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Debt - Convertible Senior Note (Details) - USD ($)
$ in Thousands
Mar. 31, 2017
Dec. 31, 2016
Debt Instrument [Line Items]    
Principal amount of long-term debt $ 386,449 $ 400,420
5% Convertible Senior Notes due 2021    
Debt Instrument [Line Items]    
Principal amount of long-term debt 115,000 115,000
Convertible Debt | 5% Convertible Senior Notes due 2021    
Debt Instrument [Line Items]    
Unamortized discount (premium) and debt issuance costs, net 22,900  
Reported Value Measurement | 5% Convertible Senior Notes due 2021    
Debt Instrument [Line Items]    
Long-term debt, fair value $ 92,101 $ 91,029