Consolidated Statements of Cash Flows (Unaudited) (USD $)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash flows from operating activities
Net income	$ 787,000,000	$ 1,892,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	2,909,000,000	1,702,000,000
Impairment of assets held for sale	278,000,000	0
Deferred income taxes and amortization of investment tax credits	263,000,000	1,008,000,000
Net fair value changes related to derivatives	(377,000,000)	360,000,000
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(142,000,000)	90,000,000
Other non-cash operating activities	1,235,000,000	703,000,000
Changes in assets and liabilities:
Accounts receivable	240,000,000	3,000,000
Inventories	12,000,000	(44,000,000)
Accounts payable, accrued expenses and other current liabilities	(837,000,000)	(400,000,000)
Option premiums paid, net	(122,000,000)	59,000,000
Counterparty collateral (posted) received, net	408,000,000	(807,000,000)
Income taxes	465,000,000	532,000,000
Pension and non-pension postretirement benefit contributions	(131,000,000)	(2,089,000,000)
Other assets and liabilities	(431,000,000)	(92,000,000)
Net cash flows provided by operating activities	4,557,000,000	2,917,000,000
Cash flows from investing activities
Capital expenditures	(4,145,000,000)	(2,972,000,000)
Proceeds from nuclear decommissioning trust fund sales	6,262,000,000	3,120,000,000
Investment in nuclear decommissioning trust funds	(6,422,000,000)	(3,293,000,000)
Cash acquired from Constellation	964,000,000
Acquisitions		(380,000,000)
Proceeds from sales of investments	26,000,000	0
Purchases of investments	(13,000,000)	0
Change in restricted cash	(38,000,000)	(532,000,000)
Other investing activities	41,000,000	26,000,000
Net cash flows provided by (used in) investing activities	(3,325,000,000)	(4,031,000,000)
Cash flows from financing activities
Changes in short-term debt	(139,000,000)	462,000,000
Issuance of long-term debt	1,558,000,000	1,199,000,000
Retirement or repayment of long-term debt	(731,000,000)	(3,000,000)
Dividends paid on common stock	(1,226,000,000)	(1,044,000,000)
Dividends paid to former Constellation shareholders	(51,000,000)	0
Proceeds from employee stock plans	61,000,000	26,000,000
Other financing activities	(20,000,000)	(67,000,000)
Net cash flows used in financing activities	(548,000,000)	573,000,000
Increase (decrease) in cash and cash equivalents	684,000,000	(541,000,000)
Cash and cash equivalents at beginning of period	1,016,000,000	1,612,000,000
Cash and cash equivalents at end of period	1,700,000,000	1,071,000,000
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	419,000,000	1,325,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	2,178,000,000	1,131,000,000
Impairment of assets held for sale	278,000,000
Deferred income taxes and amortization of investment tax credits	69,000,000	336,000,000
Net fair value changes related to derivatives	(345,000,000)	360,000,000
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(142,000,000)	90,000,000
Other non-cash operating activities	422,000,000	362,000,000
Changes in assets and liabilities:
Accounts receivable	189,000,000	(165,000,000)
Receivables from and payables to affiliates, net	(58,000,000)	210,000,000
Inventories	34,000,000	(32,000,000)
Accounts payable, accrued expenses and other current liabilities	(546,000,000)	(1,000,000)
Option premiums paid, net	(122,000,000)	59,000,000
Counterparty collateral (posted) received, net	315,000,000	(804,000,000)
Income taxes	565,000,000	268,000,000
Pension and non-pension postretirement benefit contributions	(48,000,000)	(952,000,000)
Other assets and liabilities	(195,000,000)	(65,000,000)
Net cash flows provided by operating activities	3,013,000,000	2,122,000,000
Cash flows from investing activities
Capital expenditures	(2,602,000,000)	(1,865,000,000)
Proceeds from nuclear decommissioning trust fund sales	6,262,000,000	3,120,000,000
Investment in nuclear decommissioning trust funds	(6,422,000,000)	(3,293,000,000)
Cash acquired from Constellation	708,000,000	0
Acquisitions		(380,000,000)
Change in restricted cash	0	0
Other investing activities	(2,000,000)	(3,000,000)
Net cash flows provided by (used in) investing activities	(2,056,000,000)	(2,421,000,000)
Cash flows from financing activities
Changes in short-term debt	(41,000,000)	72,000,000
Issuance of long-term debt	957,000,000	0
Retirement or repayment of long-term debt	(138,000,000)	(2,000,000)
Distribution to member	(1,384,000,000)	(61,000,000)
Contributions from member	0	30,000,000
Other financing activities	(17,000,000)	(53,000,000)
Net cash flows used in financing activities	(623,000,000)	(14,000,000)
Increase (decrease) in cash and cash equivalents	334,000,000	(313,000,000)
Cash and cash equivalents at beginning of period	496,000,000	456,000,000
Cash and cash equivalents at end of period	830,000,000	143,000,000
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	219,000,000	295,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	458,000,000	405,000,000
