Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Mar. 31, 2021
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, Recorded Investment	$ 12,370		$ 12,370		$ 12,868
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, Unpaid Principal Balance	13,029		13,029		13,718
Impaired Financing Receivable, Related Allowance	128		128		158
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	12,618	$ 8,401	12,439	$ 10,336
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	76	40	156	99
One-to-four family
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,721		3,721		3,750
Impaired Financing Receivable, with Related Allowance, Recorded Investment	74		74		76
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	4,380		4,380		4,409
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	74		74		72
Impaired Financing Receivable, Related Allowance	30		30		32
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,735	3,795	3,728	3,840
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	75	442	74	317
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	3	10	6	35
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	1	0
Multifamily
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	882		882		369
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	882		882		369
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	625	374	883	373
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0	4	0	9
Commercial real estate
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	192		192		918
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	192		192		918
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	555	580	192	2,649
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Business
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,158		2,158		2,332
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,343		5,343		5,423
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	2,158		2,158		2,527
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	5,343		5,343		5,423
Impaired Financing Receivable, Related Allowance	98		98		$ 126
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,245	2,608	2,199	2,555
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	5,383	602	5,363	602
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0	26	0	55
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	$ 73	$ 0	$ 149	$ 0