Stock Based Compensation Schedule of Other Stock Option Plan Information (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Granted, in shares	75,786	78,425	77,047
Fair Value of Options Granted, Weighted Average Grant Date, in dollars per share	$ 6.01	$ 6.12	$ 6.12
Dividend Yield	3.93%	4.00%	3.80%
Expected Volatility	37.43%	36.50%	35.40%
Risk Free Interest Rate	1.22%	2.54%	3.14%
Expected Life, in years	6 years 5 months 16 days	6 years 4 months 25 days	7 years 9 months 15 days
Stock-Based Compensation Expense	$ 424	$ 354	$ 299
Compensation Costs for Non-vested Awards Not Yet Recognized	737	705	579
Weighted Average Expected Vesting Period, In Years	1 year 8 months 15 days	1 year 9 months 18 days	1 year 9 months 18 days
Proceeds From Stock Options Exercised	2,105	1,413	798
Tax Benefit for Disposition of Stock Options	68	51	105
Intrinsic Value of Stock Options Exercised	$ 2,434	$ 1,740	$ 1,404

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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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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Aggregate unrecognized cost of option awards made to employees under a stock option plan or plans, that have yet to vest.

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Disclosure of the aggregate tax benefit realized from the exercise of stock options and the conversion of similar instruments during the annual period.

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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The total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.

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

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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