Summary of Significant Accounting Policies - Weighted Average Number of Shares Outstanding Used to Compute Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 31, 2013	Sep. 28, 2013	Jun. 29, 2013	Mar. 30, 2013	Jun. 28, 2014	Jun. 29, 2013	Sep. 27, 2014	Sep. 28, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Net Income	$ 5,156	$ 2,933	$ 6,619	$ 5,159	$ (5,244)	$ 6,985	$ 5,666	$ 3,971	$ 11,778	$ 9,637	$ 14,711	$ 16,622	$ 19,867	$ 11,378	$ 17,623
Weighted-average number of common shares outstanding
Basic weighted-average common shares outstanding		10,921	10,871	10,844		10,722	10,648	10,600	10,864	10,624	10,902	10,657	10,897	10,695	10,580
Dilutive potential common shares													229	157	48
Diluted weighted-average common shares outstanding		11,150	11,045	11,107		10,917	10,790	10,670	11,122	10,731	11,202	10,785	11,126	10,852	10,628
Earnings Per Share
Basic (in dollars per share)	$ 0.47	$ 0.27	$ 0.61	$ 0.48	$ (0.49)	$ 0.65	$ 0.53	$ 0.37	$ 1.08	$ 0.91	$ 1.35	$ 1.56	$ 1.82	$ 1.06	$ 1.67
Diluted (in dollars per share)	$ 0.46	$ 0.26	$ 0.60	$ 0.46	$ (0.49)	$ 0.64	$ 0.53	$ 0.37	$ 1.06	$ 0.90	$ 1.31	$ 1.54	$ 1.79	$ 1.05	$ 1.66