Acquisition of Citizen Engagement Centers Business - Pro Forma Results (Details) - USD ($) $ / shares in Units, $ in Thousands  | 
3 Months Ended | |
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Dec. 31, 2018  | 
Dec. 31, 2017  | 
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| Business Combinations [Abstract] | ||
| Revenue | $ 763,048 | $ 822,132 | 
| Net income | $ 59,196 | $ 63,293 | 
| Basic earnings per share attributable to MAXIMUS (in dollars per share) | $ 0.92 | $ 0.95 | 
| Diluted earnings per share attributed to MAXIMUS (in dollars per share) | $ 0.91 | $ 0.94 | 
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- Definition Per basic share amount of pro forma income from continuing operations, after tax, as if the business combination had been completed at the beginning of a period. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition Per diluted share amount of pro forma income from continuing operations, after tax, as if the business combination had been completed at the beginning of a period. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef 
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- Definition The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- Definition The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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- References No definition available. 
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