EMPLOYEE BENEFIT PLANS - Net Periodic Pension Cost (Details) - Pension plan - USD ($)	12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Net periodic pension cost included in the Bank’s consolidated statements of income
Service cost	$ 2,252,000	$ 1,574,000
Interest cost	1,968,000	1,918,000
Expected return on plan assets	(3,703,000)	(3,518,000)
Amortization of net actuarial loss	1,080,000	760,000
Net periodic cost	1,597,000	734,000
Amounts recognized in accumulated other comprehensive (gain) loss, before tax effect
Amounts recognized in accumulated other comprehensive loss, before tax, net actuarial losses	23,541,000	$ 15,311,000
Estimated net actuarial loss that will be amortized from accumulated other comprehensive loss into net periodic benefit cost during next fiscal year	$ 1,732,000