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, 2016		8,299,000
Balance at beginning of period at Dec. 31, 2016	$ 112,793	$ 8	$ 567,840	$ (453,601)	$ (2,942)	$ 1,488
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		13,000
Exercise of common stock options	546		546
Employee stock purchase plan (in shares)		45,000
Employee stock purchase plan	2,519		2,519
Stock-based compensation expense	8,538		8,538
Issuance of restricted stock (in shares)		29,000
Issuance of restricted stock	0
Restricted stock expense	3,106		3,106
Equity conversion option	(2,235)		(2,235)
Deerfield warrants	14,704		14,704
Debt issuance costs allocated to equity	(356)		(356)
Net loss	(66,400)			(66,400)
Other comprehensive income (loss)	1,847					1,847
Balance at end of period (in shares) at Dec. 31, 2017		8,386,000
Balance at end of period at Dec. 31, 2017	75,062	$ 8	594,662	(520,001)	(2,942)	3,335
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of common stock options (in shares)		44,000
Exercise of common stock options	1,586	$ 0	1,586
Employee stock purchase plan (in shares)		61,000
Employee stock purchase plan	1,346	$ 0	1,346
Issuance of common stock (in shares)		1,841,000
Issuance of common stock	21,829	$ 2	21,827
Treasury stock purchased (in shares)		21,000
Treasury stock purchased	(1,084)				(1,084)
Stock-based compensation expense	8,404		8,404
Issuance of restricted stock (in shares)		35,000
Issuance of restricted stock	0		0
Restricted stock expense	2,626		2,626
Deerfield warrants	10,396		10,396	0
Debt issuance costs allocated to equity	(58)		(58)
Net loss	(79,714)			(79,714)
Other comprehensive income (loss)	$ (747)					(747)
Balance at end of period (in shares) at Dec. 31, 2018	10,345,367	10,388,000
Balance at end of period at Dec. 31, 2018	$ 39,646	$ 10	640,789	(599,715)	(4,026)	2,588
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock purchase plan (in shares)		107,000
Employee stock purchase plan	344	$ 0	344		0
Issuance of common stock (in shares)		6,422,000
Issuance of common stock	42,285	$ 6	42,279
Treasury stock purchased (in shares)		49,000
Treasury stock purchased	(209)				(209)
Stock-based compensation expense	5,986		5,986
Issuance of restricted stock (in shares)		206,000
Issuance of restricted stock	1	$ 1
Restricted stock expense	4,862		4,862
Equity conversion option	19,321
Deerfield warrants	4,854		4,854
Prepaid warrants	9,700		9,700
Debt issuance costs allocated to equity	(762)		(762)
Shares issued upon conversion of debt (in shares)		1,018,000
Shares issued upon conversion of debt	3,357	$ 1	3,356
Net loss	(64,757)			(64,757)
Other comprehensive income (loss)	$ (772)					(772)
Balance at end of period (in shares) at Dec. 31, 2019	18,098,464	18,190,000
Balance at end of period at Dec. 31, 2019	$ 63,856	$ 18	$ 730,729	$ (664,472)	$ (4,235)	$ 1,816