CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2018	Nov. 30, 2017	Nov. 30, 2018	Nov. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 71.6	$ 57.1	$ 10.3	$ (6.6)
Other comprehensive income (loss), net:
Foreign currency translation adjustments	(0.6)	0.1	(3.7)	3.8
Pension and postretirement adjustments (net of tax)	2.7	9.0	2.9	9.5
Total other comprehensive income (loss), net	2.1	9.1	(0.8)	13.3
Comprehensive income (loss)	$ 73.7	$ 66.2	$ 9.5	$ 6.7