Quarterly report pursuant to Section 13 or 15(d)

Items Measured at Fair Value on Recurring Basis (Detail)

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Items Measured at Fair Value on Recurring Basis (Detail) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2013
Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Fair Value Interest Rate Swaps(1) $ 10.4 $ 12.2
Fair Value, Measurements, Recurring [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Fair Value Interest Rate Swaps(1) 10.4 [1]  
Notes, due 2014(1) (285.4) [1]  
Deferred Compensation Plan(2) (18.9) [2]  
Total (293.9)  
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Fair Value Interest Rate Swaps(1) 0 [1]  
Notes, due 2014(1) 0 [1]  
Deferred Compensation Plan(2) 0 [2]  
Total 0  
Significant Other Observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Fair Value Interest Rate Swaps(1) 10.4 [1]  
Notes, due 2014(1) (285.4) [1]  
Deferred Compensation Plan(2) (18.9) [2]  
Total (293.9)  
Significant Unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Fair Value Interest Rate Swaps(1) 0 [1]  
Notes, due 2014(1) 0 [1]  
Deferred Compensation Plan(2) 0 [2]  
Total $ 0  
[1] The fair value of our interest rate swaps, which are designated as fair value hedges, and our notes, due in 2014, are based on the present value of expected future cash flows using zero coupon rates and are classified within Level 2 of the fair value hierarchy.
[2] We maintain deferred compensation plans that allow for certain management employees to defer the receipt of compensation (such as salary, incentive compensation and commissions) until a later date based on the terms of the plan. The liability representing benefits accrued for plan participants is valued at the quoted market prices of the participants' investment elections.