Stock-Based Compensation (Schedule of Stock Option Awards) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2011
Stock-Based Compensation
Outstanding, Beginning Balance, Shares	863
Outstanding, Beginning Balance, Outstanding Weighted-Average Exercise Price	$ 32.69
Granted, Shares	179
Granted, Outstanding Weighted-Average Exercise Price	$ 76.34
Exercised, Shares	(160)
Exercised, Outstanding Weighted-Average Exercise Price	$ 30.75
Forfeited, Shares	(25)
Forfeited, Weighted-Average Grant-Date Fair Value	$ 47.01
Expired or canceled, Shares
Expired or canceled, Outstanding Weighted-Average Exercise Price
Outstanding, Ending Balance, Shares	857
Outstanding, Ending Balance, Outstanding Weighted-Average Exercise Price	$ 41.65
Outstanding, Ending Balance, Aggregate Intrinsic Value	$ 36,346
Outstanding, Ending Balance, Weighted-Average Remaining Contractual Life (in years)	4.6
Exercisable, Ending Balance, Shares	456
Exercisable, Ending Balance, Outstanding Weighted-Average Exercise Price	$ 32.03
Exercisable, Ending Balance, Aggregate Intrinsic Value	$ 23,749
Exercisable, Ending Balance, Weighted-Average Remaining Contractual Life (in years)	3.5

Share Based Compensation Arrangements By Share Based Payment Award Options Outstanding Weighted Average Remaining Contractual Term.

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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 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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The decrease in the number of shares that could be issued attributable to the lapse of rights to exercise previously issued stock options under the terms of the option agreements under the plan during the reporting period.

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The weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that lapsed during the reporting period.

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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.

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The weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated during the reporting period due to noncompliance with plan terms during the reporting period.

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

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