v2.4.1.9

Partnership Equity and Distributions (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	0 Months Ended	2 Months Ended	3 Months Ended	12 Months Ended
	Feb. 02, 2015	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2014
Partnership equity and distributions
Annual cash distribution (per unit)		0.68am_LimitedPartnerMinimumAnnualDistributionPerPartnershipAgreement
Cash balance to be maintained for distribution per quarter		$ 26am_CashAvailableForDistributionsPerQuarter
Cash balance to be maintained for distribution per year		$ 105am_CashAvailableForDistributionsPerYear
Pro rata cash distribution to the holders of common and subordinate units		0.1955am_LimitedPartnersProRataDistributionToHoldersOfCommonAndSubordinatedUnits
Distribution Made to Limited Partner, Distributions Declared, Per Unit	$ 0.0943us-gaap_DistributionMadeToLimitedPartnerDistributionsDeclaredPerUnit		$ 0.0943us-gaap_DistributionMadeToLimitedPartnerDistributionsDeclaredPerUnit
Above $0.1955 up to $0.2125 (Member)
Partnership equity and distributions
Unitholders marginal percentage interest in distribution				85.00%am_UnitHoldersMarginalPercentageInterestInDistributionPercentageOfLimitedPartnerInterest / am_TotalQuarterlyDistributionTargetAmountAxis = am_Above0.1955UpTo0.2125Member
General Partners marginal percentage interest in distribution				15.00%am_IncentiveDistributionDistributionPercentage / am_TotalQuarterlyDistributionTargetAmountAxis = am_Above0.1955UpTo0.2125Member
Above $0.2125 up to $0.2550 (Member)
Partnership equity and distributions
Unitholders marginal percentage interest in distribution				75.00%am_UnitHoldersMarginalPercentageInterestInDistributionPercentageOfLimitedPartnerInterest / am_TotalQuarterlyDistributionTargetAmountAxis = am_Above0.2125UpTo0.2550Member
General Partners marginal percentage interest in distribution				25.00%am_IncentiveDistributionDistributionPercentage / am_TotalQuarterlyDistributionTargetAmountAxis = am_Above0.2125UpTo0.2550Member
Above $0.2550 (Member)
Partnership equity and distributions
Pro rata cash distribution to the holders of common and subordinate units				0.2550am_LimitedPartnersProRataDistributionToHoldersOfCommonAndSubordinatedUnits / am_TotalQuarterlyDistributionTargetAmountAxis = am_Above0.2550Member
Unitholders marginal percentage interest in distribution				50.00%am_UnitHoldersMarginalPercentageInterestInDistributionPercentageOfLimitedPartnerInterest / am_TotalQuarterlyDistributionTargetAmountAxis = am_Above0.2550Member
General Partners marginal percentage interest in distribution				50.00%am_IncentiveDistributionDistributionPercentage / am_TotalQuarterlyDistributionTargetAmountAxis = am_Above0.2550Member
Minimum
Partnership equity and distributions
Minimum quarterly cash distribution (per unit)		0.17am_LimitedPartnerMinimumQuarterlyDistributionPerPartnershipAgreement / us-gaap_RangeAxis = us-gaap_MinimumMember
Minimum | Above $0.1955 up to $0.2125 (Member)
Partnership equity and distributions
Pro rata cash distribution to the holders of common and subordinate units				0.1955am_LimitedPartnersProRataDistributionToHoldersOfCommonAndSubordinatedUnits / us-gaap_RangeAxis = us-gaap_MinimumMember / am_TotalQuarterlyDistributionTargetAmountAxis = am_Above0.1955UpTo0.2125Member
Minimum | Above $0.2125 up to $0.2550 (Member)
Partnership equity and distributions
Pro rata cash distribution to the holders of common and subordinate units				0.2125am_LimitedPartnersProRataDistributionToHoldersOfCommonAndSubordinatedUnits / us-gaap_RangeAxis = us-gaap_MinimumMember / am_TotalQuarterlyDistributionTargetAmountAxis = am_Above0.2125UpTo0.2550Member
Maximum | Above $0.1955 up to $0.2125 (Member)
Partnership equity and distributions
Pro rata cash distribution to the holders of common and subordinate units				0.2125am_LimitedPartnersProRataDistributionToHoldersOfCommonAndSubordinatedUnits / us-gaap_RangeAxis = us-gaap_MaximumMember / am_TotalQuarterlyDistributionTargetAmountAxis = am_Above0.1955UpTo0.2125Member
Maximum | Above $0.2125 up to $0.2550 (Member)
Partnership equity and distributions
Pro rata cash distribution to the holders of common and subordinate units				0.2550am_LimitedPartnersProRataDistributionToHoldersOfCommonAndSubordinatedUnits / us-gaap_RangeAxis = us-gaap_MaximumMember / am_TotalQuarterlyDistributionTargetAmountAxis = am_Above0.2125UpTo0.2550Member

X

- Definition

Represnts the amount of cash balance to be maintained for distribution per quarter.

+ References

No definition available.

+ Details

Name:	am_CashAvailableForDistributionsPerQuarter
Namespace Prefix:	am_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Represnts the amount of cash balance to be maintained for distribution per year.

+ References

No definition available.

+ Details

Name:	am_CashAvailableForDistributionsPerYear
Namespace Prefix:	am_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Percentage of incentive obligation paid in cash or stock during the period to a limited liability corporation managing member or limited partnership partner, as the holder of our incentive rights ("IDRs").

+ References

No definition available.

+ Details

Name:	am_IncentiveDistributionDistributionPercentage
Namespace Prefix:	am_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Represents minimum annual distribution as per partnership agreement.

+ References

No definition available.

+ Details

Name:	am_LimitedPartnerMinimumAnnualDistributionPerPartnershipAgreement
Namespace Prefix:	am_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Represents minimum quarterly distribution as per partnership agreement.

+ References

No definition available.

+ Details

Name:	am_LimitedPartnerMinimumQuarterlyDistributionPerPartnershipAgreement
Namespace Prefix:	am_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration

X

- Definition

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

+ References

No definition available.

+ Details

Name:	am_LimitedPartnersProRataDistributionToHoldersOfCommonAndSubordinatedUnits
Namespace Prefix:	am_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Represnts the unitholders marginal percentage interest in distribution.

+ References

No definition available.

+ Details

Name:	am_UnitHoldersMarginalPercentageInterestInDistributionPercentageOfLimitedPartnerInterest
Namespace Prefix:	am_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

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

+ References

Reference 1: 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



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 272

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6373374&loc=d3e70434-108055

+ Details

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

X

- Details

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

X

- Details

Name:	am_TotalQuarterlyDistributionTargetAmountAxis=am_Above0.1955UpTo0.2125Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	am_TotalQuarterlyDistributionTargetAmountAxis=am_Above0.2125UpTo0.2550Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	am_TotalQuarterlyDistributionTargetAmountAxis=am_Above0.2550Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

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