Net Income Per Share - Computation of Basic and Diluted Net Income per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 27, 2018	Jun. 28, 2017	Jun. 27, 2018	Jun. 28, 2017
Numerator:
Net income	$ 5,052	$ 7,819	$ 7,581	$ 12,696
Denominator:
Weighted-average shares outstanding—basic (shares)	38,482,074	38,449,240	38,473,641	38,443,130
Weighted-average shares outstanding—diluted (shares)	39,043,434	39,123,961	39,015,259	39,102,501
Net income per share—basic (usd per share)	$ 0.13	$ 0.20	$ 0.20	$ 0.33
Net income per share—diluted (usd per share)	$ 0.13	$ 0.20	$ 0.19	$ 0.32
Anti-dilutive securities not considered in diluted EPS calculation (shares)	570,774	763,761	570,774	763,761