Customer Allowances and Discounts - Additional Information (Detail) (Allowance for Doubtful Accounts [Member], USD $) In Millions, unless otherwise specified	Nov. 23, 2012	Feb. 29, 2012	Nov. 25, 2011
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Trade allowances and discounts settled in cash	$ 14.0	$ 13.7	$ 13.3

Customer allowances and discounts settled in cash.

No definition available.

Name:	am_CustomerAllowancesAndDiscountsSettledInCash
Namespace Prefix:	am_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant