Goodwill (Changes in the Carrying Amount of Goodwill) (Details)	3 Months Ended
	Apr. 30, 2018 USD ($)
Goodwill [Roll Forward]
Goodwill gross, beginning of the period	$ 1,769,400,000
Less: accumulated impairment losses, beginning of the period	(149,200,000)
Goodwill net, beginning of the period	1,620,200,000
Effect of foreign currency translation	(15,300,000)
Goodwill net, end of the period	1,604,900,000
Goodwill impairment	$ 0