Consolidated Statements of Changes in Stockholder's Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Total
Beginning balance at Dec. 31, 2012	$ 31	$ 143,851	$ (57)	$ (86,255)	$ 57,570
Beginning balance (in shares) at Dec. 31, 2012	30,621,869
Increase (Decrease) in Stockholders' Equity
Exercise of over allotment from secondary offering		1,791			1,791
Exercise of over allotment from secondary offering (in shares)	239,432
Share-based compensation		1,913			1,913
Issuance of employee stock purchase plan shares		444			444
Issuance of employee stock purchase plan shares (in shares)	81,370
Exercise of stock options		78			78
Exercise of stock options (in shares)	62,513
Equity conversion feature on issuance of convertible notes, less issuance costs of $869		21,467			21,467
Equity issued on conversion of convertible notes	$ 9	42,408			42,417
Equity issued on conversion of convertible notes (in shares)	8,978,253
Net income (loss)				(92,273)	(92,273)
Other comprehensive income (loss)			57		57
Ending balance at Dec. 31, 2013	$ 40	211,952		(178,528)	33,464
Ending balance (in shares) at Dec. 31, 2013	39,983,437
Increase (Decrease) in Stockholders' Equity
Share-based compensation		2,716			2,716
Issuance of employee stock purchase plan shares		516			516
Issuance of employee stock purchase plan shares (in shares)	76,333
Exercise of stock options		54			54
Exercise of stock options (in shares)	17,627
Equity issued on conversion of convertible notes	$ 3	14,884			14,887
Equity issued on conversion of convertible notes (in shares)	2,897,066
Net income (loss)				19,871	19,871
Other comprehensive income (loss)			(154)		(154)
Ending balance at Dec. 31, 2014	$ 43	230,122	(154)	(158,657)	71,354
Ending balance (in shares) at Dec. 31, 2014	42,974,463
Increase (Decrease) in Stockholders' Equity
Share-based compensation		4,231			4,231
Issuance of employee stock purchase plan shares		930			930
Issuance of employee stock purchase plan shares (in shares)	98,986
Exercise of stock options		937			937
Exercise of stock options (in shares)	205,640
Equity issued on conversion of convertible notes	$ 6	27,083			27,089
Equity issued on conversion of convertible notes (in shares)	5,693,062
Exercise of warrants		652			652
Exercise of warrants (in shares)	32,523
Net income (loss)				14,016	14,016
Other comprehensive income (loss)			(334)		(334)
Ending balance at Dec. 31, 2015	$ 49	$ 263,955	$ (488)	$ (144,641)	$ 118,875
Ending balance (in shares) at Dec. 31, 2015	49,004,674