Leases (Details 1) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Leases [Abstract]
Operating lease cost	$ 11.1	$ 12.9	$ 22.4	$ 25.3
Finance lease cost:
Amortization of right-of-use assets	0.6	0.8	1.2	1.6
Interest on lease liabilities	0.0	0.0	0.1	0.1
Variable lease cost	5.5	6.3	11.1	12.6
Short-term lease cost	10.3	9.7	19.3	17.4
Sublease income	(1.0)	(1.5)	(2.5)	(2.3)
Net lease cost	$ 26.5	$ 28.2	$ 51.6	$ 54.7