Available commitments under revolving credit lines that have been modified as TDRs.

No definition available.

Name:	boh_AvailablecommitmentsunderRevolvingCreditLinesModifiedasTDR
Namespace Prefix:	boh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

CARES act maximum borrowing capacity under paycheck protection program loan.

+ References

No definition available.

+ Details

Name:	boh_CARESActMaximumBorrowingCapacityUnderPaycheckProtectionProgramLoan
Namespace Prefix:	boh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Period of modification related to loans that have been modified in a troubled debt restructuring where the balloon payment is extended.

+ References

No definition available.

+ Details

Name:	boh_ExtendingBalloonPayments
Namespace Prefix:	boh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the maximum current loan-to-value ratio for residential mortgage and home equity loans to be considered as pass.

+ References

No definition available.

+ Details

Name:	boh_FinancingReceivableCreditQualityCurrentLoanToValueRatioPercentageMaximum
Namespace Prefix:	boh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of days past due following modification of loans in a troubled debt restructuring, when a loan is considered to be in default.

+ References

No definition available.

+ Details

Name:	boh_FinancingReceivableModificationsMadeDefaultPeriod
Namespace Prefix:	boh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Financing receivable modified residential mortgage and or home equity loans maximum term categorized as classified credit quality indicator if principal and interest are current.

+ References

No definition available.

+ Details

Name:	boh_FinancingReceivableModifiedResidentialMortgageAndOrHomeEquityLoansMaximumTermCategorizedAsClassifiedCreditQualityIndicatorIfPrincipalAndInterestAreCurrent
Namespace Prefix:	boh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Financing receivable past due for loans and leases to be classified as classified credit quality indicator period.

+ References

No definition available.

+ Details

Name:	boh_FinancingReceivablePastDueForLoansAndLeasesToBeClassifiedAsClassifiedCreditQualityIndicatorPeriod
Namespace Prefix:	boh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Financing receivable recorded investment nonaccrual status current not past due period.

+ References

No definition available.

+ Details

Name:	boh_FinancingReceivableRecordedInvestmentNonaccrualStatusCurrentNotPastDuePeriod
Namespace Prefix:	boh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Financing Receivable, Reserve for Credit Losses, Additional Decrease in Cumulative Adjustment

+ References

No definition available.

+ Details

Name:	boh_FinancingReceivableReserveforCreditLossesAdditionalDecreaseinCumulativeAdjustment
Namespace Prefix:	boh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Loan and lease modifications amount.

+ References

No definition available.

+ Details

Name:	boh_LoanAndLeaseModificationsAmount
Namespace Prefix:	boh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of Loan and Lease Concessions

+ References

No definition available.

+ Details

Name:	boh_NumberofLoanandLeaseConcessions
Namespace Prefix:	boh_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of Paycheck Protection Loans

+ References

No definition available.

+ Details

Name:	boh_NumberofPaycheckProtectionLoans
Namespace Prefix:	boh_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of processing fees by small business administration.

+ References

No definition available.

+ Details

Name:	boh_PercentageOfProcessingFeesBySmallBusinessAdministration
Namespace Prefix:	boh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of Time Loan Being Fully Amortized

+ References

No definition available.

+ Details

Name:	boh_PeriodOfTimeLoanBeingFullyAmortized
Namespace Prefix:	boh_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Processing fee payment threshold limit of loan amount.

+ References

No definition available.

+ Details

Name:	boh_ProcessingFeePaymentThresholdLimitOfLoanAmount
Namespace Prefix:	boh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Revolving Loans, Converted To Term Loan During the Period

+ References

No definition available.

+ Details

Name:	boh_RevolvingLoansConvertedToTermLoanDuringthePeriod
Namespace Prefix:	boh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

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

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554

+ Details

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

- Definition

The gains (losses) included in earnings that represent the difference between the sale price and the carrying value of loans made to finance real estate acquisitions. This element refers to the gain (loss) and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121581245&loc=d3e21310-158488

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121581245&loc=d3e21286-158488

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=117337389&loc=d3e21493-158490

+ Details

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

- Definition

Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.8)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Definition

Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL49126937-111524

+ Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InternalCreditAssessmentAxis=us-gaap_SubstandardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201613Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CumulativeEffectPeriodOfAdoptionAxis=srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=boh_LandLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=boh_PaycheckProtectionLoansAdministeredBySBAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=boh_PaycheckProtectionProgramLoanProcessingFeesThresholdOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=boh_PaycheckProtectionProgramLoanProcessingFeesThresholdTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=boh_PaycheckProtectionProgramLoanProcessingFeesThresholdThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=boh_AccruedInterestReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Loans and Leases and the Allowance for Credit Losses - Additional Information (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($) Loan	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) Loan	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Loan and lease portfolio
Net gains related to sales of residential mortgage loans	$ 3,400,000	$ 2,500,000	$ 9,000,000.0	$ 4,100,000
Accrued interest receivable	$ 57,370,000		$ 57,370,000		$ 46,476,000
Number of paycheck protection loans \| Loan	4,504		4,504
Revolving loans, converted to term loan during the period			$ 1,500,000
Number of days non-accrual loans are not past due			30 days
Recorded Investment	$ 63,000,000.0		$ 63,000,000.0		69,100,000
Available commitments to lend additional funds on loans modified as TDR			200,000		300,000
Consumer mortgage loans collateralized by residential real estate property that are in the process of foreclosure	$ 1,100,000		$ 1,100,000
Consumer
Loan and lease portfolio
Number of loan and lease concessions - COVID-19 \| Loan	16,104		16,104
Loan and lease modifications, amount - COVID-19	$ 691,200,000		$ 691,200,000
Commercial
Loan and lease portfolio
Number of loan and lease concessions - COVID-19 \| Loan	674		674
Loan and lease modifications, amount - COVID-19	$ 836,700,000		$ 836,700,000
Classified
Loan and lease portfolio
Number of months up to which residential and home equity loans may be considered classified, even if they are current as to principal and interest			6 months
Classified \| Residential Mortgage
Loan and lease portfolio
Number of days past due for loans and leases in classified credit quality indicator			90 days
Maximum current loan-to-value ratio for residential mortgage and home equity loans to be considered as pass (as a percent)			60.00%
Classified \| Home Equity
Loan and lease portfolio
Number of days past due for loans and leases in classified credit quality indicator			90 days
Maximum current loan-to-value ratio for residential mortgage and home equity loans to be considered as pass (as a percent)			60.00%
Classified \| Consumer
Loan and lease portfolio
Number of days past due for loans and leases in classified credit quality indicator			90 days
Accounting Standards Update 2016-13 \| CECL Adoption Impact
Loan and lease portfolio
Additional decrease in cumulative adjustment	1,700,000		$ 1,700,000
Minimum
Loan and lease portfolio
Default period past due following modification of loans in TDR (in days)			60 days
Maximum \| Residential Mortgage
Loan and lease portfolio
Period of time loan being fully amortized			40 years
Maximum \| Land Loan
Loan and lease portfolio
Period of time loan being fully amortized			360 months
Extending balloon payments			5 years
PPP Loans, Administered by the SBA [Member]
Loan and lease portfolio
Maximum borrowing capacity under paycheck protection program loan	$ 10,000,000		$ 10,000,000
Loans interest rate	1.00%		1.00%
Long-term debt, gross	$ 544,500,000		$ 544,500,000
PPP Loans, Administered by the SBA [Member] \| Minimum
Loan and lease portfolio
Loans maturity period			2 years
PPP Loans, Administered by the SBA [Member] \| Maximum
Loan and lease portfolio
Loans maturity period			5 years
PPP Loan Processing Fees Threshold One
Loan and lease portfolio
Percentage of processing fees by SBA			5.00%
PPP Loan Processing Fees Threshold One \| Maximum
Loan and lease portfolio
Processing fee payment threshold limit of loan amount	350,000		$ 350,000
PPP Loan Processing Fees Threshold Two
Loan and lease portfolio
Percentage of processing fees by SBA			3.00%
PPP Loan Processing Fees Threshold Two \| Minimum
Loan and lease portfolio
Processing fee payment threshold limit of loan amount	350,000		$ 350,000
PPP Loan Processing Fees Threshold Two \| Maximum
Loan and lease portfolio
Processing fee payment threshold limit of loan amount	2,000,000		$ 2,000,000
PPP Loan Processing Fees Threshold Three
Loan and lease portfolio
Percentage of processing fees by SBA			1.00%
PPP Loan Processing Fees Threshold Three \| Minimum
Loan and lease portfolio
Processing fee payment threshold limit of loan amount	2,000,000		$ 2,000,000
Accrued Interest Receivable
Loan and lease portfolio
Accrued interest receivable	$ 42,700,000		$ 42,700,000		$ 30,700,000