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Description of Business and Basis of Presentation - Assets and Investments Table (Details) - Western Gas Partners, LP [Member]
Sep. 30, 2017
unit
Owned and Operated [Member] | Gathering Systems [Member]  
Assets [Line Items]  
Assets, number of units 12
Owned and Operated [Member] | Treating Facilities [Member]  
Assets [Line Items]  
Assets, number of units 19
Owned and Operated [Member] | Natural Gas Processing Plants/Trains [Member]  
Assets [Line Items]  
Assets, number of units 19
Owned and Operated [Member] | Natural Gas Liquids Pipelines [Member]  
Assets [Line Items]  
Assets, number of units 2
Owned and Operated [Member] | Natural Gas Pipelines [Member]  
Assets [Line Items]  
Assets, number of units 5
Operated Interests [Member] | Gathering Systems [Member]  
Assets [Line Items]  
Assets, number of units 3
Operated Interests [Member] | Treating Facilities [Member]  
Assets [Line Items]  
Assets, number of units 3
Operated Interests [Member] | Natural Gas Processing Plants/Trains [Member]  
Assets [Line Items]  
Assets, number of units 5
Operated Interests [Member] | Oil Pipelines [Member]  
Assets [Line Items]  
Assets, number of units 1
Non-Operated Interests [Member] | Gathering Systems [Member]  
Assets [Line Items]  
Assets, number of units 3
Equity Interests [Member] | Gathering Systems [Member]  
Assets [Line Items]  
Assets, number of units 2
Equity Interests [Member] | Treating Facilities [Member]  
Assets [Line Items]  
Assets, number of units 3
Equity Interests [Member] | Natural Gas Processing Plants/Trains [Member]  
Assets [Line Items]  
Assets, number of units 2
Equity Interests [Member] | Natural Gas Liquids Pipelines [Member]  
Assets [Line Items]  
Assets, number of units 3
Equity Interests [Member] | Oil Pipelines [Member]  
Assets [Line Items]  
Assets, number of units 1