| Document and Entity Information Document | Jun. 03, 2021 |
| Document And Entity Information [Abstract] | |
| Entity Central Index Key | 0000877860 |
| Document Type | 8-K |
| Document Period End Date | Jun. 3, 2021 |
| Entity Registrant Name | NATIONAL HEALTH INVESTORS INC |
| Entity Incorporation, State or Country Code | MD |
| Entity File Number | 001-10822 |
| Entity Tax Identification Number | 62-1470956 |
| Entity Address, Address Line One | 222 Robert Rose Drive |
| Entity Address, City or Town | Murfreesboro |
| Entity Address, State or Province | TN |
| Entity Address, Postal Zip Code | 37129 |
| City Area Code | 615 |
| Local Phone Number | 890-9100 |
| 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 | NHI |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
