Financial Instruments (Details) - Fair Value, Measurements, Recurring - Not Designated as Hedging Instrument - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	$ 15		$ 31
Liability Derivatives	13		27
Interest Rate Cap | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	11		25
Liability Derivatives	11		25
Foreign Exchange Forward
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency forward contracts	(1)	$ (5)
Foreign Exchange Forward | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Asset Derivatives	4		6
Liability Derivatives	$ 2		$ 2