JUNIOR SUBORDINATED DEBENTURES - Boston Private Capital Trust II Terms (Details) - Boston Private Capital Trust II Junior Subordinated Debentures	12 Months Ended
Dec. 31, 2020 USD ($) payment	Dec. 31, 2019 USD ($)	Dec. 30, 2010
Debt Instrument [Line Items]
Debt face amount	$ 100,000,000
Debt stated interest rate			6.25%
Debt basis spread on variable rate	1.68%
Debt effective interest rate	1.92%
Assets Held-in-trust	$ 3,100,000	$ 3,100,000
Option to defer, number of quarterly payments \| payment	20

Debt Instrument, Option To Defer, Number Of Quarterly Payments

No definition available.

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- Definition

The total amount of cash and securities held by third party trustees pursuant to terms of debt instruments or other agreements as of the date of each statement of financial position presented, which can be used by the trustee only to pay the noncurrent portion of specified obligations.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(b))
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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
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-Subparagraph (SX 210.5-02.22(a)(1))
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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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- 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.

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