CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2018	Aug. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (61.3)	$ (63.7)
Other comprehensive income (loss), net:
Foreign currency translation adjustments	(3.1)	3.7
Pension and postretirement adjustments (net of tax)	0.2	0.5
Total other comprehensive income (loss), net	(2.9)	4.2
Comprehensive income (loss)	$ (64.2)	$ (59.5)