Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2023	Mar. 18, 2024	Jun. 30, 2023
Document Information [Line Items]
Entity Central Index Key	0000796534
Entity Registrant Name	NATIONAL BANKSHARES INC
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2023
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	0-15204
Entity Incorporation, State or Country Code	VA
Entity Tax Identification Number	54-1375874
Entity Address, Address Line One	101 Hubbard Street
Entity Address, City or Town	Blacksburg
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	24062-9002
City Area Code	540
Local Phone Number	951-6300
Title of 12(b) Security	Common Stock, par value $1.25 per share
Trading Symbol	NKSH
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 171,979,867
Entity Common Stock, Shares Outstanding		5,893,782
Auditor Name	Yount, Hyde & Barbour, P.C.
Auditor Firm ID	613
Auditor Location	Winchester, Virginia