Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities
Net income	$ 956	$ 1,959
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	4,009	2,930
Impairment of long-lived assets and losses on regulatory assets	274	25
Gain on sales of assets	(41)	(10)
Deferred income taxes and amortization of investment tax credits	623	241
Net fair value changes related to derivatives	100	(363)
Gain (Loss) on Investments	243	(221)
Other non-cash operating activities	1,224	856
Changes in assets and liabilities:
Inventories	21	65
Accounts receivable	(296)	175
Accounts payable and accrued expenses	296	(115)
Option premiums (paid) received, net	(24)	27
Increase (Decrease) Cash Collateral from Counterparties	757	115
Income taxes	527	300
Pension and non-pension postretirement benefit contributions	(283)	(430)
Other assets and liabilities	(537)	(322)
Net cash flows provided by operating activities	7,363	5,674
Cash flows from investing activities
Capital expenditures	(6,368)	(5,443)
Proceeds from nuclear decommissioning trust fund sales	7,914	4,551
Investment in nuclear decommissioning trust funds	(8,093)	(4,737)
Acquisition of businesses, net of cash acquired	(6,896)	(28)
Proceeds from Sale of Property Held-for-sale	49	145
Proceeds from termination of direct financing lease investment	360	0
Change in restricted cash	(75)	(70)
Other investing activities	(110)	(107)
Net cash flows used in investing activities	(13,219)	(5,689)
Cash flows from financing activities
Changes in short-term borrowings	(1,014)	230
Proceeds from short-term borrowings with maturities greater than 90 days	195	0
Issuance of long-term debt	4,488	5,909
Proceeds from (Repayments of) Other Long-term Debt	(30)	0
Retirement of long-term debt	(944)	(1,745)
Dividends paid on common stock	(873)	(819)
Proceeds from employee stock plans	36	24
Other financing activities	35	(65)
Repayments of Short-term Debt, Maturing in More than Three Months	(452)	0
Payments for Repurchase of Redeemable Preferred Stock	(190)	0
Net cash flows provided by financing activities	1,251	5,402
(Decrease) Increase in cash and cash equivalents	(4,605)	5,387
Cash and cash equivalents at beginning of period	6,502	1,878
Cash and cash equivalents at end of period	1,897	7,265
Proceeds from Issuance of Common Stock	0	1,868
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	556	1,208
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	2,516	1,887
Impairment of long-lived assets and losses on regulatory assets	209	1
Gain on sales of assets	(31)	(7)
Deferred income taxes and amortization of investment tax credits	(133)	21
Net fair value changes related to derivatives	112	(252)
Gain (Loss) on Investments	243	(221)
Other non-cash operating activities	129	227
Changes in assets and liabilities:
Inventories	18	69
Accounts receivable	26	252
Change Receivables Payables From Affiliates	(56)	16
Accounts payable and accrued expenses	9	(146)
Option premiums (paid) received, net	(24)	27
Increase (Decrease) Cash Collateral from Counterparties	759	186
Income taxes	202	(70)
Pension and non-pension postretirement benefit contributions	(122)	(189)
Other assets and liabilities	(204)	(245)
Net cash flows provided by operating activities	3,723	3,206
Cash flows from investing activities
Capital expenditures	(2,651)	(2,774)
Proceeds from nuclear decommissioning trust fund sales	7,914	4,551
Investment in nuclear decommissioning trust funds	(8,093)	(4,737)
Acquisition of businesses, net of cash acquired	(255)	(28)
Proceeds from Sale of Property Held-for-sale	30	144
Change in restricted cash	(39)	(84)
Other investing activities	(184)	(92)
Net cash flows used in investing activities	(3,278)	(3,020)
Cash flows from financing activities
Repayments of Debt, Maturing in More than Three Months	(152)	0
Issuance of long-term debt	338	1,307
Proceeds from Debt, Maturing in More than Three Months	195	0
Retirement of long-term debt	(164)	(64)
Repayments of Related Party Debt	0	(550)
Other financing activities	92	(6)
Distribution to member	(167)	(2,368)
Proceeds from Contributions from Affiliates	142	55
Change in Exelon intercompany money pool borrowings	(785)	1,205
Net cash flows provided by financing activities	(501)	(421)
(Decrease) Increase in cash and cash equivalents	(56)	(235)
Cash and cash equivalents at beginning of period	431	780
Cash and cash equivalents at end of period	375	545
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	297	339
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	574	528
Gain on sales of assets	(6)	0
Deferred income taxes and amortization of investment tax credits	398	107
Other non-cash operating activities	122	312
Changes in assets and liabilities:
Inventories	4	(23)
Accounts receivable	(55)	(114)
Change Receivables Payables From Affiliates	(9)	(23)
Accounts payable and accrued expenses	145	(18)
Increase (Decrease) Cash Collateral from Counterparties	(2)	(43)
