Accumulated Other Comprehensive Income (Loss) - Reclassification of Component of Accumulated Other Comprehensive Income (Loss) Associated with Cash Flow Hedges (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense, net	$ (94)	$ (95)	$ (282)	$ (294)
Other, net		(1)	(49)	(2)
Income (loss) before income taxes	457	496	1,312	663
Tax (expense) benefit	(153)	(159)	(466)	(184)
Total reclassifications for the period, Net of tax	304	337	846	479
Amount Reclassified from Accumulated Other Comprehensive Income [Member] | Derivative Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income (loss) before income taxes	(3)	15	(29)	28
Tax (expense) benefit	1	(6)	11	(11)
Total reclassifications for the period, Net of tax	(2)	9	(18)	17
Interest Rate Swaps [Member] | Amount Reclassified from Accumulated Other Comprehensive Income [Member] | Derivative Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense, net	(2)	(4)	(8)	(9)
Treasury Rate Locks [Member] | Amount Reclassified from Accumulated Other Comprehensive Income [Member] | Derivative Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense, net	$ (1)		(1)	(3)
Foreign Currency Derivatives [Member] | Amount Reclassified from Accumulated Other Comprehensive Income [Member] | Derivative Instruments [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other, net		$ 19	$ (20)	$ 40