Stockholders' Equity - Changes in Stockholders' Equity (Details) (USD $)	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013	Sep. 30, 2012
Changes in Stockholders' Equity
Beginning Balance					$ 19,004,000,000	$ 18,285,000,000
Net Income After Dividends on Preferred and Preference Stock	852,000,000	[1],[2]	976,000,000	[1]	1,230,000,000	1,967,000,000	[1]
Other comprehensive income (loss)	2,000,000		0		11,000,000	(1,000,000)
Stock Issued During Period, Value, Treasury Stock Reissued					89,000,000
Stock issued					533,000,000	479,000,000
Stock Repurchased During Period, Shares					0
Stock Repurchased During Period, Value					(19,000,000)	(117,000,000)
Cash dividends on common stock					(1,314,000,000)	(1,267,000,000)
Other					0	0
Ending Balance	19,534,000,000		19,346,000,000		19,534,000,000	19,346,000,000
Number of Common shares Issued [Member]
Changes in Stockholders' Equity
Beginning Balance, Shares					877,803,000	865,664,000
Stock issued, shares					12,046,000	11,586,000
Stock Repurchased During Period, Shares					0	0
Ending Balance, Shares	889,849,000		877,250,000		889,849,000	877,250,000
Number of Common shares Treasury [Member]
Changes in Stockholders' Equity
Beginning Balance, Shares					(10,035,000)	(539,000)
Stock Issued During Period, Shares, Treasury Stock Reissued					1,956,000
Stock Repurchased During Period, Shares					0	(2,567,000)
Other, Shares					(30,000)	(38,000)
Ending Balance, Shares	8,109,000		(3,144,000)		8,109,000	(3,144,000)
Common Stockholders' Equity [Member]
Changes in Stockholders' Equity
Beginning Balance					18,297,000,000	17,578,000,000
Net Income After Dividends on Preferred and Preference Stock					1,230,000,000	1,967,000,000
Other comprehensive income (loss)					11,000,000	(1,000,000)
Stock Issued During Period, Value, Treasury Stock Reissued					89,000,000
Stock issued					484,000,000	479,000,000
Stock Repurchased During Period, Value					(19,000,000)	(117,000,000)
Cash dividends on common stock					(1,314,000,000)	(1,267,000,000)
Other					0	0
Ending Balance	18,778,000,000		18,639,000,000		18,778,000,000	18,639,000,000
Preferred and Preference Stock of Subsidiaries [Member]
Changes in Stockholders' Equity
Beginning Balance					707,000,000	707,000,000
Net Income After Dividends on Preferred and Preference Stock					0	0
Other comprehensive income (loss)					0	0
Stock issued					49,000,000	0
Stock Repurchased During Period, Value					0	0
Cash dividends on common stock					0
Other					0	0
Ending Balance	$ 756,000,000		$ 707,000,000		$ 756,000,000	$ 707,000,000

[1] After dividends on preferred and preference stock of subsidiaries.

[2] Segment net income (loss) for the three months ended September 30, 2013 includes a $150 million pre-tax charge ($93 million after tax) for an estimated probable loss on the Kemper IGCC. See Note (B) under "Integrated Coal Gasification Combined Cycle – Kemper IGCC Cost Estimate" herein for additional information.