Retirement and Postretirement Benefit Plans (Details 8) (USD $) In Thousands, unless otherwise specified	Feb. 29, 2012
Pension Plans [Member]
Details of benefits expected to be paid out
2013	$ 11,024
2014	11,230
2015	11,315
2016	11,161
2017	11,496
2018 - 2022	57,264
Postretirement benefit plan [Member]
Details of benefits expected to be paid out
2013	5,325
2013	4,610
2014	5,370
2014	4,703
2015	5,454
2015	4,730
2016	5,547
2016	4,754
2017	5,584
2017	5,390
2018 - 2022	27,996
2018 - 2022	$ 27,046

Defined benefit plan expected future benefit payments net of subsidy in year five.

No definition available.

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- Definition

Defined benefit plan expected future benefit payments net of subsidy in year four.

+ References

No definition available.

+ Details

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- Definition

Defined benefit plan expected future benefit payments net of subsidy in year one.

+ References

No definition available.

+ Details

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- Definition

Defined benefit plan expected future benefit payments net of subsidy in year five.

+ References

No definition available.

+ Details

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- Definition

Defined benefit plan expected future benefit payments net of subsidy in year three.

+ References

No definition available.

+ Details

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- Definition

Defined benefit plan expected future benefit payments net of subsidy in year two.

+ References

No definition available.

+ Details

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Namespace Prefix:	am_
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- Details

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- Definition

The amount of the aggregate benefits expected to be paid in the five fiscal years thereafter (the aggregate amount of benefits expected to be paid in years 6 through 10 after the date of the latest statement of financial position).

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph f

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920

+ Details

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- Definition

The amount of the benefits expected to be paid in Year 5.

+ References

+ Details

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- Definition

The amount of the benefits expected to be paid in Year 4.

+ References

+ Details

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- Definition

The amount of the benefits expected to be paid in Year 1.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

The amount of the benefits expected to be paid in Year 3.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

The amount of the benefits expected to be paid in Year 2.

+ References

+ Details

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