Post-Retirement Benefits - Additional Information (Detail) - USD ($)	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain from reduction to salaries and employee benefits expense			$ 919,000
Effective date of freezing of the defined benefit pension plan		May 01, 2017
Defined benefit plan, contributions by employer		$ 0
Percentage of investment in plan assets		100.00%	100.00%
Estimated long-term inflation rate		2.50%
Expected return on plan assets		7.50%
ESOP shares		1,453,209	1,453,209
Stock price		$ 10.00
ESOP payable term		15 years
ESOP prime rate percentage		4.50%
ESOP borrowing		$ 13,600,000
Number of shares committed to be released per year through 2032		96,881
ESOP Compensation		$ 2,248,000	$ 454,000
Equity Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of investment in plan assets		67.00%	65.00%
Equity Mutual Funds [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets		6.00%
Equity Mutual Funds [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets		8.00%
Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of investment in plan assets		1.00%	1.00%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of investment in plan assets		32.00%	34.00%
Fixed Income Securities [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets		3.00%
Fixed Income Securities [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets		5.00%
Scenario Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, contributions by employer	$ 0
Employee Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pre-tax amounts recognized in accumulated other comprehensive loss		$ 6,500,000	$ 7,600,000
Defined benefit plan, contributions by employer			$ 3,000,000
Assumed discount rates used		4.14%	3.87%
Temporary increase in percentage of bond fund portion		50.00%
Expected return on plan assets		7.50%	7.50%
Benefits Paid		$ 868,000	$ 828,000
Employee Pension Plan [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset rebalancing threshold		10.00%
Employee Pension Plan [Member] | Equity Mutual Funds [Member] | Long-Term Objective [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of investment in plan assets		65.00%
Employee Pension Plan [Member] | Debt Securities [Member] | Long-Term Objective [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of investment in plan assets		34.00%
Employee Pension Plan [Member] | Cash Equivalents [Member] | Long-Term Objective [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of investment in plan assets		1.00%
Employee Pension Plan [Member] | Scenario Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss	580,000
Prior service (credit) cost	0
Defined Contribution Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, description		The Company maintained a defined contribution plan for eligible employees hired after October 1, 2012. All full-time employees who have attained age twenty-one and have a minimum of one year of service received a contribution to their 401(k) account equal to 5% of their salary.
Defined contribution plan for eligible employee who hired after		Oct. 01, 2012
Defined contribution plan, minimum age for eligibility to receive contribution		21 years
Defined contribution plan, minimum period of service to receive contribution		1 year
Rate of contribution receive by employee on salary		5.00%
Plan expense		$ 0	120,000	$ 162,000
401 (k) Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan, minimum age for eligibility to receive contribution		21 years
Defined contribution plan, minimum period of service to receive contribution		1 year
Rate of contribution receive by employee on salary		10.00%
Employee contribution minimum percentage rate		2.00%
Employer matching contribution, percent of match		75.00%
Employer matching contribution, percent of employee gross pay		6.00%
Defined contribution savings plan expense		$ 414,000	418,000	410,000
Defined benefit plan effective date of suspension		Jul. 01, 2018
Acquired Pension Plan [Member] | CMS Bancorp [Member]
Defined Benefit Plan Disclosure [Line Items]
Termination of pension plan and chargeable to earning				629,000
Supplemental Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss		$ 335,000	379,000
Accrued benefit cost		3,400,000	3,000,000
Projected benefit obligation and accumulated benefit obligation		3,400,000	3,000,000
Pension expense		655,000	615,000	539,000
Benefits Paid		$ 272,000	$ 272,000	$ 272,000
Supplemental Retirement Plan [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumed discount rates used		3.16%
Rates of compensation increases used		3.16%
Supplemental Retirement Plan [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Assumed discount rates used		4.14%
Rates of compensation increases used		4.14%
Supplemental Retirement Plan [Member] | Scenario Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated amortization of net loss	$ 37,000