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Other Liabilities - Additional Information (Detail) (WHQ Development [Member], USD $)
In Millions, unless otherwise specified
9 Months Ended
Nov. 28, 2014
WHQ Development [Member]
 
Schedule Of Other Liabilities [Line Items]  
Anticipated year of completion for new world headquarters building 2016
New World Headquarters construction costs to date $ 19.0us-gaap_ConstructionInProgressGross
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= am_WorldHeadQuartersDevelopmentMember
Offsetting liability $ 19.0am_ConstructionCostsOffsettingLiability
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= am_WorldHeadQuartersDevelopmentMember