Net Income Per Share - Computation of Basic and Diluted Net Income per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 27, 2017	Sep. 27, 2017	Jun. 28, 2017	Mar. 29, 2017	Dec. 28, 2016	Sep. 28, 2016	Jun. 29, 2016	Mar. 30, 2016	Dec. 27, 2017	Dec. 28, 2016	Dec. 30, 2015
Numerator:
Net income	$ (38)	$ (4,039)	$ 7,819	$ 4,877	$ 418	$ 5,211	$ 7,267	$ 5,443	$ 8,619	$ 18,339	$ 24,054
Denominator:
Weighted-average shares outstanding—Basic (shares)	38,465,208	38,462,100	38,449,240	38,437,020	38,437,020	38,415,189	38,294,575	38,284,435	38,453,347	38,357,805	37,949,316
Weighted-average shares outstanding—Diluted (shares)	38,465,208	38,462,100	39,123,961	39,079,007	39,108,967	39,083,577	38,962,802	39,001,078	39,086,676	39,026,950	39,039,558
Net income per share—Basic (usd per share)	$ 0.00	$ (0.11)	$ 0.20	$ 0.13	$ 0.01	$ 0.14	$ 0.19	$ 0.14	$ 0.22	$ 0.48	$ 0.63
Net income per share—Diluted (usd per share)	$ 0.00	$ (0.11)	$ 0.20	$ 0.12	$ 0.01	$ 0.13	$ 0.19	$ 0.14	$ 0.22	$ 0.47	$ 0.62
Anti-dilutive securities not considered in diluted EPS calculation (shares)	0	0							747,985	468,705	214,411