Goodwill - Changes in the Carrying Amount of Goodwill (Details)	3 Months Ended
	Apr. 30, 2021 USD ($) segment reporting_unit	Apr. 30, 2020 USD ($)
Goodwill [Roll Forward]
Goodwill gross, beginning of the period	$ 2,855,700,000
Less: accumulated impairment losses, beginning of the period	(149,200,000)
Goodwill net, beginning of the period	2,706,500,000
Additions arising from acquisitions during the period	767,200,000
Effect of foreign currency translation	10,300,000
Goodwill net, end of the period	$ 3,484,000,000.0
Number of operating segments | segment	1
Number of reporting units | reporting_unit	1
Goodwill impairment loss	$ 0	$ 0