Accumulated Other Comprehensive Income (Loss) - Summary of Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Unrealized gains (losses) on cash flow hedging instruments:
Balance at beginning of period		$ 0	$ (32)	$ (15)	$ (52)
Net gains arising during period, net of tax		0	6	11	22
Reclassification adjustment for losses realized in net income, net of tax	[1]	0	2	4	6
Total other comprehensive income for period		0	8	15	28
Balance at end of period		0	(24)	0	(24)
Net gains arising during period, taxes		0	2	6	11
Reclassification adjustment for losses realized in net income, taxes		0	1	3	3
Pension and postretirement benefit plan liability:
Balance at beginning of period		26	(13)	29	(13)
Reclassification adjustment for losses realized in net income, net of tax				(3)	0
Pension and postretirement benefit plan adjustments		0	0	(3)	0
Balance at end of period		26	(13)	26	(13)
Reclassification adjustment for losses realized in net income, tax		0	0	(1)	0
Total accumulated other comprehensive income (loss) at end of period		$ 26	$ (37)	$ 26	$ (37)	$ 14

[1] The amounts reclassified relate to currency swaps and are included as a component of interest expense in our consolidated statement of income.