Business Segment Information - Reconciliation of segment operating income to income from continuing operations before provision for income taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2023	Nov. 30, 2022	Nov. 30, 2023	Nov. 30, 2022
Business Segment Information
Operating income	$ 38.3	$ 32.4	$ 63.6	$ 63.6
Pension settlement charge			(26.7)
Losses related to sale and exit of business	(0.9)	(0.1)	(1.6)	(0.1)
Other income (expense), net	(0.1)	0.5	(0.1)	0.7
Interest expense	(6.2)	(2.1)	(12.0)	(3.2)
Interest income	0.6	0.1	1.0	0.2
Income from continuing operations before income taxes	31.7	30.8	24.2	61.2
Operating segments
Business Segment Information
Operating income	47.0	39.0	80.2	75.3
Operating segments | Parts Supply
Business Segment Information
Operating income	28.4	21.3	43.5	39.6
Operating segments | Repair & Engineering
Business Segment Information
Operating income	11.3	8.6	20.4	16.0
Operating segments | Integrated Solutions
Business Segment Information
Operating income	6.4	7.1	14.1	15.4
Operating segments | Expeditionary Services
Business Segment Information
Operating income	0.9	2.0	2.2	4.3
Corporate and other
Business Segment Information
Operating income	$ (8.7)	$ (6.6)	$ (16.6)	$ (11.7)