Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net income (loss)	$ 3,028	$ 2,079	$ 3,869
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	5,780	5,971	5,427
Asset impairments	201	50	573
Gain on sales of assets and businesses	(27)	(56)	(3)
Bargain purchase gain	0	0	(233)
Gain on deconsolidation of business	0	0	(213)
Deferred income taxes and amortization of investment tax credits	681	(108)	(362)
Net fair value changes related to derivatives	222	294	151
Net realized and unrealized (gains) losses on NDT fund investments	(663)	303	(616)
Other non-cash operating activities	613	1,131	728
Changes in assets and liabilities:
Accounts receivable	(243)	(565)	(470)
Inventories	(87)	(37)	(72)
Accounts payable and accrued expenses	(425)	551	(388)
Option premiums (paid) received, net	(29)	(43)	28
Collateral (posted) received, net	(438)	82	(158)
Income taxes	(64)	340	299
Pension and non-pension postretirement benefit contributions	(408)	(383)	(405)
Other assets and liabilities	(1,482)	(965)	(675)
Net cash flows provided by operating activities	6,659	8,644	7,480
Cash flows from investing activities
Capital expenditures	(7,248)	(7,594)	(7,584)
Proceeds from NDT fund sales	10,051	8,762	7,845
Investment in NDT funds	(10,087)	(8,997)	(8,113)
Reduction of restricted cash from deconsolidation of business	0	0	(87)
Acquisitions of assets and businesses, net	(41)	(154)	(208)
Proceeds from sales of assets and businesses	53	91	219
Other investing activities	12	58	(43)
Net cash flows used in investing activities	(7,260)	(7,834)	(7,971)
Cash flows from financing activities
Changes in short-term borrowings	781	(338)	(261)
Proceeds from short-term borrowings with maturities greater than 90 days	0	126	621
Repayments on short-term borrowings with maturities greater than 90 days	(125)	(1)	(700)
Issuance of long-term debt	1,951	3,115	3,470
Retirement of long-term debt	(1,287)	(1,786)	(2,490)
Retirement of long-term debt to financing trust	0	0	(250)
Common stock issued from treasury stock	0	0	1,150
Dividends paid on common stock	(1,408)	(1,332)	(1,236)
Proceeds from employee stock plans	112	105	150
Sale of noncontrolling interest	0	0	396
Other financing activities	(82)	(108)	(83)
Net cash flows provided by (used in) financing activities	(58)	(219)	767
Increase (Decrease) in cash, cash equivalents and restricted cash	(659)	591	276
Cash, cash equivalents, and restricted cash at beginning of period	1,781	1,190	914
Cash, cash equivalents, and restricted cash at end of period	1,122	1,781	1,190
Capital Expenditures Incurred but Not yet Paid	(7)	(69)	42
Increase (decrease) in PPE related to ARO update	968	(107)	29
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income (loss)	1,217	443	2,798
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	3,063	3,415	3,056
Asset impairments	201	50	510
Gain on sales of assets and businesses	(27)	(48)	(2)
Bargain purchase gain	0	0	(233)
Gain on deconsolidation of business	0	0	(213)
Deferred income taxes and amortization of investment tax credits	361	(451)	(2,023)
Net fair value changes related to derivatives	228	307	167
Net realized and unrealized (gains) losses on NDT fund investments	(663)	303	(616)
Other non-cash operating activities	(124)	298	112
Changes in assets and liabilities:
Accounts receivable	(186)	(359)	(320)
Receivables from and payables to affiliates, net	(52)	8	(7)
Inventories	(47)	(12)	(29)
Accounts payable and accrued expenses	(248)	376	4
Option premiums (paid) received, net	(29)	(43)	28
Collateral (posted) received, net	(481)	64	(129)
Income taxes	302	(193)	496
Pension and non-pension postretirement benefit contributions	(175)	(139)	(148)
Other assets and liabilities	(467)	(158)	(152)
Net cash flows provided by operating activities	2,873	3,861	3,299
Cash flows from investing activities
Capital expenditures	(1,845)	(2,242)	(2,259)
Proceeds from NDT fund sales	10,051	8,762	7,845
Investment in NDT funds	(10,087)	(8,997)	(8,113)
Reduction of restricted cash from deconsolidation of business	0	0	(87)
Acquisitions of assets and businesses, net	(41)	(154)	(208)
Proceeds from sales of assets and businesses	52	90	218
