Business Segment Information - Financial information for each segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 28, 2026	Feb. 28, 2025	Feb. 28, 2026	Feb. 28, 2025	May 31, 2025
Business Segment Information
Capital expenditures	$ 8.5	$ 8.5	$ 24.6	$ 24.7
Depreciation and amortization	23.9	19.6	64.4	57.1
Earnings (Loss) from joint ventures	1.4	0.5	4.3	4.7
Total assets	3,332.5		3,332.5		$ 2,844.6
Investments in joint ventures	42.6		42.6		32.3
Discontinued operations | Corporate
Business Segment Information
Capital expenditures	0.5	0.6	1.5	1.3
Depreciation and amortization	3.2	4.9	11.9	14.7
Total assets	125.6		125.6		170.8
Parts Supply
Business Segment Information
Capital expenditures	0.4	0.1	0.7	0.2
Depreciation and amortization	7.7	2.5	16.2	7.4
Earnings (Loss) from joint ventures	1.3	0.7	4.9	1.3
Total assets	1,154.6		1,154.6		818.8
Investments in joint ventures	13.3		13.3		8.4
Repair & Engineering
Business Segment Information
Capital expenditures	4.3	6.3	13.2	14.2
Depreciation and amortization	7.8	7.1	21.1	20.1
Earnings (Loss) from joint ventures	0.1	(0.2)	(0.6)	3.4
Total assets	1,368.2		1,368.2		1,155.2
Investments in joint ventures	29.3		29.3		23.9
Integrated Solutions
Business Segment Information
Capital expenditures	2.4	0.9	6.5	3.9
Depreciation and amortization	4.8	4.7	13.9	13.7
Total assets	597.6		597.6		620.8
Expeditionary Services
Business Segment Information
Capital expenditures	0.9	0.6	2.7	5.1
Depreciation and amortization	0.4	$ 0.4	1.3	$ 1.2
Total assets	$ 86.5		$ 86.5		$ 79.0