17 — — — 24 — 6 47 BGE 8 — — — 29 — 2 39 PHI — — — — — 3 — 10 13 Pepco 13 — — — — 16 12 2 43 DPL 2 — — — — 11 9 1 23 ACE 4 — — — 10 10 — 24 Other 9 1 — — 1 — — 11 Total $ 109 $ 20 $ — $ — $ 1 $ 211 $ 31 $ 51 $ 423 December 31, 2019 Receivables from affiliates: Payables to affiliates: Generation ComEd PECO BGE 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) As of September 30, 2020 and December 31, 2019, Generation had a contract liability with ComEd for $28 million and $37 million, respectively, that was included in Other current liabilities on Generation’s Consolidated Balance Sheets. At September 30, 2020 and December 31, 2019, ComEd had a Current Payable to Generation of $28 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: September 30, 2020 December 31, 2019 ComEd $ 2,445 $ 2,622 PECO 443 480 Other — 1 Total: $ 2,888 $ 3,103
Long Term Debt to Financing Trusts	The following table presents Long-term debt to financing trusts: September 30, 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

Regulatory Matters - Narrative

Regulatory Matters - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Aug. 26, 2020
Regulatory Matters Additional Narrative Information [Line Items]
COVID-19 Regulatory Asset	$ 60		$ 60
Competitive businesses other revenues	132	$ 194	552	$ 432
Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			255
COVID-19 Regulatory Asset	18		18
PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			135
COVID-19 Regulatory Asset	20		20
Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
COVID-19 Regulatory Asset	11		11
Increase (Decrease) in Regulatory Liabilities			(68)
Pepco Holdings LLC [Member]
Regulatory Matters Additional Narrative Information [Line Items]
COVID-19 Regulatory Asset	11		11
Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
COVID-19 Regulatory Asset	8		8
Increase (Decrease) in Regulatory Liabilities			(58)
Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
COVID-19 Regulatory Asset	3		3
Increase (Decrease) in Regulatory Liabilities			(49)
Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Proposed Capital Expenditure					$ 220
Increase (Decrease) in Regulatory Assets			58
COVID-19 Regulatory Asset	$ 0		0
Increase (Decrease) in Regulatory Liabilities			(55)
Deferred Income Tax Charge [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(73)
Deferred Income Tax Charge [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(99)
Deferred Income Tax Charge [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(54)
Deferred Income Tax Charge [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(80)
Removal Costs [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(4)
Clean Energy Legislation [Member] | Exelon Generation Co L L C [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Competitive businesses other revenues			56	$ 31
Electric Transmission Formula Rate Annual Reconciliations [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			24
Electric Transmission Formula Rate Annual Reconciliations [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			16
Electric Transmission Formula Rate Annual Reconciliations [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			13
electric energy and natural gas cost [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			24
electric energy and natural gas cost [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			(3)
Securitized Stranded Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Liabilities			9
Energy Efficiency Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			145
Deferred Income Tax Charge [Member] | PECO Energy Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			119
Deferred Storm Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			29
Uncollectible Deferral [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			19
Electric Energy Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			17
Securitized Stranded Costs [Member] | Atlantic City Electric Company [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			(9)
Electric Distribution Formula Rate One-time Events [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			58
Electric Distribution Formula Rate Annual Reconciliations [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			(37)
Asset Retirement Obligation Costs [Member] | Commonwealth Edison Co [Member]
Regulatory Matters Additional Narrative Information [Line Items]
Increase (Decrease) in Regulatory Assets			$ 47

Regulatory Matters - Schedule o

Regulatory Matters - Schedule of Completed Rate Cases (Details) (Details) - USD ($) $ in Millions	Jul. 14, 2020	Apr. 23, 2020	Dec. 04, 2019	Apr. 08, 2019
Illinois 2019 Electric Distribution Base Rate Case [Member] | Commonwealth Edison Co [Member]
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
Maryland 2019 Electric Distribution Base Rate Case [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)		$ 17
Subsequent Event [Member] | Maryland 2019 Electric Distribution Base Rate Case [Member] | Delmarva Power and Light Company [Member]
Regulatory Matters Completed Rate Cases [Line Items]
Approved Revenue Requirement Increase (Decrease)	$ 12
Approved Return on Equity, Percentage	9.60%

Regulatory Matters - Schedule_2

Regulatory Matters - Schedule of Pending Rate Cases (Details) (Details) - USD ($) $ in Millions	Oct. 26, 2020	Oct. 09, 2020	Sep. 30, 2020	Sep. 11, 2020	Jun. 01, 2020	Apr. 16, 2020
Illinois 2020 Electric Distribution Base Rate Case [Member] | Commonwealth Edison Co [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
Pennsylvania 2020 Natural Gas Distribution Base Rate Case | PECO Energy Co [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)			$ 69
Requested Return on Equity, Percentage			10.95%
Maryland 2020 Distribution Base Rate Case [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)				$ 228
Requested Return on Equity, Percentage				10.10%
Maryland 2020 Gas Distribution Base Rate Case [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)				$ 91
District of Columbia 2019 Electric Distribution Base Rate Case [Member] | Potomac Electric Power Company [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended					$ 136
Requested Return on Equity, Percentage					9.70%
District of Columbia 2019 Electric Distribution Base Rate Case [Member] | Potomac Electric Power Company [Member] | 2022 [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended					$ 73
District of Columbia 2019 Electric Distribution Base Rate Case [Member] | Potomac Electric Power Company [Member] | 2023 [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended					$ 63
Maryland 2020 Electric Distribution Base Rate Case [Member] | Baltimore Gas and Electric Company [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease)				$ 137
Maryland 2020 Electric Distribution Base Rate Case [Member] | Potomac Electric Power Company [Member] | 2023 [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended	$ 56
Maryland 2020 Electric Distribution Base Rate Case [Member] | Potomac Electric Power Company [Member] | 2024 [Member]
Regulatory Matters Pending Rate Cases [Line Items]
Requested Revenue Requirement Increase (Decrease), Amended	54
Maryland 2020 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	$ 110
Requested Return on Equity, Percentage	10.20%
Delaware 2020 Gas 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		$ 7
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 - Annual Ele

Regulatory Matters - Annual Electric Transmission Fillings (Details) - USD ($) $ in Millions	Jul. 17, 2020	May 29, 2020	May 15, 2020
2020 Transmission Formula Rate Revenue Reduction [Member] | Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 9
2020 Transmission Formula Rate Annual Update [Domain] | Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			18
Revenue			(4)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 14
Public Utilities, Approved Equity Capital Structure, Percentage			8.17%
Public Utilities, Approved Return on Equity, Percentage			11.50%
Cap on Equity Component of Rate of Return on Common Equity in Federal Energy Regulatory Committee Complaint			55.00%
2020 Transmission Formula Rate Annual Update [Domain] | PECO Energy Co [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 5
Revenue	(28)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ (23)
Public Utilities, Approved Equity Capital Structure, Percentage		7.47%
Public Utilities, Approved Return on Equity, Percentage		10.35%
Cap on Equity Component of Rate of Return on Common Equity in Federal Energy Regulatory Committee Complaint		55.75%
2020 Transmission Formula Rate Annual Update [Domain] | Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 16
Revenue			(3)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ 4
Public Utilities, Approved Equity Capital Structure, Percentage			7.26%
Public Utilities, Approved Return on Equity, Percentage			10.50%
2020 Transmission Formula Rate Annual Update [Domain] | Potomac Electric Power Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 2
Revenue			(46)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ (44)
Public Utilities, Approved Equity Capital Structure, Percentage			7.81%
Public Utilities, Approved Return on Equity, Percentage			10.50%
2020 Transmission Formula Rate Annual Update [Domain] | Delmarva Power and Light Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ (4)
Revenue			(40)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ (44)
Public Utilities, Approved Equity Capital Structure, Percentage			7.20%
Public Utilities, Approved Return on Equity, Percentage			10.50%
2020 Transmission Formula Rate Annual Update [Domain] | Atlantic City Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount			$ 5
Revenue			(25)
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount			$ (20)
Public Utilities, Approved Equity Capital Structure, Percentage			7.40%
Public Utilities, Approved Return on Equity, Percentage			10.50%

Regulatory Matters - Energy Eff

Regulatory Matters - Energy Efficiency Formula Rate (Details) - ComEd 2020 Energy Efficiency Formula Rate [Domain] - Commonwealth Edison Co [Member] - USD ($) $ in Millions	May 21, 2020	Dec. 31, 2019
Schedule of Energy Efficiency Formula Rate Updates [Line Items]
Public Utilities, Requested Rate Increase (Decrease), Amount	$ 45
Revenue	3
Public Utilities, Requested Rate Increase (Decrease), Amended, Amount	$ 48
Public Utilities, Requested Equity Capital Structure, Percentage	6.28%
Requested Return on Equity, Percentage	8.38%
Basis points for ComEd's Revenue Requirement	580
Public Utilities, Approved Return on Equity, Percentage		8.96%
Public Utilities, Approved Equity Capital Structure, Percentage		6.56%

Regulatory Matters - Regulatory

Regulatory Matters - Regulatory Assets COVID-19 (Details) $ in Millions	Sep. 30, 2020USD ($)
Public Utilities, General Disclosures [Line Items]
COVID-19 Regulatory Asset	$ 60
Commonwealth Edison Co [Member]
Public Utilities, General Disclosures [Line Items]
COVID-19 Regulatory Asset	18
PECO Energy Co [Member]
Public Utilities, General Disclosures [Line Items]
COVID-19 Regulatory Asset	20
Baltimore Gas and Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
COVID-19 Regulatory Asset	11
Pepco Holdings LLC [Member]
Public Utilities, General Disclosures [Line Items]
COVID-19 Regulatory Asset	11
Potomac Electric Power Company [Member]
Public Utilities, General Disclosures [Line Items]
COVID-19 Regulatory Asset	8
Delmarva Power and Light Company [Member]
Public Utilities, General Disclosures [Line Items]
COVID-19 Regulatory Asset	3
Atlantic City Electric Company [Member]
Public Utilities, General Disclosures [Line Items]
COVID-19 Regulatory Asset	$ 0

Regulatory Matters - Capitalize

Regulatory Matters - Capitalized Ratemaking Amount Not Recognized (Details) - USD ($) $ in Millions	Sep. 30, 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	$ 54	$ 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	0	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	47	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						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Contract Asset [Roll Forward]
Beginning Balance - Contract Assets	$ 159	$ 172	$ 174	$ 196	$ 187	$ 187	$ 174	$ 187
Consideration (received) due, contract assets	(18)	(26)	(19)	(65)	(18)	(26)
Revenues recognized, contract assets	19	13	17	39	27	26
Ending Balance - Contract Assets	160	159	172	170	196	187	160	170
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	20	29	33	21	25	27	33	27
Consideration received (due), contract liabilities	154	13	20	27	17	21
Revenues recognized, contract liabilities	(25)	(22)	(24)	(22)	(21)	(23)
Ending Balance - Contract Liabilities	149	20	29	26	21	25	149	26
Contract with Customer, Performance Obligation Satisfied in Previous Period	2			3			25	17
Exelon Generation Co L L C [Member]
Contract Asset [Roll Forward]
Beginning Balance - Contract Assets	159	172	174	196	187	187	174	187
Consideration (received) due, contract assets	(18)	(26)	(19)	(65)	(18)	(26)
Revenues recognized, contract assets	19	13	17	39	27	26
Ending Balance - Contract Assets	160	159	172	170	196	187	160	170
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	27	56	71	26	39	42	71	42
Consideration received (due), contract liabilities	94	34	55	83	52	63
Revenues recognized, contract liabilities	(65)	(63)	(70)	(61)	(65)	(66)
Ending Balance - Contract Liabilities	56	27	56	48	26	39	56	48
Contract with Customer, Performance Obligation Satisfied in Previous Period	2			3			63	32
Pepco Holdings LLC [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	0	0	0	0	0	0	0	0
Consideration received (due), contract liabilities	124	0	0	0	0	0
Revenues recognized, contract liabilities	(2)	0	0	0	0	0
Ending Balance - Contract Liabilities	122	0	0	0	0	0	122	0
Potomac Electric Power Company [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	0	0	0	0	0	0	0	0
Consideration received (due), contract liabilities	98	0	0	0	0	0
Revenues recognized, contract liabilities	(2)	0	0	0	0	0
Ending Balance - Contract Liabilities	96	0	0	0	0	0	96	0
Delmarva Power and Light Company [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	0	0	0	0	0	0	0	0
Consideration received (due), contract liabilities	13	0	0	0	0	0
Revenues recognized, contract liabilities	0	0	0	0	0	0
Ending Balance - Contract Liabilities	13	0	0	0	0	0	13	0
Atlantic City Electric Company [Member]
Contract Liabilities [Roll Forward]
Beginning Balance - Contract Liabilities	0	0	0	0	0	0	0	0
Consideration received (due), contract liabilities	13	0	0	0	0	0
Revenues recognized, contract liabilities	0	0	0	0	0	0
Ending Balance - Contract Liabilities	$ 13	$ 0	$ 0	$ 0	$ 0	$ 0	$ 13	$ 0

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Performance Obligations (Details) $ in Millions	Sep. 30, 2020USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 831
Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	900
Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	122
Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	96
Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	13
Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	13
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	92
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01 | Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	136
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01 | Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01 | Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01 | Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01 | Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	0
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	223
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 | Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	313
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 | Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	9
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 | Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 | Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 | Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	1
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	93
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 | Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	123
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 | Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 | Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 | Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 | Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	1
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	53
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 | Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	53
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 | Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	8
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 | Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 | Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 | Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	1
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	370
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 | Exelon Generation Co L L C [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	275
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 | Pepco Holdings LLC [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	95
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 | Potomac Electric Power Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	75
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 | Delmarva Power and Light Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	10
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 | Atlantic City Electric Company [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 10

