Earnings Per Common Share (Basic And Diluted Earnings Per Common Share) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Distributed earnings allocated to common stock	$ 29,430	$ 28,123	$ 87,005	$ 83,695
Undistributed earnings allocated to common stock	29,051	26,238	90,195	77,868
Net earnings allocated to common stock	$ 58,481	$ 54,361	$ 177,200	$ 161,563
Weighted-average shares outstanding for basic earnings per common share	61,316,854	61,137,054	61,269,850	61,083,390
Dilutive effect of stock compensation	369,596	102,092	347,204	199,013
Weighted-average shares outstanding for diluted earnings per common share	61,686,450	61,239,146	61,617,054	61,282,403

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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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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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

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