Accumulated Other Comprehensive Income - Other Comprehensive Income (Loss) Before Reclassifications Associated With the Effective Portion of Derivatives Designated as Cash Flow Hedges (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) on derivatives before tax	$ 50	$ 10	$ 23
Tax (expense) benefit	(20)	(4)	(9)
Net of tax	30	6	14
Interest Rate Swaps [Member] | Cash Flow Hedging [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) on derivatives before tax		(8)	14
Foreign Currency Derivatives [Member] | Cash Flow Hedging [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) on derivatives before tax	$ 50	23	17
Electricity Commodity Derivatives [Member] | Cash Flow Hedging [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) on derivatives before tax		$ (5)	$ (8)