Document And Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 05, 2020
Document And Entity Information [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	001-10822
Entity Registrant Name	National Health Investors Inc
Entity Incorporation, State or Country Code	MD
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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		44,650,002
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Central Index Key	0000877860
Current Fiscal Year End Date	--12-31