Segment Information - Narrative

Segment Information - Narrative (Details)	9 Months Ended
	Sep. 30, 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						9 Months Ended
		Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Competitive businesses other revenues		$ 132			$ 194			$ 552	$ 432
Revenues		8,853			8,929			24,925	26,096
Revenue from Related Parties		1			0			4	0
Depreciation and Amortization		1,289			1,083			3,312	3,237
Operating Expenses		8,087			7,559			22,387	22,703
Interest expense, net		404			409			1,241	1,221
Income (Loss) before income taxes		786			1,102			1,665	3,028
Income taxes		216			172			141	626
Net income (loss)		569	$ 574	$ 376	760	$ 494	$ 966	1,519	2,220
Capital expenditures		1,833			1,687			5,606	5,259
Assets	[1]	127,767						127,767		$ 124,977
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenues		4,659			4,774			13,272	14,280
Revenue from Related Parties		331			275			932	844
Income (Loss) before income taxes		219			501			532	1,355
Income taxes		100			87			41	388
Net income (loss)		117	529	(161)	244	118	422	485	784
Capital expenditures								1,212	1,282
Assets	[2]	47,372						47,372		48,995
Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		1,368			1,380			3,554	3,700
Revenue from Related Parties		6			4			13	11
Income (Loss) before income taxes		215			203			340	436
Income taxes		(1)			14			(77)	25
Net income (loss)		216	$ 94	$ 108	189	$ 106	$ 117	418	412
Capital expenditures								1,072	1,006
Assets	[3]	23,394						23,394		22,719
Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		71			83			241	266
PECO Energy Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		68			43			146	123
Baltimore Gas And Electric Company Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		84			65			252	199
Operating Segment [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		31			(9)			(15)	4
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		(3)			(1)			(5)	(4)
Revenues		(845)			(763)			(2,430)	(2,296)
Revenue from Related Parties		(845)			(764)			(2,430)	(2,300)
Depreciation and Amortization		0			0			0	0
Operating Expenses		(833)			(759)			(2,397)	(2,291)
Interest expense, net		0			0			0	0
Income (Loss) before income taxes		0			0			0	0
Income taxes		0			0			0	0
Net income (loss)		0			0			0	0
Capital expenditures		0			0			0	0
Assets		(10,016)						(10,016)		(10,089)
Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		(91)			(92)			(281)	(298)
Revenue from Related Parties		(91)			(93)			(281)	(298)
Depreciation and Amortization		0			0			0	0
Operating Expenses		(91)			(94)			(281)	(298)
Interest expense, net		0			0			0	0
Income (Loss) before income taxes		0			0			0	0
Income taxes		0			0			0	0
Net income (loss)		0			0			0	0
Capital expenditures		0			0			0	0
Assets		(265)						(265)		(40)
Exelon Generation Co L L C [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		135			195			557	436
Revenues		4,659			4,774			13,272	14,280
Depreciation and Amortization		558			407			1,161	1,221
Operating Expenses		4,727			4,274			12,674	13,333
Interest expense, net		80			109			277	336
Income (Loss) before income taxes		219			501			532	1,355
Income taxes		100			87			41	388
Net income (loss)		117			244			485	784
Capital expenditures		282			392			1,212	1,282
Assets		47,372						47,372		48,995
Exelon Generation Co L L C [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		331			275			932	844
Commonwealth Edison Co [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Revenues		1,643			1,583			4,499	4,342
Depreciation and Amortization		294			259			841	767
Operating Expenses		1,302			1,256			3,798	3,431
Interest expense, net		95			91			287	268
Income (Loss) before income taxes		256			245			446	674
Income taxes		60			45			142	130
Net income (loss)		196			200			304	544
Capital expenditures		554			452			1,583	1,413
Assets		34,243						34,243		32,765
Commonwealth Edison Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		15			4			31	13
PECO Energy Co [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Revenues		813			778			2,306	2,333
Depreciation and Amortization		85			83			259	247
Operating Expenses		658			595			1,900	1,783
Interest expense, net		39			33			108	100
Income (Loss) before income taxes		122			154			310	461
Income taxes		(16)			14			(7)	51
Net income (loss)		138			140			317	410
Capital expenditures		312			228			824	675
Assets		12,334						12,334		11,469
PECO Energy Co [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		3			1			7	4
Baltimore Gas and Electric Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Revenues		731			703			2,284	2,327
Depreciation and Amortization		133			116			405	368
Operating Expenses		642			612			1,903	1,936
Interest expense, net		34			31			99	89
Income (Loss) before income taxes		61			67			299	320
Income taxes		8			12			26	59
Net income (loss)		53			55			273	261
Capital expenditures		290			300			838	842
Assets		11,370						11,370		10,634
Baltimore Gas and Electric Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		6			6			16	18
Pepco Holdings LLC [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Revenues		1,368			1,380			3,554	3,700
Depreciation and Amortization		200			193			585	562
Operating Expenses		1,102			1,124			3,057	3,106
Interest expense, net		67			66			201	197
Income (Loss) before income taxes		215			203			340	436
Income taxes		(1)			14			(77)	25
Net income (loss)		216			189			418	412
Capital expenditures		386			308			1,072	1,006
Assets		23,394						23,394		22,719
Pepco Holdings LLC [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		6			4			13	11
Potomac Electric Power Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		611			642			1,650	1,748
Depreciation and Amortization		96			95			282	281
Operating Expenses		465			515			1,364	1,444
Interest expense, net		35			33			103	100
Income (Loss) before income taxes		121			103			211	226
Income taxes		3			5			(16)	9
Net income (loss)		118			98			227	217
Capital expenditures		188			157			512	455
Assets		9,227						9,227		8,661
Potomac Electric Power Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		3			2			6	5
Delmarva Power and Light Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		337			319			954	987
Depreciation and Amortization		48			46			143	138
Operating Expenses		296			268			843	820
Interest expense, net		15			15			47	45
Income (Loss) before income taxes		28			38			71	132
Income taxes		1			5			(20)	16
Net income (loss)		27			33			91	116
Capital expenditures		94			85			278	245
Assets		4,992						4,992		4,830
Delmarva Power and Light Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		3			1			7	5
Atlantic City Electric Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenues		420			419			952	966
Depreciation and Amortization		48			43			134	114
Operating Expenses		338			340			847	838
Interest expense, net		15			15			45	44
Income (Loss) before income taxes		68			65			67	89
Income taxes		(7)			2			(39)	2
Net income (loss)		75			63			106	87
Capital expenditures		103			73			281	300
Assets		4,201						4,201		3,933
Atlantic City Electric Company [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		1			1			3	2
Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Competitive businesses other revenues		0			0			0	0
Revenues		484			474			1,440	1,410
Depreciation and Amortization		19			25			61	72
Operating Expenses		489			457			1,452	1,405
Interest expense, net		89			79			269	231
Income (Loss) before income taxes		(87)			(68)			(262)	(218)
Income taxes		65			0			16	(27)
Net income (loss)		(151)			(68)			(278)	(191)
Capital expenditures		9			7			77	41
Assets		9,070						9,070		8,484
Corporate and Other [Member] | Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenues		91			92			279	297
Depreciation and Amortization		8			9			26	29
Operating Expenses		94			95			284	302
Interest expense, net		2			3			6	8
Income (Loss) before income taxes		(2)			(3)			(9)	(11)
Income taxes		2			2			(2)	(2)
Net income (loss)		(4)			(5)			(6)	(8)
Capital expenditures		1			(7)			1	6
Assets		5,239						5,239		5,335
Corporate and Other [Member] | Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member] | Revision of Prior Period, Adjustment [Member]
Segment Reporting Information [Line Items]
Income (Loss) before income taxes					195				422
Assets										$ 5,700
Corporate and Other [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		485			474			1,435	1,410
Corporate and Other [Member] | Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties		90			93			278	297
Electricity, Generation [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		3,875			4,039			10,447	11,525
Electricity, Generation [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(326)			(275)			(920)	(840)
Electricity, Generation [Member] | Exelon Generation Co L L C [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		4,201			4,314			11,367	12,365
Electricity, Generation [Member] | Commonwealth Edison Co [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, Generation [Member] | PECO Energy Co [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, Generation [Member] | Baltimore Gas and Electric Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, Generation [Member] | Pepco Holdings LLC [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, Generation [Member] | Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Oil and Gas, Purchased [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		323			266			1,345	1,479
Oil and Gas, Purchased [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			1			(3)	0
Oil and Gas, Purchased [Member] | Exelon Generation Co L L C [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		323			265			1,348	1,479
Oil and Gas, Purchased [Member] | Commonwealth Edison Co [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Oil and Gas, Purchased [Member] | PECO Energy Co [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Oil and Gas, Purchased [Member] | Baltimore Gas and Electric Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Oil and Gas, Purchased [Member] | Pepco Holdings LLC [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Oil and Gas, Purchased [Member] | Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, US Regulated
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		4,365			4,268			11,585	11,609
Electricity, US Regulated | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,308			1,365			3,440	3,570
Electricity, US Regulated | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(22)			(7)			(50)	(25)
Electricity, US Regulated | Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(6)			(3)			(15)	(10)
Electricity, US Regulated | Exelon Generation Co L L C [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, US Regulated | Commonwealth Edison Co [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,643			1,583			4,499	4,342
Electricity, US Regulated | PECO Energy Co [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		759			716			1,948	1,901
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		646			619			1,763	1,817
Electricity, US Regulated | Pepco Holdings LLC [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		1,339			1,357			3,425	3,574
Electricity, US Regulated | Potomac Electric Power Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		611			642			1,650	1,748
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		314			299			838	871
Electricity, US Regulated | Atlantic City Electric Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		420			419			952	966
Electricity, US Regulated | Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Electricity, US Regulated | Corporate and Other [Member] | Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	(1)
Natural Gas, US Regulated
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		159			163			990	1,046
Natural Gas, US Regulated | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		23			20			116	115
Natural Gas, US Regulated | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(3)			(3)			(5)	(12)
Natural Gas, US Regulated | Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | Exelon Generation Co L L C [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | PECO Energy Co [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		54			62			358	432
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		85			84			521	510
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		23			20			116	116
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		23			20			116	116
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Natural Gas, US Regulated | Corporate and Other [Member] | Corporate, Non-Segment [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(1)			(1)			6	5
Service, Other [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(491)			(478)			(1,447)	(1,415)
Service, Other [Member] | Intersegment Eliminations [Member] | Pepco Holdings LLC [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		(85)			(89)			(266)	(288)
Service, Other [Member] | Exelon Generation Co L L C [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Commonwealth Edison Co [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | PECO Energy Co [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Baltimore Gas and Electric Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Pepco Holdings LLC [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		6			3			13	10
Service, Other [Member] | Potomac Electric Power Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Delmarva Power and Light Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Atlantic City Electric Company [Member] | Operating Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		0			0			0	0
Service, Other [Member] | Corporate and Other [Member] | Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax		484			474			1,440	1,410
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		$ 91			$ 92			$ 279	$ 298
[1]	Exelon’s consolidated assets include $10,102 million and $9,532 million at September 30, 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 $3,531 million and $3,473 million at September 30, 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 $10,082 million and $9,512 million at September 30, 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 $3,499 million and $3,429 million at September 30, 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 $20 million and $20 million at September 30, 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 $32 million and $44 million at September 30, 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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 8,853	$ 8,929	$ 24,925	$ 26,096
Revenue from Related Parties	1	0	4	0
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,313	1,364	3,561	3,809
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	1,043	1,082	3,007	3,224
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	406	429	1,061	1,211
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	330	365	754	805
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	1,109	1,040	2,984	3,254
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	4,201	4,280	11,367	12,303
Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	323	299	1,348	1,541
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	135	195	557	436
Unrealized Gain (Loss) on Securities	37	77	238	64
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,659	4,774	13,272	14,280
Operating Segment [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,307	1,361	3,540	3,807
Operating Segment [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	1,042	1,099	3,013	3,255
Operating Segment [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	406	429	1,062	1,211
Operating Segment [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	323	360	734	792
Operating Segment [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	1,123	1,065	3,018	3,300
Operating Segment [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	4,201	4,314	11,367	12,365
Operating Segment [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	323	265	1,348	1,479
Operating Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Unrealized Gain (Loss) on Securities	255	17	472	(84)
Operating Segment [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,659	4,774	13,272	14,280
Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	135	195	557	436
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(845)	(763)	(2,430)	(2,296)
Revenue from Related Parties	(845)	(764)	(2,430)	(2,300)
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	6	3	21	2
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	1	(17)	(6)	(31)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0	(1)	0
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	7	5	20	13
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	(14)	(25)	(34)	(46)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	(34)	0	(62)
Intersegment Eliminations [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	34	0	62
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0	0	0
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	0	0	0	0
Revenue from Contract with Customer [Member] | Operating Segment [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	1,327	1,351	3,692	3,798
Revenue from Contract with Customer [Member] | Operating Segment [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	974	1,052	2,773	3,083
Revenue from Contract with Customer [Member] | Operating Segment [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	401	414	1,074	1,195
Revenue from Contract with Customer [Member] | Operating Segment [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	249	288	579	594
Revenue from Contract with Customer [Member] | Operating Segment [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	937	873	2,718	2,849
Revenue from Contract with Customer [Member] | Operating Segment [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	3,888	3,978	10,836	11,519
Revenue from Contract with Customer [Member] | Operating Segment [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	169	160	881	1,041
Revenue from Contract with Customer [Member] | Operating Segment [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	4,142	4,250	11,985	12,903
Revenue from Contract with Customer [Member] | Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	85	112	268	343
Other [Member] | Operating Segment [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	(20)	10	(152)	9
Other [Member] | Operating Segment [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	68	47	240	172
Other [Member] | Operating Segment [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	5	15	(12)	16
Other [Member] | Operating Segment [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	74	72	155	198
Other [Member] | Operating Segment [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	186	192	300	451
Other [Member] | Operating Segment [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	313	336	531	846
Other [Member] | Operating Segment [Member] | Generation Natural Gas [Member]
Segment Reporting Information [Line Items]
Revenues	154	105	467	438
Other [Member] | Operating Segment [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	517	524	1,287	1,377
Other [Member] | Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	$ 50	$ 83	$ 289	$ 93

Segment Information - Generat_2

Segment Information - Generation Total Revenues Net of Purchased Power and Fuel Expense (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	$ 591	$ 689	$ 1,683	$ 2,023
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	750	747	2,178	2,247
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	285	291	725	810
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	147	72	325	225
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	225	184	538	478
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	1,998	1,983	5,449	5,783
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	347	140	862	349
Unrealized Gain (Loss) on Securities	37	77	238	64
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenue Net of Purchase Power And Fuel	2,345	2,123	6,311	6,132
Operating Segment [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
RNF from external customers	586	684	1,660	2,007
Operating Segment [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
RNF from external customers	748	763	2,180	2,269
Operating Segment [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
RNF from external customers	281	288	714	800
Operating Segment [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
RNF from external customers	141	76	311	252
Operating Segment [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
RNF from external customers	253	212	608	542
Operating Segment [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
RNF from external customers	2,009	2,023	5,473	5,870
Operating Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
RNF from external customers	336	100	838	262
Revenue Net of Purchase Power And Fuel		(3)		(13)
Unrealized Gain (Loss) on Securities	255	17	472	(84)
Accelerated nuclear fuel amortization	24		24
Asset Impairment Charges	10		10
Operating Segment [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
RNF from external customers	2,345	2,123	6,311	6,132
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	5	5	23	16
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	2	(16)	(2)	(22)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	4	3	11	10
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	6	(4)	14	(27)
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(28)	(28)	(70)	(64)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	(11)	(40)	(24)	(87)
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	11	40	24	87
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Intersegment Revenue Net Of Purchase Power And Fuel	$ 0	$ 0	$ 0	$ 0

Segment Information - Electric

Segment Information - Electric and Gas Revenue by Customer Class (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue, Major Customer [Line Items]
Revenues	$ 8,853	$ 8,929	$ 24,925	$ 26,096
Revenue from Related Parties	1	0	4	0
Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenues	1,643	1,583	4,499	4,342
Revenue from Related Parties	15	4	31	13
Commonwealth Edison Co [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(38)	(56)	(51)	(98)
Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,678	1,633	4,540	4,418
Commonwealth Edison Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(35)	(50)	(41)	(76)
PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenues	813	778	2,306	2,333
Revenue from Related Parties	3	1	7	4
PECO Energy Co [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5	(11)	10	(16)
PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	808	785	2,293	2,338
PECO Energy Co [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	5	(7)	13	(5)
PECO Energy Co [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	3	1	6	4
PECO Energy Co [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	0	0	1	0
Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenues	731	703	2,284	2,327
Revenue from Related Parties	6	6	16	18
Baltimore Gas and Electric Company [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	(9)	(5)	(10)	11
Baltimore Gas and Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	740	704	2,290	2,303
Baltimore Gas and Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	(9)	(1)	(6)	24
Baltimore Gas and Electric Company [Member] | Rate-Regulated Electric Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	3	2	9	5
Baltimore Gas and Electric Company [Member] | Rate-Regulated Natural Gas Revenues [Member]
Revenue, Major Customer [Line Items]
Revenue from Related Parties	3	4	7	13
Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenues	1,368	1,380	3,554	3,700
Revenue from Related Parties	6	4	13	11
Pepco Holdings LLC [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	31	(9)	(15)	4
Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	1,337	1,386	3,567	3,689
Pepco Holdings LLC [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	31	(6)	(13)	11
Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenues	611	642	1,650	1,748
Revenue from Related Parties	3	2	6	5
Potomac Electric Power Company [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	18	(3)	20	10
Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	593	643	1,629	1,732
Potomac Electric Power Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	18	(1)	21	16
Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenues	337	319	954	987
Revenue from Related Parties	3	1	7	5
Delmarva Power and Light Company [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	8	(6)	(15)	(6)
Delmarva Power and Light Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	329	325	968	991
Delmarva Power and Light Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	8	(6)	(14)	(4)
Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenues	420	419	952	966
Revenue from Related Parties	1	1	3	2
Atlantic City Electric Company [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5	1	(20)	0
Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenues	415	418	972	966
Atlantic City Electric Company [Member] | Other Regulated Revenue [Member]
Revenue, Major Customer [Line Items]
Revenues	5	1	(20)	0
Electricity, US Regulated
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4,365	4,268	11,585	11,609
Electricity, US Regulated | Commonwealth Edison Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,666	1,635	4,519	4,427
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,678	1,633	4,540	4,418
Electricity, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	6	10	22
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	920	865	2,389	2,221
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	379	393	1,067	1,103
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	135	141	388	399
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	10	12	33	35
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	234	222	663	660
Electricity, US Regulated | PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	751	726	1,931	1,914
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	753	723	1,934	1,907
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	4	3	10
Electricity, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	518	479	1,277	1,231
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	104	109	291	304
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	66	63	174	163
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	9	21	23
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	63	171	186
Electricity, US Regulated | Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	649	623	1,775	1,814
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	652	621	1,781	1,809
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	3	3	10
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	389	352	1,034	1,019
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	65	64	183	193
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	113	116	311	335
Electricity, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	7	7	20	20
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	78	82	233	242
Electricity, US Regulated | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,308	1,365	3,440	3,570
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,314	1,366	3,451	3,574
Electricity, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	3	2	7
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	763	741	1,825	1,816
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	134	147	355	387
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	262	297	755	843
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	14	17	45	47
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	141	164	471	481
Electricity, US Regulated | Potomac Electric Power Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	590	643	1,624	1,733
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	593	643	1,629	1,732
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	2	1	6
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	307	311	779	792
Electricity, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	36	41	101	114
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	195	222	558	633
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	8	11	25	27
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	47	58	166	166
Electricity, US Regulated | Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	303	304	846	872
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	306	305	852	876
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	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	193	178	501	499
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	45	48	127	141
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	21	26	66	75
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	3	10	10
Electricity, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	44	50	148	151
Electricity, US Regulated | Atlantic City Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	414	417	969	964
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	415	418	972	966
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	263	252	545	525
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	53	58	127	132
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	46	49	131	135
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Public Authorities & Electric Railroads [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	3	10	10
Electricity, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	50	56	159	164
Natural Gas, US Regulated
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	159	163	990	1,046
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Commonwealth Edison Co [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | PECO Energy Co [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	54	62	358	431
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	55	62	359	431
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	1
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	32	38	252	285
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	16	17	86	122
Natural Gas, US Regulated | PECO Energy Co [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	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	5	18	18
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	3	5
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	85	79	503	484
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	88	83	509	494
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	1	1	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	55	49	342	327
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	9	9	55	55
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	21	20	96	93
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Baltimore Gas and Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3	5	16	19
Natural Gas, US Regulated | Pepco Holdings LLC [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	23	20	116	115
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	23	20	116	115
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Pepco Holdings LLC [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	11	9	68	64
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	6	4	30	30
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	3	4
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	3	4	10	11
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	2	5	6
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Potomac Electric Power Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Delmarva Power and Light Company [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	23	20	116	116
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	23	20	116	115
Natural Gas, US Regulated | Delmarva Power and Light Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	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	11	9	68	64
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	6	4	30	30
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	3	4
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	3	4	10	11
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	2	5	6
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Operating Segment [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Residential [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Small Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Large Commercial & Industrial [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Transportation [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	0	0	0	0
Natural Gas, US Regulated | Atlantic City Electric Company [Member] | Regulated Operation [Member] | Other [Member]
Revenue, Major Customer [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 0	$ 0	$ 0	$ 0

Accounts Receivable Accounts Re

Accounts Receivable Accounts Receivable - Narrative (Details) - Sale of accounts receivable [Member] - USD ($) $ in Millions	Sep. 30, 2020	Apr. 08, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 750
Derecognized receivables transferred at fair value	1,232	$ 1,200
Cash proceeds received	500	500
Deferred purchase price	732	650
Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	750
Derecognized receivables transferred at fair value	1,232	1,200
Cash proceeds received	500	500
Deferred purchase price	$ 732	$ 650

Accounts Receivable - Allowance

Accounts Receivable - Allowance for Credit Losses Rollforward (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses		$ (130)	$ (89)
Exelon Generation Co L L C [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses		(16)	(20)
Commonwealth Edison Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses		(23)	(26)
PECO Energy Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses		(38)	(22)
Baltimore Gas and Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses		(12)	(5)
Pepco Holdings LLC [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses		(41)	(16)
Potomac Electric Power Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses		(24)	(7)
Delmarva Power and Light Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses		(15)	(2)
Atlantic City Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Current Period Provision for Expected Credit Losses		(2)	$ (6)
Customer accounts receivable
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	$ 261	243
Current Period Provision for Expected Credit Losses	114	222
Writeoffs, net of recoveries	17	51
Allowance change due to sale of customer accounts		56
Ending balance	358	358
Customer accounts receivable | Exelon Generation Co L L C [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	33	80
Current Period Provision for Expected Credit Losses	1	13
Writeoffs, net of recoveries	1	4
Allowance change due to sale of customer accounts		56
Ending balance	33	33
Customer accounts receivable | Commonwealth Edison Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	72	59
Current Period Provision for Expected Credit Losses	37	62
Writeoffs, net of recoveries	4	16
Ending balance	105	105
Customer accounts receivable | PECO Energy Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	71	55
Current Period Provision for Expected Credit Losses	27	56
Writeoffs, net of recoveries	2	15
Ending balance	96	96
Customer accounts receivable | Baltimore Gas and Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	23	12
Current Period Provision for Expected Credit Losses	14	28
Writeoffs, net of recoveries	2	5
Ending balance	35	35
Customer accounts receivable | Pepco Holdings LLC [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	62	37
Current Period Provision for Expected Credit Losses	35	63
Writeoffs, net of recoveries	8	11
Ending balance	89	89
Customer accounts receivable | Potomac Electric Power Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	24	13
Current Period Provision for Expected Credit Losses	11	24
Writeoffs, net of recoveries	0	2
Ending balance	35	35
Customer accounts receivable | Delmarva Power and Light Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	18	11
Current Period Provision for Expected Credit Losses	7	14
Writeoffs, net of recoveries	3	3
Ending balance	22	22
Customer accounts receivable | Atlantic City Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	20	13
Current Period Provision for Expected Credit Losses	17	25
Writeoffs, net of recoveries	5	6
Ending balance	32	32
Other receivables
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	61	48
Current Period Provision for Expected Credit Losses	15	36
Writeoffs, net of recoveries	1	9
Ending balance	75	75
Other receivables | Exelon Generation Co L L C [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	0	0
Current Period Provision for Expected Credit Losses	0	0
Writeoffs, net of recoveries	0	0
Ending balance	0	0
Other receivables | Commonwealth Edison Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	22	20
Current Period Provision for Expected Credit Losses	5	9
Writeoffs, net of recoveries	0	2
Ending balance	27	27
Other receivables | PECO Energy Co [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	7	7
Current Period Provision for Expected Credit Losses	1	3
Writeoffs, net of recoveries	1	3
Ending balance	7	7
Other receivables | Baltimore Gas and Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	6	5
Current Period Provision for Expected Credit Losses	3	7
Writeoffs, net of recoveries	0	3
Ending balance	9	9
Other receivables | Pepco Holdings LLC [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	26	16
Current Period Provision for Expected Credit Losses	6	17
Writeoffs, net of recoveries	0	1
Ending balance	32	32
Other receivables | Potomac Electric Power Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	11	7
Current Period Provision for Expected Credit Losses	2	6
Writeoffs, net of recoveries	0	0
Ending balance	13	13
Other receivables | Delmarva Power and Light Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	7	4
Current Period Provision for Expected Credit Losses	1	4
Writeoffs, net of recoveries	0	0
Ending balance	8	8
Other receivables | Atlantic City Electric Company [Member]
Accounts Receivable, Allowance for Credit Loss [Line Items]
Beginning balance	8	5
Current Period Provision for Expected Credit Losses	3	7
Writeoffs, net of recoveries	0	1
Ending balance	$ 11	$ 11

Accounts Receivable - Unbilled

Accounts Receivable - Unbilled Customer Revenue (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	$ 672	$ 1,535
Exelon Generation Co L L C [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	139	807
Commonwealth Edison Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	193	218
PECO Energy Co [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	98	146
Baltimore Gas and Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	115	170
Pepco Holdings LLC [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	127	194
Potomac Electric Power Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	72	100
Delmarva Power and Light Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	37	61
Atlantic City Electric Company [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unbilled customer revenue	$ 18	$ 33

Accounts Receivable - Purchases

Accounts Receivable - Purchases and Sales of Accounts Receivable (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Apr. 08, 2020
Purchases of Accounts Receivable [Line Items]
Loss on sale receivables	$ 8	$ 23
Proceeds from new transfers		1,889
Cash collections received on deferred purchase price		2,518
Cash collections reinvested in the Facility		4,407
Accounts Receivable, Purchase		2,698
Accounts Receivable, Sale		542
Exelon Generation Co L L C [Member]
Purchases of Accounts Receivable [Line Items]
Loss on sale receivables	8	23
Proceeds from new transfers		1,889
Cash collections received on deferred purchase price		2,518
Cash collections reinvested in the Facility		4,407
Accounts Receivable, Purchase		0
Accounts Receivable, Sale		790
Commonwealth Edison Co [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase		865
Accounts Receivable, Sale		0
PECO Energy Co [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase		786
Accounts Receivable, Sale		0
Baltimore Gas and Electric Company [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase		508
Accounts Receivable, Sale		0
Pepco Holdings LLC [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase		787
Accounts Receivable, Sale		0
Potomac Electric Power Company [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase		484
Accounts Receivable, Sale		0
Delmarva Power and Light Company [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase		160
Accounts Receivable, Sale		0
Atlantic City Electric Company [Member]
Purchases of Accounts Receivable [Line Items]
Accounts Receivable, Purchase		143
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		75
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		248
Sale of accounts receivable [Member]
Purchases of Accounts Receivable [Line Items]
Derecognized receivables transferred at fair value	1,232	1,232	$ 1,200
Cash proceeds received	500	500	500
Deferred purchase price	732	732	650
Transfer of Financial Assets Accounted for as Sales [Line Items]		4,515
Sale of accounts receivable [Member] | Exelon Generation Co L L C [Member]
Purchases of Accounts Receivable [Line Items]
Derecognized receivables transferred at fair value	1,232	1,232	1,200
Cash proceeds received	500	500	500
Deferred purchase price	$ 732	732	$ 650
Transfer of Financial Assets Accounted for as Sales [Line Items]		$ 4,515

Early Plant Retirements - Narra

Early Plant Retirements - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization	$ 1,289	$ 1,083	$ 3,312	$ 3,237
Operating Expenses	8,087	7,559	22,387	22,703
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization	$ 558	$ 407	$ 1,161	$ 1,221
Salem [Member] | Nuclear Plant [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Ownership interest	42.59%		42.59%
Midwest Asset Group [Member]
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization			$ 6
Generation New England [Member]
Property, Plant and Equipment [Line Items]
Operating Expenses			43
Generation New England [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Cost, Depreciation and Amortization			6
Operating Expenses			43
Facility Closing [Member] | Midwest Asset Group [Member]
Property, Plant and Equipment [Line Items]
Operating Expenses			81
Facility Closing [Member] | Midwest Asset Group [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Operating Expenses			$ 81

Early Plant Retirements - Preta

Early Plant Retirements - Pretax Expense (Details) - Facility Closing [Member] - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
TMOysterCreek [Member]
Accelerated depreciation	$ 71		$ 216
Accelerated nuclear fuel amortization	3		13
Operating and maintenance	0		0
Asset Retirement Obligation, Revision of Estimate	39		(44)
Asset Retirement Obligation Contractual Offset	0		0
Restructuring and Related Cost, Incurred Cost	113		185
Byron Dresden
Accelerated depreciation		$ 254
Accelerated nuclear fuel amortization		14
Operating and maintenance		220
Asset Retirement Obligation, Revision of Estimate		34
Asset Retirement Obligation Contractual Offset		(129)
Restructuring and Related Cost, Incurred Cost		393
Exelon Generation Co L L C [Member] | TMOysterCreek [Member]
Accelerated depreciation	71		216
Accelerated nuclear fuel amortization	3		13
Operating and maintenance	0		0
Asset Retirement Obligation, Revision of Estimate	39		(44)
Asset Retirement Obligation Contractual Offset	0		0
Restructuring and Related Cost, Incurred Cost	$ 113		$ 185
Exelon Generation Co L L C [Member] | Byron Dresden
Accelerated depreciation		254
Accelerated nuclear fuel amortization		14
Operating and maintenance		220
Asset Retirement Obligation, Revision of Estimate		34
Asset Retirement Obligation Contractual Offset		(129)
Restructuring and Related Cost, Incurred Cost		$ 393

Early Plant Retirements - Impli

Early Plant Retirements - Implications of Potential Early Plant Retirement on Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	$ 1,405	$ 1,456
Property, plant and equipment, net	82,561	80,233
Braidwood [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	82
Nuclear fuel inventory, net	147
Property, plant and equipment, net	1,403
Construction work in progress	18
Asset retirement obligation	(570)
Lasalle [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Inventory, Raw Materials, Net of Reserves	107
Nuclear fuel inventory, net	218
Property, plant and equipment, net	1,571
Construction work in progress	23
Asset retirement obligation	(926)
Dresden Byron Braidwood [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	189
Nuclear fuel inventory, net	365
Property, plant and equipment, net	2,974
Construction work in progress	41
Asset retirement obligation	(1,496)
Exelon Generation Co L L C [Member]
Implications of Potential Early Plant Retirement [Line Items]
Materials and supplies inventory, net	971	1,026
Property, plant and equipment, net	23,709	$ 24,193
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	82
Nuclear fuel inventory, net	147
Property, plant and equipment, net	1,403
Construction work in progress	18
Asset retirement obligation	(570)
Exelon Generation Co L L C [Member] | Lasalle [Member] | Facility Closing [Member]
Implications of Potential Early Plant Retirement [Line Items]
Inventory, Raw Materials, Net of Reserves	107
Nuclear fuel inventory, net	218
Property, plant and equipment, net	1,571
Construction work in progress	23
Asset retirement obligation	(926)
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	189
Nuclear fuel inventory, net	365
Property, plant and equipment, net	2,974
Construction work in progress	41
Asset retirement obligation	$ (1,496)

Nuclear Decommissioning - Narra

Nuclear Decommissioning - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	$ 13,432	$ 13,190
Nuclear Decommissioning [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Net increase (decrease) due to changes in, and timing of, estimated future cash flows	806
Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	13,432	13,190
Exelon Generation Co L L C [Member] | Nuclear Decommissioning [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Net increase (decrease) due to changes in, and timing of, estimated future cash flows	806
Other Current Assets [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	115	163
Other Current Assets [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	115	163
Assets, Total [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	13,547	13,353
Assets, Total [Member] | Exelon Generation Co L L C [Member]
Nuclear Decommissioning Additional Narrative Information [Line Items]
Nuclear decommissioning trust funds	$ 13,547	$ 13,353

Nuclear Decommissioning - Rollf

Nuclear Decommissioning - Rollforward of Nuclear Decommissioning ARO (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Accretion expense	$ 375	$ 371
Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Accretion expense	375	$ 371
Nuclear Decommissioning [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance	10,504
Accretion expense	367
Net increase (decrease) due to changes in, and timing of, estimated future cash flows	806
Costs incurred related to decommissioning plants	(59)
ARO ending balance	11,618
Current portion of ARO	93		$ 112
Nuclear Decommissioning [Member] | Exelon Generation Co L L C [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
ARO beginning balance	10,504
Accretion expense	367
Net increase (decrease) due to changes in, and timing of, estimated future cash flows	806
Costs incurred related to decommissioning plants	(59)
ARO ending balance	11,618
Current portion of ARO	$ 93		$ 112

Asset Impairments - Narrative (

Asset Impairments - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)MW	Sep. 30, 2019USD ($)
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use			$ 567	$ 174
Net income (loss) attributable to noncontrolling interests	$ 68	$ (12)	(85)	56
Deferred income taxes and amortization of investment tax credits			164	412
Certain Distributed Energy Companies [Member]
Property, Plant and Equipment [Line Items]
Equity Method Investment, Other than Temporary Impairment		164
Net income (loss) attributable to noncontrolling interests		96
Deferred income taxes and amortization of investment tax credits		(46)
Income (Loss) from Equity Method Investments		(15)
Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use			552	174
Net income (loss) attributable to noncontrolling interests	68	(13)	(85)	56
Deferred income taxes and amortization of investment tax credits			$ (51)	$ 201
Exelon Generation Co L L C [Member] | Certain Distributed Energy Companies [Member]
Property, Plant and Equipment [Line Items]
Equity Method Investment, Other than Temporary Impairment		164
Net income (loss) attributable to noncontrolling interests		96
Deferred income taxes and amortization of investment tax credits		(46)
Income (Loss) from Equity Method Investments		$ (15)
Antelope Valley [Member]
Property, Plant and Equipment [Line Items]
Capacity Of Facility Of Company Owned Solar Distribution Generation Facilities | MW			242
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
Impairment of Long-Lived Assets Held-for-use			$ 0
Generation New England [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	500
Generation New England [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use	$ 500
Midwest Asset Group [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use			0
Midwest Asset Group [Member] | Exelon Generation Co L L C [Member]
Property, Plant and Equipment [Line Items]
Impairment of Long-Lived Assets Held-for-use			$ 0

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Millions	Jun. 05, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		27.50%	15.60%	8.50%	20.70%
Decrease in Unrecognized Tax Benefits is Reasonably Possible		$ 411		$ 411
Tax Adjustments, Settlements, and Unusual Provisions				76
Income Tax Expense (Benefit)		$ 216	$ 172	$ 141	$ 626
Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Effective income tax rate		45.70%	17.40%	7.70%	28.60%
Decrease in Unrecognized Tax Benefits is Reasonably Possible		$ 411		$ 411
Tax Adjustments, Settlements, and Unusual Provisions				73
Income Tax Expense (Benefit)		$ 100	$ 87	41	$ 388
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%
State and Local Jurisdiction [Member]
Income Tax Additional Narrative Information [Line Items]
Increase (Decrease) in Deferred Income Taxes				$ 66	23
State and Local Jurisdiction [Member] | Exelon Generation Co L L C [Member]
Income Tax Additional Narrative Information [Line Items]
Increase (Decrease) in Income Taxes					9
Increase (Decrease) in Deferred Income Taxes				$ (26)	$ 9

Income Taxes - Reconciliation t

Income Taxes - Reconciliation to Effective Tax Rate (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	12.30%	6.40%	9.30%	5.10%
Qualified nuclear decommissioning trust fund income	13.20%	3.20%	3.20%	5.30%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments			2.50%
Amortization of investment tax credit, including deferred taxes on basis difference	(1.40%)	(4.10%)	(1.20%)	(1.90%)
Plant basis differences	(4.30%)	(1.70%)	(4.00%)	(1.60%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(3.00%)	(1.20%)	(2.60%)	(1.00%)
Noncontrolling interests	0.80%	(2.20%)	1.00%	(1.00%)
Excess deferred tax amortization	(10.10%)	(6.50%)	(15.80%)	(6.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	(0.20%)		(5.00%)
Other	(0.80%)	0.70%	0.10%	0.80%
Effective income tax rate	27.50%	15.60%	8.50%	20.70%
Exelon Generation Co L L C [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	(10.30%)	5.20%	0.00%	4.20%
Qualified nuclear decommissioning trust fund income	47.40%	7.10%	10.00%	11.90%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments			0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(4.50%)	(8.90%)	(3.20%)	(4.00%)
Plant basis differences	0.00%	0.00%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(9.20%)	(2.70%)	(7.00%)	(2.10%)
Noncontrolling interests	2.90%	(4.80%)	3.10%	(2.30%)
Excess deferred tax amortization	0.00%	0.00%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	(0.70%)		(15.70%)
Other	(0.90%)	0.50%	(0.50%)	(0.10%)
Effective income tax rate	45.70%	17.40%	7.70%	28.60%
Commonwealth Edison Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	8.10%	8.10%	12.70%	8.20%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments			9.40%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.20%)	(0.30%)	(0.20%)
Plant basis differences	(0.60%)	(1.00%)	(0.90%)	(0.70%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.40%)	0.00%	(0.40%)	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(5.60%)	(9.90%)	(11.80%)	(9.20%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%		0.00%
Other	1.10%	0.40%	2.10%	0.20%
Effective income tax rate	23.40%	18.40%	31.80%	19.30%
PECO Energy Co [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	(6.20%)	(0.30%)	(3.40%)	0.00%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments			0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	0.00%	0.00%	0.00%	0.00%
Plant basis differences	(23.30%)	(7.50%)	(15.90%)	(6.80%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	0.00%	0.00%	0.00%	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(3.80%)	(3.60%)	(3.50%)	(2.90%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%		0.00%
Other	(0.80%)	(0.50%)	(0.50%)	(0.20%)
Effective income tax rate	(13.10%)	9.10%	(2.30%)	11.10%
Baltimore Gas and Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	5.10%	6.30%	5.50%	6.40%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments			0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.10%)	(0.10%)	(0.10%)
Plant basis differences	(1.20%)	(1.10%)	(1.80%)	(1.10%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.80%)	0.00%	(0.40%)	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(10.60%)	(8.00%)	(15.00%)	(7.90%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%		0.00%
Other	(0.30%)	(0.20%)	(0.50%)	0.10%
Effective income tax rate	13.10%	17.90%	8.70%	18.40%
Pepco Holdings LLC [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	5.50%	4.80%	5.00%	4.80%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments			0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.20%)	(0.20%)	(0.20%)
Plant basis differences	(1.50%)	(1.80%)	(2.20%)	(1.80%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.50%)	0.00%	(0.30%)	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(24.90%)	(17.70%)	(45.30%)	(18.60%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%		0.00%
Other	0.10%	0.80%	(0.60%)	0.50%
Effective income tax rate	(0.50%)	6.90%	(22.60%)	5.70%
Potomac Electric Power Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	4.60%	1.90%	4.20%	2.00%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments			0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.10%)	(0.10%)	(0.10%)	(0.10%)
Plant basis differences	(2.10%)	(2.60%)	(2.40%)	(2.30%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.50%)	0.00%	(0.30%)	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(20.00%)	(16.30%)	(29.20%)	(17.30%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%		0.00%
Other	(0.40%)	1.00%	(0.80%)	0.70%
Effective income tax rate	2.50%	4.90%	(7.60%)	4.00%
Delmarva Power and Light Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.60%	6.60%	6.50%	6.70%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments			0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.20%)	(0.20%)	(0.30%)	(0.20%)
Plant basis differences	(0.40%)	(0.60%)	(0.50%)	(0.60%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.50%)	0.00%	(0.20%)	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(23.60%)	(13.50%)	(53.60%)	(15.00%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%		0.00%
Other	0.70%	(0.10%)	(1.10%)	0.20%
Effective income tax rate	3.60%	13.20%	(28.20%)	12.10%
Atlantic City Electric Company [Member]
Effective Income Tax Rate Reconciliation, Percent [Abstract]
U.S. Federal statutory rate	21.00%	21.00%	21.00%	21.00%
Increase (decrease) due to:
State income taxes, net of Federal income tax benefit	6.90%	6.90%	6.80%	6.90%
Qualified nuclear decommissioning trust fund income	0.00%	0.00%	0.00%	0.00%
Effective Income Tax Rate Reconciliation, Deferred Prosecution Agreement payments			0.00%
Amortization of investment tax credit, including deferred taxes on basis difference	(0.30%)	(0.30%)	(0.50%)	(0.30%)
Plant basis differences	(1.30%)	(1.90%)	(3.70%)	(2.00%)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Percent	(0.40%)	0.00%	(0.40%)	0.00%
Noncontrolling interests	0.00%	0.00%	0.00%	0.00%
Excess deferred tax amortization	(36.80%)	(23.30%)	(81.40%)	(23.40%)
Effective Income Tax Rate Reconciliation, Tax Settlement, Percent	0.00%		0.00%
Other	0.60%	0.70%	0.00%	0.00%
Effective income tax rate	(10.30%)	3.10%	(58.20%)	2.20%

Income Taxes - Accounting for U

Income Taxes - Accounting for Uncertainty in Income Taxes (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 125	$ 507
Exelon Generation Co L L C [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	49	441
Pepco Holdings LLC [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	53	48
Atlantic City Electric Company [Member]
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits	$ 16	$ 14

Income Taxes - Settlement of In

Income Taxes - Settlement of Income Tax Audits, Refund Claims, and Litigation (Details) $ in Millions	Sep. 30, 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] | 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] | 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

Allocation of Tax Benefits (Det

Allocation of Tax Benefits (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Exelon Generation Co L L C [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	$ 64	$ 41
Commonwealth Edison Co [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	14	0
PECO Energy Co [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	17	14
Baltimore Gas and Electric Company [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	0	3
Pepco Holdings LLC [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	17	7
Potomac Electric Power Company [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	8	6
Delmarva Power and Light Company [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	6	1
Atlantic City Electric Company [Member] | State and Local Jurisdiction [Member]
Allocation of Tax Benefits [Line Items]
Allocation Of Federal Tax Benefit Under Tax Sharing Agreement	$ 1	$ 0

Retirement Benefits - Narrative

Retirement Benefits - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2020	Sep. 30, 2020
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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Amortization of:
Net periodic benefit cost	$ (15)	$ 2	$ (38)	$ (8)
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	97	89	290	267
Interest cost	190	221	569	663
Expected return on assets	(317)	(306)	(953)	(918)
Amortization of:
Prior service cost (benefit)	1	0	3	0
Actuarial loss	128	104	384	310
Settlement charges	8	7	14	7
Contractual Termination Benefits	0	1	0	1
Net periodic benefit cost	107	116	307	330
Other Postretirement Benefit Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	22	23	67	70
Interest cost	37	47	114	141
Expected return on assets	(41)	(38)	(122)	(115)
Amortization of:
Prior service cost (benefit)	(30)	(45)	(92)	(134)
Actuarial loss	12	11	36	34
Settlement charges	0	0	0	0
Contractual Termination Benefits	0	0	0	0
Net periodic benefit cost	$ 0	$ (2)	$ 3	$ (4)

Retirement Benefits - Allocated

Retirement Benefits - Allocated Portion of Pension and Postretirement Benefit Plan Costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			$ 310	$ 324
Pension and other post retirement benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	$ 107	$ 114	310	326
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			89	98
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)	30	37	89	100
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			85	70
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)	29	23	85	70
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			4	9
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	4	4	9
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			46	45
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	47	47
Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			52	71
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	52	71
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			11	19
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)	4	6	11	19
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			6	11
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)	2	4	6	11
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)			10	12
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	$ 10	$ 12

Retirement Benefits - Defined C

Retirement Benefits - Defined Contribution Savings Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	$ 37	$ 36	$ 104	$ 101
Exelon Generation Co L L C [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	14	14	41	41
Commonwealth Edison Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	9	9	25	26
PECO Energy Co [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	3	2	8	7
Baltimore Gas and Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	4	4	8	9
Pepco Holdings LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	3	4	9	8
Potomac Electric Power Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	1	1	3	2
Delmarva Power and Light Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	1	1	2	2
Atlantic City Electric Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Savings Plan Matching Contributions	$ 0	$ 1	$ 1	$ 1

Derivative Financial Instrume_3

Derivative Financial Instruments - Narrative (Details) MWh in Millions, $ in Millions	1 Months Ended	9 Months Ended
	Jun. 30, 2012MWh	Sep. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Derivative [Line Items]
Derivative, Notional Amount		$ 153	$ 99
Incremental Collateral For Loss Of Investment Grade Credit Rating		1,287	1,509
Derivative, Collateral, Right to Reclaim Cash		288	982
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Derivative, Notional Amount		153	99
Incremental Collateral For Loss Of Investment Grade Credit Rating		1,287	1,509
Derivative, Collateral, Right to Reclaim Cash		288	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		10
Baltimore Gas and Electric Company [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		31
PECO Energy Co [Member]
Derivative [Line Items]
Incremental Collateral For Loss Of Investment Grade Credit Rating		$ 22
Minimum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months		97.00%
Expected Generation Hedged In Year Two		87.00%
Maximum [Member] | Exelon Generation Co L L C [Member]
Derivative [Line Items]
Expected Generation Hedged In Next Twelve Months		100.00%
Expected Generation Hedged In Year Two		90.00%
Not Designated as Hedging Instrument, Economic Hedge [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative, Notional Amount		$ 1,217	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		517	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		$ 171	$ 231

Derivative Financial Instrume_4

Derivative Financial Instruments - Summary of Derivative Fair Value Balances (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Mark-to-market derivative assets, current	$ 472	$ 679
Derivative Asset, Noncurrent	383	508
Mark-to-market derivative liabilities, current	(177)	(247)
Mark-to-market derivative liabilities, noncurrent	(396)	(393)
Margin Deposit Assets	34	511
Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	471	675
Derivative Asset, Noncurrent	383	508
Total mark-to-market derivative assets	854	1,183
Mark-to-market derivative liabilities, current	(168)	(236)
Mark-to-market derivative liabilities, noncurrent	(378)	(380)
Total mark-to-market derivative liabilities	(546)	(616)
Total mark-to-market derivative net assets (liabilities)	308	567
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	471	675
Derivative Asset, Noncurrent	383	508
Mark-to-market derivative liabilities, current	(147)	(215)
Mark-to-market derivative liabilities, noncurrent	(121)	(123)
Margin Deposit Assets	34	511
Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	471	675
Derivative Asset, Noncurrent	383	508
Total mark-to-market derivative assets	854	1,183
Mark-to-market derivative liabilities, current	(138)	(204)
Mark-to-market derivative liabilities, noncurrent	(104)	(111)
Total mark-to-market derivative liabilities	(242)	(315)
Total mark-to-market derivative net assets (liabilities)	612	868
Commonwealth Edison Co [Member]
Derivative [Line Items]
Mark-to-market derivative liabilities, current	(30)	(32)
Mark-to-market derivative liabilities, noncurrent	(274)	(269)
Collateral [Member] | Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	79	287
Derivative Asset, Noncurrent	39	122
Total mark-to-market derivative assets	118	409
Mark-to-market derivative liabilities, current	84	357
Mark-to-market derivative liabilities, noncurrent	49	163
Total mark-to-market derivative liabilities	133	520
Total mark-to-market derivative net assets (liabilities)	251	929
Netting [Member] | Exelon Generation Co L L C [Member] | Commodity Contract [Member]
Derivative [Line Items]
Mark-to-market derivative assets, current	(2,232)	(3,190)
Derivative Asset, Noncurrent	(1,172)	(877)
Total mark-to-market derivative assets	(3,404)	(4,067)
Mark-to-market derivative liabilities, current	2,232	3,190
Mark-to-market derivative liabilities, noncurrent	1,172	877
Total mark-to-market derivative liabilities	3,404	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	2,566	3,506
Derivative Asset, Noncurrent	1,500	1,238
Total mark-to-market derivative assets	4,066	4,744
Mark-to-market derivative liabilities, current	(2,414)	(3,713)
Mark-to-market derivative liabilities, noncurrent	(1,313)	(1,140)
Total mark-to-market derivative liabilities	(3,727)	(4,853)
Total mark-to-market derivative net assets (liabilities)	339	(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	(30)	(32)
Mark-to-market derivative liabilities, noncurrent	(274)	(269)
Total mark-to-market derivative liabilities	(304)	(301)
Total mark-to-market derivative net assets (liabilities)	(304)	(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	58	72
Derivative Asset, Noncurrent	16	25
Total mark-to-market derivative assets	74	97
Mark-to-market derivative liabilities, current	(40)	(38)
Mark-to-market derivative liabilities, noncurrent	(12)	(11)
Total mark-to-market derivative liabilities	(52)	(49)
Total mark-to-market derivative net assets (liabilities)	$ 22	$ 48

