Summary of Options (Detail) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) $ / shares shares
NUMBER OF SHARES
Options outstanding, beginning balance | shares	4,536,700
Granted | shares	569,500
Exercised | shares	(582,300)
Cancelled | shares	(102,300)
Options outstanding, ending balance | shares	4,421,600
Vested and expected to vest, end of period | shares	4,325,600
Exercisable, end of period | shares	2,590,700
PER SHARE EXERCISE PRICE
Options outstanding, beginning balance | $ / shares	$ 44.25	[1]
Granted | $ / shares	62.46	[1]
Exercised | $ / shares	37.50	[1]
Cancelled | $ / shares	55.17	[1]
Options outstanding, ending balance | $ / shares	47.23	[1]
Vested and expected to vest, end of period | $ / shares	46.93	[1]
Exercisable, end of period | $ / shares	$ 41.14	[1]
REMAINING CONTRACTUAL LIFE IN YEARS
Options outstanding, ending balance	5 years 8 months 9 days	[1]
Vested and expected to vest, end of period	5 years 7 months 17 days	[1]
Exercisable, end of period	4 years 15 days	[1]
AGGREGATE INTRINSIC VALUE
Options outstanding, ending balance | $	$ 17.5
Vested and expected to vest, end of period | $	17.5
Exercisable, end of period | $	$ 17.5

[1] Weighted Average