Leases - Additional Information (Detail)	3 Months Ended	9 Months Ended
	Mar. 31, 2020 USD ($) BranchOffice AdministrativeOffice	Mar. 31, 2020 USD ($) BranchOffice AdministrativeOffice
Lessee Lease Description [Line Items]
Number of branch offices in real estate lease | BranchOffice	11	11
Number of administrative office in real estate lease | AdministrativeOffice	2	2
Lease maturity start year		2020
Lease maturity end year		2041
Lease option to extend		some of which include lessee options to extend the lease term.
Operating lease, weighted average remaining lease terms	10 years	10 years
Lessee, operating lease, description		The operating lease asset and lease liability are determined at the commencement date of the lease based on the present value of the lease payments.
Operating lease, weighted average discount rate, percent	2.41%	2.41%
Short-term lease cost	$ 0	$ 0
Sale and leaseback transactions with related parties	0	0
Operating lease, liability	11,649,000	11,649,000
Occupancy and Equipment Expense [Member]
Lessee Lease Description [Line Items]
Operating lease, cost	501,000	1,500,000
Premises And Equipment [Member]
Lessee Lease Description [Line Items]
Operating lease ,right-of-use asset	11,400,000	11,400,000
Other Liabilities [Member]
Lessee Lease Description [Line Items]
Operating lease, liability	$ 11,600,000	$ 11,600,000
Maximum [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease, original term	12 months	12 months