Estimated Fair Values of Financial Instruments Not Carried at Fair Value (Detail) (Estimate of Fair Value, Fair Value Disclosure, USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 462.0
Equity securities	9.7
Other investments	15.7
Debt	1,065.3
Fair Value, Inputs, Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	462.0
Fair Value, Inputs, Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	9.7
Other investments	5.1
Debt	1,065.3
Fair Value, Inputs, Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other investments	$ 10.6