Fair Value of Assets and Liabilities (FV on recurring or nonrecurring basis-level 3 inputs) (Details 3) $ in Thousands	Sep. 30, 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	$ 2,788	$ 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	29,123	3,545
Mortgage Servicing Rights \| Discounted Cash Flow
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Mortgage Servicing Rights, at Fair Value	$ 24,848	$ 30,508
Significant Other Unobservable Inputs (Level 3) \| Interest Rate Lock Commitments \| Pricing Model \| Weighted Average Closing Ratio (as a percent)
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Fair Value Inputs	0.9187	0.8900
Significant Other Unobservable Inputs (Level 3) \| Interest Rate Swap Agreements \| Discounted Cash Flow \| Weighted Average Credit Factor (as a percent)
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Interest Rate Derivative Instruments Not Designated as Hedging Instruments, Fair Value Inputs	0.0020	0.0006
Significant Other Unobservable Inputs (Level 3) \| Mortgage Servicing Rights \| Discounted Cash Flow \| Weighted Average Constant Prepayment Rate (as a percent)
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Mortgage Servicing Rights, Fair Value Inputs	0.1181	0.0701
Significant Other Unobservable Inputs (Level 3) \| Weighted Average Discount Rate (as a percent) \| Discounted Cash Flow \| Weighted Average Discount Rate (as a percent)
Level 3 Assets and Liabilities, Fair Value and Fair Value Unobservable Inputs
Mortgage Servicing Rights, Fair Value Inputs	0.0696	0.0959

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

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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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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