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Debt - Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended
Jan. 31, 2017
Mar. 31, 2017
Dec. 31, 2016
Five-Year Credit Facility [Member]      
Debt Instrument [Line Items]      
Line of credit, maximum capacity   $ 3,000,000,000  
Debt instrument, term   5 years  
Line of credit, expiration date   Jan. 23, 2021  
Line of credit, outstanding borrowings   $ 0  
364-Day Credit Facility Due 2017 [Member]      
Debt Instrument [Line Items]      
Line of credit, maximum capacity   $ 2,000,000,000  
Debt instrument, term   364 days  
Line of credit, expiration date Jan. 12, 2018    
Line of credit, outstanding borrowings   $ 0  
Commercial Paper [Member]      
Debt Instrument [Line Items]      
Line of credit, maximum capacity   3,000,000,000  
Commercial paper, outstanding borrowings   $ 0  
Commercial Paper [Member] | Maximum [Member]      
Debt Instrument [Line Items]      
Debt instrument, term   397 days  
WES RCF [Member]      
Debt Instrument [Line Items]      
Line of credit, maximum capacity   $ 1,200,000,000  
Debt instrument, term   5 years  
Line of credit, expiration date   Feb. 26, 2020  
Line of credit, outstanding borrowings   $ 0  
Line of credit, available borrowing capacity   1,195,000,000  
Line of credit, expandable maximum capacity   1,500,000,000  
Letters of credit, outstanding   5,000,000  
WGP RCF [Member]      
Debt Instrument [Line Items]      
Line of credit, maximum capacity   $ 250,000,000  
Debt instrument, term   3 years  
Line of credit, expiration date   Mar. 14, 2019  
Line of credit, outstanding borrowings   $ 28,000,000  
Line of credit, available borrowing capacity   222,000,000  
Line of credit, expandable maximum capacity   $ 500,000,000  
Line of credit, interest rate   2.99%  
Fair Value, Inputs, Level 2 [Member] | Market Approach Valuation Technique [Member]      
Debt Instrument [Line Items]      
Estimated fair value of total borrowings   $ 17,000,000,000 $ 17,100,000,000
Zero-Coupon Senior Notes [Member]      
Debt Instrument [Line Items]      
Debt Instrument, earliest call date   Oct. 10, 2017  
Zero-Coupon Senior Notes [Member] | Accreted Value at Next Potential Put Date [Member]      
Debt Instrument [Line Items]      
Debt instrument, accreted value   $ 883,000,000