Net Loss Per Share (Details) - USD ($)		3 Months Ended		9 Months Ended
	Aug. 09, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Apr. 03, 2017	Nov. 30, 2015	Nov. 02, 2015	Dec. 10, 2013
Earnings Per Share, Basic and Diluted [Abstract]
Net loss		$ (10,116,000)	$ (14,273,000)	$ (53,759,000)	$ (51,879,000)
Shares used in computing basic and diluted net loss per share (in shares)		85,226,000	83,496,000	84,487,000	83,225,000
Basic and diluted net loss per share (in dollars per share)		$ (0.12)	$ (0.17)	$ (0.64)	$ (0.62)
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Outstanding securities used in calculations (in shares)		348,000	553,000	646,000	867,000
Potential Dilutive Effect of Securities [Abstract]
Conversion of the Notes (in shares)		8,317,000	11,939,000	8,317,000	11,939,000
Deerfield Warrants
Potential Dilutive Effect of Securities [Abstract]
Conversion of Deerfield Warrants (in shares)		6,470,000	6,470,000	6,470,000	6,470,000
New Deerfield Warrants
Potential Dilutive Effect of Securities [Abstract]
Conversion of Deerfield Warrants (in shares)			0	8,750,000	0
New Deerfield Warrants | Common Stock
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Exercise price of warrants issued (in dollars per share)	$ 4.71
3.25% Convertible Senior Notes
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Stated interest rate		3.25%		3.25%
Debt instrument face amount		$ 40,500,000		$ 40,500,000
3.25% Convertible Senior Notes | Deerfield Warrants
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Stated interest rate	3.25%
Repayments of debt	$ 40,500,000
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
Facility Agreement | New Deerfield Warrants | Common Stock
Securities Excluded from Calculations of Earnings Per Share Because Impact Would Have Been Anti-Dilutive [Abstract]
Debt instrument face amount	$ 40,500,000.0
Potential Dilutive Effect of Securities [Abstract]
Conversion of Deerfield Warrants (in shares)		8,750,001
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		$ 18,100,000		$ 18,100,000					$ 86,300,000
Stated interest rate		2.25%		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		$ 75,800,000		$ 75,800,000			$ 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%		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)		80,000	338,000	181,000	543,000
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)		120,000	117,000	121,000	119,000
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)		148,000	98,000	344,000	205,000