XML 34 R47.htm IDEA: XBRL DOCUMENT v2.4.1.9
LOAN LOSS ALLOWANCE (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Activity in the allowance for loan losses    
Balance at beginning of period $ 35,662us-gaap_LoansAndLeasesReceivableAllowance  
Provision for loan losses 3,851us-gaap_ProvisionForLoanAndLeaseLosses 3,396us-gaap_ProvisionForLoanAndLeaseLosses
Balance at end of period 36,286us-gaap_LoansAndLeasesReceivableAllowance  
Allowance For Loan Losses    
Total 36,286us-gaap_LoansAndLeasesReceivableAllowance  
Business Activity    
Activity in the allowance for loan losses    
Balance at beginning of period 32,795us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
29,527us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
Charged-off loans 2,158us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
1,984us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
Recoveries on charged-off loans 136us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
107us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
Provision for loan losses 1,495us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
1,728us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
Balance at end of period 32,268us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
29,378us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
Allowance For Loan Losses    
Individually evaluated for impairment 1,086us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
2,018us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
Collectively evaluated 31,182us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
27,360us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
Total 32,268us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
29,378us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
Acquired Loans    
Activity in the allowance for loan losses    
Balance at beginning of period 2,867us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
3,796us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
Charged-off loans 1,274us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
1,333us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
Recoveries on charged-off loans 69us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
93us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
Provision for loan losses 2,356us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
1,668us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
Balance at end of period 4,018us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
4,224us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
Allowance For Loan Losses    
Individually evaluated for impairment 568us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
301us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
Collectively evaluated 3,450us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
3,923us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
Total 4,018us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
4,224us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
Residential | Mortgages | Business Activity    
Activity in the allowance for loan losses    
Balance at beginning of period 6,836us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
6,937us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Charged-off loans 128us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
706us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Recoveries on charged-off loans 67us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
7us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Provision for loan losses (702)us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
(575)us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Balance at end of period 6,073us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
5,663us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Allowance For Loan Losses    
Individually evaluated for impairment   397us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Collectively evaluated 6,073us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
5,266us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Total 6,073us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
5,663us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Residential | Mortgages | Acquired Loans    
Activity in the allowance for loan losses    
Balance at beginning of period 615us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
625us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Charged-off loans 238us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
429us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Recoveries on charged-off loans   73us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Provision for loan losses 372us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
401us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Balance at end of period 749us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
670us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Allowance For Loan Losses    
Individually evaluated for impairment 52us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
30us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Collectively evaluated 697us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
640us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Total 749us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
670us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_MortgagesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialPortfolioSegmentMember
Commercial real estate | Business Activity    
Activity in the allowance for loan losses    
Balance at beginning of period 14,690us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
13,705us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Charged-off loans 1,605us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
660us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Recoveries on charged-off loans 3us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
1us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Provision for loan losses 1,330us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
1,900us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Balance at end of period 14,418us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
14,946us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Allowance For Loan Losses    
Individually evaluated for impairment 1,086us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
1,558us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Collectively evaluated 13,332us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
13,388us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Total 14,418us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
14,946us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Commercial real estate | Acquired Loans    
Activity in the allowance for loan losses    
Balance at beginning of period 790us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
2,339us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Charged-off loans 405us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
447us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Recoveries on charged-off loans   1us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Provision for loan losses 1,579us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
231us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Balance at end of period 1,964us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
2,124us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Allowance For Loan Losses    
Individually evaluated for impairment 455us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
250us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Collectively evaluated 1,509us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
1,874us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Total 1,964us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
2,124us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Commercial real estate | Business loans | Business Activity    
Activity in the allowance for loan losses    
Balance at beginning of period 5,206us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
5,173us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Charged-off loans 223us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
189us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Recoveries on charged-off loans 5us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
20us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Provision for loan losses 1,460us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
(185)us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Balance at end of period 6,448us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
4,819us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Allowance For Loan Losses    
Individually evaluated for impairment   54us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Collectively evaluated 6,448us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
4,765us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Total 6,448us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
4,819us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Commercial real estate | Business loans | Acquired Loans    
Activity in the allowance for loan losses    
Balance at beginning of period 1,093us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
597us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Charged-off loans 198us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
52us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Recoveries on charged-off loans 41us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
5us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Provision for loan losses (11)us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
548us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Balance at end of period 925us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
1,098us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Allowance For Loan Losses    
Individually evaluated for impairment   21us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Collectively evaluated 925us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
1,077us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Total 925us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
1,098us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancialInstrumentAxis
= us-gaap_CommercialLoanMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Consumer | Business Activity    
Activity in the allowance for loan losses    
Balance at beginning of period 5,928us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
3,644us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Charged-off loans 202us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
429us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Recoveries on charged-off loans 61us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
79us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Provision for loan losses (751)us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
836us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Balance at end of period 5,036us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
4,130us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Allowance For Loan Losses    
Individually evaluated for impairment   9us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Collectively evaluated 5,036us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
4,121us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Total 5,036us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
4,130us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Consumer | Acquired Loans    
Activity in the allowance for loan losses    
Balance at beginning of period 369us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
235us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Charged-off loans 433us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
405us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Recoveries on charged-off loans 28us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
14us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Provision for loan losses 416us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
488us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Balance at end of period 380us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
332us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Allowance For Loan Losses    
Individually evaluated for impairment 61us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
 
Collectively evaluated 319us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
332us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Total 380us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
332us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansAcquiredFromBusinessCombinationsMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Unallocated | Business Activity    
Activity in the allowance for loan losses    
Balance at beginning of period 135us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
68us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
Provision for loan losses 158us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
(248)us-gaap_ProvisionForLoanAndLeaseLosses
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
Balance at end of period 293us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
(180)us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
Allowance For Loan Losses    
Collectively evaluated 293us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
(180)us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
Total $ 293us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember
$ (180)us-gaap_LoansAndLeasesReceivableAllowance
/ bhlb_AccountsNotesLoansAndFinancingReceivableBySourceAxis
= bhlb_LoansFromBusinessActivitiesMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_UnallocatedFinancingReceivablesMember