Stock-Based Compensation (Stock Based Compensation Activity) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation	$ 49
Number of Options, Balance	827		848
Options outstanding, intrinsic value	$ 34		$ 54
Stock Issued During Period, Value, Restricted Stock Award, Gross	$ 24	$ 15
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	3 years 6 months		4 years 3 months
Time-Based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Grant Price, Balance	$ 27.26
Weighted Average Grant Price, Granted at fair market value	54.72	$ 42.05
Weighted Average Grant Price, Vested/exercised	22.23
Weighted Average Grant Price, Canceled	41.19
Weighted Average Grant Price, Balance	$ 43.57		$ 27.26
Number of RSUs, Balance	998
Number of RSUs, Granted at fair market value	425
Number of RSUs, Vested/exercised	(538)
Number of RSUs, Canceled	(29)
Number of RSUs, Balance	856		998
Performance-Based and Market-Based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Grant Price, Balance	$ 19.17
Weighted Average Grant Price, Granted at fair market value	55.51	$ 42.03
Weighted Average Grant Price, Vested/exercised	12.05
Weighted Average Grant Price, Canceled	19.96
Weighted Average Grant Price, Balance	$ 35.15		$ 19.17
Number of RSUs, Balance	1,884
Number of RSUs, Granted at fair market value	230
Number of RSUs, Vested/exercised	(982)
Number of RSUs, Canceled	(182)
Number of RSUs, Balance	950		1,884
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding	$ 41
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	1 year
Cash Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Grant Price, Balance	$ 14.90
Weighted Average Grant Price, Granted at fair market value	0.00
Weighted Average Grant Price, Vested/exercised	12.65
Weighted Average Grant Price, Canceled	0.00
Weighted Average Grant Price, Balance	$ 18.04		$ 14.90
Number of RSUs, Balance	267
Number of RSUs, Granted at fair market value	0
Number of RSUs, Vested/exercised	(156)
Number of RSUs, Canceled	0
Number of RSUs, Balance	111		267
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding	$ 5
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding	37
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 31