XML 70 R49.htm IDEA: XBRL DOCUMENT
v3.5.0.2

Significant Accounting Policies (Details) $ in Billions | 12 Months Ended
--- | ---
Sep. 30, 2016 USD ($) item | Sep. 30, 2015 USD ($) | Sep. 30, 2014 USD ($)
Fiscal Year |  |  |
Length of Fiscal Year | 364 days | 364 days | 371 days
Revenue Recognition |  |  |
Other direct costs | $ | $ 8.4 | $ 8.3 | $ 3.5
Number of cost reimbursable contracts | 2 |  |
Cost-Plus Contracts |  |  |
Number of major types of cost-plus contracts the Company enters into | 2 |  |
Fixed Price Contracts |  |  |
Number of types of fixed price contracts | 2 |  |
Pension Plans |  |  |
Amortization period of the difference between actual return and expected return | 5 years |  |
Specified percentage to be exceeded for amortization of cumulative, net unrecognized gains or losses (as a percent) | 10.00% |  |
Service Related Contracts |  |  |
Service-Related Contracts |  |  |
Cost reimbursable (as a percent) | 53.00% | 57.00% | 46.00%
Guaranteed maximum price (as a percent) | 15.00% | 15.00% | 14.00%
Fixed price (as a percent) | 32.00% | 28.00% | 40.00%
Minimum |  |  |
Fiscal Year |  |  |
Length of Fiscal Year | 364 days |  |
Property and Equipment |  |  |
Estimated useful lives for equipment furniture and fixtures | 3 years |  |
Maximum |  |  |
Fiscal Year |  |  |
Length of Fiscal Year | 371 days |  |
Property and Equipment |  |  |
Estimated useful lives for equipment furniture and fixtures | 10 years |  |

X
- References No definition available. + Details
Name: | acm_CostPlusContractsAbstract
Namespace Prefix: | acm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents percentage of total revenues that are from cost reimbursable revenues. + References No definition available. + Details
Name: | acm_CostReimbursableAmountPercentage
Namespace Prefix: | acm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the percentage of the greater of the projected benefit obligation or the market related value of plan assets that has to be exceeded for amortization of cumulative net unrecognized gains or losses. + References No definition available. + Details
Name: | acm_DefinedBenefitPensionPlanAmortizationOfGainsLossesSpecifiedPercentageToBeExceeded
Namespace Prefix: | acm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the amortization period of the difference between the actual return (including capital, dividends, and interest) and the expected return 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_DefinedBenefitPensionPlanAmortizationPeriodOfDifferenceBetweenActualReturnAndExpectedReturn
Namespace Prefix: | acm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | acm_FiscalYearAbstract
Namespace Prefix: | acm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents percentage of of total revenues that are from fixed price contact revenues. + References No definition available. + Details
Name: | acm_FixedPriceContractPercentage
Namespace Prefix: | acm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | acm_FixedPriceContractsAbstract
Namespace Prefix: | acm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents percentage of of total revenues that are from guaranteed maximum price contract revenues. + References No definition available. + Details
Name: | acm_GuaranteedMaximumPriceContractPercentage
Namespace Prefix: | acm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the length of fiscal year of the company 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_LengthOfFiscalYear
Namespace Prefix: | acm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of cost reimbursable contracts that the entity enters into. + References No definition available. + Details
Name: | acm_NumberOfCostReimbursableContracts
Namespace Prefix: | acm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of major types of cost-plus contracts that the entity enters into. + References No definition available. + Details
Name: | acm_NumberOfMajorTypesOfCostPlusContracts
Namespace Prefix: | acm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of types of fixed price contracts. + References No definition available. + Details
Name: | acm_NumberOfTypesOfFixedPriceContracts
Namespace Prefix: | acm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | acm_PensionPlansAbstract
Namespace Prefix: | acm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition N\A + References No definition available. + Details
Name: | acm_ServiceRelatedContractsAbstract
Namespace Prefix: | acm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Other costs incurred and are directly related to services rendered by an entity during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.2(d)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 + Details
Name: | us-gaap_OtherCostOfServices
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentAbstract
Namespace Prefix: | us-gaap_
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

X
- References No definition available. + Details
Name: | us-gaap_RevenueRecognitionAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_TypeOfArrangementAxis=acm_ServiceRelatedContractsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |