Business Segment Information - Financial information for each segment (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2025	Aug. 31, 2024	May 31, 2025
Business Segment Information
Capital expenditures	$ 8.7	$ 7.9
Depreciation and amortization	19.1	18.5
Earnings from joint ventures	3.0	2.3
Total assets	2,929.7		$ 2,844.6
Investments in joint ventures	34.8		32.3
Discontinued operations | Corporate
Business Segment Information
Capital expenditures	0.7	0.4
Depreciation and amortization	4.7	4.9
Total assets	146.0		170.8
Parts Supply
Business Segment Information
Capital expenditures	0.3
Depreciation and amortization	2.9	2.6
Earnings from joint ventures	2.9	0.5
Total assets	875.0		818.8
Investments in joint ventures	11.3		8.4
Repair & Engineering
Business Segment Information
Capital expenditures	4.9	2.5
Depreciation and amortization	6.6	6.6
Earnings from joint ventures	0.1	1.8
Total assets	1,166.1		1,155.2
Investments in joint ventures	23.5		23.9
Integrated Solutions
Business Segment Information
Capital expenditures	2.1	1.6
Depreciation and amortization	4.5	4.0
Total assets	660.0		620.8
Expeditionary Services
Business Segment Information
Capital expenditures	0.7	3.4
Depreciation and amortization	0.4	$ 0.4
Total assets	$ 82.6		$ 79.0