Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities
Net income	$ 1,979	$ 1,928
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	4,511	3,999
Impairment of long-lived assets and losses on regulatory assets	49	488
Gain on sales of assets and businesses	(55)	(5)
Bargain purchase gain	0	(233)
Deferred income taxes and amortization of investment tax credits	97	444
Net fair value changes related to derivatives	67	149
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(21)	(429)
Other non-cash operating activities	804	603
Changes in assets and liabilities:
Accounts receivable	(167)	184
Inventories	(24)	(87)
Accounts payable and accrued expenses	84	(591)
Option premiums (paid) received, net	(36)	35
Collateral received (posted), net	222	(100)
Income taxes	166	167
Pension and non-pension postretirement benefit contributions	(362)	(344)
Other assets and liabilities	(639)	(535)
Net cash flows provided by (used in) operating activities	6,675	5,673
Cash flows from investing activities
Capital expenditures	(5,497)	(5,556)
Proceeds from nuclear decommissioning trust fund sales	6,379	6,848
Investment in nuclear decommissioning trust funds	(6,553)	(7,044)
Acquisition of assets and businesses, net	(57)	(208)
Proceeds from sales of assets and businesses	90	219
Other investing activities	29	(2)
Net cash flows provided by (used in) investing activities	(5,609)	(5,743)
Cash flows from financing activities
Changes in short-term borrowings	(218)	(570)
Proceeds from short-term borrowings with maturities greater than 90 days	126	621
Repayments on short-term borrowings with maturities greater than 90 days	(1)	(610)
Issuance of long-term debt	2,664	2,616
Retirement of long-term debt	(1,480)	(1,728)
Retirement of long-term debt to financing trust	0	(250)
Sale of noncontrolling interest	0	396
Dividends paid on common stock	(999)	(921)
Common stock issued from treasury stock	0	1,150
Proceeds from employee stock plans	67	61
Other financing activities	(94)	(64)
Net cash flows provided by (used in) financing activities	65	701
Increase (Decrease) in cash and cash equivalents	1,131	631
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	1,190	914
Cash, Cash Equivalents and Restricted Cash at End of Period	2,321	1,545
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	667	508
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	2,608	2,231
Impairment of long-lived assets and losses on regulatory assets	49	485
Gain on sales of assets and businesses	(48)	(3)
Bargain purchase gain	0	(233)
Deferred income taxes and amortization of investment tax credits	(278)	(179)
Net fair value changes related to derivatives	73	160
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(21)	(429)
Other non-cash operating activities	187	132
Changes in assets and liabilities:
Accounts receivable	126	66
Receivables from and payables to affiliates, net	(7)	27
Inventories	(10)	(43)
Accounts payable and accrued expenses	(59)	(255)
Option premiums (paid) received, net	(36)	35
Collateral received (posted), net	228	(77)
Income taxes	220	154
Pension and non-pension postretirement benefit contributions	(134)	(122)
Other assets and liabilities	(154)	(187)
Net cash flows provided by (used in) operating activities	3,411	2,270
Cash flows from investing activities
Capital expenditures	(1,660)	(1,654)
Proceeds from nuclear decommissioning trust fund sales	6,379	6,848
Investment in nuclear decommissioning trust funds	(6,553)	(7,044)
Acquisition of assets and businesses, net	(57)	(208)
Proceeds from sales of assets and businesses	90	218
Other investing activities	(5)	(35)
Net cash flows provided by (used in) investing activities	(1,806)	(1,875)
Cash flows from financing activities
Changes in short-term borrowings	0	(620)
Proceeds from short-term borrowings with maturities greater than 90 days	1	121
Repayments on short-term borrowings with maturities greater than 90 days	(1)	(110)
Issuance of long-term debt	14	789
Retirement of long-term debt	(100)	(541)
Sale of noncontrolling interest	0	396
Changes in Exelon intercompany money pool	(54)	91
Distributions to member	(688)	(494)
Contributions from member	54	102
Other financing activities	(46)	(31)
Net cash flows provided by (used in) financing activities	(820)	(297)
Increase (Decrease) in cash and cash equivalents	785	98
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	554	448
Cash, Cash Equivalents and Restricted Cash at End of Period	1,339	546
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	523	447
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	696	631
Deferred income taxes and amortization of investment tax credits	214	455
