Accumulated Other Comprehensive Income (Loss) - Schedule of AOCI Activity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2020	Nov. 30, 2019	Nov. 30, 2020	Nov. 30, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 1,147.4	$ 1,196.7	$ 1,180.6	$ 1,272.8
Other comprehensive income (loss) before reclassifications	5.7	3.9	16.4	1.9
Amortization of gains and losses, net of tax	0.2	0.3	0.3	0.5
Amortization of prior service credit (net of tax of $0.1)	(0.1)	(0.1)	(0.1)	(0.1)
Other comprehensive income (loss)	5.8	4.1	16.6	2.3
Ending Balance	1,187.9	1,261.3	1,187.9	1,261.3
Amortization, Tax	(0.0)	(0.0)	0.0	0.0
Amortization of prior service credit, Tax	0.1	0.0	0.1	0.0
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(47.5)	(61.5)	(58.3)	(59.7)
Ending Balance	(41.7)	(57.4)	(41.7)	(57.4)
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(39.3)	(49.1)	(50.0)	(47.1)
Other comprehensive income (loss) before reclassifications	0.4	3.9	11.1	1.9
Amortization of gains and losses, net of tax	0.0	0.0	0.0	0.0
Amortization of prior service credit (net of tax of $0.1)	0.0	0.0	0.0	0.0
Other comprehensive income (loss)	0.4	3.9	11.1	1.9
Ending Balance	(38.9)	(45.2)	(38.9)	(45.2)
Retirement benefit plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(8.2)	(12.4)	(8.3)	(12.6)
Other comprehensive income (loss) before reclassifications	5.3	0.0	5.3	0.0
Amortization of gains and losses, net of tax	0.2	0.3	0.3	0.5
Amortization of prior service credit (net of tax of $0.1)	(0.1)	(0.1)	(0.1)	(0.1)
Other comprehensive income (loss)	5.4	0.2	5.5	0.4
Ending Balance	$ (2.8)	$ (12.2)	$ (2.8)	$ (12.2)