Accumulated Other Comprehensive Income (Loss) - Schedule of AOCI Activity (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (86.7)	$ (77.0)
Other comprehensive income (loss) before reclassifications	(9.1)	(12.7)
Other comprehensive income (loss)	(7.5)	(9.7)
Ending balance	(94.2)	(86.7)	$ (77.0)
Pension and postretirement adjustments, tax portion	22.0	22.4	20.6
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(40.0)	(31.9)
Other comprehensive income (loss) before reclassifications	(5.3)	(8.1)
Other comprehensive income (loss)	(5.3)	(8.1)
Ending balance	(45.3)	(40.0)	(31.9)
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
Recognized net actuarial loss [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from Accumulated other comprehensive income (loss)	1.6	3.0
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	(39.4)	(38.0)
Other comprehensive income (loss) before reclassifications	(8.8)	(2.8)
Other comprehensive income (loss)	(7.5)	(1.4)
Ending balance	(46.9)	(39.4)	(38.0)
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)	0.0	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)	1.3	1.4
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	(7.3)	(7.1)
Other comprehensive income (loss) before reclassifications	5.0	(1.8)
Other comprehensive income (loss)	5.3	(0.2)
Ending balance	(2.0)	(7.3)	$ (7.1)
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)	0.3	1.6
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