Segment Information (Details) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) segment	Jun. 30, 2018 USD ($)
Segment Reporting [Abstract]
Number of operating segments (in segments) | segment				2
Revenues from external customers
Revenues from external customers		$ 85,705	$ 85,573	$ 172,215	$ 168,203
Operating income
Operating income		14,537	15,926	30,706	31,063
Interest expense		4,543	4,298	9,135	8,348
Loss on extinguishment of debt	$ 3,200	3,196	0	3,196	0
Other income		(1,312)	(336)	(2,499)	(1,256)
Income before income taxes		8,110	11,964	20,874	23,971
U.S.
Revenues from external customers
Revenues from external customers		75,190	74,086	150,624	145,574
Operating income
Operating income		12,689	14,292	27,273	28,448
International
Revenues from external customers
Revenues from external customers		10,515	11,487	21,591	22,629
Operating income
Operating income		$ 1,848	$ 1,634	$ 3,433	$ 2,615