Customer Allowances and Discounts - Additional Information (Detail) (Allowance for Rebates [Member], USD $) In Millions, unless otherwise specified	May 30, 2014	Feb. 28, 2014	May 31, 2013
Allowance for Rebates [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Trade allowances and discounts settled in cash	$ 14.6	$ 16.5	$ 14.3

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