Consolidated Statement of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2011	$ 9,312	$ 65	$ 291,252	$ (282,005)
Beginning balance, shares at Dec. 31, 2011		65,369,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(47,386)			(47,386)
Issuance of common stock, net of issuance costs	45,809	35	45,774
Issuance of common stock, net of issuance costs, shares		35,058,000
Issuance of common stock in conjunction with exercise of stock options	33		33
Issuance of common stock in conjunction with exercise of stock options, shares		18,000
Issuance of common stock from ESPP purchase	548	1	547
Issuance of common stock from ESPP purchase, shares		364,000
Stock-based compensation	6,157		6,157
Ending balance at Dec. 31, 2012	14,473	101	343,763	(329,391)
Ending balance, shares at Dec. 31, 2012		100,809,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(80,856)			(80,856)
Issuance of common stock, net of issuance costs	64,471	31	64,440
Issuance of common stock, net of issuance costs, shares		30,667,000
Issuance of common stock from initial public offering, net of issuance costs of $371	10,834	7	10,827
Issuance of common stock from initial public offering, net of issuance costs of $371, shares		6,753,000
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		291,000
Issuance of common stock from ESPP purchase	385		385
Issuance of common stock from ESPP purchase, shares		304,000
Issuance of common stock in conjunction with exercise of warrants	338		338
Issuance of common stock in conjunction with the exercise of warrants, shares		103,000
Stock-based compensation	8,006		8,006
Stock-based compensation, restructuring	201		201
Ending balance at Dec. 31, 2013	18,426	139	428,534	(410,247)
Ending balance, shares at Dec. 31, 2013		138,927,000
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	150,000	152,000
Issuance of common stock from ESPP purchase	556	1	555
Issuance of common stock from ESPP purchase, shares		504,000
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		465,000
Issuance of common stock in conjunction with vesting of restricted stock units	1	1
Issuance of common stock in conjunction with vesting of restricted stock units, shares		1,321,000
Issuance of common stock in conjunction with acquisition	15,237	12	15,225
Issuance of common stock in conjunction with acquisition, shares		11,995,000
Issuance of common stock warrants in conjunction with debt	558		558
Stock-based compensation	9,492		9,492
Ending balance at Dec. 31, 2014	$ 55,279	$ 153	$ 456,786	$ (401,660)
Ending balance, shares at Dec. 31, 2014		153,364,000