Fair Value of Financial Instruments - Schedule of Assets Measured At Fair Value on a Non-recurring Basis (Detail) - USD ($)	Dec. 31, 2020	Jun. 30, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	$ 1,696,109,000	$ 1,385,938,000
Fair Value, Measurements, Nonrecurring [Member] | Collateral Dependent Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	5,275,000
Fair Value, Measurements, Nonrecurring [Member] | Collateral Dependent Loans [Member] | Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	1,900,000
Fair Value, Measurements, Nonrecurring [Member] | Collateral Dependent Loans [Member] | Non-Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	3,375,000
Fair Value, Measurements, Nonrecurring [Member] | Other Real Estate Owned [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	178,000	178,000
Fair Value, Measurements, Nonrecurring [Member] | Other Real Estate Owned [Member] | Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	178,000	178,000
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value		4,750,000
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value		2,339,000
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Non-Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value		2,282,000
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Commercial Business [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value		129,000
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	1,696,109,000	1,385,938,000
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Collateral Dependent Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	5,275,000
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Collateral Dependent Loans [Member] | Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	1,900,000
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Collateral Dependent Loans [Member] | Non-Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	3,375,000
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Other Real Estate Owned [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	178,000	178,000
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Other Real Estate Owned [Member] | Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	$ 178,000	178,000
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value		4,750,000
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value		2,339,000
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Non-Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value		2,282,000
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Commercial Business [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value		$ 129,000