Organization and Basis of Presentation (Policies)	3 Months Ended
Organization and Basis of Presentation (Policies)	Mar. 31, 2018
Organization and Basis of Presentation
Organization and Basis of Presentation	Organization and Basis of Presentation First Hawaiian, Inc. (“FHI” or the “Parent”), a bank holding company, owns 100% of the outstanding common stock of First Hawaiian Bank (“FHB” or the “Bank”), its only direct, wholly-owned subsidiary. FHI is a majority-owned, indirect subsidiary of BNP Paribas (“BNPP”), a financial institution based in France. The accompanying unaudited interim consolidated financial statements of First Hawaiian, Inc. and the Bank (the “Company”) have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. The accompanying unaudited interim consolidated financial statements and notes thereto should be read in conjunction with the Company’s audited consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. In the opinion of management, all adjustments, which consist of normal recurring adjustments necessary for a fair presentation of the interim period consolidated financial information, have been made. Results of operations for interim periods are not necessarily indicative of results to be expected for the entire year. Intercompany account balances and transactions have been eliminated in consolidation.
Reorganization Transactions	Reorganization Transactions In connection with FHI’s initial public offering (“IPO”) in August 2016, in which BNPP sold approximately 17% of its interest in FHI, BNPP announced its intent to sell a controlling interest in FHI, including its wholly-owned subsidiary FHB, over time, subject to market conditions and other considerations. On April 1, 2016, a series of reorganization transactions (the “Reorganization Transactions”) were undertaken to facilitate the IPO. As part of the Reorganization Transactions, FHI, which was then known as BancWest Corporation (“BancWest”), formed a new bank holding company, BancWest Holding Inc. (“BWHI”), a Delaware corporation and a direct wholly‑owned subsidiary of BancWest, and contributed 100% of its interest in Bank of the West (“BOW”), as well as other assets and liabilities not related to FHB, to BWHI. Following the contribution of BOW to BWHI, BancWest distributed its interest in BWHI to BNPP. As part of these transactions, BancWest amended its certificate of incorporation to change its name to “First Hawaiian, Inc.”, with First Hawaiian Bank remaining as the only direct wholly-owned subsidiary of FHI. On July 1, 2016, in order to comply with the Board of Governors of the Federal Reserve System’s requirement (under Regulation YY) applicable to BNPP that a foreign banking organization with $50 billion or more in U.S. non-branch assets as of June 30, 2015 establish a U.S. intermediate holding company and hold its interest in the substantial majority of its U.S. subsidiaries through the intermediate holding company by July 1, 2016, FHI became an indirect subsidiary of BNP Paribas USA, Inc. (“BNP Paribas USA”), BNPP’s U.S. intermediate holding company. As part of that reorganization, FHI became a direct wholly-owned subsidiary of BancWest Corporation (“BWC”), a direct wholly-owned subsidiary of BNP Paribas USA. On August 4, 2016, FHI’s common stock began trading on the NASDAQ Global Select Market (“NASDAQ”) under the ticker symbol “FHB”. On August 9, 2016, the IPO of 24,250,000 shares of FHI common stock, which included the full exercise of the underwriters’ option to purchase an additional 3,163,043 shares, at $23.00 per share were completed. On February 17, 2017, a second offering of 28,750,000 shares of FHI common stock, which included the full exercise of the underwriters’ option to purchase an additional 3,750,000 shares, at $32.00 per share was completed. FHI did not receive any of the proceeds from the sales of shares by BNPP. Following the secondary offering and exercise of the underwriters’ option to purchase additional shares in February 2017, BNPP beneficially owned approximately 62% of FHI’s outstanding common stock. BNPP continued to beneficially own approximately 62% of FHI’s outstanding common stock as of March 31, 2018.
Use of Estimates in the Preparation of Financial Statements	Use of Estimates in the Preparation of Financial Statements The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Management bases its estimates on historical experience and various other assumptions believed to be reasonable. Although these estimates are based on management’s best knowledge of current events, actual results may differ from these estimates.
