Goodwill (Changes in the Carrying Amount of Goodwill) (Details) - USD ($)	3 Months Ended	6 Months Ended
	Jul. 31, 2020	Jul. 31, 2020
Goodwill [Roll Forward]
Goodwill gross, beginning of the period		$ 2,594,200,000
Less: accumulated impairment losses, beginning of the period		(149,200,000)
Goodwill net, beginning of the period		2,445,000,000.0
Effect of foreign currency translation, measurement period adjustments, and other		14,100,000
Goodwill net, end of the period	$ 2,459,100,000	2,459,100,000
Goodwill impairment loss	$ 0	$ 0