Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Nov. 30, 2022	Aug. 31, 2022	Nov. 30, 2021	Aug. 31, 2021	Nov. 30, 2022	Nov. 30, 2021
Accumulated Other Comprehensive Loss
Balance at beginning of the period	$ (22.7)	$ (19.6)	$ (18.6)	$ (18.3)	$ (19.6)	$ (18.3)
Other comprehensive income before reclassifications	(0.3)		(3.7)		(3.6)	(4.3)
Amounts reclassified from AOCL	0.2		0.1		0.4	0.4
Other comprehensive loss, net of tax	(0.1)	(3.1)	(3.6)	(0.3)	(3.2)	(3.9)
Balance at end of the period	(22.8)	(22.7)	(22.2)	(18.6)	(22.8)	(22.2)
Currency Translation Adjustments
Accumulated Other Comprehensive Loss
Balance at beginning of the period	(6.1)	(2.8)	3.3	3.9	(2.8)	3.9
Other comprehensive income before reclassifications	(0.3)		(3.7)		(3.6)	(4.3)
Amounts reclassified from AOCL			(0.2)			(0.2)
Other comprehensive loss, net of tax	(0.3)		(3.9)		(3.6)	(4.5)
Balance at end of the period	(6.4)	(6.1)	(0.6)	3.3	(6.4)	(0.6)
Pension Plans
Accumulated Other Comprehensive Loss
Balance at beginning of the period	(16.6)	(16.8)	(21.9)	(22.2)	(16.8)	(22.2)
Amounts reclassified from AOCL	0.2		0.3		0.4	0.6
Other comprehensive loss, net of tax	0.2		0.3		0.4	0.6
Balance at end of the period	$ (16.4)	$ (16.6)	$ (21.6)	$ (21.9)	$ (16.4)	$ (21.6)