Leases - Supplemental cash flow information (Details) - USD ($) $ in Millions	12 Months Ended
May 31, 2023	May 31, 2022	May 31, 2021
Leases
Cash paid for amounts included in the measurement of lease liabilities	$ 14.5	$ 14.1	$ 15.3
Operating lease liabilities arising from obtaining ROU assets	$ 4.5	$ 9.5	$ 5.2

Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 5
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=123391704&loc=SL77918643-209977

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (g)(1)
-URI https://asc.fasb.org/extlink&oid=128292326&loc=SL77918686-209980

Name:	us-gaap_OperatingLeasePayments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration