Business and Summary of Significant Accounting Policies - Stock Based Compensation Expense (Details)	12 Months Ended
	Jan. 31, 2020 USD ($) period	Jan. 31, 2019 USD ($)	Jan. 31, 2018 USD ($)
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense related to stock awards and Employee Qualified Stock Purchase Plan (ESPP) purchases	$ 362,400,000	$ 249,500,000	$ 261,400,000
Tax benefit	(1,100,000)	(2,600,000)	(2,600,000)
Stock-based compensation expense related to stock awards and ESPP purchases, net	361,300,000	246,900,000	258,800,000
Market capitalization level of peer group	$ 2,000,000,000.00
Number of exercise periods | period	4
Term of exercise period	6 months
Term of offering period	24 months
Cash dividends paid	$ 0	0	0
Dividend yield	0.00%
Cost of subscription and maintenance revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense related to stock awards and Employee Qualified Stock Purchase Plan (ESPP) purchases	$ 13,800,000	13,200,000	11,900,000
Cost of other revenue
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense related to stock awards and Employee Qualified Stock Purchase Plan (ESPP) purchases	5,800,000	4,300,000	4,000,000.0
Marketing and sales
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense related to stock awards and Employee Qualified Stock Purchase Plan (ESPP) purchases	149,000,000.0	109,400,000	107,300,000
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense related to stock awards and Employee Qualified Stock Purchase Plan (ESPP) purchases	120,800,000	82,600,000	82,900,000
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense related to stock awards and Employee Qualified Stock Purchase Plan (ESPP) purchases	$ 73,000,000.0	$ 40,000,000.0	$ 55,300,000