Other investing activities	3	10	(58)
Net cash flows used in investing activities	(1,867)	(2,531)	(2,662)
Cash flows from financing activities
Changes in short-term borrowings	320	0	(620)
Proceeds from short-term borrowings with maturities greater than 90 days	0	0	121
Repayments on short-term borrowings with maturities greater than 90 days	0	0	(200)
Issuance of long-term debt	42	15	1,645
Retirement of long-term debt	(813)	(141)	(1,261)
Changes in Exelon intercompany money pool	(100)	46	(1)
Contributions from member	41	155	102
Distributions to member	(899)	(1,001)	(659)
Sale of noncontrolling interest	0	0	396
Other financing activities	(51)	(55)	(54)
Net cash flows provided by (used in) financing activities	(1,460)	(981)	(531)
Increase (Decrease) in cash, cash equivalents and restricted cash	(454)	349	106
Cash, cash equivalents, and restricted cash at beginning of period	903	554	448
Cash, cash equivalents, and restricted cash at end of period	449	903	554
Increase (decrease) in capital expenditures not paid	(34)	(199)	73
Increase (decrease) in PPE related to ARO update	959	(130)	29
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income (loss)	688	664	567
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	1,033	940	850
Deferred income taxes and amortization of investment tax credits	109	259	659
Other non-cash operating activities	265	242	164
Changes in assets and liabilities:
Accounts receivable	(34)	(136)	(59)
Receivables from and payables to affiliates, net	(12)	26	8
Inventories	(16)	1	4
Accounts payable and accrued expenses	(51)	70	(297)
Collateral (posted) received, net	48	11	(26)
Income taxes	95	62	(308)
Pension and non-pension postretirement benefit contributions	(77)	(42)	(41)
Other assets and liabilities	(345)	(348)	6
Net cash flows provided by operating activities	1,703	1,749	1,527
Cash flows from investing activities
Capital expenditures	(1,915)	(2,126)	(2,250)
Other investing activities	29	29	20
Net cash flows used in investing activities	(1,886)	(2,097)	(2,230)
Cash flows from financing activities
Changes in short-term borrowings	130	0	0
Issuance of long-term debt	700	1,350	1,000
Retirement of long-term debt	(300)	(840)	(425)
Dividends paid on common stock	(508)	(459)	(422)
Contributions from parent	250	500	651
Other financing activities	(16)	(17)	(15)
Net cash flows provided by (used in) financing activities	256	534	789
Increase (Decrease) in cash, cash equivalents and restricted cash	73	186	86
Cash, cash equivalents, and restricted cash at beginning of period	330	144	58
Cash, cash equivalents, and restricted cash at end of period	403	330	144
Increase (decrease) in capital expenditures not paid	(37)	11	(61)
Increase (decrease) in PPE related to ARO update	7	7	0
PECO Energy Co [Member]
Cash flows from operating activities
Net income (loss)	528	460	434
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	333	301	286
Gain on sales of assets and businesses	(1)	0	0
Deferred income taxes and amortization of investment tax credits	20	(5)	19
Other non-cash operating activities	38	51	54
Changes in assets and liabilities:
Accounts receivable	(29)	(74)	(44)
Receivables from and payables to affiliates, net	(5)	7	(6)
Inventories	4	(14)	1
Accounts payable and accrued expenses	(11)	(3)	6
Income taxes	(34)	15	34
Pension and non-pension postretirement benefit contributions	(28)	(28)	(24)
Other assets and liabilities	(64)	29	(5)
Net cash flows provided by operating activities	751	739	755
Cash flows from investing activities
Capital expenditures	(939)	(849)	(732)
Changes in Exelon intercompany money pool	(68)	0	131
Other investing activities	(1)	9	4
Net cash flows used in investing activities	(1,008)	(840)	(597)
Cash flows from financing activities
Issuance of long-term debt	325	700	325
Retirement of long-term debt	0	(500)	0
Dividends paid on common stock	(358)	(306)	(288)
Contributions from parent	188	89	16
Other financing activities	(6)	(22)	(3)
Net cash flows provided by (used in) financing activities	149	(39)	50
Increase (Decrease) in cash, cash equivalents and restricted cash	(108)	(140)	208
Cash, cash equivalents, and restricted cash at beginning of period	135	275	67
