Quarterly Financial Data (Unaudited) - Condensed Summary of Actual Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 188,339	$ 198,349	$ 195,127	$ 173,416	$ 149,966	$ 153,604	$ 178,251	$ 180,291	$ 755,231	$ 662,112	$ 825,341
Gross Profit	23,211	25,150	22,701	21,503	18,276	18,919	24,331	25,704	92,565	87,230	110,822
Operating Income	8,638	10,682	7,568	4,557	3,910	4,466	8,427	8,580	31,445	25,383	38,026
Net Income (Loss)	$ (7,227)	$ 4,763	$ 131	$ 628	$ 355	$ 1,147	$ 2,720	$ 2,563	$ (1,705)	$ 6,785	$ 7,061
Basic and Diluted Earnings (Loss) Per Share	$ (0.24)	$ 0.16	$ 0.00	$ 0.02	$ 0.01	$ 0.04	$ 0.09	$ 0.09	$ (0.06)	$ 0.23	$ 0.24