Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2023	Aug. 09, 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	Q2
Document Fiscal Year Focus	2023
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 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 Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		5,891,739