Document And Entity Information - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Feb. 15, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Entity Registrant Name	NATIONAL HEALTH INVESTORS INC
Entity Central Index Key	0000877860
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		42,735,034
Entity Current Reporting Status	Yes
Entity Public Float:			$ 2,986,872
Entity Voluntary Filers:	No
Entity Well-known Seasoned Issuer:	Yes
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false