Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities
Net income (loss)	$ 1,441	$ 1,519
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	6,204	4,419
Asset impairments	541	567
Gain on sales of assets and businesses	(147)	(16)
Deferred income taxes and amortization of investment tax credits	(45)	164
Net fair value changes related to derivatives	(1,244)	(448)
Net realized and unrealized (gains) losses on NDT funds	(383)	(59)
Unrealized loss on equity investments	83	0
Other non-cash operating activities	(293)	988
Changes in assets and liabilities:
Accounts receivable	(254)	1,195
Inventories	(101)	(67)
Accounts payable and accrued expenses	354	(519)
Option premiums paid, net	(186)	(131)
Collateral received (posted), net	2,111	644
Income taxes	250	(31)
Pension and non-pension postretirement benefit contributions	(602)	(580)
Other assets and liabilities	(3,588)	(3,423)
Net cash flows provided by operating activities	4,141	4,222
Cash flows from investing activities
Capital expenditures	(5,970)	(5,606)
Proceeds from NDT fund sales	5,766	3,370
Investment in NDT funds	(5,900)	(3,438)
Collection of deferred purchase price	3,052	2,518
Proceeds from sales of assets and businesses	801	46
Other investing activities	40	(2)
Net cash flows provided by (used in) investing activities	(2,211)	(3,112)
Cash flows from financing activities
Changes in short-term borrowings	(744)	(689)
Proceeds from short-term borrowings with maturities greater than 90 days	1,380	500
Issuance of long-term debt	3,406	6,756
Retirement of long-term debt	(1,618)	(5,158)
Dividends paid on common stock	(1,121)	(1,119)
Acquisition of CENG noncontrolling interest	(885)	0
Proceeds from employee stock plans	63	62
Other financing activities	(93)	(104)
Net cash flows provided by (used in) financing activities	388	248
Increase (decrease) in cash, restricted cash, and cash equivalents	2,318	1,358
Cash, restricted cash, and cash equivalents at beginning of period	1,166	1,122
Cash, restricted cash, and cash equivalents at end of period	3,484	2,480
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(334)	(11)
Increase in deferred purchase price	2,933	3,275
Increase in PPE related to ARO update	574	775
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income (loss)	(122)	485
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	3,951	2,266
Asset impairments	537	552
Gain on sales of assets and businesses	(144)	(12)
Deferred income taxes and amortization of investment tax credits	(204)	(51)
Net fair value changes related to derivatives	(1,244)	(448)
Net realized and unrealized (gains) losses on NDT funds	(383)	(59)
Unrealized loss on equity investments	83	0
Other non-cash operating activities	(582)	293
Changes in assets and liabilities:
Accounts receivable	(207)	1,463
Change in Receivables From Payables To Affiliates, Net	82	75
Inventories	(29)	(65)
Accounts payable and accrued expenses	357	(619)
Option premiums paid, net	(186)	(131)
Collateral received (posted), net	1,974	640
Income taxes	177	112
Pension and non-pension postretirement benefit contributions	(237)	(249)
Other assets and liabilities	(2,849)	(2,889)
Net cash flows provided by operating activities	974	1,363
Cash flows from investing activities
Capital expenditures	(1,086)	(1,212)
Proceeds from NDT fund sales	5,766	3,370
Investment in NDT funds	(5,900)	(3,438)
Collection of deferred purchase price	3,052	2,518
Proceeds from sales of assets and businesses	802	46
Other investing activities	5	5
Net cash flows provided by (used in) investing activities	2,639	1,289
Cash flows from financing activities
Changes in short-term borrowings	(340)	(280)
Proceeds from short-term borrowings with maturities greater than 90 days	880	500
Issuance of long-term debt	152	2,405
Retirement of long-term debt	(89)	(3,613)
Changes in Exelon/PHI intercompany money pool	(285)	0
Acquisition of CENG noncontrolling interest	(885)	0
Distributions to member	(1,373)	(1,406)
Contributions from member	64	64
Other financing activities	(45)	(48)
Net cash flows provided by (used in) financing activities	(1,921)	(2,378)
Increase (decrease) in cash, restricted cash, and cash equivalents	1,692	274
Cash, restricted cash, and cash equivalents at beginning of period	327	449
Cash, restricted cash, and cash equivalents at end of period	2,019	723
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(77)	(77)
Increase in deferred purchase price	2,933	3,275
Increase in PPE related to ARO update	550	775
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income (loss)	609	304
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	893	841
Asset impairments	0	15
Deferred income taxes and amortization of investment tax credits	211	205
Other non-cash operating activities	95	354
Changes in assets and liabilities:
Accounts receivable	(72)	(104)
Change in Receivables From Payables To Affiliates, Net	(16)	(13)
Inventories	(6)	(2)
