Quarterly Financial Data (Unaudited) - Summary of Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Oct. 01, 2016	Jul. 02, 2016	Apr. 02, 2016	Dec. 31, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Operating revenue	$ 264,051	$ 271,493	$ 276,813	$ 260,394	$ 285,991	$ 284,214	$ 295,007	$ 263,561	$ 1,072,751	$ 1,128,773	$ 1,191,521
Operating income	5,849	10,027	16,774	13,930	18,464	16,944	22,920	15,067	46,580	73,395	80,835
Income before income taxes	4,410	8,119	14,771	12,105	15,088	15,001	21,584	13,332
Provision for income taxes	1,687	3,122	5,724	4,628	5,782	5,754	8,300	5,168	15,161	25,004	27,729
Net income	$ 2,723	$ 4,997	$ 9,047	$ 7,477	$ 9,306	$ 9,247	$ 13,284	$ 8,164	$ 24,244	$ 40,001	$ 45,370
Earnings per common share:
Basic	$ 0.10	$ 0.18	$ 0.32	$ 0.26	$ 0.33	$ 0.32	$ 0.44	$ 0.27	$ 0.85	$ 1.37	$ 1.51
Diluted	$ 0.10	$ 0.18	$ 0.32	$ 0.26	$ 0.33	$ 0.32	$ 0.44	$ 0.27	$ 0.85	$ 1.37	$ 1.51
Weighted average number of common shares outstanding:
Basic	28,415	28,413	28,414	28,402	28,380	28,661	29,979	29,992	28,411	29,233	30,013
Diluted	28,415	28,413	28,414	28,402	28,382	28,661	29,980	29,998	28,411	29,235	30,044