Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net income (loss)	$ 1,954	$ 3,028	$ 2,079
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	6,527	5,780	5,971
Asset impairments	591	201	50
Gain on sales of assets and businesses	(24)	(27)	(56)
Deferred income taxes and amortization of investment tax credits	309	681	(108)
Net fair value changes related to derivatives	(268)	222	294
Net realized and unrealized (gains) losses on NDT fund investments	(461)	(663)	303
Unrealized Gain (Loss) on Investments	(186)	0	0
Other non-cash operating activities	592	613	1,131
Changes in assets and liabilities:
Accounts receivable	697	(243)	(565)
Inventories	(85)	(87)	(37)
Accounts payable and accrued expenses	(129)	(425)	551
Option premiums (paid) received, net	(139)	(29)	(43)
Collateral received (posted), net	494	(438)	82
Income taxes	140	(64)	340
Pension and non-pension postretirement benefit contributions	(601)	(408)	(383)
Other assets and liabilities	(5,176)	(1,482)	(965)
Net cash flows provided by operating activities	4,235	6,659	8,644
Cash flows from investing activities
Capital expenditures	(8,048)	(7,248)	(7,594)
Proceeds from NDT fund sales	3,341	10,051	8,762
Investment in NDT funds	(3,464)	(10,087)	(8,997)
Collection of deferred purchase price	3,771	0	0
Acquisitions of assets and businesses, net	0	(41)	(154)
Proceeds from sales of assets and businesses	46	53	91
Other investing activities	18	12	58
Net cash flows used in investing activities	(4,336)	(7,260)	(7,834)
Cash flows from financing activities
Changes in short-term borrowings	161	781	(338)
Proceeds from short-term borrowings with maturities greater than 90 days	500	0	126
Repayments on short-term borrowings with maturities greater than 90 days	0	(125)	(1)
Issuance of long-term debt	7,507	1,951	3,115
Retirement of long-term debt	(6,440)	(1,287)	(1,786)
Dividends paid on common stock	(1,492)	(1,408)	(1,332)
Proceeds from employee stock plans	45	112	105
Other financing activities	(136)	(82)	(108)
Net cash flows provided by (used in) financing activities	145	(58)	(219)
Increase (Decrease) in cash, restricted cash, and cash equivalents	44	(659)	591
Cash, restricted cash, and cash equivalents at beginning of period	1,122	1,781	1,190
Cash, restricted cash, and cash equivalents at end of period	1,166	1,122	1,781
Capital Expenditures Incurred but Not yet Paid	194	(7)	(69)
Increase in Deferred Purchase Price	4,441	0	0
Increase (decrease) in PPE related to ARO update	850	968	(107)
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income (loss)	579	1,217	443
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	3,636	3,063	3,415
Asset impairments	563	201	50
Gain on sales of assets and businesses	(11)	(27)	(48)
Deferred income taxes and amortization of investment tax credits	78	361	(451)
Net fair value changes related to derivatives	(270)	228	307
Net realized and unrealized (gains) losses on NDT fund investments	(461)	(663)	303
Unrealized Gain (Loss) on Investments	(186)	0	0
Other non-cash operating activities	18	(124)	298
Changes in assets and liabilities:
Accounts receivable	1,125	(186)	(359)
Receivables from and payables to affiliates, net	24	(52)	8
Inventories	(77)	(47)	(12)
Accounts payable and accrued expenses	(343)	(248)	376
Option premiums (paid) received, net	(139)	(29)	(43)
Collateral received (posted), net	479	(481)	64
Income taxes	186	302	(193)
Pension and non-pension postretirement benefit contributions	(255)	(175)	(139)
Other assets and liabilities	(4,362)	(467)	(158)
Net cash flows provided by operating activities	584	2,873	3,861
Cash flows from investing activities
Capital expenditures	(1,747)	(1,845)	(2,242)
Proceeds from NDT fund sales	3,341	10,051	8,762
Investment in NDT funds	(3,464)	(10,087)	(8,997)
Collection of deferred purchase price	3,771	0	0
Acquisitions of assets and businesses, net	0	(41)	(154)
Proceeds from sales of assets and businesses	46	52	90
Other investing activities	11	3	10
Net cash flows used in investing activities	1,958	(1,867)	(2,531)
Cash flows from financing activities
Changes in short-term borrowings	20	320	0
