Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net income	$ 636	$ 971
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	1,501	1,274
Impairment of long-lived assets and losses on regulatory assets	0	10
Gain on sales of assets and businesses	(56)	(4)
Bargain purchase gain	0	(226)
Deferred income taxes and amortization of investment tax credits	(14)	185
Net fair value changes related to derivatives	259	47
Net realized and unrealized gains (losses) on nuclear decommissioning trust fund investments	68	(175)
Other non-cash operating activities	240	118
Changes in assets and liabilities:
Accounts receivable	133	291
Inventories	167	109
Accounts payable and accrued expenses	(451)	(728)
Option premiums paid, net	(27)	(6)
Collateral posted, net	(214)	(110)
Income taxes	86	50
Pension and non-pension postretirement benefit contributions	(331)	(307)
Other assets and liabilities	(495)	(425)
Net cash flows provided by (used in) operating activities	1,502	1,074
Cash flows from investing activities
Capital expenditures	(1,880)	(2,009)
Proceeds from nuclear decommissioning trust fund sales	1,189	1,767
Investment in nuclear decommissioning trust funds	(1,248)	(1,833)
Acquisition of businesses, net	0	(212)
Proceeds from sales of assets and businesses	79	22
Other investing activities	3	(18)
Net cash flows provided by (used in) investing activities	(1,857)	(2,283)
Cash flows from financing activities
Changes in short-term borrowings	726	721
Proceeds from short-term borrowings with maturities greater than 90 days	1	560
Repayments on short-term borrowings with maturities greater than 90 days	(1)	(500)
Issuance of long-term debt	1,130	763
Retirement of long-term debt	(1,241)	(65)
Dividends paid on common stock	(333)	(303)
Proceeds from employee stock plans	12	12
Other financing activities	(30)	(4)
Net cash flows provided by (used in) financing activities	264	1,184
Increase (Decrease) in cash and cash equivalents	(91)	(25)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	1,190	914
Cash, Cash Equivalents and Restricted Cash at End of Period	1,099	889
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	186	399
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	858	678
Impairment of long-lived assets and losses on regulatory assets	0	10
Gain on sales of assets and businesses	(53)	(4)
Bargain purchase gain	0	(226)
Deferred income taxes and amortization of investment tax credits	(68)	108
Net fair value changes related to derivatives	264	51
Net realized and unrealized gains (losses) on nuclear decommissioning trust fund investments	68	(175)
Other non-cash operating activities	45	(10)
Changes in assets and liabilities:
Accounts receivable	194	173
Receivables from and payables to affiliates, net	(15)	23
Inventories	122	81
Accounts payable and accrued expenses	(317)	(236)
Option premiums paid, net	(27)	(6)
Collateral posted, net	(214)	(102)
Income taxes	79	(81)
Pension and non-pension postretirement benefit contributions	(125)	(110)
Other assets and liabilities	(142)	(153)
Net cash flows provided by (used in) operating activities	855	420
Cash flows from investing activities
Capital expenditures	(628)	(625)
Proceeds from nuclear decommissioning trust fund sales	1,189	1,767
Investment in nuclear decommissioning trust funds	(1,248)	(1,833)
Acquisition of businesses, net	0	(212)
Proceeds from sales of assets and businesses	79	22
Other investing activities	(7)	(29)
Net cash flows provided by (used in) investing activities	(615)	(910)
Cash flows from financing activities
Changes in short-term borrowings	165	(42)
Proceeds from short-term borrowings with maturities greater than 90 days	1	60
Repayments on short-term borrowings with maturities greater than 90 days	(1)	0
Issuance of long-term debt	4	762
Retirement of long-term debt	(29)	(30)
Change in Exelon intercompany money pool	0	(1)
Distributions to member	(188)	(164)
Other financing activities	(9)	(3)
Net cash flows provided by (used in) financing activities	(57)	582
Increase (Decrease) in cash and cash equivalents	183	92
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	554	448
Cash, Cash Equivalents and Restricted Cash at End of Period	737	540
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	165	141
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	228	208
