Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities
Net income (loss)	$ 211	$ 950
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	4,180	2,741
Asset impairments	500	33
Gain on sales of assets and businesses	(83)	(13)
Deferred income taxes and amortization of investment tax credits	(163)	33
Net fair value changes related to derivatives	(490)	(194)
Net realized and unrealized (gains) losses on NDT funds	(376)	196
Unrealized loss on equity investments	(96)	0
Other non-cash operating activities	(331)	671
Changes in assets and liabilities:
Accounts receivable	(16)	1,318
Inventories	1	(14)
Accounts payable and accrued expenses	(87)	(798)
Option premiums received (paid), net	2	(102)
Collateral received (posted), net	957	340
Income taxes	190	(114)
Pension and non-pension postretirement benefit contributions	(559)	(558)
Other assets and liabilities	(2,702)	(1,809)
Net cash flows provided by operating activities	1,138	2,680
Cash flows from investing activities
Capital expenditures	(4,040)	(3,773)
Proceeds from NDT fund sales	4,438	2,488
Investment in NDT funds	(4,538)	(2,540)
Collection of deferred purchase price	2,209	1,102
Proceeds from sales of assets and businesses	724	0
Other investing activities	17	4
Net cash flows provided by (used in) investing activities	(1,190)	(2,719)
Cash flows from financing activities
Changes in short-term borrowings	(666)	(751)
Proceeds from short-term borrowings with maturities greater than 90 days	500	500
Issuance of long-term debt	2,455	6,526
Retirement of long-term debt	(630)	(3,894)
Dividends paid on common stock	(747)	(746)
Proceeds from employee stock plans	47	46
Other financing activities	(64)	(84)
Net cash flows provided by (used in) financing activities	895	1,597
Increase (decrease) in cash, restricted cash, and cash equivalents	843	1,558
Cash, restricted cash, and cash equivalents at beginning of period	1,166	1,122
Cash, restricted cash, and cash equivalents at end of period	2,009	2,680
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(313)	(105)
Increase in deferred purchase price	1,958	1,754
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income (loss)	(756)	368
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	2,686	1,320
Asset impairments	493	18
Gain on sales of assets and businesses	(79)	(12)
Deferred income taxes and amortization of investment tax credits	(142)	(54)
Net fair value changes related to derivatives	(490)	(193)
Net realized and unrealized (gains) losses on NDT funds	(376)	196
Unrealized loss on equity investments	(96)	0
Other non-cash operating activities	(421)	136
Changes in assets and liabilities:
Accounts receivable	(90)	1,443
Receivables from and payables to affiliates, net	43	68
Inventories	4	(34)
Accounts payable and accrued expenses	154	(666)
Option premiums received (paid), net	2	(102)
Collateral received (posted), net	955	342
Income taxes	(1)	26
Pension and non-pension postretirement benefit contributions	(212)	(243)
Other assets and liabilities	(2,031)	(1,332)
Net cash flows provided by operating activities	(357)	1,281
Cash flows from investing activities
Capital expenditures	(719)	(930)
Proceeds from NDT fund sales	4,438	2,488
Investment in NDT funds	(4,538)	(2,540)
Collection of deferred purchase price	2,209	1,102
Proceeds from sales of assets and businesses	724	0
Other investing activities	(8)	6
Net cash flows provided by (used in) investing activities	2,106	126
Cash flows from financing activities
Changes in short-term borrowings	(340)	(220)
Proceeds from short-term borrowings with maturities greater than 90 days	0	500
Issuance of long-term debt	151	2,403
Retirement of long-term debt	(56)	(2,936)
Changes in Exelon/PHI intercompany money pool	(285)	0
Distributions to member	(916)	(937)
Other financing activities	(29)	(30)
Net cash flows provided by (used in) financing activities	(1,475)	(1,220)
Increase (decrease) in cash, restricted cash, and cash equivalents	274	187
Cash, restricted cash, and cash equivalents at beginning of period	327	449
Cash, restricted cash, and cash equivalents at end of period	601	636
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(66)	(108)
Increase in deferred purchase price	1,958	1,754
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income (loss)	390	107
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	589	547
Asset impairments	0	15
Deferred income taxes and amortization of investment tax credits	143	129
Other non-cash operating activities	23	283
Changes in assets and liabilities:
Accounts receivable	(48)	(92)
Receivables from and payables to affiliates, net	5	(6)
Inventories	(2)	(7)
Accounts payable and accrued expenses	(45)	4
Collateral received (posted), net	2	(3)
Income taxes	(34)	(90)
Pension and non-pension postretirement benefit contributions	(173)	(144)
