| Document And Entity Information | May 04, 2022 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | May 4, 2022 |
| Entity Registrant Name | LifeStance Health Group, Inc. |
| Entity Central Index Key | 0001845257 |
| Entity Emerging Growth Company | true |
| Entity File Number | 001-40478 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 86-1832801 |
| Entity Address, Address Line One | 4800 N. Scottsdale Road |
| Entity Address, Address Line Two | Suite 6000 |
| Entity Address, City or Town | Scottsdale |
| Entity Address, State or Province | AZ |
| Entity Address, Postal Zip Code | 85251 |
| City Area Code | 602 |
| Local Phone Number | 767-2100 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Ex Transition Period | false |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | LFST |
| Security Exchange Name | NASDAQ |