Other non-cash operating activities	187	112
Changes in assets and liabilities:
Accounts receivable	(190)	31
Receivables from and payables to affiliates, net	8	346
Inventories	4	6
Accounts payable and accrued expenses	(38)	(706)
Collateral received (posted), net	(10)	(22)
Income taxes	(65)	(205)
Pension and non-pension postretirement benefit contributions	(41)	(38)
Other assets and liabilities	(170)	63
Net cash flows provided by (used in) operating activities	1,118	1,120
Cash flows from investing activities
Capital expenditures	(1,540)	(1,698)
Other investing activities	22	17
Net cash flows provided by (used in) investing activities	(1,518)	(1,681)
Cash flows from financing activities
Issuance of long-term debt	1,350	1,000
Retirement of long-term debt	(840)	(425)
Dividends paid on common stock	(345)	(316)
Contributions from parent	387	567
Other financing activities	(16)	(14)
Net cash flows provided by (used in) financing activities	536	812
Increase (Decrease) in cash and cash equivalents	136	251
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	144	58
Cash, Cash Equivalents and Restricted Cash at End of Period	280	309
PECO Energy Co [Member]
Cash flows from operating activities
Net income	336	327
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	224	213
Gain on sales of assets and businesses	(1)	0
Deferred income taxes and amortization of investment tax credits	5	37
Other non-cash operating activities	41	38
Changes in assets and liabilities:
Accounts receivable	(85)	45
Receivables from and payables to affiliates, net	1	(10)
Inventories	(13)	(5)
Accounts payable and accrued expenses	(1)	(41)
Income taxes	(16)	51
Pension and non-pension postretirement benefit contributions	(25)	(23)
Other assets and liabilities	26	(29)
Net cash flows provided by (used in) operating activities	492	603
Cash flows from investing activities
Capital expenditures	(615)	(537)
Changes in Exelon intercompany money pool	0	74
Other investing activities	6	6
Net cash flows provided by (used in) investing activities	(609)	(457)
Cash flows from financing activities
Issuance of long-term debt	700	325
Retirement of long-term debt	(500)	0
Dividends paid on common stock	(300)	(216)
Contributions from parent	71	16
Other financing activities	(22)	(4)
Net cash flows provided by (used in) financing activities	(51)	121
Increase (Decrease) in cash and cash equivalents	(168)	267
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	275	67
Cash, Cash Equivalents and Restricted Cash at End of Period	107	334
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	242	231
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	358	348
Deferred income taxes and amortization of investment tax credits	82	141
Other non-cash operating activities	42	52
Changes in assets and liabilities:
Accounts receivable	72	95
Receivables from and payables to affiliates, net	(4)	(13)
Inventories	(8)	(18)
Accounts payable and accrued expenses	(3)	(25)
Collateral received (posted), net	1	0
Income taxes	(48)	12
Pension and non-pension postretirement benefit contributions	(50)	(50)
Other assets and liabilities	(9)	(72)
Net cash flows provided by (used in) operating activities	675	701
Cash flows from investing activities
Capital expenditures	(667)	(615)
Other investing activities	8	6
Net cash flows provided by (used in) investing activities	(659)	(609)
Cash flows from financing activities
Changes in short-term borrowings	(77)	(45)
Issuance of long-term debt	300	300
Retirement of long-term debt	0	(41)
Retirement of long-term debt to financing trust	0	(250)
Dividends paid on common stock	(157)	(148)
Contributions from parent	18	77
Other financing activities	(2)	(5)
Net cash flows provided by (used in) financing activities	82	(112)
Increase (Decrease) in cash and cash equivalents	98	(20)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	18	50
Cash, Cash Equivalents and Restricted Cash at End of Period	116	30
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income	336	359
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	555	511
Deferred income taxes and amortization of investment tax credits	50	190
Other non-cash operating activities	109	66
Changes in assets and liabilities:
Accounts receivable	(89)	(42)
Receivables from and payables to affiliates, net	10	(13)
Inventories	0	(29)
Accounts payable and accrued expenses	115	(49)
Income taxes	(31)	82
Pension and non-pension postretirement benefit contributions	(66)	(74)
Other assets and liabilities	(144)	(206)
Net cash flows provided by (used in) operating activities	845	795
Cash flows from investing activities
Capital expenditures	(988)	(995)
