Restructuring charges and other facility exit costs, net (Details) $ in Millions		12 Months Ended
		Jan. 31, 2017 USD ($) Facility Position		Jan. 31, 2016 USD ($)
Restructuring Cost and Reserve [Line Items]
Additions		$ 77.8		$ 0.0
Restructuring Reserve [Roll Forward]
Total, beginning balance		1.3		1.6
Current portion, beginning balance		0.8	[1]	0.7	[2]
Non-current portion, beginning balance		0.5	[1]	0.9	[2]
Additions		77.8		0.0
Payments		(67.6)		(0.5)
Adjustments		(3.1)	[3]	0.2	[4]
Total, ending balance		8.4		1.3
Current portion, ending balance	[1]	6.6		0.8
Non-current portion, ending balance	[1]	1.8		0.5
Total		$ 1.3		1.6
One-time Termination Benefits | Fiscal 2017 Plan
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated | Position		840
Facility Closing
Restructuring Cost and Reserve [Line Items]
Additions		$ 7.4
Lease termination and other exit costs		9.6
Restructuring Reserve [Roll Forward]
Total, beginning balance		0.0
Additions		7.4
Payments		(1.8)
Adjustments		(1.1)
Total, ending balance		4.5		0.0
Total		$ 0.0		0.0
Facility Closing | Fiscal 2017 Plan
Restructuring Cost and Reserve [Line Items]
Number of facilities consolidated | Facility		18
Additions		$ 7.1
Lease termination and other exit costs		7.6
Restructuring Reserve [Roll Forward]
Total, beginning balance
Additions		7.1
Payments		(3.2)
Adjustments		(2.0)
Total, ending balance		1.9
Total
Employee Severance | Fiscal 2017 Plan
Restructuring Cost and Reserve [Line Items]
Additions		63.3
Restructuring Reserve [Roll Forward]
Total, beginning balance		0.0
Additions		63.3
Payments		(62.2)
Adjustments		0.0
Total, ending balance		1.1		0.0
Total		0.0		0.0
Lease Termination | Fiscal 2014 Plan
Restructuring Cost and Reserve [Line Items]
Additions		0.0		0.0
Restructuring Reserve [Roll Forward]
Total, beginning balance		1.2		1.4
Additions		0.0		0.0
Payments		(0.3)		(0.4)
Adjustments		0.0	[3]	0.2
Total, ending balance		0.9		1.2
Total		1.2		1.4
Lease Termination | Fiscal 2013 Plan
Restructuring Cost and Reserve [Line Items]
Additions		0.0		0.0
Restructuring Reserve [Roll Forward]
Total, beginning balance		0.1		0.2
Additions		0.0		0.0
Payments		(0.1)		(0.1)
Adjustments		0.0		0.0
Total, ending balance		0.0		0.1
Total		$ 0.1		$ 0.2

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

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

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

[4] Adjustments include the impact of foreign currency translation.