Summary of Options (Detail) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares shares
NUMBER OF SHARES
Options outstanding, beginning balance | shares	4,421,600
Granted | shares	792,700
Exercised | shares	(679,900)
Cancelled | shares	(67,500)
Options outstanding, ending balance | shares	4,466,900
Vested and expected to vest, end of period | shares	4,348,300
Exercisable, end of period | shares	2,629,100
PER SHARE EXERCISE PRICE
Options outstanding, beginning balance | $ / shares	$ 47.23	[1]
Granted | $ / shares	50.00	[1]
Exercised | $ / shares	43.16	[1]
Cancelled | $ / shares	59.53	[1]
Options outstanding, ending balance | $ / shares	48.15	[1]
Vested and expected to vest, end of period | $ / shares	48.06	[1]
Exercisable, end of period | $ / shares	$ 42.58	[1]
REMAINING CONTRACTUAL LIFE IN YEARS
Options outstanding, ending balance	5 years 9 months 11 days	[1]
Vested and expected to vest, end of period	5 years 8 months 16 days	[1]
Exercisable, end of period	4 years 29 days	[1]
AGGREGATE INTRINSIC VALUE
Options outstanding, ending balance | $	$ 70.3
Vested and expected to vest, end of period | $	68.9
Exercisable, end of period | $	$ 56.1

[1] Weighted Average