Consolidated Statements of Cash Flows (Unaudited) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities
Net income	$ 200,000,000	$ 669,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	776,000,000	552,000,000
Impairment of long-lived assets	0	0
Deferred income taxes and amortization of investment tax credits	101,000,000	340,000,000
Net fair value changes related to derivatives	(73,000,000)	148,000,000
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(103,000,000)	(40,000,000)
Other non-cash operating activities	(530,000,000)	(223,000,000)
Changes in assets and liabilities:
Accounts receivable	394,000,000	53,000,000
Inventories	104,000,000	78,000,000
Accounts payable, accrued expenses and other current liabilities	(1,176,000,000)	(526,000,000)
Option premiums paid, net	(100,000,000)	19,000,000
Counterparty collateral (posted) received, net	340,000,000	(150,000,000)
Income taxes	178,000,000	733,000,000
Pension and non-pension postretirement benefit contributions	(55,000,000)	(2,088,000,000)
Other assets and liabilities	(122,000,000)	(218,000,000)
Net cash flows provided by operating activities	994,000,000	(207,000,000)
Cash flows from investing activities
Capital expenditures	(1,496,000,000)	(1,150,000,000)
Proceeds from nuclear decommissioning trust fund sales	3,680,000,000	1,195,000,000
Investment in nuclear decommissioning trust funds	(3,726,000,000)	(1,247,000,000)
Acquisitions	(964,000,000)
Proceeds from sales of investments	10,000,000	1,000,000
Purchases of investments	(5,000,000)	(1,000,000)
Change in restricted cash	(8,000,000)	8,000,000
Other investing activities	(59,000,000)	15,000,000
Net cash flows provided by (used in) investing activities	(640,000,000)	(1,179,000,000)
Cash flows from financing activities
Changes in short-term debt	141,000,000	50,000,000
Issuance of long-term debt	0	599,000,000
Retirement of long-term debt	(451,000,000)	(1,000,000)
Dividends paid on common stock	(350,000,000)	(348,000,000)
Proceeds from employee stock plans	12,000,000	8,000,000
Other financing activities	(1,000,000)	(47,000,000)
Net cash flows used in financing activities	(649,000,000)	261,000,000
Increase (decrease) in cash and cash equivalents	(295,000,000)	(1,125,000,000)
Cash and cash equivalents at beginning of period	1,016,000,000	1,612,000,000
Cash and cash equivalents at end of period	721,000,000	487,000,000
Exelon Generation Co L L C [Member]
Cash flows from operating activities
Net income	166,000,000	495,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	547,000,000	364,000,000
Deferred income taxes and amortization of investment tax credits	165,000,000	180,000,000
Net fair value changes related to derivatives	(63,000,000)	148,000,000
Net realized and unrealized (gains) losses on nuclear decommissioning trust fund investments	(103,000,000)	(40,000,000)
Other non-cash operating activities	(90,000,000)	(72,000,000)
Changes in assets and liabilities:
Accounts receivable	321,000,000	(151,000,000)
Receivables from and payables to affiliates, net	85,000,000	238,000,000
Inventories	59,000,000	26,000,000
Accounts payable, accrued expenses and other current liabilities	(782,000,000)	17,000,000
Option premiums paid, net	(100,000,000)	19,000,000
Counterparty collateral (posted) received, net	348,000,000	(206,000,000)
Income taxes	162,000,000	388,000,000
Pension and non-pension postretirement benefit contributions	(20,000,000)	(952,000,000)
Other assets and liabilities	(80,000,000)	(20,000,000)
Net cash flows provided by operating activities	795,000,000	578,000,000
Cash flows from investing activities
Capital expenditures	(1,055,000,000)	(772,000,000)
Proceeds from nuclear decommissioning trust fund sales	3,680,000,000	1,195,000,000
Investment in nuclear decommissioning trust funds	(3,726,000,000)	(1,247,000,000)
Change in restricted cash	(1,000,000)	0
Cash acquired from Constellation	708,000,000	0
Other investing activities	(77,000,000)	1,000,000
Net cash flows provided by (used in) investing activities	(471,000,000)	(823,000,000)
Cash flows from financing activities
Changes in short-term debt	0	0
Issuance of long-term debt	0	0
Retirement of long-term debt	(1,000,000)	(1,000,000)
Distribution to member	(600,000,000)	0
Contributions from member	0	0
Other financing activities	0	(37,000,000)
Net cash flows used in financing activities	(601,000,000)	(38,000,000)
Increase (decrease) in cash and cash equivalents	(277,000,000)	(283,000,000)
Cash and cash equivalents at beginning of period	496,000,000	456,000,000
Cash and cash equivalents at end of period	219,000,000	173,000,000
Commonwealth Edison Co [Member]
Cash flows from operating activities
Net income	87,000,000	69,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	149,000,000	134,000,000
Deferred income taxes and amortization of investment tax credits	57,000,000	81,000,000
Other non-cash operating activities	(60,000,000)	(82,000,000)
