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Debt - Senior Secured Credit Facility (Details) - Secured debt - USD ($)
Mar. 31, 2020
Dec. 31, 2019
Senior Secured Credit Facility    
Debt Instrument [Line Items]    
Maximum borrowing capacity $ 2,000,000,000.0  
Current borrowing capacity 950,000,000.0  
Amount outstanding $ 275,000,000.0  
Credit facility, interest rate at period end (as a percent) 2.43%  
Line of Credit Facility, Borrowing Base and Aggregate Elected Commitment $ 950,000,000  
Letter of Credit    
Debt Instrument [Line Items]    
Maximum borrowing capacity 80,000,000.0  
Letters of credit outstanding $ 14,700,000 $ 14,700,000