Share-Based Compensation (Details 2) (USD $)	3 Months Ended
Mar. 31, 2013
Summary of stock option activity
Options outstanding, Beginning Balance, Shares	363,896
Options outstanding, Beginning Balance, Weighted Average Exercise Price	$ 22.03
Options outstanding, Beginning Balance, Options Exercisable	276,009
Exercised, Shares	(47,343)
Exercised, Weighted Average Exercise Price	$ 19.48
Forfeited or Expired, Shares	(27,086)
Forfeited or Expired, Weighted Average Exercise Price	$ 28.28
Options outstanding, Ending Balance, Shares	289,467
Options outstanding, Ending Balance, Weighted Average Exercise Price	$ 21.87
Options outstanding, Ending Balance, Options Exercisable	287,467

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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-Name Accounting Standards Codification

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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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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.

+ References

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

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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Number of share options (or share units) exercised during the current period.

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