Annual report pursuant to Section 13 and 15(d)

Total Stock-Based Compensation Expense (Detail)

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Total Stock-Based Compensation Expense (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Stock-based compensation expense $ 28.0 $ 24.4 $ 21.8
Cost of services
      
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Stock-based compensation expense 3.9 3.6 3.6
Selling, general and administrative expenses
      
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]      
Stock-based compensation expense $ 24.1 $ 20.8 $ 18.2