Accumulated Other Comprehensive Income - Other Comprehensive Income (Loss) Before Reclassifications Associated With Cash Flow Derivative Instruments (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) on derivatives before tax	$ (8)	$ (1)
Tax (expense) benefit	3
Net of tax	(5)	(1)
Interest Rate Swaps [Member] | Cash Flow Hedging [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) on derivatives before tax	(8)	2
Foreign currency derivatives[Member] | Cash Flow Hedging [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) on derivatives before tax	10	7
Electricity commodity derivatives [Member] | Cash Flow Hedging [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) on derivatives before tax	$ (10)	$ (10)