Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation and Cash-Based Incentive Compensation (Schedule of Compensation Expense under Share-Based Payment Arrangements and Related Tax Benefit) (Detail)

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Share-Based Compensation and Cash-Based Incentive Compensation (Schedule of Compensation Expense under Share-Based Payment Arrangements and Related Tax Benefit) (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation $ 3,319 $ 2,775 $ 9,137 $ 6,437
Tax benefit computed at the statutory rate 1,162 971 3,198 2,253
Restricted Stock [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation 110 593 324 1,784
Restricted Stock Units (RSUs) [Member]
       
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Share-based compensation $ 3,209 $ 2,182 $ 8,813 $ 4,653