Organization and Basis of Presentation - Transition to an Independent Public Company (Details) - shares		12 Months Ended	29 Months Ended
	Feb. 01, 2019	Dec. 31, 2018	Dec. 31, 2018
BNP Paribas (BNPP)
Reorganization Transactions
Number of shares sold			109,830,000
BNP Paribas (BNPP) | First Hawaiian, Inc. (FHI)
Reorganization Transactions
Number of shares sold	24,859,750
Outstanding common stock owned (as a percent)	0.00%
BancWest Corporation (BWC)
Reorganization Transactions
Number of shares repurchased		4,769,870