Loans and Allowance for Loan Losses - Summary of Impaired Loans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Financing Receivable, Impaired [Line Items]
Specific Allowance	$ 3	$ 1,533
Recorded Balance	9,342	11,595
Unpaid Principal Balance	9,342	11,595
Specific Allowance	3	1,533
Average Investment in Impaired Loans	10,278	7,782
Interest Income Recognized	142	292
Interest on Cash Basis	144	329
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Balance, Loans without a specific allowance	47	19
Unpaid Principal Balance, Loans without a specific allowance	47	19
Specific Allowance, Loans without a specific allowance	0	0
Average Investment in Impaired Loans, Loans without a specific allowance	86	23
Interest Income Recognized, Loans without a specific allowance	4
Interest on Cash Basis, Loans without a specific allowance	5
Recorded Balance, Loans with a specific allowance	3	6
Unpaid Principal Balance, Loans with a specific allowance	3	6
Specific Allowance	3	6
Average Investment in Impaired Loans, Loans with a specific allowance	5	7
Recorded Balance	50	25
Unpaid Principal Balance	50	25
Specific Allowance	3	6
Average Investment in Impaired Loans	91	30
Interest Income Recognized	4
Interest on Cash Basis	5
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Balance, Loans without a specific allowance	30	89
Unpaid Principal Balance, Loans without a specific allowance	30	89
Specific Allowance, Loans without a specific allowance	0	0
Average Investment in Impaired Loans, Loans without a specific allowance	57	87
Recorded Balance	30	89
Unpaid Principal Balance	30	89
Average Investment in Impaired Loans	57	87
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Recorded Balance, Loans without a specific allowance	3
Unpaid Principal Balance, Loans without a specific allowance	3
Specific Allowance, Loans without a specific allowance	0	0
Average Investment in Impaired Loans, Loans without a specific allowance	4
Interest Income Recognized, Loans without a specific allowance	1
Interest on Cash Basis, Loans without a specific allowance	1
Recorded Balance	3
Unpaid Principal Balance	3
Average Investment in Impaired Loans	4
Interest Income Recognized	1
Interest on Cash Basis	1
One- to four-family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Balance, Loans without a specific allowance	7,904	2,220
Unpaid Principal Balance, Loans without a specific allowance	7,904	2,220
Specific Allowance, Loans without a specific allowance	0	0
Average Investment in Impaired Loans, Loans without a specific allowance	8,739	2,276
Interest Income Recognized, Loans without a specific allowance	50	38
Interest on Cash Basis, Loans without a specific allowance	51	51
Recorded Balance, Loans with a specific allowance		7,814
Unpaid Principal Balance, Loans with a specific allowance		7,814
Specific Allowance		1,527
Average Investment in Impaired Loans, Loans with a specific allowance		3,907
Interest Income Recognized, Loans with a specific allowance		185
Interest on Cash Basis, Loans with a specific allowance		185
Recorded Balance	7,904	10,034
Unpaid Principal Balance	7,904	10,034
Specific Allowance		1,527
Average Investment in Impaired Loans	8,739	6,183
Interest Income Recognized	50	223
Interest on Cash Basis	51	236
Multi-family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Balance, Loans without a specific allowance	1,329	1,390
Unpaid Principal Balance, Loans without a specific allowance	1,329	1,390
Specific Allowance, Loans without a specific allowance	0	0
Average Investment in Impaired Loans, Loans without a specific allowance	1,359	1,421
Interest Income Recognized, Loans without a specific allowance	85	67
Interest on Cash Basis, Loans without a specific allowance	85	90
Recorded Balance	1,329	1,390
Unpaid Principal Balance	1,329	1,390
Average Investment in Impaired Loans	1,359	1,421
Interest Income Recognized	85	67
Interest on Cash Basis	85	90
Home equity lines of credit [Member]
Financing Receivable, Impaired [Line Items]
Recorded Balance, Loans without a specific allowance	26	57
Unpaid Principal Balance, Loans without a specific allowance	26	57
Specific Allowance, Loans without a specific allowance	0	0
Average Investment in Impaired Loans, Loans without a specific allowance	28	61
Interest Income Recognized, Loans without a specific allowance	2	2
Interest on Cash Basis, Loans without a specific allowance	2	3
Recorded Balance	26	57
Unpaid Principal Balance	26	57
Average Investment in Impaired Loans	28	61
Interest Income Recognized	2	2
Interest on Cash Basis	2	3
Construction [Member]
Financing Receivable, Impaired [Line Items]
Specific Allowance, Loans without a specific allowance	$ 0	$ 0