Business and Summary of Significant Accounting Policies - Computer Equipment, Software, Furniture and Leasehold Improvements, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Property, Plant and Equipment [Abstract]
Depreciation	$ 73.1	$ 60.6	$ 52.1
Computer hardware, at cost	206.1	202.7
Computer software, at cost	73.5	85.6
Leasehold improvements, land and buildings, at cost	206.3	202.9
Furniture and equipment, at cost	58.2	59.0
Computer software, hardware, leasehold improvements, furniture, and equipment, at cost	544.1	550.2
Less: Accumulated depreciation	(385.5)	(380.9)
Computer software, hardware, leasehold improvements, furniture, and equipment, net	$ 158.6	$ 169.3
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