XML 27 R79.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Major Clients (Details) (Sales Revenue, Services, Net [Member], Customer Concentration Risk [Member]) | 12 Months Ended
--- | ---
Sep. 30, 2014 | Sep. 30, 2013 | Sep. 30, 2012
Percentage of total revenue |  |  |
Period for which criteria of threshold percentage for disclosure not met in past | 5 years |  |
Maximum |  |  |
Percentage of total revenue |  |  |
Percentage of revenue accounted for by no other single client (as a percent) | 10.00% |  |
Agencies of U.S. Federal Government [Member] |  |  |
Percentage of total revenue |  |  |
Percentage of the Company's revenue (as a percent) | 15.00% | 18.00% | 18.00%
Agencies of U.S. Federal Government [Member] | Management Support Services [Member] |  |  |
Percentage of total revenue |  |  |
Percentage of the Company's revenue (as a percent) | 3.00% | 4.00% | 4.00%

X
- Definition Represents the period for which criteria of threshold percentage for disclosure not met in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | acm_PeriodForWhichCriteriaOfThresholdPercentageForDisclosureNotMet
Namespace Prefix: | acm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Threshold percentage which the entity uses for disclosure. + References No definition available. + Details
Name: | acm_ThresholdForDisclosurePercentage
Namespace Prefix: | acm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_ConcentrationRiskLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13537-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6404-108592 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13531-108611 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6351-108592 + Details
Name: | us-gaap_ConcentrationRiskPercentage1
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration