v3.7.0.1

Sale of Common Units Under Equity Distribution Agreement (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Sep. 30, 2016	Jun. 30, 2017
Sale of Common Units Under Equity Distribution Agreement
Maximum aggregate offering price of common limited partners units under an equity distribution agreement	$ 250.0
Units issued and sold (in shares)		700,031
Net proceeds from issue and sale of common units		$ 23.1
Remaining capacity to issue additional common units under an equity distribution agreement		$ 159.9

X

- Definition

Maximum aggregate offering price of common limited partners units under an equity distribution agreement.

+ References

No definition available.

+ Details

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

X

- Definition

Remaining capacity to issue additional common units under an equity distribution agreement.

+ References

No definition available.

+ Details

Name:	am_CommonLimitedPartnersUnitsDistributionAgreementRemainingCapacity
Namespace Prefix:	am_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Total limited partner units issued during the period due to the sale of units.

+ References

No definition available.

+ Details

Name:	am_LimitedPartnersSaleOfUnits
Namespace Prefix:	am_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Total amount of limited partner units issued during the period due to the sale of units.

+ References

No definition available.

+ Details

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

X

- References

No definition available.

+ Details

Name:	am_SaleOfCommonUnitsUnderEquityDistributionAgreementAbstract
Namespace Prefix:	am_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration