| Document and Entity Information Document | Sep. 16, 2019 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Sep. 16, 2019 |
| Entity Registrant Name | HMS HOLDINGS CORP. |
| Entity Central Index Key | 0001196501 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 0-50194 |
| Entity Tax Identification Number | 11-3656261 |
| Entity Address, Address Line One | 5615 High Point Drive |
| Entity Address, City or Town | Irving |
| Entity Address, State or Province | TX |
| Entity Address, Postal Zip Code | 75038 |
| City Area Code | 214 |
| Local Phone Number | 453-3000 |
| Entity Information, Former Legal or Registered Name | Not Applicable |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock $0.01 par value |
| Trading Symbol | HMSY |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
