2.4.0.82410402 - Disclosure - Securities Sold Under Agreements to Repurchase ("Repurchase Agreements") (Schedule of Repurchase Agreements) (Details)truefalseIn Thousands, unless otherwise specifiedfalse1false USDfalsefalse$I2013Q2http://www.sec.gov/CIK0000715579instant2013-06-30T00:00:000001-01-01T00:00:00usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$2false USDfalsefalse$I2012Q4http://www.sec.gov/CIK0000715579instant2012-12-31T00:00:000001-01-01T00:00:00usdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$1true 1us-gaap_DisclosureOfRepurchaseAgreementsAbstractus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Disclosure of Repurchase Agreements [Abstract]2false 2acnb_AssetsSoldUnderAgreementsToRepurchaseGrossAmountsacnb_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse5125000051250[1]USD$falsetruefalse2truefalsefalse4730300047303[1]USD$falsetruefalsexbrli:monetaryItemTypemonetaryAssets Sold Under Agreements To Repurchase Gross AmountsNo definition available.false2Gross Amounts of Recognized Liabilities3false 2us-gaap_AssetsSoldUnderAgreementsToRepurchaseCarryingAmountsus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse5125000051250[1]falsefalsefalse2truefalsefalse4730300047303[1]falsefalsefalsexbrli:monetaryItemTypemonetaryCarrying amount of assets sold under agreements to repurchase when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under repurchase agreements exceeds 10 percent of total assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(m)(1)(i)(A)(i)) -URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph m -Subparagraph 1 -Article 4 false2Net Amounts of Liabilities Presented in the Statements of Condition4false 2acnb_SecuritiesSoldUnderAgreementsToRepurchaseNotOffsetAgainstReverseReposacnb_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsetruenegatedLabel1truefalsefalse-51250000-51250[1]falsefalsefalse2truefalsefalse-47303000-47303[1]falsefalsefalsexbrli:monetaryItemTypemonetarySecurities Sold Under Agreements To Repurchase Not Offset Against Reverse ReposNo definition available.false2Gross Amounts Not offset in the Statements of Condition - Financial Instruments5false 2us-gaap_PledgedAssetsSeparatelyReportedSecuritiesPledgedForRepurchaseAgreementsAtFairValueus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse5738900057389USD$falsetruefalse2truefalsefalse5639200056392USD$falsetruefalsexbrli:monetaryItemTypemonetaryThe fair value, as of the date of each statement of financial position presented, of securities which are owned but transferred to serve as collateral for the payment of repurchase agreements, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6467456&loc=d3e113888-111728 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 140 -Paragraph 15 -Subparagraph a -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Pledged Assets Separately Reported, Securities Pledged for Repurchase Agreements, at Fair Value1As of June 30, 2013 and December 31, 2012, the fair value of securities pledged in connection with repurchase agreements was $57,389 and $56,392, respectively.falseSecurities Sold Under Agreements to Repurchase ("Repurchase Agreements") (Schedule of Repurchase Agreements) (Details) (USD $)ThousandsUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.acnb.com/role/SecuritiesSoldUnderAgreementsToRepurchaseRepurchaseAgreementsScheduleOfRepurchaseAgreementsDetails25