Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities
Net income	$ 1,046	$ 430
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	2,591	2,396
Impairment of long-lived assets and losses on regulatory assets	445	239
Gain on sales of assets	(5)	(40)
Business Combination, Bargain Purchase, Gain Recognized, Amount	(226)	0
Deferred income taxes and amortization of investment tax credits	107	261
Unrealized Gain (Loss) on Derivatives	(230)	(194)
Gain (Loss) on Investments	(284)	(114)
Other non-cash operating activities	415	1,056
Changes in assets and liabilities:
Accounts receivable	342	86
Inventories	(23)	89
Accounts payable and accrued expenses	(811)	(363)
Option premiums paid, net	(8)	(10)
Collateral (posted) received, net	(173)	710
Income taxes	58	470
Pension and non-pension postretirement benefit contributions	(325)	(258)
Other assets and liabilities	(481)	(593)
Net cash flows provided by (used in) operating activities	2,898	4,553
Cash flows from investing activities
Capital expenditures	(3,845)	(4,489)
Proceeds from Sale of Property Held-for-sale	211	45
Proceeds from nuclear decommissioning trust fund sales	5,213	4,977
Investment in nuclear decommissioning trust funds	(5,339)	(5,094)
Acquisition of businesses, net	(212)	(6,642)
Proceeds from termination of direct financing lease investment	0	360
Change in restricted cash	1	15
Other investing activities	(9)	(49)
Net cash flows provided by (used in) investing activities	(3,980)	(10,877)
Cash flows from financing activities
Changes in short-term borrowings	422	(798)
Proceeds from short-term borrowings with maturities greater than 90 days	576	194
Repayments of Short-term Debt, Maturing in More than Three Months	(510)	(315)
Issuance of long-term debt	981	3,174
Retirement of long-term debt	(1,049)	(217)
Dividends paid on common stock	(607)	(582)
Proceeds from Issuance of Common Stock	1,150
Proceeds from employee stock plans	43	17
Other financing activities	(23)	(4)
Net cash flows provided by (used in) financing activities	983	1,469
Increase (Decrease) in cash and cash equivalents	(99)	(4,855)
Cash and cash equivalents at beginning of period	635	6,502
Cash and cash equivalents at end of period	536	1,647
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	144	285
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	1,415	1,467
Impairment of long-lived assets and losses on regulatory assets	445	179
Gain on sales of assets	(4)	(31)
Business Combination, Bargain Purchase, Gain Recognized, Amount	(226)	0
Deferred income taxes and amortization of investment tax credits	(173)	(59)
Unrealized Gain (Loss) on Derivatives	(235)	(199)
Gain (Loss) on Investments	(284)	(114)
Other non-cash operating activities	121	169
Changes in assets and liabilities:
Accounts receivable	192	123
Change Receivables Payables From Affiliates	8	(77)
Inventories	(5)	57
Accounts payable and accrued expenses	(328)	(228)
Option premiums paid, net	(8)	(10)
Collateral (posted) received, net	(163)	720
Income taxes	(99)	41
Pension and non-pension postretirement benefit contributions	(116)	(117)
Other assets and liabilities	(180)	(217)
Net cash flows provided by (used in) operating activities	974	2,387
Cash flows from investing activities
Capital expenditures	(1,189)	(2,051)
Proceeds from Sale of Property Held-for-sale	210	30
Proceeds from nuclear decommissioning trust fund sales	5,213	4,977
Investment in nuclear decommissioning trust funds	(5,339)	(5,094)
Acquisition of businesses, net	(212)	(1)
Change in restricted cash	(8)	25
Other investing activities	(32)	(96)
Net cash flows provided by (used in) investing activities	(1,357)	(2,210)
Cash flows from financing activities
Changes in short-term borrowings	(51)	0
Proceeds from Debt, Maturing in More than Three Months	76	194
Repayments of Debt, Maturing in More than Three Months	(10)	(15)
Issuance of long-term debt	779	173
Retirement of long-term debt	(295)	(131)
Distribution to member	(330)	(111)
Proceeds from Contributions from Affiliates	0	45
Change in Exelon intercompany money pool borrowings	196	(429)
Other financing activities	(7)	39
Net cash flows provided by (used in) financing activities	358	(235)
Increase (Decrease) in cash and cash equivalents	(25)	(58)
Cash and cash equivalents at beginning of period	290	431
Cash and cash equivalents at end of period	265	373
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	259	260
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	419	379
Deferred income taxes and amortization of investment tax credits	235	222
Other non-cash operating activities	58	83
Changes in assets and liabilities:
Accounts receivable	12	(36)
