Accumulated Other Comprehensive Income (Loss) - Schedule of AOCI Activity (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2019	Aug. 31, 2018
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (59.7)	$ (55.7)
Other comprehensive income (loss) before reclassifications	(2.0)	(3.1)
Amortization of gains and losses, net of tax	0.2	0.2
Amortization of prior service credit	0.0
Other comprehensive income (loss)	(1.8)	(2.9)
Ending balance	(61.5)	(58.6)
Amortization, Tax	0.0	0.0
Amortization of prior service credit, Tax	0.0
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(47.1)	(41.9)
Other comprehensive income (loss) before reclassifications	(2.0)	(3.1)
Other comprehensive income (loss)	(2.0)	(3.1)
Ending balance	(49.1)	(45.0)
Retirement benefit plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(12.6)	(13.8)
Other comprehensive income (loss) before reclassifications	0.0	0.0
Amortization of gains and losses, net of tax	0.2	0.2
Amortization of prior service credit	0.0
Other comprehensive income (loss)	0.2	0.2
Ending balance	$ (12.4)	$ (13.6)