Share-Based Compensation (Summary Of Stock Option Activity) (Details) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Options outstanding, January 1	509,422	384,507	253,836
Options outstanding, March 31,	211,675	509,422	384,507
Weighted Average Exercise Price, January 1, Outstanding	$ 42.03	$ 33.24	$ 27.72
Weighted Average Exercise Price, March 31, Outstanding	$ 46.60	$ 42.03	$ 33.24
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price	$ 44.08
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	3 years 8 months 15 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 2,102,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 436,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 6.36	$ 9.91	$ 6.26
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	35,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	3 years 1 month 21 days
1997 Plan [Member]
Options exercised	19,266	15,000	48,717
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 33.26	$ 23.79	$ 31.56
2005 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	340,000	340,000	395,000
Options exercised	618,481	183,417	215,612
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price	$ 43.63	$ 32.69	$ 31.78
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 47.52	$ 46.11	$ 36.18
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period		(16,668)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price		$ 41.52
Grant Date 2-4-2008 [Member]
Options outstanding, March 31,	5,000
Weighted Average Exercise Price, March 31, Outstanding	$ 29.24
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	0 years 1 month 6 days 2 hours
Grant Date 2-22-2011 [Member]
Options outstanding, March 31,	15,000
Weighted Average Exercise Price, March 31, Outstanding	$ 45.58
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	3 years 1 month 24 days 8 hours
Grant Date 2-25-2011 [Member]
Options outstanding, March 31,	56,672
Weighted Average Exercise Price, March 31, Outstanding	$ 46.22
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	3 years 1 month 24 days 8 hours
Grant Date 2-21-2012 [Member]
Options outstanding, March 31,	135,003
Weighted Average Exercise Price, March 31, Outstanding	$ 47.52
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	4 years 1 month 24 days 8 hours

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

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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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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The number of shares reserved for issuance pertaining to the outstanding stock options as of the balance sheet date for all option plans in the customized range of exercise prices.

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