XML 46 R36.htm IDEA: XBRL DOCUMENT v3.10.0.1
Debt and Credit Agreements - Narrative (Details) - USD ($)
Sep. 30, 2018
Apr. 18, 2018
Dec. 31, 2017
Revolving credit facility      
Debt Instrument [Line Items]      
Borrowing base   $ 3,200,000,000.0  
Remaining borrowing capacity $ 1,800,000,000 $ 1,700,000,000  
Line of credit $ 0    
6.51% weighted-average senior notes      
Debt Instrument [Line Items]      
Weighted average interest rate 6.51%   6.51%