Investment Securities - Schedule of Amortized Cost, Gross Unrealized Gains and Losses, and Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Available-for-Sale:
Available-for-Sale: Amortized Cost	$ 3,111,239	$ 2,947,415
Available-for-Sale: Gross Unrealized Gains	2,303	1,248
Available-for-Sale: Gross Unrealized Losses	(226,523)	(259,135)
Available-for-Sale: Fair Value	2,887,019	2,689,528
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	4,535,108	4,618,543
Held-to-Maturity: Gross Unrealized Gains	52	40
Held-to-Maturity: Gross Unrealized Losses	(711,505)	(797,701)
Held-to-Maturity: Fair Value	3,823,655	3,820,882
Debt Securities Issued by the U.S. Treasury and Government Agencies
Available-for-Sale:
Available-for-Sale: Amortized Cost	233,515	257,036
Available-for-Sale: Gross Unrealized Gains	149	221
Available-for-Sale: Gross Unrealized Losses	(6,268)	(8,185)
Available-for-Sale: Fair Value	227,396	249,072
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	131,900	131,868
Held-to-Maturity: Gross Unrealized Losses	(12,329)	(14,927)
Held-to-Maturity: Fair Value	119,571	116,941
Debt Securities Issued by States and Political Subdivisions
Available-for-Sale:
Available-for-Sale: Amortized Cost	72,968	73,208
Available-for-Sale: Gross Unrealized Losses	(7,972)	(9,349)
Available-for-Sale: Fair Value	64,996	63,859
Debt Securities Issued by Government-Sponsored Enterprises
Available-for-Sale:
Available-for-Sale: Amortized Cost	1,365	1,505
Available-for-Sale: Gross Unrealized Losses	(29)	(41)
Available-for-Sale: Fair Value	1,336	1,464
Debt Securities Issued by Corporations
Available-for-Sale:
Available-for-Sale: Amortized Cost	728,334	703,579
Available-for-Sale: Gross Unrealized Gains	667	376
Available-for-Sale: Gross Unrealized Losses	(28,529)	(32,280)
Available-for-Sale: Fair Value	700,472	671,675
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	10,422	10,490
Held-to-Maturity: Gross Unrealized Losses	(1,905)	(2,156)
Held-to-Maturity: Fair Value	8,517	8,334
Residential - Government Agencies or Sponsored Enterprises
Available-for-Sale:
Available-for-Sale: Amortized Cost	1,110,283	1,050,299
Available-for-Sale: Gross Unrealized Gains	716	322
Available-for-Sale: Gross Unrealized Losses	(102,495)	(115,401)
Available-for-Sale: Fair Value	1,008,504	935,220
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	2,142,080	2,185,210
Held-to-Maturity: Gross Unrealized Gains	4	3
Held-to-Maturity: Gross Unrealized Losses	(338,686)	(377,149)
Held-to-Maturity: Fair Value	1,803,398	1,808,064
Commercial - Government Agencies or Sponsored Enterprises
Available-for-Sale:
Available-for-Sale: Amortized Cost	330,746	306,696
Available-for-Sale: Gross Unrealized Gains	265	199
Available-for-Sale: Gross Unrealized Losses	(21,961)	(23,421)
Available-for-Sale: Fair Value	309,050	283,474
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	414,089	416,389
Held-to-Maturity: Gross Unrealized Losses	(84,927)	(92,211)
Held-to-Maturity: Fair Value	329,162	324,178
Collateralized Mortgage Obligations
Available-for-Sale:
Available-for-Sale: Amortized Cost	1,441,029	1,356,995
Available-for-Sale: Gross Unrealized Gains	981	521
Available-for-Sale: Gross Unrealized Losses	(124,456)	(138,822)
Available-for-Sale: Fair Value	1,317,554	1,218,694
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	2,556,169	2,601,599
Held-to-Maturity: Gross Unrealized Gains	4	3
Held-to-Maturity: Gross Unrealized Losses	(423,613)	(469,360)
Held-to-Maturity: Fair Value	2,132,560	2,132,242
Residential - Government Agencies or Sponsored Enterprises
Available-for-Sale:
Available-for-Sale: Amortized Cost	634,028	555,092
Available-for-Sale: Gross Unrealized Gains	506	130
Available-for-Sale: Gross Unrealized Losses	(59,269)	(70,458)
Available-for-Sale: Fair Value	575,265	484,764
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	1,826,625	1,864,591
Held-to-Maturity: Gross Unrealized Gains	48	37
Held-to-Maturity: Gross Unrealized Losses	(271,727)	(309,093)
Held-to-Maturity: Fair Value	1,554,946	1,555,535
Commercial - Government Agencies or Sponsored Enterprises
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	9,992	9,995
Held-to-Maturity: Gross Unrealized Losses	(1,931)	(2,165)
Held-to-Maturity: Fair Value	8,061	7,830
Mortgage-Backed Securities
Available-for-Sale:
Available-for-Sale: Amortized Cost	634,028	555,092
Available-for-Sale: Gross Unrealized Gains	506	130
Available-for-Sale: Gross Unrealized Losses	(59,269)	(70,458)
Available-for-Sale: Fair Value	575,265	484,764
Held-to-Maturity:
Held-to-Maturity: Amortized Cost	1,836,617	1,874,586
Held-to-Maturity: Gross Unrealized Gains	48	37
Held-to-Maturity: Gross Unrealized Losses	(273,658)	(311,258)
Held-to-Maturity: Fair Value	$ 1,563,007	$ 1,563,365

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

+ Details

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

- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

+ Details

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

- References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesFairValueToAmortizedCostBasisAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, 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://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

+ Details

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

- Definition

Amount excluding accrued interest, 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://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

+ Details

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

- Definition

Amount excluding accrued interest, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-3B

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-5

+ Details

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

- References

No definition available.

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5A
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-5A

+ Details

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

- 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/otherTransitionRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5A
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-5A

+ Details

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

- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2E

Reference 3: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-5

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-5A

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

+ Details

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=boh_ResidentialCollateralizedMortgageObligationsIssuedByGovernmentAgenciesOrSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=boh_CommercialCollateralizedMortgageObligationsIssuedByGovernmentAgenciesOrSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CollateralizedMortgageObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=boh_ResidentialMortgageBackedSecuritiesIssuedByGovernmentAgenciesOrSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=boh_CommercialMortgageBackedSecuritiesIssuedByGovernmentAgenciesOrSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: