Loans Receivable, Net - Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Impaired Financing Receivable, Recorded Investment
Impaired Financing Receivable, Recorded Investment	$ 11,447	$ 12,868
Impaired Financing Receivable, Unpaid Principal Balance
Impaired Financing Receivable, Unpaid Principal Balance	12,203	13,718
Impaired Financing Receivable, Related Allowance	69	158
Impaired Financing Receivable, Average Recorded Investment
Impaired Financing Receivable, Average Recorded Investment	12,158	12,618
Impaired Financing Receivable, Interest Income, Cash Basis Method
Impaired Financing Receivable, Interest Income, Cash Basis Method	323	192
One-to-four family
Impaired Financing Receivable, Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	4,892	3,750
Impaired Financing Receivable, with Related Allowance, Recorded Investment	0	76
Impaired Financing Receivable, Unpaid Principal Balance
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	5,576	4,409
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	0	72
Impaired Financing Receivable, Related Allowance	0	32
Impaired Financing Receivable, Average Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	4,321	4,119
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	38	503
Impaired Financing Receivable, Interest Income, Cash Basis Method
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	50	64
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0
Multifamily
Impaired Financing Receivable, Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	515	369
Impaired Financing Receivable, Unpaid Principal Balance
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	515	369
Impaired Financing Receivable, Average Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	442	1,791
Impaired Financing Receivable, Interest Income, Cash Basis Method
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	16	16
Commercial real estate
Impaired Financing Receivable, Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	918
Impaired Financing Receivable, Unpaid Principal Balance
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	918
Impaired Financing Receivable, Average Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	459	697
Impaired Financing Receivable, Interest Income, Cash Basis Method
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	7	10
Business
Impaired Financing Receivable, Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	837	2,332
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,203	5,423
Impaired Financing Receivable, Unpaid Principal Balance
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	909	2,527
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	5,203	5,423
Impaired Financing Receivable, Related Allowance	69	126
Impaired Financing Receivable, Average Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,585	2,153
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	5,313	3,355
Impaired Financing Receivable, Interest Income, Cash Basis Method
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	33	102
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	$ 217	$ 0