Proceeds from short-term borrowings with maturities greater than 90 days	500	0	0
Issuance of long-term debt	3,155	42	15
Retirement of long-term debt	(4,334)	(813)	(141)
Repayment of long term debt to affiliate	(550)	0	0
Distributions to member	(1,734)	(899)	(1,001)
Contributions from member	64	41	155
Changes in Exelon/PHI intercompany money pool	285	(100)	46
Other financing activities	(70)	(51)	(55)
Net cash flows provided by (used in) financing activities	(2,664)	(1,460)	(981)
Increase (Decrease) in cash, restricted cash, and cash equivalents	(122)	(454)	349
Cash, restricted cash, and cash equivalents at beginning of period	449	903	554
Cash, restricted cash, and cash equivalents at end of period	327	449	903
Increase (decrease) in capital expenditures not paid	(88)	(34)	(199)
Increase in Deferred Purchase Price	4,441	0	0
Increase (decrease) in PPE related to ARO update	850	959	(130)
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income (loss)	438	688	664
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	1,133	1,033	940
Deferred income taxes and amortization of investment tax credits	228	109	259
Unrealized Gain (Loss) on Investments	0
Other non-cash operating activities	202	265	242
Changes in assets and liabilities:
Accounts receivable	(10)	(34)	(136)
Receivables from and payables to affiliates, net	(1)	(12)	26
Inventories	(13)	(16)	1
Accounts payable and accrued expenses	63	(51)	70
Collateral received (posted), net	14	48	11
Income taxes	8	95	62
Pension and non-pension postretirement benefit contributions	(148)	(77)	(42)
Other assets and liabilities	(590)	(345)	(348)
Net cash flows provided by operating activities	1,324	1,703	1,749
Cash flows from investing activities
Capital expenditures	(2,217)	(1,915)	(2,126)
Other investing activities	2	29	29
Net cash flows used in investing activities	(2,215)	(1,886)	(2,097)
Cash flows from financing activities
Changes in short-term borrowings	193	130	0
Issuance of long-term debt	1,000	700	1,350
Retirement of long-term debt	(500)	(300)	(840)
Dividends paid on common stock	(499)	(508)	(459)
Contributions from parent	712	250	500
Other financing activities	(13)	(16)	(17)
Net cash flows provided by (used in) financing activities	893	256	534
Increase (Decrease) in cash, restricted cash, and cash equivalents	2	73	186
Cash, restricted cash, and cash equivalents at beginning of period	403	330	144
Cash, restricted cash, and cash equivalents at end of period	405	403	330
Increase (decrease) in capital expenditures not paid	109	(37)	11
PECO Energy Co [Member]
Cash flows from operating activities
Net income (loss)	447	528	460
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	347	333	301
Gain on sales of assets and businesses	0	(1)	0
Deferred income taxes and amortization of investment tax credits	(23)	20	(5)
Unrealized Gain (Loss) on Investments	0
Other non-cash operating activities	24	38	51
Changes in assets and liabilities:
Accounts receivable	(88)	(29)	(74)
Receivables from and payables to affiliates, net	(6)	(5)	7
Inventories	(1)	4	(14)
Accounts payable and accrued expenses	63	(11)	(3)
Income taxes	31	(34)	15
Pension and non-pension postretirement benefit contributions	(18)	(28)	(28)
Other assets and liabilities	1	(64)	29
Net cash flows provided by operating activities	777	751	739
Cash flows from investing activities
Capital expenditures	(1,147)	(939)	(849)
Changes in Exelon/PHI intercompany money pool	68	(68)	0
Other investing activities	7	(1)	9
Net cash flows used in investing activities	(1,072)	(1,008)	(840)
Cash flows from financing activities
Issuance of long-term debt	350	325	700
Retirement of long-term debt	0	0	(500)
Dividends paid on common stock	(340)	(358)	(306)
Contributions from parent	248	188	89
Changes in Exelon/PHI intercompany money pool	40	0	0
Other financing activities	(4)	(6)	(22)
Net cash flows provided by (used in) financing activities	294	149	(39)
Increase (Decrease) in cash, restricted cash, and cash equivalents	(1)	(108)	(140)
Cash, restricted cash, and cash equivalents at beginning of period	27	135	275
Cash, restricted cash, and cash equivalents at end of period	26	27	135
