Accumulated Other Comprehensive Income (AOCI) - Components of AOCI (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, included in stockholders's equity	$ 3,707	$ 5,711
Tax effect	(825)	(1,264)
Net of tax amount	283,423	258,347	$ 238,392	$ 200,694
Net unrealized gain on securities available-for-sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, included in stockholders's equity	3,734	5,744
Net unrealized gain on securities available-for-sale securities for which a portion of an other-than-temporary impairment has been recognized in income
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, included in stockholders's equity	(1)	(1)
Unrealized gain from defined benefit pension plan
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, included in stockholders's equity	(26)	(32)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net of tax amount	$ 2,882	$ 4,447	$ 1,247	$ (2,345)