Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2021	May 31, 2020	May 31, 2019
Allowance for Doubtful Accounts
Other liabilities	$ 29.5	$ 34.4
Balance, beginning of year	22.1	16.0	$ 7.5
Provision charged to operations	8.5	5.4	15.8
Recoveries, deductions for accounts written off and other reclassifications	(14.2)	0.7	(7.3)
Balance, end of year	$ 16.4	22.1	16.0
European airline customer
Allowance for Doubtful Accounts
Impairment of non-current contract assets			7.6
Other liabilities			1.5
Balance, beginning of year		$ 3.3
Provision charged to operations			12.4
Balance, end of year			$ 3.3