Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities
Net income	$ 1,911	$ 956
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	3,999	4,009
Impairment of long-lived assets and losses on regulatory assets	488	274
Gain on sales of assets	(5)	(41)
Bargain purchase gain	(233)	0
Deferred income taxes and amortization of investment tax credits	439	623
Net fair value changes related to derivatives	149	100
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(429)	(243)
Other non-cash operating activities	603	1,224
Changes in assets and liabilities:
Accounts receivable	224	(296)
Inventories	(87)	21
Accounts payable and accrued expenses	(593)	296
Option premiums received (paid), net	35	(24)
Collateral (posted) received, net	(100)	757
Income taxes	167	527
Pension and non-pension postretirement benefit contributions	(344)	(283)
Other assets and liabilities	(547)	(537)
Net cash flows provided by (used in) operating activities	5,677	7,363
Cash flows from investing activities
Capital expenditures	(5,556)	(6,368)
Proceeds from nuclear decommissioning trust fund sales	6,848	7,914
Investment in nuclear decommissioning trust funds	(7,044)	(8,093)
Acquisition of businesses, net	(208)	(6,896)
Proceeds from termination of direct financing lease investment	0	360
Changes in restricted cash	(67)	(75)
Proceeds from sale of long-lived assets	219	49
Other investing activities	(2)	(110)
Net cash flows provided by (used in) investing activities	(5,810)	(13,219)
Cash flows from financing activities
Changes in short-term borrowings	(570)	(1,014)
Proceeds from short-term borrowings with maturities greater than 90 days	621	195
Repayments on short-term borrowings with maturities greater than 90 days	(610)	(452)
Issuance of long-term debt	2,616	4,488
Retirement of long-term debt	(1,728)	(944)
Retirement of long-term debt to financing trust	(250)
Restricted proceeds from issuance of long-term debt	0	(30)
Redemption of preference stock	0	(190)
Dividends paid on common stock	(921)	(873)
Common stock issued from treasury stock	1,150	0
Proceeds from employee stock plans	61	36
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	396
Other financing activities	(64)	35
Net cash flows provided by (used in) financing activities	701	1,251
Increase (Decrease) in cash and cash equivalents	568	(4,605)
Cash and cash equivalents at beginning of period	635	6,502
Cash and cash equivalents at end of period	1,203	1,897
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	491	556
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	2,231	2,516
Impairment of long-lived assets and losses on regulatory assets	485	209
Gain on sales of assets	(3)	(31)
Bargain purchase gain	(233)	0
Deferred income taxes and amortization of investment tax credits	(184)	(133)
Net fair value changes related to derivatives	160	112
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(429)	(243)
Other non-cash operating activities	132	129
Changes in assets and liabilities:
Accounts receivable	106	26
Receivables from and payables to affiliates, net	27	(56)
Inventories	(43)	18
Accounts payable and accrued expenses	(257)	9
Option premiums received (paid), net	35	(24)
Collateral (posted) received, net	(77)	759
Income taxes	154	202
Pension and non-pension postretirement benefit contributions	(122)	(122)
Other assets and liabilities	(203)	(204)
Net cash flows provided by (used in) operating activities	2,270	3,723
Cash flows from investing activities
Capital expenditures	(1,654)	(2,651)
Proceeds from nuclear decommissioning trust fund sales	6,848	7,914
Investment in nuclear decommissioning trust funds	(7,044)	(8,093)
Acquisition of businesses, net	(208)	(255)
Changes in restricted cash	(28)	(39)
Proceeds from sale of long-lived assets	218	30
Other investing activities	(35)	(184)
Net cash flows provided by (used in) investing activities	(1,903)	(3,278)
Cash flows from financing activities
Changes in short-term borrowings	(620)	0
Proceeds from short-term borrowings with maturities greater than 90 days	121	195
Repayments on short-term borrowings with maturities greater than 90 days	(110)	(152)
Issuance of long-term debt	789	338
Retirement of long-term debt	(541)	(164)
Change in Exelon intercompany money pool	91	(785)
Distributions to member	(494)	(167)
Contributions from member	102	142
Noncontrolling Interest, Increase from Sale of Parent Equity Interest	396
Other financing activities	(31)	92
Net cash flows provided by (used in) financing activities	(297)	(501)
Increase (Decrease) in cash and cash equivalents	70	(56)
Cash and cash equivalents at beginning of period	290	431
Cash and cash equivalents at end of period	360	375
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	447	297
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	631	574
Deferred income taxes and amortization of investment tax credits	455	398
