Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities
Net income (loss)	$ (264)	$ 376
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	2,104	1,378
Asset impairments	1	8
Gain on sales of assets and businesses	(71)	0
Deferred income taxes and amortization of investment tax credits	(142)	(245)
Net fair value changes related to derivatives	(178)	(132)
Net realized and unrealized (gains) losses on NDT funds	(118)	651
Unrealized loss on equity investments	23	0
Other non-cash operating activities	(170)	273
Changes in assets and liabilities:
Accounts receivable	(372)	800
Inventories	77	81
Accounts payable and accrued expenses	(176)	(976)
Option premiums received (paid), net	16	(38)
Collateral received (posted), net	273	(21)
Income taxes	113	(56)
Pension and non-pension postretirement benefit contributions	(537)	(531)
Other assets and liabilities	(1,840)	(488)
Net cash flows provided by operating activities	(1,261)	1,080
Cash flows from investing activities
Capital expenditures	(2,140)	(2,016)
Proceeds from NDT fund sales	2,908	1,183
Investment in NDT funds	(2,939)	(1,234)
Collection of deferred purchase price	1,574	0
Proceeds from sales of assets and businesses	680	0
Other investing activities	12	(8)
Net cash flows provided by (used in) investing activities	95	(2,075)
Cash flows from financing activities
Changes in short-term borrowings	597	109
Proceeds from short-term borrowings with maturities greater than 90 days	500	500
Issuance of long-term debt	1,705	2,652
Retirement of long-term debt	(79)	(1,032)
Dividends paid on common stock	(374)	(373)
Proceeds from employee stock plans	31	30
Other financing activities	(46)	(21)
Net cash flows provided by (used in) financing activities	2,334	1,865
Increase (Decrease) in cash, restricted cash, and cash equivalents	1,168	870
Cash, restricted cash, and cash equivalents at beginning of period	1,166	1,122
Cash, restricted cash, and cash equivalents at end of period	2,334	1,992
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(324)	(180)
Increase in deferred purchase price	1,339	0
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income (loss)	(769)	(161)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	1,346	661
Asset impairments	1	8
Gain on sales of assets and businesses	(71)	0
Deferred income taxes and amortization of investment tax credits	(123)	(329)
Net fair value changes related to derivatives	(178)	(127)
Net realized and unrealized (gains) losses on NDT funds	(118)	651
Unrealized loss on equity investments	23	0
Other non-cash operating activities	(202)	205
Changes in assets and liabilities:
Accounts receivable	(453)	787
Receivables from and payables to affiliates, net	59	34
Inventories	50	39
Accounts payable and accrued expenses	208	(614)
Option premiums received (paid), net	16	(38)
Collateral received (posted), net	270	(22)
Income taxes	(55)	(58)
Pension and non-pension postretirement benefit contributions	(205)	(232)
Other assets and liabilities	(1,411)	(184)
Net cash flows provided by operating activities	(1,612)	620
Cash flows from investing activities
Capital expenditures	(382)	(558)
Proceeds from NDT fund sales	2,908	1,183
Investment in NDT funds	(2,939)	(1,234)
Collection of deferred purchase price	1,574	0
Proceeds from sales of assets and businesses	680	0
Changes in Exelon/PHI intercompany money pool	0	(254)
Other investing activities	(2)	(8)
Net cash flows provided by (used in) investing activities	1,839	(871)
Cash flows from financing activities
Changes in short-term borrowings	997	275
Proceeds from short-term borrowings with maturities greater than 90 days	0	500
Issuance of long-term debt	1	1,502
Retirement of long-term debt	(35)	(1,028)
Changes in Exelon/PHI intercompany money pool	(285)	0
Distributions to member	(458)	(468)
Other financing activities	(12)	(8)
Net cash flows provided by (used in) financing activities	208	773
Increase (Decrease) in cash, restricted cash, and cash equivalents	435	522
Cash, restricted cash, and cash equivalents at beginning of period	327	449
Cash, restricted cash, and cash equivalents at end of period	762	971
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(37)	(56)
Increase in deferred purchase price	1,339	0
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income (loss)	197	168
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	292	273
Deferred income taxes and amortization of investment tax credits	63	42
Other non-cash operating activities	(9)	16
Changes in assets and liabilities:
Accounts receivable	23	9
Receivables from and payables to affiliates, net	(15)	(6)
Inventories	(1)	(2)
Accounts payable and accrued expenses	(176)	(147)
