Share-Based Payments (Summary of Stock Option Transactions under our Share-Based Payment Plans) (Details) (USD $)	12 Months Ended
Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009
Share-Based Payments [Abstract]
Outstanding at December 31, 2010, number of shares	1,402,256
Granted 2011, number of shares	0
Exercised 2011, number of shares	135,196
Forfeited or expired 2011, number of shares	27,373
Outstanding at December 31, 2010, number of shares	1,239,687	1,402,256
Exercisable at December 31, 2011, number of shares	1,130,901
Outstanding at December 31, 2010, weighted average exercise price	$ 18.08
Granted 2011, weighted average exercise price	$ 0.00
Exercised 2011, weighted average exercise price	$ 11.26
Forfeited or expired 2011, weighted average exercise price	$ 20.58
Outstanding at December 31, 2011, weighted average exercise price	$ 18.78	$ 18.08
Exercisable at December 31, 2011, weighted average exercise price	$ 19.08
Outstanding at December 31, 2011, weighted average remaining contractual life in years	5.20
Exercisable at December 31, 2011, weighted average remaining contractual life in years	4.95
Outstanding at Decemeber 31, 2011, aggregate intrinsic value	$ 2,381,000
Exercisable at December 31, 2011, aggregate intrinsic value	2,135,000
Total intrinsic value of options exercised	$ 800,000	$ 800,000	$ 400,000

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The total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices of vested portions of options outstanding and currently exercisable under the option plan as of the balance sheet date.

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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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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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The weighted average period between the balance sheet date and expiration for all vested portions of options outstanding and currently exercisable (or convertible) under the plan, which may be expressed in a decimal value for number of years.

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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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The weighted average price at which option holders acquired shares when converting their stock options into shares under the plan during the reporting period.

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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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The combined weighted average exercise price associated with stock options during the period that have either lapsed or been forfeited.

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

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The weighted average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on stock options awarded under the plan during the reporting period.

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The total dollar difference between fair values of the underlying shares reserved for issuance and exercise prices pertaining to options outstanding under the plan as of the balance sheet date.

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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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The weighted average price as of the beginning of the year at which grantees can acquire the shares reserved for issuance under the stock option plan.

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The weighted average period between the balance sheet date and expiration for all awards outstanding under the plan, which may be expressed in a decimal value for number of years.

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

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