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, 2014		Mar. 31, 2013	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Adjustments to Additional Paid in Capital, Income Tax Benefit from Share-based Compensation			$ 57
Number of Options, Balance	892	[1]		979
Options outstanding, intrinsic value	41	[1]		37
Stock Issued During Period, Value, Restricted Stock Award, Gross	14		14
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	5 years 0 months 0 days	[1]		5 years 2 months 0 days
Time-Based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Grant Price, Balance	$ 17.92	[2]
Weighted Average Grant Price, Granted at fair market value	$ 41.15		$ 21.20
Weighted Average Grant Price, Vested/exercised	$ 16.62	[3]
Weighted Average Grant Price, Canceled	$ 23.49
Weighted Average Grant Price, Balance	$ 26.40	[4]
Number of RSUs, Balance	1,308	[2]
Number of RSUs, Granted at fair market value	352
Number of RSUs, Vested/exercised	(588)	[3]
Number of RSUs, Canceled	(56)
Number of RSUs, Balance	1,016	[4]
Performance-Based and Market-Based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Grant Price, Balance	$ 13.79	[2]
Weighted Average Grant Price, Granted at fair market value	$ 39.37		$ 20.30
Weighted Average Grant Price, Vested/exercised	$ 10.91	[3]
Weighted Average Grant Price, Canceled	$ 21.48
Weighted Average Grant Price, Balance	$ 17.66	[4]
Number of RSUs, Balance	2,043	[2]
Number of RSUs, Granted at fair market value	235
Number of RSUs, Vested/exercised	(432)	[3]
Number of RSUs, Canceled	(32)
Number of RSUs, Balance	1,814	[4]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding	88
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	1 year 3 months 0 days
Cash Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Grant Price, Balance	$ 14.90	[2]
Weighted Average Grant Price, Granted at fair market value	$ 0.00		$ 17.14
Weighted Average Grant Price, Vested/exercised	$ 0.00	[3]
Weighted Average Grant Price, Canceled	$ 0.00
Weighted Average Grant Price, Balance	$ 14.90	[4]
Number of RSUs, Balance	267	[2]
Number of RSUs, Granted at fair market value	0
Number of RSUs, Vested/exercised	0	[3]
Number of RSUs, Canceled	0
Number of RSUs, Balance	267	[4]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Outstanding	13
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	49
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 43

[1] The Company assumes that substantially all outstanding stock options will vest over time.

[2] Reflects the maximum number of stock units assuming achievement of all performance-, market- and time-vesting criteria and does not include those for non-employee directors. The weighted-average fair value of time-based RSUs, performance-based and market-based RSUs, and cash units granted in 2013 was $21.20, $20.30 and $17.14, respectively.

[3] The total grant date fair value of RSUs vested during the three months ended March 31, 2014 and 2013 was $14 million and $14 million, respectively.

[4] The Company’s outstanding time-based RSUs, performance-based and market-based RSUs, and cash units had aggregate intrinsic value of $49 million, $88 million and $13 million, respectively. Aggregate unrecognized compensation expense related to time-based RSUs and performance-based and market-based RSUs amounted to $43 million and will be recognized over a weighted average vesting period of 1.3 years. The Company assumes that substantially all outstanding awards will vest over time.