Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net Income (Loss)	$ 2,084	$ 3,876	$ 1,196
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	5,971	5,427	5,576
Impairment losses of long-lived assets, intangibles and regulatory assets	50	573	306
Gain on deconsolidation of business	0	(213)	0
(Gain) Loss on sales of assets and businesses	(56)	(3)	48
Bargain purchase gain	0	(233)	0
Deferred income taxes and amortization of investment tax credits	(106)	(362)	656
Net fair value changes related to derivatives	294	151	24
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	303	(616)	(229)
Other non-cash operating activities	1,124	721	1,333
Changes in assets and liabilities:
Accounts receivable	(565)	(470)	(432)
Inventories	(37)	(72)	7
Accounts payable and accrued expenses	551	(388)	771
Option premiums received (paid), net	(43)	28	(66)
Collateral (posted) received, net	82	(158)	931
Income taxes	340	299	576
Pension and non-pension postretirement benefit contributions	(383)	(405)	(397)
Deposit with IRS	0	0	(1,250)
Other assets and liabilities	(965)	(675)	(589)
Net cash flows provided by (used in) operating activities	8,644	7,480	8,461
Cash flows from investing activities
Capital expenditures	(7,594)	(7,584)	(8,553)
Proceeds from termination of direct financing lease investment	0	0	360
Proceeds from nuclear decommissioning trust fund sales	8,762	7,845	9,496
Investment in nuclear decommissioning trust funds	(8,997)	(8,113)	(9,738)
Reduction of restricted cash from deconsolidation of business	0	(87)	0
Acquisitions of businesses, net	(154)	(208)	(6,923)
Proceeds from sales of long-lived assets	91	219	61
Other investing activities	58	(43)	(153)
Net cash flows provided by (used in) investing activities	(7,834)	(7,971)	(15,450)
Cash flows from financing activities
Changes in short-term borrowings	(338)	(261)	(353)
Proceeds from short-term borrowings with maturities greater than 90 days	126	621	240
Repayments on short-term borrowings with maturities greater than 90 days	(1)	(700)	(462)
Issuance of long-term debt	3,115	3,470	4,716
Retirement of long-term debt	(1,786)	(2,490)	(1,936)
Retirement of long-term debt to financing trust	0	(250)	0
Common stock issued from treasury stock	0	1,150	0
Redemption of preference stock	0	0	(190)
Dividends paid on common stock	(1,332)	(1,236)	(1,166)
Proceeds from employee stock plans	105	150	55
Sale of noncontrolling interest	0	396	372
Other financing activities	(108)	(83)	(85)
Net cash flows provided by (used in) financing activities	(219)	767	1,191
Increase (Decrease) in cash, cash equivalents and restricted cash	591	276	(5,798)
Cash, cash equivalents, and restricted cash at beginning of period	1,190	914	6,712
Cash, cash equivalents, and restricted cash at end of period	1,781	1,190	914
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net Income (Loss)	443	2,798	550
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	3,415	3,056	3,519
Impairment losses of long-lived assets, intangibles and regulatory assets	50	510	243
Gain on deconsolidation of business	0	(213)	0
(Gain) Loss on sales of assets and businesses	(48)	(2)	59
Bargain purchase gain	0	(233)	0
Deferred income taxes and amortization of investment tax credits	(451)	(2,023)	(277)
Net fair value changes related to derivatives	307	167	40
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	303	(616)	(229)
Other non-cash operating activities	298	112	15
Changes in assets and liabilities:
Accounts receivable	(359)	(320)	(152)
Receivables from and payables to affiliates, net	8	(7)	(21)
Inventories	(12)	(29)	(4)
Accounts payable and accrued expenses	376	4	29
Option premiums received (paid), net	(43)	28	(66)
Collateral (posted) received, net	64	(129)	923
Income taxes	(193)	496	182
Pension and non-pension postretirement benefit contributions	(139)	(148)	(152)
Other assets and liabilities	(158)	(152)	(217)
Net cash flows provided by (used in) operating activities	3,861	3,299	4,442
Cash flows from investing activities
Capital expenditures	(2,242)	(2,259)	(3,078)
Proceeds from nuclear decommissioning trust fund sales	8,762	7,845	9,496
Investment in nuclear decommissioning trust funds	(8,997)	(8,113)	(9,738)
Reduction of restricted cash from deconsolidation of business	0	(87)	0
