Accumulated Other Comprehensive Income (Loss) - Summary of Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Unrealized gains (losses) on cash flow hedging instruments:
Balance at beginning of period		$ (15)	$ (52)
Net gains arising during period, net of tax		7	9
Reclassification adjustment for losses realized in net income, net of tax	[1]	1	2
Total other comprehensive income for period		8	11
Balance at end of period		(7)	(41)
Net gains arising during period, taxes		4	5
Reclassification adjustment for losses realized in net income, taxes		2	1
Pension and postretirement benefit plan liability:
Balance at beginning of period		29	(13)
Reclassification adjustment for losses realized in net income, net of tax		(1)	0
Pension and postretirement benefit plan adjustments		(1)	0
Balance at end of period		28	(13)
Reclassification adjustment for losses realized in net income, tax		(1)	0
Total accumulated other comprehensive gain (loss) at end of period		$ 21	$ (54)	$ 14

[1] The amounts reclassified during the three months ended March 31, 2016 and 2015 relate to interest rate and currency swaps and are included as a component of interest expense in our consolidated statement of income.