CONSOLIDATED STATEMENTS OF COMPREHENSIVE iNCOME / LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 36,908	$ (102,496)	$ (88,720)
Unrealized gain on available-for-sale securities, net of tax	0	14	35
Comprehensive income (loss)	$ 36,908	$ (102,482)	$ (88,685)