Other non-cash operating activities	112	122
Changes in assets and liabilities:
Accounts receivable	31	(55)
Receivables from and payables to affiliates, net	346	(9)
Inventories	6	4
Accounts payable and accrued expenses	(706)	145
Collateral (posted) received, net	(22)	(2)
Income taxes	(205)	206
Pension and non-pension postretirement benefit contributions	(38)	(35)
Other assets and liabilities	63	104
Net cash flows provided by (used in) operating activities	1,120	1,749
Cash flows from investing activities
Capital expenditures	(1,698)	(1,950)
Changes in restricted cash	(50)	0
Other investing activities	17	31
Net cash flows provided by (used in) investing activities	(1,731)	(1,919)
Cash flows from financing activities
Changes in short-term borrowings	0	(284)
Issuance of long-term debt	1,000	1,200
Retirement of long-term debt	(425)	(665)
Dividends paid on common stock	(316)	(275)
Contributions from parent	567	188
Other financing activities	(14)	(17)
Net cash flows provided by (used in) financing activities	812	147
Increase (Decrease) in cash and cash equivalents	201	(23)
Cash and cash equivalents at beginning of period	56	67
Cash and cash equivalents at end of period	257	44
PECO Energy Co [Member]
Cash flows from operating activities
Net income	327	346
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	213	201
Deferred income taxes and amortization of investment tax credits	37	69
Other non-cash operating activities	38	49
Changes in assets and liabilities:
Accounts receivable	45	(50)
Receivables from and payables to affiliates, net	(10)	9
Inventories	(5)	5
Accounts payable and accrued expenses	(41)	(12)
Income taxes	51	43
Pension and non-pension postretirement benefit contributions	(23)	(29)
Other assets and liabilities	(29)	(49)
Net cash flows provided by (used in) operating activities	603	582
Cash flows from investing activities
Capital expenditures	(537)	(448)
Changes in Exelon intercompany money pool	74	0
Other investing activities	6	10
Net cash flows provided by (used in) investing activities	(457)	(438)
Cash flows from financing activities
Issuance of long-term debt	325	300
Restricted proceeds from issuance of long-term debt	0	(30)
Dividends paid on common stock	(216)	(208)
Contributions from parent	16	18
Other financing activities	(4)	(3)
Net cash flows provided by (used in) financing activities	121	77
Increase (Decrease) in cash and cash equivalents	267	221
Cash and cash equivalents at beginning of period	63	295
Cash and cash equivalents at end of period	330	516
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	231	191
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	348	307
Impairment of long-lived assets and losses on regulatory assets	0	52
Deferred income taxes and amortization of investment tax credits	141	54
Other non-cash operating activities	52	109
Changes in assets and liabilities:
Accounts receivable	95	(50)
Receivables from and payables to affiliates, net	(13)	(10)
Inventories	(18)	(7)
Accounts payable and accrued expenses	(25)	43
Income taxes	12	19
Pension and non-pension postretirement benefit contributions	(50)	(46)
Other assets and liabilities	(69)	(2)
Net cash flows provided by (used in) operating activities	704	660
Cash flows from investing activities
Capital expenditures	(615)	(611)
Changes in restricted cash	23	(22)
Other investing activities	6	19
Net cash flows provided by (used in) investing activities	(586)	(614)
Cash flows from financing activities
Changes in short-term borrowings	(45)	(210)
Issuance of long-term debt	300	850
Retirement of long-term debt	(41)	(39)
Retirement of long-term debt to financing trust	(250)	0
Redemption of preference stock	0	(190)
Dividends paid on preference stock	0	(8)
Dividends paid on common stock	(148)	(134)
Contributions from parent	77	28
Other financing activities	(5)	(11)
Net cash flows provided by (used in) financing activities	(112)	286
Increase (Decrease) in cash and cash equivalents	6	332
Cash and cash equivalents at beginning of period	23	9
Cash and cash equivalents at end of period	29	341
Pepco Holdings LLC [Member] | Successor [Member]
Cash flows from operating activities
Net income	359
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	511
Deferred income taxes and amortization of investment tax credits	190
Net fair value changes related to derivatives	0
Other non-cash operating activities	66
Changes in assets and liabilities:
Accounts receivable	(42)
Receivables from and payables to affiliates, net	(13)
Inventories	(29)
Accounts payable and accrued expenses	(49)
Income taxes	82
Pension and non-pension postretirement benefit contributions	(74)
Other assets and liabilities	(204)
Net cash flows provided by (used in) operating activities	797
Cash flows from investing activities
Capital expenditures	(995)
Purchases of investments	0
Changes in restricted cash	(1)
Proceeds from sale of long-lived assets	1
