Goodwill Changes in the Carrying Amount of Goodwill (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016	Jan. 31, 2017	Jan. 31, 2016
Goodwill [Roll Forward]
Goodwill gross, beginning of the period					$ 1,710,300,000	$ 1,684,200,000
Less: accumulated impairment losses, beginning of the period (as of February 1, 2017 and February 1, 2016, respectively)					(149,200,000)	$ (149,200,000)
Goodwill net, beginning of the period			$ 1,561,100,000	$ 1,535,000,000	1,535,000,000
Additions arising from acquisitions during the period			0		62,800,000
Effect of foreign currency translation, purchase accounting adjustments, and other			27,500,000		(36,700,000)
Goodwill net, end of the period	$ 1,588,600,000		1,588,600,000		$ 1,561,100,000
Goodwill impairment	$ 0	$ 0	$ 0	$ 0