Cash, cash equivalents, and restricted cash at end of period	27	135	275
Increase (decrease) in capital expenditures not paid	40	(12)	22
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income (loss)	360	313	307
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	502	483	473
Asset impairments	0	0	7
Deferred income taxes and amortization of investment tax credits	130	76	145
Other non-cash operating activities	85	58	65
Changes in assets and liabilities:
Accounts receivable	25	8	(5)
Receivables from and payables to affiliates, net	1	12	(4)
Inventories	(1)	2	(9)
Accounts payable and accrued expenses	(43)	(1)	(15)
Collateral (posted) received, net	(4)	4	0
Income taxes	(67)	(20)	60
Pension and non-pension postretirement benefit contributions	(48)	(54)	(53)
Other assets and liabilities	(192)	(92)	(150)
Net cash flows provided by operating activities	748	789	821
Cash flows from investing activities
Capital expenditures	(1,145)	(959)	(882)
Other investing activities	8	9	7
Net cash flows used in investing activities	(1,137)	(950)	(875)
Cash flows from financing activities
Changes in short-term borrowings	40	(42)	32
Issuance of long-term debt	400	300	300
Retirement of long-term debt	0	0	(41)
Retirement of long-term debt to financing trust	0	0	(250)
Dividends paid on common stock	(224)	(209)	(198)
Contributions from parent	193	109	184
Other financing activities	(8)	(2)	(5)
Net cash flows provided by (used in) financing activities	401	156	22
Increase (Decrease) in cash, cash equivalents and restricted cash	12	(5)	(32)
Cash, cash equivalents, and restricted cash at beginning of period	13	18	50
Cash, cash equivalents, and restricted cash at end of period	25	13	18
Increase (decrease) in capital expenditures not paid	6	50	23
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income (loss)	477	393	355
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	754	740	675
Asset impairments	0	0	52
Deferred income taxes and amortization of investment tax credits	(7)	30	252
Other non-cash operating activities	161	150	65
Changes in assets and liabilities:
Accounts receivable	(39)	(2)	(26)
Receivables from and payables to affiliates, net	3	8	(2)
Inventories	(27)	(14)	(37)
Accounts payable and accrued expenses	(17)	45	(106)
Income taxes	16	34	79
Pension and non-pension postretirement benefit contributions	(25)	(74)	(99)
Other assets and liabilities	(179)	(178)	(258)
Net cash flows provided by operating activities	1,117	1,132	950
Cash flows from investing activities
Capital expenditures	(1,355)	(1,375)	(1,396)
Other investing activities	(3)	4	(1)
Net cash flows used in investing activities	(1,358)	(1,371)	(1,397)
Cash flows from financing activities
Changes in short-term borrowings	154	(296)	328
Proceeds from short-term borrowings with maturities greater than 90 days	0	125	0
Repayments on short-term borrowings with maturities greater than 90 days	(125)	0	(500)
Issuance of long-term debt	485	750	202
Retirement of long-term debt	(157)	(299)	(169)
Changes in Exelon intercompany money pool	12	0	0
Contributions from member	398	385	758
Distributions to member	(526)	(326)	(311)
Other financing activities	(5)	(9)	(2)
Net cash flows provided by (used in) financing activities	236	330	306
Increase (Decrease) in cash, cash equivalents and restricted cash	(5)	91	(141)
Cash, cash equivalents, and restricted cash at beginning of period	186	95	236
Cash, cash equivalents, and restricted cash at end of period	181	186	95
Increase (decrease) in capital expenditures not paid	2	93	(12)
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income (loss)	243	205	198
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	374	385	321
Asset impairments	0	0	14
Deferred income taxes and amortization of investment tax credits	1	(20)	113
Other non-cash operating activities	56	67	1
Changes in assets and liabilities:
Accounts receivable	(22)	(5)	(20)
Receivables from and payables to affiliates, net	5	(17)	0
Inventories	(19)	(6)	(24)
Accounts payable and accrued expenses	(39)	59	(63)
Income taxes	9	(13)	81
Pension and non-pension postretirement benefit contributions	(14)	(17)	(72)