Income taxes	206	389
Pension and non-pension postretirement benefit contributions	(35)	(142)
Other assets and liabilities	104	34
Net cash flows provided by operating activities	1,749	1,346
Cash flows from investing activities
Capital expenditures	(1,950)	(1,670)
Change in restricted cash	0	2
Other investing activities	31	22
Net cash flows used in investing activities	(1,919)	(1,646)
Cash flows from financing activities
Changes in short-term borrowings	(284)	300
Issuance of long-term debt	1,200	400
Retirement of long-term debt	(665)	(260)
Dividends paid on common stock	(275)	(226)
Other financing activities	(17)	(4)
Contributions from parent	188	75
Net cash flows provided by financing activities	147	285
(Decrease) Increase in cash and cash equivalents	(23)	(15)
Cash and cash equivalents at beginning of period	67	66
Cash and cash equivalents at end of period	44	51
PECO Energy Co [Member]
Cash flows from operating activities
Net income	346	299
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	201	198
Deferred income taxes and amortization of investment tax credits	69	11
Other non-cash operating activities	49	69
Changes in assets and liabilities:
Inventories	5	8
Accounts receivable	(50)	(15)
Change Receivables Payables From Affiliates	9	0
Accounts payable and accrued expenses	(12)	(19)
Income taxes	43	69
Pension and non-pension postretirement benefit contributions	(29)	(37)
Other assets and liabilities	(49)	(16)
Net cash flows provided by operating activities	582	567
Cash flows from investing activities
Capital expenditures	(448)	(435)
Change in restricted cash	0	(1)
Other investing activities	10	11
Net cash flows used in investing activities	(438)	(425)
Cash flows from financing activities
Issuance of long-term debt	300	0
Proceeds from (Repayments of) Other Long-term Debt	(30)	0
Dividends paid on common stock	(208)	(209)
Other financing activities	(3)	(2)
Contributions from parent	18	16
Change in Exelon intercompany money pool borrowings		55
Net cash flows provided by financing activities	77	(140)
(Decrease) Increase in cash and cash equivalents	221	2
Cash and cash equivalents at beginning of period	295	30
Cash and cash equivalents at end of period	516	32
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	191	212
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	307	271
Impairment of long-lived assets and losses on regulatory assets	52
Gain on sales of assets		(1)
Deferred income taxes and amortization of investment tax credits	54	79
Other non-cash operating activities	109	111
Changes in assets and liabilities:
Inventories	(7)	10
Accounts receivable	(50)	62
Change Receivables Payables From Affiliates	(10)	(8)
Accounts payable and accrued expenses	43	34
Increase (Decrease) Cash Collateral from Counterparties	0	(27)
Income taxes	19	(6)
Pension and non-pension postretirement benefit contributions	(46)	(14)
Other assets and liabilities	(2)	(28)
Net cash flows provided by operating activities	660	696
Cash flows from investing activities
Capital expenditures	(611)	(506)
Change in restricted cash	(22)	2
Other investing activities	19	13
Net cash flows used in investing activities	(614)	(491)
Cash flows from financing activities
Changes in short-term borrowings	(210)	(70)
Issuance of long-term debt	850	0
Proceeds from (Repayments of) Other Long-term Debt	(190)
Retirement of long-term debt	(39)	(37)
Dividends paid on common stock	(134)	(116)
Other financing activities	(11)	(15)
Contributions from parent	28	6
Dividends paid on preference stock	(8)	(10)
Net cash flows provided by financing activities	286	(242)
(Decrease) Increase in cash and cash equivalents	332	(37)
Cash and cash equivalents at beginning of period	9	64
Cash and cash equivalents at end of period	341	27
Pepco Holdings LLC [Member] | Successor [Member]
Cash flows from financing activities
Cash and cash equivalents at end of period	299
Pepco Holdings LLC [Member] | Predecessor [Member]
Cash flows from operating activities
Net income		197
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization		474
Deferred income taxes and amortization of investment tax credits		107
Net fair value changes related to derivatives		(15)
Other non-cash operating activities		143
Changes in assets and liabilities:
Inventories		(5)
Accounts receivable		(211)
Change Receivables Payables From Affiliates		0
Accounts payable and accrued expenses		23
Increase (Decrease) Cash Collateral from Counterparties		0
Income taxes		12
Pension and non-pension postretirement benefit contributions		(12)
Other assets and liabilities		(112)
Net cash flows provided by operating activities		601
Cash flows from investing activities
Capital expenditures		(855)
Purchases of investments		0
Change in restricted cash		6
Other investing activities		14
Net cash flows used in investing activities		(835)
Cash flows from financing activities
Changes in short-term borrowings		99
