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Significant Accounting Policies (Details 2)	12 Months Ended
	Sep. 30, 2013
Minimum
Length of fiscal year	364 days
Property and Equipment
Estimated useful lives for equipment, furniture and fixtures	3 years
Maximum
Length of fiscal year	371 days
Property and Equipment
Estimated useful lives for equipment, furniture and fixtures	10 years

X

- Definition

Represents the length of fiscal years of the company.

+ References

No definition available.

+ Details

Name:	acm_LengthOfFiscalYear
Namespace Prefix:	acm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	acm_PropertyAndEquipmentAbstract
Namespace Prefix:	acm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration