Fair Value of Assets and Liabilities (FV on recurring or nonrecurring basis-level 3 inputs) (Details 3) $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Interest Rate Lock Commitments \| Pricing Model
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Interest Rate Derivative Instruments Not Designated as Hedging Instruments at Fair Value, Net	$ 1,280	$ 871
Interest Rate Swap Agreements \| Discounted Cash Flow
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Interest Rate Derivative Instruments Not Designated as Hedging Instruments at Fair Value, Net	$ 21,293	$ 3,545
Mortgage Servicing Rights \| Discounted Cash Flow
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Weighted Average Constant Prepayment Rate (as a percent)	10.76%	7.01%
Mortgage Servicing Rights, at Fair Value	$ 26,840	$ 30,508
boh_MeasurementInputClosingRatio [Member] \| Fair Value, Inputs, Level 3 [Member] \| Interest Rate Lock Commitments \| Pricing Model
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Derivative Asset (Liability) Net, Measurement Input	0.9224	0.8900
Measurement Input, Discount Rate [Member] \| Fair Value, Inputs, Level 3 [Member] \| Discounted Cash Flow
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Servicing Asset, Measurement Input	0.0733	0.0959
Measurement Input, Entity Credit Risk [Member] \| Fair Value, Inputs, Level 3 [Member] \| Interest Rate Swap Agreements \| Discounted Cash Flow
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Derivative Asset (Liability) Net, Measurement Input	0.0020	0.0006

Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs [Line Items]

No definition available.

Name:	boh_Level3AssetsandLiabilitiesFairValueandFairValueUnobservableInputsLineItems
Namespace Prefix:	boh_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the assets reported on a recurring or nonrecurring basis on the balance sheet at period end at fair value.

+ References

No definition available.

+ Details

Name:	boh_MortgageServicingRightsFairValueDisclosure
Namespace Prefix:	boh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Discount rate which is used to value residual cash flows generated by financial assets of the securitization, asset-backed financing arrangement, or similar transfer for initial fair value measurement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=118948506&loc=d3e107207-111719

+ Details

Name:	us-gaap_AssumptionForFairValueOnSecuritizationDateOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesDiscountRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Value of input used to measure net derivative asset (liability).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_DerivativeAssetLiabilityNetMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value as of the balance sheet date of all derivatives not designated as hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=117331979&loc=d3e41228-113958

+ Details

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

- Definition

Value of input used to measure servicing asset.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_ValuationTechniqueAxis=boh_PricingModelTechniqueMember
Namespace Prefix:
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationTechniqueAxis=boh_DiscountedCashFlowTechniqueMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
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- Details

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- Details

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- Details

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- Details

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