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Long-Term Debt - Convertible Senior Notes Due 2023 (Details)
$ / shares in Units, $ in Thousands
3 Months Ended
Mar. 20, 2018
USD ($)
$ / shares
Mar. 31, 2020
USD ($)
Mar. 31, 2019
USD ($)
Dec. 31, 2019
USD ($)
Debt Instrument [Line Items]        
Principal amount   $ 422,786    
Unamortized debt discount   20,907    
Interest expense   7,394 $ 7,896  
Convertible Senior Notes Maturing September 2023        
Debt Instrument [Line Items]        
Principal amount $ 125,000 125,000   $ 125,000
Interest rate (as a percent) 4.125%      
Frequency of periodic payment semi-annually      
Maturity date Sep. 15, 2023      
Initial conversion ratio 0.1056133      
Initial conversion price per share (in dollars per share) | $ / shares $ 9.47      
Redemption price as a percentage of principal amount 100.00%      
Minimum percentage in aggregate principal amount 25.00%      
Unamortized debt discount $ 20,100 13,700   $ 14,500
Carrying amount of equity component $ 15,900      
Effective interest rate (as a percent) 7.80%      
Interest expense   $ 2,100 $ 2,100