Acquisitions of businesses, net	(154)	(208)	(293)
Proceeds from sales of long-lived assets	90	218	37
Other investing activities	10	(58)	(240)
Net cash flows provided by (used in) investing activities	(2,531)	(2,662)	(3,816)
Cash flows from financing activities
Changes in short-term borrowings	0	(620)	620
Proceeds from short-term borrowings with maturities greater than 90 days	1	121	240
Repayments on short-term borrowings with maturities greater than 90 days	(1)	(200)	(162)
Issuance of long-term debt	15	1,645	388
Retirement of long-term debt	(141)	(1,261)	(202)
Changes in Exelon intercompany money pool	46	(1)	(1,191)
Distributions to member	(1,001)	(659)	(922)
Contributions from member	155	102	142
Sale of noncontrolling interest	0	396	372
Other financing activities	(55)	(54)	(19)
Net cash flows provided by (used in) financing activities	(981)	(531)	(734)
Increase (Decrease) in cash, cash equivalents and restricted cash	349	106	(108)
Cash, cash equivalents, and restricted cash at beginning of period	554	448	556
Cash, cash equivalents, and restricted cash at end of period	903	554	448
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net Income (Loss)	664	567	378
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	940	850	775
Deferred income taxes and amortization of investment tax credits	259	659	439
Other non-cash operating activities	242	164	215
Changes in assets and liabilities:
Accounts receivable	(136)	(59)	(25)
Receivables from and payables to affiliates, net	26	8	3
Inventories	1	4	1
Accounts payable and accrued expenses	70	(297)	339
Collateral (posted) received, net	11	(26)	7
Income taxes	62	(308)	306
Pension and non-pension postretirement benefit contributions	(42)	(41)	(38)
Other assets and liabilities	(348)	6	105
Net cash flows provided by (used in) operating activities	1,749	1,527	2,505
Cash flows from investing activities
Capital expenditures	(2,126)	(2,250)	(2,734)
Other investing activities	29	20	49
Net cash flows provided by (used in) investing activities	(2,097)	(2,230)	(2,685)
Cash flows from financing activities
Changes in short-term borrowings	0	0	(294)
Issuance of long-term debt	1,350	1,000	1,200
Retirement of long-term debt	(840)	(425)	(665)
Dividends paid on common stock	(459)	(422)	(369)
Contributions from parent	500	651	315
Other financing activities	(17)	(15)	(18)
Net cash flows provided by (used in) financing activities	534	789	169
Increase (Decrease) in cash, cash equivalents and restricted cash	186	86	(11)
Cash, cash equivalents, and restricted cash at beginning of period	144	58	69
Cash, cash equivalents, and restricted cash at end of period	330	144	58
PECO Energy Co [Member]
Cash flows from operating activities
Net Income (Loss)	460	434	438
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	301	286	270
Deferred income taxes and amortization of investment tax credits	(5)	19	78
Other non-cash operating activities	51	54	65
Changes in assets and liabilities:
Accounts receivable	(74)	(44)	(71)
Receivables from and payables to affiliates, net	7	(6)	6
Inventories	(14)	1	6
Accounts payable and accrued expenses	(3)	6	67
Income taxes	15	34	8
Pension and non-pension postretirement benefit contributions	(28)	(24)	(30)
Other assets and liabilities	29	(5)	(8)
Net cash flows provided by (used in) operating activities	739	755	829
Cash flows from investing activities
Capital expenditures	(849)	(732)	(686)
Changes in Exelon intercompany money pool	0	131	(131)
Other investing activities	9	4	20
Net cash flows provided by (used in) investing activities	(840)	(597)	(797)
Cash flows from financing activities
Issuance of long-term debt	700	325	300
Retirement of long-term debt	(500)	0	(300)
Dividends paid on common stock	(306)	(288)	(277)
Contributions from parent	89	16	18
Other financing activities	(22)	(3)	(4)
Net cash flows provided by (used in) financing activities	(39)	50	(263)
Increase (Decrease) in cash, cash equivalents and restricted cash	(140)	208	(231)
Cash, cash equivalents, and restricted cash at beginning of period	275	67	298
Cash, cash equivalents, and restricted cash at end of period	135	275	67
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net Income (Loss)	313	307	294
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	483	473	423
