Business and Summary of Significant Accounting Policies - Changes In the Carrying Amount of Goodwill (Details) - USD ($)	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Accounting Policies [Abstract]
Impairment of goodwill	$ 0	$ 0	$ 0
Goodwill [Roll Forward]
Goodwill, beginning of period, gross		2,600,000,000.0	1,769,400,000
Less: accumulated impairment losses, beginning of the year		(149,200,000)	$ (149,200,000)
Additions arising from acquisitions during the year	0	866,900,000
Effect of foreign currency translation and measurement period adjustments	(5,800,000)	(36,300,000)
Goodwill, end of period, net	$ 2,445,000,000.0	$ 2,450,800,000