Financial Instruments - Effect of Interest Rate Swaps on Results of Operations (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense	$ 425	$ 427	$ 844	$ 887
Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Loss Recognized in OCI on Derivatives, Net of Tax			19
Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense			$ 62