Correction of an Immaterial Error to the Financial Statements	Correction of an Immaterial Error to the Financial Statements Subsequent to the issuance of the Company’s unaudited interim September 30, 2017 consolidated financial statements, the Company’s management determined that certain expenses related to card rewards program were incorrectly offset against credit and debit card fee income and credit card interchange assessment fees were incorrectly classified in card rewards program expense versus credit and debit card fee income in the consolidated statements of income for the three months ended March 31, 2017. For the three months ended March 31, 2017, income from service charges on deposit accounts was overstated by $0.1 million, credit and debit card fee income was understated by $1.8 million, occupancy expense was understated by $0.4 million and card rewards program expense was understated by $1.3 million. As a result, certain noninterest income and noninterest expense amounts have been restated from the amounts previously reported to correct the classification errors. There was no change to net income or earnings per share as previously reported as a result of these errors. Management has evaluated the materiality of these errors on its prior period financial statements from a quantitative and qualitative perspective, and has concluded that these errors were not material to the prior period.
Accounting Standard Adopted in 2018 and Recent Accounting Pronouncements	Accounting Standards Adopted in 2018 In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606). This guidance requires entities to recognize revenues when they transfer promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The Company adopted the provisions of ASU No. 2014-09 on January 1, 2018. The Company adopted the new guidance using the modified retrospective transition approach, in which the guidance would only be applied to existing contracts in effect at January 1, 2018 and new contracts entered into after this date. Most of the Company’s revenue is comprised of net interest income on loans, leases, investment securities and deposits, and is explicitly out of scope of the new revenue recognition guidance. Management conducted an assessment of the revenue streams that were potentially affected by the new guidance and reviewed contracts in scope to ensure compliance with the new guidance. These contracts included those related to credit and debit card fees, service charges and fees on deposit accounts and trust and investment services fees. The adoption of ASU No. 2014-09 did not have a material impact on the Company’s consolidated financial statements. However, additional disclosures required by the standard have been included in “Note 13. Revenue from Contracts with Customers” to the Company’s consolidated financial statements. In March 2017, the FASB issued ASU No. 2017-07, Compensation – Retirement Benefits (Topic 715), Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. This guidance requires entities to report the service cost component of net periodic benefit cost in the same line item as other compensation costs arising from services rendered by pertinent employees during the reporting period. The other components of net periodic benefit costs are to be presented in the income statement separately from the service cost component. The Company adopted the provisions of ASU No. 2017-07 on January 1, 2018 and applied the guidance retrospectively to all periods for which a statement of income is presented. The Company continues to record the service cost component of net periodic benefit cost in salaries and employee benefits; however, all other components of net periodic benefit cost is now recorded in other noninterest expense. The Company elected to use the practical expedient which permits entities to estimate amounts for comparative periods using the information previously disclosed in the Company’s pension and other postretirement benefit plan disclosure as such amounts are not material. The adoption of ASU No. 2017-07 did not have a material impact on the Company’s consolidated financial statements. See “Note 15. Benefit Plans” for required disclosures. In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718), Scope of Modification Accounting. This guidance applies to entities that change the terms or conditions of a share-based payment award. This guidance clarifies when an entity should account for a change as a modification. Modification accounting will be required only if the fair value, the vesting conditions or the classification of the award (as equity or liability) changes as a result of the change in terms or conditions. The Company adopted the provisions of ASU No. 2017-09 on January 1, 2018. The adoption of ASU No. 2017-09 did not have a material impact on the Company’s consolidated financial statements. In February 2018, the FASB issued ASU No. 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220), Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. This guidance provided entities with an option to reclassify tax effects that were stranded in accumulated other comprehensive income, pursuant to the recently enacted Tax Cuts and Jobs Act of 2017 (the “Tax Act”), to retained earnings. This guidance is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. This guidance may be early adopted in any interim or annual period for which financial statements have not yet been issued and applied either in the period of adoption or retrospectively to each period in which the effect of the change in the corporate tax rate in the Tax Act is recognized. The Company elected to early adopt the provisions of ASU No. 2018-02 on January 1, 2018 and reflected the reclassification related to the Tax Act in the period of adoption. The amount of the reclassification reflected the impact of the Tax Act that was signed into law on December 22, 2017 which reduced the corporate tax rate from 35% to 21%. The result of the early adoption