Loans Receivable and Allowance for Loan and Lease Losses Nonaccrual Loans (Details) - Nonperforming - USD ($) $ in Thousands	Sep. 30, 2019	Mar. 31, 2019
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	$ 7,728	$ 10,294
One-to-four family
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	3,753	4,488
Multifamily
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	2,433	3,214
Commercial real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	0	476
Business
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	1,542	2,051
Consumer
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	$ 0	$ 65