Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2020
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, Recorded Investment	$ 13,302		$ 13,302		$ 8,450
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, Unpaid Principal Balance	14,117		14,117		9,314
Impaired Financing Receivable, Related Allowance	174		174		166
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	10,876	$ 9,238	10,827	$ 10,647
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	40	44	149	129
One-to-four family
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,762		3,762		3,819
Impaired Financing Receivable, with Related Allowance, Recorded Investment	77		77		807
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	4,420		4,420		4,566
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	73		73		803
Impaired Financing Receivable, Related Allowance	33		33		156
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,790	4,143	3,767	4,390
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	442	813	77	870
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	10	14	50	43
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Multifamily
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	370		370		375
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	372		372		376
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	373	1,406	371	1,796
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	4	14	13	45
Commercial real estate
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,160		1,160		0
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,160		1,160		0
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	580	0	1,160	238
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	2,471		2,471		2,797
Impaired Financing Receivable, with Related Allowance, Recorded Investment	5,462		5,462		652
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	2,630		2,630		2,917
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	5,462		5,462		652
Impaired Financing Receivable, Related Allowance	141		141		$ 10
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,634	2,096	2,445	2,374
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	3,057	780	3,007	979
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	26	16	86	41
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	$ 0	$ 0	$ 0	$ 0