Fair Value of Financial Instruments - Schedule of Assets Measured At Fair Value on a Non-recurring Basis (Detail) - USD ($)	Dec. 31, 2018	Jun. 30, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	$ 688,711,000	$ 756,966,000
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	4,299,000	4,469,000
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	3,446,000	3,562,000
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	791,000	794,000
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	62,000	113,000
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	288,000
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	288,000
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	687,711,000	755,966,000
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets, Fair Value	1,000,000	1,000,000
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	4,299,000	4,469,000
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	3,446,000	3,562,000
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	791,000	794,000
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	62,000	113,000
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	288,000	$ 0
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	$ 288,000