Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning balance			$ 5,320
Other comprehensive income, net of tax expense	$ 33	$ 9	47	$ 78
Accumulated Other Comprehensive Income (Loss), Ending balance	5,507		5,507
Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning balance			(40)
Amounts reclassified from accumulated other comprehensive loss net of tax			4
Other comprehensive income, net of tax expense			4
Accumulated Other Comprehensive Income (Loss), Ending balance	(36)		(36)
Accumulated Net Investment Gain (Loss) Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning balance			13
Other comprehensive income before reclassifications, net of tax			2
Other comprehensive income, net of tax expense			2
Accumulated Other Comprehensive Income (Loss), Ending balance	15		15
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning balance			(47)
Other comprehensive income before reclassifications, net of tax			40
Other comprehensive income, net of tax expense			40
Accumulated Other Comprehensive Income (Loss), Ending balance	(7)		(7)
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning balance			(6)
Other comprehensive income before reclassifications, net of tax			1
Other comprehensive income, net of tax expense			1
Accumulated Other Comprehensive Income (Loss), Ending balance	(5)		(5)
AOCI Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning balance			(80)
Other comprehensive income before reclassifications, net of tax			43
Amounts reclassified from accumulated other comprehensive loss net of tax			4
Other comprehensive income, net of tax expense			47
Accumulated Other Comprehensive Income (Loss), Ending balance	$ (33)		$ (33)