Collateral received (posted), net	5	3
Income taxes	(23)	(7)
Pension and non-pension postretirement benefit contributions	(171)	(143)
Other assets and liabilities	(159)	(132)
Net cash flows provided by operating activities	26	74
Cash flows from investing activities
Capital expenditures	(613)	(506)
Other investing activities	7	5
Net cash flows provided by (used in) investing activities	(606)	(501)
Cash flows from financing activities
Changes in short-term borrowings	(188)	(130)
Issuance of long-term debt	700	1,000
Dividends paid on common stock	(127)	(125)
Contributions from parent	198	125
Other financing activities	(9)	(13)
Net cash flows provided by (used in) financing activities	574	857
Increase (Decrease) in cash, restricted cash, and cash equivalents	(6)	430
Cash, restricted cash, and cash equivalents at beginning of period	405	403
Cash, restricted cash, and cash equivalents at end of period	399	833
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(107)	(5)
PECO Energy Co [Member]
Cash flows from operating activities
Net income (loss)	167	140
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	86	86
Deferred income taxes and amortization of investment tax credits	6	2
Other non-cash operating activities	12	22
Changes in assets and liabilities:
Accounts receivable	(5)	14
Receivables from and payables to affiliates, net	(2)	(3)
Inventories	13	15
Accounts payable and accrued expenses	(36)	(45)
Income taxes	3	14
Pension and non-pension postretirement benefit contributions	(16)	(16)
Other assets and liabilities	(103)	(84)
Net cash flows provided by operating activities	125	145
Cash flows from investing activities
Capital expenditures	(295)	(259)
Changes in Exelon/PHI intercompany money pool	(48)	(22)
Other investing activities	1	1
Net cash flows provided by (used in) investing activities	(342)	(280)
Cash flows from financing activities
Issuance of long-term debt	375	0
Changes in Exelon/PHI intercompany money pool	(40)	0
Dividends paid on common stock	(85)	(85)
Contributions from parent	0	231
Other financing activities	(4)	0
Net cash flows provided by (used in) financing activities	246	146
Increase (Decrease) in cash, restricted cash, and cash equivalents	29	11
Cash, restricted cash, and cash equivalents at beginning of period	26	27
Cash, restricted cash, and cash equivalents at end of period	55	38
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(44)	(11)
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income (loss)	209	181
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	152	143
Deferred income taxes and amortization of investment tax credits	(4)	33
Other non-cash operating activities	2	(8)
Changes in assets and liabilities:
Accounts receivable	12	(28)
Receivables from and payables to affiliates, net	(15)	(13)
Inventories	9	20
Accounts payable and accrued expenses	(59)	(9)
Income taxes	(9)	7
Pension and non-pension postretirement benefit contributions	(65)	(64)
Other assets and liabilities	(103)	10
Net cash flows provided by operating activities	129	272
Cash flows from investing activities
Capital expenditures	(336)	(283)
Other investing activities	2	(6)
Net cash flows provided by (used in) investing activities	(334)	(289)
Cash flows from financing activities
Changes in short-term borrowings	156	66
Dividends paid on common stock	(74)	(62)
Net cash flows provided by (used in) financing activities	82	4
Increase (Decrease) in cash, restricted cash, and cash equivalents	(123)	(13)
Cash, restricted cash, and cash equivalents at beginning of period	145	25
Cash, restricted cash, and cash equivalents at end of period	22	12
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(80)	(35)
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income (loss)	128	108
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	210	194
Deferred income taxes and amortization of investment tax credits	4	(4)
Other non-cash operating activities	(25)	7
Changes in assets and liabilities:
Accounts receivable	56	36
Receivables from and payables to affiliates, net	(18)	(17)
Inventories	5	8
Accounts payable and accrued expenses	(24)	(16)
Income taxes	3	15
Pension and non-pension postretirement benefit contributions	(36)	(27)
Other assets and liabilities	(94)	(72)
Net cash flows provided by operating activities	209	232
Cash flows from investing activities
Capital expenditures	(456)	(376)
Other investing activities	1	1
Net cash flows provided by (used in) investing activities	(455)	(375)
Cash flows from financing activities
Changes in short-term borrowings	(368)	(100)
Issuance of long-term debt	625	150
Retirement of long-term debt	(44)	(6)
