XML 58 R38.htm IDEA: XBRL DOCUMENT v3.20.1
Long-term debt - Narrative (Details) - USD ($)
Feb. 11, 2020
Mar. 31, 2020
Jan. 09, 2020
Debt Instrument [Line Items]      
Early redemption fees $ 13,800,000    
Write off of unamortized financing fees and discounts 7,900,000    
Senior Notes Bearing Interest at 4.625 Percent Due March 2028      
Debt Instrument [Line Items]      
Stated interest rate (as a percent)     4.625%
Senior Notes Bearing Interest at 4.625 Percent Due March 2028 | Senior Notes      
Debt Instrument [Line Items]      
Principal amount of unsecured notes $ 1,000,000,000.0   $ 1,000,000,000.0
Unsecured notes bearing fixed rate interest at 5.125% due July 2020      
Debt Instrument [Line Items]      
Stated interest rate (as a percent) 5.125% 5.125%  
Repayments of unsecured debt $ 310,000,000.0    
Unsecured notes bearing fixed rate interest at 6.375% due October 2023      
Debt Instrument [Line Items]      
Stated interest rate (as a percent) 6.375% 6.375%  
Repayments of unsecured debt $ 650,000,000.0    
Amended and Restated Competitive Advance and Revolving Credit Agreement | Line of Credit | Revolving Credit Facility      
Debt Instrument [Line Items]      
Unused borrowing capacity   $ 720,800,000  
Maximum borrowing capacity under credit facility   $ 1,510,000,000