| Document and Entity Information | Dec. 31, 2020 |
| Cover [Abstract] | |
| Entity Central Index Key | 0001351051 |
| Document Type | 8-K |
| Document Period End Date | Dec. 31, 2020 |
| Entity File Number | 001-33459 |
| Entity Registrant Name | Genesis Healthcare, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 20-3934755 |
| Entity Address, Address Line One | 101 East State Street |
| Entity Address, City or Town | Kennett Square |
| Entity Address, State or Province | PA |
| Entity Address, Postal Zip Code | 19348 |
| City Area Code | 610 |
| Local Phone Number | 444-6350 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Class A Common Stock, $0.001 par value per share |
| Trading Symbol | GEN |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
