Reconciliation of Ongoing Earnings (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Reconciliation Ongoing Earnings To Net Income Attributable To Controlling Interests [Abstract]
Ongoing Earnings	$ 344	$ 361	$ 757	$ 756
Tax levelization	8	4	2	3
CVO mark-to-market, net of tax (Note 10)	(50)		(46)
Impairment, net of tax	0	(2)	0	(5)
Plant retirement adjustment, net of tax	0	0	0	1
Change in tax treatment of the Medicare Part D subsidy (Note 11)	0	0	0	(22)
Merger and integration costs, net of tax (Note 2)	(15)	0	(36)	0
CR3 indemnification adjustment (charge), net of tax (Note 15B)	4		(22)
Continuing income attributable to noncontrolling interests, net of tax	2	2	5	4
Income from continuing operations before cumulative effect of change in accounting principle	293	365	660	737
Discontinued operations, net of tax	0	(2)	(4)	(2)
Cumulative effect of change in accounting principle, net of tax	0	2	0	0
Net (income) loss attributable to noncontrolling interests, net of tax	(2)	(4)	(5)	(4)
Net income attributable to controlling interests	291	361	651	731
Tax information [Details]
CVO mark-to-market, tax benefit (expense)	13		13
Impairment, tax benefit (expense)	0	1	0	3
Plant retirement adjustment, tax benefit (expense)	0	0	0	(1)
Merger and integration costs, tax benefit (expense)	7		11
CR3 indemnification adjustment (charge), tax benefit (expense)	$ (2)		$ 16