Proceeds from sales of assets and businesses	0	1
Other investing activities	2	4
Net cash flows provided by (used in) investing activities	(986)	(990)
Cash flows from financing activities
Changes in short-term borrowings	(141)	96
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	300	202
Retirement of long-term debt	(33)	(127)
Changes in Exelon intercompany money pool	10	1
Distributions to member	(232)	(267)
Contributions from parent	237	758
Other financing activities	(6)	(2)
Net cash flows provided by (used in) financing activities	260	161
Increase (Decrease) in cash and cash equivalents	119	(34)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	95	236
Cash, Cash Equivalents and Restricted Cash at End of Period	214	202
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income	174	188
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	286	242
Deferred income taxes and amortization of investment tax credits	(5)	90
Other non-cash operating activities	42	8
Changes in assets and liabilities:
Accounts receivable	(36)	(43)
Receivables from and payables to affiliates, net	(9)	(10)
Inventories	6	(15)
Accounts payable and accrued expenses	104	(24)
Income taxes	(18)	80
Pension and non-pension postretirement benefit contributions	(11)	(69)
Other assets and liabilities	(137)	(99)
Net cash flows provided by (used in) operating activities	396	348
Cash flows from investing activities
Capital expenditures	(475)	(439)
Proceeds from sales of assets and businesses	0	1
Other investing activities	3	0
Net cash flows provided by (used in) investing activities	(472)	(438)
Cash flows from financing activities
Changes in short-term borrowings	38	(23)
Issuance of long-term debt	100	202
Retirement of long-term debt	(8)	(7)
Dividends paid on common stock	(128)	(133)
Contributions from parent	85	161
Other financing activities	(4)	(1)
Net cash flows provided by (used in) financing activities	83	199
Increase (Decrease) in cash and cash equivalents	7	109
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	40	42
Cash, Cash Equivalents and Restricted Cash at End of Period	47	151
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income	90	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	135	124
Deferred income taxes and amortization of investment tax credits	24	61
Other non-cash operating activities	16	6
Changes in assets and liabilities:
Accounts receivable	13	7
Receivables from and payables to affiliates, net	(14)	0
Inventories	(3)	(6)
Accounts payable and accrued expenses	18	0
Income taxes	0	33
Other assets and liabilities	13	(40)
Net cash flows provided by (used in) operating activities	292	292
Cash flows from investing activities
Capital expenditures	(254)	(294)
Other investing activities	1	1
Net cash flows provided by (used in) investing activities	(253)	(293)
Cash flows from financing activities
Changes in short-term borrowings	(216)	54
Issuance of long-term debt	200	0
Retirement of long-term debt	(4)	(14)
Dividends paid on common stock	(58)	(82)
Contributions from parent	150	0
Other financing activities	(3)	0
Net cash flows provided by (used in) financing activities	69	(42)
Increase (Decrease) in cash and cash equivalents	108	(43)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	2	46
Cash, Cash Equivalents and Restricted Cash at End of Period	110	3
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income	76	77
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion, including nuclear fuel and energy contract amortization	107	113
Deferred income taxes and amortization of investment tax credits	24	28
Other non-cash operating activities	24	21
Changes in assets and liabilities:
Accounts receivable	(66)	(7)
Receivables from and payables to affiliates, net	(3)	(5)
Inventories	(2)	(7)
Accounts payable and accrued expenses	21	9
Income taxes	(3)	(9)
Pension and non-pension postretirement benefit contributions	(6)	0
Other assets and liabilities	(12)	(62)
Net cash flows provided by (used in) operating activities	160	158
Cash flows from investing activities
Capital expenditures	(247)	(242)
Other investing activities	(1)	0
Net cash flows provided by (used in) investing activities	(248)	(242)
Cash flows from financing activities
Changes in short-term borrowings	37	65
Proceeds from short-term borrowings with maturities greater than 90 days	125	0
Retirement of long-term debt	(22)	(25)
Dividends paid on common stock	(46)	(53)
Net cash flows provided by (used in) financing activities	94	(13)
Increase (Decrease) in cash and cash equivalents	6	(97)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	31	133
Cash, Cash Equivalents and Restricted Cash at End of Period	$ 37	$ 36