Segment Information - Schedule of Selected Information for Each Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenues from external customers	$ 79,941	$ 73,063	$ 250,137	$ 227,503
Operating income
Operating income	12,822	12,595	42,646	44,447
Interest expense	4,442	6,792	14,147	20,799
Debt retirement costs	0	1,415	0	1,415
Loss on extinguishment of debt	0	0	2,161	0
Other (income) expense	(908)	148	(2,037)	(317)
Income before income taxes	9,288	4,240	28,375	22,550
U.S.
Segment Reporting Information [Line Items]
Revenues from external customers	69,579	62,621	218,706	192,687
Operating income
Operating income	12,243	11,649	40,306	35,941
International
Segment Reporting Information [Line Items]
Revenues from external customers	10,362	10,442	31,431	34,816
Operating income
Operating income	$ 579	$ 946	$ 2,340	$ 8,506