Derivative Financial Instruments (Narrative Disclosures) (Details) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2017	Dec. 31, 2016
Derivatives
Fair value of interest rate swaps	$ 1,380	$ 352
Interest rate swap contracts not designated as hedging instruments - liabilities, gross	1,380	$ 352
Derivative asset, fair value, amount offset against collateral	0
Derivative Instruments in Hedges, at Fair Value, Net	$ 0
Interest rate derivatives, line item on income statement for gain (loss)	other non-interest income
To commercial borrowers, corporation receives fixed rates and pays floating rates
Derivatives
Fair value of interest rate swaps	$ 1,400
To commercial borrowers, corporation receives fixed rates and pays floating rates \| Minimum
Derivatives
Derivative, maturity date	Sep. 30, 2018
To commercial borrowers, corporation receives fixed rates and pays floating rates \| Maximum
Derivatives
Derivative, maturity date	Mar. 15, 2034
To dealer countparties, corporation pays fixed rates and receives floating rates
Derivatives
Interest rate swap contracts not designated as hedging instruments - liabilities, gross	$ 1,400
Interest rate derivative instruments not designated as hedging instruments at fair value, net	$ 1,400
To dealer countparties, corporation pays fixed rates and receives floating rates \| Minimum
Derivatives
Derivative, maturity date	Sep. 30, 2018
To dealer countparties, corporation pays fixed rates and receives floating rates \| Maximum
Derivatives
Derivative, maturity date	Mar. 15, 2034
Not Designated as Hedging Instrument \| To commercial borrowers, corporation receives fixed rates and pays floating rates
Derivatives
Notional value of interest rate swaps with various commercial borrowers	$ 52,300
Not Designated as Hedging Instrument \| To dealer countparties, corporation pays fixed rates and receives floating rates
Derivatives
Notional value of interest rate swaps with various commercial borrowers	$ 52,300

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=d3e41678-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226016-175313

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Aggregate net fair value of all derivative instruments designated as hedging instruments. Includes instruments designated as cash flow hedges, fair value hedges, and hedges of net investments in foreign operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13495-108611

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Date the derivative contract matures, in CCYY-MM-DD format.

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Description of where the net gain (loss) on interest rate derivatives not designated as hedging instruments are reported in the statement of income or other statement of financial performance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(n)(7))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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Fair value as of the balance sheet date of all derivative assets not designated as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(2)
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Fair value as of the balance sheet date of all derivatives not designated as hedging instruments.

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-Name Accounting Standards Codification
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- Definition

Fair value as of the balance sheet date of all derivative liabilities not designated as hedging instruments.

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