of ASU No. 2018-02 was to reclassify a credit balance of $20.1 million from accumulated other comprehensive loss to retained earnings as of January 1, 2018. The Company utilizes a security-by-security approach to releasing income tax effects from accumulated other comprehensive loss. The adoption of ASU No. 2018-02 did not have a material impact on the Company’s consolidated financial statements. Recent Accounting Pronouncements The following ASUs have been issued by the FASB and are applicable to the Company in future reporting periods. In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842). This guidance provides that lessees will be required to recognize the following for all leases (with the exception of short-term leases): 1) a lease liability, which is the present value of a lessee's obligation to make lease payments, and 2) a right-of-use asset, which is an asset that represents the lessee's right to use, or control the use of, a specified asset for the lease term. Lessor accounting under the new guidance remains largely unchanged as it is substantially equivalent to existing guidance for sales-type leases, direct financing leases and operating leases. This guidance is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Entities are required to use a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period presented in the financial statements. As lessees, the Company has lease agreements for branch locations that are currently considered operating leases, and therefore, are not recognized on the Company’s consolidated balance sheets. The Company expects that the new guidance will require these leases to be recognized on the consolidated balance sheets as a right-of-use asset with a corresponding lease liability. The Company has formed a working group comprised of teams from different disciplines, including finance and bank properties. The Company continues to evaluate the impact this guidance will have on the Company’s consolidated financial statements. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments. This guidance eliminates the probable recognition threshold for credit losses on financial assets measured at amortized cost. For loans and held-to-maturity debt securities, this update requires a current expected credit loss (“CECL”) approach to determine the allowance for credit losses. CECL requires loss estimates for the remaining estimated life of the financial asset using historical experience, current conditions, and reasonable and supportable forecasts. In addition, this guidance modifies the other-than-temporary impairment model for available-for-sale debt securities to require an allowance for credit impairment instead of a direct write-down, which allows for a reversal of credit losses in future periods. The guidance requires entities to record a cumulative effect adjustment to the balance sheet as of the beginning of the first reporting period in which the guidance is effective. This update is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019, with earlier adoption permitted. The new guidance will require significant operational changes, particularly in data collection and analysis. The Company has formed a working group comprised of teams from different disciplines, including credit and finance, to evaluate the requirements of the new standard and the impact it will have on the Company’s current processes. Management’s evaluation includes a review of existing credit models to identify areas where existing credit models used to comply with other regulatory requirements may be leveraged and areas where new impairment models may be required. The Company continues to evaluate the impact this guidance, including the method of implementation, will have on its consolidated financial statements. In January 2017, the FASB issued ASU No. 2017-04, Intangibles – Goodwill and Other (Topic 350), Simplifying the Test for Goodwill Impairment. This guidance simplifies the subsequent measurement of goodwill by eliminating Step 2 from the current two-step goodwill impairment test. This guidance provides that a goodwill impairment test be conducted by comparing the fair value of a reporting unit with its carrying amount. Entities are to recognize an impairment charge for goodwill by the amount by which the carrying amount exceeds the reporting unit’s fair value. Entities will continue to have the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. This update is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. The adoption of ASU No. 2017-04 is not expected to have a material impact on the Company’s consolidated financial statements. In March 2017, the FASB issued ASU No. 2017-08, Receivables – Nonrefundable Fees and Other Costs (Subtopic 310-20), Premium Amortization on Purchased Callable Debt Securities. Under current GAAP, entities normally amortize the premium as an adjustment of yield over the contractual life of the instrument. This guidance shortens the amortization period for certain callable debt securities held at a premium to the earliest call date. This update is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. The adoption of ASU No. 2017-08 is not expected to have a material impact on the Company’s consolidated financial statements. In August 2017, the FASB issued ASU No. 2017-02, Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities. The objectives of the new guidance are to: (1) improve the transparency and understandability of information conveyed to financial statement users about an entity’s risk management activities by better aligning the entity’s financial reporting for hedging relationships with those risk management activities, and (2) reduce the complexity of and simplify the application of hedge accounting by preparers. Currently, the Company participates in limited activities in fair value and cash flow hedging relationships. However, hedging improvements in the new guidance will be considered in the development of future risk management strategies.