Basis of Presentation (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Feb. 28, 2019	Nov. 30, 2018	Aug. 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	Feb. 28, 2019	Feb. 28, 2018	Jun. 01, 2018	May 31, 2018
New accounting pronouncements adopted
Revenue, practical expedient application of ASC 606							true
Accounts receivable, net	$ 237.6						$ 237.6		$ 170.6	$ 202.0
Inventories	514.7						514.7		443.4	460.7
Contract assets - current	54.9						54.9		49.6
Other current assets	39.3						39.3		25.3	26.2
Other non-current assets	67.5						67.5		99.9	118.9
Accrued liabilities	115.0						115.0		147.4	138.3
Deferred tax liabilities									9.1	15.7
Other liabilities and deferred income									61.1	62.2
Deferred revenue on long-term contracts	89.0						89.0			35.8
Retained earnings	689.6						689.6		712.8	$ 733.2
Sales	529.5			$ 456.3			1,489.1	$ 1,274.8
Cost of sales	444.2						1,254.3
Gross profit	85.3			77.6			234.8	209.9
Provision for income taxes (benefit)	(0.6)			(9.8)			4.7	1.4
Income from continuing operations	27.4			31.3			57.5	55.6
Cash flows provided from operating activities:
Net income (loss)	(37.4)	$ 7.0	$ 15.1	15.5	$ (22.5)	$ 10.6	(15.3)	3.6
Income from continuing operations	27.4			$ 31.3			57.5	55.6
Accounts receivable							(73.3)	34.8
Contract assets							(5.2)
Inventories							(71.8)	(36.7)
Accrued and other liabilities							2.8	(12.0)
Other							34.7	$ (17.8)
ASC 606 Adjustments
New accounting pronouncements adopted
Accounts receivable, net									(31.4)
Inventories									(17.3)
Contract assets - current									49.6
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	39.5						39.5
Inventories	21.4						21.4
Contract assets - current	(54.9)						(54.9)
Other current assets	0.2						0.2
Other non-current assets	24.1						24.1
Accrued liabilities	(3.1)						(3.1)
Deferred tax liabilities	6.6						6.6
Deferred revenue on long-term contracts	7.4						7.4
Retained earnings	19.4						19.4
Sales	0.1						(5.3)
Cost of sales	(1.0)						(4.1)
Gross profit	1.1						(1.2)
Provision for income taxes (benefit)	0.2						(0.3)
Income from continuing operations	0.9						(0.9)
Cash flows provided from operating activities:
Net income (loss)							(0.9)
Income from continuing operations	0.9						(0.9)
Accounts receivable							(8.1)
Contract assets							5.2
Inventories							(4.1)
Accrued and other liabilities							6.0
Other							1.9
ASU 2014-09 | Balances Excluding ASC 606
New accounting pronouncements adopted
Accounts receivable, net	277.1						277.1
Inventories	536.1						536.1
Other current assets	39.5						39.5
Other non-current assets	91.6						91.6
Accrued liabilities	111.9						111.9
Deferred tax liabilities	6.6						6.6
Deferred revenue on long-term contracts	96.4						96.4
Retained earnings	709.0						709.0
Sales	529.6						1,483.8
Cost of sales	443.2						1,250.2
Gross profit	86.4						233.6
Provision for income taxes (benefit)	(0.4)						4.4
Income from continuing operations	28.3						56.6
Cash flows provided from operating activities:
Net income (loss)							(16.2)
Income from continuing operations	28.3						56.6
Accounts receivable							(81.4)
Inventories							(75.9)
Accrued and other liabilities							8.8
Other							36.6
ASU 2017-07 | Other expense, net
New accounting pronouncements adopted
Pension income	$ 0.1						$ 0.7