Revenue Recognition - Contract Assets and Liabilities and Remaining Performance Obligations (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2019	Nov. 30, 2018	Nov. 30, 2019	Nov. 30, 2018	May 31, 2019
Contract Assets and Liabilities
Contract assets - current	$ 62.2		$ 62.2		$ 59.2
Contract assets - non-current	32.0		32.0		17.0
Deferred revenue - current	(11.3)		(11.3)		(12.6)
Deferred revenue on long-term contracts	(122.5)		(122.5)		(83.8)
Net contract liabilities	(39.6)		(39.6)		$ (20.2)
Change in contract assets - current			3.0
Change in contract assets - non-current			15.0
Change in contract liabilities - current			1.3
Change in contract liabilities - non-current			(38.7)
Change in net contract assets (liabilities)			(19.4)
Change in Contract with Customer, Liability
Deferred revenue at beginning of period	(86.3)	$ (58.5)	(96.4)	$ (44.1)
Revenue deferred	(153.7)	(103.5)	(240.3)	(194.0)
Revenue recognized	103.3	76.4	204.3	156.5
Other	2.9	8.0	(1.4)	4.0
Deferred revenue at end of period	(133.8)	$ (77.6)	(133.8)	$ (77.6)
Remaining Performance Obligations
Remaining performance obligation	$ 1,300.0		$ 1,300.0
Revenue, Remaining Performance Obligation, Percentage	40.00%		40.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-05-31
Remaining Performance Obligations
Expected timing of satisfaction of remaining performance obligation	12 months		12 months