Condensed Consolidated Statements Of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (12,116)	$ 23,819	$ (62,202)	$ 65,392
Other comprehensive income:
Net unrealized gains (loss) on available-for-sale securities, net of tax	(16)	(360)	38	1,470
Other comprehensive income	(16)	(360)	38	1,470
Comprehensive income (loss)	$ (12,132)	$ 23,459	$ (62,164)	$ 66,862