Fair Value of Financial Instruments - Schedule of Quantitative Information about Level 3 Fair Value Measurements (Detail) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Dec. 31, 2018	Jun. 30, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		$ 688,711	$ 756,966
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		4,299	4,469
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		3,446	3,562
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Non-Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		791	794
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Commercial Business [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		62	113
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Valuation of Underlying Collateral [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		4,299	4,469
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Valuation of Underlying Collateral [Member] | Adjustments to Reflect Current Conditions or Selling Costs [Member] | Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		$ 3,446	$ 3,562
Valuation Techniques	[1]	Market valuation of underlying collateral
Unobservable Input	[2]	Adjustments to reflect current conditions/selling costs
Weighted Average		9.35%	12.34%
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Valuation of Underlying Collateral [Member] | Adjustments to Reflect Current Conditions or Selling Costs [Member] | Non-Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		$ 791	$ 794
Valuation Techniques	[1]	Market valuation of underlying collateral
Unobservable Input	[2]	Adjustments to reflect current conditions/selling costs
Weighted Average		11.74%	14.07%
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Valuation of Underlying Collateral [Member] | Adjustments to Reflect Current Conditions or Selling Costs [Member] | Commercial Business [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		$ 62	$ 113
Valuation Techniques	[1]	Market valuation of underlying collateral
Unobservable Input	[2]	Adjustments to reflect current conditions/selling costs
Weighted Average		6.46%	14.54%
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Valuation of Underlying Collateral [Member] | Adjustments to Reflect Current Conditions or Selling Costs [Member] | Minimum [Member] | Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Range		6.00%	6.00%
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Valuation of Underlying Collateral [Member] | Adjustments to Reflect Current Conditions or Selling Costs [Member] | Minimum [Member] | Non-Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Range		11.00%	14.00%
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Valuation of Underlying Collateral [Member] | Adjustments to Reflect Current Conditions or Selling Costs [Member] | Minimum [Member] | Commercial Business [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Range		0.00%	10.00%
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Valuation of Underlying Collateral [Member] | Adjustments to Reflect Current Conditions or Selling Costs [Member] | Maximum [Member] | Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Range		21.00%	26.00%
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Valuation of Underlying Collateral [Member] | Adjustments to Reflect Current Conditions or Selling Costs [Member] | Maximum [Member] | Non-Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Range		12.00%	15.00%
Fair Value, Measurements, Nonrecurring [Member] | Impaired Loans [Member] | Market Valuation of Underlying Collateral [Member] | Adjustments to Reflect Current Conditions or Selling Costs [Member] | Maximum [Member] | Commercial Business [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Range		10.00%	24.00%
Fair Value, Measurements, Nonrecurring [Member] | Other Real Estate Owned [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		$ 288
Fair Value, Measurements, Nonrecurring [Member] | Other Real Estate Owned [Member] | Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		288
Fair Value, Measurements, Nonrecurring [Member] | Other Real Estate Owned [Member] | Market Valuation of Underlying Collateral [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		288
Fair Value, Measurements, Nonrecurring [Member] | Other Real Estate Owned [Member] | Market Valuation of Underlying Collateral [Member] | Adjustments to Reflect Current Conditions or Selling Costs [Member] | Residential Mortgage [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assets, Fair Value		$ 288
Valuation Techniques	[3]	Market valuation of underlying collateral
Unobservable Input	[2]	Adjustments to reflect current conditions/selling costs
Range		5.00%
Weighted Average		5.00%

[1] The fair value of impaired loans is generally determined based on an independent appraisal of the fair value of a loan’s underlying collateral.

[2] The fair value basis of impaired loans and other real estate owned is adjusted to reflect management estimates of selling costs including, but not necessarily limited to, real estate brokerage commissions and title transfer fees

[3] The fair value basis of other real estate owned is generally determined based upon the lower of an independent appraisal of the property’s fair value or the applicable listing price or contracted sales price.