Accumulated Other Comprehensive Loss - Changes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
AOCI roll forward
Beginning balance	$ 5,320	$ 5,367	$ 5,889
Other comprehensive income (loss), net of tax	88	47	(150)
Ending balance	6,042	5,320	5,367
Accumulated Other Comprehensive Loss [Member]
AOCI roll forward
Beginning balance	(80)	(127)	23
Other comprehensive income (loss) before reclassifications, net of tax	82	24	(134)
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax	6	23	(16)
Other comprehensive income (loss), net of tax	88	47	(150)
Ending balance	8	(80)	(127)
Derivative Instruments [Member]
AOCI roll forward
Beginning balance	(40)	(52)	(61)
Other comprehensive income (loss) before reclassifications, net of tax		(7)	30
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax	7	19	(21)
Other comprehensive income (loss), net of tax	7	12	9
Ending balance	(33)	(40)	(52)
Available-for-Sale Securities. [Member]
AOCI roll forward
Beginning balance	13	8	10
Other comprehensive income (loss) before reclassifications, net of tax	3	5	(2)
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax	(1)
Other comprehensive income (loss), net of tax	2	5	(2)
Ending balance	15	13	8
Foreign Currency Translation Adjustments [Member]
AOCI roll forward
Beginning balance	(47)	(75)	84
Other comprehensive income (loss) before reclassifications, net of tax	76	26	(164)
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax		2	5
Other comprehensive income (loss), net of tax	76	28	(159)
Ending balance	29	(47)	(75)
Post - Retirement Benefit Obligation [Member]
AOCI roll forward
Beginning balance	(6)	(8)	(10)
Other comprehensive income (loss) before reclassifications, net of tax	3		2
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax		2
Other comprehensive income (loss), net of tax	3	2	2
Ending balance	$ (3)	$ (6)	$ (8)