Recently Issued Accounting Standards (Adoption of New Accounting Standard - Income Statement) (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended							9 Months Ended
		Feb. 01, 2018	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Oct. 31, 2018	Oct. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			$ 660.9				$ 515.3			$ 1,832.5	$ 1,502.8
Marketing and sales			297.6				272.5			863.1	785.8
Provision for income taxes			(35.2)				(8.6)			(69.8)	(34.4)
Net loss			$ (23.7)	$ (39.4)	$ (82.4)	$ (173.5)	$ (119.8)	$ (144.0)	$ (129.6)	$ (145.5)	$ (393.4)
Basic net loss per share (in usd per share)			$ (0.11)				$ (0.55)			$ (0.67)	$ (1.79)
Diluted net loss per share (in usd per share)			$ (0.11)				$ (0.55)			$ (0.67)	$ (1.79)
As Adjusted
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Marketing and sales			$ 290.9							$ 832.0
Provision for income taxes			(25.7)							(61.8)
Net loss			$ (17.7)							$ (104.8)
Basic net loss per share (in usd per share)			$ (0.08)							$ (0.48)
Diluted net loss per share (in usd per share)			$ (0.08)							$ (0.48)
Accounting Standards Update 2014-09 | Impact from the adoption of ASC 606 and 340-40
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue		$ 89.0
Marketing and sales			$ (6.7)							$ (31.1)
Provision for income taxes			9.5							8.0
Net loss			$ 6.0							$ 40.7
Basic net loss per share (in usd per share)			$ 0.03							$ 0.19
Diluted net loss per share (in usd per share)			$ 0.03							$ 0.19
Maintenance and subscription
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			$ 631.4				$ 475.5			$ 1,750.0	$ 1,370.4
Cost of revenue			54.8				53.9			159.3	161.6
Maintenance and subscription | As Adjusted
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of revenue			54.8							159.2
Maintenance and subscription | Accounting Standards Update 2014-09 | Impact from the adoption of ASC 606 and 340-40
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of revenue			0.0							(0.1)
Subscription
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			481.3				231.1			1,252.3	600.6
Subscription | As Adjusted
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			472.9							1,245.6
Subscription | Accounting Standards Update 2014-09 | Impact from the adoption of ASC 606 and 340-40
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			(8.4)							(6.7)
Maintenance
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			150.1				244.4			497.7	769.8
Maintenance | As Adjusted
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			149.3							501.2
Maintenance | Accounting Standards Update 2014-09 | Impact from the adoption of ASC 606 and 340-40
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			(0.8)							3.5
Other
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue	[1]		29.5				39.8			82.5	132.4
Cost of revenue	[2]		13.9				$ 19.6			39.0	$ 56.0
Other | As Adjusted
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			28.8							88.2
Cost of revenue			14.2							40.0
Other | Accounting Standards Update 2014-09 | Impact from the adoption of ASC 606 and 340-40
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			(0.7)							5.7
Cost of revenue			$ 0.3							$ 1.0

[1] Previously labeled as "License and other" in prior periods.

[2] Previously labeled as "Cost of license and other revenue" in prior periods.