Loans Receivable and Related Allowance for Loan Losses - Impaired Loans by Class (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Impaired Loans with Specific Allowance
Unpaid Principal Balance	$ 77	$ 707	$ 1,313
Recorded Investment	77	707	1,280
Related Allowance	10	97	120
Average Recorded Investment	679	947	677
Interest Income Recognized in Period	1	1	29
Cash Basis Interest Recognized in Period	1	1	6
Impaired Loans with No Specific Allowance
Unpaid Principal Balance	2,215	1,422	727
Recorded Investment	2,004	990	553
Average Recorded Investment	1,279	906	1,080
Interest Income Recognized in Period	8	3	5
Cash Basis Interest Recognized in Period	8	3	5
Residential first mortgages
Impaired Loans with Specific Allowance
Unpaid Principal Balance	77	78	168
Recorded Investment	77	78	135
Related Allowance	10	19	19
Average Recorded Investment	106	124	119
Interest Income Recognized in Period	1	1	6
Cash Basis Interest Recognized in Period	1	1	6
Impaired Loans with No Specific Allowance
Unpaid Principal Balance	409	91	0
Recorded Investment	372	58	0
Average Recorded Investment	186	29	23
Interest Income Recognized in Period	7	2	0
Cash Basis Interest Recognized in Period	7	2	0
Home equity loans and lines of credit
Impaired Loans with Specific Allowance
Unpaid Principal Balance	0	0	0
Recorded Investment	0	0	0
Related Allowance	0	0	0
Average Recorded Investment	0	0	0
Interest Income Recognized in Period	0	0	0
Cash Basis Interest Recognized in Period	0	0	0
Impaired Loans with No Specific Allowance
Unpaid Principal Balance	0	0	0
Recorded Investment	0	0	0
Average Recorded Investment	0	0	0
Interest Income Recognized in Period	0	0	0
Cash Basis Interest Recognized in Period	0	0	0
Commercial real estate
Impaired Loans with Specific Allowance
Unpaid Principal Balance	0	0	557
Recorded Investment	0	0	557
Related Allowance	0	0	95
Average Recorded Investment	279	47	130
Interest Income Recognized in Period	0	0	23
Cash Basis Interest Recognized in Period	0	0	0
Impaired Loans with No Specific Allowance
Unpaid Principal Balance	1,165	1,256	631
Recorded Investment	991	857	457
Average Recorded Investment	724	801	735
Interest Income Recognized in Period	1	1	3
Cash Basis Interest Recognized in Period	1	1	3
Commercial business
Impaired Loans with Specific Allowance
Unpaid Principal Balance	0	629	588
Recorded Investment	0	629	588
Related Allowance	0	78	6
Average Recorded Investment	294	776	428
Interest Income Recognized in Period	0	0	0
Cash Basis Interest Recognized in Period	0	0	0
Impaired Loans with No Specific Allowance
Unpaid Principal Balance	641	75	96
Recorded Investment	641	75	96
Average Recorded Investment	369	76	322
Interest Income Recognized in Period	0	0	2
Cash Basis Interest Recognized in Period	0	0	2
Consumer
Impaired Loans with Specific Allowance
Unpaid Principal Balance	0	0	0
Recorded Investment	0	0	0
Related Allowance	0	0	0
Average Recorded Investment	0	0	0
Interest Income Recognized in Period	0	0	0
Cash Basis Interest Recognized in Period	0	0	0
Impaired Loans with No Specific Allowance
Unpaid Principal Balance	0	0	0
Recorded Investment	0	0	0
Average Recorded Investment	0	0	0
Interest Income Recognized in Period	0	0	0
Cash Basis Interest Recognized in Period	$ 0	$ 0	$ 0

Impaired Financing Receivable, with No Related Allowance [Abstract]

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Impaired Financing Receivable, with Related Allowance [Abstract]

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- Definition

Amount of allowance for credit losses related to recorded investment.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5212-111524

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Amount of average investment of impaired financing receivables for which there is no related allowance for credit losses.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5258-111524

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Amount of interest income, recognized on accrual basis, on financing receivables that are recognized as impaired, for which there is no related allowance for credit losses.

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Amount of interest income, recognized on cash basis, on financing receivables, for which there is no related allowance for credit losses and are recognized as impaired.

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Amount of investment in impaired financing receivables for which there is no related allowance for credit losses.

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-Publisher FASB
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Unpaid principal balance of impaired financing receivables for which there is a related allowance for credit losses.

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