Stock-Based Compensation (Stock Based Compensation Activity) (Detail) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 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	$ 56
Number of Options, Balance	836		848
Options outstanding, intrinsic value	47		54
Stock Issued During Period, Value, Restricted Stock Award, Gross	23	14
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	4 years 0 months 0 days		4 years 3 months 0 days
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	$ 61.17	$ 41.15
Weighted Average Grant Price, Vested/exercised	$ 22.19
Weighted Average Grant Price, Canceled	$ 43.57
Weighted Average Grant Price, Balance	$ 42.70
Number of RSUs, Balance	998
Number of RSUs, Granted at fair market value	250
Number of RSUs, Vested/exercised	(528)
Number of RSUs, Canceled	(9)
Number of RSUs, Balance	711
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	$ 39.37
Weighted Average Grant Price, Vested/exercised	$ 12.07
Weighted Average Grant Price, Canceled	$ 18.18
Weighted Average Grant Price, Balance	$ 34.92
Number of RSUs, Balance	1,884
Number of RSUs, Granted at fair market value	230
Number of RSUs, Vested/exercised	(976)
Number of RSUs, Canceled	(159)
Number of RSUs, Balance	979
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding	58
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	1 year 5 months 0 days
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
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
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding	7
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	42
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 46