Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income (loss)	$ 29,993	$ 2,577	$ (4,440)
Available-for-sale investments
Net change in unrealized gain (loss) on available-for-sale investments	(15)	30	(87)
Less: Reclassification adjustment for net gains on investments recognized during the year	(5)	(3)	(7)
Net change in unrealized gain (loss) on available-for-sale investments	(20)	27	(94)
Tax provision		10
Other comprehensive income (loss), net of tax	(20)	17	(94)
Comprehensive income (loss)	$ 29,973	$ 2,594	$ (4,534)