Consolidated Statements of Cash Flows (Unaudited) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities
Net income	$ 1,235	$ 787
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	2,844	2,909
Impairment of assets held for sale	0	278
Deferred income taxes and amortization of investment tax credits	(164)	263
Net fair value changes related to derivatives	(229)	(377)
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(95)	(142)
Other non-cash operating activities	738	1,235
Changes in assets and liabilities:
Accounts receivable	54	228
Inventories	(103)	12
Accounts payable, accrued expenses and other current liabilities	(243)	(817)
Option premiums paid, net	(38)	(122)
Counterparty collateral (posted) received, net	(73)	408
Income taxes	863	465
Pension and non-pension postretirement benefit contributions	(360)	(131)
Other assets and liabilities	(35)	(422)
Net cash flows provided by operating activities	4,394	4,574
Cash flows from investing activities
Capital expenditures	(3,887)	(4,162)
Proceeds from nuclear decommissioning trust fund sales	3,344	6,262
Investment in nuclear decommissioning trust funds	(3,518)	(6,422)
Proceeds from sale of long-lived assets	32
Cash acquired from Constellation	0	964
Acquisitions		0
Proceeds from sales of investments	20	26
Purchases of investments	(3)	(13)
Change in restricted cash	(23)	(38)
Other investing activities	65	41
Net cash flows provided by (used in) investing activities	(3,970)	(3,342)
Cash flows from financing activities
Payment of accounts receivable agreement	(210)
Changes in short-term debt	205	(139)
Issuance of long-term debt	2,031	1,558
Retirement or repayment of long-term debt	(1,156)	(731)
Redemption of preferred securities	(93)
Dividends paid on common stock	(981)	(1,226)
Dividends paid to former Constellation shareholders	0	(51)
Proceeds from employee stock plans	40	61
Other financing activities	(102)	(20)
Net cash flows used in financing activities	(266)	(548)
Increase (decrease) in cash and cash equivalents	158	684
Cash and cash equivalents at beginning of period	1,486	1,016
Cash and cash equivalents at end of period	1,644	1,700
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	795	419
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	1,937	2,178
Impairment of assets held for sale	0	278
Deferred income taxes and amortization of investment tax credits	183	69
Net fair value changes related to derivatives	(222)	(345)
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(95)	(142)
Other non-cash operating activities	375	422
Changes in assets and liabilities:
Accounts receivable	57	189
Receivables from and payables to affiliates, net	(2)	(58)
Inventories	(81)	34
Accounts payable, accrued expenses and other current liabilities	(162)	(546)
Option premiums paid, net	(38)	(122)
Counterparty collateral (posted) received, net	(123)	315
Income taxes	315	565
Pension and non-pension postretirement benefit contributions	(123)	(48)
Other assets and liabilities	(163)	(195)
Net cash flows provided by operating activities	2,657	3,013
Cash flows from investing activities
Capital expenditures	(1,995)	(2,602)
Proceeds from nuclear decommissioning trust fund sales	3,344	6,262
Investment in nuclear decommissioning trust funds	(3,518)	(6,422)
Proceeds from sale of long-lived assets	32
Cash acquired from Constellation	0	708
Acquisitions		0
Change in restricted cash	(30)	0
Other investing activities	18	(2)
Net cash flows provided by (used in) investing activities	(2,149)	(2,056)
Cash flows from financing activities
Changes in short-term debt	12	(41)
Change in Exelon intercompany money pool borrowings	0
Issuance of long-term debt	831	957
Retirement or repayment of long-term debt	(471)	(138)
Distribution to member	(550)	(1,384)
Contributions from member	0	0
Other financing activities	(73)	(17)
Net cash flows used in financing activities	(251)	(623)
Increase (decrease) in cash and cash equivalents	257	334
Cash and cash equivalents at beginning of period	671	496
Cash and cash equivalents at end of period	928	830
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	140	219
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	501	458