Deferred income taxes and amortization of investment tax credits	50	137
Other non-cash operating activities	46	31
Changes in assets and liabilities:
Accounts receivable	39	92
Receivables from and payables to affiliates, net	(19)	(16)
Inventories	5	4
Accounts payable and accrued expenses	(158)	(236)
Collateral posted, net	(3)	(7)
Income taxes	(5)	(34)
Pension and non-pension postretirement benefit contributions	(38)	(35)
Other assets and liabilities	(176)	(49)
Net cash flows provided by (used in) operating activities	134	236
Cash flows from investing activities
Capital expenditures	(531)	(626)
Other investing activities	8	7
Net cash flows provided by (used in) investing activities	(523)	(619)
Cash flows from financing activities
Changes in short-term borrowings	317	365
Issuance of long-term debt	800	0
Retirement of long-term debt	(700)	0
Dividends paid on common stock	(114)	(105)
Contributions from parent	113	100
Other financing activities	(9)	(1)
Net cash flows provided by (used in) financing activities	407	359
Increase (Decrease) in cash and cash equivalents	18	(24)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	144	58
Cash, Cash Equivalents and Restricted Cash at End of Period	162	34
PECO Energy Co [Member]
Cash flows from operating activities
Net income	113	127
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	75	71
Deferred income taxes and amortization of investment tax credits	(4)	24
Other non-cash operating activities	21	23
Changes in assets and liabilities:
Accounts receivable	(51)	(25)
Receivables from and payables to affiliates, net	7	(10)
Inventories	12	19
Accounts payable and accrued expenses	6	(40)
Income taxes	5	25
Pension and non-pension postretirement benefit contributions	(24)	(23)
Other assets and liabilities	(141)	(85)
Net cash flows provided by (used in) operating activities	19	106
Cash flows from investing activities
Capital expenditures	(217)	(201)
Changes in Exelon intercompany money pool	0	131
Other investing activities	2	1
Net cash flows provided by (used in) investing activities	(215)	(69)
Cash flows from financing activities
Changes in short-term borrowings	220	0
Issuance of long-term debt	325	0
Retirement of long-term debt	(500)	0
Dividends paid on common stock	(287)	(72)
Change in Exelon intercompany money pool	194	0
Other financing activities	(5)	0
Net cash flows provided by (used in) financing activities	(53)	(72)
Increase (Decrease) in cash and cash equivalents	(249)	(35)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	275	67
Cash, Cash Equivalents and Restricted Cash at End of Period	26	32
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	128	125
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	134	128
Deferred income taxes and amortization of investment tax credits	22	72
Other non-cash operating activities	20	24
Changes in assets and liabilities:
Accounts receivable	(32)	(7)
Receivables from and payables to affiliates, net	0	(7)
Inventories	20	17
Accounts payable and accrued expenses	(9)	(81)
Income taxes	14	33
Pension and non-pension postretirement benefit contributions	(45)	(44)
Other assets and liabilities	61	(52)
Net cash flows provided by (used in) operating activities	313	208
Cash flows from investing activities
Capital expenditures	(224)	(206)
Other investing activities	1	4
Net cash flows provided by (used in) investing activities	(223)	(202)
Cash flows from financing activities
Changes in short-term borrowings	(32)	50
Dividends paid on common stock	(52)	(49)
Net cash flows provided by (used in) financing activities	(84)	1
Increase (Decrease) in cash and cash equivalents	6	7
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	18	50
Cash, Cash Equivalents and Restricted Cash at End of Period	24	57
Pepco Holdings LLC [Member]
Cash flows from operating activities
Net income	65	140
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	183	167
Deferred income taxes and amortization of investment tax credits	17	13
Other non-cash operating activities	53	(8)
Changes in assets and liabilities:
Accounts receivable	(9)	68
Receivables from and payables to affiliates, net	10	(8)
Inventories	4	(11)
Accounts payable and accrued expenses	44	(81)
Income taxes	(9)	55
Pension and non-pension postretirement benefit contributions	(55)	(66)
Other assets and liabilities	(24)	(75)
Net cash flows provided by (used in) operating activities	279	194
