Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net income	$ 1,460	$ 1,179
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	2,922	3,000
Impairment of long-lived assets	9	41
Gain on sales of assets and businesses	(33)	(60)
Deferred income taxes and amortization of investment tax credits	284	(2)
Net fair value changes related to derivatives	107	151
Net realized and unrealized (gains) losses on NDT funds	(404)	80
Other non-cash operating activities	277	479
Changes in assets and liabilities:
Accounts receivable	618	(105)
Inventories	19	60
Accounts payable and accrued expenses	(924)	(342)
Option premiums received (paid), net	48	(36)
Collateral (posted) received, net	(311)	81
Income taxes	151	129
Pension and non-pension postretirement benefit contributions	(355)	(345)
Other assets and liabilities	(970)	(441)
Net cash flows provided by operating activities	2,898	3,869
Cash flows from investing activities
Capital expenditures	(3,572)	(3,807)
Proceeds from NDT fund sales	6,920	3,822
Investment in NDT funds	(6,847)	(3,924)
Acquisition of assets and businesses, net	0	(57)
Proceeds from sales of assets and businesses	14	89
Other investing activities	26	31
Net cash flows used in investing activities	(3,459)	(3,846)
Cash flows from financing activities
Changes in short-term borrowings	470	200
Proceeds from short-term borrowings with maturities greater than 90 days	0	126
Repayments on short-term borrowings with maturities greater than 90 days	(125)	(1)
Issuance of long-term debt	850	1,488
Retirement of long-term debt	(574)	(1,309)
Dividends paid on common stock	(704)	(666)
Proceeds from employee stock plans	75	27
Other financing activities	(34)	(50)
Net cash flows provided by (used in) financing activities	(42)	(185)
Increase (Decrease) in cash, cash equivalents and restricted cash	(603)	(162)
Cash, cash equivalents and restricted cash at beginning of period	1,781	1,190
Cash, cash equivalents and restricted cash at end of period	1,178	1,028
Supplemental Cash Flow Information
Increase (Decrease) in capital expenditures not paid	(133)	(283)
Change in PPE related to ARO update	301	47
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	540	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	1,580	1,735
Impairment of long-lived assets	9	41
Gain on sales of assets and businesses	(33)	(54)
Deferred income taxes and amortization of investment tax credits	151	(149)
Net fair value changes related to derivatives	114	158
Net realized and unrealized (gains) losses on NDT funds	(404)	80
Other non-cash operating activities	(50)	85
Changes in assets and liabilities:
Accounts receivable	472	258
Receivables from and payables to affiliates, net	(18)	7
Inventories	32	34
Accounts payable and accrued expenses	(507)	(272)
Option premiums received (paid), net	48	(36)
Collateral (posted) received, net	(318)	91
Income taxes	321	58
Pension and non-pension postretirement benefit contributions	(158)	(129)
Other assets and liabilities	(351)	(212)
Net cash flows provided by operating activities	1,428	2,063
Cash flows from investing activities
Capital expenditures	(890)	(1,298)
Proceeds from NDT fund sales	6,920	3,822
Investment in NDT funds	(6,847)	(3,924)
Acquisition of assets and businesses, net	0	(57)
Proceeds from sales of assets and businesses	14	89
Changes in Exelon/PHI intercompany money pool	(179)	(185)
Other investing activities	8	4
Net cash flows used in investing activities	(974)	(1,549)
Cash flows from financing activities
Issuance of long-term debt	40	13
Retirement of long-term debt	(130)	(76)
Changes in Exelon/PHI intercompany money pool	(100)	(54)
Distributions to member	(449)	(377)
Other financing activities	(21)	(24)
Net cash flows provided by (used in) financing activities	(660)	(518)
Increase (Decrease) in cash, cash equivalents and restricted cash	(206)	(4)
Cash, cash equivalents and restricted cash at beginning of period	903	554
Cash, cash equivalents and restricted cash at end of period	697	550
Supplemental Cash Flow Information
Increase (Decrease) in capital expenditures not paid	(30)	(310)
Change in PPE related to ARO update	301	47
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	344	329
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	508	459
Deferred income taxes and amortization of investment tax credits	64	84
Other non-cash operating activities	87	117
Changes in assets and liabilities:
Accounts receivable	56	(133)
Receivables from and payables to affiliates, net	(16)	15
Inventories	(5)	5
Accounts payable and accrued expenses	(121)	(41)
Collateral (posted) received, net	11	(13)
Income taxes	43	(15)
Pension and non-pension postretirement benefit contributions	(68)	(39)
Other assets and liabilities	(236)	(166)
Net cash flows provided by operating activities	667	602
Cash flows from investing activities
