Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities
Net income	$ 1,179	$ 1,066
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	3,000	2,591
Impairment of long-lived assets and losses on regulatory assets	41	445
Gain on sales of assets and businesses	(60)	(5)
Bargain purchase gain	0	(226)
Deferred income taxes and amortization of investment tax credits	(2)	113
Net fair value changes related to derivatives	151	230
Net realized and unrealized losses (gains) on nuclear decommissioning trust fund investments	80	(284)
Other non-cash operating activities	479	415
Changes in assets and liabilities:
Accounts receivable	(105)	301
Inventories	60	(23)
Accounts payable and accrued expenses	(342)	(810)
Option premiums paid, net	(36)	(8)
Collateral received (posted), net	81	(173)
Income taxes	129	58
Pension and non-pension postretirement benefit contributions	(345)	(325)
Other assets and liabilities	(441)	(470)
Net cash flows provided by (used in) operating activities	3,869	2,895
Cash flows from investing activities
Capital expenditures	(3,807)	(3,845)
Proceeds from nuclear decommissioning trust fund sales	3,822	5,213
Investment in nuclear decommissioning trust funds	(3,924)	(5,339)
Acquisition of assets and businesses, net	(57)	(212)
Proceeds from sales of assets and businesses	89	211
Other investing activities	31	(9)
Net cash flows provided by (used in) investing activities	(3,846)	(3,981)
Cash flows from financing activities
Changes in short-term borrowings	200	422
Proceeds from short-term borrowings with maturities greater than 90 days	126	576
Repayments on short-term borrowings with maturities greater than 90 days	(1)	(510)
Issuance of long-term debt	1,488	981
Retirement of long-term debt	(1,309)	(1,049)
Dividends paid on common stock	(666)	(607)
Common stock issued from treasury stock		1,150
Proceeds from employee stock plans	27	43
Other financing activities	(50)	(23)
Net cash flows provided by (used in) financing activities	(185)	983
Increase (Decrease) in cash and cash equivalents	(162)	(103)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	1,190	914
Cash, Cash Equivalents and Restricted Cash at End of Period	1,028	811
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	368	164
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	1,735	1,415
Impairment of long-lived assets and losses on regulatory assets	41	445
Gain on sales of assets and businesses	(54)	(4)
Bargain purchase gain	0	(226)
Deferred income taxes and amortization of investment tax credits	(149)	(167)
Net fair value changes related to derivatives	158	235
Net realized and unrealized losses (gains) on nuclear decommissioning trust fund investments	80	(284)
Other non-cash operating activities	85	121
Changes in assets and liabilities:
Accounts receivable	258	151
Receivables from and payables to affiliates, net	7	8
Inventories	34	(5)
Accounts payable and accrued expenses	(272)	(327)
Option premiums paid, net	(36)	(8)
Collateral received (posted), net	91	(163)
Income taxes	58	(99)
Pension and non-pension postretirement benefit contributions	(129)	(116)
Other assets and liabilities	(212)	(166)
Net cash flows provided by (used in) operating activities	2,063	974
Cash flows from investing activities
Capital expenditures	(1,298)	(1,189)
Proceeds from nuclear decommissioning trust fund sales	3,822	5,213
Investment in nuclear decommissioning trust funds	(3,924)	(5,339)
Acquisition of assets and businesses, net	(57)	(212)
Proceeds from sales of assets and businesses	89	210
Changes in Exelon intercompany money pool	(185)	0
Other investing activities	4	(32)
Net cash flows provided by (used in) investing activities	(1,549)	(1,349)
Cash flows from financing activities
Changes in short-term borrowings	0	(51)
Proceeds from short-term borrowings with maturities greater than 90 days	1	76
Repayments on short-term borrowings with maturities greater than 90 days	(1)	(10)
Issuance of long-term debt	13	779
Retirement of long-term debt	(76)	(295)
Change in Exelon intercompany money pool	(54)	196
Distributions to member	(377)	(330)
Other financing activities	(24)	(7)
Net cash flows provided by (used in) financing activities	(518)	358
Increase (Decrease) in cash and cash equivalents	(4)	(17)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	554	448
Cash, Cash Equivalents and Restricted Cash at End of Period	550	431
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	329	259
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	459	419
Deferred income taxes and amortization of investment tax credits	84	235