Derivative Financial Instrume_5

Derivative Financial Instruments - Summary of Economic Hedges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			$ 448	$ (96)
Exelon Generation Co L L C [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives			448	(102)
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	$ 248	$ 31	462	(62)
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	248	31	462	(62)
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Operating Revenue [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	39	76	238	65
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	39	76	238	65
Not Designated as Hedging Instrument, Economic Hedge [Member] | Commodity Contract [Member] | Purchased Power And Fuel [Member]
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives	209	(45)	224	(127)
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	$ 209	$ (45)	$ 224	$ (127)

Derivative Financial Instrume_6

Derivative Financial Instruments - Summary of Credit Risk Exposure (Details) $ in Millions	Sep. 30, 2020USD ($)
Derivative [Line Items]
Cash Collateral Held	$ 31
Letters Of Credit Held	26
Exelon Generation Co L L C [Member] | Total Exposure Before Credit Collateral [Member]
Derivative [Line Items]
Investment grade	638
Non-investment grade	4
Internally rated - investment grade	168
Internally rated - non-investment grade	110
Total	920
Exelon Generation Co L L C [Member] | Credit Collateral [Member]
Derivative [Line Items]
Investment grade	27
Non-investment grade	0
Internally rated - investment grade	1
Internally rated - non-investment grade	29
Total	57
Exelon Generation Co L L C [Member] | Net Exposure [Member]
Derivative [Line Items]
Investment grade	611
Non-investment grade	4
Internally rated - investment grade	167
Internally rated - non-investment grade	81
Total	863
Financial institutions	26
Investor-owned utilities, marketers and power producers	650
Energy Cooperatives And Municipalities	142
Other	45
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	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Liability	$ (750)	$ (956)
Offsetting Fair Value of In-the-Money Contracts Under Master Netting Agreements	535	649
Derivative liabilities, fair value	$ 215	$ 307

Derivative Financial Instrume_8

Derivative Financial Instruments Derivative Financial Instruments - Summary of Cash Collateral and Letters of Credit (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Collateral, Right to Reclaim Cash	$ 288	$ 982
Derivative, Collateral, Right to Reclaim Securities	212	264
Derivative, Collateral, Obligation to Return Cash	68	103
Derivative, Collateral, Obligation to Return Securities	74	112
Incremental Collateral For Loss Of Investment Grade Credit Rating	1,287	1,509
Exelon Generation Co L L C [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Collateral, Right to Reclaim Cash	288	982
Derivative, Collateral, Right to Reclaim Securities	212	264
Derivative, Collateral, Obligation to Return Cash	68	103
Derivative, Collateral, Obligation to Return Securities	74	112
Incremental Collateral For Loss Of Investment Grade Credit Rating	$ 1,287	$ 1,509

Debt and Credit Agreements - Na

Debt and Credit Agreements - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
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
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	470
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	470
ExGenRenewablesIVNov2024 [Member] | Non Recourse Debt [Member]
Debt Instrument [Line Items]
Non-Recourse Debt	710
Long-term Debt	850
ExGenRenewablesIVNov2024 [Member] | Exelon Generation Co L L C [Member] | Non Recourse Debt [Member]
Debt Instrument [Line Items]
Non-Recourse Debt	710
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
ExGenBilat100May152020 [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	100
Line of Credit, Current	$ 40
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] | Short-term Debt [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.50%
London Interbank Offered Rate (LIBOR) [Member] | ShortTermDebt300 [Member] [Member] | Exelon Generation Co L L C [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate Terms	LIBOR plus 0.75%
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	$ 4,900

Debt and Credit Agreements - Co

Debt and Credit Agreements - Commercial Paper Borrowings (Details) - Commercial Paper [Member] - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Short-term Debt [Line Items]
Commercial Paper	$ 141	$ 870
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.16%	2.25%
Parent Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 136
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	1.92%
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 320
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	1.84%
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 141	$ 130
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.16%	2.38%
PECO Energy Co [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 0
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	0.00%
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 76
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	2.46%
Pepco Holdings LLC [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 208
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 82
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	2.56%
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 56
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	2.02%
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Commercial Paper	$ 0	$ 70
Short-term Debt, Weighted Average Interest Rate, at Point in Time	0.00%	2.43%

Debt and Credit Agreements - Is

Debt and Credit Agreements - Issuance of Long-Term Debt (Details) $ in Millions	Sep. 30, 2020USD ($)
Parent Company [Member] | Note405Apr2030 [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Interest Rate	4.05%
Debt Instrument, Face Amount	$ 1,250
Parent Company [Member] | Note470Apr2050 [Member] | Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Interest Rate	4.70%
Debt Instrument, Face Amount	$ 750
Exelon Generation Co L L C [Member] | SN325June2025 [Member] | Energy Efficiency Project Financing [Member]
Debt Instrument [Line Items]
Interest Rate	3.25%
Debt Instrument, Face Amount	$ 900
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	$ 3
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	$ 2
Commonwealth Edison Co [Member] | FMB220Mar2030 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.20%
Debt Instrument, Face Amount	$ 350
Commonwealth Edison Co [Member] | FMB300March2050 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.00%
Debt Instrument, Face Amount	$ 650
PECO Energy Co [Member] | FMB280June2050 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.80%
Debt Instrument, Face Amount	$ 350
Baltimore Gas and Electric Company [Member] | SN290June2050 [Member] | Energy Efficiency Project Financing [Member]
Debt Instrument [Line Items]
Interest Rate	2.90%
Debt Instrument, Face Amount	$ 400
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
Delmarva Power and Light Company [Member] | FMB253June2030 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	2.53%
Debt Instrument, Face Amount	$ 100
Delmarva Power and Light Company [Member] | Bonds105July2020 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	1.05%
Debt Instrument, Face Amount	$ 78
Atlantic City Electric Company [Member] | Bonds225June2029 [Member] | Tax-exempt Money Market Funds [Member]
Debt Instrument [Line Items]
Interest Rate	2.25%
Debt Instrument, Face Amount	$ 23
Atlantic City Electric Company [Member] | FMB324June2050 [Member] | First Mortgage Bonds [Member]
Debt Instrument [Line Items]
Interest Rate	3.24%
Debt Instrument, Face Amount	$ 100

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Narrative (Details) $ in Millions	Sep. 30, 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	52
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	52
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	119
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	119
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	299
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	299
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	395
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	$ 395

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities - Fair Value of Financial Liabilities Recorded at Amortized Cost (Details) - USD ($) $ in Millions	Sep. 30, 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	1,207	1,199
Reported Value Measurement [Member]
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Long-term debt (including amounts due within one year)	37,589	36,039
Long-term debt to financing trust	390	390
Spent Nuclear Fuel Obligation, Noncurrent	1,207	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)	44,053	40,033
Long-term debt to financing trust	467	428
Spent Nuclear Fuel Obligation, Noncurrent	1,042	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)	40,816	37,453
Long-term debt to financing trust	0	0
Spent Nuclear Fuel Obligation, Noncurrent	1,042	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)	3,237	2,580
Long-term debt to financing trust	467	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	1,207	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)	6,756	7,974
Spent Nuclear Fuel Obligation, Noncurrent	1,207	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)	7,651	8,670
Spent Nuclear Fuel Obligation, Noncurrent	1,042	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)	6,250	7,304
Spent Nuclear Fuel Obligation, Noncurrent	1,042	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)	1,401	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)	8,981	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)	10,970	9,848
Long-term debt to financing trust	246	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)	10,970	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	246	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)	3,753	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)	4,548	3,918
Long-term debt to financing trust	221	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)	4,498	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	221	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)	3,664	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)	4,263	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)	4,263	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)	7,020	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)	7,868	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)	6,082	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)	1,786	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)	3,164	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)	4,082	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)	3,343	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)	739	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)	1,676	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)	1,912	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)	1,463	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)	449	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)	1,417	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)	1,615	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)	1,017	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)	$ 598	$ 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	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)	$ 177	$ 247
Derivative Liability, Noncurrent	396	393
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	1	2
Derivative Asset, Notional Amount	658	724
Margin Deposit Assets	34	511
Derivative, Notional Amount	153	99
Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	677	373
Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	116	110
Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	137	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	208	147
Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	1,687	639
Deferred purchase price	732
Assets, Fair Value Disclosure	17,303	15,584
Deferred Compensation Liability, Current and Noncurrent	(135)	(147)
Total Liabilities	(681)	(763)
Fair Value, Net Asset (Liability)	16,622	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	(546)	(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	(4,031)	(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	(52)	(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	3,537	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	13,755	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	404	452
Fair Value, Recurring [Member] | Equity Securities [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	6,509	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	4,982	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	1,796	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	1,980	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	52	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	104	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	1,050	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	771	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	439	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	650	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	275	262
Fair Value, Recurring [Member] | Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	58	50
Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	88	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	118	119
Fair Value, Recurring [Member] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	854	1,183
Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	4,066	4,744
Fair Value, Recurring [Member] | Proprietary Trading [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	74	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	(3,286)	(3,658)
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	43	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	1,687	639
Deferred purchase price	0
Assets, Fair Value Disclosure	7,454	6,156
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(1)	0
Fair Value, Net Asset (Liability)	7,453	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	(1)	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	(700)	(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	699	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	5,501	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	313	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	3,345	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	1,843	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	1,843	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	146	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	58	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	88	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] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	120	(140)
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	776	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	(656)	(908)
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	114	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
Deferred purchase price	732
Assets, Fair Value Disclosure	4,741	4,061
Deferred Compensation Liability, Current and Noncurrent	(135)	(147)
Total Liabilities	(155)	(322)
Fair Value, Net Asset (Liability)	4,586	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	(20)	(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	(1,692)	(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	(36)	(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	1,708	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	3,734	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	91	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	1,794	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	1,849	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	1,516	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	137	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	52	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	104	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	40	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	95	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	84	78
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	180	366
Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,737	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	37	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	(1,594)	(2,162)
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	94	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
Deferred purchase price	0
Assets, Fair Value Disclosure	1,106	1,509
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(525)	(441)
Fair Value, Net Asset (Liability)	581	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	(525)	(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	(1,639)	(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	(16)	(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	1,130	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	518	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	280	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	280	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	238	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	34	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	34	41
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	554	957
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,553	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	37	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	(1,036)	(588)
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
Deferred purchase price	0
Assets, Fair Value Disclosure	4,002	3,858
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	4,002	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	4,002	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	1,370	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	1,010	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	1,010	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	533	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	439	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	650	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] | Commodity Derivative Assets [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] | 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
Exelon Generation Co L L C [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	(215)	(307)
Mark-to-market derivative liabilities (current liabilities)	147	215
Derivative Liability, Noncurrent	121	123
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	1	2
Derivative Asset, Notional Amount	658	724
Margin Deposit Assets	34	511
Derivative, Notional Amount	153	99
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	408	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	45	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	208	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	270	214
Deferred purchase price	732
Assets, Fair Value Disclosure	15,670	14,951
Deferred Compensation Liability, Current and Noncurrent	(37)	(41)
Total Liabilities	(279)	(356)
Fair Value, Net Asset (Liability)	15,391	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	(242)	(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	(3,727)	(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	(52)	(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	3,537	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	13,755	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	404	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	6,509	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	4,982	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	1,796	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	1,980	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	52	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	104	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	1,050	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	771	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	439	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	650	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	59	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	28	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	27	25
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	854	1,183
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	4,066	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	74	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	(3,286)	(3,658)
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	43	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	270	214
Deferred purchase price	0
Assets, Fair Value Disclosure	5,923	5,629
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(1)	0
Fair Value, Net Asset (Liability)	5,922	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	(1)	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	(700)	(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	699	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	5,501	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	313	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	3,345	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	1,843	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	1,843	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	32	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	28	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] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	120	(140)
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	776	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	(656)	(908)
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	114	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
Deferred purchase price	732
Assets, Fair Value Disclosure	4,673	3,996
Deferred Compensation Liability, Current and Noncurrent	(37)	(41)
Total Liabilities	(57)	(216)
Fair Value, Net Asset (Liability)	4,616	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	(20)	(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	(1,692)	(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	(36)	(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	1,708	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	3,734	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	91	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	1,794	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	1,849	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	1,516	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	137	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	52	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	104	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	40	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	27	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	27	25
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	180	366
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,737	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	37	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	(1,594)	(2,162)
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	94	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
Deferred purchase price	0
Assets, Fair Value Disclosure	1,072	1,468
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(221)	(140)
Fair Value, Net Asset (Liability)	851	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	(221)	(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	(1,335)	(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	(16)	(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	1,130	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	518	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	280	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	280	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	238	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] | Commodity Derivative Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	554	957
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Economic Hedging Instrument [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Derivative Asset	1,553	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	37	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	(1,036)	(588)
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
Deferred purchase price	0
Assets, Fair Value Disclosure	4,002	3,858
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	4,002	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	4,002	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	1,370	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	1,010	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	1,010	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	533	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	439	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	650	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] | 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 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
Commonwealth Edison Co [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Mark-to-market derivative liabilities (current liabilities)	30	32
Derivative Liability, Noncurrent	274	269
Commonwealth Edison Co [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	76	90
Commonwealth Edison Co [Member] | Restricted cash member [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	36	33
Commonwealth Edison Co [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	127	163
Commonwealth Edison Co [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	396	280
Assets, Fair Value Disclosure	396	280
Total mark-to-market derivative liabilities	(304)	(301)
Deferred Compensation Liability, Current and Noncurrent	(7)	(8)
Total Liabilities	(311)	(309)
Fair Value, Net Asset (Liability)	85	(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	396	280
Assets, Fair Value Disclosure	396	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)	396	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	(304)	(301)
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	(304)	(301)
Fair Value, Net Asset (Liability)	(304)	(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	65	12
PECO Energy Co [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	184	15
Assets, Fair Value Disclosure	206	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)	198	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	22	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	9	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	13	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	184	15
Assets, Fair Value Disclosure	193	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)	193	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	9	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	9	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	13	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)	5	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	13	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	13	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	28	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	298	0
Assets, Fair Value Disclosure	307	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)	302	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	9	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	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	298	0
Assets, Fair Value Disclosure	307	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)	307	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	9	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	9	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	0	0
Total mark-to-market derivative liabilities	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Rabbi Trust Investments [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | Mutual Funds [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Baltimore Gas and Electric Company [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member] | 6311 Life Insurance [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Investments, Fair Value Disclosure	0	0
Pepco Holdings LLC [Member] | Cash and Cash Equivalents [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	78	57
Pepco Holdings LLC [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	10	14
Pepco Holdings LLC [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	166	124
Assets, Fair Value Disclosure	303	259
Deferred Compensation Liability, Current and Noncurrent	(17)	(19)
Total Liabilities	(17)	(19)
Fair Value, Net Asset (Liability)	286	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	137	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	52	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	14	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	60	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	166	124
Assets, Fair Value Disclosure	232	182
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	232	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	66	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	52	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	14	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	37	36
Deferred Compensation Liability, Current and Noncurrent	(17)	(19)
Total Liabilities	(17)	(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	37	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	26	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	34	41
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	34	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	34	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	34	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	46	29
Potomac Electric Power Company [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	112	34
Assets, Fair Value Disclosure	225	144
Deferred Compensation Liability, Current and Noncurrent	(2)	(2)
Total Liabilities	(2)	(2)
Fair Value, Net Asset (Liability)	223	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	113	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	51	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	2	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	60	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	112	34
Assets, Fair Value Disclosure	163	77
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	163	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	51	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	51	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	28	26
Deferred Compensation Liability, Current and Noncurrent	(2)	(2)
Total Liabilities	(2)	(2)
Fair Value, Net Asset (Liability)	26	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	28	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	2	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	26	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	34	41
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	34	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	34	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	34	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	9	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	17	0
Assets, Fair Value Disclosure	17	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	17	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	17	0
Assets, Fair Value Disclosure	17	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	17	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	13	12
Atlantic City Electric Company [Member] | Other Assets [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	10	14
Atlantic City Electric Company [Member] | Fair Value, Recurring [Member]
Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]
Cash equivalents	14	16
Assets, Fair Value Disclosure	14	16
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	14	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	14	16
Assets, Fair Value Disclosure	14	16
Deferred Compensation Liability, Current and Noncurrent	0	0
Total Liabilities	0	0
Fair Value, Net Asset (Liability)	14	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	121	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	$ 121	$ 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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 883	$ 1,179	$ 1,068	$ 907
Total realized / unrealized gains (losses)
Included in net income	(327)	(171)	(483)	(125)
Included in noncurrent payables to affiliates	0	0	0	0
Included in regulatory assets	32	4	14	1
Change in collateral	(79)	41	(120)	227
Purchases, sales, issuances and settlements
Purchases	66	53	136	163
Sales	(3)	(22)	(27)	(23)
Settlements	0	(18)	(15)	(88)
Transfers into Level 3		1	(5)	5
Transfers out of Level 3	9	(11)	13	(11)
Ending Balance	581	1,056	581	1,056
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(222)	(18)	(107)	173
Fair Value, Inputs, Level 3 [Member] | Consolidation, Eliminations [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	0	0	0	0
Total realized / unrealized gains (losses)
Included in net income	0	0	0	0
Included in noncurrent payables to affiliates	(18)	(11)	(17)	(32)
Included in regulatory assets	18	11	17	32
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3		0	0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	0	0	0	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0	0	0
Exelon Generation Co L L C [Member]
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings	105	153	376	298
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	1,158	1,412	1,328	1,118
Total realized / unrealized gains (losses)
Included in net income	(315)	(171)	(473)	(127)
Included in noncurrent payables to affiliates	18	11	17	32
Included in regulatory assets	0	0	0	0
Change in collateral	(79)	41	(120)	227
Purchases, sales, issuances and settlements
Purchases	66	53	136	163
Sales	(3)	(22)	(27)	(23)
Settlements	(3)	(18)	(18)	(88)
Transfers into Level 3		1	(5)	5
Transfers out of Level 3	9	(11)	13	(11)
Ending Balance	851	1,296	851	1,296
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(210)	(18)	(97)	171
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	499	539	511	543
Total realized / unrealized gains (losses)
Included in net income	3	2	1	5
Included in noncurrent payables to affiliates	18	11	17	32
Included in regulatory assets	0	0	0	0
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	1	1	6	43
Sales	0	(21)	0	(21)
Settlements	(3)	(18)	(18)	(88)
Transfers into Level 3		0	1	0
Transfers out of Level 3	0	0	0	0
Ending Balance	518	514	518	514
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	3	2	1	5
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member] | Derivative [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	659	873	817	575
Total realized / unrealized gains (losses)
Included in net income	(318)	(173)	(474)	(132)
Included in noncurrent payables to affiliates	0	0	0	0
Included in regulatory assets	0	0	0	0
Change in collateral	(79)	41	(120)	227
Purchases, sales, issuances and settlements
Purchases	65	52	130	120
Sales	(3)	(1)	(27)	(2)
Settlements	0	0	0	0
Transfers into Level 3		1	(6)	5
Transfers out of Level 3	9	(11)	13	(11)
Ending Balance	333	782	333	782
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(213)	(20)	(98)	166
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)	5	4	23	17
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	(318)	(273)	(301)	(249)
Total realized / unrealized gains (losses)
Included in net income	0	0	0	0
Included in noncurrent payables to affiliates	0	0	0	0
Included in regulatory assets	14	(7)	(3)	(31)
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3		0	0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	(304)	(280)	(304)	(280)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	0	0	0	0
Footnotes To Fair Value Assets And Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Abstract]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Inputs Reconciliation, Period Increase (Decrease)	(9)	(7)	(26)	(31)
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	43	40	41	38
Total realized / unrealized gains (losses)
Included in net income	(12)	0	(10)	2
Included in noncurrent payables to affiliates	0	0	0	0
Included in regulatory assets	0	0	0	0
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	3	0	3	0
Transfers into Level 3		0	0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	34	40	34	40
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(12)	0	(10)	2
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	43	40	41	38
Total realized / unrealized gains (losses)
Included in net income	(12)	0	(10)	2
Included in noncurrent payables to affiliates	0	0	0	0
Included in regulatory assets	0	0	0	0
Change in collateral	0	0	0	0
Purchases, sales, issuances and settlements
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	3	0	3	0
Transfers into Level 3		0	0	0
Transfers out of Level 3	0	0	0	0
Ending Balance	34	40	34	40
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ (12)	$ 0	$ (10)	$ 2

