Derivative Instruments (Details) (USD $)	12 Months Ended
	Dec. 31, 2012
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months	$ (44,000,000)
Summary of derivative instruments by risk exposure, maximum maturity [Abstract]
Maximum length of time hedged in interest rate cash flow hedges	December 2030
Maximum length of time hedged in foreign currency cash flow hedges	September 2030
Net notional amount of interest rate swaps	7,300,000,000
Net notional amount of foreign currency swaps	$ 662,000,000