Liability for Appeals (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Other Liabilities Disclosure [Abstract]
Liability for appeals	$ 3,906	$ 3,570

Liability as of the balance sheet date for the estimated liability for appeals and estimated allowance for appeals related to receivables associated with client contracts that have be received on or before the balance sheet date.

No definition available.

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