Other assets and liabilities	(82)	(164)	(142)
Net cash flows provided by operating activities	512	474	407
Cash flows from investing activities
Capital expenditures	(626)	(656)	(628)
Other investing activities	3	2	0
Net cash flows used in investing activities	(623)	(654)	(628)
Cash flows from financing activities
Changes in short-term borrowings	42	14	3
Issuance of long-term debt	260	200	202
Retirement of long-term debt	(125)	(14)	(13)
Dividends paid on common stock	(213)	(169)	(133)
Contributions from parent	160	166	161
Other financing activities	(3)	(4)	(1)
Net cash flows provided by (used in) financing activities	121	193	219
Increase (Decrease) in cash, cash equivalents and restricted cash	10	13	(2)
Cash, cash equivalents, and restricted cash at beginning of period	53	40	42
Cash, cash equivalents, and restricted cash at end of period	63	53	40
Increase (decrease) in capital expenditures not paid	39	20	5
Delmarva Power & Light Company [Member]
Cash flows from operating activities
Net income (loss)	147	120	121
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	184	182	167
Asset impairments	0	0	6
Deferred income taxes and amortization of investment tax credits	(7)	24	89
Other non-cash operating activities	27	24	9
Changes in assets and liabilities:
Accounts receivable	(5)	8	(22)
Receivables from and payables to affiliates, net	(5)	(9)	11
Inventories	(6)	(3)	(5)
Accounts payable and accrued expenses	3	11	(8)
Income taxes	12	2	26
Pension and non-pension postretirement benefit contributions	(1)	0	(2)
Other assets and liabilities	(55)	(7)	(71)
Net cash flows provided by operating activities	294	352	321
Cash flows from investing activities
Capital expenditures	(348)	(364)	(428)
Other investing activities	1	2	(1)
Net cash flows used in investing activities	(347)	(362)	(429)
Cash flows from financing activities
Changes in short-term borrowings	56	(216)	216
Issuance of long-term debt	75	200	0
Retirement of long-term debt	(12)	(4)	(40)
Dividends paid on common stock	(139)	(96)	(112)
Contributions from parent	63	150	0
Other financing activities	(1)	(2)	0
Net cash flows provided by (used in) financing activities	42	32	64
Increase (Decrease) in cash, cash equivalents and restricted cash	(11)	22	(44)
Cash, cash equivalents, and restricted cash at beginning of period	24	2	46
Cash, cash equivalents, and restricted cash at end of period	13	24	2
Increase (decrease) in capital expenditures not paid	(4)	22	4
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income (loss)	99	75	77
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	157	136	146
Asset impairments	0	0	7
Deferred income taxes and amortization of investment tax credits	3	25	32
Other non-cash operating activities	22	24	17
Changes in assets and liabilities:
Accounts receivable	(13)	(8)	14
Receivables from and payables to affiliates, net	(6)	1	0
Inventories	(1)	(4)	(7)
Accounts payable and accrued expenses	26	(7)	(2)
Income taxes	2	(2)	(11)
Pension and non-pension postretirement benefit contributions	(1)	(6)	(20)
Other assets and liabilities	(27)	(6)	(47)
Net cash flows provided by operating activities	261	228	206
Cash flows from investing activities
Capital expenditures	(375)	(335)	(312)
Other investing activities	(1)	1	(1)
Net cash flows used in investing activities	(376)	(334)	(313)
Cash flows from financing activities
Changes in short-term borrowings	56	(94)	108
Proceeds from short-term borrowings with maturities greater than 90 days	0	125	0
Repayments on short-term borrowings with maturities greater than 90 days	(125)	0	0
Issuance of long-term debt	150	350	0
Retirement of long-term debt	(18)	(281)	(35)
Dividends paid on common stock	(124)	(59)	(68)
Contributions from parent	175	67	0
Other financing activities	(1)	(3)	0
Net cash flows provided by (used in) financing activities	113	105	5
Increase (Decrease) in cash, cash equivalents and restricted cash	(2)	(1)	(102)
Cash, cash equivalents, and restricted cash at beginning of period	30	31	133
Cash, cash equivalents, and restricted cash at end of period	28	30	31
Increase (decrease) in capital expenditures not paid	$ (29)	$ 46	$ (13)