Stock Option Accounting (Details Textual) (USD $)	3 Months Ended
Mar. 31, 2013	Dec. 31, 2012
Stock Option Accounting (Textual) [Abstract]
Number of outstanding options	20,400	23,350
Weighted average exercise price	$ 31.82	$ 31.17
Options granted	0
Common Class A [Member]
Stock Option Accounting (Textual) [Abstract]
Number of outstanding options	20,400
Exercise prices of shares outstanding, minimum	$ 31.60
Exercise prices of shares outstanding, maximum	$ 31.83
Weighted average exercise price	$ 31.82
Weighted average remaining contractual life	1 year 6 months
Intrinsic value of options exercisable	$ 42,636
Intrinsic value of options exercised	$ 11,568

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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.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

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- Definition

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.

+ References

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

+ References

No definition available.

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The number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

+ References

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- Definition

Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

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.

+ References

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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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