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, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 31, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Net Income	$ 8,871	$ 8,303	$ 7,815	$ 7,472	$ 673	$ 4,171	$ 1,591	$ 2,600	$ 32,461	$ 9,035	$ 20,077
Weighted-average number of common shares outstanding
Basic weighted-average common shares outstanding (in shares)									11,518	11,390	11,290
Dilutive potential common shares (in shares)									274	269	268
Diluted weighted-average common shares outstanding (in shares)									11,792	11,659	11,558
Earnings Per Share
Basic earnings (loss) per share (in dollars per share)	$ 0.77	$ 0.72	$ 0.68	$ 0.65	$ 0.06	$ 0.37	$ 0.14	$ 0.23	$ 2.82	$ 0.79	$ 1.78
Diluted earnings (loss) per share (in dollars per share)	$ 0.75	$ 0.70	$ 0.66	$ 0.64	$ 0.06	$ 0.36	$ 0.14	$ 0.22	$ 2.75	$ 0.77	$ 1.74