Summary of Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 26, 2015 USD ($) $ / shares shares
Options Outstanding
Outstanding, beginning balance	898,429
Granted	465,005
Forfeited	(97,251)
Exercised	(66,786)
Outstanding, ending balance	1,199,397
Options exercisable at end of period	573,736
Weighted-Average Exercise Price
Outstanding, beginning balance | $ / shares	$ 44.40
Granted | $ / shares	58.57
Forfeited | $ / shares	55.06
Exercised | $ / shares	33.11
Outstanding, ending balance | $ / shares	50.04
Options exercisable at end of period | $ / shares	$ 42.49
Weighted-Average Remaining Contractual Term
Outstanding at end of period	4 years 7 months 6 days
Options exercisable at end of period	3 years 1 month 6 days
Aggregate Intrinsic Value
Outstanding at end of period | $	$ 1,961
Options exercisable at end of period | $	$ 1,961