Stock Option Plans - Stock Option Activity and Related Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Under Option, Beginning balance	7.9	8.8
Shares Under Option, Granted	1.6	1.3
Shares Under Option, Exercised	(1.8)	(1.9)
Shares Under Option, Forfeited or canceled	(0.2)	(0.3)
Shares Under Option, Ending balance	7.5	7.9
Shares Under Option, Exercisable at end of year	1.9	2.0
Shares Under Option, Ending unvested and expected to vest	5.3	5.7
Weighted Average Exercise Price, Beginning balance	$ 56.40	$ 50.16
Weighted Average Exercise Price, Granted	86.17	79.59
Weighted Average Exercise Price, Exercised	45.80	42.91
Weighted Average Exercise Price, Forfeited or canceled	65.87	57.33
Weighted Average Exercise Price, Ending balance	65.09	56.40
Weighted Average Exercise Price, Exercisable at end of year	47.17	45.03
Weighted Average Exercise Price, Ending unvested and expected to vest	$ 70.74	$ 59.76
Weighted Average Remaining Contractual Term (in years), Ending balance	3 years 10 months 9 days	3 years 9 months
Weighted Average Remaining Contractual Term (in years), Exercisable at end of year	1 year 9 months 29 days	1 year 9 months 25 days
Weighted Average Remaining Contractual Term (in years), Ending unvested and expected to vest	4 years 6 months 3 days	4 years 4 months 9 days
Aggregate Intrinsic Value, Ending Balance	$ 437.9	$ 308.6
Aggregate Intrinsic Value, Exercisable at end of year	147.2	101.9
Aggregate Intrinsic Value, Ending unvested and expected to vest	$ 278.1	$ 201.5