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Stockholders' Equity - Common Stock and Warrants (Details) - USD ($)
$ / shares in Units, $ in Thousands
 1 Months Ended 3 Months Ended
Mar. 15, 2018
Feb. 16, 2018
Feb. 15, 2018
Apr. 30, 2018
Mar. 31, 2018
Mar. 31, 2017
Dec. 31, 2017
Convertible Debt              
Price per share of common stock issued (in dollars per share)       $ 7.98      
Maximum number of additional shares granted to underwriters   2,903,225          
Net proceeds from the issuance of common stock after deducting underwriting discounts, commissions and offering expenses         $ 294,584    
Common stock, par value (in dollars per share)         $ 0.01   $ 0.01
Options exercised (in shares)       453,214      
Proceeds from exercise of stock options       $ 3,600 $ 3,978 $ 265  
Common Stock              
Convertible Debt              
Number of common stock shares issued in underwriting agreement 885,000   19,354,839   20,239,839    
Price per share of common stock issued (in dollars per share) $ 15.50   $ 15.50        
Gross proceeds from issue of common stock     $ 300,000        
Net proceeds from the issuance of common stock after deducting underwriting discounts, commissions and offering expenses $ 294,600       $ 294,600    
Over-allotment Option | Common Stock              
Convertible Debt              
Number of days in option period granted to underwriters     30 days        
Maximum number of additional shares granted to underwriters     2,903,225