Discontinued Operations - Revenues (Details) - Discontinued Operations - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 28, 2017	Feb. 29, 2016	Feb. 28, 2017	Feb. 29, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	$ 0.1	$ 0.4	$ 0.3	$ 0.7
Operating costs and expenses	0.0	0.6	0.4	2.2
Interest income (expense)	0.1	0.0	0.1	0.1
Gain (loss) on sale	0.0	(2.9)	0.0	(2.9)
Earnings (loss) before income taxes	0.2	(3.1)	0.0	(4.3)
Provision (benefit) for income taxes	0.1	(1.3)	0.0	(1.7)
Earnings (loss) from discontinued operations, net of tax	$ 0.1	$ (1.8)	$ 0.0	$ (2.6)