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

Number of years after the grant date that an equity-based award expires.

No definition available.

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

Cash payments made to settle "in-the-money" stock options.

No definition available.

Name:	am_StockOptionsSettledAtFairValue
Namespace Prefix:	am_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Total amount paid in cash to settle outstanding stock options as of the Merger Date.

No definition available.

Name:	am_StockOptionsSettlementThroughCashPayment
Namespace Prefix:	am_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901