Restructuring charges and other facility exit costs, net (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Feb. 29, 2016	Jan. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring costs expected completion date				2017
Restructuring Reserve [Roll Forward]
Beginning Balance				$ 0.0
Additions		$ 3.2	$ 0.0	71.5	$ 0.0
Payments				(57.5)
Adjustments	[1]			(5.4)
Ending Balance		8.6		8.6
Current portion	[2]					$ 7.0		$ 0.0
Non-current portion	[2]					1.6		0.0
Total Restructuring Reserve		8.6		0.0		8.6		0.0
Lease termination and other exit costs
Restructuring Reserve [Roll Forward]
Additions				7.4
Payments				(1.0)
Adjustments	[1]			(3.5)
Ending Balance		2.9		2.9
Total Restructuring Reserve		2.9		2.9		2.9
Fiscal 2017 Plan | Employee termination costs
Restructuring Cost and Reserve [Line Items]
Expected cost							$ 65.0
Restructuring Reserve [Roll Forward]
Beginning Balance				0.0
Additions		2.8		58.5
Payments				(54.0)
Adjustments	[1]			0.0
Ending Balance		4.5		4.5
Total Restructuring Reserve		4.5		0.0		4.5		0.0
Fiscal 2017 Plan | Lease termination and other exit costs
Restructuring Cost and Reserve [Line Items]
Expected cost							$ 7.0
Restructuring Reserve [Roll Forward]
Beginning Balance				0.0
Additions		0.4		5.6
Payments				(2.5)
Adjustments	[1]			(1.9)
Ending Balance		1.2		1.2
Total Restructuring Reserve		$ 1.2		$ 0.0		$ 1.2		$ 0.0

[1] Adjustments include the impact of computer equipment, software, furniture, straight-line rent and leasehold improvement write-offs, and foreign currency translation.

[2] The current and non-current portions of the reserve are recorded in the Condensed Consolidated Balance Sheets under “Other accrued liabilities” and “Other liabilities,” respectively.