Summary of Significant Accounting Policies - Weighted Average Number of Shares Outstanding Used to Compute Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Net Income	$ 673	$ 4,171	$ 1,591	$ 2,600	$ 9,484	$ 4,655	$ 3,823	$ 2,115	$ 9,035	$ 20,077	$ 25,261
Weighted-average number of common shares outstanding
Basic weighted-average common shares outstanding (in shares)									11,390	11,290	11,151
Dilutive potential common shares (in shares)									269	268	148
Diluted weighted-average common shares outstanding (in shares)									11,659	11,558	11,299
Earnings Per Share
Basic earnings (loss) per share (in dollars per share)	$ 0.06	$ 0.37	$ 0.14	$ 0.23	$ 0.84	$ 0.41	$ 0.34	$ 0.19	$ 0.79	$ 1.78	$ 2.27
Diluted earnings (loss) per share (in dollars per share)	$ 0.06	$ 0.36	$ 0.14	$ 0.22	$ 0.82	$ 0.41	$ 0.33	$ 0.18	$ 0.77	$ 1.74	$ 2.24