Consolidated Statements of Cash Flows (Unaudited) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities
Net income	$ 1,820	$ 1,729	$ 1,171
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	3,868	3,779	4,079
Impairment of long-lived assets	687	171	284
Gain on consolidation and acquisition of businesses	(296)	0	0
(Gain) loss on sales of assets	(437)	(13)	7
(Gain) loss on sales of assets	(437)	(13)	7
Deferred income taxes and amortization of investment tax credits	502	119	615
Net fair value changes related to derivatives	716	(445)	(604)
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(210)	(170)	(157)
Other non-cash operating activities	1,054	718	1,364
Changes in assets and liabilities:
Accounts receivable	(318)	(97)	243
Inventories	(380)	(100)	26
Accounts payable, accrued expenses and other current liabilities	209	(90)	(632)
Option premiums received (paid), net	38	(36)	(114)
Counterparty collateral (posted) received, net	(1,478)	215	135
Income taxes	(143)	883	544
Pension and non-pension postretirement benefit contributions	(617)	(422)	(462)
Other assets and liabilities	(558)	102	(368)
Net cash flows provided by operating activities	4,457	6,343	6,131
Cash flows from investing activities
Capital expenditures	(6,077)	(5,395)	(5,789)
Proceeds from termination of direct financing lease investment	335	0	0
Proceeds from nuclear decommissioning trust fund sales	7,396	4,217	7,265
Investment in nuclear decommissioning trust funds	(7,551)	(4,450)	(7,483)
Acquisitions of businesses	(386)	0	(21)
Proceeds from sales of long-lived assets	1,719	32	371
Proceeds from sales of investments	7	22	28
Cash and restricted cash acquired from consolidations and acquisitions	140	0	964
Purchases of investments	(3)	(4)	(13)
Change in restricted cash	(104)	(43)	(34)
Distribution from CENG	13	115	0
Other investing activities	(88)	112	136
Net cash flows used in investing activities	(4,599)	(5,394)	(4,576)
Cash flows from financing activities
Payment of accounts receivable agreement	0	(210)	(15)
Changes in short-term borrowings	122	332	(197)
Issuance of long-term debt	3,463	2,055	2,027
Retirement of long-term debt	(1,545)	(1,589)	(1,145)
Redemption of preferred securities	0	(93)	0
Distribution to noncontrolling interest of consolidated VIE	(421)	0	0
Dividends paid on common stock	(1,065)	(1,249)	(1,716)
Proceeds from employee stock plans	35	47	72
Other financing activities	(178)	(119)	(111)
Net cash flows provided by (used in) financing activities	411	(826)	(1,085)
Increase in cash and cash equivalents	269	123	470
Cash and cash equivalents at beginning of period	1,609	1,486	1,016
Cash and cash equivalents at end of period	1,878	1,609	1,486
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	1,019	1,060	558
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	2,519	2,559	2,966
Impairment of long-lived assets	663	157	284
Gain on consolidation and acquisition of businesses	(296)	0	0
(Gain) loss on sales of assets	(437)	(13)	7
Deferred income taxes and amortization of investment tax credits	(198)	315	408
Net fair value changes related to derivatives	635	(448)	(611)
Net realized and unrealized gains on nuclear decommissioning trust fund investments	(210)	(170)	(157)
Other non-cash operating activities	346	270	518
Changes in assets and liabilities:
Accounts receivable	(215)	109	248
Receivables from and payables to affiliates, net	15	2	39
Inventories	(359)	(88)	31
Accounts payable, accrued expenses and other current liabilities	94	(109)	(499)
Option premiums received (paid), net	38	(36)	(114)
Counterparty collateral (posted) received, net	(1,507)	162	95
Income taxes	265	402	114
Pension and non-pension postretirement benefit contributions	(297)	(149)	(178)
Other assets and liabilities	(249)	(136)	(128)
Net cash flows provided by operating activities	1,826	3,887	3,581
Cash flows from investing activities
Capital expenditures	(3,012)	(2,752)	(3,554)
Proceeds from nuclear decommissioning trust fund sales	7,396	4,217	7,265
Investment in nuclear decommissioning trust funds	(7,551)	(4,450)	(7,483)
Acquisitions of businesses	(386)	0	(21)
Proceeds from sales of long-lived assets	1,719	32	371
Cash and restricted cash acquired from consolidations and acquisitions	140	0	708
Change in restricted cash	(87)	(64)	4
Distribution from CENG	13	115	0
Other investing activities	(43)	30	81
Changes in Exelon intercompany money pool	44	(44)	0
Net cash flows used in investing activities	(1,767)	(2,916)	(2,629)
Cash flows from financing activities
Changes in short-term borrowings	17	13	(52)
Issuance of long-term debt	1,112	854	1,076
Retirement of long-term debt	(586)	(570)	(145)
Distribution to noncontrolling interest of consolidated VIE	(421)	0	0
Other financing activities	(67)	(82)	(78)
Distribution to member	(645)	(625)	(1,626)
Contribution from member	53	26	48
Net cash flows provided by (used in) financing activities	(537)	(384)	(777)
