XML 64 R52.htm IDEA: XBRL DOCUMENT
v3.19.2

SECURITIES AVAILABLE FOR SALE, HELD TO MATURITY, AND MARKETABLE EQUITY SECURITIES - Summary of Securities with Unrealized Losses (Details) - USD ($) $ in Thousands | Jun. 30, 2019 | Dec. 31, 2018
--- | --- | ---
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, less than twelve months, gross unrealized losses | $ 515 | $ 1,576
Available for sale securities, over twelve months, gross unrealized losses | 3,303 | 24,115
Available for sale securities, continuous unrealized loss position, accumulated loss | 3,818 | 25,691
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available for sale securities, continuous unrealized loss position, less than twelve months, fair value | 90,256 | 130,805
Available for sale securities, continuous unrealized loss position, over twelve months, fair value | 287,645 | 992,767
Available for sale securities, continuous unrealized loss position, fair value | 377,901 | 1,123,572
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Held-to-maturity securities, continuous unrealized loss position, less than twelve months, accumulated loss | 0 | 192
Held-to-maturity securities, continuous unrealized loss position, over twelve months, gross unrealized losses | 1,435 | 6,471
Held to maturity securities, accumulated unrecognized holding loss | 1,435 | 6,663
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Held to maturity securities, accumulated unrecognized holding loss, less than twelve months, fair value | 0 | 25,674
Held to maturity securities, accumulated unrecognized holding loss, over twelve months, fair value | 24,078 | 170,459
Held to maturity securities, accumulated unrecognized holding loss, fair value | 24,078 | 196,133
Securities available for sale and held to maturity |  |
Held to maturity and available for sale securities continuous unrealized loss position, less than twelve months, aggregate losses | 515 | 1,768
Held to maturity and available for sale securities continuous unrealized loss position, less than twelve months, fair value | 90,256 | 156,479
Held to maturity and available for sale securities continuous unrealized loss position, over twelve months, aggregate losses | 4,738 | 30,586
Held to maturity and available for sale securities continuous unrealized loss position, over twelve months, fair value | 311,723 | 1,163,226
Held to maturity and available for sale securities continuous unrealized loss position, aggregate losses | 5,253 | 32,354
Held to maturity and available for sale securities continuous unrealized loss position, fair value | 401,979 | 1,319,705
Municipal bonds and obligations |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, less than twelve months, gross unrealized losses | 0 | 55
Available for sale securities, over twelve months, gross unrealized losses | 5 | 658
Available for sale securities, continuous unrealized loss position, accumulated loss | 5 | 713
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available for sale securities, continuous unrealized loss position, less than twelve months, fair value | 0 | 3,186
Available for sale securities, continuous unrealized loss position, over twelve months, fair value | 1,319 | 11,787
Available for sale securities, continuous unrealized loss position, fair value | 1,319 | 14,973
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Held-to-maturity securities, continuous unrealized loss position, less than twelve months, accumulated loss |  | 127
Held-to-maturity securities, continuous unrealized loss position, over twelve months, gross unrealized losses |  | 3,474
Held to maturity securities, accumulated unrecognized holding loss |  | 3,601
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Held to maturity securities, accumulated unrecognized holding loss, less than twelve months, fair value |  | 17,596
Held to maturity securities, accumulated unrecognized holding loss, over twelve months, fair value |  | 103,759
Held to maturity securities, accumulated unrecognized holding loss, fair value |  | 121,355
Agency collateralized mortgage obligations |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, less than twelve months, gross unrealized losses | 72 | 76
Available for sale securities, over twelve months, gross unrealized losses | 509 | 15,116
Available for sale securities, continuous unrealized loss position, accumulated loss | 581 | 15,192
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available for sale securities, continuous unrealized loss position, less than twelve months, fair value | 43,755 | 39,114
Available for sale securities, continuous unrealized loss position, over twelve months, fair value | 103,929 | 755,528
Available for sale securities, continuous unrealized loss position, fair value | 147,684 | 794,642
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Held-to-maturity securities, continuous unrealized loss position, less than twelve months, accumulated loss | 0 | 0
Held-to-maturity securities, continuous unrealized loss position, over twelve months, gross unrealized losses | 115 | 778
Held to maturity securities, accumulated unrecognized holding loss | 115 | 778
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Held to maturity securities, accumulated unrecognized holding loss, less than twelve months, fair value | 0 | 0
Held to maturity securities, accumulated unrecognized holding loss, over twelve months, fair value | 10,648 | 43,138
