Securities Held to Maturity - Schedule Of Held To Maturity Securities Pledged (Detail) - Securities Held to Maturity [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Jun. 30, 2018
Schedule Of Held To Maturity Securities [Line Items]
Held to maturity securities pledged	$ 266,083	$ 283,746
FHLB of New York [Member]
Schedule Of Held To Maturity Securities [Line Items]
Held to maturity securities pledged	128,888	142,646
Secure Public Funds On Deposit [Member]
Schedule Of Held To Maturity Securities [Line Items]
Held to maturity securities pledged	7,270	7,604
Federal Reserve ("FRB") [Member]
Schedule Of Held To Maturity Securities [Line Items]
Held to maturity securities pledged	105,194	107,520
Depositor Sweep Accounts [Member]
Schedule Of Held To Maturity Securities [Line Items]
Held to maturity securities pledged	$ 24,731	$ 25,976