Fair Value of Financial Asset_7

Fair Value of Financial Assets and Liabilities - Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 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	$ 327	$ 171	$ 483	$ 125
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(222)	(18)	(107)	173
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	(305)	(25)	(370)	122
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(216)	99	(50)	368
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	(13)	(148)	(104)	(254)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	3	(119)	(48)	(202)
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	(12)	0	(10)	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(12)	0	(10)	2
Other, net [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	2	0	5
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	3	2	1	5
Exelon Generation Co L L C [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	315	171	473	127
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(210)	(18)	(97)	171
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	(305)	(25)	(370)	122
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(216)	99	(50)	368
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	(13)	(148)	(104)	(254)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	3	(119)	(48)	(202)
Exelon Generation Co L L C [Member] | Other, net [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	0	2	0	5
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	3	2	1	5
Pepco Holdings LLC [Member] | Operating and Maintenance [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	(12)	0	(10)	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	(12)	0	(10)	2
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	(12)	0	(10)	0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ (12)	$ 0	$ (10)	$ 2

Fair Value of Financial Asset_8

Fair Value of Financial Assets and Liabilities - Fair Value Inputs Assets Quantitative Information (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Fair Value, Inputs, Level 3 [Member]
Derivatives Fair Value Footnotes [Abstract]
Cash Collateral Posted	$ 94,000,000	$ 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	218,000,000	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	$ (304,000,000)	$ (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	9	9
Forward gas price assets	1.84	0.83
Forward heat rate	800.00%	900.00%
Derivative Asset (Liability) Net, Measurement Input	0.03	0.03
Fair Value Inputs Renewable Factor	91.00%	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	113	180
Forward gas price assets	4.69	10.72
Forward heat rate	900.00%	1000.00%
Derivative Asset (Liability) Net, Measurement Input	0.08	0.07
Fair Value Inputs Renewable Factor	123.00%	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	29	29
Forward gas price assets	2.77	2.55
Forward heat rate	885.00%	968.00%
Derivative Asset (Liability) Net, Measurement Input	0.0493	0.0495
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	0.10	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	1.60	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	0.57	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	$ 21,000,000	$ 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	9	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	115	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	$ (215,000,000)	$ (307,000,000)
Exelon Generation Co L L C [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives Fair Value Footnotes [Abstract]
Cash Collateral Posted	94,000,000	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	$ 218,000,000	$ 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	9	9
Forward gas price assets	1.84	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	113	180
Forward gas price assets	4.69	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	29	29
Forward gas price assets	2.77	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	0.10	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	1.60	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	0.57	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	$ 21,000,000	$ 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	9	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	115	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	$ (304,000,000)	$ (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	800.00%	900.00%
Derivative Asset (Liability) Net, Measurement Input	0.03	0.03
Fair Value Inputs Renewable Factor	91.00%	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	900.00%	1000.00%
Derivative Asset (Liability) Net, Measurement Input	0.08	0.07
Fair Value Inputs Renewable Factor	123.00%	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	885.00%	968.00%
Derivative Asset (Liability) Net, Measurement Input	0.0493	0.0495
Fair Value Inputs Renewable Factor	99.00%	99.00%

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Millions	Oct. 30, 2020USD ($)	Aug. 31, 2020USD ($)	Mar. 23, 2016USD ($)MW	Sep. 30, 2020USD ($)MGPSiteOpen_claim	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Mar. 31, 2018MW	Sep. 30, 2020USD ($)MGPSiteOpen_claimMW	Sep. 30, 2019MW	Dec. 31, 2022MW	Dec. 31, 2019USD ($)
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment				$ 2,924							$ 2,924
Accrual for Environmental Loss Contingencies, Gross				494							494			$ 478
Liability for Asbestos and Environmental Claims, Gross				91							91			83
Exelon Generation Co L L C [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment				2,359							2,359
Accrual for Environmental Loss Contingencies, Gross				125							125			105
Liability for Asbestos and Environmental Claims, Gross				91							91			83
Contributions from parent				64
Commonwealth Edison Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment				$ 223							$ 223
Mgp Site Contingency Monitoring Count | MGPSite				21							21
Accrual for Environmental Loss Contingencies, Gross				$ 299							$ 299			304
Deferred Prosecution Agreement payments				200							200			0
Estimated Litigation Liability, Current, Due within 30 days				100							100
Estimated Litigation Liability, Current, Due within 90 days				100							100
Contributions from parent				239	$ 124	$ 125	$ 63	$ 61	$ 63
Increase in Restricted Cash				100
Commonwealth Edison Co [Member] | Deferred Prosecution Agreement Payments [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Deferred Prosecution Agreement payments				200							200
Contributions from parent		$ 100
PECO Energy Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment				$ 180							$ 180
Mgp Site Contingency Monitoring Count | MGPSite				8							8
Accrual for Environmental Loss Contingencies, Gross				$ 23							$ 23			19
Contributions from parent				17		231	29		145
Baltimore Gas and Electric Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment				$ 5							$ 5
Mgp Site Contingency Monitoring Count | MGPSite				4							4
Accrual for Environmental Loss Contingencies, Gross				$ 2							$ 2			2
Contributions from parent				258	26		$ 104
Pepco Holdings LLC [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment				49							49
Accrual for Environmental Loss Contingencies, Gross				45							45			48
Contributions from parent				135	215	144		264	19
Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment				23							23
Accrual for Environmental Loss Contingencies, Gross				43							43			46
Contributions from parent				125		137		$ 115	$ 14
Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment				$ 16							$ 16
Mgp Site Contingency Count | MGPSite				1							1
Accrual for Environmental Loss Contingencies, Gross				$ 1							$ 1			$ 1
Contributions from parent				6	$ 100	$ 6
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							$ 27
Open Asbestos Related Personal Injury Claims | Open_claim				274							274
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				$ 64							$ 64
Pepco Holdings Inc [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment				513							513
Pepco Holdings Inc [Member] | Pepco Holdings LLC [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment				320							320
Pepco Holdings Inc [Member] | Potomac Electric Power Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment				120							120
Pepco Holdings Inc [Member] | Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Other Commitment				89							89
West Lake [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Accrual for Environmental Loss Contingencies, Gross				280							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				30							30
Accrual for Environmental Loss Contingencies, Component Amount				90							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			$ 135	118							$ 118
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				118							$ 118
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] | Commonwealth Edison Co [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Increase in Restricted Cash	$ 100
Subsequent Event [Member] | Commonwealth Edison Co [Member] | Deferred Prosecution Agreement Payments [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Deferred Prosecution Agreement payments				$ 200							$ 200
Contributions from parent	$ 100
Subsequent Event [Member] | Wind Assets [Member] | Pepco Holdings Inc [Member] | Delmarva Power and Light Company [Member]
Commitments And Contingencies Additional Narrative Information [Line Items]
Purchase Commitment | MW													40

