Goodwill - Changes in the Carrying Amount of Goodwill (Details)	3 Months Ended		6 Months Ended
	Jul. 31, 2021 USD ($)	Jul. 31, 2020 USD ($)	Jul. 31, 2021 USD ($) reporting_unit segment	Jul. 31, 2020 USD ($)
Goodwill [Roll Forward]
Goodwill, 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			865,500,000
Effect of foreign currency translation and measurement period adjustments			(9,800,000)
Goodwill net, end of the period	$ 3,562,200,000		$ 3,562,200,000
Number of operating segments | segment			1
Number of reporting units | reporting_unit			1
Goodwill impairment loss	$ 0	$ 0	$ 0	$ 0