Leases - Schedule of Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Leases [Abstract]
2019	$ 5,778
2020	5,420
2021	3,742
2022	2,531
2023	2,236
Thereafter	2,947
Total lease payments	$ 22,654

Lessee, Operating Lease, Liability, Payments, Net of Sublease Income, Due

No definition available.

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Lessee, Operating Lease, Liability, Payments, Net of Sublease Income, Due After Year Five

No definition available.

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Lessee, Operating Lease, Liability, Payments, Net of Sublease Income, Due Next Twelve Months

No definition available.

Name:	hmsy_LesseeOperatingLeaseLiabilityPaymentsNetOfSubleaseIncomeDueNextTwelveMonths
Namespace Prefix:	hmsy_
Data Type:	xbrli:monetaryItemType
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Lessee, Operating Lease, Liability, Payments, Net of Sublease Income, Due Year Five

No definition available.

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Namespace Prefix:	hmsy_
Data Type:	xbrli:monetaryItemType
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Lessee, Operating Lease, Liability, Payments, Net of Sublease Income, Due Year Four

No definition available.

Name:	hmsy_LesseeOperatingLeaseLiabilityPaymentsNetOfSubleaseIncomeDueYearFour
Namespace Prefix:	hmsy_
Data Type:	xbrli:monetaryItemType
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Lessee, Operating Lease, Liability, Payments, Net of Sublease Income, Due Year Three

No definition available.

Name:	hmsy_LesseeOperatingLeaseLiabilityPaymentsNetOfSubleaseIncomeDueYearThree
Namespace Prefix:	hmsy_
Data Type:	xbrli:monetaryItemType
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Lessee, Operating Lease, Liability, Payments, Net of Sublease Income, Due Year Two

No definition available.

Name:	hmsy_LesseeOperatingLeaseLiabilityPaymentsNetOfSubleaseIncomeDueYearTwo
Namespace Prefix:	hmsy_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

No definition available.