Held to maturity securities, accumulated unrecognized holding loss, fair value | 10,648 | 43,138
Agency mortgage-backed securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, less than twelve months, gross unrealized losses | 5 | 53
Available for sale securities, over twelve months, gross unrealized losses | 1,074 | 5,068
Available for sale securities, continuous unrealized loss position, accumulated loss | 1,079 | 5,121
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available for sale securities, continuous unrealized loss position, less than twelve months, fair value | 2,191 | 5,500
Available for sale securities, continuous unrealized loss position, over twelve months, fair value | 93,990 | 162,439
Available for sale securities, continuous unrealized loss position, fair value | 96,181 | 167,939
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Held-to-maturity securities, continuous unrealized loss position, less than twelve months, accumulated loss | 0 | 0
Held-to-maturity securities, continuous unrealized loss position, over twelve months, gross unrealized losses | 57 | 297
Held to maturity securities, accumulated unrecognized holding loss | 57 | 297
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Held to maturity securities, accumulated unrecognized holding loss, less than twelve months, fair value | 0 | 0
Held to maturity securities, accumulated unrecognized holding loss, over twelve months, fair value | 6,701 | 6,922
Held to maturity securities, accumulated unrecognized holding loss, fair value | 6,701 | 6,922
Agency commercial mortgage-backed securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, less than twelve months, gross unrealized losses | 0 | 44
Available for sale securities, over twelve months, gross unrealized losses | 1,089 | 3,231
Available for sale securities, continuous unrealized loss position, accumulated loss | 1,089 | 3,275
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available for sale securities, continuous unrealized loss position, less than twelve months, fair value | 0 | 1,503
Available for sale securities, continuous unrealized loss position, over twelve months, fair value | 55,319 | 57,422
Available for sale securities, continuous unrealized loss position, fair value | 55,319 | 58,925
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Held-to-maturity securities, continuous unrealized loss position, less than twelve months, accumulated loss |  | 0
Held-to-maturity securities, continuous unrealized loss position, over twelve months, gross unrealized losses |  | 289
Held to maturity securities, accumulated unrecognized holding loss |  | 289
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Held to maturity securities, accumulated unrecognized holding loss, less than twelve months, fair value |  | 0
Held to maturity securities, accumulated unrecognized holding loss, over twelve months, fair value |  | 10,128
Held to maturity securities, accumulated unrecognized holding loss, fair value |  | 10,128
Corporate bonds |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, less than twelve months, gross unrealized losses | 434 | 1,249
Available for sale securities, over twelve months, gross unrealized losses | 620 | 7
Available for sale securities, continuous unrealized loss position, accumulated loss | 1,054 | 1,256
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available for sale securities, continuous unrealized loss position, less than twelve months, fair value | 37,147 | 74,434
Available for sale securities, continuous unrealized loss position, over twelve months, fair value | 30,036 | 2,561
Available for sale securities, continuous unrealized loss position, fair value | 67,183 | 76,995
Trust preferred securities |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, less than twelve months, gross unrealized losses | 4 | 99
Available for sale securities, over twelve months, gross unrealized losses | 0 | 0
Available for sale securities, continuous unrealized loss position, accumulated loss | 4 | 99
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available for sale securities, continuous unrealized loss position, less than twelve months, fair value | 7,163 | 7,068
Available for sale securities, continuous unrealized loss position, over twelve months, fair value | 0 | 0
Available for sale securities, continuous unrealized loss position, fair value | 7,163 | 7,068
Other bonds and obligations |  |
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Available for sale securities, less than twelve months, gross unrealized losses | 0 | 0
Available for sale securities, over twelve months, gross unrealized losses | 6 | 35
Available for sale securities, continuous unrealized loss position, accumulated loss | 6 | 35
Debt Securities, Available-for-sale, Unrealized Loss Position [Abstract] |  |
Available for sale securities, continuous unrealized loss position, less than twelve months, fair value | 0 | 0
Available for sale securities, continuous unrealized loss position, over twelve months, fair value | 3,052 | 3,030
Available for sale securities, continuous unrealized loss position, fair value | 3,052 | 3,030
Tax advantaged economic development bonds |  |
Debt Securities, Held-to-maturity, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
Held-to-maturity securities, continuous unrealized loss position, less than twelve months, accumulated loss | 0 | 65
