Supplementary Data Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Depreciation, Depletion and Amortization	$ 130.9	$ 133.7	$ 133.2
Furniture and equipment	585.1	640.7
Leasehold improvements	570.1	594.0
Internal use computer software	295.2	296.2
Land and buildings	78.7	87.3
Property and Equipment	1,529.1	1,618.2
Less: accumulated depreciation	961.9	1,070.0
Total property and equipment, net	$ 567.2	$ 548.2