Consolidated Statements of Comprehensive Income (unaudited) - USD ($) shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Income Statement [Abstract]
Revenue	$ 1,336.8	$ 1,203.5
Operating expenses:
Compensation and benefits	810.4	737.9
Operating, administrative and other	458.2	387.2
Depreciation and amortization	31.2	24.9
Restructuring and acquisition charges	7.6	0.8
Total operating expenses	1,307.4	1,150.8
Operating income	29.4	52.7
Interest Income (Expense), Net	(8.9)	(6.0)
Equity earnings from real estate ventures	13.0	11.3
Income before income taxes and noncontrolling interest	33.5	58.0
Provision for (benefit from) income taxes	8.3	14.7
Net income	25.2	43.3
Net income attributable to noncontrolling interest	(0.5)	1.4
Net income attributable to the Company	25.7	41.9
Net income attributable to common shareholders	$ 25.7	$ 41.9
Basic earnings per common share (in dollars per share)	$ 0.57	$ 0.93
Basic weighted average shares outstanding (in shares)	45,095	44,844
Diluted earnings per common share (in dollars per share)	$ 0.56	$ 0.92
Diluted weighted average shares outstanding (in shares)	45,483	45,374
Other comprehensive income:
Net income attributable to the Company	$ 25.7	$ 41.9
Change in pension liabilities, net of tax	0.0	(0.9)
Foreign currency translation adjustments	13.8	(109.1)
Comprehensive income attributable to the Company	$ 39.5	$ (66.3)