Maximus, Inc. Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plans And Deferred Compensation - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Percentage of liabilities that can be met plan assets	90.00%
Investments in mutual funds within the rabbi trust	$ 28.5
United States
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contribution to defined contribution plans	17.3	$ 13.2	$ 12.3
Foreign Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contribution to defined contribution plans	$ 22.8	$ 18.6	$ 18.6