Fair Value of Financial Assets and Liabilities (Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings) (Details) (Fair Value Inputs Level 3 [Member], USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Operating Revenue [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Total gains (losses) included in income	$ (268,000,000)	$ (159,000,000)
Change in the unrealized gains (losses) relating to assets and liabilities held	(425,000,000)	(117,000,000)
Purchased Fuel and Electric [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Total gains (losses) included in income	(44,000,000)	32,000,000
Change in the unrealized gains (losses) relating to assets and liabilities held	(21,000,000)	38,000,000
Other, net [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Total gains (losses) included in income	1,000,000	1,000,000
Change in the unrealized gains (losses) relating to assets and liabilities held		1,000,000
Exelon Generation Co L L C [Member] | Operating Revenue [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Total gains (losses) included in income	(268,000,000)	(176,000,000)
Change in the unrealized gains (losses) relating to assets and liabilities held	(425,000,000)	(124,000,000)
Exelon Generation Co L L C [Member] | Purchased Fuel and Electric [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Total gains (losses) included in income	(44,000,000)	32,000,000
Change in the unrealized gains (losses) relating to assets and liabilities held	(21,000,000)	38,000,000
Exelon Generation Co L L C [Member] | Other, net [Member]
Fair Value Assets And Liabilities Measured On Recurring Basis Gain Loss Included In Earnings [Line Items]
Total gains (losses) included in income	1,000,000	814,139.21
Change in the unrealized gains (losses) relating to assets and liabilities held		$ 1,065,685.19