Stock-Based Compensation Plans (Summary of Activity Related to Share Based Awards) (Details) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($) $ / shares shares
Restricted Stock Units (RSUs) [Member]
Number of Shares
Nonvested, beginning \| shares	0
Granted \| shares	18,762
Vested \| shares	0
Forfeited \| shares	(1,285)
Nonvested, ending \| shares	17,477
Weighted Average Grant Date Fair Value
Nonvested, beginning \| $ / shares	$ 0.00
Granted \| $ / shares	43.05
Vested \| $ / shares	0.00
Forfeited \| $ / shares	43.11
Nonvested, ending \| $ / shares	$ 43.04
Weighted-Average Remaining Contractual Term (Years)
Nonvested, weighted average remaining contractual term	4 years 7 months 6 days
Aggregate Intrinsic Value
Nonvested, aggregate intrinsic value \| $	$ 736
Unrecognized Compensation
Nonvested, unrecognized compensation \| $	$ 620
Restricted Stock [Member]
Number of Shares
Nonvested, beginning \| shares	47,518
Granted \| shares	16,185
Vested \| shares	(22,553)
Forfeited \| shares	(4,825)
Nonvested, ending \| shares	36,325
Weighted Average Grant Date Fair Value
Nonvested, beginning \| $ / shares	$ 28.16
Granted \| $ / shares	42.39
Vested \| $ / shares	31.14
Forfeited \| $ / shares	28.93
Nonvested, ending \| $ / shares	$ 32.56
Weighted-Average Remaining Contractual Term (Years)
Nonvested, weighted average remaining contractual term	2 years 2 months 12 days
Aggregate Intrinsic Value
Nonvested, aggregate intrinsic value \| $	$ 1,530
Unrecognized Compensation
Nonvested, unrecognized compensation \| $	$ 787
Management Stock Purchase Plan [Member]
Number of Shares
Nonvested, beginning \| shares	26,699
Granted \| shares	8,088
Vested \| shares	(11,777)
Forfeited \| shares	(2,791)
Nonvested, ending \| shares	20,219
Weighted Average Grant Date Fair Value
Nonvested, beginning \| $ / shares	$ 7.85
Granted \| $ / shares	13.73
Vested \| $ / shares	7.73
Forfeited \| $ / shares	11.49
Nonvested, ending \| $ / shares	$ 9.77
Weighted-Average Remaining Contractual Term (Years)
Nonvested, weighted average remaining contractual term	1 year
Aggregate Intrinsic Value
Nonvested, aggregate intrinsic value \| $	$ 431
Unrecognized Compensation
Nonvested, unrecognized compensation \| $	$ 54
Performance Shares [Member]
Number of Shares
Nonvested, beginning \| shares	52,737
Granted \| shares	16,830
Vested \| shares	(32,323)
Forfeited \| shares	(5,621)
Nonvested, ending \| shares	31,623
Weighted Average Grant Date Fair Value
Nonvested, beginning \| $ / shares	$ 27.01
Granted \| $ / shares	41.39
Vested \| $ / shares	26.09
Forfeited \| $ / shares	26.97
Nonvested, ending \| $ / shares	$ 35.60
Weighted-Average Remaining Contractual Term (Years)
Nonvested, weighted average remaining contractual term	1 year 8 months 12 days
Aggregate Intrinsic Value
Nonvested, aggregate intrinsic value \| $	$ 1,332
Unrecognized Compensation
Nonvested, unrecognized compensation \| $	$ 291
DCRP Awards [Member]
Number of Shares
Nonvested, beginning \| shares	14,244
Granted \| shares	2,772
Vested \| shares	(2,776)
Forfeited \| shares	(4,192)
Nonvested, ending \| shares	10,048
Weighted Average Grant Date Fair Value
Nonvested, beginning \| $ / shares	$ 23.65
Granted \| $ / shares	42.66
Vested \| $ / shares	32.50
Forfeited \| $ / shares	25.88
Nonvested, ending \| $ / shares	$ 25.52
Weighted-Average Remaining Contractual Term (Years)
Nonvested, weighted average remaining contractual term	9 years 2 months 12 days
Aggregate Intrinsic Value
Nonvested, aggregate intrinsic value \| $	$ 423
Unrecognized Compensation
Nonvested, unrecognized compensation \| $	$ 229

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

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

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

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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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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).

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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.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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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Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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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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Intrinsic value of equity-based compensation awards not vested. Excludes stock and unit options.

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