Other assets and liabilities	(292)	(245)
Net cash flows provided by operating activities	558	498
Cash flows from investing activities
Capital expenditures	(1,162)	(1,029)
Other investing activities	12	(4)
Net cash flows provided by (used in) investing activities	(1,150)	(1,033)
Cash flows from financing activities
Changes in short-term borrowings	(290)	(130)
Issuance of long-term debt	700	1,000
Dividends paid on common stock	(253)	(249)
Contributions from parent	395	249
Other financing activities	(11)	(14)
Net cash flows provided by (used in) financing activities	541	856
Increase (decrease) in cash, restricted cash, and cash equivalents	(51)	321
Cash, restricted cash, and cash equivalents at beginning of period	405	403
Cash, restricted cash, and cash equivalents at end of period	354	724
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(93)	18
PECO Energy Co [Member]
Cash flows from operating activities
Net income (loss)	271	178
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	173	173
Deferred income taxes and amortization of investment tax credits	21	6
Other non-cash operating activities	(5)	25
Changes in assets and liabilities:
Accounts receivable	86	22
Receivables from and payables to affiliates, net	2	3
Inventories	3	10
Accounts payable and accrued expenses	(46)	27
Income taxes	24	15
Pension and non-pension postretirement benefit contributions	(15)	(18)
Other assets and liabilities	(140)	(48)
Net cash flows provided by operating activities	374	393
Cash flows from investing activities
Capital expenditures	(577)	(512)
Changes in Exelon/PHI intercompany money pool	0	68
Other investing activities	4	3
Net cash flows provided by (used in) investing activities	(573)	(441)
Cash flows from financing activities
Issuance of long-term debt	375	350
Changes in Exelon/PHI intercompany money pool	(40)	0
Dividends paid on common stock	(169)	(170)
Contributions from parent	395	231
Other financing activities	(4)	(3)
Net cash flows provided by (used in) financing activities	557	408
Increase (decrease) in cash, restricted cash, and cash equivalents	358	360
Cash, restricted cash, and cash equivalents at beginning of period	26	27
Cash, restricted cash, and cash equivalents at end of period	384	387
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(16)	42
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income (loss)	254	219
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	293	272
Deferred income taxes and amortization of investment tax credits	11	22
Other non-cash operating activities	28	50
Changes in assets and liabilities:
Accounts receivable	73	19
Receivables from and payables to affiliates, net	(19)	(26)
Inventories	(9)	10
Accounts payable and accrued expenses	(51)	(15)
Collateral received (posted), net	2	0
Income taxes	(27)	26
Pension and non-pension postretirement benefit contributions	(71)	(68)
Other assets and liabilities	(96)	(5)
Net cash flows provided by operating activities	388	504
Cash flows from investing activities
Capital expenditures	(620)	(548)
Other investing activities	10	(4)
Net cash flows provided by (used in) investing activities	(610)	(552)
Cash flows from financing activities
Changes in short-term borrowings	0	(76)
Issuance of long-term debt	600	400
Dividends paid on common stock	(146)	(123)
Contributions from parent	0	26
Other financing activities	(6)	(8)
Net cash flows provided by (used in) financing activities	448	219
Increase (decrease) in cash, restricted cash, and cash equivalents	226	171
Cash, restricted cash, and cash equivalents at beginning of period	145	25
Cash, restricted cash, and cash equivalents at end of period	371	196
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(71)	(14)
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income (loss)	269	202
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	404	385
Deferred income taxes and amortization of investment tax credits	10	(74)
Other non-cash operating activities	(50)	107
Changes in assets and liabilities:
Accounts receivable	(30)	(64)
Receivables from and payables to affiliates, net	(22)	(22)
Inventories	3	6
Accounts payable and accrued expenses	(35)	14
Income taxes	(1)	(30)
Pension and non-pension postretirement benefit contributions	(40)	(31)
Other assets and liabilities	(131)	(146)
Net cash flows provided by operating activities	377	347
Cash flows from investing activities
Capital expenditures	(889)	(686)
Other investing activities	(2)	2
Net cash flows provided by (used in) investing activities	(891)	(684)
Cash flows from financing activities
Changes in short-term borrowings	(36)	(189)
Issuance of long-term debt	625	373
Retirement of long-term debt	(249)	(35)
Changes in Exelon/PHI intercompany money pool	(12)	10
Distributions to member	(414)	(268)
