Quarterly report pursuant to Section 13 or 15(d)

Long-term Debt - Summary of Components of Notes (Details)

v3.20.1
Long-term Debt - Summary of Components of Notes (Details) - USD ($)
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Jul. 31, 2019
Senior Unsecured Notes        
Debt Instrument [Line Items]        
Principal     $ 150,000,000  
Senior Unsecured Notes | 2024 Notes        
Debt Instrument [Line Items]        
Principal $ 500,000,000 $ 500,000,000   $ 350,000,000
Accrued interest 6,000,000 13,000,000    
Unamortized premium 7,000,000 7,000,000    
Less: Unamortized financing costs (8,000,000) (8,000,000)    
Carrying value of convertible notes 505,000,000 512,000,000    
Convertible Senior Notes | 4.125% Convertible Senior Notes Due September 1, 2022        
Debt Instrument [Line Items]        
Principal 150,000,000 150,000,000    
Accrued interest 1,000,000 2,000,000    
Less: Unamortized financing costs (3,000,000) (3,000,000)    
Carrying value of convertible notes $ 148,000,000 $ 149,000,000