Consolidated Statements of Cash Flows (Unaudited) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities
Net income	$ 1,729	$ 1,171	$ 2,499
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	3,779	4,079	2,316
Impairment of assets held for sale		272
Deferred income taxes and amortization of investment tax credits	119	615	1,457
Net fair value changes related to derivatives	(445)	(604)	291
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(170)	(157)	14
Other non-cash operating activities	876	1,383	770
Changes in assets and liabilities:
Accounts receivable	(97)	243	57
Inventories	(100)	26	(58)
Accounts payable, accrued expenses and other current liabilities	(90)	(632)	(254)
Option premiums paid, net	(36)	(114)	(3)
Counterparty collateral (posted) received, net	215	135	(344)
Income taxes	883	544	492
Pension and non-pension postretirement benefit contributions	(422)	(462)	(2,360)
Other assets and liabilities	102	(368)	(24)
Net cash flows provided by operating activities	6,343	6,131	4,853
Cash flows from investing activities
Capital expenditures	(5,395)	(5,789)	(4,042)
Changes in intercompany money pool	(44)
Proceeds from nuclear decommissioning trust fund sales	4,217	7,265	6,139
Investment in nuclear decommissioning trust funds	(4,450)	(7,483)	(6,332)
Cash acquired from Constellation		964
Proceeds from sale of Three Maryland Generating Stations	32	371
Acquisitions		(21)	(387)
Distribution From Affiliates	115
Proceeds from sales of investments	22	28	6
Purchases of investments	(4)	(13)	(4)
Change in restricted cash	(43)	(34)	(3)
Other investing activities	112	136	20
Net cash flows provided by (used in) investing activities	(5,394)	(4,576)	(4,603)
Cash flows from financing activities
Payment of accounts receivable agreement	(210)	(15)
Changes in short-term debt	332	(197)	161
Redemption of preferred securities	(93)
Issuance of long-term debt	2,055	2,027	1,199
Retirement or repayment of long-term debt	(1,589)	(1,145)	(789)
Dividends paid on common stock	(1,249)	(1,716)	(1,393)
Proceeds from employee stock plans	47	72	38
Other financing activities	(119)	(111)	(62)
Net cash flows used in financing activities	(826)	(1,085)	(846)
Increase (decrease) in cash and cash equivalents	123	470	(596)
Cash and cash equivalents at beginning of period	1,486	1,016	1,612
Cash and cash equivalents at end of period	1,609	1,486	1,016
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	1,060	558	1,771
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	2,559	2,966	1,539
Impairment of assets held for sale	0	272	0
Deferred income taxes and amortization of investment tax credits	315	408	551
Net fair value changes related to derivatives	(448)	(611)	291
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(170)	(157)	14
Other non-cash operating activities	414	537	421
Changes in assets and liabilities:
Accounts receivable	109	248	(122)
Receivables from and payables to affiliates, net	2	39	208
Inventories	(88)	31	(47)
Accounts payable, accrued expenses and other current liabilities	(109)	(499)	34
Option premiums paid, net	(36)	(114)	(3)
Counterparty collateral (posted) received, net	162	95	(410)
Income taxes	402	114	193
Pension and non-pension postretirement benefit contributions	(149)	(178)	(1,070)
Other assets and liabilities	(136)	(128)	(57)
Net cash flows provided by operating activities	3,887	3,581	3,313
Cash flows from investing activities
Capital expenditures	(2,752)	(3,554)	(2,491)
Proceeds from nuclear decommissioning trust fund sales	4,217	7,265	6,139
Investment in nuclear decommissioning trust funds	(4,450)	(7,483)	(6,332)
Proceeds from sale of long-lived assets	32	371
Cash acquired from Constellation	0	708
Acquisitions	0	(21)	(387)
Distribution From Affiliates	115
Change in restricted cash	(64)	4	0
Other investing activities	30	81	(6)
Net cash flows provided by (used in) investing activities	(2,916)	(2,629)	(3,077)
Cash flows from financing activities
Changes in short-term debt	13	(52)
Issuance of long-term debt	854	1,076	0
Retirement or repayment of long-term debt	(570)	(145)	(2)
Distribution to member	(625)	(1,626)	(172)
Contributions from member	26	48	30
Other financing activities	(82)	(78)	(52)
Net cash flows used in financing activities	(384)	(777)	(196)
Increase (decrease) in cash and cash equivalents	587	175	40
Cash and cash equivalents at beginning of period	671	496	456
Cash and cash equivalents at end of period	1,258	671	496
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	249	379	416
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	669	610	554
Deferred income taxes and amortization of investment tax credits	(57)	270	700
Other non-cash operating activities	28	252	184
