LOANS (Summary of Modified Loans Resulting in Troubled Debt Restructurings) (Details) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($) Contract	Dec. 31, 2015 USD ($) Contract
Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]
Number of Contracts \| Contract	1	0
Pre-Modification Outstanding Recorded Investment	$ 826	$ 0
Post-Modification Outstanding Recorded Investment	$ 832	$ 0

Financing Receivable, Modifications, Subsequent Default, Pre-Modification Recorded Investment

No definition available.

Name:	acnb_FinancingReceivableModificationsSubsequentDefaultPreModificationRecordedInvestment
Namespace Prefix:	acnb_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableGrossAllowanceAndNetAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration