Stock Option Plans - Stock Options Outstanding and Exercisable (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 21.28
Range of Exercise Prices, maximum	$ 46.87
Option Outstanding, Number Outstanding	8.4
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	3 years 11 months 16 days	3 years 7 months 13 days	3 years 4 months 28 days
Option Outstanding, Weighted Average Exercise Price	$ 35.49	$ 31.35	$ 28.80	$ 27.20
Options Exercisable, Number Exercisable	2.6
Option Exercisable, Weighted Average Exercise Price	$ 26.91
Exercise Prices Range $ 21.28 - $ 27.25 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 21.28
Range of Exercise Prices, maximum	$ 27.25
Option Outstanding, Number Outstanding	2.3
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	1 year 7 months 2 days
Option Outstanding, Weighted Average Exercise Price	$ 25.78
Options Exercisable, Number Exercisable	1.9
Option Exercisable, Weighted Average Exercise Price	$ 25.76
Exercise Prices Range $ 27.35 - $ 35.71 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 27.35
Range of Exercise Prices, maximum	$ 35.71
Option Outstanding, Number Outstanding	2.5
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	3 years 7 months 2 days
Option Outstanding, Weighted Average Exercise Price	$ 33.18
Options Exercisable, Number Exercisable	0.7
Option Exercisable, Weighted Average Exercise Price	$ 29.83
Exercise Prices Range $ 35.95 - $ 39.17 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 35.95
Range of Exercise Prices, maximum	$ 46.16
Option Outstanding, Number Outstanding	1.7
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	5 years 2 months 12 days
Option Outstanding, Weighted Average Exercise Price	$ 39.19
Options Exercisable, Number Exercisable	0
Option Exercisable, Weighted Average Exercise Price	$ 0.00
Exercise Prices Range $ 46.16 - $ 46.16 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Prices, minimum	$ 46.87
Range of Exercise Prices, maximum	$ 46.87
Option Outstanding, Number Outstanding	1.9
Option Outstanding, Weighted Average Remaining Contractual Term (in years)	6 years 2 months 9 days
Option Outstanding, Weighted Average Exercise Price	$ 46.87
Options Exercisable, Number Exercisable	0
Option Exercisable, Weighted Average Exercise Price	$ 0.00