Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 26, 2018
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		8,714,431
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Emerging Growth Company	false
Small Business	false