Changes in assets and liabilities:
Accounts receivable	(12)	24	5
Receivables from and payables to affiliates, net	(12)	(18)	(287)
Inventories	(18)	(11)	(9)
Accounts payable, accrued expenses and other current liabilities	74	59	(84)
Counterparty collateral (posted) received, net	53	40	66
Income taxes	178	9	223
Pension and non-pension postretirement benefit contributions	(122)	(138)	(977)
Other assets and liabilities	188	(142)	45
Net cash flows provided by operating activities	1,218	1,334	836
Cash flows from investing activities
Capital expenditures	(1,433)	(1,246)	(1,028)
Proceeds from sales of investments	7	28	6
Purchases of investments	(4)	(13)	(4)
Change in restricted cash	2
Other investing activities	45	19	19
Net cash flows provided by (used in) investing activities	(1,387)	(1,212)	(1,007)
Cash flows from financing activities
Changes in short-term debt	184	0	0
Issuance of long-term debt	350	350	1,199
Retirement or repayment of long-term debt	(252)	(450)	(537)
Contributions from parent	176
Dividends paid on common stock	(220)	(105)	(300)
Other financing activities	(1)	(7)	(7)
Net cash flows used in financing activities	61	(212)	355
Increase (decrease) in cash and cash equivalents	(108)	(90)	184
Cash and cash equivalents at beginning of period	144	234	50
Cash and cash equivalents at end of period	36	144	234
PECO Energy Co [Member]
Cash flows from operating activities
Net income	395	381	389
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	228	217	202
Deferred income taxes and amortization of investment tax credits	20	37	253
Other non-cash operating activities	108	125	100
Changes in assets and liabilities:
Accounts receivable	(79)	(14)	225
Receivables from and payables to affiliates, net	(18)	13	(217)
Inventories	2	21	0
Accounts payable, accrued expenses and other current liabilities	41	(47)	34
Income taxes	87	174	(45)
Pension and non-pension postretirement benefit contributions	(31)	(45)	(137)
Other assets and liabilities	(6)	16	14
Net cash flows provided by operating activities	747	878	818
Cash flows from investing activities
Capital expenditures	(537)	(422)	(481)
Changes in intercompany money pool	0	82	(82)
Change in restricted cash	(2)	2	(2)
Other investing activities	8	10	8
Net cash flows provided by (used in) investing activities	(531)	(328)	(557)
Cash flows from financing activities
Changes in short-term debt	(210)	(15)	0
Redemption of preferred securities	(93)	0	0
Issuance of long-term debt	550	350	0
Retirement or repayment of long-term debt	(300)	(375)	(250)
Retirement of long-term debt of variable interest entity	0	0	0
Retirement of long-term debt to financing affiliates	0	0	0
Contributions from parent	27	9	18
Dividends paid on common stock	(332)	(343)	(348)
Dividends paid on preferred securities	(1)	(4)	(4)
Repayment of receivable from parent	0	0	0
Other financing activities	(2)	(4)	(5)
Net cash flows used in financing activities	(361)	(382)	(589)
Increase (decrease) in cash and cash equivalents	(145)	168	(328)
Cash and cash equivalents at beginning of period	362	194	522
Cash and cash equivalents at end of period	217	362	194
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	210	4	136
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	348	298	274
Deferred income taxes and amortization of investment tax credits	125	104	145
Other non-cash operating activities	153	193	129
Changes in assets and liabilities:
Accounts receivable	(127)	(45)	60
Receivables from and payables to affiliates, net	(14)	26	(44)
Inventories	1	25	(10)
Accounts payable, accrued expenses and other current liabilities	(14)	(33)	(21)
Income taxes	(33)	14	35
Pension and non-pension postretirement benefit contributions	(24)	(16)	(67)
Other assets and liabilities	(64)	(85)	(161)
Net cash flows provided by operating activities	561	485	476
Cash flows from investing activities
Capital expenditures	(587)	(582)	(592)
Changes in intercompany money pool			0
Proceeds from sales of investments	0	0	0
Change in restricted cash	2	0	0
Other investing activities	14	9
Net cash flows provided by (used in) investing activities	(571)	(573)	(592)
Cash flows from financing activities
Changes in short-term debt	135	0	0
Issuance of long-term debt	300	250	300
Retirement or repayment of long-term debt	(467)	(173)	(82)
Contributions from parent	0	66	0
Dividends paid on common stock	0	0
Dividends paid on preferred securities	(13)	(13)	(13)
Other financing activities	(3)	(2)	(5)
Net cash flows used in financing activities	(48)	128	115
Increase (decrease) in cash and cash equivalents	(58)	40	(1)
Cash and cash equivalents at beginning of period	89	49	50
Cash and cash equivalents at end of period	$ 31	$ 89	$ 49