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Organization and Summary of Significant Accounting Policies - Transition to an Independent Public Company (Details) - First Hawaiian, Inc. (FHI) - USD ($) |  | 12 Months Ended
--- | --- | ---
Feb. 01, 2019 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
BNP Paribas (BNPP) |  |  |  |
Reorganization Transactions |  |  |  |
Outstanding common stock owned after sales of shares (as a percent) | 0.00% |  |  |
Completion of public offering |  |  |  |
Reorganization Transactions |  |  |  |
Proceeds from the sales of shares |  | $ 0 | $ 0 | $ 0

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