Operating segments (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Feb. 29, 2024	Feb. 29, 2024	Feb. 28, 2023	Feb. 28, 2022	Sep. 30, 2022
Operations and assets by segment
Sales	$ 1,537,589	$ 1,537,589	$ 1,323,649	$ 525,598
Cost of sales	1,174,128	1,174,128	1,027,706	379,445
Gross margin	363,461	363,461	295,943	146,153
Selling, general and administrative	141,861	141,861	122,305	66,934
Operating income (loss)	221,600	221,600	173,638	79,219
Interest expense, net of capitalized interest	(107,065)	(107,065)	(88,800)	(6,363)
Equity in earnings of unconsolidated subsidiaries	15,407	15,407	2,597	0
Other (income) expense	161	161	1,240	175
Income (loss) from continuing operations before income tax	130,103	130,103	88,675	73,031
Income taxes	28,496	28,496	22,336	23,214
Net income from continuing operations	101,607	101,607	66,339	49,817
Legal matter expense	500
Amortization of intangible assets		23,961	22,613	6,658
Depreciation		79,423	74,590	32,081
Expenditures for acquisitions, net of cash, and property, plant and equipment:		95,119	1,339,850	84,809
Assets:	2,195,505	2,195,505	2,221,479
Property, plant and equipment, net	$ 541,652	541,652	498,503
Selling, general and administrative
Operations and assets by segment
Amortization of intangible assets		23,961	15,489	0
Cost of sales
Operations and assets by segment
Amortization of intangible assets		$ 0	7,124	6,658
AIS Joint Venture
Operations and assets by segment
Ownership percentage of investment	40.00%	40.00%			40.00%
United States
Operations and assets by segment
Sales		$ 1,498,397	1,279,890	494,012
Property, plant and equipment, net	$ 522,693	522,693	478,722
Canada
Operations and assets by segment
Sales		39,192	43,759	31,586
Property, plant and equipment, net	18,959	18,959	19,781
Corporate
Operations and assets by segment
Sales	0		0	0
Cost of sales	0		0	0
Gross margin	0		0	0
Selling, general and administrative	76,453		61,824	49,539
Operating income (loss)	(76,453)		(61,824)	(49,539)
Interest expense, net of capitalized interest	(107,065)		(88,800)	(6,363)
Equity in earnings of unconsolidated subsidiaries	0		0
Other (income) expense	33		374	60
Income (loss) from continuing operations before income tax	(183,485)		(150,250)	(55,842)
Income taxes	28,496		22,336	23,214
Net income from continuing operations	(211,981)		(172,586)	(79,056)
Depreciation		25,129	1,436	1,628
Expenditures for acquisitions, net of cash, and property, plant and equipment:		1,826	797	2,073
Assets:	43,709	43,709	59,572
Corporate | Selling, general and administrative
Operations and assets by segment
Amortization of intangible assets		24,000
Metal Coatings | Selling, general and administrative
Operations and assets by segment
Legal matter expense		5,500
Amortization of intangible assets			15,500
Metal Coatings | Cost of sales
Operations and assets by segment
Amortization of intangible assets			7,100	6,700
Metal Coatings | Operating Segments
Operations and assets by segment
Sales	656,189		636,982	525,598
Cost of sales	465,147		462,473	379,445
Gross margin	191,042		174,509	146,153
Selling, general and administrative	26,314		18,556	17,395
Operating income (loss)	164,728		155,953	128,758
Interest expense, net of capitalized interest	0		0	0
Equity in earnings of unconsolidated subsidiaries	0		0
Other (income) expense	128		101	115
Income (loss) from continuing operations before income tax	164,856		156,054	128,873
Depreciation		26,353	32,955	30,453
Expenditures for acquisitions, net of cash, and property, plant and equipment:		25,484	23,639	82,736
Assets:	553,505	553,505	588,337
Precoat Metals
Operations and assets by segment
Legal matter expense		5,800
Precoat Metals | Operating Segments
Operations and assets by segment
Sales	881,400		686,667	0
Cost of sales	708,981		565,233	0
Gross margin	172,419		121,434	0
Selling, general and administrative	32,848		41,925	0
Operating income (loss)	139,571		79,509	0
Interest expense, net of capitalized interest	0		0	0
Equity in earnings of unconsolidated subsidiaries	0		0
Other (income) expense	0		765	0
Income (loss) from continuing operations before income tax	139,571		80,274	0
Depreciation		27,941	40,199	0
Expenditures for acquisitions, net of cash, and property, plant and equipment:		67,809	1,315,414	0
Assets:	1,500,122	1,500,122	1,488,810
Infrastructure Solutions | Operating Segments
Operations and assets by segment
Sales	0		0	0
Cost of sales	0		0	0
Gross margin	0		0	0
Selling, general and administrative	6,246		0	0
Operating income (loss)	(6,246)		0	0
Interest expense, net of capitalized interest	0		0	0
Equity in earnings of unconsolidated subsidiaries	15,407		2,597
Other (income) expense	0		0	0
Income (loss) from continuing operations before income tax	9,161		2,597	$ 0
Assets:	$ 98,169	$ 98,169	$ 84,760