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Summary of Significant Accounting Policies - Financial Instruments (Details) - USD ($) $ in Millions	May 31, 2019	Jun. 01, 2018	May 31, 2018	May 31, 2017	May 31, 2016
Financial Instruments and Concentrations of Market or Credit Risk
Accounts receivable, net	$ 197.8	$ 170.6	$ 202.0
Allowance for doubtful accounts	16.0		7.5	$ 4.9	$ 3.3
Accounts receivable
Financial Instruments and Concentrations of Market or Credit Risk
Accounts receivable, net	197.8		202.0
Accounts receivable \| U.S. Government
Financial Instruments and Concentrations of Market or Credit Risk
Accounts receivable, net	60.4		45.3
Accounts receivable \| U.S. Government \| Trade receivables
Financial Instruments and Concentrations of Market or Credit Risk
Accounts receivable, net	28.7		31.9
Accounts receivable \| U.S. Government \| Unbilled receivables
Financial Instruments and Concentrations of Market or Credit Risk
Accounts receivable, net	31.7		13.4
Accounts receivable \| All other customers
Financial Instruments and Concentrations of Market or Credit Risk
Accounts receivable, net	137.4		156.7
Accounts receivable \| All other customers \| Trade receivables
Financial Instruments and Concentrations of Market or Credit Risk
Accounts receivable, net	92.5		96.2
Accounts receivable \| All other customers \| Unbilled receivables
Financial Instruments and Concentrations of Market or Credit Risk
Accounts receivable, net	44.9		$ 60.5
Accounts receivable \| Former commercial program customers
Financial Instruments and Concentrations of Market or Credit Risk
Past due accounts receivables	12.4
Allowance for doubtful accounts	$ 8.2