Forbearance Agreement, Number Of Expirations

No definition available.

Name:	acnb_ForbearanceAgreementNumberOfExpirations
Namespace Prefix:	acnb_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Forbearance Agreement, Number Of Negotiations

+ References

No definition available.

+ Details

Name:	acnb_ForbearanceAgreementNumberOfNegotiations
Namespace Prefix:	acnb_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Forbearance Agreements Modified, Number of Modified

+ References

No definition available.

+ Details

Name:	acnb_ForbearanceAgreementsModifiedNumberofModified
Namespace Prefix:	acnb_
Data Type:	xbrli:integerItemType
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=49124121&loc=SL6953676-111524

+ Details

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

- Definition

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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=25495931&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=49124121&loc=SL6953682-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
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

+ Details

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

- Definition

Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 35

-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL49126937-111524

+ Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=acnb_AccrualMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=acnb_NonaccrualMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Loans (Troubled Debt Restructurings) (Details) (USD $)	3 Months Ended		12 Months Ended
Loans (Troubled Debt Restructurings) (Details) (USD $)	Mar. 31, 2015 Contract	Mar. 31, 2014 Contract	Dec. 31, 2014	Dec. 31, 2013 Contract	Dec. 31, 2012 Contract	Dec. 31, 2011 Contract
Financing Receivable, Modifications [Line Items]
Troubled debt restructured loan defaulted, number of contracts	0	0
Forbearance Agreements Modified, Number of Modified				2		1
Pre-Modification Outstanding Recorded Investments	$ 10,513,000		$ 10,513,000
Post-Modification Outstanding Recorded Investments	10,553,000		10,553,000
Recorded Investment	7,706,000		7,834,000
Forbearance Agreement, Number Of Negotiations				1	3
Mortgage Loans in Process of Foreclosure, Amount	1,119,000		568,000
Forbearance Agreement, Number Of Expirations	2
Troubled debt restructured loan defaulted, amount		0
Financing Receivable, Modifications, Number of Contracts	1
Accrual [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments	7,454,000		7,454,000
Post-Modification Outstanding Recorded Investments	7,506,000		7,506,000
Recorded Investment	6,924,000		6,968,000
Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments	3,059,000		3,059,000
Post-Modification Outstanding Recorded Investments	3,047,000		3,047,000
Recorded Investment	782,000		866,000
Commercial and industrial [Member] \| Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments	490,000		490,000
Post-Modification Outstanding Recorded Investments	485,000		485,000
Recorded Investment	23,000		46,000
Commercial real estate [Member] \| Accrual [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments	7,118,000		7,118,000
Post-Modification Outstanding Recorded Investments	7,170,000		7,170,000
Recorded Investment	6,633,000		6,674,000
Commercial real estate [Member] \| Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments	1,021,000		1,021,000
Post-Modification Outstanding Recorded Investments	1,021,000		1,021,000
Recorded Investment	525,000		546,000
Commercial real estate construction [Member] \| Nonaccrual [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments	1,548,000		1,548,000
Post-Modification Outstanding Recorded Investments	1,541,000		1,541,000
Recorded Investment	234,000		274,000
Residential mortgage [Member] \| Accrual [Member]
Financing Receivable, Modifications [Line Items]
Pre-Modification Outstanding Recorded Investments	336,000		336,000
Post-Modification Outstanding Recorded Investments	336,000		336,000
Recorded Investment	$ 291,000		$ 294,000