Loans Receivable and Allowance for Loan Losses - Interest Income on Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Financing Receivable, Impaired [Line Items]
Average recorded Investment	$ 22,292	$ 19,873	$ 21,313	$ 20,646
Interest Income Recognized	290	197	590	194
Real estate loans \| One-to-four family
Financing Receivable, Impaired [Line Items]
Average recorded Investment	8,611	10,715	9,149	11,025
Interest Income Recognized	108	103	214	103
Real estate loans \| Multifamily and commercial
Financing Receivable, Impaired [Line Items]
Average recorded Investment	2,666	2,718	2,681	3,043
Interest Income Recognized	37	30	74	28
Real estate loans \| Construction
Financing Receivable, Impaired [Line Items]
Average recorded Investment	1,700	0	1,133	0
Interest Income Recognized	0	0	25	0
Commercial business loans
Financing Receivable, Impaired [Line Items]
Average recorded Investment	6,616	3,180	5,430	3,541
Interest Income Recognized	98	25	178	25
Consumer loans \| Home equity loans and advances
Financing Receivable, Impaired [Line Items]
Average recorded Investment	2,699	3,260	2,920	3,037
Interest Income Recognized	$ 47	$ 39	$ 99	$ 38

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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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