Contributions from member	560	359
Other financing activities	(8)	(8)
Net cash flows provided by (used in) financing activities	466	242
Increase (decrease) in cash, restricted cash, and cash equivalents	(48)	(95)
Cash, restricted cash, and cash equivalents at beginning of period	160	181
Cash, restricted cash, and cash equivalents at end of period	112	86
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(41)	(24)
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income (loss)	134	109
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	199	186
Deferred income taxes and amortization of investment tax credits	10	(22)
Other non-cash operating activities	(43)	11
Changes in assets and liabilities:
Accounts receivable	(23)	(45)
Receivables from and payables to affiliates, net	(11)	(22)
Inventories	1	3
Accounts payable and accrued expenses	(26)	11
Income taxes	(20)	(18)
Pension and non-pension postretirement benefit contributions	(7)	(6)
Other assets and liabilities	(79)	(52)
Net cash flows provided by operating activities	135	155
Cash flows from investing activities
Capital expenditures	(439)	(324)
Other investing activities	(2)	(3)
Net cash flows provided by (used in) investing activities	(441)	(327)
Cash flows from financing activities
Changes in short-term borrowings	119	(68)
Issuance of long-term debt	150	150
Retirement of long-term debt	0	(1)
Changes in Exelon/PHI intercompany money pool	9	50
Dividends paid on common stock	(123)	(101)
Contributions from parent	138	137
Other financing activities	(2)	(6)
Net cash flows provided by (used in) financing activities	291	161
Increase (decrease) in cash, restricted cash, and cash equivalents	(15)	(11)
Cash, restricted cash, and cash equivalents at beginning of period	65	63
Cash, restricted cash, and cash equivalents at end of period	50	52
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(15)	(28)
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income (loss)	86	64
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	104	94
Deferred income taxes and amortization of investment tax credits	4	(19)
Other non-cash operating activities	(12)	40
Changes in assets and liabilities:
Accounts receivable	24	6
Receivables from and payables to affiliates, net	(12)	(2)
Accounts payable and accrued expenses	7	3
Income taxes	14	(12)
Other assets and liabilities	(22)	(21)
Net cash flows provided by operating activities	193	153
Cash flows from investing activities
Capital expenditures	(211)	(184)
Changes in Exelon/PHI intercompany money pool	(9)	(55)
Other investing activities	1	(3)
Net cash flows provided by (used in) investing activities	(219)	(242)
Cash flows from financing activities
Changes in short-term borrowings	(146)	(56)
Issuance of long-term debt	125	100
Retirement of long-term debt	0	(1)
Dividends paid on common stock	(63)	(66)
Contributions from parent	120	106
Other financing activities	(3)	(1)
Net cash flows provided by (used in) financing activities	33	82
Increase (decrease) in cash, restricted cash, and cash equivalents	7	(7)
Cash, restricted cash, and cash equivalents at beginning of period	15	13
Cash, restricted cash, and cash equivalents at end of period	22	6
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	(14)	(4)
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income (loss)	51	31
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, and accretion, including nuclear fuel and energy contract amortization	87	86
Deferred income taxes and amortization of investment tax credits	(2)	(30)
Other non-cash operating activities	(14)	34
Changes in assets and liabilities:
Accounts receivable	(30)	(23)
Receivables from and payables to affiliates, net	4	9
Inventories	2	2
Accounts payable and accrued expenses	(2)	17
Income taxes	2	2
Pension and non-pension postretirement benefit contributions	(3)	(2)
Other assets and liabilities	(25)	(68)
Net cash flows provided by operating activities	70	58
Cash flows from investing activities
Capital expenditures	(239)	(178)
Other investing activities	0	5
Net cash flows provided by (used in) investing activities	(239)	(173)
Cash flows from financing activities
Changes in short-term borrowings	(9)	(65)
Issuance of long-term debt	350	123
Retirement of long-term debt	(249)	(34)
Changes in Exelon/PHI intercompany money pool	0	5
Dividends paid on common stock	(229)	(35)
Contributions from parent	303	116
Other financing activities	(4)	(1)
Net cash flows provided by (used in) financing activities	162	109
Increase (decrease) in cash, restricted cash, and cash equivalents	(7)	(6)
Cash, restricted cash, and cash equivalents at beginning of period	30	28
Cash, restricted cash, and cash equivalents at end of period	23	22
Supplemental Cash Flow Information
Increase (decrease) in capital expenditures not paid	$ (13)	$ 7