Forebearance Agreement, Number Of Negotiations

No definition available.

Name:	acnb_ForebearanceAgreementNumberOfNegotiations
Namespace Prefix:	acnb_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Forebearance Agreements Modified, Number of Modified

+ References

No definition available.

+ Details

Name:	acnb_ForebearanceAgreementsModifiedNumberOfModified
Namespace Prefix:	acnb_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancingReceivableModificationsLineItems
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=7512638&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of investment in financing receivables (after modification) modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in financing receivables (before modification) modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of the outstanding recorded investment related to 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 40

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6951948&loc=d3e18845-111554

+ Details

Name:	us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and 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=7512638&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

For a debtor, the aggregate gain (loss) recognized on the restructuring of payables arises from the difference between the book value of the debt before the restructuring and the fair value of the payments on the debt after restructuring is complete.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 60

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6402221&loc=d3e15743-112638

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 15

-Paragraph 25

-Subparagraph b

-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.

+ Details

Name:	us-gaap_GainsLossesOnRestructuringOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Loans (Troubled Debt Restructurings) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2012 loan	Dec. 31, 2011 loan	Dec. 31, 2010 loan	Dec. 31, 2009 loan
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments		$ 8,255	$ 2,694
Post-Modification Outstanding Recorded Investments		8,243	2,682
Recorded Investment		6,715	1,496
Gains (Losses) on Restructuring of Debt	39		589
Forebearance Agreement, Number Of Negotiations		3	1	2	1
Forebearance Agreements Modified, Number of Modified			1
Financing Receivable, Modifications, Subsequent Default, Number of Contracts		0
Commercial real estate [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts		2
Pre-Modification Outstanding Recorded Investments		5,225
Post-Modification Outstanding Recorded Investments		5,225
Recorded Investment		5,099
Residential mortgage [Member]
Financing Receivable, Modifications [Line Items]
Number of Contracts		1
Pre-Modification Outstanding Recorded Investments		336
Post-Modification Outstanding Recorded Investments		336
Recorded Investment		321
Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments		3,342
Post-Modification Outstanding Recorded Investments		3,330
Recorded Investment		1,900
Nonaccrual [Member] \| Commercial and industrial [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments		490	490
Post-Modification Outstanding Recorded Investments		485	485
Recorded Investment		187	234
Nonaccrual [Member] \| Commercial real estate [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments		1,304	656
Post-Modification Outstanding Recorded Investments		1,304	656
Recorded Investment		953	412
Nonaccrual [Member] \| Commercial real estate construction [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments		1,548	1,548
Post-Modification Outstanding Recorded Investments		1,541	1,541
Recorded Investment		760	850
Accrual [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments		4,913
Post-Modification Outstanding Recorded Investments		4,913
Recorded Investment		4,815
Accrual [Member] \| Commercial real estate [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments		4,577
Post-Modification Outstanding Recorded Investments		4,577
Recorded Investment		4,494
Accrual [Member] \| Residential mortgage [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments		336
Post-Modification Outstanding Recorded Investments		336
Recorded Investment		$ 321