Fair Value (Estimated Fair Values of Financial Instruments Not Carried at Fair Value) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	$ 530.5	$ 430.2
Estimate of Fair Value, Fair Value Disclosure
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	606.2	486.2
Equity securities	9.3	9.3
Other investments	82.4	20.5
Debt	1,030.7	961.7
Estimate of Fair Value, Fair Value Disclosure | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents	606.2	486.2
Estimate of Fair Value, Fair Value Disclosure | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity securities	9.3	9.3
Other investments	58.6	2.7
Debt	1,030.7	961.7
Estimate of Fair Value, Fair Value Disclosure | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other investments	$ 23.8	$ 17.8