Segment Information (Details) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)
Segment Reporting [Abstract]
Number of operating segments (in segments) \| segment	2
Revenues from external customers
Revenues from external customers	$ 86,510	$ 82,630
Operating income
Operating income	16,169	15,137
Interest expense	4,592	4,050
Other income	(1,187)	(920)
Income before income taxes	12,764	12,007
U.S.
Revenues from external customers
Revenues from external customers	75,434	71,488
Operating income
Operating income	14,584	14,156
International
Revenues from external customers
Revenues from external customers	11,076	11,142
Operating income
Operating income	$ 1,585	$ 981

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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