Commitments and Contingencies_3

Commitments and Contingencies - Merger Commitment (Details) $ in Millions	Sep. 30, 2020USD ($)
Other Commitments [Line Items]
Other Commitment	$ 2,924
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	49
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	23
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	16
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	10
Pepco Holdings Inc [Member]
Other Commitments [Line Items]
Other Commitment	513
Pepco Holdings Inc [Member] | Remaining commitment
Other Commitments [Line Items]
Other Commitment	87
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	69
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	57
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	7
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	Sep. 30, 2020USD ($)
Other Commitments [Line Items]
Other Commitment	$ 2,924
Other Commitment, to be Paid, Remainder of Fiscal Year	612
Other Commitment, to be Paid, Year Two	1,881
Other Commitment, to be Paid, Year Three	30
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five	6
Other Commitment, to be Paid, after Year Five	392
Guarantor Obligations, Maximum Exposure, Undiscounted	74
Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,462
Other Commitment, to be Paid, Remainder of Fiscal Year	224
Other Commitment, to be Paid, Year Two	1,238
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Surety Bonds
Other Commitments [Line Items]
Other Commitment	1,056
Other Commitment, to be Paid, Remainder of Fiscal Year	388
Other Commitment, to be Paid, Year Two	641
Other Commitment, to be Paid, Year Three	27
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	378
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	378
Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	28
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	2
Other Commitment, to be Paid, Year Three	3
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five	6
Other Commitment, to be Paid, after Year Five	14
Exelon Generation Co L L C [Member]
Other Commitments [Line Items]
Other Commitment	2,359
Other Commitment, to be Paid, Remainder of Fiscal Year	594
Other Commitment, to be Paid, Year Two	1,738
Other Commitment, to be Paid, Year Three	27
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Exelon Generation Co L L C [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	1,447
Other Commitment, to be Paid, Remainder of Fiscal Year	220
Other Commitment, to be Paid, Year Two	1,227
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Exelon Generation Co L L C [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	912
Other Commitment, to be Paid, Remainder of Fiscal Year	374
Other Commitment, to be Paid, Year Two	511
Other Commitment, to be Paid, Year Three	27
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Commonwealth Edison Co [Member]
Other Commitments [Line Items]
Other Commitment	223
Other Commitment, to be Paid, Remainder of Fiscal Year	5
Other Commitment, to be Paid, Year Two	18
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	200
Commonwealth Edison Co [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	7
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	7
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Commonwealth Edison Co [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	16
Other Commitment, to be Paid, Remainder of Fiscal Year	5
Other Commitment, to be Paid, Year Two	11
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Commonwealth Edison Co [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	200
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	200
PECO Energy Co [Member]
Other Commitments [Line Items]
Other Commitment	180
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	2
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	178
PECO Energy Co [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	2
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	2
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
PECO Energy Co [Member] | Financing trust guarantees
Other Commitments [Line Items]
Other Commitment	178
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	178
Baltimore Gas and Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	5
Other Commitment, to be Paid, Remainder of Fiscal Year	3
Other Commitment, to be Paid, Year Two	2
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Baltimore Gas and Electric Company [Member] | Letters of Credit
Other Commitments [Line Items]
Other Commitment	2
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Baltimore Gas and Electric Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	3
Other Commitment, to be Paid, Remainder of Fiscal Year	1
Other Commitment, to be Paid, Year Two	2
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Pepco Holdings LLC [Member]
Other Commitments [Line Items]
Other Commitment	49
Other Commitment, to be Paid, Remainder of Fiscal Year	3
Other Commitment, to be Paid, Year Two	20
Other Commitment, to be Paid, Year Three	3
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five	6
Other Commitment, to be Paid, after Year Five	14
Guarantor Obligations, Maximum Exposure, Undiscounted	74
Pepco Holdings LLC [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	21
Other Commitment, to be Paid, Remainder of Fiscal Year	3
Other Commitment, to be Paid, Year Two	18
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Pepco Holdings LLC [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	28
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	2
Other Commitment, to be Paid, Year Three	3
Other Commitment, to be Paid, Year Four	3
Other Commitment, to be Paid, Year Five	6
Other Commitment, to be Paid, after Year Five	14
Potomac Electric Power Company [Member]
Other Commitments [Line Items]
Other Commitment	23
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	14
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five	2
Other Commitment, to be Paid, after Year Five	5
Guarantor Obligations, Maximum Exposure, Undiscounted	25
Potomac Electric Power Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	14
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	14
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Potomac Electric Power Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	9
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	0
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five	2
Other Commitment, to be Paid, after Year Five	5
Delmarva Power and Light Company [Member]
Other Commitments [Line Items]
Other Commitment	16
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five	3
Other Commitment, to be Paid, after Year Five	6
Guarantor Obligations, Maximum Exposure, Undiscounted	31
Delmarva Power and Light Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	4
Other Commitment, to be Paid, Remainder of Fiscal Year	2
Other Commitment, to be Paid, Year Two	2
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Delmarva Power and Light Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	12
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five	3
Other Commitment, to be Paid, after Year Five	6
Atlantic City Electric Company [Member]
Other Commitments [Line Items]
Other Commitment	10
Other Commitment, to be Paid, Remainder of Fiscal Year	1
Other Commitment, to be Paid, Year Two	3
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five	1
Other Commitment, to be Paid, after Year Five	3
Guarantor Obligations, Maximum Exposure, Undiscounted	18
Atlantic City Electric Company [Member] | Surety Bonds
Other Commitments [Line Items]
Other Commitment	3
Other Commitment, to be Paid, Remainder of Fiscal Year	1
Other Commitment, to be Paid, Year Two	2
Other Commitment, to be Paid, Year Three	0
Other Commitment, to be Paid, Year Four	0
Other Commitment, to be Paid, Year Five	0
Other Commitment, to be Paid, after Year Five	0
Atlantic City Electric Company [Member] | Guaranteed lease residual values
Other Commitments [Line Items]
Other Commitment	7
Other Commitment, to be Paid, Remainder of Fiscal Year	0
Other Commitment, to be Paid, Year Two	1
Other Commitment, to be Paid, Year Three	1
Other Commitment, to be Paid, Year Four	1
Other Commitment, to be Paid, Year Five	1
Other Commitment, to be Paid, after Year Five	$ 3
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	Sep. 30, 2020	Dec. 31, 2019
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	$ 494	$ 478
Exelon Generation Co L L C [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	125	105
Commonwealth Edison Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	299	304
PECO Energy Co [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	23	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	45	48
Potomac Electric Power Company [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Total environmental investigation and remediation reserve	43	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	320	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	298	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	22	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						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	$ 34,871	$ 34,616	$ 34,573	$ 33,907	$ 33,704	$ 33,070	$ 34,573	$ 33,070
Other comprehensive income	28			30			90	33
Ending balance	35,103	34,871	34,616	34,352	33,907	33,704	35,103	34,352
Gains (Losses) on Cash Flow Hedges
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(3)		(2)	(2)		(2)	(2)	(2)
OCI before reclassifications	(1)			0			(2)	0
Amounts reclassified from AOCI	0			0			0	0
Other comprehensive income	(1)			0			(2)	0
Ending balance	(4)	(3)		(2)	(2)		(4)	(2)
Pension and Non-Pension Postretirement Benefit Plan Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(3,096)		(3,165)	(2,957)		(2,960)	(3,165)	(2,960)
OCI before reclassifications	(13)			6			(17)	(32)
Amounts reclassified from AOCI	39			21			112	62
Other comprehensive income	26			27			95	30
Ending balance	(3,070)	(3,096)		(2,930)	(2,957)		(3,070)	(2,930)
Foreign Currency Items
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(33)		(27)	(29)		(33)	(27)	(33)
OCI before reclassifications	3			(2)			(3)	2
Amounts reclassified from AOCI	0			0			0	0
Other comprehensive income	3			(2)			(3)	2
Ending balance	(30)	(33)		(31)	(29)		(30)	(31)
AOCI of Investments in Unconsolidated Affiliates
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance				(2)		0		0
OCI before reclassifications				0				(2)
Amounts reclassified from AOCI				2				2
Other comprehensive income				2				0
Ending balance				0	(2)			0
Total
Movement in Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(3,132)	(3,173)	(3,194)	(2,990)	(3,012)	(2,995)	(3,194)	(2,995)
OCI before reclassifications	(11)			4			(22)	(32)
Amounts reclassified from AOCI	39			23			112	64
Other comprehensive income	28	41	21	27	22	(17)	90	32
Ending balance	$ (3,104)	$ (3,132)	$ (3,173)	$ (2,963)	$ (2,990)	$ (3,012)	$ (3,104)	$ (2,963)

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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Prior service costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ 4	$ 6	$ 12	$ 18
Actuarial losses
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	(16)	(13)	(50)	(39)
Pension and Non-Pension Postretirement Benefit Plan Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Tax	$ 3	$ 0	$ 6	$ 14

Variable Interest Entities - Na

Variable Interest Entities - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Apr. 01, 2014
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 74
Exelon Generation Co L L C [Member] | Distributed Energy Company
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		90.00%
Exelon Generation Co L L C [Member] | VIE Distributed Energy Company
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		90.00%
CENG [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		50.01%
EGRP [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		51.00%
Antelope Valley [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		100.00%
Distributed Energy Company | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		31.00%
NER | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		100.00%
Variable Interest Entity, Primary Beneficiary [Member] | CENG [Member] | Payment Guarantee [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			$ 245
Variable Interest Entity, Primary Beneficiary [Member] | CENG [Member] | Financial Guarantee [Member]
Variable Interest Entity [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			$ 165
Variable Interest Entity, Primary Beneficiary [Member] | CENG [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		49.99%
Guarantor Obligations, Current Carrying Value	$ 688
Variable Interest Entity, Primary Beneficiary [Member] | EGRP [Member] | Exelon Generation Co L L C [Member] | Wind project entities [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		100.00%
Variable Interest Entity, Primary Beneficiary [Member] | EGRP [Member] | Exelon Generation Co L L C [Member] | Solar project entities [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage		100.00%

Variable Interest Entities - As

Variable Interest Entities - Assets and Liabilities of Consolidated VIES (Details) - USD ($) $ in Millions		Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 1,858	$ 587	$ 1,683	$ 1,349
Restricted cash and cash equivalents		485	358	309	247
Accounts receivable, net
Customer		2,792	4,592
Unamortized energy contract assets		41	47
Inventory, net
Materials and supplies		1,405	1,456
Other current assets		2,277	1,253
Total current assets		12,312	12,037
Property, plant and equipment, net		82,561	80,233
NDT funds		13,432	13,190
Unamortized energy contract assets		308	336
Other Assets, Noncurrent		3,165	3,197
Total assets	[1]	127,767	124,977
Long-term debt due within one year		2,077	4,710
Accounts payable		3,182	3,560
Accrued expenses		1,879	1,981
Unamortized energy contract liabilities		107	132
Other		1,475	1,331
Total current liabilities		11,262	14,185
Long-term debt		35,512	31,329
Asset retirement obligations, noncurrent		11,989	10,846
Unamortized energy contract liabilities		266	338
Other		3,313	3,064
Total liabilities	[1]	92,664	90,404
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		623	303	1,019	750
Restricted cash and cash equivalents		100	146	126	153
Accounts receivable, net
Customer		1,056	2,893
Unamortized energy contract assets		41	47
Inventory, net
Materials and supplies		971	1,026
Other current assets		1,387	605
Total current assets		5,883	7,076
Property, plant and equipment, net		23,709	24,193
NDT funds		13,432	13,190
Unamortized energy contract assets		308	336
Other Assets, Noncurrent		1,820	1,960
Total assets	[2]	47,372	48,995
Long-term debt due within one year		203	2,624
Accounts payable		1,109	1,692
Accrued expenses		699	786
Unamortized energy contract liabilities		8	17
Other		437	517
Total current liabilities		4,411	7,289
Long-term debt		5,677	4,464
Asset retirement obligations, noncurrent		11,744	10,603
Unamortized energy contract liabilities		8	11
Other		1,488	1,415
Total liabilities	[2]	32,448	33,165
Pepco Holdings LLC [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		196	131	99	124
Restricted cash and cash equivalents		38	36	38	43
Accounts receivable, net
Customer		495	479
Inventory, net
Materials and supplies		194	190
Other current assets		52	49
Total current assets		1,634	1,480
Property, plant and equipment, net		14,954	14,296
Other Assets, Noncurrent		300	323
Total assets	[3]	23,394	22,719
Long-term debt due within one year		349	103
Accounts payable		507	462
Accrued expenses		279	296
Unamortized energy contract liabilities		98	115
Other		144	131
Total current liabilities		1,723	1,612
Long-term debt		6,671	6,460
Asset retirement obligations, noncurrent		58	57
Unamortized energy contract liabilities		258	327
Other		650	577
Total liabilities	[3]	13,325	13,111
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		13	12	13	7
Restricted cash and cash equivalents		4	2	$ 3	$ 4
Accounts receivable, net
Customer		133	108
Inventory, net
Other current assets		4	5
Total current assets		340	270
Property, plant and equipment, net		3,372	3,190
Other Assets, Noncurrent		50	53
Total assets	[4]	4,201	3,933
Long-term debt due within one year		261	20
Accounts payable		168	144
Accrued expenses		42	42
Other		10	9
Total current liabilities		693	360
Long-term debt		1,156	1,307
Other		52	39
Total liabilities	[4]	2,813	2,657
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		148	163
Restricted cash and cash equivalents		52	88
Accounts receivable, net
Customer		151	151
Other		39	39
Unamortized energy contract assets		22	23
Inventory, net
Materials and supplies		241	227
Other current assets		781	32
Total current assets		1,434	723
Property, plant and equipment, net		5,865	6,022
NDT funds		2,785	2,741
Unamortized energy contract assets		253	250
Other Assets, Noncurrent		49	89
Total noncurrent assets		8,952	9,102
Total assets		10,386	9,825
Long-term debt due within one year		134	544
Accounts payable		81	106
Accrued expenses		63	70
Unamortized energy contract liabilities		5	8
Other		26	3
Total current liabilities		309	731
Long-term debt		913	527
Asset retirement obligations, noncurrent		2,210	2,128
Unamortized energy contract liabilities		1	1
Other		106	89
Total noncurrent liabilities		3,230	2,745
Total liabilities		3,539	3,476
PP&E - unrestricted asset		1	20
Other Assets		8	0
Variable Interest Entity, Primary Beneficiary [Member] | Recourse [Member]
Inventory, net
Total liabilities		8	3
Variable Interest Entity, Primary Beneficiary [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		148	163
Restricted cash and cash equivalents		48	85
Accounts receivable, net
Customer		151	151
Other		39	39
Unamortized energy contract assets		22	23
Inventory, net
Materials and supplies		241	227
Other current assets		776	31
Total current assets		1,425	719
Property, plant and equipment, net		5,865	6,022
NDT funds		2,785	2,741
Unamortized energy contract assets		253	250
Other Assets, Noncurrent		38	73
Total noncurrent assets		8,941	9,086
Total assets		10,366	9,805
Long-term debt due within one year		109	523
Accounts payable		81	106
Accrued expenses		63	70
Unamortized energy contract liabilities		5	8
Other		26	3
Total current liabilities		284	710
Long-term debt		906	504
Asset retirement obligations, noncurrent		2,210	2,128
Unamortized energy contract liabilities		1	1
Other		106	89
Total noncurrent liabilities		3,223	2,722
Total liabilities		3,507	3,432
PP&E - unrestricted asset		1	20
Other Assets		8	0
Variable Interest Entity, Primary Beneficiary [Member] | Exelon Generation Co L L C [Member] | Recourse [Member]
Inventory, net
Total liabilities		8	3
Variable Interest Entity, Primary Beneficiary [Member] | Pepco Holdings LLC [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		4	3
Accounts receivable, net
Customer		0	0
Other		0	0
Unamortized energy contract assets		0	0
Inventory, net
Materials and supplies		0	0
Other current assets		5	1
Total current assets		9	4
Property, plant and equipment, net		0	0
NDT funds		0	0
Unamortized energy contract assets		0	0
Other Assets, Noncurrent		11	16
Total noncurrent assets		11	16
Total assets		20	20
Long-term debt due within one year		25	21
Accounts payable		0	0
Accrued expenses		0	0
Unamortized energy contract liabilities		0	0
Other		0	0
Total current liabilities		25	21
Long-term debt		7	23
Asset retirement obligations, noncurrent		0	0
Unamortized energy contract liabilities		0	0
Other		0	0
Total noncurrent liabilities		7	23
Total liabilities		32	44
Variable Interest Entity, Primary Beneficiary [Member] | Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		4	3
Accounts receivable, net
Customer		0	0
Other		0	0
Unamortized energy contract assets		0	0
Inventory, net
Materials and supplies		0	0
Other current assets		0	0
Total current assets		4	3
Property, plant and equipment, net		0	0
NDT funds		0	0
Unamortized energy contract assets		0	0
Other Assets, Noncurrent		10	14
Total noncurrent assets		10	14
Total assets		14	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		0	0
Total current liabilities		20	20
Long-term debt		6	21
Asset retirement obligations, noncurrent		0	0
Unamortized energy contract liabilities		0	0
Other		0	0
Total noncurrent liabilities		6	21
Total liabilities		$ 26	$ 41
[1]	Exelon’s consolidated assets include $10,102 million and $9,532 million at September 30, 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 $3,531 million and $3,473 million at September 30, 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 $10,082 million and $9,512 million at September 30, 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 $3,499 million and $3,429 million at September 30, 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 $20 million and $20 million at September 30, 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 $32 million and $44 million at September 30, 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 $14 million and $17 million at September 30, 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 $26 million and $41 million at September 30, 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		Sep. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Total assets	[1]	$ 127,767	$ 124,977
Total liabilities	[1]	92,664	90,404
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets	[2]	47,372	48,995
Total liabilities	[2]	32,448	$ 33,165
Exelon Generation Co L L C [Member] | CENG [Member]
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage			50.01%
Exelon Generation Co L L C [Member] | Distributed Energy Company
Variable Interest Entity [Line Items]
Equity Method Investment, Ownership Percentage			31.00%
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		1,145	$ 1,079
Total liabilities		441	260
Exelon's ownership interest in VIE		163	191
Other ownership interests in VIE		541	629
Variable Interest Entity, Not Primary Beneficiary [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets		1,145	1,079
Total liabilities		441	260
Exelon's ownership interest in VIE		163	191
Other ownership interests in VIE		541	629
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		10,386	9,825
Total liabilities		3,539	3,476
Variable Interest Entity, Primary Beneficiary [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets		10,366	9,805
Total liabilities		3,507	3,432
Commercial Agreement VIE [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		736	636
Total liabilities		216	33
Exelon's ownership interest in VIE		0	0
Other ownership interests in VIE		520	604
Commercial Agreement VIE [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets		736	636
Total liabilities		216	33
Exelon's ownership interest in VIE		0	0
Other ownership interests in VIE		520	604
Equity Investment VIE [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		409	443
Total liabilities		225	227
Exelon's ownership interest in VIE		163	191
Other ownership interests in VIE		21	25
Equity Investment VIE [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets		409	443
Total liabilities		225	227
Exelon's ownership interest in VIE		163	191
Other ownership interests in VIE		$ 21	$ 25
[1]	Exelon’s consolidated assets include $10,102 million and $9,532 million at September 30, 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 $3,531 million and $3,473 million at September 30, 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 $10,082 million and $9,512 million at September 30, 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 $3,499 million and $3,429 million at September 30, 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.

