Reconciliation of Ongoing Earnings (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reconciliation Ongoing Earnings To Net Income Attributable To Controlling Interests [Abstract]
Ongoing Earnings									$ 871	$ 889	$ 846
CVO mark-to-market, net of tax (Note 16)		(50)							(45)	0	19
Impairment, net of tax									(2)	(6)	(2)
Merger and integration costs, net of tax (Note 2)									(46)
CR3 indemnification charge, net of tax (Note 22C)									(20)
Plant retirement charge, net of tax									(1)	(1)	(17)
Amount to be refunded to customers, net of tax									(177)
Change in tax treatment of the Medicare Part D subsidy (Note 17)									0	(22)
Cumulative prior period adjustment related to certain employee life insurance benefits, net of tax											(10)
Continuing income attributable to noncontrolling interests, net of tax									7	7	4
Income from continuing operations	(73)	293	180	187	130	365	181	191	587	867	840
Discontinued operations, net of tax									(5)	(4)	(79)
Net income attributable to noncontrolling interests, net of tax									(7)	(7)	(4)
Net income attributable to controlling interests	(76)	291	176	184	125	361	180	190	575	856	757
Tax information [Details]
CVO mark-to-market, tax benefit (expense)									14
Impairment, tax benefit (expense)									1	4	1
Merger and integration costs, tax benefit (expense)									17
CR3 indemnification charge, tax benefit (expense)									13
Plant retirement charge, tax benefit (expense)									1	1	11
Amount to be refunded to customers, tax benefit (expense)									111
Cumulative prior period adjustment related to certain employee life insurance benefits, tax benefit (expense)									$ 0	$ 0	$ 7