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, 2012	$ 14,473	$ 13	$ 343,851	$ 0	$ (329,391)
Beginning balance, shares at Dec. 31, 2012		12,602
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(80,856)				(80,856)
Issuance of common stock, net of issuance costs	64,471	$ 3	64,468
Issuance of common stock, net of issuance costs, shares		3,833
Issuance of common stock from offering, net of issuance costs	10,834	$ 1	10,833
Issuance of common stock from offering, net of issuance costs, shares		844
Issuance of common stock in conjunction with exercise of stock options	574		574
Issuance of common stock in conjunction with exercise of stock options, shares		36
Issuance of common stock from ESPP purchase	385		385
Issuance of common stock from ESPP purchase, shares		38
Issuance of common stock in conjunction with exercise of warrants	338		338
Issuance of common stock in conjunction with the exercise of warrants, shares		12
Stock-based compensation	8,006		8,006
Stock-based compensation, restructuring	201		201
Reclassification of other-than-temporary loss on available-for-sale securities included in net income (loss)	0
Ending balance at Dec. 31, 2013	18,426	$ 17	428,656	0	(410,247)
Ending balance, shares at Dec. 31, 2013		17,365
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	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 conjunction 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 conjunction with acquisition	15,237	$ 2	15,235
Issuance of common stock in conjunction with acquisition, shares		1,499
Issuance of common stock warrants in conjunction 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 (loss)	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 income (loss)	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	96
Issuance of common stock from ESPP purchase	$ 203		203
Issuance of common stock from ESPP purchase, shares		26
Issuance of common stock in conjunction 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 (loss)	(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