Goodwill Changes in the Carrying Amount of Goodwill (Details) - USD ($)	3 Months Ended	9 Months Ended
	Oct. 31, 2017	Oct. 31, 2017	Jan. 31, 2017
Goodwill [Roll Forward]
Goodwill gross, beginning of the period			$ 1,710,300,000
Less: accumulated impairment losses, beginning of the period			$ (149,200,000)
Goodwill net, beginning of the period		$ 1,561,100,000
Additions arising from acquisitions during the period		0
Effect of foreign currency translation, purchase accounting adjustments, and other during the period		27,600,000
Goodwill net, end of the period	$ 1,588,700,000	1,588,700,000
Goodwill impairment	$ 0	$ 0