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)