Taxes (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended		12 Months Ended
	Feb. 28, 2017	Feb. 28, 2018	Feb. 29, 2016	May 31, 2018	May 31, 2017	May 31, 2016	May 31, 2015
Income Tax And Non Income Tax Disclosure [Abstract]
Settlements during the period			$ 4.9	$ 1.9	$ 0.6	$ 2.9
Net deferred tax assets				25.2	53.7
Decrease in deferred tax asset valuation allowance				(0.3)
Increase in deferred tax asset valuation allowance					1.6
Foreign operating loss carryforwards				110.2
Unrecognized tax benefits				10.1	14.1	17.9	$ 17.3
Income tax penalties and interest accrued				1.8	1.7	2.3
Unrecognized tax benefits that would impact effective tax rate				10.1	14.1	17.0
Tax (expense) benefit from income tax penalties and interest expense				0.1	(0.6)	(0.5)
Period increase (decrease) in unrecognized tax benefits				(4.0)	(3.8)
Loss Contingencies [Line Items]
Earnings (loss) from continuing operations before income taxes				(1.5)	87.9	68.7
Remeasurement expense	$ 5.7
State Sales Tax Assessment [Member] | Wisconsin [Member]
Loss Contingencies [Line Items]
Sales and Excise Tax Payable	$ 5.4
Pension Plans [Member] | U.S. [Member]
Loss Contingencies [Line Items]
Settlement charge		$ (57.3)		$ (57.3)	$ 0.0	$ 0.0