Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Preferred Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning Balances at Dec. 31, 2013	$ 186,294	$ 263		$ 688,390	$ (148)	$ (502,211)
Beginning Balances (in shares) at Dec. 31, 2013		26,280	43
Issuance (withholding) of common stock upon exercise of stock options and restricted stock awards, net	49			49
Issuance (withholding) of common stock upon exercise of stock options and restricted stock awards, net (in shares)		5
Reverse stock split		$ (237)		237
Issuance of common stock under Employee Stock Purchase Plan	130			130
Issuance of common stock under Employee Stock Purchase Plan (in shares)		11
Warrants exercised	163			163
Warrants exercised (in shares)		11
Stock compensation expense	6,089			6,089
Total other comprehensive loss	(1,521)				(1,521)
Net loss	(90,722)					(90,722)
Ending Balances at Dec. 31, 2014	100,482	$ 26		695,058	(1,669)	(592,933)
Ending Balances (in shares) at Dec. 31, 2014		26,307	43
Conversion of Preferred Stock	2	$ 5		(3)
Conversion of Preferred Stock (in shares)		4,343	(43)
Issuance (withholding) of common stock upon exercise of stock options and restricted stock awards, net	531			531
Issuance (withholding) of common stock upon exercise of stock options and restricted stock awards, net (in shares)		37
Issuance of common stock under Employee Stock Purchase Plan	291			291
Issuance of common stock under Employee Stock Purchase Plan (in shares)		23
Issuance of common stock, net of issuance costs	183,897	$ 7		183,890
Issuance of common stock, net of issuance costs (in shares)		7,353
Warrants exercised	228			228
Warrants exercised (in shares)		383
Stock compensation expense	9,703			9,703
Total other comprehensive loss	(1,261)				(1,261)
Net loss	(106,794)					(106,794)
Ending Balances at Dec. 31, 2015	187,079	$ 38		889,698	(2,930)	(699,727)
Ending Balances (in shares) at Dec. 31, 2015		38,446
Issuance (withholding) of common stock upon exercise of stock options and restricted stock awards, net	(83)	$ 1		(84)
Issuance (withholding) of common stock upon exercise of stock options and restricted stock awards, net (in shares)		107
Issuance of common stock under Employee Stock Purchase Plan	615			615
Issuance of common stock under Employee Stock Purchase Plan (in shares)		46
Stock compensation expense	14,728			14,728
Total other comprehensive loss	(694)				(694)
Net loss	(112,444)					(112,444)
Ending Balances at Dec. 31, 2016	$ 89,201	$ 39		$ 904,957	$ (3,624)	$ (812,171)
Ending Balances (in shares) at Dec. 31, 2016		38,599