| Document and Entity Information Document - USD ($) $ in Thousands | 12 Months Ended | |
| Dec. 31, 2022 | Feb. 13, 2023 | |
| Document And Entity Information [Abstract] | ||
| Entity Central Index Key | 0000877860 | |
| Document Type | 10-K/A | |
| Document Period End Date | Dec. 31, 2022 | |
| 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 | |
| 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 | |
| Document Fiscal Year Focus | 2022 | |
| Entity Voluntary Filers | No | |
| Entity Current Reporting Status | Yes | |
| Entity Interactive Data Current | Yes | |
| Entity Filer Category | Large Accelerated Filer | |
| Entity Small Business | false | |
| Entity Shell Company | false | |
| Entity Public Float | $ 2,581,065 | |
| Entity Common Stock, Shares Outstanding | 43,388,742 | |
| ICFR Auditor Attestation Flag | true | |
| Document Transition Report | false | |
| Entity Well-known Seasoned Issuer | Yes | |
| Document Annual Report | true | |
| Current Fiscal Year End Date | --12-31 | |
| Document Fiscal Period Focus | FY | |
| Auditor Name | BDO USA, LLP | |
| Auditor Location | Nashville, TN | |
| Auditor Firm ID | 243 |
