Loans Receivable and Allowance for Loan Losses - Interest Income on Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Financing Receivable, Impaired [Line Items]
Average recorded Investment	$ 22,350	$ 19,868	$ 21,375	$ 20,457
Interest Income Recognized	261	200	841	198
Real estate loans \| One-to-four family
Financing Receivable, Impaired [Line Items]
Average recorded Investment	8,773	10,606	9,144	10,873
Interest Income Recognized	101	107	340	105
Real estate loans \| Multifamily and commercial
Financing Receivable, Impaired [Line Items]
Average recorded Investment	2,637	2,717	2,667	2,961
Interest Income Recognized	37	30	111	29
Real estate loans \| Construction
Financing Receivable, Impaired [Line Items]
Average recorded Investment	850	0	850	0
Interest Income Recognized	0	0	0	0
Commercial business loans
Financing Receivable, Impaired [Line Items]
Average recorded Investment	7,461	3,098	5,848	3,390
Interest Income Recognized	88	24	268	25
Consumer loans \| Home equity loans and advances
Financing Receivable, Impaired [Line Items]
Average recorded Investment	2,629	3,447	2,866	3,233
Interest Income Recognized	$ 35	$ 39	$ 122	$ 39

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- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5212-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5258-111524

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- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

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