Business and Summary of Significant Accounting Policies - Computer Equipment, Software, Furniture and Leasehold Improvements, Net (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Jan. 31, 2015	Jan. 31, 2014	Jan. 31, 2013
Property, Plant and Equipment [Abstract]
Depreciation	$ 52.1	$ 47.2	$ 45.6
Computer hardware, at cost	194.0	163.0
Computer software, at cost	84.9	80.9
Leasehold improvements, land, and buildings, at cost	176.3	163.7
Furniture and equipment, at cost	53.0	51.7
Computer software, hardware, leasehold improvements, furniture, and equipment, at cost	508.2	459.3
Less: Accumulated depreciation	(349.0)	(329.0)
Computer software, hardware, leasehold improvements, furniture, and equipment, net	159.2	130.3
Write off of fully depreciated assets	$ 25.8
Software and Software Development Costs
Property, Plant and Equipment [Abstract]
Useful Life	3 years
Minimum
Property, Plant and Equipment [Abstract]
Useful Life	3 years
Maximum
Property, Plant and Equipment [Abstract]
Useful Life	5 years