Accounts payable and accrued expenses	(36)	21
Collateral received (posted), net	68	3
Income taxes	(9)	(22)
Pension and non-pension postretirement benefit contributions	(176)	(145)
Other assets and liabilities	(376)	(380)
Net cash flows provided by operating activities	1,185	1,077
Cash flows from investing activities
Capital expenditures	(1,723)	(1,583)
Other investing activities	20	0
Net cash flows provided by (used in) investing activities	(1,703)	(1,583)
Cash flows from financing activities
Changes in short-term borrowings	(323)	11
Issuance of long-term debt	1,150	1,000
Retirement of long-term debt	(350)	(500)
Dividends paid on common stock	(380)	(374)
Contributions from parent	593	488
Other financing activities	(16)	(14)
Net cash flows provided by (used in) financing activities	674	611
Increase (decrease) in cash, restricted cash, and cash equivalents	156	105
Cash, restricted cash, and cash equivalents at beginning of period	405	403
Cash, restricted cash, and cash equivalents at end of period	561	508
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(118)	49
PECO Energy Co [Member]
Cash flows from operating activities
Net income (loss)	383	317
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	259
Deferred income taxes and amortization of investment tax credits	19	(5)
Other non-cash operating activities	4	27
Changes in assets and liabilities:
Accounts receivable	47	(2)
Change in Receivables From Payables To Affiliates, Net	16	(7)
Inventories	(21)	(3)
Accounts payable and accrued expenses	(23)	32
Income taxes	55	48
Pension and non-pension postretirement benefit contributions	(15)	(18)
Other assets and liabilities	(87)	(13)
Net cash flows provided by operating activities	637	635
Cash flows from investing activities
Capital expenditures	(878)	(824)
Changes in Exelon/PHI intercompany money pool	0	68
Other investing activities	5	4
Net cash flows provided by (used in) investing activities	(873)	(752)
Cash flows from financing activities
Issuance of long-term debt	750	350
Retirement of long-term debt	(300)	0
Changes in Exelon/PHI intercompany money pool	(40)	0
Dividends paid on common stock	(254)	(255)
Contributions from parent	414	248
Other financing activities	(8)	(4)
Net cash flows provided by (used in) financing activities	562	339
Increase (decrease) in cash, restricted cash, and cash equivalents	326	222
Cash, restricted cash, and cash equivalents at beginning of period	26	27
Cash, restricted cash, and cash equivalents at end of period	352	249
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	25	28
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income (loss)	290	273
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	434	405
Deferred income taxes and amortization of investment tax credits	7	35
Other non-cash operating activities	77	82
Changes in assets and liabilities:
Accounts receivable	92	(19)
Change in Receivables From Payables To Affiliates, Net	(13)	(27)
Inventories	(30)	2
Accounts payable and accrued expenses	14	53
Income taxes	3	46
Pension and non-pension postretirement benefit contributions	(76)	(74)
Other assets and liabilities	(129)	(50)
Net cash flows provided by operating activities	669	726
Cash flows from investing activities
Capital expenditures	(907)	(838)
Other investing activities	13	0
Net cash flows provided by (used in) investing activities	(894)	(838)
Cash flows from financing activities
Changes in short-term borrowings	0	(76)
Issuance of long-term debt	600	400
Retirement of long-term debt	(300)	0
Dividends paid on common stock	(219)	(186)
Contributions from parent	257	284
Other financing activities	(6)	(8)
Net cash flows provided by (used in) financing activities	332	414
Increase (decrease) in cash, restricted cash, and cash equivalents	107	302
Cash, restricted cash, and cash equivalents at beginning of period	145	25
Cash, restricted cash, and cash equivalents at end of period	252	327
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(70)	7
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income (loss)	535	418
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	614	585
Deferred income taxes and amortization of investment tax credits	0	(99)
Other non-cash operating activities	(35)	115
Changes in assets and liabilities:
Accounts receivable	(112)	(121)
Change in Receivables From Payables To Affiliates, Net	(19)	(26)
Inventories	(13)	(2)
Accounts payable and accrued expenses	19	57
Income taxes	17	(14)
Pension and non-pension postretirement benefit contributions	(43)	(35)
Other assets and liabilities	(120)	(61)
Net cash flows provided by operating activities	843	817
Cash flows from investing activities
Capital expenditures	(1,299)	(1,072)
Other investing activities	(1)	3
Net cash flows provided by (used in) investing activities	(1,300)	(1,069)
Cash flows from financing activities
Changes in short-term borrowings	(81)	(208)
