Segment Information - Schedule of Selected Information for Each Business Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenues from external customers	$ 82,630	$ 81,359
Operating income
Operating income	15,137	11,927
Interest expense	4,050	5,420
Loss on extinguishment of debt	0	2,161
Other income	(920)	(577)
Income before income taxes	12,007	4,923
U.S.
Segment Reporting Information [Line Items]
Revenues from external customers	71,488	71,027
Operating income
Operating income	14,156	11,168
International
Segment Reporting Information [Line Items]
Revenues from external customers	11,142	10,332
Operating income
Operating income	$ 981	$ 759