Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2019	May 31, 2018	May 31, 2017
Accumulated Other Comprehensive Loss
Balance at beginning of the period	$ (32.0)	$ (39.9)	$ (44.4)
Other comprehensive income (loss) before reclassifications	(10.4)	6.2	2.9
Amounts reclassified from AOCL	1.5	1.7	1.6
Total other comprehensive income (loss), net of tax	(8.9)	7.9	4.5
Balance at end of the period	(40.9)	(32.0)	(39.9)
Currency Translation Adjustments
Accumulated Other Comprehensive Loss
Balance at beginning of the period	0.3	(1.7)	(1.1)
Other comprehensive income (loss) before reclassifications	(2.4)	2.0	(0.6)
Total other comprehensive income (loss), net of tax	(2.4)	2.0	(0.6)
Balance at end of the period	(2.1)	0.3	(1.7)
Pensions Plans
Accumulated Other Comprehensive Loss
Balance at beginning of the period	(32.3)	(38.2)	(43.3)
Other comprehensive income (loss) before reclassifications	(8.0)	4.2	3.5
Amounts reclassified from AOCL	1.5	1.7	1.6
Total other comprehensive income (loss), net of tax	(6.5)	5.9	5.1
Balance at end of the period	$ (38.8)	$ (32.3)	$ (38.2)