Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities
Net income	$ 966	$ 636
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	1,460	1,501
Impairment of long-lived assets	7	0
Gain on sales of assets and businesses	0	(56)
Deferred income taxes and amortization of investment tax credits	187	(14)
Net fair value changes related to derivatives	31	259
Net realized and unrealized (gains) losses on NDT funds	(308)	68
Other non-cash operating activities	127	240
Changes in assets and liabilities:
Accounts receivable	79	133
Inventories	128	167
Accounts payable and accrued expenses	(764)	(451)
Option premiums received (paid), net	6	(27)
Collateral posted, net	(101)	(214)
Income taxes	141	86
Pension and non-pension postretirement benefit contributions	(328)	(331)
Other assets and liabilities	(587)	(495)
Net cash flows provided by operating activities	1,044	1,502
Cash flows from investing activities
Capital expenditures	(1,873)	(1,880)
Proceeds from NDT fund sales	3,713	1,189
Investment in NDT funds	(3,666)	(1,248)
Proceeds from sales of assets and businesses	8	79
Other investing activities	32	3
Net cash flows used in investing activities	(1,786)	(1,857)
Cash flows from financing activities
Changes in short-term borrowings	540	726
Proceeds from short-term borrowings with maturities greater than 90 days	0	1
Repayments on short-term borrowings with maturities greater than 90 days	0	(1)
Issuance of long-term debt	402	1,130
Retirement of long-term debt	(352)	(1,241)
Dividends paid on common stock	(352)	(333)
Proceeds from employee stock plans	51	12
Other financing activities	(14)	(30)
Net cash flows provided by (used in) financing activities	275	264
Increase (Decrease) in cash, cash equivalents and restricted cash	(467)	(91)
Cash, cash equivalents and restricted cash at beginning of period	1,781	1,190
Cash, cash equivalents and restricted cash at end of period	1,314	1,099
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	422	186
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	789	858
Impairment of long-lived assets	7	0
Gain on sales of assets and businesses	0	(53)
Deferred income taxes and amortization of investment tax credits	108	(68)
Net fair value changes related to derivatives	33	264
Net realized and unrealized (gains) losses on NDT funds	(308)	68
Other non-cash operating activities	(90)	45
Changes in assets and liabilities:
Accounts receivable	197	194
Receivables from and payables to affiliates, net	(5)	(15)
Inventories	103	122
Accounts payable and accrued expenses	(411)	(317)
Option premiums received (paid), net	6	(27)
Collateral posted, net	(87)	(214)
Income taxes	146	79
Pension and non-pension postretirement benefit contributions	(141)	(125)
Other assets and liabilities	(187)	(142)
Net cash flows provided by operating activities	582	855
Cash flows from investing activities
Capital expenditures	(511)	(628)
Proceeds from NDT fund sales	3,713	1,189
Investment in NDT funds	(3,666)	(1,248)
Proceeds from sales of assets and businesses	8	79
Other investing activities	23	(7)
Net cash flows used in investing activities	(433)	(615)
Cash flows from financing activities
Changes in short-term borrowings	0	165
Proceeds from short-term borrowings with maturities greater than 90 days	0	1
Repayments on short-term borrowings with maturities greater than 90 days	0	(1)
Issuance of long-term debt	2	4
Retirement of long-term debt	(47)	(29)
Changes in Exelon intercompany money pool	(100)	0
Distributions to member	(225)	(188)
Other financing activities	(6)	(9)
Net cash flows provided by (used in) financing activities	(376)	(57)
Increase (Decrease) in cash, cash equivalents and restricted cash	(227)	183
Cash, cash equivalents and restricted cash at beginning of period	903	554
Cash, cash equivalents and restricted cash at end of period	676	737
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	157	165
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	251	228
Deferred income taxes and amortization of investment tax credits	34	50
Other non-cash operating activities	56	46
Changes in assets and liabilities:
Accounts receivable	14	39
Receivables from and payables to affiliates, net	(34)	(19)
