Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Jan. 31, 2021	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Federal:
Current									$ 9.8	$ (2.3)	$ (13.3)
Deferred									(741.0)	7.6	(6.7)
State:
Current									19.0	(0.4)	(1.8)
Deferred									(57.5)	2.1	0.1
Foreign:
Current									87.6	69.6	65.3
Deferred									20.6	3.7	(5.5)
Income tax provision (benefit)	$ (740.2)	$ 23.9	$ 30.8	$ 24.0	$ (8.5)	$ 29.7	$ 26.3	$ 32.8	$ (661.5)	$ 80.3	$ 38.1