Other non-cash operating activities	117	58
Changes in assets and liabilities:
Accounts receivable	(133)	12
Receivables from and payables to affiliates, net	15	(4)
Inventories	5	(2)
Accounts payable and accrued expenses	(41)	(182)
Collateral received (posted), net	(13)	(8)
Income taxes	(15)	4
Pension and non-pension postretirement benefit contributions	(39)	(37)
Other assets and liabilities	(166)	34
Net cash flows provided by (used in) operating activities	602	788
Cash flows from investing activities
Capital expenditures	(1,026)	(1,168)
Other investing activities	17	12
Net cash flows provided by (used in) investing activities	(1,009)	(1,156)
Cash flows from financing activities
Changes in short-term borrowings	320	389
Issuance of long-term debt	800	0
Retirement of long-term debt	(700)	0
Dividends paid on common stock	(229)	(211)
Contributions from parent	225	184
Other financing activities	(10)	(1)
Net cash flows provided by (used in) financing activities	406	361
Increase (Decrease) in cash and cash equivalents	(1)	(7)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	144	58
Cash, Cash Equivalents and Restricted Cash at End of Period	143	51
PECO Energy Co [Member]
Cash flows from operating activities
Net income	210	215
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	149	141
Deferred income taxes and amortization of investment tax credits	(10)	39
Other non-cash operating activities	22	22
Changes in assets and liabilities:
Accounts receivable	(43)	26
Receivables from and payables to affiliates, net	(4)	(10)
Inventories	4	7
Accounts payable and accrued expenses	(18)	(30)
Income taxes	19	51
Pension and non-pension postretirement benefit contributions	(25)	(23)
Other assets and liabilities	(50)	(70)
Net cash flows provided by (used in) operating activities	254	368
Cash flows from investing activities
Capital expenditures	(411)	(367)
Changes in Exelon intercompany money pool	0	121
Other investing activities	5	4
Net cash flows provided by (used in) investing activities	(406)	(242)
Cash flows from financing activities
Changes in short-term borrowings	50	0
Issuance of long-term debt	375	0
Retirement of long-term debt	(500)	0
Dividends paid on common stock	(293)	(144)
Change in Exelon intercompany money pool	233	0
Contributions from parent	41	0
Other financing activities	(6)	0
Net cash flows provided by (used in) financing activities	(100)	(144)
Increase (Decrease) in cash and cash equivalents	(252)	(18)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	275	67
Cash, Cash Equivalents and Restricted Cash at End of Period	23	49
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	179	169
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	248	239
Deferred income taxes and amortization of investment tax credits	39	99
Other non-cash operating activities	27	35
Changes in assets and liabilities:
Accounts receivable	73	77
Receivables from and payables to affiliates, net	(4)	(7)
Inventories	5	(5)
Accounts payable and accrued expenses	(48)	(83)
Income taxes	(45)	26
Pension and non-pension postretirement benefit contributions	(49)	(47)
Other assets and liabilities	39	(34)
Net cash flows provided by (used in) operating activities	464	469
Cash flows from investing activities
Capital expenditures	(434)	(405)
Other investing activities	6	4
Net cash flows provided by (used in) investing activities	(428)	(401)
Cash flows from financing activities
Changes in short-term borrowings	59	40
Retirement of long-term debt	0	(41)
Dividends paid on common stock	(105)	(99)
Net cash flows provided by (used in) financing activities	(46)	(100)
Increase (Decrease) in cash and cash equivalents	(10)	(32)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	18	50
Cash, Cash Equivalents and Restricted Cash at End of Period	8	18
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income	149	205
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	363	332
Gain on sales of long-lived assets	0	(1)
Deferred income taxes and amortization of investment tax credits	14	59
Other non-cash operating activities	71	28
Changes in assets and liabilities:
Accounts receivable	(28)	(3)
Receivables from and payables to affiliates, net	4	(7)
Inventories	8	(19)
Accounts payable and accrued expenses	66	(61)
Income taxes	13	87
Pension and non-pension postretirement benefit contributions	(62)	(68)
Other assets and liabilities	(111)	(149)
Net cash flows provided by (used in) operating activities	487	403
Cash flows from investing activities
Capital expenditures	(629)	(671)
Proceeds from sales of assets and businesses	0	1