Inventories	(3)	5
Accounts payable and accrued expenses	(188)	(158)
Collateral posted, net	(13)	(3)
Income taxes	5	(5)
Pension and non-pension postretirement benefit contributions	(67)	(38)
Other assets and liabilities	(121)	(176)
Net cash flows provided by operating activities	91	134
Cash flows from investing activities
Capital expenditures	(503)	(531)
Other investing activities	11	8
Net cash flows used in investing activities	(492)	(523)
Cash flows from financing activities
Changes in short-term borrowings	322	317
Issuance of long-term debt	400	800
Retirement of long-term debt	(300)	(700)
Dividends paid on common stock	(127)	(114)
Contributions from parent	63	113
Other financing activities	(9)	(9)
Net cash flows provided by (used in) financing activities	349	407
Increase (Decrease) in cash, cash equivalents and restricted cash	(52)	18
Cash, cash equivalents and restricted cash at beginning of period	330	144
Cash, cash equivalents and restricted cash at end of period	278	162
PECO Energy Co [Member]
Cash flows from operating activities
Net income	168	113
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	81	75
Deferred income taxes and amortization of investment tax credits	5	(4)
Other non-cash operating activities	16	21
Changes in assets and liabilities:
Accounts receivable	(86)	(51)
Receivables from and payables to affiliates, net	7	7
Inventories	23	12
Accounts payable and accrued expenses	(13)	6
Income taxes	20	5
Pension and non-pension postretirement benefit contributions	(25)	(24)
Other assets and liabilities	(119)	(141)
Net cash flows provided by operating activities	77	19
Cash flows from investing activities
Capital expenditures	(222)	(217)
Other investing activities	2	2
Net cash flows used in investing activities	(220)	(215)
Cash flows from financing activities
Changes in short-term borrowings	0	220
Issuance of long-term debt	0	325
Retirement of long-term debt	0	(500)
Dividends paid on common stock	(90)	(287)
Changes in Exelon intercompany money pool	0	194
Contributions from parent	145	0
Other financing activities	0	(5)
Net cash flows provided by (used in) financing activities	55	(53)
Increase (Decrease) in cash, cash equivalents and restricted cash	(88)	(249)
Cash, cash equivalents and restricted cash at beginning of period	135	275
Cash, cash equivalents and restricted cash at end of period	47	26
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	160	128
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	134
Deferred income taxes and amortization of investment tax credits	28	22
Other non-cash operating activities	27	20
Changes in assets and liabilities:
Accounts receivable	(39)	(32)
Receivables from and payables to affiliates, net	(10)	0
Inventories	17	20
Accounts payable and accrued expenses	(27)	(9)
Collateral posted, net	(1)	0
Income taxes	8	14
Pension and non-pension postretirement benefit contributions	(40)	(45)
Other assets and liabilities	(14)	61
Net cash flows provided by operating activities	245	313
Cash flows from investing activities
Capital expenditures	(258)	(224)
Other investing activities	1	1
Net cash flows used in investing activities	(257)	(223)
Cash flows from financing activities
Changes in short-term borrowings	71	(32)
Dividends paid on common stock	(56)	(52)
Net cash flows provided by (used in) financing activities	15	(84)
Increase (Decrease) in cash, cash equivalents and restricted cash	3	6
Cash, cash equivalents and restricted cash at beginning of period	13	18
Cash, cash equivalents and restricted cash at end of period	16	24
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income	117	65
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	180	183
Deferred income taxes and amortization of investment tax credits	0	17
Other non-cash operating activities	35	53
Changes in assets and liabilities:
Accounts receivable	(11)	(9)
Receivables from and payables to affiliates, net	(8)	10
Inventories	(12)	4
Accounts payable and accrued expenses	(9)	44
Income taxes	4	(9)
Pension and non-pension postretirement benefit contributions	(6)	(55)
Other assets and liabilities	(61)	(24)
Net cash flows provided by operating activities	229	279
