Acquisitions - Additional Information (Details) $ in Millions				3 Months Ended	12 Months Ended
	Nov. 16, 2023 USD ($)	Dec. 01, 2021 USD ($)	Jun. 08, 2021 USD ($)	Feb. 28, 2022 USD ($)	May 31, 2024 USD ($)	May 31, 2023 USD ($) Acquisition	May 31, 2022 USD ($)
Business Acquisition [Line Items]
Goodwill					$ 79.6	$ 78.6	$ 80.0
Pension liability adjustment					(2.4)	$ 0.7	(6.6)
Number of acquisitions | Acquisition						0
Cash consideration for acquired entity, net of cash acquired					21.0	$ 0.0	376.7
Net sales					3,430.6	3,607.7	4,068.9
Operating income (loss)					194.5	120.3	226.6
Incremental cost of goods sold					$ 2,990.8	$ 3,271.2	$ 3,673.4
TWB | Joint Venture Transactions
Business Acquisition [Line Items]
Percent of ownership interest held in unconsolidated affiliates			55.00%		55.00%
Voestalpine Automotive Components Nagold GmbH & Co. KG
Business Acquisition [Line Items]
Date of acquisition	Nov. 16, 2023
Business acquisition, name of acquired entity	Voestalpine Nagold
Net cash consideration	$ 21.0
Pension liability	0.9
Property, plant and equipment	12.3
Net working capital	9.0
Goodwill	0.6
Purchase accounting adjustments, property, plant and equipment	0.3
Purchase accounting adjustments, net working capital	(0.8)
Purchase accounting adjustments, goodwill	0.5
Pension liability adjustment	0.0
Voestalpine Automotive Components Nagold GmbH & Co. KG | Property, Plant and Equipment
Business Acquisition [Line Items]
Purchase consideration, net	12.6
Voestalpine Automotive Components Nagold GmbH & Co. KG | Net Working Capital
Business Acquisition [Line Items]
Purchase consideration, net	8.2
Voestalpine Automotive Components Nagold GmbH & Co. KG | Goodwill
Business Acquisition [Line Items]
Purchase consideration, net	$ 1.1
Shiloh Industries' U.S. BlankLight
Business Acquisition [Line Items]
Net cash consideration			$ 104.5
Tempel Steel Company
Business Acquisition [Line Items]
Cash consideration for acquired entity, net of cash acquired		$ 272.2
Acquisition related costs		$ 1.9		$ 1.9
Net sales				278.2
Operating income (loss)				8.6
Incremental cost of goods sold				$ 3.8