Derivative Instruments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Maximum length of time hedged in interest rate cash flow hedges	through June 2031
Maximum Length of Time Hedged in Foreign Currency Cash Flow Hedge	16 years 6 months
Margin cash collateral received from counterparties that was not offset against derivative assets	$ 45	$ 24
Margin cash collateral provided to counterparties that was not offset against derivative liabilities	109	42
Total gain (loss) to be reclassified during next 12 months	$ (61)