| Document And Entity Information | May 06, 2021 |
| Document Information [Line Items] | |
| Entity, Registrant Name | NATIONAL HEALTHCARE CORPORATION |
| Document, Type | 8-K |
| Document, Period End Date | May 6, 2021 |
| Entity, Incorporation, State or Country Code | DE |
| Entity, File Number | 001-13489 |
| Entity, Tax Identification Number | 52-2057472 |
| Entity, Address, Address Line One | 100 Vine Street |
| Entity, Address, City or Town | Murfreesboro |
| Entity, Address, State or Province | TN |
| Entity, Address, Postal Zip Code | 37130 |
| City Area Code | 615 |
| Local Phone Number | 890-2020 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | NHC |
| Security Exchange Name | NYSEAMER |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0001047335 |
