Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period (in shares) at Dec. 31, 2017		8,386,000
Balance at beginning of period at Dec. 31, 2017	$ 75,062	$ 8	$ 594,662	$ (520,001)	$ (2,942)	$ 3,335
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	2,143		2,143
Issuance of restricted stock (in shares)		9,000
Issuance of restricted stock	0
Restricted stock expense	905		905
Exercise of common stock options (in shares)		26,000
Exercise of common stock options	705		705
Non-employee restricted stock expense	(27)		(27)
Net loss	(19,767)			(19,767)
Other comprehensive income	(127)					(127)
Balance at end of period (in shares) at Mar. 31, 2018		8,421,000
Balance at end of period at Mar. 31, 2018	58,894	$ 8	598,388	(539,768)	(2,942)	3,208
Balance at beginning of period (in shares) at Dec. 31, 2017		8,386,000
Balance at beginning of period at Dec. 31, 2017	75,062	$ 8	594,662	(520,001)	(2,942)	3,335
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(43,643)
Balance at end of period (in shares) at Jun. 30, 2018		8,513,000
Balance at end of period at Jun. 30, 2018	39,626	$ 8	604,311	(563,644)	(3,705)	2,656
Balance at beginning of period (in shares) at Mar. 31, 2018		8,421,000
Balance at beginning of period at Mar. 31, 2018	58,894	$ 8	598,388	(539,768)	(2,942)	3,208
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock purchase plan (in shares)		28,000
Employee stock purchase plan	999		999
Treasury stock purchased (in shares)		21,000
Treasury stock purchased	(763)				(763)
Stock-based compensation expense	3,227		3,227
Issuance of restricted stock (in shares)		26,000
Issuance of restricted stock	0	$ 0
Restricted stock expense	989		989
Exercise of common stock options (in shares)		17,000
Exercise of common stock options	659		659
Non-employee restricted stock expense	49		49
Net loss	(23,876)			(23,876)
Other comprehensive income	(552)					(552)
Balance at end of period (in shares) at Jun. 30, 2018		8,513,000
Balance at end of period at Jun. 30, 2018	$ 39,626	$ 8	604,311	(563,644)	(3,705)	2,656
Balance at beginning of period (in shares) at Dec. 31, 2018	10,345,367	10,388,000
Balance at beginning of period at Dec. 31, 2018	$ 39,646	$ 10	640,789	(599,715)	(4,026)	2,588
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Treasury stock purchased	(1)				(1)
Stock-based compensation expense	1,512		1,512
Issuance of restricted stock (in shares)		3,000
Issuance of restricted stock	0
Restricted stock expense	849		849
Net loss	(22,028)			(22,028)
Other comprehensive income	(598)					(598)
Balance at end of period (in shares) at Mar. 31, 2019		10,391,000
Balance at end of period at Mar. 31, 2019	$ 19,380	$ 10	643,150	(621,743)	(4,027)	1,990
Balance at beginning of period (in shares) at Dec. 31, 2018	10,345,367	10,388,000
Balance at beginning of period at Dec. 31, 2018	$ 39,646	$ 10	640,789	(599,715)	(4,026)	2,588
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	$ (49,162)
Balance at end of period (in shares) at Jun. 30, 2019	17,352,698	17,409,000
Balance at end of period at Jun. 30, 2019	$ 72,076	$ 17	722,478	(648,877)	(4,120)	2,578
Balance at beginning of period (in shares) at Mar. 31, 2019		10,391,000
Balance at beginning of period at Mar. 31, 2019	19,380	$ 10	643,150	(621,743)	(4,027)	1,990
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock purchase plan (in shares)		42,000
Employee stock purchase plan	207		207
Treasury stock purchased (in shares)		13,000
Treasury stock purchased	(93)				(93)
Stock-based compensation expense	1,355		1,355
Issuance of restricted stock (in shares)		35,000
Issuance of restricted stock	0
Prepaid warrants	9,700		9,700
Restricted stock expense	1,168		1,168
Deerfield warrants	4,854		4,854
Debt issuance cost allocated to equity	(762)		(762)
Equity conversion option	18,651		18,651
Issuance of common stock (in shares)		6,422,000
Issuance of common stock	42,285	$ 6	42,279
Shares issued upon conversion of debt (in shares)		506,000
Shares issued upon conversion of debt	1,877	$ 1	1,876
Net loss	(27,134)			(27,134)
Other comprehensive income	$ 588					588
Balance at end of period (in shares) at Jun. 30, 2019	17,352,698	17,409,000
Balance at end of period at Jun. 30, 2019	$ 72,076	$ 17	$ 722,478	$ (648,877)	$ (4,120)	$ 2,578