Investment Securities (Details) (USD $)	3 Months Ended
Mar. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Available-for-Sale:
Amortized Cost		$ 4,351,807,000	$ 6,457,151,000
Gross Unrealized Gains		100,807,000	109,238,000
Gross Unrealized Losses		(3,716,000)	(32,515,000)
Fair Value		4,448,898,000	6,533,874,000
Held-to-Maturity:
Amortized Cost		2,520,422,000	127,249,000
Gross Unrealized Gains		89,701,000	6,779,000
Gross Unrealized Losses		(42,000)
Fair Value		2,610,081,000	134,028,000
Reclassification at fair value in available-for-sale investment securities to the held-to-maturity category	2,200,000,000
Unrealized after-tax gains in accumulated other comprehensive income to be amortized over the estimated remaining life of the securities	8,200,000
Debt Securities Issued by the U.S. Treasury and Government Agencies
Available-for-Sale:
Amortized Cost		1,276,925,000	536,770,000
Gross Unrealized Gains		10,710,000	19,131,000
Gross Unrealized Losses		(1,039,000)	(45,000)
Fair Value		1,286,596,000	555,856,000
Held-to-Maturity:
Amortized Cost		179,481,000
Gross Unrealized Gains		6,601,000
Fair Value		186,082,000
Debt Securities Issued by States and Political Subdivisions
Available-for-Sale:
Amortized Cost		152,762,000	113,715,000
Gross Unrealized Gains		6,807,000	1,477,000
Gross Unrealized Losses		(1,000)	(1,583,000)
Fair Value		159,568,000	113,609,000
Debt Securities Issued by U.S. Government-Sponsored Enterprises
Available-for-Sale:
Amortized Cost			500,000
Gross Unrealized Gains			5,000
Fair Value			505,000
Debt Securities Issued by Corporations
Available-for-Sale:
Amortized Cost		133,670,000
Gross Unrealized Gains		481,000
Gross Unrealized Losses		(1,611,000)
Fair Value		132,540,000
Mortgage-backed Securities Issued by Government Agencies
Available-for-Sale:
Amortized Cost		2,721,303,000	5,696,907,000
Gross Unrealized Gains		79,394,000	84,008,000
Gross Unrealized Losses		(1,065,000)	(30,887,000)
Fair Value		2,799,632,000	5,750,028,000
Held-to-Maturity:
Amortized Cost		2,285,502,000	47,368,000
Gross Unrealized Gains		79,905,000	2,959,000
Gross Unrealized Losses		(42,000)
Fair Value		2,365,365,000	50,327,000
Mortgage-Backed Securities Issued by U.S. Government-Sponsored Enterprises
Available-for-Sale:
Amortized Cost		67,147,000	109,259,000
Gross Unrealized Gains		3,415,000	4,617,000
Fair Value		70,562,000	113,876,000
Held-to-Maturity:
Amortized Cost		55,439,000	79,881,000
Gross Unrealized Gains		3,195,000	3,820,000
Fair Value		58,634,000	83,701,000
Mortgage-Backed Securities
Available-for-Sale:
Amortized Cost		2,788,450,000	5,806,166,000
Gross Unrealized Gains		82,809,000	88,625,000
Gross Unrealized Losses		(1,065,000)	(30,887,000)
Fair Value		2,870,194,000	5,863,904,000
Held-to-Maturity:
Amortized Cost		2,340,941,000
Gross Unrealized Gains		83,100,000
Gross Unrealized Losses		(42,000)
Fair Value		$ 2,423,999,000

This item represents the unrealized gain (loss) recognized in other comprehensive income (a separate component of shareholders' equity) as a result of securities categorized as available-for-sale being transferred to the held-to-maturity securities category.

Name:	boh_AvailableForSaleSecuritiesTransferredToHeldToMaturitySecuritiesUnrealizedGainLoss
Namespace Prefix:	boh
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Unrealized holding gain (loss), net of tax, at the date of the transfer for a debt security from the available-for-sale category transferred into the held-to-maturity category. Also includes the unrealized gain (loss) at the date of transfer for a debt security from the held-to-maturity category transferred into the available-for-sale category.

+ Details

Name:	boh_OtherComprehensiveIncomeReclassificationAdjustmentForAvailableForSaleSecuritiesTransferredToHeldToMaturityNetOfTax
Namespace Prefix:	boh
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_AvailableForSaleSecuritiesAbstract
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6379932&loc=d3e22054-111558

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Available-for-Sale Securities

-URI http://asc.fasb.org/extlink&oid=6505594

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesFairValueDisclosure
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 22

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13, 19

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableforsaleSecuritiesGrossUnrealizedGain
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the gross unrealized losses for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLosses1
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This item represents the amortized cost, prior to other than temporary impairment (OTTI), of investments in debt securities which are categorized as held-to-maturity. The held-to-maturity category is for those securities that the entity has the positive intent and ability to hold until maturity. The temporary impairments arise from the unrealized losses that are recognized in AOCI.

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This item represents the aggregate fair value of investments in debt securities as of the balance sheet date and which are categorized as held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 19

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 137

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27232-111563

+ Details

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

- Details

Name:	us-gaap_HeldToMaturitySecuritiesUnclassifiedAbstract
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

As of the balance sheet date, the excess of fair value over carrying value (amortized cost) of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding gain.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 19

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 137

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27232-111563

+ Details

Name:	us-gaap_HeldtomaturitySecuritiesUnrecognizedHoldingGain
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

As of the balance sheet date, the excess of carrying value (amortized cost) over fair value of a debt security categorized as held-to-maturity, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 19

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 137

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6872113&loc=d3e27232-111563

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesUnrecognizedHoldingLoss
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant