Stock Incentive Plan Summary of Unvested Stock and Stock Units (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost	$ 954,000
Other than Options, Nonvested, Number	0	32,338	30,169	26,897
Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$ 0.00	$ 22.64	$ 20.87	$ 22.95
RSA/RSU, Grants in Period, Gross	18,391	13,912	18,002
Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 30.65	$ 26.09	$ 20.14
Other than Options, Vested in Period	(50,729)	(11,743)	(14,730)
Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$ 25.54	$ 22.18	$ 23.77
Other than Options, Forfeited in Period	0	0	0
Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	$ 0.00	$ 0.00	$ 0.00
Other than Options, Vested in Period, Total Fair Value	$ 260,483	$ 260,483	$ 350,075
Nonvested Awards, Total Compensation Cost Not yet Recognized, Share-based Awards Other than Options	$ 0	$ 344,000	$ 386,000
Discounted Cash Flow [Member] \| Weighted Average [Member] \| Significant Unobservable Inputs (Level 3) \| Trust preferred securities
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Loss severity

Loss severity used when pricing the investments.

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Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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No definition available.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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-Subparagraph (c)(2)(iii)(3)
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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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-Publisher FASB
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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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- Definition

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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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.

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No definition available.

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- Definition

Amount of capitalized and expensed compensation cost from equity-based compensation arrangements.

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