Impairment of Securities - Additional Information (Detail) - Security	Dec. 31, 2018	Jun. 30, 2018
Schedule Of Investments [Line Items]
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions	137	132
Held-to-maturity, securities in unrecognized loss positions, qualitative disclosure, number of positions	348	371
Collateralized Loan Obligations [Member]
Schedule Of Investments [Line Items]
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions	17	19
Debt Securities [Member] | Trust Preferred Securities [Member]
Schedule Of Investments [Line Items]
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions	2	2
Debt Securities [Member] | Asset-backed Securities [Member]
Schedule Of Investments [Line Items]
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions	8	3
Debt Securities [Member] | Corporate Bonds [Member]
Schedule Of Investments [Line Items]
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions	13	6
Debt Securities [Member] | U.S. Agency Securities [Member]
Schedule Of Investments [Line Items]
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions	8	9
Debt Securities [Member] | Obligations of State and Political Subdivisions [Member]
Schedule Of Investments [Line Items]
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions	64	65
Held-to-maturity, securities in unrecognized loss positions, qualitative disclosure, number of positions	176	190
Debt Securities [Member] | Subordinated Debt [Member]
Schedule Of Investments [Line Items]
Held-to-maturity, securities in unrecognized loss positions, qualitative disclosure, number of positions	8	7
Collateralized Mortgage Obligations Excluding Pass Through Securities [Member]
Schedule Of Investments [Line Items]
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions	7	7
Held-to-maturity, securities in unrecognized loss positions, qualitative disclosure, number of positions	7	8
Residential Pass-Through Securities [Member]
Schedule Of Investments [Line Items]
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions	16	19
Held-to-maturity, securities in unrecognized loss positions, qualitative disclosure, number of positions	127	131
Commercial Pass-Through Securities [Member]
Schedule Of Investments [Line Items]
Available-for-sale, securities in unrealized loss positions, qualitative disclosure, number of positions	2	2
Held-to-maturity, securities in unrecognized loss positions, qualitative disclosure, number of positions	30	35