Derivatives and Other Hedging Instruments (Summary of Effect of Cash Flows Hedges on Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Effect of Cash Flow Hedges on Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance, pre-tax	$ 11	$ (119)	$ (47)	$ (101)
Additions and revaluations of derivatives designated as cash flow hedges, pre-tax	13	(18)	19	(80)
Clearance of hedge results to earnings, pre-tax	25	20	77	64
Ending balance, pre-tax	49	(117)	49	(117)
Beginning balance, tax	(5)	42	16	36
Additions and revaluations of derivatives designated as cash flow hedges, tax	(5)	6	(6)	29
Clearance of hedge results to earnings, tax	(9)	(7)	(29)	(24)
Ending balance, tax	(19)	41	(19)	41
Beginning balance, after-tax	6	(77)	(31)	(65)
Additions and revaluations of derivatives designated as cash flow hedges, after-tax	8	(12)	13	(51)
Clearance of hedge results to earnings, after-tax	16	13	48	40
Ending balance, after-tax	$ 30	$ (76)	$ 30	$ (76)