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Stockholders' Equity - Narrative (Details) - USD ($)
 1 Months Ended 3 Months Ended
May 31, 2018
Mar. 31, 2020
Jan. 01, 2020
May 13, 2016
2016 Incentive Plan        
Class of Stock [Line Items]        
Number of shares authorized (in shares)   18,000,000   18,000,000
Number of potential shares authorized for issuance under share based compensation plan (in shares)       2,000,000
Increase in number of shares authorized (in shares)     2,000,000  
Number of shares available for grant (in shares)   7,536,221    
Number of shares of unvested restricted stock units and options outstanding (in shares)   2,667,710    
Common stock, other shares, outstanding (in shares)   5,631,777    
Award vesting period   3 years    
Maximum contractual term   10 years    
2007 Incentive Plan        
Class of Stock [Line Items]        
Common stock, other shares, outstanding (in shares)   3,984,209    
Award vesting period   3 years    
Maximum contractual term   10 years    
Common stock | Sales Agreement        
Class of Stock [Line Items]        
Maximum authorized amount $ 100,000,000.0 $ 250,000,000.0    
Agent fee 3.00%      
Aggregate number of shares issued (in shares)   43,148,952    
Stock sale agreement weighted average price per share   $ 4.92    
Aggregate proceeds   $ 208,200,000    
Stock sales agreement, remaining authorized sales amount   $ 150,000,000