Loans Receivable and Allowance for Loan Losses - Interest Income on Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Financing Receivable, Impaired [Line Items]
Average recorded Investment	$ 19,868	$ 26,306	$ 20,457	$ 29,513
Interest Income Recognized	200	226	198	242
Real estate loans \| One-to-four family
Financing Receivable, Impaired [Line Items]
Average recorded Investment	10,606	14,154	10,873	15,476
Interest Income Recognized	107	113	105	135
Real estate loans \| Multifamily and commercial
Financing Receivable, Impaired [Line Items]
Average recorded Investment	2,717	5,084	2,961	6,504
Interest Income Recognized	30	39	29	33
Real estate loans \| Construction
Financing Receivable, Impaired [Line Items]
Average recorded Investment			0	168
Interest Income Recognized			0	0
Commercial business loans
Financing Receivable, Impaired [Line Items]
Average recorded Investment	3,098	3,508	3,390	3,843
Interest Income Recognized	24	31	25	29
Consumer loans
Financing Receivable, Impaired [Line Items]
Average recorded Investment
Interest Income Recognized
Consumer loans \| Home equity loans and advances
Financing Receivable, Impaired [Line Items]
Average recorded Investment	3,447	3,560	3,233	3,522
Interest Income Recognized	$ 39	$ 43	$ 39	$ 45

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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5258-111524

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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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