Debt - Convertible Notes (Details)
1 Months Ended 3 Months Ended 9 Months Ended
May 31, 2014
USD ($)
Sep. 30, 2020
USD ($)
Sep. 30, 2019
USD ($)
Sep. 30, 2020
USD ($)
$ / shares
Sep. 30, 2019
USD ($)
Dec. 31, 2019
USD ($)
Debt Instrument [Line Items]            
Repurchased of convertible notes       $ 154,574,000 $ 402,500,000  
Loss on debt extinguishment   $ 7,252,000 $ 5,580,000 7,252,000 $ 11,473,000  
Unamortized deferred financing costs   $ 19,464,000   $ 19,464,000   $ 17,549,000
Convertible Senior Notes            
Debt Instrument [Line Items]            
Stated interest rate   3.75%   3.75%    
Unamortized deferred financing costs   $ 500,000   $ 500,000   2,100,000
Equity component of the conversion feature   55,100,000   $ 55,100,000   55,100,000
Convertible Senior Notes | Convertible Senior Notes Due 2019            
Debt Instrument [Line Items]            
Aggregate principal amount of debt $ 402,500,000          
Stated interest rate 2.875%          
Debt instrument, maturity date May 15, 2019          
Convertible Senior Notes | Convertible Senior Notes Due 2021            
Debt Instrument [Line Items]            
Aggregate principal amount of debt $ 345,000,000.0          
Stated interest rate 3.75%          
Debt instrument, maturity date May 15, 2021          
Debt conversion ratio       17.4458    
Anti-dilutive cash dividends, exceeding (in USD per share) | $ / shares       $ 0.73026    
Repurchased of convertible notes   154,600,000        
Loss on debt extinguishment   6,200,000   $ 6,200,000    
Unamortized discount   $ 1,700,000   $ 1,700,000   $ 6,500,000