Quarterly report pursuant to Section 13 or 15(d)

Borrowings (Credit Facility) (Narrative) (Details)

v3.10.0.1
Borrowings (Credit Facility) (Narrative) (Details)
6 Months Ended
Apr. 05, 2018
USD ($)
May 25, 2017
USD ($)
lender
Jun. 30, 2018
USD ($)
Dec. 31, 2017
USD ($)
Line of Credit Facility [Line Items]        
Balance outstanding on credit facility     $ 0 $ 25,000,000
Senior secured revolving credit facility | Secured debt        
Line of Credit Facility [Line Items]        
Debt instrument maturity date   May 25, 2022    
Institutional lenders | lender   17    
Maximum borrowing capacity   $ 2,000,000,000    
Increase limit $ 825,000,000   825,000,000  
Credit facility borrowing base $ 650,000,000   650,000,000  
Balance outstanding on credit facility     0  
Letters of credit outstanding     $ 1,250,000  
Interest rate at period end (as a percent)     3.97%  
Unused capacity, commitment fee (as a percent)     0.375%  
Senior secured revolving credit facility | Secured debt | Minimum        
Line of Credit Facility [Line Items]        
Debt instrument interest rate (as a percent) 1.25%   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%   2.25%