Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Sep. 30, 2022
Deferred tax assets/(liabilities):
Costs deductible in future periods	$ 37,036	$ 36,604
Deferred revenue	8,712	7,273
Stock compensation	6,212	4,918
Capital loss carryforward	2,391	2,391
Net operating loss carryforwards	33,278	6,666
Amortization of goodwill and intangibles	(189,316)	(198,903)
Capitalized software	(28,246)	(15,445)
Accounts receivable - unbilled	(7,963)	(12,087)
Property and equipment	(3,437)	(2,577)
Prepaid expenses	(10,906)	(11,522)
Financial instruments	(8,158)	(8,261)
Valuation allowance	(34,643)	(8,075)
Other	(6,399)	(2,111)
Net deferred tax liability	$ (201,439)	$ (201,129)

Deferred Tax Liabilities, Financial Instruments

No definition available.

Name:	mms_DeferredTaxLiabilitiesFinancialInstruments
Namespace Prefix:	mms_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The current portion of the amount as of the balance sheet date of the estimated future tax effects attributable to the difference between the tax basis of unbilled receivables and the basis of unbilled receivables determined in accordance with generally accepted accounting principles.

+ References

No definition available.

+ Details

Name:	mms_DeferredTaxLiabilitiesUnbilledReceivables
Namespace Prefix:	mms_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_ComponentsOfDeferredTaxAssetsAndLiabilitiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible capital loss carryforwards.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-6

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-8

+ Details

Name:	us-gaap_DeferredTaxAssetsCapitalLossCarryforwards
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from deferred income.

+ References

+ Details

Name:	us-gaap_DeferredTaxAssetsDeferredIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

+ References

+ Details

Name:	us-gaap_DeferredTaxAssetsOperatingLossCarryforwards
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, before allocation of valuation allowances, of deferred tax asset attributable to deductible differences from reserves and accruals, compensation and benefit costs, and other provisions, reserves, and allowances.

+ References

+ Details

Name:	us-gaap_DeferredTaxAssetsTaxDeferredExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation.

+ References

+ Details

Name:	us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-2

+ Details

Name:	us-gaap_DeferredTaxAssetsValuationAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences without jurisdictional netting.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-2

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482525/740-10-45-6

+ Details

Name:	us-gaap_DeferredTaxLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred tax liability attributable to taxable temporary differences from capitalized software.

+ References

+ Details

Name:	us-gaap_DeferredTaxLiabilitiesDeferredExpenseCapitalizedSoftware
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred tax liability attributable to taxable temporary differences from intangible assets including goodwill.

+ References

+ Details

Name:	us-gaap_DeferredTaxLiabilitiesGoodwillAndIntangibleAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred tax liability attributable to taxable temporary differences classified as other.

+ References

+ Details

Name:	us-gaap_DeferredTaxLiabilitiesOther
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred tax consequences attributable to taxable temporary differences derived from prepaid expenses.

+ References

No definition available.

+ Details

Name:	us-gaap_DeferredTaxLiabilitiesPrepaidExpenses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

+ References

+ Details

Name:	us-gaap_DeferredTaxLiabilitiesPropertyPlantAndEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant