v2.4.0.6
Employee Savings Plans - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Expenses related ESOP $ 7,380,000 $ 7,011,000 $ 8,123,000
Shares vested under ESOP 4,508,000    
Matching contributions to 401(k) retirement savings plan 9,318,000 8,456,000 7,073,000
Maximum percentage of employee contributions that company matches 5.00%    
Matching percentage of employer to employee contributions 100.00%    
Supplemental Executive Retirement Plan
     
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Assets of the rabbi trust 15,872,000 3,639,000  
SERP liability $ 15,872,000 $ 3,639,000  
Eligible U.S. Employees
     
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Maximum percentage of employee contributions that company matches 50.00%    
Employee Stock Ownership Plan E S O P Plan
     
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]      
Maximum number of shares of common stock available for issuance 7,200,000