Loans Receivable and Allowance for Loan Losses - Troubled Debt Restructuring (Details) $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($) loan	Dec. 31, 2018 USD ($) loan	Sep. 30, 2017 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
No. of Loans \| loan	1	7	7
Pre-modification Recorded Investment	$ 4,095	$ 1,454	$ 4,778
Post-modification Recorded Investment	$ 4,095	$ 1,454	$ 4,778
Real estate loans \| One-to-four family
Financing Receivable, Troubled Debt Restructuring [Line Items]
No. of Loans \| loan	0	5	3
Pre-modification Recorded Investment	$ 0	$ 801	$ 548
Post-modification Recorded Investment	$ 0	$ 801	$ 548
Real estate loans \| Multifamily and commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
No. of Loans \| loan	0	1	1
Pre-modification Recorded Investment	$ 0	$ 65	$ 3,964
Post-modification Recorded Investment	$ 0	$ 65	$ 3,964
Commercial business loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
No. of Loans \| loan	1	0	1
Pre-modification Recorded Investment	$ 4,095	$ 0	$ 18
Post-modification Recorded Investment	$ 4,095	$ 0	$ 18
Consumer loans \| Home equity loans and advances
Financing Receivable, Troubled Debt Restructuring [Line Items]
No. of Loans \| loan	0	1	2
Pre-modification Recorded Investment	$ 0	$ 588	$ 248
Post-modification Recorded Investment	$ 0	$ 588	$ 248

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No definition available.

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Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=118936363&loc=SL6953676-111524

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Amount, after troubled debt restructuring, of modified financing receivable.

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- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

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