Goodwill Changes in the Carrying Amount of Goodwill 2 (Details) - USD ($)	3 Months Ended	12 Months Ended
	Apr. 30, 2017	Jan. 31, 2017	Jan. 31, 2016
Goodwill [Roll Forward]
Goodwill, beginning of the period	$ 1,710,300,000	$ 1,684,200,000
Less: accumulated impairment losses, beginning of the period		(149,200,000)	$ (149,200,000)
Additions arising from acquisitions during the period	0	62,800,000
Effect of foreign currency translation, purchase accounting adjustments, and other	9,600,000	(36,700,000)
Goodwill, end of the period	$ 1,570,700,000	1,561,100,000
Goodwill impairment		$ 0	$ 0