Acquisitions - Additional Information (Details) - USD ($) $ in Thousands					3 Months Ended	12 Months Ended
	Feb. 29, 2020	Oct. 07, 2019	May 01, 2019	Jun. 02, 2017	Feb. 29, 2020	May 31, 2020	May 31, 2018	Dec. 31, 2019	May 31, 2019
Business Acquisition [Line Items]
Goodwill						$ 321,434	$ 345,183		$ 334,607
Samuel Joint Venture | Miscellaneous Income, Net
Business Acquisition [Line Items]
Gain in pre-tax earnings					$ 6,055
Samuel Joint Venture | Joint Venture Transactions
Business Acquisition [Line Items]
Additional ownership interest acquired in joint venture								31.75%
Total ownership percentage						63.00%
Book value of assets contributed for acquiring ownership interest in joint venture								$ 30,061
Noncontrolling interest								$ 11,123
Ownership interest percentage								31.25%
Heidtman Cleveland
Business Acquisition [Line Items]
Cash consideration for acquired entity		$ 29,593
Estimated useful life of intangible asset acquired		10 years
Total consideration for acquired entity	$ 29,593
Goodwill	$ 8,024				$ 8,024
Magna Industries, Inc.
Business Acquisition [Line Items]
Total consideration for acquired entity			$ 13,500
Business acquisition contingent consideration, estimated fair value			2,000
Acquisition related costs			1,150
Business combination , total intangible assets			3,677			$ 3,625
Goodwill			$ 777			725
Payment for contingent consideration						1,150
Amount recognized for post-closing adjustment to net working capital.						$ 310
AMTROL
Business Acquisition [Line Items]
Total consideration for acquired entity				$ 291,921
Acquisition related costs				3,568			1,568
Goodwill				$ 103,437
Net sales							265,198
Operating income							$ 18,899