Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 16,692	$ (52,781)	$ 52,601	$ (38,126)
Other comprehensive income (loss):
Unrealized gains (losses) on marketable securities, net of tax	(2)	(22)	415	(22)
Comprehensive income (loss)	$ 16,690	$ (52,803)	$ 53,016	$ (38,148)