Quarterly report pursuant to Section 13 or 15(d)

Borrowings (Credit Facility) (Narrative) (Details)

v3.19.1
Borrowings (Credit Facility) (Narrative) (Details)
3 Months Ended
Mar. 31, 2019
USD ($)
May 01, 2019
USD ($)
Dec. 31, 2018
USD ($)
Sep. 27, 2018
USD ($)
Apr. 05, 2018
USD ($)
May 25, 2017
USD ($)
lender
Line of Credit Facility [Line Items]            
Balance outstanding on credit facility $ 330,000,000   $ 200,000,000      
Senior secured revolving credit facility | Secured debt            
Line of Credit Facility [Line Items]            
Institutional lenders | lender           17
Maximum borrowing capacity           $ 2,000,000,000
Credit facility borrowing base 1,100,000,000     $ 1,100,000,000 $ 825,000,000  
Increase limit 850,000,000     $ 850,000,000 $ 650,000,000  
Balance outstanding on credit facility 330,000,000          
Letters of credit outstanding $ 17,675,000          
Interest rate at period end (as a percent) 4.00%          
Unused capacity, commitment fee (as a percent) 0.375%          
Senior secured revolving credit facility | Secured debt | Subsequent Event            
Line of Credit Facility [Line Items]            
Credit facility borrowing base   $ 1,100,000        
Senior secured revolving credit facility | Secured debt | Minimum            
Line of Credit Facility [Line Items]            
Debt instrument interest rate (as a percent) 1.25%          
Senior secured revolving credit facility | Secured debt | Maximum            
Line of Credit Facility [Line Items]            
Debt instrument interest rate (as a percent) 2.25%