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Equity and Partners' Capital - Additional Information (details) (USD $)
In Millions, except Share data, unless otherwise specified
 3 Months Ended 1 Months Ended
Mar. 31, 2015
Jul. 31, 2014
Nov. 30, 2014
Dec. 31, 2014
Schedule of Investments [Line Items]        
Limited partner units owned 218,909,977us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding     218,909,977us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding
Anadarko [Member]        
Schedule of Investments [Line Items]        
Limited partner units owned 193,387,365us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding
/ us-gaap_OtherOwnershipInterestsByNameAxis
= wgp_AnadarkoMember		      
Ownership interest 88.30%us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest
/ us-gaap_OtherOwnershipInterestsByNameAxis
= wgp_AnadarkoMember		      
Anadarko [Member] | Common Units [Member]        
Schedule of Investments [Line Items]        
Common units issued   5,750,000us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering
/ us-gaap_CapitalUnitsByClassAxis
= wgp_CommonUnitsMember
/ us-gaap_OtherOwnershipInterestsByNameAxis
= wgp_AnadarkoMember		    
Anadarko [Member] | Option on Securities [Member] | Common Units [Member]        
Schedule of Investments [Line Items]        
Common units issued   750,000us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering
/ us-gaap_CapitalUnitsByClassAxis
= wgp_CommonUnitsMember
/ us-gaap_OptionIndexedToIssuersEquityEquityAxis
= us-gaap_OptionOnSecuritiesMember
/ us-gaap_OtherOwnershipInterestsByNameAxis
= wgp_AnadarkoMember		    
Public [Member]        
Schedule of Investments [Line Items]        
Limited partner units owned 25,522,612us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding
/ us-gaap_OtherOwnershipInterestsByNameAxis
= wgp_PublicMember		      
Ownership interest 11.70%us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest
/ us-gaap_OtherOwnershipInterestsByNameAxis
= wgp_PublicMember		      
Western Gas Partners [Member]        
Schedule of Investments [Line Items]        
General partner units owned 2,583,068us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember		      
General partner's interest 1.80%us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember		   2.00%us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember		  
Units issued 45,711us-gaap_PartnersCapitalAccountUnitsSoldInPrivatePlacement
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember		      
Price per unit     $ 70.85us-gaap_SharesIssuedPricePerShare
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember		 [1]  
Western Gas Partners [Member] | Common Units [Member]        
Schedule of Investments [Line Items]        
Limited partner units owned 49,296,205us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding
/ us-gaap_CapitalUnitsByClassAxis
= wgp_CommonUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember		      
Ownership interest 34.80%us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest
/ us-gaap_CapitalUnitsByClassAxis
= wgp_CommonUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember		      
Common units issued     8,620,153us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering
/ us-gaap_CapitalUnitsByClassAxis
= wgp_CommonUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember		 [1]  
Western Gas Partners [Member] | Incentive Distribution Rights [Member]        
Schedule of Investments [Line Items]        
General partner's interest 100.00%us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest
/ us-gaap_CapitalUnitsByClassAxis
= wgp_IncentiveDistributionRightsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember		      
Western Gas Partners [Member] | Class C Units [Member]        
Schedule of Investments [Line Items]        
Units issued 45,711us-gaap_PartnersCapitalAccountUnitsSoldInPrivatePlacement
/ us-gaap_CapitalUnitsByClassAxis
= wgp_ClassCUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember		      
Price per unit     $ 68.72us-gaap_SharesIssuedPricePerShare
/ us-gaap_CapitalUnitsByClassAxis
= wgp_ClassCUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember		  
Proceeds from the issuance of WES Class C units     $ 750.0us-gaap_ProceedsFromIssuanceOfPrivatePlacement
/ us-gaap_CapitalUnitsByClassAxis
= wgp_ClassCUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember		  
Western Gas Partners [Member] | Class C Units [Member] | Maximum [Member]        
Schedule of Investments [Line Items]        
Redeemable option on units     $ 150.0wgp_RedeemableOptionOnUnits
/ us-gaap_CapitalUnitsByClassAxis
= wgp_ClassCUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		  
Western Gas Partners [Member] | Option on Securities [Member] | Common Units [Member]        
Schedule of Investments [Line Items]        
Common units issued     1,120,153us-gaap_PartnersCapitalAccountUnitsSoldInPublicOffering
/ us-gaap_CapitalUnitsByClassAxis
= wgp_CommonUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember
/ us-gaap_OptionIndexedToIssuersEquityEquityAxis
= us-gaap_OptionOnSecuritiesMember		  
Western Gas Partners [Member] | Public [Member] | Common Units [Member]        
Schedule of Investments [Line Items]        
Limited partner units owned 78,123,429us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding
/ us-gaap_CapitalUnitsByClassAxis
= wgp_CommonUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember
/ us-gaap_OtherOwnershipInterestsByNameAxis
= wgp_PublicMember		      
Ownership interest 55.10%us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest
/ us-gaap_CapitalUnitsByClassAxis
= wgp_CommonUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember
/ us-gaap_OtherOwnershipInterestsByNameAxis
= wgp_PublicMember		      
Western Gas Partners [Member] | Other Subsidiaries Of Anadarko [Member]        
Schedule of Investments [Line Items]        
Ownership interest 8.30%us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPMembersOrLimitedPartnersOwnershipInterest
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember
/ us-gaap_OtherOwnershipInterestsByNameAxis
= wgp_OtherSubsidiariesOfAnadarkoMember		      
Western Gas Partners [Member] | Other Subsidiaries Of Anadarko [Member] | Common Units [Member]        
Schedule of Investments [Line Items]        
Limited partner units owned 757,619us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding
/ us-gaap_CapitalUnitsByClassAxis
= wgp_CommonUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember
/ us-gaap_OtherOwnershipInterestsByNameAxis
= wgp_OtherSubsidiariesOfAnadarkoMember		      
Western Gas Partners [Member] | Other Subsidiaries Of Anadarko [Member] | Class C Units [Member]        
Schedule of Investments [Line Items]        
Limited partner units owned 10,959,564us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding
/ us-gaap_CapitalUnitsByClassAxis
= wgp_ClassCUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember
/ us-gaap_OtherOwnershipInterestsByNameAxis
= wgp_OtherSubsidiariesOfAnadarkoMember		      
Units issued     10,913,853us-gaap_PartnersCapitalAccountUnitsSoldInPrivatePlacement
/ us-gaap_CapitalUnitsByClassAxis
= wgp_ClassCUnitsMember
/ dei_LegalEntityAxis
= wgp_WesternGasPartnersMember
/ us-gaap_OtherOwnershipInterestsByNameAxis
= wgp_OtherSubsidiariesOfAnadarkoMember		  
[1] Includes the issuance of 1,120,153 WES common units pursuant to the partial exercise of the underwriters’ over-allotment option, the net proceeds from which were $77.0 million. Beginning with this partial exercise, WES GP elected not to make a corresponding capital contribution to maintain its 2.0% interest in WES.