Change Receivables Payables From Affiliates	(4)	1
Inventories	(2)	7
Accounts payable and accrued expenses	(182)	(42)
Collateral (posted) received, net	(8)	(10)
Income taxes	4	261
Pension and non-pension postretirement benefit contributions	(37)	(35)
Other assets and liabilities	34	38
Net cash flows provided by (used in) operating activities	788	1,128
Cash flows from investing activities
Capital expenditures	(1,168)	(1,334)
Change in restricted cash	(10)	0
Other investing activities	12	21
Net cash flows provided by (used in) investing activities	(1,166)	(1,313)
Cash flows from financing activities
Changes in short-term borrowings	389	(259)
Issuance of long-term debt	0	1,200
Dividends paid on common stock	(211)	(183)
Contributions from parent	184	113
Other financing activities	(1)	(17)
Net cash flows provided by (used in) financing activities	361	854
Increase (Decrease) in cash and cash equivalents	(17)	669
Cash and cash equivalents at beginning of period	56	67
Cash and cash equivalents at end of period	39	736
PECO Energy Co [Member]
Cash flows from operating activities
Net income	215	224
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	141	134
Deferred income taxes and amortization of investment tax credits	39	51
Other non-cash operating activities	22	27
Changes in assets and liabilities:
Accounts receivable	26	(1)
Change Receivables Payables From Affiliates	(10)	(2)
Inventories	7	19
Accounts payable and accrued expenses	(30)	(19)
Income taxes	51	31
Pension and non-pension postretirement benefit contributions	(23)	(29)
Other assets and liabilities	(70)	(96)
Net cash flows provided by (used in) operating activities	368	339
Cash flows from investing activities
Capital expenditures	(367)	(299)
Changes in Exelon intercompany money pool	121	0
Other investing activities	4	8
Net cash flows provided by (used in) investing activities	(242)	(291)
Cash flows from financing activities
Dividends paid on common stock	(144)	(139)
Other financing activities	0	(1)
Net cash flows provided by (used in) financing activities	(144)	(140)
Increase (Decrease) in cash and cash equivalents	(18)	(92)
Cash and cash equivalents at beginning of period	63	295
Cash and cash equivalents at end of period	45	203
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	169	135
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	239	206
Impairment of long-lived assets and losses on regulatory assets	0	52
Deferred income taxes and amortization of investment tax credits	99	17
Other non-cash operating activities	35	60
Changes in assets and liabilities:
Accounts receivable	77	11
Change Receivables Payables From Affiliates	(7)	6
Inventories	(5)	6
Accounts payable and accrued expenses	(83)	(5)
Income taxes	26	46
Pension and non-pension postretirement benefit contributions	(47)	(42)
Other assets and liabilities	(31)	(3)
Net cash flows provided by (used in) operating activities	472	489
Cash flows from investing activities
Capital expenditures	(405)	(392)
Change in restricted cash	18	5
Other investing activities	4	12
Net cash flows provided by (used in) investing activities	(383)	(375)
Cash flows from financing activities
Changes in short-term borrowings	40	(2)
Retirement of long-term debt	(41)	(39)
Dividends paid on common stock	(99)	(90)
Dividends paid on preference stock	0	(6)
Contributions from parent	0	21
Other financing activities	0	(2)
Net cash flows provided by (used in) financing activities	(100)	(118)
Increase (Decrease) in cash and cash equivalents	(11)	(4)
Cash and cash equivalents at beginning of period	23	9
Cash and cash equivalents at end of period	12	5
Pepco Holdings LLC [Member] | Successor [Member]
Cash flows from operating activities
Net income	205
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	332
Gain (Loss) on Disposition of Assets	(1)
Deferred income taxes and amortization of investment tax credits	59
Unrealized Gain (Loss) on Derivatives	0
Other non-cash operating activities	28
Changes in assets and liabilities:
Accounts receivable	(3)
Change Receivables Payables From Affiliates	(7)
Inventories	(19)
Accounts payable and accrued expenses	(61)
Income taxes	87
Pension and non-pension postretirement benefit contributions	(68)
Other assets and liabilities	(149)
Net cash flows provided by (used in) operating activities	403
Cash flows from investing activities
Capital expenditures	(671)
Proceeds from Sale of Property Held-for-sale	1
Purchases of investments	0
Change in restricted cash	3
Other investing activities	0
Net cash flows provided by (used in) investing activities	(667)
Cash flows from financing activities
Changes in short-term borrowings	45