Increase (decrease) in capital expenditures not paid	55	40	(12)
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income (loss)	349	360	313
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	550	502	483
Deferred income taxes and amortization of investment tax credits	37	130	76
Unrealized Gain (Loss) on Investments	0
Other non-cash operating activities	97	85	58
Changes in assets and liabilities:
Accounts receivable	(165)	25	8
Receivables from and payables to affiliates, net	(8)	1	12
Inventories	10	(1)	2
Accounts payable and accrued expenses	102	(43)	(1)
Collateral received (posted), net	0	(4)	4
Income taxes	60	(67)	(20)
Pension and non-pension postretirement benefit contributions	(78)	(48)	(54)
Other assets and liabilities	(70)	(192)	(92)
Net cash flows provided by operating activities	884	748	789
Cash flows from investing activities
Capital expenditures	(1,247)	(1,145)	(959)
Other investing activities	2	8	9
Net cash flows used in investing activities	(1,245)	(1,137)	(950)
Cash flows from financing activities
Changes in short-term borrowings	(76)	40	(42)
Issuance of long-term debt	400	400	300
Dividends paid on common stock	(246)	(224)	(209)
Contributions from parent	411	193	109
Other financing activities	(8)	(8)	(2)
Net cash flows provided by (used in) financing activities	481	401	156
Increase (Decrease) in cash, restricted cash, and cash equivalents	120	12	(5)
Cash, restricted cash, and cash equivalents at beginning of period	25	13	18
Cash, restricted cash, and cash equivalents at end of period	145	25	13
Increase (decrease) in capital expenditures not paid	53	6	50
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income (loss)	495	477	393
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	782	754	740
Deferred income taxes and amortization of investment tax credits	(97)	(7)	30
Unrealized Gain (Loss) on Investments	0
Other non-cash operating activities	103	161	150
Changes in assets and liabilities:
Accounts receivable	(159)	(39)	(2)
Receivables from and payables to affiliates, net	3	3	8
Inventories	(6)	(27)	(14)
Accounts payable and accrued expenses	49	(17)	45
Income taxes	(25)	16	34
Pension and non-pension postretirement benefit contributions	(39)	(25)	(74)
Other assets and liabilities	(104)	(179)	(178)
Net cash flows provided by operating activities	1,002	1,117	1,132
Cash flows from investing activities
Capital expenditures	(1,604)	(1,355)	(1,375)
Other investing activities	7	(3)	4
Net cash flows used in investing activities	(1,597)	(1,358)	(1,371)
Cash flows from financing activities
Changes in short-term borrowings	160	154	(296)
Proceeds from short-term borrowings with maturities greater than 90 days	0	0	125
Repayments on short-term borrowings with maturities greater than 90 days	0	(125)	0
Issuance of long-term debt	602	485	750
Retirement of long-term debt	(128)	(157)	(299)
Distributions to member	(553)	(526)	(326)
Contributions from member	494	398	385
Changes in Exelon/PHI intercompany money pool	9	12	0
Other financing activities	(10)	(5)	(9)
Net cash flows provided by (used in) financing activities	574	236	330
Increase (Decrease) in cash, restricted cash, and cash equivalents	(21)	(5)	91
Cash, restricted cash, and cash equivalents at beginning of period	181	186	95
Cash, restricted cash, and cash equivalents at end of period	160	181	186
Increase (decrease) in capital expenditures not paid	54	2	93
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income (loss)	266	243	205
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	377	374	385
Deferred income taxes and amortization of investment tax credits	(46)	1	(20)
Unrealized Gain (Loss) on Investments	0
Other non-cash operating activities	(23)	56	67
Changes in assets and liabilities:
Accounts receivable	(67)	(22)	(5)
Receivables from and payables to affiliates, net	(12)	5	(17)
Inventories	1	(19)	(6)
Accounts payable and accrued expenses	41	(39)	59
Income taxes	(1)	9	(13)
Pension and non-pension postretirement benefit contributions	(11)	(14)	(17)
Other assets and liabilities	(24)	(82)	(164)
