Fair Value Measurements (Details) (Fair value measured on a recurring basis, USD $)	Jun. 30, 2014		Dec. 31, 2013
Money market funds
Fair value measurements
Investments	$ 201,100,000	[1]	$ 170,500,000	[1]
Estimated Fair Value
Fair value measurements
Deferred compensation liabilities	(29,700,000)	[2]	(44,300,000)	[2]
Derivative Liability	600,000	[2]	800,000	[2]
Total	778,800,000		836,100,000
Estimated Fair Value | Equity securities
Fair value measurements
Investments	603,700,000	[3]	698,000,000	[3]
Estimated Fair Value | Pooled funds
Fair value measurements
Investments	4,300,000	[3]	12,400,000	[3]
Estimated Fair Value | Fixed income securities
Fair value measurements
Investments			300,000	[3]
Quoted prices in Active Markets for Identical Assets (Level 1)
Fair value measurements
Deferred compensation liabilities	(29,700,000)	[2]	(44,300,000)	[2]
Derivative Liability	0	[2]	0	[2]
Total	775,100,000		824,200,000
Quoted prices in Active Markets for Identical Assets (Level 1) | Money market funds
Fair value measurements
Investments	201,100,000	[1]	170,500,000	[1]
Quoted prices in Active Markets for Identical Assets (Level 1) | Equity securities
Fair value measurements
Investments	603,700,000	[3]	698,000,000	[3]
Quoted prices in Active Markets for Identical Assets (Level 1) | Pooled funds
Fair value measurements
Investments	0	[3]	0	[3]
Quoted prices in Active Markets for Identical Assets (Level 1) | Fixed income securities
Fair value measurements
Investments			0	[3]
Significant Other Observable Inputs (Level 2)
Fair value measurements
Deferred compensation liabilities	0	[2]	0	[2]
Derivative Liability	600,000	[2]	800,000	[2]
Total	3,700,000		11,900,000
Significant Other Observable Inputs (Level 2) | Money market funds
Fair value measurements
Investments	0	[1]	0	[1]
Significant Other Observable Inputs (Level 2) | Equity securities
Fair value measurements
Investments	0	[3]	0	[3]
Significant Other Observable Inputs (Level 2) | Pooled funds
Fair value measurements
Investments	4,300,000	[3]	12,400,000	[3]
Significant Other Observable Inputs (Level 2) | Fixed income securities
Fair value measurements
Investments			300,000	[3]
Fair Value, Inputs, Level 3 [Member]
Fair value measurements
Deferred compensation liabilities	0	[2]	0	[2]
Derivative Liability	0	[2]	0.0	[2]
Total	0		0
Fair Value, Inputs, Level 3 [Member] | Money market funds
Fair value measurements
Investments	0	[1]	0	[1]
Fair Value, Inputs, Level 3 [Member] | Equity securities
Fair value measurements
Investments	0	[3]	0	[3]
Fair Value, Inputs, Level 3 [Member] | Pooled funds
Fair value measurements
Investments	0	[3]	0	[3]
Fair Value, Inputs, Level 3 [Member] | Fixed income securities
Fair value measurements
Investments			$ 0	[3]

[1] (1) Included in Cash and cash equivalents, Funds held on behalf of clients and Other assets on the Company’s Condensed Consolidated Balance Sheet.

[2] (3) Included in Other liabilities on the Company’s Condensed Consolidated Balance Sheet.

[3] (2) Included in Investments on the Company’s Condensed Consolidated Balance Sheet.