Accumulated Other Comprehensive Income - Components of Accumulated Other Comprehensive Income (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), tax	$ 20	$ 4	$ 9
Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), tax	20	4	9
Amounts reclassified from accumulated other comprehensive income, tax	(14)	(3)	(1)
Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), tax	(1)	2	1
Amounts reclassified from accumulated other comprehensive income, tax	0	0	0
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), tax	0	0	0
Amounts reclassified from accumulated other comprehensive income, tax	0	0	0
Post - Retirement Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), tax	1	(8)	10
Amounts reclassified from accumulated other comprehensive income, tax	$ 0	$ 0	$ 0