Derivative Financial Instruments (Notional Amounts) (Details 1) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Interest Rate Lock Commitments
Derivative [Line Items]
Notional Amount	$ 110,702	$ 33,133
Fair Value	2,788	871
Forward Commitments
Derivative [Line Items]
Notional Amount	130,815	34,102
Fair Value	201	(352)
Receive Fixed / Pay Variable Swap
Derivative [Line Items]
Notional Amount	763,316	505,034
Fair Value	37,289	(2,537)
Pay Fixed / Receive Variable Swap
Derivative [Line Items]
Notional Amount	763,316	505,034
Fair Value	(8,166)	6,082
Foreign Exchange Contracts
Derivative [Line Items]
Notional Amount	72,683	55,663
Fair Value	(405)	793
Visa Conversion Rate Swap Agreement
Derivative [Line Items]
Notional Amount	104,816	80,746
Fair Value	$ (453)	$ 0

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

+ Details

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

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

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateLockCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForwardContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=boh_ReceiveFixedOrPayVariableSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=boh_PayFixedOrReceiveVariableSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=boh_VisaConversionRateSwapAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: