Commitments and Contingent Liabilities - Contingencies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Sep. 30, 2018
Contingencies
Settlement agreement	$ 4.1
Overdraft fee litigation
Contingencies
Settlement agreement		$ 4.1
First Hawaiian Bank (FHB)
Contingencies
Period for one-time continuous negative balance overdraft fee	7 days