Other investing activities	4
Net cash flows provided by (used in) investing activities	(991)
Cash flows from financing activities
Changes in short-term borrowings	96
Proceeds from short-term borrowings with maturities greater than 90 days	0
Repayments on short-term borrowings with maturities greater than 90 days	(500)
Issuance of long-term debt	202
Retirement of long-term debt	(127)
Common stock issued for the Direct Stock Purchase and Dividend Reinvestment Plan and employee-related compensation	0
Change in Exelon intercompany money pool	1
Distributions to member	(267)
Contributions from member	758
Other financing activities	(2)
Net cash flows provided by (used in) financing activities	161
Increase (Decrease) in cash and cash equivalents	(33)
Cash and cash equivalents at beginning of period	170
Cash and cash equivalents at end of period	137	299
Pepco Holdings LLC [Member] | Predecessor [Member]
Cash flows from financing activities
Cash and cash equivalents at beginning of period		26
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income	188	20
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	242	221
Deferred income taxes and amortization of investment tax credits	90	96
Other non-cash operating activities	8	168
Changes in assets and liabilities:
Accounts receivable	(43)	(105)
Receivables from and payables to affiliates, net	(10)	44
Inventories	(15)	3
Accounts payable and accrued expenses	(24)	7
Income taxes	80	139
Pension and non-pension postretirement benefit contributions	(69)	(6)
Other assets and liabilities	(99)	(83)
Net cash flows provided by (used in) operating activities	348	504
Cash flows from investing activities
Capital expenditures	(439)	(392)
Purchases of investments	0	(32)
Changes in restricted cash	(1)	(31)
Proceeds from sale of long-lived assets	1	12
Other investing activities	0	8
Net cash flows provided by (used in) investing activities	(439)	(435)
Cash flows from financing activities
Changes in short-term borrowings	(23)	(64)
Issuance of long-term debt	202	2
Retirement of long-term debt	(7)	(5)
Dividends paid on common stock	(133)	(92)
Contributions from parent	161	187
Other financing activities	(1)	0
Net cash flows provided by (used in) financing activities	199	28
Increase (Decrease) in cash and cash equivalents	108	97
Cash and cash equivalents at beginning of period	9	5
Cash and cash equivalents at end of period	117	102
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income	107	(16)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	124	120
Deferred income taxes and amortization of investment tax credits	61	69
Other non-cash operating activities	6	99
Changes in assets and liabilities:
Accounts receivable	7	8
Receivables from and payables to affiliates, net	0	12
Inventories	(6)	0
Accounts payable and accrued expenses	0	(8)
Collateral (posted) received, net	0	1
Income taxes	33	52
Other assets and liabilities	(40)	(70)
Net cash flows provided by (used in) operating activities	292	267
Cash flows from investing activities
Capital expenditures	(294)	(260)
Proceeds from sale of long-lived assets	0	4
Other investing activities	1	2
Net cash flows provided by (used in) investing activities	(293)	(254)
Cash flows from financing activities
Changes in short-term borrowings	54	(88)
Retirement of long-term debt	(14)	0
Dividends paid on common stock	(82)	(39)
Contributions from parent	0	113
Net cash flows provided by (used in) financing activities	(42)	(14)
Increase (Decrease) in cash and cash equivalents	(43)	(1)
Cash and cash equivalents at beginning of period	46	5
Cash and cash equivalents at end of period	3	4
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income	77	(50)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	113	130
Deferred income taxes and amortization of investment tax credits	28	14
Other non-cash operating activities	21	138
Changes in assets and liabilities:
Accounts receivable	(7)	(32)
Receivables from and payables to affiliates, net	(5)	9
Inventories	(7)	(1)
Accounts payable and accrued expenses	9	10
Income taxes	(9)	184
Other assets and liabilities	(62)	(87)
Net cash flows provided by (used in) operating activities	158	315
Cash flows from investing activities
Capital expenditures	(242)	(227)
Changes in restricted cash	1	(4)
Proceeds from sale of long-lived assets	0	2
Other investing activities	0	2
Net cash flows provided by (used in) investing activities	(241)	(227)
Cash flows from financing activities
Changes in short-term borrowings	65	(5)
Retirement of long-term debt	(25)	(35)
Dividends paid on common stock	(53)	(24)
Contributions from parent	0	139
Other financing activities	0	(1)
Net cash flows provided by (used in) financing activities	(13)	74
Increase (Decrease) in cash and cash equivalents	(96)	162
Cash and cash equivalents at beginning of period	101	3
Cash and cash equivalents at end of period	$ 5	$ 165