Benefit Plans - Schedule of Net Funded Status (Detail) - USD ($)	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2019	Jun. 30, 2018
Atlas Bank Retirement Income Plan ("ABRIP") [Member]
Change in benefit obligation:
Projected benefit obligation - beginning	$ 2,716,000	$ 2,896,000
Interest cost	108,000	109,000	$ 108,000
Actuarial loss (gain)	(58,000)	(85,000)
Benefit payments	(213,000)	(204,000)
Projected benefit obligation - ending	2,553,000	2,716,000	2,896,000
Change in plan assets:
Fair value of assets - beginning	3,440,000	3,692,000
Actual return on assets	(4,000)	(48,000)
Benefit payments	(213,000)	(204,000)
Fair value of assets - ending	3,223,000	3,440,000	3,692,000
Reconciliation of funded status:
Projected benefit obligation	(2,716,000)	(2,716,000)	(2,896,000)	$ (2,553,000)	$ (2,716,000)
Fair value of assets - ending	3,223,000	3,440,000	3,692,000
Funded status included in other assets / liabilities				670,000	724,000
Accumulated benefit obligation				$ (2,553,000)	$ (2,716,000)
Discount rate				3.75%	4.25%
Benefit Equalization Plan ("BEP") [Member]
Change in benefit obligation:
Projected benefit obligation - beginning	3,053,000	3,223,000
Interest cost	125,000	124,000	134,000
Actuarial loss (gain)	162,000	(61,000)
Benefit payments	(235,000)	(233,000)	(231,000)
Projected benefit obligation - ending	3,105,000	3,053,000	3,223,000
Change in plan assets:
Benefit payments	(235,000)	(233,000)
Contributions	235,000	233,000	231,000
Reconciliation of funded status:
Projected benefit obligation	(3,053,000)	(3,053,000)	(3,223,000)	$ (3,105,000)	$ (3,053,000)
Funded status included in other assets / liabilities				(3,105,000)	(3,053,000)
Accumulated benefit obligation				$ (3,105,000)	$ (3,053,000)
Discount rate				3.75%	4.25%
Postretirement Welfare Plan [Member]
Change in benefit obligation:
Projected benefit obligation - beginning	617,000	586,000
Service cost	54,000	48,000	31,000
Interest cost	26,000	23,000	21,000
Actuarial loss (gain)	19,000	(33,000)
Benefit payments	(6,000)	(7,000)	(7,000)
Projected benefit obligation - ending	710,000	617,000	586,000
Change in plan assets:
Benefit payments	(6,000)	(7,000)
Contributions	6,000	7,000	7,000
Reconciliation of funded status:
Projected benefit obligation	(617,000)	(617,000)	(586,000)	$ (710,000)	$ (617,000)
Funded status included in other assets / liabilities				$ (710,000)	$ (617,000)
Discount rate				3.75%	4.25%
Salary increase rate				3.25%	3.25%
Directors' Consultation and Retirement Plan ("DCRP") [Member]
Change in benefit obligation:
Projected benefit obligation - beginning	2,843,000	2,978,000
Interest cost	119,000	118,000	116,000
Actuarial loss (gain)	73,000	(193,000)
Benefit payments	(60,000)	(60,000)	(60,000)
Projected benefit obligation - ending	2,975,000	2,843,000	2,978,000
Change in plan assets:
Benefit payments	(60,000)	(60,000)
Contributions	60,000	60,000	60,000
Reconciliation of funded status:
Projected benefit obligation	$ (2,843,000)	$ (2,843,000)	$ (2,978,000)	$ (2,975,000)	$ (2,843,000)
Funded status included in other assets / liabilities				(2,975,000)	(2,843,000)
Accumulated benefit obligation				$ (2,975,000)	$ (2,843,000)
Discount rate				3.75%	4.25%