Issuance of long-term debt	750	601
Retirement of long-term debt	(255)	(119)
Changes in Exelon/PHI intercompany money pool	(5)	9
Distributions to member	(605)	(451)
Contributions from member	667	493
Other financing activities	(12)	(10)
Net cash flows provided by (used in) financing activities	459	315
Increase (decrease) in cash, restricted cash, and cash equivalents	2	63
Cash, restricted cash, and cash equivalents at beginning of period	160	181
Cash, restricted cash, and cash equivalents at end of period	162	244
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(74)	(5)
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income (loss)	264	227
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	302	282
Deferred income taxes and amortization of investment tax credits	12	(36)
Other non-cash operating activities	(54)	6
Changes in assets and liabilities:
Accounts receivable	(57)	(61)
Change in Receivables From Payables To Affiliates, Net	(2)	(23)
Inventories	(6)	2
Accounts payable and accrued expenses	14	36
Income taxes	(10)	(11)
Pension and non-pension postretirement benefit contributions	(9)	(8)
Other assets and liabilities	(114)	15
Net cash flows provided by operating activities	340	429
Cash flows from investing activities
Capital expenditures	(641)	(512)
Changes in Exelon/PHI intercompany money pool	0	(117)
Other investing activities	(2)	(3)
Net cash flows provided by (used in) investing activities	(643)	(632)
Cash flows from financing activities
Changes in short-term borrowings	5	(82)
Issuance of long-term debt	275	300
Retirement of long-term debt	(1)	(2)
Dividends paid on common stock	(221)	(174)
Contributions from parent	244	262
Other financing activities	(4)	(6)
Net cash flows provided by (used in) financing activities	298	298
Increase (decrease) in cash, restricted cash, and cash equivalents	(5)	95
Cash, restricted cash, and cash equivalents at beginning of period	65	63
Cash, restricted cash, and cash equivalents at end of period	60	158
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(16)	(23)
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income (loss)	135	91
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	143
Deferred income taxes and amortization of investment tax credits	5	(20)
Other non-cash operating activities	(2)	47
Changes in assets and liabilities:
Accounts receivable	26	3
Change in Receivables From Payables To Affiliates, Net	(12)	(5)
Inventories	(5)	(3)
Accounts payable and accrued expenses	17	21
Income taxes	19	(12)
Pension and non-pension postretirement benefit contributions	(1)	(1)
Other assets and liabilities	(7)	(25)
Net cash flows provided by operating activities	332	239
Cash flows from investing activities
Capital expenditures	(320)	(278)
Other investing activities	1	(3)
Net cash flows provided by (used in) investing activities	(319)	(281)
Cash flows from financing activities
Changes in short-term borrowings	(124)	(56)
Issuance of long-term debt	125	178
Retirement of long-term debt	0	(79)
Dividends paid on common stock	(106)	(99)
Contributions from parent	120	112
Other financing activities	(4)	(1)
Net cash flows provided by (used in) financing activities	11	55
Increase (decrease) in cash, restricted cash, and cash equivalents	24	13
Cash, restricted cash, and cash equivalents at beginning of period	15	13
Cash, restricted cash, and cash equivalents at end of period	39	26
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(24)	8
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income (loss)	141	106
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	133	134
Deferred income taxes and amortization of investment tax credits	(20)	(40)
Other non-cash operating activities	(8)	34
Changes in assets and liabilities:
Accounts receivable	(81)	(62)
Change in Receivables From Payables To Affiliates, Net	0	2
Inventories	(1)	0
Accounts payable and accrued expenses	(3)	16
Income taxes	10	4
Pension and non-pension postretirement benefit contributions	(3)	(3)
Other assets and liabilities	15	(53)
Net cash flows provided by operating activities	183	138
Cash flows from investing activities
Capital expenditures	(336)	(281)
Other investing activities	1	5
Net cash flows provided by (used in) investing activities	(335)	(276)
Cash flows from financing activities
Changes in short-term borrowings	38	(70)
Issuance of long-term debt	350	123
Retirement of long-term debt	(254)	(38)
Changes in Exelon/PHI intercompany money pool	0	117
Dividends paid on common stock	(280)	(111)
Contributions from parent	303	117
Other financing activities	(5)	(1)
Net cash flows provided by (used in) financing activities	152	137
Increase (decrease) in cash, restricted cash, and cash equivalents	0	(1)
Cash, restricted cash, and cash equivalents at beginning of period	30	28
Cash, restricted cash, and cash equivalents at end of period	30	27
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	$ (34)	$ 9