Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2019
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, Recorded Investment	$ 8,925		$ 8,925		$ 12,369
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, Unpaid Principal Balance	9,998		9,998		13,567
Impaired Financing Receivable, Related Allowance	168		168		189
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, Average Recorded Investment	9,238	$ 12,182	10,647	$ 12,622
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, Interest Income, Cash Basis Method	44	44	129	115
One-to-four family
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	4,291		4,291		4,488
Impaired Financing Receivable, with Related Allowance, Recorded Investment	811		811		929
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	5,296		5,296		5,643
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	806		806		929
Impaired Financing Receivable, Related Allowance	158		158		171
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	4,143	4,608	4,390	4,973
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	813	938	870	1,000
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	14	25	43	60
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	378		378		3,214
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	378		378		3,214
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,406	2,518	1,796	1,836
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	0	0	0	371
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	14	11	45	29
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0	0	0
Commercial real estate
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0		0		476
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0		0		476
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	0	486	238	1,011
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	0	8	0	16
Business
Impaired Financing Receivable, Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	2,774		2,774		1,974
Impaired Financing Receivable, with Related Allowance, Recorded Investment	671		671		1,288
Impaired Financing Receivable, Unpaid Principal Balance [Abstract]
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	2,847		2,847		2,017
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	671		671		1,288
Impaired Financing Receivable, Related Allowance	10		10		$ 18
Impaired Financing Receivable, Average Recorded Investment [Abstract]
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	2,096	1,204	2,374	1,192
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	780	2,428	979	2,239
Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract]
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	16	0	41	6
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	$ 0	$ 0	$ 0	$ 4