Net cash flows provided by operating activities	501	512	474
Cash flows from investing activities
Capital expenditures	(773)	(626)	(656)
Other investing activities	0	3	2
Net cash flows used in investing activities	(773)	(623)	(654)
Cash flows from financing activities
Changes in short-term borrowings	(47)	42	14
Issuance of long-term debt	300	260	200
Retirement of long-term debt	(3)	(125)	(14)
Dividends paid on common stock	(232)	(213)	(169)
Contributions from parent	262	160	166
Other financing activities	(6)	(3)	(4)
Net cash flows provided by (used in) financing activities	274	121	193
Increase (Decrease) in cash, restricted cash, and cash equivalents	2	10	13
Cash, restricted cash, and cash equivalents at beginning of period	63	53	40
Cash, restricted cash, and cash equivalents at end of period	65	63	53
Increase (decrease) in capital expenditures not paid	1	39	20
Delmarva Power & Light Company [Member]
Cash flows from operating activities
Net income (loss)	125	147	120
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	191	184	182
Deferred income taxes and amortization of investment tax credits	(13)	(7)	24
Unrealized Gain (Loss) on Investments	0
Other non-cash operating activities	51	27	24
Changes in assets and liabilities:
Accounts receivable	(34)	(5)	8
Receivables from and payables to affiliates, net	8	(5)	(9)
Inventories	(5)	(6)	(3)
Accounts payable and accrued expenses	4	3	11
Income taxes	(25)	12	2
Pension and non-pension postretirement benefit contributions	0	(1)	0
Other assets and liabilities	(30)	(55)	(7)
Net cash flows provided by operating activities	272	294	352
Cash flows from investing activities
Capital expenditures	(424)	(348)	(364)
Other investing activities	(3)	1	2
Net cash flows used in investing activities	(427)	(347)	(362)
Cash flows from financing activities
Changes in short-term borrowings	90	56	(216)
Issuance of long-term debt	178	75	200
Retirement of long-term debt	(80)	(12)	(4)
Dividends paid on common stock	(141)	(139)	(96)
Contributions from parent	112	63	150
Other financing activities	(2)	(1)	(2)
Net cash flows provided by (used in) financing activities	157	42	32
Increase (Decrease) in cash, restricted cash, and cash equivalents	2	(11)	22
Cash, restricted cash, and cash equivalents at beginning of period	13	24	2
Cash, restricted cash, and cash equivalents at end of period	15	13	24
Increase (decrease) in capital expenditures not paid	20	(4)	22
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income (loss)	112	99	75
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	180	157	136
Deferred income taxes and amortization of investment tax credits	(37)	3	25
Unrealized Gain (Loss) on Investments	0
Other non-cash operating activities	36	22	24
Changes in assets and liabilities:
Accounts receivable	(55)	(13)	(8)
Receivables from and payables to affiliates, net	6	(6)	1
Inventories	(3)	(1)	(4)
Accounts payable and accrued expenses	5	26	(7)
Income taxes	(1)	2	(2)
Pension and non-pension postretirement benefit contributions	(2)	(1)	(6)
Other assets and liabilities	(42)	(27)	(6)
Net cash flows provided by operating activities	199	261	228
Cash flows from investing activities
Capital expenditures	(401)	(375)	(335)
Other investing activities	6	(1)	1
Net cash flows used in investing activities	(395)	(376)	(334)
Cash flows from financing activities
Changes in short-term borrowings	117	56	(94)
Proceeds from short-term borrowings with maturities greater than 90 days	0	0	125
Repayments on short-term borrowings with maturities greater than 90 days	0	(125)	0
Issuance of long-term debt	123	150	350
Retirement of long-term debt	(44)	(18)	(281)
Dividends paid on common stock	(114)	(124)	(59)
Contributions from parent	117	175	67
Other financing activities	(1)	(1)	(3)
Net cash flows provided by (used in) financing activities	198	113	105
Increase (Decrease) in cash, restricted cash, and cash equivalents	2	(2)	(1)
Cash, restricted cash, and cash equivalents at beginning of period	28	30	31
Cash, restricted cash, and cash equivalents at end of period	30	28	30
Increase (decrease) in capital expenditures not paid	$ 33	$ (29)	$ 46