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Acquisitions and Divestitures - Additional Information (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Jun. 27, 2018
Jun. 01, 2018
Mar. 17, 2017
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Property, Plant and Equipment [Line Items]              
Acquisition, net investment           $ 161,858  
Affiliates [Member]              
Property, Plant and Equipment [Line Items]              
Cash payment           254 $ 3,910
Settlement of the Deferred purchase price obligation - Anadarko [1]           0 37,346
Deferred Purchase Price Obligation - Anadarko [Member] | Affiliates [Member]              
Property, Plant and Equipment [Line Items]              
Settlement of the Deferred purchase price obligation - Anadarko [2]       $ 0 $ 0 $ 0 37,346
Western Gas Partners, LP [Member] | Helper and Clawson Systems [Member]              
Property, Plant and Equipment [Line Items]              
Gain (loss) on sale of assets             16,300
Western Gas Partners, LP [Member] | Non-Operated Marcellus Interest [Member]              
Property, Plant and Equipment [Line Items]              
Percentage ownership interest     33.75%        
Western Gas Partners, LP [Member] | Whitethorn [Member]              
Property, Plant and Equipment [Line Items]              
Ownership percentage acquired   20.00%          
Acquisition, net investment   $ 150,600          
Western Gas Partners, LP [Member] | Cactus II [Member]              
Property, Plant and Equipment [Line Items]              
Ownership percentage acquired 15.00%            
Acquisition, net investment $ 11,300            
Western Gas Partners, LP [Member] | Delaware Basin JV Gathering LLC [Member]              
Property, Plant and Equipment [Line Items]              
Ownership percentage acquired     50.00%        
Percentage ownership interest     50.00%        
Cash payment     $ 155,000        
Net gain from property exchange             125,700
Western Gas Partners, LP [Member] | Delaware Basin JV Gathering LLC [Member] | Deferred Purchase Price Obligation - Anadarko [Member] | Affiliates [Member]              
Property, Plant and Equipment [Line Items]              
Settlement of the Deferred purchase price obligation - Anadarko             $ 37,346
[1] See Note 3.
[2] Represents the cash payment to Anadarko for the settlement of the Deferred purchase price obligation - Anadarko (see Note 3).