XML 27 R1.htm IDEA: XBRL DOCUMENT v3.20.2
Document and Entity Information - USD ($)
$ in Billions
 12 Months Ended
Sep. 30, 2020
Nov. 12, 2020
Mar. 27, 2020
Document and Entity Information      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Sep. 30, 2020    
Document Transition Report false    
Entity File Number 0-52423    
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, 9th Floor    
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 593-8000    
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   150,763,791  
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Public Float     $ 4.5
Current Fiscal Year End Date --09-30    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY    
Amendment Flag false    
Entity Central Index Key 0000868857