Nonaccrual Loans (Details) - Nonperforming - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019	Mar. 31, 2019
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	$ 7,193		$ 10,294
One-to-four family
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	4,053		4,488
Multifamily
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	378		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	2,754		2,051
Consumer
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	$ 8		$ 65