CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 31, 2021	Jul. 31, 2020	Jul. 31, 2021	Jul. 31, 2020
Statement of Comprehensive Income [Abstract]
Net gain on derivative instruments, tax expense (benefit)	$ (1.7)	$ 2.3	$ (3.4)	$ 1.9
Change in net unrealized gain on available-for-sale securities, tax expense (benefit)	0.0	0.0	0.0	0.1
Change in defined pension items, tax expense (benefit)	0.0	0.0	0.0	0.0
Net change in cumulative foreign currency translation (loss) gain, tax expense (benefit)	$ 1.2	$ (0.4)	$ (0.6)	$ (0.4)