Proceeds from short-term borrowings with maturities greater than 90 days	0
Repayments of Debt, Maturing in More than Three Months	(500)
Issuance of long-term debt	202
Retirement of long-term debt	(120)
Common stock issued for the Direct Stock Purchase and Dividend Reinvestment Plan and employee-related compensation	0
Distribution to member	(131)
Contributions from parent	751
Change in Exelon intercompany money pool borrowings	0
Other financing activities	(2)
Net cash flows provided by (used in) financing activities	245
Increase (Decrease) in cash and cash equivalents	(19)
Cash and cash equivalents at beginning of period	170
Cash and cash equivalents at end of period	151	294
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	101	(60)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	160	144
Gain (Loss) on Disposition of Assets	(1)	0
Deferred income taxes and amortization of investment tax credits	35	20
Other non-cash operating activities	0	158
Changes in assets and liabilities:
Accounts receivable	(33)	(41)
Change Receivables Payables From Affiliates	(4)	47
Inventories	(10)	1
Accounts payable and accrued expenses	(45)	(19)
Income taxes	46	165
Pension and non-pension postretirement benefit contributions	(65)	(3)
Other assets and liabilities	(55)	(47)
Net cash flows provided by (used in) operating activities	129	365
Cash flows from investing activities
Capital expenditures	(291)	(256)
Proceeds from Sale of Property Held-for-sale	1	12
Acquisition of businesses, net		(33)
Purchases of investments	0	(31)
Change in restricted cash	(1)	(31)
Other investing activities	(2)	(1)
Net cash flows provided by (used in) investing activities	(293)	(307)
Cash flows from financing activities
Changes in short-term borrowings	(23)	(64)
Issuance of long-term debt	202	1
Retirement of long-term debt	(7)	(5)
Dividends paid on common stock	(58)	(55)
Contributions from parent	161	187
Other financing activities	(1)	0
Net cash flows provided by (used in) financing activities	274	64
Increase (Decrease) in cash and cash equivalents	110	122
Cash and cash equivalents at beginning of period	9	5
Cash and cash equivalents at end of period	119	127
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income	76	(60)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	79	76
Deferred income taxes and amortization of investment tax credits	33	23
Other non-cash operating activities	(3)	121
Changes in assets and liabilities:
Accounts receivable	12	30
Change Receivables Payables From Affiliates	(2)	15
Inventories	(3)	1
Accounts payable and accrued expenses	18	(2)
Collateral (posted) received, net	0	1
Income taxes	13	66
Other assets and liabilities	(29)	(51)
Net cash flows provided by (used in) operating activities	194	220
Cash flows from investing activities
Capital expenditures	(192)	(182)
Change in restricted cash	0	(1)
Other investing activities	1	3
Net cash flows provided by (used in) investing activities	(191)	(180)
Cash flows from financing activities
Changes in short-term borrowings	25	(105)
Retirement of long-term debt	(14)	0
Dividends paid on common stock	(54)	(38)
Contributions from parent	0	113
Net cash flows provided by (used in) financing activities	(43)	(30)
Increase (Decrease) in cash and cash equivalents	(40)	10
Cash and cash equivalents at beginning of period	46	5
Cash and cash equivalents at end of period	6	15
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income	36	(97)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	72	81
Deferred income taxes and amortization of investment tax credits	(8)	(28)
Other non-cash operating activities	7	138
Changes in assets and liabilities:
Accounts receivable	18	31
Change Receivables Payables From Affiliates	(6)	8
Inventories	(3)	(2)
Accounts payable and accrued expenses	3	6
Income taxes	11	181
Other assets and liabilities	(53)	(110)
Net cash flows provided by (used in) operating activities	77	208
Cash flows from investing activities
Capital expenditures	(175)	(164)
Proceeds from Sale of Property Held-for-sale	0	2
Change in restricted cash	2	1
Other investing activities	0	1
Net cash flows provided by (used in) investing activities	(173)	(160)
Cash flows from financing activities
Changes in short-term borrowings	42	(5)
Retirement of long-term debt	(17)	(22)
Dividends paid on common stock	(22)	(11)
Contributions from parent	0	139
Other financing activities	(1)	(1)
Net cash flows provided by (used in) financing activities	2	100
Increase (Decrease) in cash and cash equivalents	(94)	148
Cash and cash equivalents at beginning of period	101	3
Cash and cash equivalents at end of period	$ 7	$ 151