Consolidated Statements of Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Total	Vesting of Warrants	Termination of ADM Operating Agreement	Common Stock	Additional Paid-In Capital	Additional Paid-In Capital Vesting of Warrants	Additional Paid-In Capital Termination of ADM Operating Agreement	Accumulated Other Comprehensive Loss	Accumulated Deficit
Common stock, shares outstanding, beginning (in shares) at Dec. 31, 2013				68,745,000
Beginning Balance at Dec. 31, 2013	$ 138,948			$ 69	$ 448,990			$ (3,794)	$ (306,317)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock plans, net of shares used for tax withholdings (in shares)				1,367,000
Issuance of common stock under stock plans, net of shares used for tax withholdings	8,880			$ 1	8,879
Common stock issued pursuant to vesting of restricted stock and restricted stock units (in shares)				783,000
Common stock issued pursuant to vesting of restricted stock and restricted stock units	8,518			$ 1	8,517
Stock-based compensation expense	$ 17,032				17,032
Issuance of common stock	5,750,000			5,750,000
Issuance of common stock	$ 59,209			$ 6	59,203
Common stock issued upon early conversion of senior convertible notes (in shares)				2,743,000
Common stock issued upon early conversion of Senior Convertible Notes	22,594			$ 2	22,592
Vesting of warrants	556					$ 556
Common stock issued pursuant to ADM termination agreement	0
Change in unrealized gain/loss on available-for-sale securities	(312)							(312)
Foreign currency translation adjustment	(6,908)							(6,908)
Net loss	$ (162,141)								(162,141)
Common stock, shares outstanding, beginning (in shares) at Dec. 31, 2014	79,388,000
Ending Balance at Dec. 31, 2014	$ 86,376			$ 79	565,769			(11,014)	(468,458)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock plans, net of shares used for tax withholdings (in shares)				416,000
Issuance of common stock under stock plans, net of shares used for tax withholdings	837			$ 1	836
Common stock issued pursuant to vesting of restricted stock and restricted stock units (in shares)				808,000
Common stock issued pursuant to vesting of restricted stock and restricted stock units	5,633			$ 1	5,632
Stock-based compensation expense	10,052				10,052
Vesting of warrants		$ 97	$ 242			$ 97	$ 242
Common stock issued pursuant to ADM termination agreement (in shares)				1,122,000
Common stock issued pursuant to ADM termination agreement	3,052			$ 1	3,051
Change in unrealized gain/loss on available-for-sale securities	228							228
Foreign currency translation adjustment	(11,545)							(11,545)
Net loss	$ (141,447)								(141,447)
Common stock, shares outstanding, beginning (in shares) at Dec. 31, 2015	81,734,000			81,734,000
Ending Balance at Dec. 31, 2015	$ (46,475)			$ 82	585,679			(22,331)	(609,905)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under stock plans, net of shares used for tax withholdings (in shares)				537,000
Issuance of common stock under stock plans, net of shares used for tax withholdings	895			$ 1	894
Common stock issued pursuant to vesting of restricted stock and restricted stock units (in shares)				682,000
Common stock issued pursuant to vesting of restricted stock and restricted stock units	0			$ 1	(1)
Stock-based compensation expense	$ 11,912				11,912
Issuance of common stock	3,171,000,000			3,171,000
Issuance of common stock	$ 4,775			$ 1	4,774
Issuance of common stock options for offering costs	335				335
Conversion of preferred stock to common stock (in shares)				550,000
Conversion of preferred stock to common stock	1,056			$ 1	1,055
Shares issued pursuant to consulting agreement (in shares)				111,000
Shares issued pursuant to consulting agreement	183			$ 0	183
Common stock issued upon early conversion of senior convertible notes (in shares)				9,023,000
Common stock issued upon early conversion of Senior Convertible Notes	39,900			$ 9	39,891
Common stock issued pursuant to ADM termination agreement (in shares)				628,000
Common stock issued pursuant to ADM termination agreement	1,206			$ 1	1,205
Change in unrealized gain/loss on available-for-sale securities	(2)							(2)
Foreign currency translation adjustment	5,525							5,525
Net loss	$ (101,556)								(101,556)
Common stock, shares outstanding, beginning (in shares) at Dec. 31, 2016	96,436,000			96,436,000
Ending Balance at Dec. 31, 2016	$ (82,246)			$ 96	$ 645,927			$ (16,808)	$ (711,461)