Fair Value Measurements (Details) (Fair value measured on a recurring basis, USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Estimated Fair Value
Fair value measurements
Deferred compensation liabilities	$ (41.8)	$ (43.8)
Derivative instruments	(0.3)	(2.3)
Total	689.9	671.9
Estimated Fair Value \| Equity securities
Fair value measurements
Investments	693.6	651.7
Estimated Fair Value \| Investments in pooled funds
Fair value measurements
Investments	34.3	47.9
Estimated Fair Value \| Fixed income securities
Fair value measurements
Investments	4.1	18.4
Quoted prices in Active Markets for Identical Assets (Level 1)
Fair value measurements
Deferred compensation liabilities	(41.8)	(43.8)
Total	651.8	607.9
Quoted prices in Active Markets for Identical Assets (Level 1) \| Equity securities
Fair value measurements
Investments	693.6	651.7
Significant Other Observable Inputs (Level 2)
Fair value measurements
Derivative instruments	(0.3)	(2.3)
Total	38.1	64.0
Significant Other Observable Inputs (Level 2) \| Investments in pooled funds
Fair value measurements
Investments	34.3	47.9
Significant Other Observable Inputs (Level 2) \| Fixed income securities
Fair value measurements
Investments	$ 4.1	$ 18.4

Derivative instrument obligations meeting the definition of a liability which the Company is a party to as of the balance sheet date.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investment securities as of the balance sheet date which may include marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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