Changes in assets and liabilities:
Accounts receivable	58,000,000	21,000,000
Receivables from and payables to affiliates, net	15,000,000	(22,000,000)
Inventories	(3,000,000)	(4,000,000)
Accounts payable, accrued expenses and other current liabilities	(159,000,000)	(153,000,000)
Counterparty collateral (posted) received, net	(8,000,000)	56,000,000
Income taxes	116,000,000	288,000,000
Pension and non-pension postretirement benefit contributions	(9,000,000)	(871,000,000)
Other assets and liabilities	(72,000,000)	(35,000,000)
Net cash flows provided by operating activities	291,000,000	(354,000,000)
Cash flows from investing activities
Capital expenditures	(291,000,000)	(251,000,000)
Proceeds from sales of investments	(10,000,000)	(1,000,000)
Purchases of investments	(5,000,000)	(1,000,000)
Change in restricted cash	0	0
Other investing activities	6,000,000	10,000,000
Net cash flows provided by (used in) investing activities	(280,000,000)	(241,000,000)
Cash flows from financing activities
Changes in short-term debt	302,000,000	50,000,000
Issuance of long-term debt	0	599,000,000
Retirement of long-term debt	(450,000,000)	0
Contributions from parent	0	0
Dividends paid on common stock	(75,000,000)	(75,000,000)
Other financing activities	(3,000,000)	(2,000,000)
Net cash flows used in financing activities	(226,000,000)	572,000,000
Increase (decrease) in cash and cash equivalents	(215,000,000)	(23,000,000)
Cash and cash equivalents at beginning of period	234,000,000	50,000,000
Cash and cash equivalents at end of period	19,000,000	27,000,000
PECO Energy Co [Member]
Cash flows from operating activities
Net income	97,000,000	126,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	53,000,000	48,000,000
Deferred income taxes and amortization of investment tax credits	10,000,000	56,000,000
Other non-cash operating activities	(40,000,000)	(35,000,000)
Changes in assets and liabilities:
Accounts receivable	31,000,000	188,000,000
Receivables from and payables to affiliates, net	12,000,000	(227,000,000)
Inventories	39,000,000	55,000,000
Accounts payable, accrued expenses and other current liabilities	(71,000,000)	(26,000,000)
Income taxes	76,000,000	33,000,000
Pension and non-pension postretirement benefit contributions	(5,000,000)	(110,000,000)
Other assets and liabilities	(110,000,000)	(162,000,000)
Net cash flows provided by operating activities	172,000,000	16,000,000
Cash flows from investing activities
Capital expenditures	(96,000,000)	(121,000,000)
Changes in Exelon intercompany money pool	(35,000,000)	(59,000,000)
Change in restricted cash	(3,000,000)	(2,000,000)
Other investing activities	4,000,000	10,000,000
Net cash flows provided by (used in) investing activities	(130,000,000)	(172,000,000)
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	(87,000,000)	(111,000,000)
Dividends paid on preferred securities	(1,000,000)	(1,000,000)
Repayment of receivable from parent	0	0
Other financing activities	0	(5,000,000)
Net cash flows used in financing activities	(88,000,000)	(117,000,000)
Increase (decrease) in cash and cash equivalents	(46,000,000)	(273,000,000)
Cash and cash equivalents at beginning of period	194,000,000	522,000,000
Cash and cash equivalents at end of period	148,000,000	249,000,000
Baltimore Gas and Electric Company [Member]
Cash flows from operating activities
Net income	(30,000,000)	81,000,000
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation, amortization and accretion	79,000,000	77,000,000
Deferred income taxes and amortization of investment tax credits	40,000,000	29,000,000
Other non-cash operating activities	(178,000,000)	(16,000,000)
Changes in assets and liabilities:
Accounts receivable	(9,000,000)	27,000,000
Receivables from and payables to affiliates, net	56,000,000	(1,000,000)
Inventories	50,000,000	41,000,000
Accounts payable, accrued expenses and other current liabilities	(60,000,000)	3,000,000
Income taxes	(57,000,000)	56,000,000
Pension and non-pension postretirement benefit contributions	(7,000,000)	(5,000,000)
Other assets and liabilities	12,000,000	26,000,000
Net cash flows provided by operating activities	252,000,000	350,000,000
Cash flows from investing activities
Capital expenditures	(115,000,000)	(136,000,000)
Change in restricted cash	(19,000,000)	(23,000,000)
Other investing activities	(6,000,000)	0
Net cash flows provided by (used in) investing activities	(140,000,000)	(159,000,000)
Cash flows from financing activities
Dividends paid on common stock		(85,000,000)
Dividends paid on preferred securities	(3,000,000)	(3,000,000)
Other financing activities	(1,000,000)	(3,000,000)
Net cash flows used in financing activities	(4,000,000)	(91,000,000)
Increase (decrease) in cash and cash equivalents	108,000,000	100,000,000
Cash and cash equivalents at beginning of period	49,000,000	50,000,000
Cash and cash equivalents at end of period	$ 157,000,000	$ 150,000,000