[Line Items] for Basis Of Presentation And Significant Accounting Policies [Table]

No definition available.

Name:	bpfh_BasisOfPresentationAndSignificantAccountingPoliciesLineItems
Namespace Prefix:	bpfh_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Consolidated Entities

+ References

No definition available.

+ Details

Name:	bpfh_NumberOfConsolidatedEntities
Namespace Prefix:	bpfh_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Geographic Markets

+ References

No definition available.

+ Details

Name:	bpfh_NumberOfGeographicMarkets
Namespace Prefix:	bpfh_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Payments To Acquire Equity Securities, FV-NI

+ References

No definition available.

+ Details

Name:	bpfh_PaymentsToAcquireEquitySecuritiesFVNI
Namespace Prefix:	bpfh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Proceeds From The Sale Of Equity Securities, FV-NI

+ References

No definition available.

+ Details

Name:	bpfh_ProceedsFromTheSaleOfEquitySecuritiesFVNI
Namespace Prefix:	bpfh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

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

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

+ Details

Name:	us-gaap_OperatingLeaseLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's right to use underlying asset under operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977

+ Details

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

- Definition

Amount of cash outflow to acquire investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3151-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26853-111562

+ Details

Name:	us-gaap_PaymentsToAcquireAvailableForSaleSecuritiesDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26853-111562

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3151-108585

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3179-108585

+ Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=bpfh_PrivateBankingSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=bpfh_AffiliatePartnersSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201602Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RestatementAxis=srt_RestatementAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Basis of Presentation and Summary of Significant Accounting Policies (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($) segment affiliate market	Mar. 31, 2018 USD ($)	Dec. 31, 2017 segment	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Basis Of Presentation And Significant Accounting Policies [Line Items]
Lease liabilities	$ 120,162				$ 0
Number of reportable segments \| segment	3		4
ROU assets	$ 104,644				$ 0
Purchases, adjustment, securities available for sale	0	$ 9,985
Sales, adjustment, securities available for sale	0	24
Purchases, adjustment, equity securities at fair value	15,149	11,968
Sales, adjustment, equity securities at fair value	$ 21,886	$ 15,853
Private Banking
Basis Of Presentation And Significant Accounting Policies [Line Items]
Number of geographic markets \| market	3
Affiliate Partners
Basis Of Presentation And Significant Accounting Policies [Line Items]
Number of consolidated entities \| affiliate	4
ASU 2016-02
Basis Of Presentation And Significant Accounting Policies [Line Items]
Lease liabilities				$ 124,000
ROU assets				$ 108,000
Restatement Adjustment
Basis Of Presentation And Significant Accounting Policies [Line Items]
Purchases, adjustment, securities available for sale	$ (12,000)
Sales, adjustment, securities available for sale	$ (15,900)