Derivatives and Other Hedging Instruments (Effect of Cash Flow Hedges on Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Beginning balance, pre-tax	$ (47)	$ (101)
Additions and revaluations of derivatives designated as cash flow hedges, pre-tax	17	(36)
Clearance of hedge results to earnings, pre-tax	96	90
Ending balance, pre-tax	66	(47)
Beginning balance, tax	16	36
Additions and revaluations of derivatives designated as cash flow hedges, tax	(5)	14
Clearance of hedge results to earnings, tax	(36)	(34)
Ending balance, tax	(25)	16
Beginning balance, after-tax	(31)	(65)
Additions and revaluations of derivatives designated as cash flow hedges, after-tax	12	(22)
Clearance of hedge results to earnings, after-tax	60	56
Ending balance, after-tax	41	(31)
Portion of ending balance expected to be reclassified into earnings over the next twelve months, pre-tax	73
Portion of ending balance expected to be reclassified into earnings over the next twelve months, tax	(28)
Portion of ending balance expected to be reclassified into earnings over the next twelve months, after-tax	$ 45