Debt (Accounts Receivable Facility) - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Feb. 28, 2015	Feb. 28, 2014
Debt Disclosure [Line Items]
Debt due within one year	$ 0us-gaap_DebtCurrent	$ 20,000us-gaap_DebtCurrent
Accounts Receivable Facility [Member]
Debt Disclosure [Line Items]
Available financing of receivables purchase agreement	50,000
Debt due within one year	$ 0	$ 0
Annual facility fee	0.60%
Accounts Receivable Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Disclosure [Line Items]
Debt instrument variable rate	0.40%

Maximum borrowing capacity under the Accounts Receivable facility.

No definition available.

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

- Definition

Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19,20)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19

-Article 5

+ Details

Name:	us-gaap_DebtCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=am_AccountsReceivableFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: