Consolidated Statements of Cash Flows (Unaudited) (USD $)	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash flows from operating activities
Net income	$ 490,000,000	$ 1,290,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	1,895,000,000	1,114,000,000
Impairment of long-lived assets	0	0
Deferred income taxes and amortization of investment tax credits	227,000,000	590,000,000
Net fair value changes related to derivatives	(323,000,000)	264,000,000
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(70,000,000)	(51,000,000)
Other non-cash operating activities	959,000,000	378,000,000
Changes in assets and liabilities:
Accounts receivable	414,000,000	0
Inventories	45,000,000	17,000,000
Accounts payable, accrued expenses and other current liabilities	(1,063,000,000)	(486,000,000)
Option premiums paid, net	(108,000,000)	38,000,000
Counterparty collateral (posted) received, net	451,000,000	(494,000,000)
Income taxes	259,000,000	691,000,000
Pension and non-pension postretirement benefit contributions	(90,000,000)	(2,089,000,000)
Other assets and liabilities	(357,000,000)	(249,000,000)
Net cash flows provided by operating activities	2,729,000,000	1,013,000,000
Cash flows from investing activities
Capital expenditures	(2,816,000,000)	(1,985,000,000)
Proceeds from nuclear decommissioning trust fund sales	5,371,000,000	1,657,000,000
Investment in nuclear decommissioning trust funds	(5,483,000,000)	(1,772,000,000)
Cash acquired from Constellation	964,000,000
Proceeds from sales of investments	12,000,000	0
Purchases of investments	(5,000,000)	0
Change in restricted cash	(15,000,000)	(2,000,000)
Other investing activities	(12,000,000)	28,000,000
Net cash flows provided by (used in) investing activities	(1,984,000,000)	(2,074,000,000)
Cash flows from financing activities
Changes in short-term debt	179,000,000	140,000,000
Issuance of long-term debt	850,000,000	599,000,000
Retirement or repayment of long-term debt	(649,000,000)	(2,000,000)
Dividends paid on common stock	(773,000,000)	(695,000,000)
Dividends paid to former Constellation shareholders	(51,000,000)	0
Proceeds from employee stock plans	42,000,000	15,000,000
Other financing activities	(10,000,000)	(46,000,000)
Net cash flows used in financing activities	(412,000,000)	11,000,000
Increase (decrease) in cash and cash equivalents	333,000,000	(1,050,000,000)
Cash and cash equivalents at beginning of period	1,016,000,000	1,612,000,000
Cash and cash equivalents at end of period	1,349,000,000	562,000,000
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	332,000,000	938,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	1,423,000,000	735,000,000
Deferred income taxes and amortization of investment tax credits	168,000,000	298,000,000
Net fair value changes related to derivatives	(307,000,000)	264,000,000
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(70,000,000)	(51,000,000)
Other non-cash operating activities	318,000,000	168,000,000
Changes in assets and liabilities:
Accounts receivable	306,000,000	(139,000,000)
Receivables from and payables to affiliates, net	(42,000,000)	223,000,000
Inventories	30,000,000	(5,000,000)
Accounts payable, accrued expenses and other current liabilities	(732,000,000)	(78,000,000)
Option premiums paid, net	(108,000,000)	38,000,000
Counterparty collateral (posted) received, net	443,000,000	(525,000,000)
Income taxes	314,000,000	270,000,000
Pension and non-pension postretirement benefit contributions	(35,000,000)	(952,000,000)
Other assets and liabilities	(174,000,000)	(108,000,000)
Net cash flows provided by operating activities	1,866,000,000	1,076,000,000
Cash flows from investing activities
Capital expenditures	(1,820,000,000)	(1,270,000,000)
Proceeds from nuclear decommissioning trust fund sales	5,371,000,000	1,657,000,000
Investment in nuclear decommissioning trust funds	(5,483,000,000)	(1,772,000,000)
Cash acquired from Constellation	708,000,000	0
Change in restricted cash	6,000,000	0
Other investing activities	(66,000,000)	(3,000,000)
Net cash flows provided by (used in) investing activities	(1,284,000,000)	(1,388,000,000)
Cash flows from financing activities
Changes in short-term debt	(42,000,000)	0
Issuance of long-term debt	850,000,000	0
Retirement or repayment of long-term debt	(56,000,000)	(1,000,000)
Distribution to member	(891,000,000)	0
Contributions from member	0	0
Other financing activities	(9,000,000)	(34,000,000)
Net cash flows used in financing activities	(148,000,000)	(35,000,000)
Increase (decrease) in cash and cash equivalents	434,000,000	(347,000,000)
Cash and cash equivalents at beginning of period	496,000,000	456,000,000
Cash and cash equivalents at end of period	930,000,000	109,000,000
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	129,000,000	183,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	300,000,000	270,000,000
Deferred income taxes and amortization of investment tax credits	116,000,000	184,000,000
Other non-cash operating activities	241,000,000	115,000,000
