Basis of Presentation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2018	Nov. 30, 2017	Nov. 30, 2018	Nov. 30, 2017	Jun. 01, 2018	May 31, 2018
New accounting pronouncements adopted
Revenue, Practical Expedient, Initial Application and Transition, Completed Contract, Same Reporting Period [true false]			true
Accounts receivable, net	$ 218.6		$ 218.6		$ 170.6	$ 202.0
Contract assets-current	63.0		63.0		49.6
Inventories	495.0		495.0		443.4	460.7
Other current assets	33.0		33.0		25.3	26.2
Other non-current assets	85.8		85.8		99.9	118.9
Accrued liabilities	114.4		114.4		147.4	138.3
Deferred tax liabilities	10.5		10.5		9.1	15.7
Other liabilities and deferred income	95.0		95.0		61.1	62.2
Retained earnings	729.6		729.6		712.8	$ 733.2
Sales	493.3	$ 420.6	959.6	$ 818.5
Cost of sales	415.0		810.1
Gross profit	78.3	70.7	149.5	132.3
Provision for income taxes	3.0	6.8	5.3	11.2
Income from continuing operations	11.2	$ 13.2	30.1	$ 24.2
ASC 606 Adjustments
New accounting pronouncements adopted
Accounts receivable, net					(31.4)
Contract assets-current					49.6
Inventories					(17.3)
Other current assets					(0.9)
Other non-current assets					(19.0)
Accrued liabilities					9.1
Deferred tax liabilities					(6.6)
Other liabilities and deferred income					(1.1)
Retained earnings					(20.4)
ASC 606 Adjustments | Other contracts
New accounting pronouncements adopted
Retained earnings					22.1
ASC 606 Adjustments | Repair services
New accounting pronouncements adopted
Retained earnings					1.3
ASC 606 Adjustments | Manufacturing products
New accounting pronouncements adopted
Retained earnings					$ 0.4
ASU 2014-09 | ASC 606 Adjustments
New accounting pronouncements adopted
Accounts receivable, net	46.8		46.8
Contract assets-current	(63.0)		(63.0)
Inventories	20.1		20.1
Other current assets	0.6		0.6
Other non-current assets	21.5		21.5
Accrued liabilities	(5.0)		(5.0)
Deferred tax liabilities	6.6		6.6
Other liabilities and deferred income	5.6		5.6
Retained earnings	18.8		18.8
Sales	(0.4)		(5.2)
Cost of sales	(1.5)		(3.1)
Gross profit	1.1		(2.1)
Provision for income taxes	0.3		(0.5)
Income from continuing operations	0.8		(1.6)
ASU 2014-09 | Balances Excluding ASC 606
New accounting pronouncements adopted
Accounts receivable, net	265.4		265.4
Inventories	515.1		515.1
Other current assets	33.6		33.6
Other non-current assets	107.3		107.3
Accrued liabilities	109.4		109.4
Deferred tax liabilities	17.1		17.1
Other liabilities and deferred income	100.6		100.6
Retained earnings	748.4		748.4
Sales	492.9		954.4
Cost of sales	413.5		807.0
Gross profit	79.4		147.4
Provision for income taxes	3.3		4.8
Income from continuing operations	12.0		28.5
ASU 2017-07 | Other income (expense), net
New accounting pronouncements adopted
Pension income	$ 0.3		$ 0.6