XML 56 R41.htm IDEA: XBRL DOCUMENT
v3.8.0.1

SECURITIES AVAILABLE FOR SALE, HELD TO MATURITY, AND OTHER - Narrative (Details) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 USD ($) security | Dec. 31, 2017 USD ($)
Investment Holdings [Line Items] |  |
Securities available for sale and other, at fair value | $ | $ 1,460,660 | $ 1,426,099
Municipal bonds and obligations |  |
Investment Holdings [Line Items] |  |
Available for sale and held to maturity securities, continuous unrealized loss position, aggregate losses (as percent) | 2.50% |
Held-to-maturity, securities in unrealized loss positions (security) | 73 |
Held-to-maturity securities portfolio, number of securities (security) | 227 |
Municipal bonds and obligations | Debt securities |  |
Investment Holdings [Line Items] |  |
Available-for-sale, securities in unrealized loss positions (security) | 13 |
Available for sale securities portfolio, number of securities (security) | 258 |
Available for sale and held to maturity securities, continuous unrealized loss position, aggregate losses (as percent) | 5.30% |
Agency collateralized mortgage obligations |  |
Investment Holdings [Line Items] |  |
Available for sale and held to maturity securities, continuous unrealized loss position, aggregate losses (as percent) | 4.10% |
Held-to-maturity, securities in unrealized loss positions (security) | 4 |
Held-to-maturity securities portfolio, number of securities (security) | 9 |
Agency collateralized mortgage obligations | Debt securities |  |
Investment Holdings [Line Items] |  |
Available-for-sale, securities in unrealized loss positions (security) | 229 |
Available for sale securities portfolio, number of securities (security) | 243 |
Available for sale and held to maturity securities, continuous unrealized loss position, aggregate losses (as percent) | 2.20% |
Mortgage-backed securities |  |
Investment Holdings [Line Items] |  |
Available for sale and held to maturity securities, continuous unrealized loss position, aggregate losses (as percent) | 4.50% |
Held-to-maturity, securities in unrealized loss positions (security) | 2 |
Held-to-maturity securities portfolio, number of securities (security) | 2 |
Mortgage-backed securities | Debt securities |  |
Investment Holdings [Line Items] |  |
Available-for-sale, securities in unrealized loss positions (security) | 73 |
Available for sale securities portfolio, number of securities (security) | 101 |
Available for sale and held to maturity securities, continuous unrealized loss position, aggregate losses (as percent) | 3.30% |
Corporate bonds | Debt securities |  |
Investment Holdings [Line Items] |  |
Available-for-sale, securities in unrealized loss positions (security) | 4 |
Available for sale securities portfolio, number of securities (security) | 20 |
Available for sale and held to maturity securities, continuous unrealized loss position, aggregate losses (as percent) | 0.20% |
Other bonds and obligations | Debt securities |  |
Investment Holdings [Line Items] |  |
Available-for-sale, securities in unrealized loss positions (security) | 6 |
Available for sale securities portfolio, number of securities (security) | 9 |
Available for sale and held to maturity securities, continuous unrealized loss position, aggregate losses (as percent) | 1.50% |
Tax advantaged economic development bonds |  |
Investment Holdings [Line Items] |  |
Available for sale and held to maturity securities, continuous unrealized loss position, aggregate losses (as percent) | 7.10% |
Held-to-maturity, securities in unrealized loss positions (security) | 3 |
Held-to-maturity securities portfolio, number of securities (security) | 7 |

X
- Definition Represents the aggregate unrealized losses, expressed as a percentage of the amortized cost of the securities in a continuous unrealized loss position categorized as held-to-maturity and available-for-sales securities. + References No definition available. + Details
Name: | bhlb_AvailableForSaleAndHeldToMaturitySecuritiesContinuousUnrealizedLossPositionAggregateLossesPercentage
Namespace Prefix: | bhlb_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of securities in the entity's portfolio of available-for-sale securities. + References No definition available. + Details
Name: | bhlb_AvailableForSaleSecuritiesPortfolioNumberOfSecurities
Namespace Prefix: | bhlb_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Held To Maturity Securities Portfolio Number of Securities + References No definition available. + Details
Name: | bhlb_HeldToMaturitySecuritiesPortfolioNumberofSecurities
Namespace Prefix: | bhlb_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562 + Details
Name: | us-gaap_AvailableForSaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 + Details
Name: | us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Disclosure regarding factors used to determine that the impairment of securities categorized as held-to-maturity where cost exceeds fair value is not an other than temporary impairment (OTTI). This item contains disclosure of the number of investment positions in the held-to-maturity investments determined to be temporarily impaired. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_InvestmentHoldingsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CollateralizedMortgageObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CorporateBondSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_OtherDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=bhlb_TaxAdvantagedEconomicDevelopmentBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |