Consolidated Statement of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2013	$ 18,426	$ 17	$ 428,656	$ 0	$ (410,247)
Beginning balance, shares at Dec. 31, 2013		17,365
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	8,587				8,587
Issuance of common stock in conjunction with exercise of stock options	343		343
Issuance of common stock in conjunction with exercise of stock options, shares		20
Issuance of common stock from ESPP purchase	556	$ 0	556
Issuance of common stock from ESPP purchase, shares		63
Issuance of common stock in connection with exercise of warrants	2,079		2,079
Issuance of common stock in conjunction with the exercise of warrants, shares		58
Issuance of common stock in conjunction with vesting of restricted stock units	1	$ 0	1
Issuance of common stock in conjunction with vesting of restricted stock units, shares		165
Issuance of common stock in connection with acquisition	15,237	$ 2	15,235
Issuance of common stock in conjunction with acquisition, shares		1,499
Issuance of common stock warrants in connection with debt	558		558
Stock-based compensation	9,492		9,492
Reclassification of other-than-temporary loss on available-for-sale securities included in net income	0
Ending balance at Dec. 31, 2014	55,279	$ 19	456,920	0	(401,660)
Ending balance, shares at Dec. 31, 2014		19,170
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	26,144				26,144
Issuance of common stock from offering, net of issuance costs	92,007	$ 5	92,002
Issuance of common stock from offering, net of issuance costs, shares		5,463
Issuance of common stock in conjunction with exercise of stock options	1,441	$ 1	1,440
Issuance of common stock in conjunction with exercise of stock options, shares		96
Issuance of common stock from ESPP purchase	203		203
Issuance of common stock from ESPP purchase, shares		26
Issuance of common stock in connection with exercise of warrants	0		0
Issuance of common stock in conjunction with the exercise of warrants, shares		17
Stock-based compensation	7,686		7,686
Unrealized loss on available-for-sale securities	5,485			5,485
Reclassification of other-than-temporary loss on available-for-sale securities included in net income	(5,485)			(5,485)
Ending balance at Dec. 31, 2015	182,760	$ 25	558,251	0	(375,516)
Ending balance, shares at Dec. 31, 2015		24,772
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(69,707)				(69,707)
Issuance of common stock in conjunction with exercise of stock options	$ 47	$ 0	47
Issuance of common stock in conjunction with exercise of stock options, shares	6	6
Issuance of common stock from ESPP purchase	$ 303		303
Issuance of common stock from ESPP purchase, shares		35
Stock-based compensation	7,353		7,353
Reclassification of other-than-temporary loss on available-for-sale securities included in net income	0
Ending balance at Dec. 31, 2016	$ 120,756	$ 25	$ 565,954	$ 0	$ (445,223)
Ending balance, shares at Dec. 31, 2016		24,813