Business Segment Information - Customers Percentage of Sales (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2022	May 31, 2021	May 31, 2020
Business Segment Information
Net sales	$ 1,820.0	$ 1,652.3	$ 2,072.0
U.S. Department of Defense, other U.S. government agencies and their contractors
Business Segment Information
Net sales	620.0	738.8	668.2
Aviation Services
Business Segment Information
Net sales	1,745.8	1,553.7	1,964.2
Aviation Services | U.S. Department of Defense, other U.S. government agencies and their contractors
Business Segment Information
Net sales	557.4	657.0	588.7
Expeditionary Services
Business Segment Information
Net sales	74.2	98.6	107.8
Expeditionary Services | U.S. Department of Defense, other U.S. government agencies and their contractors
Business Segment Information
Net sales	$ 62.6	$ 81.8	$ 79.5
Customer | Total sales | U.S. Department of Defense, other U.S. government agencies and their contractors
Business Segment Information
Percentage of total sales	34.10%	44.70%	32.20%