Impairment losses of long-lived assets, intangibles and regulatory assets	0	7	52
Deferred income taxes and amortization of investment tax credits	76	145	118
Other non-cash operating activities	58	65	88
Changes in assets and liabilities:
Accounts receivable	8	(5)	(98)
Receivables from and payables to affiliates, net	12	(4)	3
Inventories	2	(9)	1
Accounts payable and accrued expenses	(1)	(15)	138
Collateral (posted) received, net	4	0	0
Income taxes	(20)	60	18
Pension and non-pension postretirement benefit contributions	(54)	(53)	(49)
Other assets and liabilities	(92)	(150)	(43)
Net cash flows provided by (used in) operating activities	789	821	945
Cash flows from investing activities
Capital expenditures	(959)	(882)	(934)
Other investing activities	9	7	24
Net cash flows provided by (used in) investing activities	(950)	(875)	(910)
Cash flows from financing activities
Changes in short-term borrowings	(42)	32	(165)
Issuance of long-term debt	300	300	850
Retirement of long-term debt	0	(41)	(379)
Retirement of long-term debt to financing trust	0	(250)	0
Redemption of preference stock	0	0	(190)
Dividends paid on preferred securities	0	0	(8)
Dividends paid on common stock	(209)	(198)	(179)
Contributions from parent	109	184	61
Other financing activities	(2)	(5)	(11)
Net cash flows provided by (used in) financing activities	156	22	(21)
Increase (Decrease) in cash, cash equivalents and restricted cash	(5)	(32)	14
Cash, cash equivalents, and restricted cash at beginning of period	18	50	36
Cash, cash equivalents, and restricted cash at end of period	13	18	50
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net Income (Loss)	398	362
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	740	675
Impairment losses of long-lived assets, intangibles and regulatory assets	0	52
Deferred income taxes and amortization of investment tax credits	32	252
Net fair value changes related to derivatives	0	0
Other non-cash operating activities	(143)	(58)
Changes in assets and liabilities:
Accounts receivable	2	26
Receivables from and payables to affiliates, net	8	(2)
Inventories	14	37
Accounts payable and accrued expenses	45	(106)
Income taxes	34	79
Pension and non-pension postretirement benefit contributions	74	99
Other assets and liabilities	178	258
Net cash flows provided by (used in) operating activities	1,132	950
Cash flows from investing activities
Capital expenditures	(1,375)	(1,396)
Purchases of investments	0	0
Other investing activities	4	(1)
Net cash flows provided by (used in) investing activities	(1,371)	(1,397)
Cash flows from financing activities
Changes in short-term borrowings	(296)	328
Proceeds from short-term borrowings with maturities greater than 90 days	125	0
Repayments on short-term borrowings with maturities greater than 90 days	0	(500)
Issuance of long-term debt	750	202
Retirement of long-term debt	(299)	(169)
Changes in Exelon intercompany money pool	0	0
Distributions to member	(326)	(311)
Proceeds from employee stock plans	0	0
Contributions from parent	385	758
Other financing activities	(9)	(2)
Net cash flows provided by (used in) financing activities	330	306
Increase (Decrease) in cash, cash equivalents and restricted cash	91	(141)
Cash, cash equivalents, and restricted cash at beginning of period	95	236
Cash, cash equivalents, and restricted cash at end of period	186	95	236
Pepco Holdings LLC [Member] | Predecessor [Member]
Cash flows from financing activities
Cash, cash equivalents, and restricted cash at beginning of period			58
Pepco Holdings LLC [Member] | Successor [Member]
Cash flows from financing activities
Cash, cash equivalents, and restricted cash at beginning of period		236
Cash, cash equivalents, and restricted cash at end of period			236
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net Income (Loss)	210	205	42
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	385	321	295
Impairment losses of long-lived assets, intangibles and regulatory assets	0	14	0
Deferred income taxes and amortization of investment tax credits	(18)	113	153
Other non-cash operating activities	60	(6)	175
Changes in assets and liabilities:
Accounts receivable	(5)	(20)	(41)
Receivables from and payables to affiliates, net	(17)	0	44
Inventories	(6)	(24)	1