Cash flows from investing activities
Capital expenditures	(258)	(320)
Other investing activities	0	(3)
Net cash flows provided by (used in) investing activities	(258)	(323)
Cash flows from financing activities
Changes in short-term borrowings	57	145
Repayments on short-term borrowings with maturities greater than 90 days	0	(500)
Issuance of long-term debt	0	1
Retirement of long-term debt	(12)	(24)
Change in Exelon intercompany money pool	13	13
Distributions to member	(71)	(69)
Contributions from member	0	500
Net cash flows provided by (used in) financing activities	(13)	66
Increase (Decrease) in cash and cash equivalents	8	(63)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	95	236
Cash, Cash Equivalents and Restricted Cash at End of Period	103	173
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income	31	58
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	96	82
Deferred income taxes and amortization of investment tax credits	4	5
Other non-cash operating activities	10	(15)
Changes in assets and liabilities:
Accounts receivable	0	45
Receivables from and payables to affiliates, net	(18)	(6)
Inventories	(2)	(10)
Accounts payable and accrued expenses	36	(49)
Income taxes	(3)	20
Pension and non-pension postretirement benefit contributions	(7)	(64)
Other assets and liabilities	(21)	(37)
Net cash flows provided by (used in) operating activities	126	29
Cash flows from investing activities
Capital expenditures	(127)	(139)
Other investing activities	0	(5)
Net cash flows provided by (used in) investing activities	(127)	(144)
Cash flows from financing activities
Changes in short-term borrowings	34	144
Issuance of long-term debt	0	1
Dividends paid on common stock	(25)	(30)
Other financing activities	0	(1)
Net cash flows provided by (used in) financing activities	9	114
Increase (Decrease) in cash and cash equivalents	8	(1)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	40	42
Cash, Cash Equivalents and Restricted Cash at End of Period	48	41
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income	31	57
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	45	39
Deferred income taxes and amortization of investment tax credits	10	13
Other non-cash operating activities	19	(7)
Changes in assets and liabilities:
Accounts receivable	(1)	6
Receivables from and payables to affiliates, net	(16)	1
Inventories	7	1
Accounts payable and accrued expenses	18	14
Income taxes	(5)	21
Other assets and liabilities	7	(23)
Net cash flows provided by (used in) operating activities	115	122
Cash flows from investing activities
Capital expenditures	(65)	(82)
Other investing activities	0	2
Net cash flows provided by (used in) investing activities	(65)	(80)
Cash flows from financing activities
Changes in short-term borrowings	(5)	0
Retirement of long-term debt	(4)	(14)
Dividends paid on common stock	(36)	(30)
Net cash flows provided by (used in) financing activities	(45)	(44)
Increase (Decrease) in cash and cash equivalents	5	(2)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	2	46
Cash, Cash Equivalents and Restricted Cash at End of Period	7	44
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income	7	28
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization	33	35
Deferred income taxes and amortization of investment tax credits	2	(7)
Other non-cash operating activities	9	2
Changes in assets and liabilities:
Accounts receivable	(5)	14
Receivables from and payables to affiliates, net	(4)	(5)
Inventories	0	(1)
Accounts payable and accrued expenses	30	(5)
Income taxes	0	3
Pension and non-pension postretirement benefit contributions	(6)	0
Other assets and liabilities	(7)	(6)
Net cash flows provided by (used in) operating activities	59	58
Cash flows from investing activities
Capital expenditures	(63)	(88)
Other investing activities	(1)	1
Net cash flows provided by (used in) investing activities	(64)	(87)
Cash flows from financing activities
Changes in short-term borrowings	28	0
Retirement of long-term debt	(8)	(10)
Dividends paid on common stock	(9)	(10)
Net cash flows provided by (used in) financing activities	11	(20)
Increase (Decrease) in cash and cash equivalents	6	(49)
Cash, Cash Equivalents and Restricted Cash at Beginning of Period	31	133
Cash, Cash Equivalents and Restricted Cash at End of Period	$ 37	$ 84