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Basis of Presentation (Details)
 3 Months Ended
Mar. 31, 2015
Partnership Ownership Disclosure [Abstract]  
General partner ownership interest (in hundredths) 2.00%us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest
Parent's percentage ownership in the general partner of the Partnership 100.00%trgp_GeneralPartnerOwnershipInterestByParent
Number of Partnership common units owned (in units) 16,309,594trgp_NumberOfPartnershipCommonUnitsOwned
Limited Partner [Member]  
Partnership Ownership Disclosure [Abstract]  
General partner ownership interest (in hundredths) 9.10%us-gaap_LimitedLiabilityCompanyLLCOrLimitedPartnershipLPManagingMemberOrGeneralPartnerOwnershipInterest
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= us-gaap_LimitedPartnerMember