Cash flows from investing activities
Capital expenditures	(358)	(258)
Other investing activities	1	0
Net cash flows used in investing activities	(357)	(258)
Cash flows from financing activities
Changes in short-term borrowings	147	57
Retirement of long-term debt	(5)	(12)
Changes in Exelon intercompany money pool	0	13
Distributions to member	(128)	(71)
Contributions from member	19	0
Net cash flows provided by (used in) financing activities	33	(13)
Increase (Decrease) in cash, cash equivalents and restricted cash	(95)	8
Cash, cash equivalents and restricted cash at beginning of period	186	95
Cash, cash equivalents and restricted cash at end of period	91	103
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income	55	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	94	96
Deferred income taxes and amortization of investment tax credits	(2)	4
Other non-cash operating activities	3	10
Changes in assets and liabilities:
Accounts receivable	(19)	0
Receivables from and payables to affiliates, net	3	(18)
Inventories	(14)	(2)
Accounts payable and accrued expenses	(2)	36
Income taxes	4	(3)
Pension and non-pension postretirement benefit contributions	(4)	(7)
Other assets and liabilities	(37)	(21)
Net cash flows provided by operating activities	81	126
Cash flows from investing activities
Capital expenditures	(144)	(127)
Other investing activities	1	0
Net cash flows used in investing activities	(143)	(127)
Cash flows from financing activities
Changes in short-term borrowings	65	34
Dividends paid on common stock	(24)	(25)
Contributions from parent	14	0
Net cash flows provided by (used in) financing activities	55	9
Increase (Decrease) in cash, cash equivalents and restricted cash	(7)	8
Cash, cash equivalents and restricted cash at beginning of period	53	40
Cash, cash equivalents and restricted cash at end of period	46	48
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income	53	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	46	45
Deferred income taxes and amortization of investment tax credits	1	10
Other non-cash operating activities	11	19
Changes in assets and liabilities:
Accounts receivable	(5)	(1)
Receivables from and payables to affiliates, net	(15)	(16)
Inventories	1	7
Accounts payable and accrued expenses	11	18
Income taxes	5	(5)
Other assets and liabilities	(10)	7
Net cash flows provided by operating activities	98	115
Cash flows from investing activities
Capital expenditures	(78)	(65)
Net cash flows used in investing activities	(78)	(65)
Cash flows from financing activities
Changes in short-term borrowings	5	(5)
Retirement of long-term debt	0	(4)
Dividends paid on common stock	(41)	(36)
Net cash flows provided by (used in) financing activities	(36)	(45)
Increase (Decrease) in cash, cash equivalents and restricted cash	(16)	5
Cash, cash equivalents and restricted cash at beginning of period	24	2
Cash, cash equivalents and restricted cash at end of period	8	7
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income	10	7
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	31	33
Deferred income taxes and amortization of investment tax credits	0	2
Other non-cash operating activities	5	9
Changes in assets and liabilities:
Accounts receivable	13	(5)
Receivables from and payables to affiliates, net	(4)	(4)
Inventories	1	0
Accounts payable and accrued expenses	12	30
Income taxes	(1)	0
Pension and non-pension postretirement benefit contributions	0	(6)
Other assets and liabilities	(7)	(7)
Net cash flows provided by operating activities	60	59
Cash flows from investing activities
Capital expenditures	(128)	(63)
Other investing activities	0	(1)
Net cash flows used in investing activities	(128)	(64)
Cash flows from financing activities
Changes in short-term borrowings	77	28
Retirement of long-term debt	(4)	(8)
Dividends paid on common stock	(12)	(9)
Contributions from parent	5	0
Net cash flows provided by (used in) financing activities	66	11
Increase (Decrease) in cash, cash equivalents and restricted cash	(2)	6
Cash, cash equivalents and restricted cash at beginning of period	30	31
Cash, cash equivalents and restricted cash at end of period	$ 28	$ 37