Supplemental Financial Inform_3

Supplemental Financial Information - Operations (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	$ 30	$ 30	$ 48	$ 48
Variable Lease Income	76	80	225	209
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	50	67	127	197
Net realized income on NDT funds - Non-regulatory agreement units	23	33	127	316
Net unrealized gains on NDT funds - Regulatory agreement units	398	89	111	565
Net unrealized gains on NDT funds - Non-regulatory agreement units	254	55	1	236
Regulatory offset to NDT fund-related activities	(359)	(125)	(192)	(611)
Decommissioning-related activities	366	119	174	703
AFUDC - Equity	27	22	76	64
Non-service net periodic benefit cost	15	(2)	38	8
Exelon Generation Co L L C [Member]
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	28	29	43	44
Variable Lease Income	76	80	224	206
Decommissioning-Related Activities [Abstract]
Net realized income on NDT funds - Regulatory agreement units	50	67	127	197
Net realized income on NDT funds - Non-regulatory agreement units	23	33	127	316
Net unrealized gains on NDT funds - Regulatory agreement units	398	89	111	565
Net unrealized gains on NDT funds - Non-regulatory agreement units	254	55	1	236
Regulatory offset to NDT fund-related activities	(359)	(125)	(192)	(611)
Decommissioning-related activities	366	119	174	703
AFUDC - Equity	0	0	0	0
Commonwealth Edison Co [Member]
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	7	4	22	13
PECO Energy Co [Member]
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	5	3	12	9
Baltimore Gas and Electric Company [Member]
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	6	6	16	16
Pepco Holdings LLC [Member]
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	1	1	3	3
Variable Lease Income	0	0	1	3
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	9	9	26	26
Potomac Electric Power Company [Member]
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	7	7	20	18
Delmarva Power and Light Company [Member]
Supplemental Statement of Operations Information [Line Items]
Operating Lease Income	1	1	3	3
Variable Lease Income	0	0	1	3
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	1	1	3	3
Atlantic City Electric Company [Member]
Decommissioning-Related Activities [Abstract]
AFUDC - Equity	$ 1	$ 1	$ 3	$ 4

Supplemental Financial Inform_4

Supplemental Financial Information - Taxes Other Than Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Supplemental Statement of Operations Information [Line Items]
Utility taxes	$ 237	$ 241	$ 651	$ 672
Property	152	148	449	444
Payroll	59	57	183	185
Exelon Generation Co L L C [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	26	29	75	87
Property	66	66	199	205
Payroll	29	28	88	92
Commonwealth Edison Co [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	66	66	181	183
Property	7	7	23	22
Payroll	7	7	21	21
PECO Energy Co [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	41	38	102	102
Property	4	5	12	12
Payroll	4	3	12	11
Baltimore Gas and Electric Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	21	21	65	68
Property	42	39	121	114
Payroll	4	4	13	13
Pepco Holdings LLC [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	83	86	228	231
Property	32	31	94	91
Payroll	6	6	21	20
Potomac Electric Power Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	77	81	210	217
Property	21	21	63	64
Payroll	2	2	6	5
Delmarva Power and Light Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	5	5	16	14
Property	10	9	29	25
Payroll	1	1	4	3
Atlantic City Electric Company [Member]
Supplemental Statement of Operations Information [Line Items]
Utility taxes	1	0	2	0
Property	1	0	2	2
Payroll	$ 1	$ 1	$ 3	$ 2

Supplemental Financial Inform_5

Supplemental Financial Information - Cash Flow (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	$ 2,831	$ 2,803
Amortization of regulatory assets	434	390
Amortization of intangible assets, net	47	44
Amortization of energy contract assets and liabilities	24	14
Nuclear fuel	708	771
ARO accretion	375	371
Total depreciation, amortization and accretion	4,419	4,393
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	310	324
Provision for uncollectible accounts	130	89
Other decommissioning-related activity	(301)	(400)
Energy-related options	79	21
True-up adjustments to decoupling mechanisms and formula rates	66	72
Restructuring Costs	96
Inventory Write-down	119
Long-term incentive plan	(8)	33
Amortization of operating ROU asset	185	193
Deferred payments for legal settlements	200
Change in environmental liabilities		23
Exelon Generation Co L L C [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	1,121	1,184
Amortization of regulatory assets	0	0
Amortization of intangible assets, net	40	37
Amortization of energy contract assets and liabilities	22	14
Nuclear fuel	708	771
ARO accretion	375	371
Total depreciation, amortization and accretion	2,266	2,377
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	89	98
Provision for uncollectible accounts	16	20
Other decommissioning-related activity	(301)	(400)
Energy-related options	79	21
True-up adjustments to decoupling mechanisms and formula rates	0	0
Restructuring Costs	88
Inventory Write-down	118
Amortization of operating ROU asset	135	138
Change in environmental liabilities		0
Commonwealth Edison Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	689	661
Amortization of regulatory assets	152	106
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	841	767
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	85	70
Provision for uncollectible accounts	23	26
True-up adjustments to decoupling mechanisms and formula rates	51	80
Restructuring Costs	1
Inventory Write-down	1
Amortization of operating ROU asset	1	2
Deferred payments for legal settlements	200
Change in environmental liabilities		0
PECO Energy Co [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	238	225
Amortization of regulatory assets	21	22
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	259	247
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	4	9
Provision for uncollectible accounts	38	22
True-up adjustments to decoupling mechanisms and formula rates	(10)	0
Restructuring Costs	0
Inventory Write-down	1
Amortization of operating ROU asset	0	0
Change in environmental liabilities		0
Baltimore Gas and Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	293	263
Amortization of regulatory assets	112	105
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	405	368
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	46	45
Provision for uncollectible accounts	12	5
True-up adjustments to decoupling mechanisms and formula rates	10	0
Restructuring Costs	0
Inventory Write-down	0
Amortization of operating ROU asset	23	23
Change in environmental liabilities		0
Pepco Holdings LLC [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	436	405
Amortization of regulatory assets	149	157
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	585	562
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	52	71
Provision for uncollectible accounts	41	16
True-up adjustments to decoupling mechanisms and formula rates	15	(8)
Restructuring Costs	0
Inventory Write-down	(1)
Amortization of operating ROU asset	21	26
Change in environmental liabilities		23
Potomac Electric Power Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	191	178
Amortization of regulatory assets	91	103
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	282	281
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	11	19
Provision for uncollectible accounts	24	7
True-up adjustments to decoupling mechanisms and formula rates	(20)	(9)
Restructuring Costs	0
Inventory Write-down	0
Amortization of operating ROU asset	5	6
Change in environmental liabilities		23
Delmarva Power and Light Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	116	109
Amortization of regulatory assets	27	29
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	143	138
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	6	11
Provision for uncollectible accounts	15	2
True-up adjustments to decoupling mechanisms and formula rates	15	1
Restructuring Costs	0
Inventory Write-down	(1)
Amortization of operating ROU asset	6	7
Change in environmental liabilities		0
Atlantic City Electric Company [Member]
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	104	89
Amortization of regulatory assets	30	25
Amortization of intangible assets, net	0	0
ARO accretion	0	0
Total depreciation, amortization and accretion	134	114
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefit costs	10	12
Provision for uncollectible accounts	2	6
True-up adjustments to decoupling mechanisms and formula rates	20	0
Restructuring Costs	0
Inventory Write-down	0
Amortization of operating ROU asset	$ 2	4
Change in environmental liabilities		$ 0

Supplemental Financial Inform_6

Supplemental Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 1,858	$ 587	$ 1,683	$ 1,349
Restricted cash	485	358	309	247
Restricted cash included in other long-term assets	137	177	186	185
Total cash, cash equivalents and restricted cash	2,480	1,122	2,178	1,781
Accrued Expenses [Abstract]
Compensation-related accruals	898	1,052
Taxes accrued	403	414
Interest accrued	440	337
Exelon Generation Co L L C [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	623	303	1,019	750
Restricted cash	100	146	126	153
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	723	449	1,145	903
Accrued Expenses [Abstract]
Compensation-related accruals	352	422
Taxes accrued	183	222
Interest accrued	79	65
Commonwealth Edison Co [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	76	90	76	135
Restricted cash	305	150	124	29
Restricted cash included in other long-term assets	127	163	171	166
Total cash, cash equivalents and restricted cash	508	403	371	330
Accrued Expenses [Abstract]
Compensation-related accruals	147	171
Taxes accrued	55	83
Interest accrued	64	110
PECO Energy Co [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	242	21	224	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	249	27	230	135
Accrued Expenses [Abstract]
Compensation-related accruals	60	58
Taxes accrued	25	3
Interest accrued	36	37
Baltimore Gas and Electric Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	326	24	130	7
Restricted cash	1	1	1	6
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	327	25	131	13
Accrued Expenses [Abstract]
Compensation-related accruals	72	78
Taxes accrued	63	26
Interest accrued	40	46
Pepco Holdings LLC [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	196	131	99	124
Restricted cash	38	36	38	43
Restricted cash included in other long-term assets	10	14	15	19
Total cash, cash equivalents and restricted cash	244	181	152	186
Accrued Expenses [Abstract]
Compensation-related accruals	95	101
Taxes accrued	84	117
Interest accrued	80	49
Potomac Electric Power Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	125	30	18	16
Restricted cash	33	33	34	37
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	158	63	52	53
Accrued Expenses [Abstract]
Compensation-related accruals	31	28
Taxes accrued	65	90
Interest accrued	38	23
Delmarva Power and Light Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	26	13	11	23
Restricted cash	0	0	0	1
Restricted cash included in other long-term assets	0	0	0	0
Total cash, cash equivalents and restricted cash	26	13	11	24
Accrued Expenses [Abstract]
Compensation-related accruals	16	19
Taxes accrued	10	14
Interest accrued	21	8
Atlantic City Electric Company [Member]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	13	12	13	7
Restricted cash	4	2	3	4
Restricted cash included in other long-term assets	10	14	15	19
Total cash, cash equivalents and restricted cash	27	28	$ 31	$ 30
Accrued Expenses [Abstract]
Compensation-related accruals	14	15
Taxes accrued	3	8
Interest accrued	$ 21	$ 12

Related Party Transactions - Op

Related Party Transactions - Operating Revenues and Purchased Power and Fuel (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Related Party Transaction [Line Items]
Revenue from Related Parties	$ 1	$ 0	$ 4	$ 0
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	331	275	932	844
Purchased power and/or fuel from affiliates	3	3	(6)	7
Exelon Generation Co L L C [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	71	83	241	266
Purchased power and/or fuel from affiliates	0		11	4
Exelon Generation Co L L C [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	68	43	146	123
Exelon Generation Co L L C [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	84	65	252	199
Exelon Generation Co L L C [Member] | Pepco Holdings LLC Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	105	83	288	254
Exelon Generation Co L L C [Member] | Potomac Electric Power Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	80	66	219	188
Exelon Generation Co L L C [Member] | Delmarva Power and Light Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	21	14	60	50
Exelon Generation Co L L C [Member] | Atlantic City Electric Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	4	3	9	16
Exelon Generation Co L L C [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	3	1	5	2
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Revenue from Related Parties	15	4	31	13
Purchased power and/or fuel from affiliates	71	83	252	270
Commonwealth Edison Co [Member] | Exelon Generation Co LLC Affiliate [Member]
Related Party Transaction [Line Items]
Purchased power and/or fuel from affiliates	$ 71	$ 83	$ 252	$ 270

Related Party Transactions - BS

Related Party Transactions - BSC and PHISCO Service Companies (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	$ 148	$ 125	$ 390	$ 357
PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction Capitalized Costs Support Services	15	16	45	57
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	132	140	409	439
Exelon Generation Co L L C [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	133	138	406	434
Related Party Transaction Capitalized Costs Support Services	13	18	37	44
Commonwealth Edison Co [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	69	73	209	196
Commonwealth Edison Co [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	65	72	204	195
Related Party Transaction Capitalized Costs Support Services	49	37	133	98
PECO Energy Co [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	37	37	114	112
PECO Energy Co [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	34	36	107	110
Related Party Transaction Capitalized Costs Support Services	20	22	53	68
Baltimore Gas and Electric Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	39	39	122	118
Baltimore Gas and Electric Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	38	38	120	116
Related Party Transaction Capitalized Costs Support Services	30	30	88	89
Pepco Holdings LLC [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	38	36	111	105
Pepco Holdings LLC [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	36	35	107	102
Related Party Transaction Capitalized Costs Support Services	36	18	79	58
Pepco Holdings LLC [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	0	0	0	0
Related Party Transaction Capitalized Costs Support Services	15	16	45	57
Potomac Electric Power Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	49	50	152	156
Potomac Electric Power Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	20	21	61	64
Related Party Transaction Capitalized Costs Support Services	14	8	29	25
Potomac Electric Power Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	28	29	90	92
Related Party Transaction Capitalized Costs Support Services	7	8	20	26
Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	37	37	112	113
Delmarva Power and Light Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	13	13	38	39
Related Party Transaction Capitalized Costs Support Services	12	5	26	16
Delmarva Power and Light Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	24	24	73	74
Related Party Transaction Capitalized Costs Support Services	4	4	13	16
Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	32	32	98	99
Atlantic City Electric Company [Member] | Exelon Business Services Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	11	10	32	31
Related Party Transaction Capitalized Costs Support Services	10	4	22	13
Atlantic City Electric Company [Member] | PHI Service Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Expenses from Transactions with Related Party	21	22	65	67
Related Party Transaction Capitalized Costs Support Services	$ 4	$ 4	$ 12	$ 15

Related Party Transactions - Cu

Related Party Transactions - Current Receivables From/Payables To Affiliates (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	$ 423	$ 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	113	117
Accounts Receivable, Related Parties, Current	109	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	56	78
Due to Related Parties, Current	28	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	17	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	8	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	13	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	2	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	4	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	82	103
Accounts Receivable, Related Parties, Current	20	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	19	27
Accounts Payable, Related Parties, Current	28	41
Commonwealth Edison Co [Member] | Affiliated Entity [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	110	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	47	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	39	66
Accounts Receivable, Related Parties, Current	0	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	0	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	71	98
Accounts Receivable, Related Parties, Current	0	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	43	66
Delmarva Power and Light Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	23	32
Atlantic City Electric Company [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Current	24	25
Accounts Receivable, Related Parties, Current	1	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	0	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	211	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	69	67
Business Services Company [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	49	54
Business Services Company [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	24	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	29	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	16	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	11	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	10	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	31	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	10	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	51	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	25	23
Other Legal Entities [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	5	8
Other Legal Entities [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Related Party Transaction, Due from (to) Related Party, Current	6	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	2	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	$ 0	$ 1

Related Party Transactions - No

Related Party Transactions - Noncurrent Receivables from/Payables to affiliates (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Exelon Generation Co L L C [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	$ 2,888	$ 3,103
Exelon Generation Co L L C [Member] | Commonwealth Edison Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	2,445	2,622
Exelon Generation Co L L C [Member] | PECO Energy Co Affiliate [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	443	480
Other Legal Entities [Member] | Business Services Corporation [Member]
Related Party Transaction [Line Items]
Accounts Payable, Related Parties, Noncurrent	$ 0	$ 1

Related Party Transactions - Lo

Related Party Transactions - Long Term Debt to Financing Trusts (Details) - USD ($) $ in Millions	Sep. 30, 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 transmission tower attachment agreements [Member] - Subsequent Event [Member] $ in Millions	Jul. 01, 2020USD ($)
Potomac Electric Power Company [Member]
Subsequent Event [Line Items]
Agreement Liabilities Recorded	$ 98
Delmarva Power and Light Company [Member]
Subsequent Event [Line Items]
Undivided Interest Sold	60.00%
Agreement Liabilities Recorded	$ 13
Atlantic City Electric Company [Member]
Subsequent Event [Line Items]
Undivided Interest Sold	60.00%
Agreement Liabilities Recorded	$ 13