Consolidated Statements Of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Comprehensive Income [Line Items]
Net income	$ 582	$ 863	$ 761
Reclassification adjustments included in net income
Change in cash flow hedges, net of tax	8	6	6
Change in unrecognized items for pension and other postretirement benefits, net of tax	5	3	4
Net unrealized (losses) gains on cash flow hedges, net of tax	(87)	(34)	16
Net unrecognized items on pension and other postretirement benefits, net of tax	34	(13)	2
Other, net of tax			1
Other comprehensive (loss) income	(40)	(38)	29
Comprehensive income	542	825	790
Comprehensive (income) loss attributable to noncontrolling interests	(7)	(7)	(4)
Comprehensive income attributable to controlling interests	535	818	786
Tax information [Details]
Change in cash flow hedges, tax benefit (expense)	(5)	(4)	(4)
Change in unrecognized items for pension and other postretirement benefits, tax benefit (expense)	(3)	(2)	(3)
Net unrealized gains (losses) on cash flow hedges, tax (expense) benefit	56	22	(10)
Net unrecognized items on pension and other postretirement benefits, tax benefit (expense)	(24)	8	(1)
PEC
Comprehensive Income [Line Items]
Net income	516	602	514
Reclassification adjustments included in net income
Change in cash flow hedges, net of tax	5	4	3
Net unrealized (losses) gains on cash flow hedges, net of tax	(43)	(10)	5
Other comprehensive (loss) income	(38)	(6)	8
Comprehensive income	478	596	522
Comprehensive (income) loss attributable to noncontrolling interests		1	2
Comprehensive income attributable to controlling interests	478	597	524
Tax information [Details]
Change in cash flow hedges, tax benefit (expense)	(3)	(3)	(2)
Net unrealized gains (losses) on cash flow hedges, tax (expense) benefit	28	6	(3)
PEF
Comprehensive Income [Line Items]
Net income	314	453	462
Reclassification adjustments included in net income
Net unrealized (losses) gains on cash flow hedges, net of tax	(23)	(7)	4
Other comprehensive (loss) income	(23)	(7)	4
Comprehensive income attributable to controlling interests	291	446	466
Tax information [Details]
Net unrealized gains (losses) on cash flow hedges, tax (expense) benefit	$ 15	$ 4	$ (2)