Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 01, 2019
Document and Entity Information [Abstract]
Entity Registrant Name	AMERICAN NATIONAL BANKSHARES INC.
Entity Central Index Key	0000741516
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding (in shares)		11,113,336
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Emerging Growth Company	false
Small Business	true
Entity Shell Company	false