Income Taxes - Schedule of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
State	$ 500	$ 745	$ 270
Federal	0	0	513
Foreign	0	0	2,336
Current income tax expense (benefit)	500	745	3,119
Deferred:
Foreign	0	0	(755)
Deferred income tax expense (benefit)	0	0	(755)
Income tax expense	$ 500	$ 745	$ 2,364