Revenue Recognition Adoption of New Accounting Standard - Balance Sheet (Details) (Details) - USD ($) $ in Millions	Feb. 01, 2018	Jan. 31, 2020	Jan. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net		$ 652.3	$ 474.3
Prepaid expenses and other current assets		163.3	192.1
Deferred income taxes, net		56.4	65.3
Long-term income taxes payable		19.1	21.5
Long-term deferred income taxes		82.5	79.8
Accumulated deficit		$ (2,295.8)	(2,147.4)
As reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net			474.3
Prepaid expenses and other current assets			192.1
Deferred income taxes, net			65.3
Other assets			337.8
Deferred revenue, current			1,763.3
Other accrued liabilities			142.3
Long-term deferred revenue			328.1
Long-term income taxes payable			21.5
Long-term deferred income taxes			79.8
Accumulated deficit			(2,147.4)
Impact from the adoption of ASC 606 and 340-40
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net			547.7
Prepaid expenses and other current assets			112.7
Deferred income taxes, net			72.3
Other assets			319.9
Deferred revenue, current			1,903.9
Other accrued liabilities			144.0
Long-term deferred revenue			365.3
Long-term income taxes payable			21.3
Long-term deferred income taxes			73.1
Accumulated deficit			(2,336.9)
Cumulative effect on retained earnings	$ 179.4
Impact from the adoption of ASC 606 and 340-40 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net			73.4
Prepaid expenses and other current assets			(79.4)
Deferred income taxes, net			7.0
Other assets			(17.9)
Deferred revenue, current			140.6
Other accrued liabilities			1.7
Long-term deferred revenue			37.2
Long-term income taxes payable			(0.2)
Long-term deferred income taxes			(6.7)
Accumulated deficit			$ (189.5)