Name:	amgp_IncentiveDistributionDistributionPercentage
Namespace Prefix:	amgp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents minimum annual distribution as per partnership agreement.

No definition available.

Name:	amgp_LimitedPartnerMinimumAnnualDistributionPerPartnershipAgreement
Namespace Prefix:	amgp_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration

Represents minimum quarterly distribution as per partnership agreement.

No definition available.

Name:	amgp_LimitedPartnerMinimumQuarterlyDistributionPerPartnershipAgreement
Namespace Prefix:	amgp_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration

Represents the pro rata cash distribution made to the holders of common and subordinated units.

No definition available.

Name:	amgp_LimitedPartnersProRataDistributionToHoldersOfCommonAndSubordinatedUnits
Namespace Prefix:	amgp_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration

Represents the minimum amount of cash distributions per common unit and subordinated unit in any quarter which will trigger distributions to the entity's unitholders and general partner as holder of incentive distribution rights.

No definition available.

Name:	amgp_MinimumAmountOfLimitedPartnersProRataDistributionRequiredToTriggerUnitholdersAndGeneralPartnerDistributions
Namespace Prefix:	amgp_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

Represents the unitholders marginal percentage interest in distribution.

No definition available.

Name:	amgp_UnitHoldersMarginalPercentageInterestInDistributionPercentageOfLimitedPartnerInterest
Namespace Prefix:	amgp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Amount of equity impact of cash distribution declared to unit-holder of limited partnership (LP).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70434-108055

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Name:	us-gaap_DistributionMadeToLimitedPartnerCashDistributionsDeclared
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Per unit of ownership amount of cash distributions declared to unit-holder of a limited partnership (LP).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70478-108055

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 272
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70434-108055

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Name:	us-gaap_DistributionMadeToLimitedPartnerDistributionsDeclaredPerUnit
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

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.

No definition available.

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

Name:	us-gaap_PartnerTypeOfPartnersCapitalAccountAxis=us-gaap_GeneralPartnerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_PartnerCapitalComponentsAxis=amgp_CommonUnitAndSubordinatedUnitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	amgp_TotalQuarterlyDistributionTargetAmountAxis=amgp_Above0.1955UpTo0.2125Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	amgp_TotalQuarterlyDistributionTargetAmountAxis=amgp_Above0.2125UpTo0.2550Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	amgp_TotalQuarterlyDistributionTargetAmountAxis=amgp_Above0.2550Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: