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Benefit Plans - 401(k) Savings Plan (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
Salaries and employee benefits |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Employer contributions | $ 9.2 | $ 9.1 | $ 8.6
First Hawaiian, Inc. 401(k) Savings Plan | Maximum |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Employer contributions, as percentage of employee's pay | 5.00% | 5.00% | 5.00%
First Hawaiian, Inc. Future Plan |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Employer contributions, as percentage of employee's pay | 2.50% | 2.50% | 2.50%

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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