Stock Options Status and Activity (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended				12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Stock Options [Line Items]
Increase Decrease In Earnings Per Share Diluted						$ (0.09)	$ (0.08)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Shares Under Option Outstanding Beginning Balance	2,073,185	2,086,770	2,119,003	1,983,573	1,983,573
Shares Under Option, Granted	0	834	0	192,624
Share Under Option, Canceled	0	(526)		(31,299)
Shares Under Option, Forfeited	(12,182)	(1,535)	0	(300)
Shares Under Option, Exercised	(607,000)	(12,358)	(32,233)	(25,595)
Shares Under Option Outstanding Ending Balance	1,454,003	2,073,185	2,086,770	2,119,003	1,454,003	1,983,573
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Prices, Outstanding, Beginning Balance	$ 26.13	$ 26.11	$ 26.10	$ 22.93	$ 22.93
Weighted Average Exercise Prices, Granted	$ 0	$ 66.54	$ 0.00	$ 56.23
Weighted Average Exercise Price, Canceled	$ 0.00	$ 36.00		$ 19.78
Weighted Average Exercise Prices, Forfeited	$ 47.36	$ 29.72	$ 0.00	$ 22.77
Weighted Average Exercise Prices, Exercised	$ 13.66	$ 23.81	$ 25.49	$ 14.72
Weighted Average Exercise Prices, Outstanding, Ending Balance	$ 31.16	$ 26.13	$ 26.11	$ 26.10	$ 31.16	$ 22.93
Weighted Average Remaining Life in Years	4 years 4 months 24 days	4 years 1 month 5 days	4 years 3 months 17 days	4 years 7 months 5 days		4 years 6 months 0 days
Aggregate Intrinsic Value, Outstanding, Beginning Balance	$ 77	$ 75	$ 67	$ 62	$ 62
Aggregate Intrinsic Value, Exercised	24	0	1	1	30	19	10
Aggregate Intrinsic Value, Outstanding, Ending Balance	33	77	75	67	33	62
Stock Option
Schedule Of Stock Options [Line Items]
Unrecorded Tax Benefit From Stock Options Exercised					$ 12	$ 6	$ 10