Document and Entity Information - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Mar. 01, 2019	Jun. 30, 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 Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Emerging Growth Company	false
Entity Small Business	false
Entity Public Float			$ 321,345
Entity Common Stock, Shares Outstanding		8,756,569
Entity Shell Company	false
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018