XML 11 R1.htm IDEA: XBRL DOCUMENT v3.21.2
Document and Entity Information - shares
 9 Months Ended
Jun. 30, 2021
Aug. 05, 2021
Document and Entity Information    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Jun. 30, 2021  
Document Transition Report false  
Entity File Number 000-52423  
Entity Registrant Name AECOM  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 61-1088522  
Entity Address, Address Line One 300 South Grand Avenue, Suite 900  
Entity Address, City or Town Los Angeles  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 90071  
City Area Code 213  
Local Phone Number 593-8100  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Title of 12(b) Security Common Stock  
Trading Symbol ACM  
Security Exchange Name NYSE  
Entity Common Stock, Shares Outstanding   144,061,817
Current Fiscal Year End Date --09-30  
Document Fiscal Year Focus 2021  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Entity Central Index Key 0000868857