Loans - Narrative, Troubled Debt Restructurings (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020 USD ($) contract	Mar. 31, 2019 USD ($) contract	Jun. 30, 2018 contract	Dec. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of relationships (contract) | contract	0	2
Pre-Modification Outstanding Recorded Investment		$ 2,836
Post-Modification Outstanding Recorded Investment		$ 2,836
Troubled debt restructurings	$ 17,100			$ 18,500
Number of TDR loans restructured that subsequently defaulted (contract) | contract	1	0	0
Loans restructured that subsequently defaulted	$ 27
One-to-Four Family
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of relationships (contract) | contract		1
Pre-Modification Outstanding Recorded Investment		$ 2
Post-Modification Outstanding Recorded Investment		$ 2
Commercial Mortgage Backed Securities
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of relationships (contract) | contract		1
Pre-Modification Outstanding Recorded Investment		$ 2,834
Post-Modification Outstanding Recorded Investment		$ 2,834