Capital expenditures	(961)	(1,026)
Other investing activities	17	17
Net cash flows used in investing activities	(944)	(1,009)
Cash flows from financing activities
Changes in short-term borrowings	303	320
Issuance of long-term debt	400	800
Retirement of long-term debt	(300)	(700)
Contributions from parent	124	225
Dividends paid on common stock	(254)	(229)
Other financing activities	(10)	(10)
Net cash flows provided by (used in) financing activities	263	406
Increase (Decrease) in cash, cash equivalents and restricted cash	(14)	(1)
Cash, cash equivalents and restricted cash at beginning of period	330	144
Cash, cash equivalents and restricted cash at end of period	316	143
Supplemental Cash Flow Information
Increase (Decrease) in capital expenditures not paid	(77)	(22)
PECO Energy Co [Member]
Cash flows from operating activities
Net income	270	210
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	164	149
Deferred income taxes and amortization of investment tax credits	8	(10)
Other non-cash operating activities	15	22
Changes in assets and liabilities:
Accounts receivable	39	(43)
Receivables from and payables to affiliates, net	(4)	(4)
Inventories	12	4
Accounts payable and accrued expenses	(31)	(18)
Income taxes	(11)	19
Pension and non-pension postretirement benefit contributions	(27)	(25)
Other assets and liabilities	(117)	(50)
Net cash flows provided by operating activities	318	254
Cash flows from investing activities
Capital expenditures	(447)	(411)
Other investing activities	4	5
Net cash flows used in investing activities	(443)	(406)
Cash flows from financing activities
Changes in short-term borrowings	0	50
Issuance of long-term debt	0	375
Retirement of long-term debt	0	(500)
Changes in Exelon/PHI intercompany money pool	52	233
Contributions from parent	145	41
Dividends paid on common stock	(180)	(293)
Other financing activities	(1)	(6)
Net cash flows provided by (used in) financing activities	16	(100)
Increase (Decrease) in cash, cash equivalents and restricted cash	(109)	(252)
Cash, cash equivalents and restricted cash at beginning of period	135	275
Cash, cash equivalents and restricted cash at end of period	26	23
Supplemental Cash Flow Information
Increase (Decrease) in capital expenditures not paid	33	(17)
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	206	179
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	252	248
Deferred income taxes and amortization of investment tax credits	47	39
Other non-cash operating activities	41	27
Changes in assets and liabilities:
Accounts receivable	85	73
Receivables from and payables to affiliates, net	(14)	(4)
Inventories	5	5
Accounts payable and accrued expenses	(73)	(48)
Collateral (posted) received, net	(5)	0
Income taxes	(29)	(45)
Pension and non-pension postretirement benefit contributions	(42)	(49)
Other assets and liabilities	(21)	39
Net cash flows provided by operating activities	452	464
Cash flows from investing activities
Capital expenditures	(542)	(434)
Other investing activities	4	6
Net cash flows used in investing activities	(538)	(428)
Cash flows from financing activities
Changes in short-term borrowings	194	59
Dividends paid on common stock	(112)	(105)
Net cash flows provided by (used in) financing activities	82	(46)
Increase (Decrease) in cash, cash equivalents and restricted cash	(4)	(10)
Cash, cash equivalents and restricted cash at beginning of period	13	18
Cash, cash equivalents and restricted cash at end of period	9	8
Supplemental Cash Flow Information
Increase (Decrease) in capital expenditures not paid	24	10
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income	223	149
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	369	363
Deferred income taxes and amortization of investment tax credits	2	14
Other non-cash operating activities	54	71
Changes in assets and liabilities:
Accounts receivable	(34)	(28)
Receivables from and payables to affiliates, net	(8)	4
Inventories	(25)	8
Accounts payable and accrued expenses	(25)	66
Income taxes	(12)	13
Pension and non-pension postretirement benefit contributions	(11)	(62)
Other assets and liabilities	(114)	(111)
Net cash flows provided by operating activities	419	487
Cash flows from investing activities
Capital expenditures	(698)	(629)
Other investing activities	2	2
Net cash flows used in investing activities	(696)	(627)
Cash flows from financing activities
Changes in short-term borrowings	(27)	(228)
Proceeds from short-term borrowings with maturities greater than 90 days	0	125
Repayments on short-term borrowings with maturities greater than 90 days	(125)	0
Issuance of long-term debt	410	300
Retirement of long-term debt	(125)	(25)
Changes in Exelon/PHI intercompany money pool	3	7
Distributions to member	(216)	(109)
Contributions from member	283	235
Other financing activities	(4)	(7)
