Deferred Costs - Summary of Changes in Carrying Amount of Corporation's Net Deferred Costs (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Feb. 29, 2016	Feb. 29, 2016	Feb. 28, 2015	Feb. 28, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Beginning balance		$ 299,227	$ 294,322	$ 272,597
Payments		108,290	124,258	130,970
Amortization		(121,169)	(114,125)	(108,761)
Contract asset impairment	$ (8,510)	(7,657)	(4,422)
Currency translation		(827)	(806)	(484)
Ending balance	$ 277,864	$ 277,864	$ 299,227	$ 294,322

Amortization of amounts previously capitalized under retail supply agreements with customers.

No definition available.

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

- Definition

Currency translation and other deferred costs, net.

+ References

No definition available.

+ Details

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

- Definition

Advance payments, allowances and other credits given to customers under retail supply agreements that are capitalized and recognized over the life of the supply agreement.

+ References

No definition available.

+ Details

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

- Definition

Net amount of total deferred cost assets and total future payment commitments associated with retail supply agreements.

+ References

No definition available.

+ Details

Name:	am_DeferredCostsNet
Namespace Prefix:	am_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

The charge against earnings resulting from the write down of long lived assets other than goodwill due to the difference between the carrying value and lower fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51719941&loc=d3e2921-110230

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

+ Details

Name:	us-gaap_OtherAssetImpairmentCharges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration