Revenue Recognition - Contract Assets and Liabilities and Remaining Performance Obligations (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Nov. 30, 2020	Aug. 31, 2020	Nov. 30, 2019	Nov. 30, 2020	Nov. 30, 2019	May 31, 2020
Contract Assets and Liabilities
Contract assets - current	$ 52.8			$ 52.8		$ 49.3
Contract assets - non-current	24.1			24.1		22.4
Contract liabilities:
Deferred revenue - current	(18.1)			(18.1)		(11.2)
Deferred revenue on long-term contracts	(30.3)			(30.3)		(88.0)
Net contract assets (liabilities)	28.5			28.5		(27.5)
Change in contract assets - current				3.5
Change in contract assets - non-current				1.7
Change in contract liabilities - current				(6.9)
Change in contract liabilities - non-current				57.7
Change in net contract assets (liabilities)				56.0
Charge related to terminiation of PBH customer contract		$ 2.2
PBH forward loss reserve	4.2			4.2
Forward loss reserves	8.4			8.4
Forward loss reserves classified as current in accrued liabilities	19.4			19.4		$ 22.1
Change in Contract with Customer, Liability
Deferred revenue at beginning of period	(85.4)	(99.2)	$ (86.3)	(99.2)	$ (96.4)
Revenue deferred	(50.8)		(153.7)	(123.0)	(240.3)
Revenue recognized	87.6		103.3	176.1	204.3
Other	0.2		2.9	(2.3)	(1.4)
Deferred revenue at end of period	(48.4)	$ (85.4)	$ (133.8)	(48.4)	$ (133.8)
Remaining Performance Obligations
Remaining performance obligation	$ 750.0			$ 750.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-05-31
Remaining Performance Obligations
Remaining performance obligation (as a percent)	50.00%			50.00%
Expected timing of satisfaction of remaining performance obligation	12 months			12 months
Accrued liabilities
Contract liabilities:
PBH forward loss reserve	$ 3.7			$ 3.7
Other liabilities
Contract liabilities:
PBH forward loss reserve	$ 0.5			0.5
PBH contracts
Contract liabilities:
Contract Charges on non-achievement of minimum volume guarantees				$ 4.5