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