The percentage of the purchase price using cash on hand as the source of funding for a business acquisition.

No definition available.

Name:	hmsy_BusinessAcquisitionFundingSourceCashOnHandPercentage
Namespace Prefix:	hmsy_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage of the purchase price using an existing credit line as the source of funding for a business acquisition.

+ References

No definition available.

+ Details

Name:	hmsy_BusinessAcquisitionFundingSourceExistingCreditLinePercentage
Namespace Prefix:	hmsy_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of increase (decrease) of acquired deferred tax liabilities for purchase accounting adjustments.

+ References

No definition available.

+ Details

Name:	hmsy_BusinessCombinationDeferredTaxLiabilitiesPurchaseAccountingAdjustment
Namespace Prefix:	hmsy_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of increase (decrease) to assets, excluding financial assets and goodwill, lacking physical substance with a finite life for purchase accounting adjustments.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetsPurchaseAccountingAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 16
-URI http://asc.fasb.org/extlink&oid=84229725&loc=d3e961-128460

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillPurchaseAccountingAdjustments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=hmsy_ElizaHoldingCorpMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 2 - Business Combinations (Details Textual) - Eliza Holding Corp [Member] - USD ($) $ in Millions		2 Months Ended	3 Months Ended	6 Months Ended
	Apr. 17, 2017	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2017
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
Payments to Acquire Businesses, Gross	$ 171.6
Business Acquisition, Funding Source, Cash on Hand, Percentage	75.00%
Business Acquisition, Funding Source, Existing Credit Line, Percentage	25.00%
Finite-Lived Intangible Assets, Purchase Accounting Adjustments			$ 8.9
Business Combination, Deferred Tax Liabilities, Purchase Accounting Adjustment			3.4
Goodwill, Purchase Accounting Adjustments			$ (5.5)
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual				$ 17.5
Customer Relationships [Member]
Finite-Lived Intangible Asset, Useful Life		36 years	15 years