Proceeds from short-term borrowings with maturities greater than 90 days		300
Issuance of long-term debt		408
Retirement of long-term debt		(163)
Dividends paid on common stock		(206)
Common stock issued for the Direct Stock Purchase and Dividend Reinvestment Plan and employee-related compensation		23
Distribution to member		0
Other financing activities		(24)
Contributions from parent		0
Change in Exelon intercompany money pool borrowings		0
Issuance of preferred stock		54
Net cash flows provided by financing activities		491
(Decrease) Increase in cash and cash equivalents		257
Cash and cash equivalents at beginning of period	26	15
Cash and cash equivalents at end of period		272
Potomac Electric Power Company [Member]
Cash flows from operating activities
Net income	20	128
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	221	191
Deferred income taxes and amortization of investment tax credits	96	70
Other non-cash operating activities	168	42
Changes in assets and liabilities:
Inventories	3	(5)
Accounts receivable	(105)	(113)
Change Receivables Payables From Affiliates	44	2
Accounts payable and accrued expenses	7	(1)
Income taxes	139	0
Pension and non-pension postretirement benefit contributions	(6)	(7)
Other assets and liabilities	(83)	(94)
Net cash flows provided by operating activities	504	213
Cash flows from investing activities
Capital expenditures	(392)	(374)
Proceeds from Sale of Property Held-for-sale	12
Purchases of investments	(32)	0
Change in restricted cash	(31)	3
Other investing activities	8	14
Net cash flows used in investing activities	(435)	(357)
Cash flows from financing activities
Changes in short-term borrowings	(64)	(56)
Issuance of long-term debt	2	208
Retirement of long-term debt	(5)	(17)
Dividends paid on common stock	(92)	(91)
Other financing activities	0	(8)
Contributions from parent	187	112
Net cash flows provided by financing activities	28	148
(Decrease) Increase in cash and cash equivalents	97	4
Cash and cash equivalents at beginning of period	5	6
Cash and cash equivalents at end of period	102	10
Potomac Electric Power Company [Member] | Successor [Member]
Cash flows from investing activities
Acquisition of businesses, net of cash acquired	(33)
Delmarva Power and Light Company [Member]
Cash flows from operating activities
Net income	(16)	55
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	120	113
Deferred income taxes and amortization of investment tax credits	69	40
Other non-cash operating activities	99	31
Changes in assets and liabilities:
Inventories	0	4
Accounts receivable	8	(33)
Change Receivables Payables From Affiliates	12	5
Accounts payable and accrued expenses	(8)	(5)
Increase (Decrease) Cash Collateral from Counterparties	1	0
Income taxes	52	0
Other assets and liabilities	(70)	(22)
Net cash flows provided by operating activities	267	188
Cash flows from investing activities
Capital expenditures	(260)	(246)
Proceeds from Sale of Property Held-for-sale	4
Change in restricted cash	0	5
Other investing activities	2	1
Net cash flows used in investing activities	(254)	(240)
Cash flows from financing activities
Changes in short-term borrowings	(88)	(40)
Issuance of long-term debt	0	200
Retirement of long-term debt	0	(100)
Dividends paid on common stock	(39)	(80)
Other financing activities	0	(2)
Contributions from parent	113	75
Net cash flows provided by financing activities	(14)	53
(Decrease) Increase in cash and cash equivalents	(1)	1
Cash and cash equivalents at beginning of period	5	4
Cash and cash equivalents at end of period	4	5
Atlantic City Electric Company [Member]
Cash flows from operating activities
Net income	(50)	37
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization, depletion and accretion, including nuclear fuel and energy contract amortization	130	135
Deferred income taxes and amortization of investment tax credits	14	13
Other non-cash operating activities	138	27
Changes in assets and liabilities:
Inventories	(1)	(1)
Accounts receivable	(32)	(87)
Change Receivables Payables From Affiliates	9	1
Accounts payable and accrued expenses	10	35
Income taxes	184	10
Other assets and liabilities	(87)	8
Net cash flows provided by operating activities	315	178
Cash flows from investing activities
Capital expenditures	(227)	(212)
Proceeds from Sale of Property Held-for-sale	2
Change in restricted cash	(4)	(6)
Other investing activities	2	2
Net cash flows used in investing activities	(227)	(216)
Cash flows from financing activities
Changes in short-term borrowings	(5)	98
Retirement of long-term debt	(35)	(46)
Dividends paid on common stock	(24)	(12)
Other financing activities	(1)	0
Contributions from parent	139	0
Net cash flows provided by financing activities	74	40
(Decrease) Increase in cash and cash equivalents	162	2
Cash and cash equivalents at beginning of period	3	2
Cash and cash equivalents at end of period	$ 165	$ 4