Discontinued Operations (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Aug. 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2018
Discontinued Operations
Interest expense	$ 2.1			$ 1.7
Operating results for discontinued operations
Sales	20.0			41.3
Cost of sales	(22.3)			(38.4)
Selling, general and administrative expenses	(2.5)			(3.6)
Operating loss from discontinued operations	(4.8)			(0.7)
Provision for income taxes (benefit)	(1.0)			(0.3)
Income (Loss) from discontinued operations	(3.8)			$ (0.4)
Carrying amounts of the major classes of assets and liabilities for our discontinued operations
Inventory, rotable assets, and equipment	100.9				$ 106.1
Accounts receivable, net	10.1				14.7
Other assets	3.7				4.2
Assets of discontinued operations	114.7				125.0
Liabilities of discontinued operations	24.7				25.0
Contractor-Owned, Contractor-Operated | Discontinued Operations, Held-for-sale or Disposed of by Sale
Discontinued Operations
Goodwill impairment charge		$ 9.8
Impairment and other charges			$ 54.2
General corporate overhead	0.0				0.0
Interest expense	$ 0.0				$ 0.0