Accounts payable and accrued expenses	59	(63)	32
Income taxes	(13)	81	110
Pension and non-pension postretirement benefit contributions	(17)	(72)	(32)
Other assets and liabilities	(164)	(142)	(128)
Net cash flows provided by (used in) operating activities	474	407	651
Cash flows from investing activities
Capital expenditures	(656)	(628)	(586)
Purchases of investments	0	0	(30)
Other investing activities	2	0	0
Net cash flows provided by (used in) investing activities	(654)	(628)	(616)
Cash flows from financing activities
Changes in short-term borrowings	14	3	(41)
Issuance of long-term debt	200	202	4
Retirement of long-term debt	(14)	(13)	(11)
Dividends paid on common stock	(169)	(133)	(136)
Contributions from parent	166	161	187
Other financing activities	(4)	(1)	(3)
Net cash flows provided by (used in) financing activities	193	219	0
Increase (Decrease) in cash, cash equivalents and restricted cash	13	(2)	35
Cash, cash equivalents, and restricted cash at beginning of period	40	42	7
Cash, cash equivalents, and restricted cash at end of period	53	40	42
Delmarva Power & Light Company [Member]
Cash flows from operating activities
Net Income (Loss)	120	121	(9)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	182	167	157
Impairment losses of long-lived assets, intangibles and regulatory assets	0	6	0
Deferred income taxes and amortization of investment tax credits	24	89	109
Other non-cash operating activities	24	9	114
Changes in assets and liabilities:
Accounts receivable	8	(22)	(5)
Receivables from and payables to affiliates, net	(9)	11	13
Inventories	(3)	(5)	0
Accounts payable and accrued expenses	11	(8)	(4)
Collateral (posted) received, net	0	0	1
Income taxes	2	26	28
Pension and non-pension postretirement benefit contributions	0	(2)	(22)
Other assets and liabilities	(7)	(71)	(72)
Net cash flows provided by (used in) operating activities	352	321	310
Cash flows from investing activities
Capital expenditures	(364)	(428)	(349)
Other investing activities	2	(1)	13
Net cash flows provided by (used in) investing activities	(362)	(429)	(336)
Cash flows from financing activities
Changes in short-term borrowings	(216)	216	(105)
Issuance of long-term debt	200	0	175
Retirement of long-term debt	(4)	(40)	(100)
Dividends paid on common stock	(96)	(112)	(54)
Contributions from parent	150	0	152
Other financing activities	(2)	0	(1)
Net cash flows provided by (used in) financing activities	32	64	67
Increase (Decrease) in cash, cash equivalents and restricted cash	22	(44)	41
Cash, cash equivalents, and restricted cash at beginning of period	2	46	5
Cash, cash equivalents, and restricted cash at end of period	24	2	46
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net Income (Loss)	75	77	(42)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	136	146	165
Impairment losses of long-lived assets, intangibles and regulatory assets	0	7	0
Deferred income taxes and amortization of investment tax credits	25	32	22
Other non-cash operating activities	24	17	155
Changes in assets and liabilities:
Accounts receivable	(8)	14	(8)
Receivables from and payables to affiliates, net	1	0	13
Inventories	(4)	(7)	(1)
Accounts payable and accrued expenses	(7)	(2)	9
Income taxes	(2)	(11)	174
Pension and non-pension postretirement benefit contributions	(6)	(20)	(17)
Other assets and liabilities	(6)	(47)	(85)
Net cash flows provided by (used in) operating activities	228	206	385
Cash flows from investing activities
Capital expenditures	(335)	(312)	(311)
Other investing activities	1	(1)	4
Net cash flows provided by (used in) investing activities	(334)	(313)	(307)
Cash flows from financing activities
Changes in short-term borrowings	(94)	108	(5)
Proceeds from short-term borrowings with maturities greater than 90 days	125	0	0
Issuance of long-term debt	350	0	0
Retirement of long-term debt	(281)	(35)	(48)
Dividends paid on common stock	(59)	(68)	(63)
Contributions from parent	67	0	139
Other financing activities	(3)	0	(1)
Net cash flows provided by (used in) financing activities	105	5	22
Increase (Decrease) in cash, cash equivalents and restricted cash	(1)	(102)	100
Cash, cash equivalents, and restricted cash at beginning of period	31	133	33
Cash, cash equivalents, and restricted cash at end of period	$ 30	$ 31	$ 133