Earnings Per Share (Details) (USD $) In Thousands, except Share data	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Earnings Per Share (Details) [Abstract]
Number of anti-dilutive stock options	1,297,560	2,366,676	577,742	2,044,471
Earnings Per Share (Table Details) [Abstract]
Net earnings	$ 31,224	$ 40,497	$ 115,342	$ 139,788
Basic weighted average shares	60,030,000	65,094,000	61,944,000	65,579,000
Effect of dilutive stock options	474,000	652,000	704,000	766,000
Diluted weighted average shares	60,504,000	65,746,000	62,648,000	66,345,000
Basic earnings per common share	$ 0.52	$ 0.62	$ 1.86	$ 2.13
Diluted earnings per common share	$ 0.52	$ 0.62	$ 1.84	$ 2.11

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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-Glossary Contingent Stock Agreement

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+ Details

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

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+ Details

- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

+ References+ Details

- Definition

Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

+ References

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