Increase in cash and cash equivalents	(478)	587	175
Cash and cash equivalents at beginning of period	1,258	671	496
Cash and cash equivalents at end of period	780	1,258	671
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	408	249	379
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	687	669	610
(Gain) loss on sales of assets	(2)	0	0
Deferred income taxes and amortization of investment tax credits	433	(57)	270
Other non-cash operating activities	255	28	252
Changes in assets and liabilities:
Accounts receivable	(121)	(12)	24
Receivables from and payables to affiliates, net	(11)	(12)	(18)
Inventories	(16)	(18)	(11)
Accounts payable, accrued expenses and other current liabilities	53	74	59
Income taxes	(159)	178	9
Pension and non-pension postretirement benefit contributions	(248)	(122)	(138)
Other assets and liabilities	45	241	(102)
Net cash flows provided by operating activities	1,326	1,218	1,334
Cash flows from investing activities
Capital expenditures	(1,689)	(1,433)	(1,246)
Proceeds from sales of investments	7	7	28
Purchases of investments	(3)	(4)	(13)
Change in restricted cash	(2)	(2)	0
Other investing activities	32	45	19
Net cash flows used in investing activities	(1,655)	(1,387)	(1,212)
Cash flows from financing activities
Changes in short-term borrowings	120	184	0
Issuance of long-term debt	900	350	350
Retirement of long-term debt	(617)	(252)	(450)
Dividends paid on common stock	(307)	(220)	(105)
Other financing activities	(10)	(1)	(7)
Contributions from parent	273	0	0
Net cash flows provided by (used in) financing activities	359	61	(212)
Increase in cash and cash equivalents	30	(108)	(90)
Cash and cash equivalents at beginning of period	36	144	234
Cash and cash equivalents at end of period	66	36	144
PECO Energy Co [Member]
Cash flows from operating activities
Net income	352	395	381
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	236	228	217
Deferred income taxes and amortization of investment tax credits	88	20	37
Other non-cash operating activities	92	108	125
Changes in assets and liabilities:
Accounts receivable	(16)	(79)	(14)
Receivables from and payables to affiliates, net	(6)	(18)	13
Inventories	2	2	21
Accounts payable, accrued expenses and other current liabilities	54	41	(47)
Income taxes	(57)	87	174
Pension and non-pension postretirement benefit contributions	(16)	(31)	(45)
Other assets and liabilities	(17)	(6)	16
Net cash flows provided by operating activities	712	747	878
Cash flows from investing activities
Capital expenditures	(661)	(537)	(422)
Change in restricted cash	0	(2)	2
Other investing activities	12	8	10
Changes in Exelon intercompany money pool	0	0	82
Net cash flows used in investing activities	(649)	(531)	(328)
Cash flows from financing activities
Changes in short-term borrowings	0	(210)	(15)
Issuance of long-term debt	300	550	350
Retirement of long-term debt	(250)	(300)	(375)
Redemption of preferred securities	0	(93)	0
Dividends paid on common stock	(320)	(332)	(343)
Other financing activities	(4)	(2)	(4)
Contributions from parent	24	27	9
Dividends paid on preferred securities	0	(1)	(4)
Net cash flows provided by (used in) financing activities	(250)	(361)	(382)
Increase in cash and cash equivalents	(187)	(145)	168
Cash and cash equivalents at beginning of period	217	362	194
Cash and cash equivalents at end of period	30	217	362
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	211	210	4
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	371	348	298
Deferred income taxes and amortization of investment tax credits	116	125	104
Other non-cash operating activities	180	153	193
Changes in assets and liabilities:
Accounts receivable	46	(127)	(45)
Receivables from and payables to affiliates, net	(1)	(14)	26
Inventories	(6)	1	25
Accounts payable, accrued expenses and other current liabilities	(70)	(14)	(33)
Counterparty collateral (posted) received, net	27	0	0
Income taxes	45	(33)	14
Pension and non-pension postretirement benefit contributions	(16)	(24)	(16)
Other assets and liabilities	(163)	(64)	(85)
Net cash flows provided by operating activities	740	561	485
Cash flows from investing activities
Capital expenditures	(620)	(587)	(582)
Change in restricted cash	(22)	2	0
Other investing activities	20	14	9
Net cash flows used in investing activities	(622)	(571)	(573)
Cash flows from financing activities
Changes in short-term borrowings	(15)	135	0
Issuance of long-term debt	0	300	250
Retirement of long-term debt	(70)	(467)	(173)
Other financing activities	13	(3)	(2)
Contributions from parent	0	0	66
Dividends paid on preferred securities	(13)	(13)	(13)
Net cash flows provided by (used in) financing activities	(85)	(48)	128
Increase in cash and cash equivalents	33	(58)	40
Cash and cash equivalents at beginning of period	31	89	49
Cash and cash equivalents at end of period	$ 64	$ 31	$ 89