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Net Loss Per Share (Details) - USD ($)	3 Months Ended
Net Loss Per Share (Details) - USD ($)	Mar. 31, 2018	Mar. 31, 2017	Apr. 03, 2017	Nov. 30, 2015	Nov. 02, 2015	Dec. 10, 2013
Earnings Per Share, Basic and Diluted [Abstract]
Net loss	$ (19,767,000)	$ (21,314,000)
Shares used in computing basic and diluted net loss per share (in shares)	83,706,000	82,928,000
Basic and diluted net loss per share (in dollars per share)	$ (0.24)	$ (0.26)
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Outstanding securities used in calculations (in shares)	695,000	1,068,000
Potential Dilutive Effect of Securities [Abstract]
Conversion of the Notes (in shares)	11,939,000	14,767,000
Conversion of Deerfield Warrants (in shares)	6,470,000	0
Facility Agreement \| Deerfield Warrants \| Common Stock
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Warrants issued (in shares)			6,470,000
Exercise price of warrants issued (in dollars per share)			$ 9.23
Convertible Debt \| 2.25% Convertible Senior Notes
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Convertible notes	$ 17,600,000					$ 86,300,000
Stated interest rate	2.25%					2.25%
Debt instrument face amount						$ 86,250,000
Convertible Debt \| 3.25% Convertible Senior Notes
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Convertible notes	$ 109,400,000			$ 125,000,000
Stated interest rate					3.25%
Debt instrument face amount					$ 125,000,000.0
Secured Debt \| Facility Agreement
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Stated interest rate	6.87%
Debt instrument face amount			$ 120,000,000.0
Common stock options
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Outstanding securities used in calculations (in shares)	270,000	696,000
Restricted stock awards
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Outstanding securities used in calculations (in shares)	118,000	120,000
Restricted stock units
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Outstanding securities used in calculations (in shares)	307,000	252,000