Document and Entity Information Document - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Feb. 14, 2020	Jun. 30, 2019
Cover page.
Amendment Flag	true
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Title of 12(b) Security	Common Stock, $0.01 par value
City Area Code	(615)
Entity Incorporation, State or Country Code	MD
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Type	10-K/A
Document Transition Report	false
Entity File Number	001-10822
Entity Registrant Name	National Health Investors Inc
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
Local Phone Number	890-9100
Trading Symbol	NHI
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 3,495,872
Entity Common Stock, Shares Outstanding		44,591,660
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Central Index Key	0000877860
Current Fiscal Year End Date	--12-31
Amendment Description	This Amendment No. 1 on Form 10-K/A (the “Amendment”) is filed by National Health Investors, Inc. ("NHI" or the “Company”) to amend its Annual Report on Form 10-K for the year ended December 31, 2019 (the “2019 Form 10-K”). The purpose of the Amendment is to (i) amend Part IV, Item 15 of the 2019 Form 10-K. No other items of the 2019 Form 10-K are amended in this Form 10-K/A.