Regulatory Matters - Association's Actual Capital Amounts and Ratios (Detail) - Association [Member] - USD ($) $ in Thousands	Jun. 30, 2018	Jun. 30, 2017
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Actual, Total capital (to risk-weighted assets), Amount	$ 78,988	$ 76,034
Actual, Tier I capital (to risk-weighted assets), Amount	73,053	70,405
Actual, Common Equity Tier I capital (to risk-weighted assets), Amount	73,053	70,405
Actual, Tier I capital (to adjusted total assets), Amount	73,053	70,405
Actual, Tangible capital (to adjusted total assets), Amount	$ 73,053	$ 70,405
Actual, Total capital (to risk-weighted assets), Ratio	16.09%	16.93%
Actual, Tier I capital (to risk-weighted assets), Ratio	14.88%	15.68%
Actual, Common Equity Tier I capital (to risk-weighted assets), Ratio	14.88%	15.68%
Actual, Tier I capital (to adjusted total assets), Ratio	11.51%	11.96%
Actual, Tangible capital (to adjusted total assets), Ratio	11.51%	11.96%
Minimum Capital Requirement, Total capital (to risk-weighted assets), Amount	$ 39,276	$ 35,928
Minimum Capital Requirement, Tier I capital (to risk-weighted assets), Amount	29,457	26,946
Minimum Capital Requirement, Common Equity Tier I capital (to risk-weighted assets), Amount	22,093	20,209
Minimum Capital Requirement, Tier I capital (to adjusted total assets), Amount	25,394	23,543
Minimum Capital Requirement, Tangible capital (to adjusted total assets), Amount	$ 9,523	$ 8,829
Minimum Capital Requirement, Total capital (to risk-weighted assets), Ratio	8.00%	8.00%
Minimum Capital Requirement, Tier I capital (to risk-weighted assets), Ratio	6.00%	6.00%
Minimum Capital Requirement, Common Equity Tier I capital (to risk-weighted assets), Ratio	4.50%	4.50%
Minimum Capital Requirement, Tier I capital (to adjusted total assets), Ratio	4.00%	4.00%
Minimum Capital Requirement, Tangible capital (to adjusted total assets), Ratio	1.50%	1.50%
Minimum to Be Well Capitalized Under Prompt Corrective Action Provisions, Total Capital (to risk-weighted assets), Amount	$ 49,095	$ 44,910
Minimum to Be Well Capitalized Under Prompt Corrective Action Provisions, Tier I capital (to risk-weighted assets), Amount	39,276	35,928
Minimum to Be Well Capitalized Under Prompt Corrective Action Provisions, Common Equity Tier I capital (to risk-weighted assets), Amount	31,912	29,191
Minimum to Be Well Capitalized Under Prompt Corrective Action Provisions, Tier I capital (to adjusted total assets), Amount	31,743	$ 29,429
Minimum to Be Well Capitalized Under Prompt Corrective Action Provisions, Tangible capital (to adjusted tangible assets), Amount	$ 0
Minimum to Be Well Capitalized Under Prompt Corrective Action Provisions, Total Capital (to risk-weighted assets), Ratio	10.00%	10.00%
Minimum to Be Well Capitalized Under Prompt Corrective Action Provisions, Tier I capital (to risk-weighted assets), Ratio	8.00%	8.00%
Minimum to Be Well Capitalized Under Prompt Corrective Action Provisions, Common Equity Tier I capital (to risk-weighted assets), Ratio	6.50%	6.50%
Minimum to Be Well Capitalized Under Prompt Corrective Action Provisions, Tier I capital (to adjusted total assets), Ratio	5.00%	5.00%