Fair Value Disclosures (Narrative Disclosures) (Details) - USD ($)	9 Months Ended	12 Months Ended
Sep. 30, 2017	Dec. 31, 2016
Fair Value Inputs, Assets, Quantitative Information
Fair value, assets, level 1 to level 2 transfers	$ 0	$ 0
Fair value, assets, level 2 to Level 1 transfers	0	0
Fair value, assets, transfers into level 3	0	0
Fair value, assets, transfers out of level 3	0	0
Fair value, liabilities, level 1 to level 2 transfers	0	0
Fair value, liabilities, level 2 to level 1 transfers	0	0
Fair value, liabilities, transfers into level 3	0	0
Fair value, liabilities, transfers out of level 3	0	0
Commercial paper, at carrying value	13,400,000	20,300,000
Certificates of deposit, at carrying value	$ 3,300,000	1,600,000
Minimum
Fair Value Inputs, Assets, Quantitative Information
Quantification of unobservable inputs for level 3 values for impaired loans	13.00%
Maximum
Fair Value Inputs, Assets, Quantitative Information
Quantification of unobservable inputs for level 3 values for impaired loans	90.00%
Weighted Average
Fair Value Inputs, Assets, Quantitative Information
Quantification of unobservable inputs for level 3 values for impaired loans	20.00%
Impaired loans
Fair Value Inputs, Assets, Quantitative Information
Assets measured on a non-recurring basis, fair value	$ 16,298,000	13,365,000
Fair Value Measurements - Level 3 Inputs \| Impaired loans
Fair Value Inputs, Assets, Quantitative Information
Assets measured on a non-recurring basis, fair value	8,661,000	1,097,000
Fair Value Measurements - Level 3 Inputs \| Foreclosed properties
Fair Value Inputs, Assets, Quantitative Information
Assets measured on a non-recurring basis, fair value	$ 0	$ 0

Fair Value, Assets, Level 1 to Level 2 Transfers, Amount1

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Fair Value, Assets, Level 2 to Level 1 Transfers, Amount1

+ References

No definition available.

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- Definition

Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount1

+ References

No definition available.

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Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount1

+ References

No definition available.

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- Definition

Quantification of unobservable inputs for Level 3 values for impaired loans

+ References

No definition available.

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- Definition

This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value on a nonrecurring basis by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements.

+ References

No definition available.

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- Definition

A savings certificate entitling the Entity (that is, bearer) to receive interest at an established maturity date, based upon a fixed interest rate. A certificate of deposit may be issued in any denomination. Certificates of deposit are generally issued by commercial banks and, therefore, insured by the FDIC (up to the prescribed limit). Certificates of deposit generally restrict holders from withdrawing funds on demand without the incurrence of penalties. Generally, only certificates of deposit with original maturities of three months or less qualify as cash equivalents. Original maturity means original maturity to the entity holding the investment. As a related example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

Unsecured short-term debt instrument issued by corporations which are highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3052-108585

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Amount of transfers of financial instrument classified as a liability into level 3 of the fair value hierarchy.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- Definition

Amount of transfers of financial instrument classified as a liability out of level 3 of the fair value hierarchy.

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- Definition

Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

+ References

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- Definition

Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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