Held-to-maturity securities, continuous unrealized loss position, over twelve months, gross unrealized losses | 1,263 | 1,633
Held to maturity securities, accumulated unrecognized holding loss | 1,263 | 1,698
Debt Securities, Held-to-maturity, Continuous Unrealized Loss Position, Fair Value [Abstract] |  |
Held to maturity securities, accumulated unrecognized holding loss, less than twelve months, fair value | 0 | 8,078
Held to maturity securities, accumulated unrecognized holding loss, over twelve months, fair value | 6,729 | 6,512
Held to maturity securities, accumulated unrecognized holding loss, fair value | $ 6,729 | $ 14,590

X
- Definition Represents the aggregate fair value of investments in debt and equity securities categorized as held-to-maturity and available-for-sale that have been in a continuous unrealized loss position for twelve months or longer. + References No definition available. + Details
Name: | bhlb_DebtSecuritiesAvailableforsaleandHeldtomaturityContinuousUnrealizedLossPosition12MonthsorLonger
Namespace Prefix: | bhlb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the excess of amortized cost basis over the fair value of securities that have been in a loss position for twelve months or longer for those securities that are categorized as held-to-maturity and available-for-sale. + References No definition available. + Details
Name: | bhlb_DebtSecuritiesAvailableforsaleandHeldtomaturityContinuousUnrealizedLossPosition12MonthsorLongerAccumulatedLoss
Namespace Prefix: | bhlb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the aggregate fair value of investments in debt and equity securities categorized as held-to-maturity and available-for-sale that have been in a continuous unrealized loss position for less than twelve months. + References No definition available. + Details
Name: | bhlb_DebtSecuritiesAvailableforsaleandHeldtomaturityContinuousUnrealizedLossPositionLessthan12Months
Namespace Prefix: | bhlb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the excess of amortized cost basis over the fair value of securities that have been in a loss position for less than twelve months for those securities that are categorized as held-to-maturity and available-for-sale. + References No definition available. + Details
Name: | bhlb_DebtSecuritiesAvailableforsaleandHeldtomaturityContinuousUnrealizedLossPositionLessthan12MonthsAccumulatedLoss
Namespace Prefix: | bhlb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the aggregate fair value of investments in debt and equity securities in an unrealized loss position which are categorized as held-to-maturity and available-for-sale securities. + References No definition available. + Details
Name: | bhlb_DebtSecuritiesAvailableforsaleandHeldtomaturityUnrealizedLossPosition
Namespace Prefix: | bhlb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the excess of amortized cost basis over the fair value of securities that have been in a loss position, which are categorized as held-to-maturity and available-for-sale. + References No definition available. + Details
Name: | bhlb_DebtSecuritiesAvailableforsaleandHeldtomaturityUnrealizedLossPositionAccumulatedLoss
Namespace Prefix: | bhlb_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | bhlb_DebtSecuritivesHeldToMaturitySecuritiesandAvailableForSaleSecuritiesContinuousUnrealizedLossPositionAbstract
Namespace Prefix: | bhlb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGainLossAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118942371&loc=SL82922954-210456 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118942371&loc=SL82922954-210456 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922890-210455 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922888-210455 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118942371&loc=SL82922954-210456 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27290-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=118955579&loc=SL82922888-210455 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPositionAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27232-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for 12 months or longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27290-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionAccumulatedLossAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair value of investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27290-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionFairValueAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for less than 12 months. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27290-111563 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at amortized cost (held-to-maturity), in continuous unrealized loss position for less than 12 months. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of investment in debt security measured at amortized cost (held-to-maturity), in continuous unrealized loss position for 12 months or longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27337-111563 + Details
Name: | us-gaap_HeldToMaturitySecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

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

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
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_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
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: |