Pro Forma Results Under Acquisitions (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010
Business Acquisition, Pro Forma Information [Line Items]
Revenue	$ 1,527,044	$ 1,652,153
Income from continuing operations	357,060	309,549
Net income	$ 382,976	$ 314,972
Income from continuing operations per common share, basic	$ 1.93	$ 1.72
Income from continuing operations per common share, diluted	$ 1.56	$ 1.42
Net income per common share, basic	$ 2.07	$ 1.75
Net income per common share, diluted	$ 1.67	$ 1.44

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The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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