Deferred income taxes and amortization of investment tax credits	198,000,000	527,000,000
Other non-cash operating activities	310,000,000	210,000,000
Changes in assets and liabilities:
Accounts receivable	22,000,000	(4,000,000)
Receivables from and payables to affiliates, net	(32,000,000)	(13,000,000)
Inventories	(11,000,000)	(11,000,000)
Accounts payable, accrued expenses and other current liabilities	(49,000,000)	(160,000,000)
Counterparty collateral (posted) received, net	93,000,000	(3,000,000)
Income taxes	116,000,000	211,000,000
Pension and non-pension postretirement benefit contributions	(19,000,000)	(871,000,000)
Other assets and liabilities	(124,000,000)	29,000,000
Net cash flows provided by operating activities	1,181,000,000	615,000,000
Cash flows from investing activities
Capital expenditures	(896,000,000)	(758,000,000)
Proceeds from sales of investments	26,000,000	4,000,000
Purchases of investments	(13,000,000)	(2,000,000)
Change in restricted cash	0	(536,000,000)
Other investing activities	12,000,000	16,000,000
Net cash flows provided by (used in) investing activities	(871,000,000)	(1,276,000,000)
Cash flows from financing activities
Changes in short-term debt	35,000,000	0
Issuance of long-term debt	0	1,199,000,000
Retirement or repayment of long-term debt	(450,000,000)	(1,000,000)
Contributions from parent	0	0
Dividends paid on common stock	(95,000,000)	(225,000,000)
Other financing activities	(3,000,000)	(6,000,000)
Net cash flows used in financing activities	(513,000,000)	967,000,000
Increase (decrease) in cash and cash equivalents	(203,000,000)	306,000,000
Cash and cash equivalents at beginning of period	234,000,000	50,000,000
Cash and cash equivalents at end of period	31,000,000	356,000,000
PECO Energy Co [Member]
Cash flows from operating activities
Net income	300,000,000	314,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	161,000,000	150,000,000
Deferred income taxes and amortization of investment tax credits	27,000,000	181,000,000
Other non-cash operating activities	96,000,000	74,000,000
Changes in assets and liabilities:
Accounts receivable	36,000,000	241,000,000
Receivables from and payables to affiliates, net	15,000,000	(217,000,000)
Inventories	10,000,000	0
Accounts payable, accrued expenses and other current liabilities	(75,000,000)	24,000,000
Income taxes	127,000,000	27,000,000
Pension and non-pension postretirement benefit contributions	(12,000,000)	(110,000,000)
Other assets and liabilities	(57,000,000)	(28,000,000)
Net cash flows provided by operating activities	628,000,000	656,000,000
Cash flows from investing activities
Capital expenditures	(274,000,000)	(321,000,000)
Changes in Exelon intercompany money pool	5,000,000	(91,000,000)
Change in restricted cash	2,000,000	(2,000,000)
Other investing activities	8,000,000	12,000,000
Net cash flows provided by (used in) investing activities	(259,000,000)	(402,000,000)
Cash flows from financing activities
Changes in short-term debt	0	0
Issuance of long-term debt	350,000,000	0
Contributions from parent	0	18,000,000
Dividends paid on common stock	(258,000,000)	(268,000,000)
Dividends paid on preferred securities	(3,000,000)	(3,000,000)
Other financing activities	(4,000,000)	(5,000,000)
Net cash flows used in financing activities	85,000,000	(258,000,000)
Increase (decrease) in cash and cash equivalents	454,000,000	(4,000,000)
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	(14,000,000)	99,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	218,000,000	205,000,000
Deferred income taxes and amortization of investment tax credits	101,000,000	93,000,000
Other non-cash operating activities	147,000,000	98,000,000
Changes in assets and liabilities:
Accounts receivable	11,000,000	90,000,000
Receivables from and payables to affiliates, net	4,000,000	(5,000,000)
Inventories	21,000,000	(20,000,000)
Accounts payable, accrued expenses and other current liabilities	(16,000,000)	(18,000,000)
Income taxes	(50,000,000)	56,000,000
Pension and non-pension postretirement benefit contributions	(13,000,000)	(17,000,000)
Other assets and liabilities	(86,000,000)	(154,000,000)
Net cash flows provided by operating activities	323,000,000	427,000,000
Cash flows from investing activities
Capital expenditures	(402,000,000)	(416,000,000)
Change in restricted cash	(19,000,000)	(22,000,000)
Other investing activities	8,000,000	0
Net cash flows provided by (used in) investing activities	(413,000,000)	(438,000,000)
Cash flows from financing activities
Changes in short-term debt		140,000,000
Issuance of long-term debt	250,000,000
Retirement or repayment of long-term debt	(141,000,000)	(30,000,000)
Contributions from parent	66,000,000
Dividends paid on common stock	0	(85,000,000)
Dividends paid on preferred securities	(10,000,000)	(10,000,000)
Other financing activities	(3,000,000)	(3,000,000)
Net cash flows used in financing activities	162,000,000	12,000,000
Increase (decrease) in cash and cash equivalents	$ 72,000,000	$ 1,000,000