| Document and Entity Information | Jan. 22, 2020 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K/A |
| Document Period End Date | Jan. 22, 2020 |
| Entity File Number | 001-14585 |
| Entity Registrant Name | FIRST HAWAIIAN, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 99-0156159 |
| Entity Address, Address Line One | 999 Bishop St. |
| Entity Address, Adress Line Two | 29th Floor |
| Entity Address, State or Province | HI |
| Entity Address, City or Town | Honolulu |
| Entity Address, Postal Zip Code | 96813 |
| City Area Code | 808 |
| Local Phone Number | 525-7000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | FHB |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000036377 |
| Amendment Flag | true |
| Amendment Description | On January 28, 2020, First Hawaiian, Inc. (the “Company”) filed with the Securities and Exchange Commission a Current Report on Form 8-K (the “Form 8-K”) to, among other things, report that the Company issued a press release (the “Original Press Release”) reporting its earnings for the quarter ended December 31, 2019. The Company furnished as Exhibit 99.1 of the Form 8-K a copy of the Original Press Release. The sole purpose of this Amendment No. 1 to the Form 8-K is to furnish as Exhibit 99.1 hereto a copy of the correcting and replacing press release of the Company, dated January 29, 2020, which notes the correct record date for the Company’s next quarterly dividend of February 24, 2020, rather than February 28, 2020, as had been previously stated in the Original Press Release. |
