Stockholders' Equity (Narrative) (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Stockholders Equity [Line Items]
Other Comprehensive Income Unrealized Gain Loss On Cash Flow Hedges Arising During Period Net Of Tax			$ (8)	$ (3)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	$ 2	$ 2		6
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	1	$ 1	4	4
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax			(4)	$ 1
Stock Repurchase Program, Authorized Amount	885		$ 885
Stock Repurchased During Period, Shares			5.9	4.0
Stock Repurchased During Period, Value			$ 277	$ 210
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 258		258
Corporate Interest Expense [Member]
Stockholders Equity [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax			5
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax			3
Interest Expense [Member]
Stockholders Equity [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax			1
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax			$ 1