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Debt - Convertible Senior Note (Details) - USD ($)
$ in Thousands
Sep. 30, 2017
Dec. 31, 2016
Jul. 14, 2016
Debt Instrument [Line Items]      
Principal amount of long-term debt $ 353,457 $ 400,420  
Unamortized discount and deferred financing costs $ 23,256 30,024  
5.00% Convertible Senior Notes due 2021      
Debt Instrument [Line Items]      
Interest rate 5.00%   5.00%
5.00% Convertible Senior Notes due 2021 | Carrying Value      
Debt Instrument [Line Items]      
Long-term debt, fair value $ 94,328 91,029  
Convertible Debt | 5.00% Convertible Senior Notes due 2021      
Debt Instrument [Line Items]      
Interest rate 5.00%    
Principal amount of long-term debt $ 115,000 $ 115,000  
Unamortized discount and deferred financing costs $ 20,700