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, 2013	$ 40	$ 211,952		$ (178,528)	$ 33,464
Beginning balance (in shares) at Dec. 31, 2013	39,983,437
Increase (Decrease) in Stockholders' Equity
Share-based compensation		2,857			2,857
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)				(10,925)	(10,925)
Other comprehensive income (loss)			$ (154)		(154)
Unrealized net gain (loss) on marketable securities, net of tax					(154)
Ending balance at Dec. 31, 2014	$ 43	230,263	(154)	(189,453)	40,699
Ending balance (in shares) at Dec. 31, 2014	42,974,463
Increase (Decrease) in Stockholders' Equity
Share-based compensation		4,090			4,090
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)				13,944	13,944
Other comprehensive income (loss)			(334)		(334)
Unrealized net gain (loss) on marketable securities, net of tax					(334)
Ending balance at Dec. 31, 2015	$ 49	263,955	(488)	(175,509)	88,007
Ending balance (in shares) at Dec. 31, 2015	49,004,674
Increase (Decrease) in Stockholders' Equity
Share-based compensation		5,926			5,926
Issuance of employee stock purchase plan shares		1,494			1,494
Issuance of employee stock purchase plan shares (in shares)	109,244
Exercise of stock options		557			557
Exercise of stock options (in shares)	85,694
Equity issued on conversion of convertible notes	$ 1	4,161			4,162
Equity issued on conversion of convertible notes (in shares)	771,655
Net income (loss)				91,221	91,221
Other comprehensive income (loss)					354
Unrealized net gain (loss) on marketable securities, net of tax			354		354
Other		34			34
Ending balance at Dec. 31, 2016	$ 50	$ 276,127	$ (134)	$ (84,288)	$ 191,755
Ending balance (in shares) at Dec. 31, 2016	49,971,267