Loans Receivable, Net - Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Impaired Financing Receivable, Recorded Investment
Impaired Financing Receivable, Recorded Investment	$ 14,693	$ 19,565
Impaired Financing Receivable, Unpaid Principal Balance
Impaired Financing Receivable, Unpaid Principal Balance	16,141	21,457
Impaired Financing Receivable, Related Allowance	361	590
Impaired Financing Receivable, Average Recorded Investment
Impaired Financing Receivable, Average Recorded Investment	15,961	15,855
Impaired Financing Receivable, Interest Income, Cash Basis Method
Impaired Financing Receivable, Interest Income, Cash Basis Method	210	280
One-to-four family
Impaired Financing Receivable, Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	3,416	2,909
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,091	1,727
Impaired Financing Receivable, Unpaid Principal Balance
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	4,210	4,101
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,215	1,727
Impaired Financing Receivable, Related Allowance	306	95
Impaired Financing Receivable, Average Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,078	2,835
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	2,128	1,725
Impaired Financing Receivable, Interest Income, Cash Basis Method
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	14	17
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	5	25
Multifamily
Impaired Financing Receivable, Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,596	1,769
Impaired Financing Receivable, with Related Allowance, Recorded Investment	6	0
Impaired Financing Receivable, Unpaid Principal Balance
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	2,081	2,122
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	6	0
Impaired Financing Receivable, Related Allowance	6	0
Impaired Financing Receivable, Average Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,747	1,463
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1	0
Impaired Financing Receivable, Interest Income, Cash Basis Method
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	6	17
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	0
Commercial real estate
Impaired Financing Receivable, Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	993	5,405
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,502	889
Impaired Financing Receivable, Unpaid Principal Balance
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	993	5,572
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,502	889
Impaired Financing Receivable, Related Allowance	6	21
Impaired Financing Receivable, Average Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	1,774	2,935
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1,427	895
Impaired Financing Receivable, Interest Income, Cash Basis Method
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	17	0
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	0	43
Business
Impaired Financing Receivable, Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,923	4,223
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2,164	2,643
Impaired Financing Receivable, Unpaid Principal Balance
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	1,968	4,403
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2,164	2,643
Impaired Financing Receivable, Related Allowance	41	474
Impaired Financing Receivable, Average Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment	3,619	3,662
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	2,187	2,340
Impaired Financing Receivable, Interest Income, Cash Basis Method
Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method	142	93
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	26	85
Consumer
Impaired Financing Receivable, Recorded Investment
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	0	0
Impaired Financing Receivable, with Related Allowance, Recorded Investment	2	0
Impaired Financing Receivable, Unpaid Principal Balance
Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance	0	0
Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance	2	0
Impaired Financing Receivable, Related Allowance	2	0
Impaired Financing Receivable, Average Recorded Investment
Impaired Financing Receivable, with Related Allowance, Average Recorded Investment	1	0
Impaired Financing Receivable, Interest Income, Cash Basis Method
Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method	$ 0	$ 0