CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Earnings (Deficit)	Accumulated Other Comprehensive Loss
Balances at Dec. 31, 2017	$ 169,508	$ 6	$ 389,015	$ (219,508)	$ (5)
Balances (in shares) at Dec. 31, 2017		63,400,000
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of options	636		636
Issuance of common stock upon exercise of options (in shares)		120,000
Issuance of common stock in conjunction with vesting of restricted stock units (in shares)		33,000
Stock-based compensation	2,234		2,234
Shares withheld for payment of employee's withholding tax liability	(114)		(114)
Net (loss) income	33,824			33,824
Unrealized gain on available-for-sale securities	2				2
Balances at Mar. 31, 2018	206,090	$ 6	391,771	(185,684)	(3)
Balances (in shares) at Mar. 31, 2018		63,553,000
Balances at Dec. 31, 2018	220,335	$ 6	402,934	(182,600)	(5)
Balances (in shares) at Dec. 31, 2018		64,185,000
Increase (Decrease) in Stockholders' Equity
Issuance of common stock upon exercise of options	25		25
Issuance of common stock upon exercise of options (in shares)		14,000
Issuance of common stock in conjunction with vesting of restricted stock units (in shares)		132,000
Stock-based compensation	2,702		2,702
Shares withheld for payment of employee's withholding tax liability	(216)		(216)
Net (loss) income	(14,301)			(14,301)
Unrealized gain on available-for-sale securities	0
Balances at Mar. 31, 2019	$ 208,545	$ 6	$ 405,445	$ (196,901)	$ (5)
Balances (in shares) at Mar. 31, 2019		64,331,000