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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 149,966	$ 153,604	$ 178,251	$ 180,291	$ 184,692	$ 202,729	$ 217,617	$ 220,303	$ 662,112	$ 825,341	$ 839,743
Gross Profit	18,276	18,919	24,331	25,704	24,352	27,890	29,506	29,074	87,230	110,822	107,688
Operating Income	3,910	4,466	8,427	8,580	5,294	9,946	11,588	11,198	25,383	38,026	33,693
Net income	355	1,147	2,720	2,563	(2,291)	2,554	3,205	3,593	6,785	7,061	7,631
Net Income (Loss) Attributable to Common Stockholders	$ 355	$ 1,147	$ 2,720	$ 2,563	$ (2,291)	$ 2,554	$ 3,205	$ 3,592	$ 6,785	$ 7,060	$ 7,630
Basic (in dollars per share)	$ 0.01	$ 0.04	$ 0.09	$ 0.09	$ (0.08)	$ 0.09	$ 0.11	$ 0.12	$ 0.23	$ 0.24	$ 0.26
Diluted (in dollars per share)	$ 0.01	$ 0.04	$ 0.09	$ 0.09	$ (0.08)	$ 0.09	$ 0.11	$ 0.12	$ 0.23	$ 0.24	$ 0.26