| Items Measured at Fair Value on Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $) In Millions, unless otherwise specified | Mar. 31, 2012 | Dec. 31, 2011 | |||||
|---|---|---|---|---|---|---|---|
| Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | |||||||
| Fair Value Interest Rate Swaps | $ 14.3 | [1] | $ 14.8 | ||||
| Deferred Compensation Plan | (15.4) | [2] | |||||
| Total | (290.4) | ||||||
| Notes, due 2014 | |||||||
| Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | |||||||
| Notes, due 2014 | (289.3) | [1] | |||||
| Significant Other Observable Inputs (Level 2) | |||||||
| Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | |||||||
| Fair Value Interest Rate Swaps | 14.3 | [1] | |||||
| Deferred Compensation Plan | (15.4) | [2] | |||||
| Total | (290.4) | ||||||
| Significant Other Observable Inputs (Level 2) | Notes, due 2014 | |||||||
| Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items] | |||||||
| Notes, due 2014 | $ (289.3) | [1] | |||||
| 
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