Annual report pursuant to Section 13 and 15(d)

Cover Page

Cover Page - USD ($)
12 Months Ended
Sep. 30, 2020
Nov. 16, 2020
Mar. 31, 2020
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Sep. 30, 2020    
Document Transition Report false    
Entity File Number 1-12997    
Entity Registrant Name Maximus, Inc.    
Entity Incorporation, State or Country Code VA    
Entity Tax Identification Number 54-1000588    
Entity Address, Address Line One 1891 Metro Center Drive    
Entity Address, City or Town Reston    
Entity Address, State or Province VA    
Entity Address, Postal Zip Code 20190    
City Area Code 703    
Local Phone Number 251-8500    
Title of 12(b) Security Common Stock, no par value    
Trading Symbol MMS    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
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    
ICFR Auditor Attestation Flag true    
Entity Shell Company false    
Entity Public Float     $ 3,527,771,000
Entity Common Stock, Shares Outstanding   61,452,520  
Documents Incorporated by Reference Portions of the registrant's definitive Proxy Statement for its 2021 Annual Meeting of Shareholders to be held on March 16, 2021, which definitive Proxy Statement will be filed with the Securities and Exchange Commission not later than 120 days after the end of the registrant's fiscal year, are incorporated by reference into Part III of this Form 10-K.    
Entity Central Index Key 0001032220    
Amendment Flag false    
Current Fiscal Year End Date --09-30    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY