Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	5 Months Ended	12 Months Ended
	May 31, 2017	May 31, 2018	May 31, 2019	May 31, 2018	May 31, 2017
Current:
U.S. federal statutory income tax rate (as a percent)		21.00%	21.00%	29.20%	35.00%
Income tax benefit for the re-measurement impact				$ 14.1
Federal			$ 4.8	14.6	$ 9.3
State			0.1	0.1	0.2
Foreign			5.0	1.7	3.1
Total current			9.9	16.4	12.6
Deferred			(5.0)	(12.9)	12.5
Provision for income tax			4.9	3.5	25.1
Reasons for difference between the provision for income taxes on pre-tax income from the amount computed by applying the U.S. federal statutory tax rate
Provision for income tax at the federal statutory rate			18.7	22.5	27.0
Deferred tax re-measurement from the Tax Reform Act				(14.1)
Excess tax benefits from stock-based compensation			(2.7)	(2.9)
State net operating losses			(0.3)	1.3	5.7
Change in valuation allowance for state deferred tax assets			(6.9)	(3.4)	(5.7)
Effective settlement of prior tax positions			(4.7)		(2.2)
Other			0.8	0.1	0.3
Provision for income tax			4.9	3.5	25.1
Income tax expense in discontinued operations	$ (6.7)		(19.9)	(24.0)	(8.8)
Excess income tax benefits			4.9	3.5	25.1
Income before provision for income taxes			89.0	77.2	77.1
Deferred tax assets:
Employee benefits		$ 9.7	9.4	9.7
State net operating losses		8.6	9.0	8.6
Deferred revenue		1.1	7.7	1.1
Inventory costs		15.9	4.9	15.9
Postretirement benefits		2.2	3.7	2.2
Other		4.2	4.8	4.2
Total deferred tax assets		41.7	39.5	41.7
Valuation allowance		(7.0)	(0.1)	(7.0)
Total deferred tax assets net of valuation allowance		34.7	39.4	34.7
Deferred tax liabilities:
Tangible and intangible assets		(50.2)	(36.1)	(50.2)
Other		(0.2)	(0.2)	(0.2)
Total deferred tax liabilities		(50.4)	(36.3)	(50.4)
Net deferred tax assets			3.1
Net deferred tax assets (liabilities)		(15.7)		(15.7)
Reconciliation of unrecognized tax benefits
Balance, beginning of year			4.4	4.4	12.9
Additions for tax positions of prior years					0.4
Effective settlement of prior tax position			(4.4)		(8.9)
Balance, end of year	$ 4.4	4.4		4.4	4.4
Income tax benefit for settlements of IRS examination					(2.2)
Deferred tax liabilities attributable to:
Net deferred tax assets			$ 3.1
Minimum
Deferred tax liabilities:
Period for net operating losses carry forward (in years)			5 years
Maximum
Deferred tax liabilities:
Period for net operating losses carry forward (in years)			20 years
Other Current Assets
Deferred tax liabilities:
Income tax receivable		$ 1.0	$ 1.1	1.0
Domestic
Reasons for difference between the provision for income taxes on pre-tax income from the amount computed by applying the U.S. federal statutory tax rate
Income before provision for income taxes			68.9	58.7	57.7
Foreign
Reasons for difference between the provision for income taxes on pre-tax income from the amount computed by applying the U.S. federal statutory tax rate
Income before provision for income taxes			$ 20.1	$ 18.5	$ 19.4