Changes in Exelon/PHI intercompany money pool	3	7
Distributions to member	(81)	(134)
Contributions from member	560	144
Other financing activities	(5)	(1)
Net cash flows provided by (used in) financing activities	690	60
Increase (Decrease) in cash, restricted cash, and cash equivalents	444	(83)
Cash, restricted cash, and cash equivalents at beginning of period	160	181
Cash, restricted cash, and cash equivalents at end of period	604	98
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(33)	(57)
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income (loss)	59	52
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	102	95
Deferred income taxes and amortization of investment tax credits	4	(2)
Other non-cash operating activities	(25)	(11)
Changes in assets and liabilities:
Accounts receivable	26	14
Receivables from and payables to affiliates, net	(9)	(11)
Inventories	1	3
Accounts payable and accrued expenses	0	6
Income taxes	2	6
Pension and non-pension postretirement benefit contributions	(5)	(4)
Other assets and liabilities	(58)	(38)
Net cash flows provided by operating activities	97	110
Cash flows from investing activities
Capital expenditures	(220)	(180)
Changes in Exelon/PHI intercompany money pool	0	(114)
Other investing activities	1	(4)
Net cash flows provided by (used in) investing activities	(219)	(298)
Cash flows from financing activities
Changes in short-term borrowings	(35)	(82)
Issuance of long-term debt	150	150
Dividends paid on common stock	(28)	(28)
Contributions from parent	138	137
Other financing activities	(1)	(1)
Net cash flows provided by (used in) financing activities	224	176
Increase (Decrease) in cash, restricted cash, and cash equivalents	102	(12)
Cash, restricted cash, and cash equivalents at beginning of period	65	63
Cash, restricted cash, and cash equivalents at end of period	167	51
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(16)	(43)
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income (loss)	56	45
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	53	48
Deferred income taxes and amortization of investment tax credits	2	0
Other non-cash operating activities	(1)	2
Changes in assets and liabilities:
Accounts receivable	15	14
Receivables from and payables to affiliates, net	(11)	(9)
Inventories	2	3
Accounts payable and accrued expenses	11	4
Income taxes	3	7
Other assets and liabilities	(26)	(10)
Net cash flows provided by operating activities	104	104
Cash flows from investing activities
Capital expenditures	(112)	(95)
Other investing activities	0	(4)
Net cash flows provided by (used in) investing activities	(112)	(99)
Cash flows from financing activities
Changes in short-term borrowings	(146)	(2)
Issuance of long-term debt	125	0
Changes in Exelon/PHI intercompany money pool	0	37
Dividends paid on common stock	(40)	(52)
Contributions from parent	120	6
Other financing activities	(2)	0
Net cash flows provided by (used in) financing activities	57	(11)
Increase (Decrease) in cash, restricted cash, and cash equivalents	49	(6)
Cash, restricted cash, and cash equivalents at beginning of period	15	13
Cash, restricted cash, and cash equivalents at end of period	64	7
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(15)	(9)
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income (loss)	14	13
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	47	43
Deferred income taxes and amortization of investment tax credits	(1)	(1)
Other non-cash operating activities	(7)	4
Changes in assets and liabilities:
Accounts receivable	13	11
Receivables from and payables to affiliates, net	1	3
Inventories	3	2
Accounts payable and accrued expenses	(11)	3
Income taxes	1	2
Pension and non-pension postretirement benefit contributions	(3)	(2)
Other assets and liabilities	(3)	(22)
Net cash flows provided by operating activities	54	56
Cash flows from investing activities
Capital expenditures	(123)	(101)
Other investing activities	0	6
Net cash flows provided by (used in) investing activities	(123)	(95)
Cash flows from financing activities
Changes in short-term borrowings	(187)	(16)
Issuance of long-term debt	350	0
Retirement of long-term debt	(44)	(5)
Changes in Exelon/PHI intercompany money pool	0	77
Dividends paid on common stock	(14)	(23)
Contributions from parent	303	1
Other financing activities	(3)	0
Net cash flows provided by (used in) financing activities	405	34
Increase (Decrease) in cash, restricted cash, and cash equivalents	336	(5)
Cash, restricted cash, and cash equivalents at beginning of period	30	28
Cash, restricted cash, and cash equivalents at end of period	366	23
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	$ (2)	$ (4)