Fair Value Measurements - Derivatives in Cash Flow Hedging Relationships (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Interest Expense
Derivative Instruments Gain Loss [Line Items]
Amount of Loss Reclassified from AOCI into Income (Effective Portion)	$ 4	$ 4	$ 12	$ 12
Interest Rate Swap
Derivative Instruments Gain Loss [Line Items]
Amount of (Gain)/Loss Recognized in OCI Derivatives (Effective Portion)	$ (3)	$ 7	$ 6	$ 2