Stock Option Plans - Stock Option Activity and Related Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Shares Under Option, Beginning balance	8.3	9.0	10.6
Shares Under Option, Granted	1.9	1.7	1.4
Shares Under Option, Exercised	(1.7)	(2.3)	(2.8)
Shares Under Option, Forfeited or canceled	(0.1)	(0.1)	(0.2)
Shares Under Option, Ending balance	8.4	8.3	9.0
Shares Under Option, Exercisable at end of period	2.6	3.8	5.1
Shares Under Option, Ending vested and expected to vest	8.3	8.2	8.9
Weighted Average Exercise Price, Beginning balance	$ 31.35	$ 28.80	$ 27.20
Weighted Average Exercise Price, Granted	$ 46.86	$ 39.17	$ 35.71
Weighted Average Exercise Price, Exercised	$ 28.80	$ 27.11	$ 26.14
Weighted Average Exercise Price, Forfeited or canceled	$ 28.36	$ 26.01	$ 29.46
Weighted Average Exercised Price, Ending balance	$ 35.49	$ 31.35	$ 28.80
Weighted Average Exercise Price, Exercisable at end of period	$ 26.91	$ 27.64	$ 27.50
Weighted Average Exercise price, Ending vested and expected to vest	$ 35.38	$ 31.28	$ 28.76
Weighted Average Remaining Contractual Term (in years), Ending balance	3 years 11 months 16 days	3 years 7 months 13 days	3 years 4 months 28 days
Weighted Average Remaining Contractual Term (in years), Exercisable at end of period	1 year 10 months 13 days	2 years 1 month 24 days	2 years 6 months 7 days
Weighted Average Remaining Contractual Term (in years), Ending vested and expected to vested	3 years 11 months 5 days	3 years 7 months 2 days	3 years 4 months 21 days
Aggregate Intrinsic Value, Ending Balance	$ 97.2	$ 129.4	$ 53.9
Aggregate Intrinsic Value, Exercisable at end of period	52.8	72.5	36.3
Aggregate Intrinsic Value, Ending vested and expected to vest	$ 96.6	$ 128.3	$ 53.8