Changes in assets and liabilities:
Accounts receivable	(26,000,000)	(62,000,000)
Receivables from and payables to affiliates, net	(18,000,000)	(23,000,000)
Inventories	(7,000,000)	(7,000,000)
Accounts payable, accrued expenses and other current liabilities	(54,000,000)	(108,000,000)
Counterparty collateral (posted) received, net	8,000,000	31,000,000
Income taxes	149,000,000	321,000,000
Pension and non-pension postretirement benefit contributions	(12,000,000)	(871,000,000)
Other assets and liabilities	(104,000,000)	38,000,000
Net cash flows provided by operating activities	722,000,000	71,000,000
Cash flows from investing activities
Capital expenditures	(585,000,000)	(495,000,000)
Proceeds from sales of investments	12,000,000	4,000,000
Purchases of investments	(5,000,000)	(2,000,000)
Change in restricted cash	0	0
Other investing activities	11,000,000	20,000,000
Net cash flows provided by (used in) investing activities	(567,000,000)	(473,000,000)
Cash flows from financing activities
Changes in short-term debt	178,000,000	0
Issuance of long-term debt	0	599,000,000
Retirement or repayment of long-term debt	(450,000,000)	(1,000,000)
Contributions from parent	0	0
Dividends paid on common stock	(85,000,000)	(150,000,000)
Other financing activities	(3,000,000)	(2,000,000)
Net cash flows used in financing activities	(360,000,000)	446,000,000
Increase (decrease) in cash and cash equivalents	(205,000,000)	44,000,000
Cash and cash equivalents at beginning of period	234,000,000	50,000,000
Cash and cash equivalents at end of period	29,000,000	94,000,000
PECO Energy Co [Member]
Cash flows from operating activities
Net income	177,000,000	210,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	107,000,000	98,000,000
Deferred income taxes and amortization of investment tax credits	19,000,000	91,000,000
Other non-cash operating activities	66,000,000	44,000,000
Changes in assets and liabilities:
Accounts receivable	62,000,000	221,000,000
Receivables from and payables to affiliates, net	9,000,000	(218,000,000)
Inventories	26,000,000	29,000,000
Accounts payable, accrued expenses and other current liabilities	(83,000,000)	(11,000,000)
Income taxes	121,000,000	113,000,000
Pension and non-pension postretirement benefit contributions	(8,000,000)	(110,000,000)
Other assets and liabilities	(87,000,000)	(108,000,000)
Net cash flows provided by operating activities	409,000,000	359,000,000
Cash flows from investing activities
Capital expenditures	(179,000,000)	(209,000,000)
Changes in Exelon intercompany money pool	18,000,000	(171,000,000)
Change in restricted cash	(3,000,000)	(2,000,000)
Other investing activities	7,000,000	11,000,000
Net cash flows provided by (used in) investing activities	(157,000,000)	(371,000,000)
Cash flows from financing activities
Changes in short-term debt	0	0
Issuance of long-term debt	0	0
Retirement of long-term debt to financing affiliates	0	0
Contributions from parent	0	0
Dividends paid on common stock	(172,000,000)	(184,000,000)
Dividends paid on preferred securities	(2,000,000)	(2,000,000)
Repayment of receivable from parent	0	0
Other financing activities	0	(5,000,000)
Net cash flows used in financing activities	(174,000,000)	(191,000,000)
Increase (decrease) in cash and cash equivalents	78,000,000	(203,000,000)
Cash and cash equivalents at beginning of period	194,000,000	522,000,000
Cash and cash equivalents at end of period	272,000,000	319,000,000
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	(14,000,000)	97,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	150,000,000	144,000,000
Deferred income taxes and amortization of investment tax credits	91,000,000	59,000,000
Other non-cash operating activities	100,000,000	54,000,000
Changes in assets and liabilities:
Accounts receivable	92,000,000	94,000,000
Receivables from and payables to affiliates, net	(3,000,000)	(10,000,000)
Inventories	37,000,000	7,000,000
Accounts payable, accrued expenses and other current liabilities	(71,000,000)	(24,000,000)
Income taxes	(48,000,000)	56,000,000
Pension and non-pension postretirement benefit contributions	(8,000,000)	(7,000,000)
Other assets and liabilities	43,000,000	3,000,000
Net cash flows provided by operating activities	369,000,000	473,000,000
Cash flows from investing activities
Capital expenditures	(282,000,000)	(283,000,000)
Change in restricted cash	8,000,000	4,000,000
Other investing activities	(10,000,000)	0
Net cash flows provided by (used in) investing activities	(284,000,000)	(279,000,000)
Cash flows from financing activities
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	(6,000,000)	(6,000,000)
Other financing activities	0	(2,000,000)
Net cash flows used in financing activities	(81,000,000)	(123,000,000)
Increase (decrease) in cash and cash equivalents	4,000,000	71,000,000
Cash and cash equivalents at beginning of period	49,000,000	50,000,000
Cash and cash equivalents at end of period	$ 53,000,000	$ 121,000,000