The total amount due to the entity within one year of the balance sheet date (or one operating cycle, if longer) from outside sources, including trade accounts receivable, notes and loans receivable, as well as any other types of receivables, net of allowances established for the purpose of reducing such receivables to an amount that approximates their net realizable value.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(5))
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section S99
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-Subparagraph (SX 210.6-06(3))
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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Name:	us-gaap_ReceivablesNetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Summary of Significant Accounting Policies - Financial Instruments (Details) - USD ($) $ in Millions	May 31, 2021	May 31, 2020	May 31, 2019	May 31, 2018
Accounts receivable, net	$ 166.7	$ 171.9
Allowance for doubtful accounts	16.4	22.1	$ 16.0	$ 7.5
U.S. Government
Accounts receivable, net	49.3	61.3
U.S. Government \| Trade receivables
Accounts receivable	24.1	33.9
U.S. Government \| Unbilled receivables
Unbilled receivables	25.2	27.4
All other customers
Accounts receivable, net	117.4	110.6
All other customers \| Trade receivables
Accounts receivable	104.9	81.7
All other customers \| Unbilled receivables
Unbilled receivables	12.5	$ 28.9
Accounts receivable \| Former commercial program customers
Past due accounts receivable	4.7
Allowance for doubtful accounts	$ 8.8