Deferred income taxes and amortization of investment tax credits	(152)	198
Other non-cash operating activities	26	310
Changes in assets and liabilities:
Accounts receivable	(21)	22
Receivables from and payables to affiliates, net	(32)	(32)
Inventories	(12)	(11)
Accounts payable, accrued expenses and other current liabilities	48	(49)
Counterparty collateral (posted) received, net	50	93
Income taxes	262	116
Pension and non-pension postretirement benefit contributions	(120)	(19)
Other assets and liabilities	160	(124)
Net cash flows provided by operating activities	850	1,181
Cash flows from investing activities
Capital expenditures	(1,074)	(896)
Proceeds from sales of investments	5	26
Purchases of investments	(3)	(13)
Change in restricted cash	(3)	0
Other investing activities	33	12
Net cash flows provided by (used in) investing activities	(1,042)	(871)
Cash flows from financing activities
Changes in short-term debt	153	35
Issuance of long-term debt	350	0
Retirement or repayment of long-term debt	(252)	(450)
Contributions from parent	0	0
Dividends paid on common stock	(165)	(95)
Other financing activities	(4)	(3)
Net cash flows used in financing activities	82	(513)
Increase (decrease) in cash and cash equivalents	(110)	(203)
Cash and cash equivalents at beginning of period	144	234
Cash and cash equivalents at end of period	34	31
PECO Energy Co [Member]
Cash flows from operating activities
Net income	292	300
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	171	161
Deferred income taxes and amortization of investment tax credits	35	27
Other non-cash operating activities	84	96
Changes in assets and liabilities:
Accounts receivable	41	36
Receivables from and payables to affiliates, net	(25)	15
Inventories	4	10
Accounts payable, accrued expenses and other current liabilities	9	(75)
Income taxes	66	127
Pension and non-pension postretirement benefit contributions	(10)	(12)
Other assets and liabilities	(47)	(57)
Net cash flows provided by operating activities	620	628
Cash flows from investing activities
Capital expenditures	(374)	(274)
Changes in intercompany money pool	(1)	5
Change in restricted cash	(1)	2
Other investing activities	8	8
Net cash flows provided by (used in) investing activities	(368)	(259)
Cash flows from financing activities
Changes in short-term debt	(210)	0
Issuance of long-term debt	550	350
Redemption of preferred securities	(93)
Dividends paid on common stock	(248)	(258)
Dividends paid on preferred securities	(1)	(3)
Other financing activities	(3)	(4)
Net cash flows used in financing activities	(5)	85
Increase (decrease) in cash and cash equivalents	247	454
Cash and cash equivalents at beginning of period	362	194
Cash and cash equivalents at end of period	609	648
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	160	(14)
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	252	218
Deferred income taxes and amortization of investment tax credits	105	101
Other non-cash operating activities	105	148
Changes in assets and liabilities:
Accounts receivable	(28)	0
Receivables from and payables to affiliates, net	(12)	2
Inventories	(15)	21
Accounts payable, accrued expenses and other current liabilities	(5)	4
Income taxes	6	(50)
Pension and non-pension postretirement benefit contributions	(16)	(13)
Other assets and liabilities	(119)	(77)
Net cash flows provided by operating activities	433	340
Cash flows from investing activities
Capital expenditures	(391)	(419)
Change in restricted cash	(20)	(19)
Other investing activities	2	8
Net cash flows provided by (used in) investing activities	(409)	(430)
Cash flows from financing activities
Changes in short-term debt	40	0
Issuance of long-term debt	300	250
Retirement or repayment of long-term debt	(433)	(141)
Contributions from parent	0	66
Dividends paid on common stock	0	0
Dividends paid on preferred securities	(10)	(10)
Change in restricted cash for dividends	0
Other financing activities	(3)	(3)
Net cash flows used in financing activities	(106)	162
Increase (decrease) in cash and cash equivalents	(82)	72
Cash and cash equivalents at beginning of period	89	49
Cash and cash equivalents at end of period	$ 7	$ 121