Loans Receivable and Allowance for Loan Losses - Interest Income on Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Financing Receivable, Impaired [Line Items]
Average recorded Investment	$ 19,873	$ 25,955	$ 20,646	$ 29,279
Interest Income Recognized	197	298	194	258
Real estate loans \| One-to-four family
Financing Receivable, Impaired [Line Items]
Average recorded Investment	10,715	15,202	11,025	16,175
Interest Income Recognized	103	169	103	156
Real estate loans \| Multifamily and commercial
Financing Receivable, Impaired [Line Items]
Average recorded Investment	2,718	3,295	3,043	5,311
Interest Income Recognized	30	41	28	27
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	3,180	3,237	3,541	3,662
Interest Income Recognized	25	28	25	27
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	3,260	4,221	3,037	3,963
Interest Income Recognized	$ 39	$ 60	$ 38	$ 48

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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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