Basic and Diluted Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Reconciliation of basic and diluted earnings per share
Net earnings	$ 55,075	$ 35,526
Basic shares:
Average shares outstanding	51,960	51,546
Basic earning per share	$ 1.06	$ 0.69
Diluted shares:
Average shares outstanding	51,960	51,546
Additional shares on the potential dilution from stock options, nonvested restricted stock and performance units	1,266	1,371
Number of diluted shares outstanding	53,226	52,917
Diluted earnings per share	$ 1.03	$ 0.67

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 consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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- 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.

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- 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.

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-Glossary Weighted-Average Number of Common Shares Outstanding

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