Segment Data - Financial Information for Reportable Segments (Detail) - USD ($)		2 Months Ended	12 Months Ended
	May 31, 2021	Feb. 29, 2020	May 31, 2022	May 31, 2021	May 31, 2020
Segment Reporting Information [Line Items]
Net sales			$ 5,242,219,000	$ 3,171,429,000	$ 3,059,119,000
Capital expenditures			94,600,000	82,178,000	95,503,000
Depreciation and amortization			98,827,000	87,654,000	92,678,000
Impairment of long-lived assets		$ 4,679,000
Restructuring and other (income) expense, net	$ 11,034,000		(445,000)	2,752,000
Equity in net income of unconsolidated affiliates			213,641,000	123,325,000	114,848,000
Adjusted earnings (loss) before interest and taxes			514,286,000	917,717,000	110,786,000
Total assets	3,373,245,000		3,643,023,000	3,373,245,000
Steel Processing
Segment Reporting Information [Line Items]
Net sales			3,933,021,000	2,059,397,000	1,859,670,000
Capital expenditures			35,898,000	28,306,000	40,588,000
Depreciation and amortization			55,771,000	40,870,000	40,819,000
Impairment of long-lived assets			3,076,000		1,839,000
Restructuring and other (income) expense, net			(14,480,000)	1,883,000	3,501,000
Miscellaneous income (expense), net			862,000	(371,000)	6,082,000
Equity in net income of unconsolidated affiliates			29,787,000	15,965,000	1,325,000
Adjusted earnings (loss) before interest and taxes			203,272,000	208,175,000	39,695,000
Total assets	1,359,598,000		2,082,522,000	1,359,598,000
Consumer products
Segment Reporting Information [Line Items]
Net sales			636,478,000	523,697,000	449,337,000
Capital expenditures			13,375,000	13,334,000	8,069,000
Depreciation and amortization			10,919,000	10,145,000	9,189,000
Impairment of long-lived assets				506,000
Restructuring and other (income) expense, net				41,000	846,000
Miscellaneous income (expense), net			(76,000)	(512,000)	(25,000)
Equity in net income of unconsolidated affiliates
Adjusted earnings (loss) before interest and taxes			94,302,000	74,936,000	65,408,000
Total assets	541,028,000		681,188,000	541,028,000
Building Products
Segment Reporting Information [Line Items]
Net sales			541,757,000	402,038,000	383,372,000
Capital expenditures			31,064,000	22,705,000	17,931,000
Depreciation and amortization			18,112,000	17,321,000	18,318,000
Impairment of long-lived assets				1,423,000	3,800,000
Restructuring and other (income) expense, net			(35,000)	256,000	651,000
Miscellaneous income (expense), net			240,000	194,000	158,000
Equity in net income of unconsolidated affiliates			176,498,000	103,447,000	118,288,000
Adjusted earnings (loss) before interest and taxes			216,608,000	117,904,000	104,531,000
Total assets	555,561,000		577,026,000	555,561,000
Sustainable Energy Solutions
Segment Reporting Information [Line Items]
Net sales			130,954,000	134,890,000	122,113,000
Capital expenditures			6,445,000	8,652,000	13,794,000
Depreciation and amortization			6,554,000	6,699,000	5,596,000
Impairment of long-lived assets
Restructuring and other (income) expense, net			(143,000)	10,293,000
Miscellaneous income (expense), net			64,000	203,000	109,000
Equity in net income of unconsolidated affiliates
Adjusted earnings (loss) before interest and taxes			(6,236,000)	4,961,000	5,024,000
Total assets	128,438,000		114,084,000	128,438,000
Other
Segment Reporting Information [Line Items]
Net sales			9,000	51,407,000	244,627,000
Capital expenditures			7,818,000	9,181,000	15,121,000
Depreciation and amortization			7,471,000	12,619,000	18,756,000
Impairment of long-lived assets				11,810,000	77,051,000
Restructuring and other (income) expense, net			(2,438,000)	43,624,000	5,050,000
Incremental expenses related to Nikola gains				50,624,000
Miscellaneous income (expense), net			1,624,000	2,649,000	2,775,000
Equity in net income of unconsolidated affiliates			7,356,000	3,913,000	(4,765,000)
Adjusted earnings (loss) before interest and taxes			8,564,000	(10,505,000)	(7,071,000)
Total assets	$ 788,620,000		188,203,000	788,620,000
Consolidated
Segment Reporting Information [Line Items]
Net sales			5,242,219,000	3,171,429,000	3,059,119,000
Capital expenditures			94,600,000	82,178,000	95,503,000
Depreciation and amortization			98,827,000	87,654,000	92,678,000
Impairment of long-lived assets			3,076,000	13,739,000	82,690,000
Restructuring and other (income) expense, net			(17,096,000)	56,097,000	10,048,000
Incremental expenses related to Nikola gains				50,624,000
Miscellaneous income (expense), net			2,714,000	2,163,000	9,099,000
Equity in net income of unconsolidated affiliates			213,641,000	123,325,000	114,848,000
Adjusted earnings (loss) before interest and taxes			$ 516,510,000	$ 395,471,000	$ 207,587,000