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Number of Directors

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Refers to the number of directors elected to receive stock in lieu of cash out of total.

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Refers to the amount of regular quarterly retainer that a director could receive in cash.

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Refers to the amount of regular quarterly retainer if restricted stock vested.

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Amount of increase to additional paid-in capital (APIC) resulting from recognition of equity-based compensation for restricted stock units.

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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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The total fair value of shares issued during the period under a deferred compensation arrangement.

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Number of shares issued pursuant to the terms of a deferred compensation arrangement.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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

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Unrecognized cost of unvested options awarded to employees as compensation.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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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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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Gross number of share options (or share units) granted during the period.

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Number of share instruments newly issued under a share-based compensation plan.

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The noncash expense that accounts for the value of stock or unit options distributed to employees as compensation.

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Stock-Based Compensation - Narrative (Details)	12 Months Ended
Stock-Based Compensation - Narrative (Details)	Dec. 31, 2017 USD ($) director shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Apr. 22, 2008 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of common stock authorizes for issuance (in shares) \| shares				500,000
Total proceeds of the in-the-money options exercised	$ 113,000	$ 142,000	$ 789,000
Total intrinsic value of options exercised	287,000	11,000	220,000
Unrecognized compensation expense	0	0	0
Compensation expense related to stock options	$ 0	$ 0	$ 0
Stock options granted during period (in shares) \| shares	0	0	0
Regular monthly board retainer, cash	$ 5,800
Regular monthly board retainer, market value of restricted stock	6,250
Monthly meeting fees a director could receive in cash	725
Monthly meeting fees a director could receive if restricted stock vested	$ 900
Number of directors elected to receive stock in lieu of cash \| director	11
Number of outside directors \| director	13
Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued as payment for deferred compensation (in shares) \| shares			4,158
Market value of shares issued as payment of deferred compensation			$ 95,000
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum vesting period of granted restricted stock	36 months
Unrecognized compensation cost	$ 538,000	$ 568,000	340,000
Share based compensation expense	$ 532,000	$ 444,000	$ 322,000
Number of shares issued (in shares) \| shares	13,093	13,166	11,228
Recognized share based compensation expense	$ 484,000	$ 380,000	$ 275,000
Restricted Stock \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period for recognition of unrecognized compensation cost	12 months
Restricted Stock \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period for recognition of unrecognized compensation cost	36 months