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Employee Benefit Plans - Additional Information (Detail) (USD $)
Share data in Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]      
Percentage of amount vested to defined contribution retirement savings plan 100.00%    
Expense for continuing and discontinued operations under employee benefit plan $ 11,900,000 $ 12,800,000 $ 11,500,000
Percentage of fair market value of common stock 95.00%    
Percentage of shares limited to an employee under employee stock purchase plan 10.00%    
Maximum salary of employee allowed to purchase shares under employee stock purchase plan $ 25,000    
Common stock issued under employee stock purchase plan 2.6    
Employee Stock Purchase Plan [Member]
      
Defined Benefit Plan Disclosure [Line Items]      
Authorized to grant the common stock under the employee stock purchase plan 4.0    
0-2% Contribution [Member]
      
Defined Benefit Plan Disclosure [Line Items]      
Percentage of amount contributed to defined contribution retirement savings plan 100.00%    
2-4% Contribution [Member]
      
Defined Benefit Plan Disclosure [Line Items]      
Percentage of amount contributed to defined contribution retirement savings plan 50.00%