Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 160,857	$ 126,991	$ 111,072
Other comprehensive income (loss)	958	110	(1,019)
Ending balance	179,189	160,857	126,991
Unrealized Gain (Loss) on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(8)	(16)	(18)
Current period other comprehensive income (loss) before reclassifications	(56)	8	2
Reclassification of amounts to earnings	0	0
Other comprehensive income (loss)	(56)	8
Ending balance	(64)	(8)	(16)
Gain (loss) on Derivative Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(24)	0	0
Current period other comprehensive income (loss) before reclassifications	80	(450)	0
Reclassification of amounts to earnings	160	426
Other comprehensive income (loss)	240	(24)
Ending balance	216	(24)	0
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,185)	(1,311)	(290)
Current period other comprehensive income (loss) before reclassifications	774	126	(1,021)
Reclassification of amounts to earnings	0	0
Other comprehensive income (loss)	774	126
Ending balance	(411)	(1,185)	(1,311)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(1,217)	(1,327)	(308)
Current period other comprehensive income (loss) before reclassifications	798	(316)	(1,019)
Reclassification of amounts to earnings	160	426
Other comprehensive income (loss)	958	110
Ending balance	$ (259)	$ (1,217)	$ (1,327)