Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Accumulated Deficit
Beginning balance at Dec. 31, 2017	$ 242,973	$ 117	$ 290,751	$ 0	$ (47,895)
Beginning balance (in shares) at Dec. 31, 2017		11,696		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation	10,978		10,978
Numerator: Net loss	(32,167)				(32,167)
Ending balance at Mar. 31, 2018	221,784	$ 117	301,729	$ 0	(80,062)
Ending balance (in shares) at Mar. 31, 2018		11,696		0
Beginning balance at Dec. 31, 2018	196,427	$ 122	303,463	$ 0	(107,158)
Beginning balance (in shares) at Dec. 31, 2018		12,233		0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for Rights Offering	32,175	$ 34	32,141
Issuance of common stock for rights offering (in shares)		3,382
Issuance of common stock to employees		$ 1	(1)
Issuance of common stock to employees (in shares)		97
Treasury stock acquired through surrender of shares for tax withholding	(373)			$ (373)
Treasury stock acquired through surrender of shares for tax withholding (in shares)				(34)
Share-based compensation	852		852
Numerator: Net loss	(6,355)				(6,355)
Ending balance at Mar. 31, 2019	$ 221,903	$ 157	$ 336,455	$ (373)	$ (114,336)
Ending balance (in shares) at Mar. 31, 2019		15,712		34