Recently Issued Accounting Standards (Adoption of New Accounting Standard - Income Statement) (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended		6 Months Ended
		Feb. 01, 2018	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			$ 611.7	$ 501.8	$ 1,171.6	$ 987.5
Marketing and sales			289.1	257.6	565.5	513.3
Provision for income taxes			(16.0)	(17.6)	(34.6)	(25.8)
Net loss			$ (39.4)	$ (144.0)	$ (121.8)	$ (273.6)
Basic net loss per share (in usd per share)			$ (0.18)	$ (0.66)	$ (0.56)	$ (1.25)
Diluted net loss per share (in usd per share)			$ (0.18)	$ (0.66)	$ (0.56)	$ (1.25)
As Adjusted
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Marketing and sales			$ 278.3		$ 541.1
Provision for income taxes			(12.9)		(36.1)
Net loss			$ (27.1)		$ (87.1)
Basic net loss per share (in usd per share)			$ (0.12)		$ (0.40)
Diluted net loss per share (in usd per share)			$ (0.12)		$ (0.40)
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			$ (10.8)		$ (24.4)
Provision for income taxes			(3.1)		1.5
Net loss			$ 12.3		$ 34.7
Basic net loss per share (in usd per share)			$ 0.06		$ 0.16
Diluted net loss per share (in usd per share)			$ 0.06		$ 0.16
Maintenance and subscription
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			$ 587.0	$ 457.9	$ 1,118.6	$ 894.9
Cost of revenue			54.1	52.8	104.5	107.7
Maintenance and subscription | As Adjusted
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of revenue			54.1		104.4
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			420.6	196.1	771.0	369.5
Subscription | As Adjusted
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			416.0		772.7
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			(4.6)		1.7
Maintenance
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			166.4	261.8	347.6	525.4
Maintenance | As Adjusted
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			165.3		351.9
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			(1.1)		4.3
Other
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue	[1]		24.7	43.9	53.0	92.6
Cost of revenue	[2]		12.3	$ 17.8	25.1	$ 36.4
Other | As Adjusted
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net revenue			29.2		59.4
Cost of revenue			12.7		25.8
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			4.5		6.4
Cost of revenue			$ 0.4		$ 0.7

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

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