Accumulated Other Comprehensive Loss (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance	$ 167,825
Net other comprehensive income (loss)	154
Ending balance	290,404
Tax benefit for other comprehensive income (loss)	0
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Beginning balance	(451)
Ending balance	(297)
Unrealized Gains (Losses) on Investments [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Other comprehensive loss before reclassifications, net of tax	106	[1]
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Loss [Roll Forward]
Other comprehensive loss before reclassifications, net of tax	$ 48

[1] There was no tax benefit for other comprehensive income (loss) for the six months ended June 30, 2018.