Reconciliation of Ongoing Earnings (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Reconciliation Ongoing Earnings To Net Income Attributable To Controlling Interests
Ongoing Earnings	$ 211	$ 181	$ 413	$ 395
Tax levelization	(4)	0	(6)	(2)
CVO mark-to-market (Note 10D)	4		4
Impairment, net of tax	0	(1)	0	(2)
Plant retirement adjustment, net of tax	0	1	0	1
Change in tax treatment of the Medicare Part D subsidy (Note 9)	0	0	0	(22)
Merger and integration costs, net of tax (Note 2)	(7)	0	(21)	0
CR3 indemnification charge, net of tax (Note 13B)	(26)		(26)
Continuing income attributable to noncontrolling interests, net of tax	2	0	3	2
Income from continuing operations before cumulative effect of change in accounting principle	180	181	367	372
Discontinued operations, net of tax	(2)	(1)	(4)	0
Cumulative effect of change in accounting principle, net of tax	0	0	0	(2)
Net (income) loss attributable to noncontrolling interests, net of tax	(2)	0	(3)	0
Net income attributable to controlling interests	176	180	360	370
Tax information [Details]
Impairment, tax benefit (expense)	0	1	0	1
Plant retirement adjustment, tax benefit (expense)	0	0	0	(1)
Merger and integration costs, tax benefit (expense)	4		4
CR3 indemnification charge, tax benefit (expense)	$ 18		$ 18