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		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Effect of Cash Flow Hedges on Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance, pre-tax	$ (11)	$ (147)	$ (47)	$ (101)
Additions and revaluations of derivatives designated as cash flow hedges, pre-tax	(3)	10	6	(62)
Clearance of hedge results to earnings, pre-tax	25	18	52	44
Ending balance, pre-tax	11	(119)	11	(119)
Beginning balance, tax	2	52	16	36
Additions and revaluations of derivatives designated as cash flow hedges, tax	2	(3)	(1)	23
Clearance of hedge results to earnings, tax	(9)	(7)	(20)	(17)
Ending balance, tax	(5)	42	(5)	42
Beginning balance, after-tax	(9)	(95)	(31)	(65)
Additions and revaluations of derivatives designated as cash flow hedges, after-tax	(1)	7	5	(39)
Clearance of hedge results to earnings, after-tax	16	11	32	27
Ending balance, after-tax	$ 6	$ (77)	$ 6	$ (77)