Discontinued Operations (Details 1) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Pre Tax Gains And Losses For Energy Commodity Derivatives Designated As Cash Flow Hedges [Abstract]
Net gain (loss) recognized in other comprehensive income (loss) (effective portion)	$ 30	$ (18)
Net gain (loss) reclassified from accumulated other comprehensive income (loss) into income (effective portion)	30	(18)
Segment, Discontinued Operations [Member]
Pre Tax Gains And Losses For Energy Commodity Derivatives Designated As Cash Flow Hedges [Abstract]
Net gain (loss) recognized in other comprehensive income (loss) (effective portion)		413
Net gain (loss) reclassified from accumulated other comprehensive income (loss) into income (effective portion)		332
Derivative Instruments Not Designated As Hedging Instruments Gain Loss Net Abstract
Gain (loss) recognized in income		$ 30