Accounts Receivable (Details) - USD ($) $ in Millions	Nov. 30, 2019	May 31, 2019
Accounts receivable, net	$ 208.5	$ 197.8
Past due accounts receivable	10.1
Allowance for doubtful accounts	6.2
US Government Contract
Accounts receivable, net	62.5	60.4
Unbilled receivables	29.8	31.7
US Government Contract | Trade receivables
Accounts receivable, net	32.7	28.7
All other customers
Accounts receivable, net	146.0	137.4
Unbilled receivables	46.2	44.9
All other customers | Trade receivables
Accounts receivable, net	$ 99.8	$ 92.5