Securities - Schedule of Available for Sale Securities Pledged (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Jun. 30, 2020
Schedule Of Available For Sale Securities [Line Items]
Carrying value of securities pledged	$ 598,206	$ 549,544
FHLB of New York [Member]
Schedule Of Available For Sale Securities [Line Items]
Carrying value of securities pledged	155,620	155,288
Secure Public Funds On Deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Carrying value of securities pledged	104,434	19,944
Federal Reserve ("FRB") [Member]
Schedule Of Available For Sale Securities [Line Items]
Carrying value of securities pledged	$ 338,152	366,482
Depositor Sweep Accounts [Member]
Schedule Of Available For Sale Securities [Line Items]
Carrying value of securities pledged		$ 7,830