Stock-Based Compensation Plans (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance under the Plan	600,000
Compensation cost	$ 119	$ 187	$ 172
Service period	3 years
Grant date fair value of shares granted, amount per share	$ 28.60	$ 28.96	$ 26.33
Stock options granted at percentage of fair value	100.00%
Options granted	0	0	0
Intrinsic value of options exercised	41	52	73
Intrinsic value of options exercisable	626
Options exercisable, weighted average remaining term	5 years 11 days
Cash received from exercise of stock options	0	0	280
Tax benefit from exercise of stock options and distribution of shares in deferred compensation arrangements	14	8	20
2008 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance under the Plan	600,000
Shares available for future grants under the plan	450,094
2008 Compensation Plan For Non-Employee Directors And Trustees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance under the Plan	150,000
Shares available for future grants under the plan	104,469
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted	7,120	5,846	6,680
Service period	3 years
Fair value of shares vested during the year	282
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service period	3 years
Current Outstanding Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	199
Exercise Price Range $22.07 to $22.93 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price range, options outstanding	72,000
Options exercise price range, lower range limit	$ 22.07
Options exercise price range, upper range limit	$ 22.93
Exercise price range $26.63 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price range, options outstanding	10,000
Options exercise price	$ 26.63
Restricted Stock [Member] \| Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 119	$ 187	$ 172

Share options (or share units) granted during the period at percentage of fair value.

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Exercise price for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards.

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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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Amount of deferred tax expense from write-off of the deferred tax asset related to deductible stock options at exercise.

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Aggregate proceeds received by the entity during the annual period from exercises of stock or unit options and conversion of similar instruments granted under equity-based payment arrangements.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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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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Net number of non-option equity instruments granted to participants.

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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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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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