Other investing activities	2	0
Net cash flows provided by (used in) investing activities	(627)	(670)
Cash flows from financing activities
Changes in short-term borrowings	(228)	45
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	(25)	(120)
Change in Exelon intercompany money pool	7	0
Distributions to member	(109)	(131)
Contributions from member	235	751
Other financing activities	(7)	(2)
Net cash flows provided by (used in) financing activities	298	245
Increase (Decrease) in cash and cash equivalents	158	(22)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	95	236
Cash, Cash Equivalents and Restricted Cash at End of Period	253	214
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income	85	101
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	188	160
Gain on sales of long-lived assets	0	(1)
Deferred income taxes and amortization of investment tax credits	(8)	35
Other non-cash operating activities	24	0
Changes in assets and liabilities:
Accounts receivable	(31)	(33)
Receivables from and payables to affiliates, net	(11)	(4)
Inventories	2	(10)
Accounts payable and accrued expenses	77	(45)
Income taxes	3	46
Pension and non-pension postretirement benefit contributions	(11)	(65)
Other assets and liabilities	(91)	(55)
Net cash flows provided by (used in) operating activities	227	129
Cash flows from investing activities
Capital expenditures	(287)	(291)
Proceeds from sales of assets and businesses	0	1
Other investing activities	2	(2)
Net cash flows provided by (used in) investing activities	(285)	(292)
Cash flows from financing activities
Changes in short-term borrowings	(26)	(23)
Issuance of long-term debt	100	202
Retirement of long-term debt	(7)	(7)
Dividends paid on common stock	(50)	(58)
Contributions from parent	85	161
Other financing activities	(4)	(1)
Net cash flows provided by (used in) financing activities	98	274
Increase (Decrease) in cash and cash equivalents	40	111
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	40	42
Cash, Cash Equivalents and Restricted Cash at End of Period	80	153
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income	57	76
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	88	79
Deferred income taxes and amortization of investment tax credits	9	33
Other non-cash operating activities	14	(3)
Changes in assets and liabilities:
Accounts receivable	18	12
Receivables from and payables to affiliates, net	(22)	(2)
Inventories	4	(3)
Accounts payable and accrued expenses	10	18
Income taxes	16	13
Other assets and liabilities	22	(29)
Net cash flows provided by (used in) operating activities	216	194
Cash flows from investing activities
Capital expenditures	(166)	(192)
Other investing activities	1	1
Net cash flows provided by (used in) investing activities	(165)	(191)
Cash flows from financing activities
Changes in short-term borrowings	(216)	25
Issuance of long-term debt	200	0
Retirement of long-term debt	(4)	(14)
Dividends paid on common stock	(40)	(54)
Contributions from parent	150	0
Other financing activities	(2)	0
Net cash flows provided by (used in) financing activities	88	(43)
Increase (Decrease) in cash and cash equivalents	139	(40)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	2	46
Cash, Cash Equivalents and Restricted Cash at End of Period	141	6
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income	15	36
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	69	72
Deferred income taxes and amortization of investment tax credits	6	(8)
Other non-cash operating activities	12	7
Changes in assets and liabilities:
Accounts receivable	(13)	18
Receivables from and payables to affiliates, net	(4)	(6)
Inventories	4	(3)
Accounts payable and accrued expenses	14	3
Income taxes	3	11
Pension and non-pension postretirement benefit contributions	(6)	0
Other assets and liabilities	(33)	(53)
Net cash flows provided by (used in) operating activities	67	77
Cash flows from investing activities
Capital expenditures	(170)	(175)
Other investing activities	(2)	0
Net cash flows provided by (used in) investing activities	(172)	(175)
Cash flows from financing activities
Changes in short-term borrowings	14	42
Proceeds from short-term borrowings with maturities greater than 90 days	125	0
Retirement of long-term debt	(15)	(17)
Dividends paid on common stock	(19)	(22)
Other financing activities	0	(1)
Net cash flows provided by (used in) financing activities	105	2
Increase (Decrease) in cash and cash equivalents	0	(96)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	31	133
Cash, Cash Equivalents and Restricted Cash at End of Period	$ 31	$ 37