Stock-Based Compensation (Summary Of Stock Option Transactions) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Shares	26,993
Exercised, Shares	(473,351)
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding at beginning of period, Shares	3,376,960
Forfeited, Shares	(7,486)
Expired, Shares	(26,976)
Exercised, Shares	(473,351)
Outstanding at end of period, Shares	2,869,147
Exercisable at end of period, Shares	2,724,869
Outstanding at beginning of period, Weighted Average Exercise Price	20.03
Forfeited, Weighted Average Exercise Price	17.69
Expired, Weighted Average Exercise Price	23.56
Exercised, Weighted Average Exercise Price	16.63
Outstanding at end of period, Weighted Average Exercise Price	20.56
Exercisable at end of period, Weighted Average Exercise Price	20.74
Outstanding at end of period, Weighted Average Remaining Life (years)	4 years 7 months 6 days
Exercisable at end of period, Weighted Average Remaining Life (years)	4 years 6 months
Outstanding at end of period, Aggregate Intrinsic Value	14,579,511
Exercisable at end of period, Aggregate Intrinsic Value	13,451,257

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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.

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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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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of options outstanding.

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

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

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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

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