Quarterly Data (Details) (USD $) In Millions, except Per Share data	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Earnings Per Share Basic [Abstract]
Average common shares outstanding - basic	663	661	663	661
Earnings Per Share, Basic	$ 0.93	$ 0.67	$ 1.94	$ 1.81
Earnings Per Share Diluted
Average common shares outstanding - diluted	664	662	664	662
Earnings Per Share, Diluted	$ 0.93	$ 0.67	$ 1.94	$ 1.80
Selected Quarterly Financial Information [Line Items]
Revenues	$ 4,587	$ 4,398	$ 9,638	$ 8,859
Operating Income (Loss)	1,034	1,018	2,236	2,421
Net Income Loss	620	445	1,288	1,194
Exelon Generation Co L L C [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	2,546	2,353	5,285	4,773
Operating Income (Loss)	647	587	1,448	1,503
Net Income Loss	443	382	938	943
Commonwealth Edison Co [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	1,444	1,499	2,910	2,914
Operating Income (Loss)	254	256	454	547
Net Income Loss	114	9	183	125
PECO Energy Co [Member]
Selected Quarterly Financial Information [Line Items]
Revenues	842	1,269	1,996	2,724
Operating Income (Loss)	161	182	372	375
Net Income Loss	$ 83	$ 75	$ 210	$ 176

Selected Quarterly Financial Information [Line Items]

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The amount of net income or loss for the period per each share of common stock outstanding during the reporting period.

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The amount of net income or loss for the period per each share of common stock and dilutive common stock equivalents outstanding during the reporting period.

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The portion of consolidated profit or loss for the period, net of income taxes, which is attributable to the parent. If the entity does not present consolidated financial statements, the amount of profit or loss for the period, net of income taxes.

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Aggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains.

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The average number of shares issued and outstanding that are used in calculating diluted EPS, determined based on the timing of issuance of shares in the period.

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Number of [basic] shares, after adjustment for contingently issuable shares and other shares not deemed outstanding, determined by relating the portion of time within a reporting period that common shares have been outstanding to the total time in that period.

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