Goodwill (Changes in the Carrying Amount of Goodwill) (Details)	3 Months Ended
	Apr. 30, 2020 USD ($)
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	(14,800,000)
Goodwill net, end of the period	2,430,200,000
Goodwill impairment loss	$ 0