| Document and Entity Information Document | Sep. 28, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Sep. 28, 2021 |
| Entity Registrant Name | Phreesia, Inc. |
| Amendment Flag | false |
| Entity Central Index Key | 0001412408 |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38977 |
| Entity Tax Identification Number | 20-2275479 |
| Entity Address, Address Line One | 434 Fayetteville Street, Suite 1400 |
| Entity Address, City or Town | Raleigh |
| Entity Address, State or Province | NC |
| Entity Address, Postal Zip Code | 27601 |
| City Area Code | 888 |
| Local Phone Number | 654-7473 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | PHR |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
