Accounts Receivable (Details) - USD ($) $ in Millions	Feb. 28, 2021	May 31, 2020
Accounts Receivable
Accounts receivable	$ 186.8	$ 171.9
Past due accounts receivable	6.5
Allowance for doubtful accounts	8.7
U.S. Government Contract
Accounts Receivable
Accounts receivable	57.1	61.3
Unbilled receivables	18.7	27.4
U.S. Government Contract \| Trade receivables
Accounts Receivable
Accounts receivable	38.4	33.9
All other customers
Accounts Receivable
Accounts receivable	129.7	110.6
Unbilled receivables	20.8	28.9
All other customers \| Trade receivables
Accounts Receivable
Accounts receivable	$ 108.9	$ 81.7

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 45
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant