Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (2,262)	$ (623)
Change in unrealized gain (loss) on available-for-sale- securities, net of tax	35	(24)
Comprehensive loss, net of income tax	$ (2,227)	$ (647)