Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Mar. 10, 2017	Jun. 30, 2016
Document and Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Entity Registrant Name	ACNB CORP
Entity Central Index Key	0000715579
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		6,064,138
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 147,984,103
Entity Voluntary Filers	No