Property And Equipment (Summary Of Property And Equipment) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 4,139.9	$ 4,058.4
Accumulated depreciation and amortization	(2,162.0)	(2,038.6)
Property and equipment, net	1,977.9	2,019.8
Land and Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	21.2	21.5
Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	215.1	216.6
Data Processing Equipment, Furniture and Other Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,024.5	1,046.1
Computer Software, Purchased and Internally Developed [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	2,416.7	2,344.9
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 462.4	$ 429.3