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Acquisitions (Details)
$ in Millions
1 Months Ended 3 Months Ended 12 Months Ended
Jun. 30, 2015
USD ($)
May 31, 2015
USD ($)
Sep. 30, 2015
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Equity Method Investments and Joint Ventures [Abstract]            
Payments to Acquire Equity Method Investments       $ 132 $ 177 $ 595
Utica East Ohio Midstream, LLC [Member]            
Equity Method Investments and Joint Ventures [Abstract]            
Equity Method Investment, Ownership Percentage       62.00%    
Payments to Acquire Equity Method Investments       $ 0 $ 0 $ 357
Utica East Ohio Midstream, LLC [Member] | Williams Partners [Member]            
Equity Method Investments and Joint Ventures [Abstract]            
Equity Method Investment, Ownership Percentage       62.00%    
Payments to Acquire Equity Method Investments $ 357          
Reduction in incentive distribution rights payment $ 2          
Eagle Ford Gathering System [Member]            
Business Acquisition, Purchase Price Allocation [Abstract]            
Other intangible assets   $ 32        
Eagle Ford Gathering System [Member] | Williams Partners [Member]            
Business Acquisition [Line Items]            
Number Of Miles Of Pipeline Acquired   140        
Payments to Acquire Businesses, Gross   $ 112        
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Property, Plant, and Equipment     $ 20      
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Intangibles     $ (20)      
Business Acquisition, Purchase Price Allocation [Abstract]            
Property, plant, and equipment   $ 80        
Additional Investment [Member] | Utica East Ohio Midstream, LLC [Member]            
Equity Method Investments and Joint Ventures [Abstract]            
Equity Method Investment, Ownership Percentage 13.00%