Net cash flows provided by (used in) financing activities	199	298
Increase (Decrease) in cash, cash equivalents and restricted cash	(78)	158
Cash, cash equivalents and restricted cash at beginning of period	186	95
Cash, cash equivalents and restricted cash at end of period	108	253
Supplemental Cash Flow Information
Increase (Decrease) in capital expenditures not paid	(74)	61
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income	119	85
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	186	188
Deferred income taxes and amortization of investment tax credits	10	(8)
Other non-cash operating activities	8	24
Changes in assets and liabilities:
Accounts receivable	(36)	(31)
Receivables from and payables to affiliates, net	4	(11)
Inventories	(20)	2
Accounts payable and accrued expenses	(25)	77
Income taxes	(23)	3
Pension and non-pension postretirement benefit contributions	(6)	(11)
Other assets and liabilities	(40)	(91)
Net cash flows provided by operating activities	177	227
Cash flows from investing activities
Capital expenditures	(298)	(287)
Changes in Exelon/PHI intercompany money pool	(38)	0
Other investing activities	1	2
Net cash flows used in investing activities	(335)	(285)
Cash flows from financing activities
Changes in short-term borrowings	(40)	(26)
Issuance of long-term debt	260	100
Retirement of long-term debt	(117)	(7)
Contributions from parent	129	85
Dividends paid on common stock	(72)	(50)
Other financing activities	(3)	(4)
Net cash flows provided by (used in) financing activities	157	98
Increase (Decrease) in cash, cash equivalents and restricted cash	(1)	40
Cash, cash equivalents and restricted cash at beginning of period	53	40
Cash, cash equivalents and restricted cash at end of period	52	80
Supplemental Cash Flow Information
Increase (Decrease) in capital expenditures not paid	(18)	28
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income	83	57
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	91	88
Deferred income taxes and amortization of investment tax credits	(5)	9
Other non-cash operating activities	11	14
Changes in assets and liabilities:
Accounts receivable	15	18
Receivables from and payables to affiliates, net	(11)	(22)
Inventories	(3)	4
Accounts payable and accrued expenses	6	10
Income taxes	11	16
Pension and non-pension postretirement benefit contributions	(1)	0
Other assets and liabilities	(26)	22
Net cash flows provided by operating activities	171	216
Cash flows from investing activities
Capital expenditures	(160)	(166)
Other investing activities	1	1
Net cash flows used in investing activities	(159)	(165)
Cash flows from financing activities
Changes in short-term borrowings	0	(216)
Issuance of long-term debt	0	200
Retirement of long-term debt	0	(4)
Changes in Exelon/PHI intercompany money pool	38	0
Contributions from parent	0	150
Dividends paid on common stock	(70)	(40)
Other financing activities	0	(2)
Net cash flows provided by (used in) financing activities	(32)	88
Increase (Decrease) in cash, cash equivalents and restricted cash	(20)	139
Cash, cash equivalents and restricted cash at beginning of period	24	2
Cash, cash equivalents and restricted cash at end of period	4	141
Supplemental Cash Flow Information
Increase (Decrease) in capital expenditures not paid	(17)	17
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income	24	15
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	71	69
Deferred income taxes and amortization of investment tax credits	2	6
Other non-cash operating activities	7	12
Changes in assets and liabilities:
Accounts receivable	(11)	(13)
Receivables from and payables to affiliates, net	(9)	(4)
Inventories	(1)	4
Accounts payable and accrued expenses	16	14
Income taxes	6	3
Pension and non-pension postretirement benefit contributions	0	(6)
Other assets and liabilities	(44)	(33)
Net cash flows provided by operating activities	61	67
Cash flows from investing activities
Capital expenditures	(227)	(170)
Other investing activities	0	(2)
Net cash flows used in investing activities	(227)	(172)
Cash flows from financing activities
Changes in short-term borrowings	13	14
Proceeds from short-term borrowings with maturities greater than 90 days	0	125
Repayments on short-term borrowings with maturities greater than 90 days	(125)	0
Issuance of long-term debt	150	0
Retirement of long-term debt	(9)	(15)
Contributions from parent	155	0
Dividends paid on common stock	(24)	(19)
Other financing activities	(1)	0
Net cash flows provided by (used in) financing activities	159	105
Increase (Decrease) in cash, cash equivalents and restricted cash	(7)	0
Cash, cash equivalents and restricted cash at beginning of period	30	31
Cash, cash equivalents and restricted cash at end of period	23	31
Supplemental Cash Flow Information
Increase (Decrease) in capital expenditures not paid	$ (35)	$ 14