Reconciliation of Weighted Average Shares Used in Calculating Basic and Diluted Earnings Per Share (Detail) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share Disclosure [Line Items]
Basic	68,242	73,297	70,284	73,016
Effect of exercise of stock options	987	1,117	976	1,187
Effect of contingent common stock issuance			48	48
Effect of assumed vesting of restricted stock	1,288	1,332	1,213	1,269
Diluted	70,517	75,746	72,521	75,520

Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of contingently issuable shares. Contingently issuable shares are those shares that are issuable for little or no cash contingent on certain conditions being met.

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

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-Name Emerging Issues Task Force (EITF)

-Number 07-4

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

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

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