Derivative Instruments and Hedging Activities - Cash Flow Hedges Included in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated Other Comprehensive Loss After-tax	$ 8	$ 9
Portion Expected to be Reclassified to Income during the Next 12 Months	1	1
Interest Rate [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated Other Comprehensive Loss After-tax	8	9
Portion Expected to be Reclassified to Income during the Next 12 Months	$ 1	$ 1
Maximum Term	203 months	215 months