v3.7.0.1

Sale of Common Units Under Equity Distribution Agreement (Details) - USD ($) $ in Millions | 3 Months Ended |
--- | --- | ---
Sep. 30, 2016 | Mar. 31, 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 |
Remaining capacity to issue additional common units under an equity distribution agreement |  | $ 183.8

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
- References No definition available. + Details
Name: | am_SaleOfCommonUnitsUnderEquityDistributionAgreementAbstract
Namespace Prefix: | am_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration