Business and Summary of Significant Accounting Policies - Computer Equipment, Software, Furniture and Leasehold Improvements, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Property, Plant and Equipment [Abstract]
Depreciation	$ 60.6	$ 52.1	$ 47.2
Computer hardware, at cost	202.7	194.0
Computer software, at cost	85.6	84.9
Leasehold improvements, land, and buildings, at cost	202.9	176.3
Furniture and equipment, at cost	59.0	53.0
Computer software, hardware, leasehold improvements, furniture, and equipment, at cost	550.2	508.2
Less: Accumulated depreciation	(380.9)	(349.0)
Computer software, hardware, leasehold improvements, furniture, and equipment, net	$ 169.3	$ 159.2
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