Accumulated Other Comprehensive Income (Loss) - Schedule of AOCI Activity (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2018	May 31, 2017	May 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (94.2)	$ (86.7)
Other comprehensive income (loss) before reclassifications	3.6	(9.1)
Other comprehensive income (loss)	38.5	(7.5)
Ending balance	(55.7)	(94.2)	$ (86.7)
Pension and postretirement adjustments, tax portion	1.1	22.0	22.4
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(45.3)	(40.0)
Other comprehensive income (loss) before reclassifications	3.4	(5.3)
Other comprehensive income (loss)	3.4	(5.3)
Ending balance	(41.9)	(45.3)	(40.0)
Lump sum settlement charge [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive income (loss)	33.0	0.0
Recognized net actuarial loss [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive income (loss)	1.9	1.6
Service cost [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive income (loss)	0.0	0.0
Pension Plans [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(46.9)	(39.4)
Other comprehensive income (loss) before reclassifications	(0.4)	(8.8)
Other comprehensive income (loss)	34.4	(7.5)
Ending balance	(12.5)	(46.9)	(39.4)
Pension Plans [Member] | Lump sum settlement charge [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive income (loss)	33.0	0.0
Pension Plans [Member] | Recognized net actuarial loss [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive income (loss)	1.8	1.3
Pension Plans [Member] | Service cost [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive income (loss)	0.0	0.0
Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(2.0)	(7.3)
Other comprehensive income (loss) before reclassifications	0.6	5.0
Other comprehensive income (loss)	0.7	5.3
Ending balance	(1.3)	(2.0)	$ (7.3)
Postretirement Benefits [Member] | Lump sum settlement charge [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive income (loss)	0.0	0.0
Postretirement Benefits [Member] | Recognized net actuarial loss [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive income (loss)	0.1	0.3
Postretirement Benefits [Member] | Service cost [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive income (loss)	$ 0.0	$ 0.0