Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income (loss)	$ (30,770)	$ 29,993	$ 2,577
Available-for-sale investments
Net change in unrealized gain (loss) on available-for-sale investments	14	(15)	30
Less: Reclassification adjustment for net gains on investments recognized during the year	9	(5)	(3)
Net change in unrealized gain (loss) on available-for-sale investments	23	(20)	27
Tax provision			10
Other comprehensive income (loss), net of tax	23	(20)	17
Comprehensive income (loss)	$ (30,747)	$ 29,973	$ 2,594