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Noncontrolling Interests (Detail) - USD ($)
shares in Thousands, $ in Millions
1 Months Ended 3 Months Ended 12 Months Ended
Apr. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Western Gas Equity Partners, LP [Member] | Limited Partner [Member]      
Noncontrolling Interest [Line Items]      
Ownership interest in subsidiary   87.30%  
Public ownership interest in subsidiary   12.70%  
Western Gas Partners, LP [Member]      
Noncontrolling Interest [Line Items]      
Units issued in private placement   1,300  
Common units issued to the public     874
Net proceeds from common units     $ 57
Western Gas Partners, LP [Member] | Series A Preferred Units [Member]      
Noncontrolling Interest [Line Items]      
Units issued in private placement   14,000  
Net proceeds from Series A preferred units   $ 440  
Western Gas Partners, LP [Member] | Series A Preferred Units [Member] | Subsequent Event [Member]      
Noncontrolling Interest [Line Items]      
Units issued in private placement 8,000    
Net proceeds from Series A preferred units $ 248    
Western Gas Partners, LP [Member] | Class C Units [Member]      
Noncontrolling Interest [Line Items]      
Units issued in private placement   324 498
Western Gas Partners, LP [Member] | Limited Partner [Member]      
Noncontrolling Interest [Line Items]      
Public ownership interest in subsidiary   58.20%  
Western Gas Partners, LP [Member] | Limited Partner [Member] | Western Gas Equity Partners, LP, Ownership Interest [Member]      
Noncontrolling Interest [Line Items]      
Ownership interest in subsidiary   31.50%  
Western Gas Partners, LP [Member] | Limited Partner [Member] | Other Anadarko Subsidiaries, Ownership Interest [Member]      
Noncontrolling Interest [Line Items]      
Ownership interest in subsidiary   8.70%  
Western Gas Partners, LP [Member] | General Partner [Member] | Western Gas Equity Partners, LP, Ownership Interest [Member]      
Noncontrolling Interest [Line Items]      
Ownership interest in subsidiary   1.60%