Name:	pagp_CapitalContributionsToEquityMethodInvesteesExcludingCapitalizedInterest
Namespace Prefix:	pagp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of gain (loss) (i) from remeasurement to fair value of retained investment in former subsidiary and group of assets constituting business activity deconsolidated and derecognized and/or (ii) associated with the difference between the fair value and historical book value of assets contributed in exchange for an additional interest in an equity method investee.

No definition available.

Name:	pagp_GainsLossesOnInvestmentsInUnconsolidatedEntitiesNet
Namespace Prefix:	pagp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Number of Pipelines or Partial Pipelines Contributed

No definition available.

Name:	pagp_NumberOfPipelinesOrPartialPipelinesContributed
Namespace Prefix:	pagp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Percentage of voting equity interests acquired at the acquisition date in the business combination.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-2

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Percentage of equity in the acquiree held by the acquirer immediately before the acquisition date in a business combination.

No definition available.

Name:	us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Difference between amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and amount of underlying equity in net assets the reporting Entity has in the investee.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Name:	us-gaap_EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Name:	us-gaap_ScheduleOfEquityMethodInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=pagp_WinktoWebsterPipelineLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=pagp_SaddlehornPipelineCompanyLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=pagp_OMOGJVLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_NoncashOrPartNoncashAcquisitionsByUniqueDescriptionAxis=pagp_AcquisitionOfAdditionalInterestInExchangeForContributionOfPipelineAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=pagp_AdvantagePipelineHoldingsLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_BusinessAcquisitionAxis=pagp_MidwayPipelineLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_BusinessAcquisitionAxis=pagp_OMOGJVLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_BusinessAcquisitionAxis=pagp_AdvantagePipelineHoldingsLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: