Operating segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Aug. 31, 2023	Aug. 31, 2022	Aug. 31, 2023	Aug. 31, 2022	Feb. 28, 2023
Operations and assets by segment
Sales	$ 398,542	$ 406,710	$ 789,415	$ 613,844
Cost of sales	301,296	305,155	595,150	452,236
Gross margin	97,246	101,555	194,265	161,608
Selling, general and administrative	36,239	37,414	67,762	69,558
Operating income (loss)	61,007	64,141	126,503	92,050
Interest expense	27,770	28,144	56,476	35,615
Equity in (earnings) loss of unconsolidated subsidiaries	(974)	0	(2,394)	0
Other (income) expense	(88)	55	(50)	28
Income taxes	5,967	10,822	15,617	15,922
Net income from continuing operations	28,332	25,120	56,854	40,485
Income (loss) from continuing operations before income tax	34,299	35,942	72,471	56,407
Assets:	2,214,561		2,214,561		$ 2,221,479
Property, plant and equipment, net	516,499		516,499		498,503
United States
Operations and assets by segment
Sales	388,538	393,835	769,860	588,195
Property, plant and equipment, net	496,972		496,972		478,722
Canada
Operations and assets by segment
Sales	10,004	12,875	19,555	25,649
Property, plant and equipment, net	19,527		19,527		19,781
Corporate
Operations and assets by segment
Sales	0	0	0	0
Cost of sales	0	0	0	0
Gross margin	0	0	0	0
Selling, general and administrative	17,148	17,068	34,791	41,077
Operating income (loss)	(17,148)	(17,068)	(34,791)	(41,077)
Interest expense	27,770	28,144	56,476	35,615
Equity in (earnings) loss of unconsolidated subsidiaries	0		0
Other (income) expense	(88)	55	(50)	28
Income taxes	5,967	10,822	15,617	15,922
Net income from continuing operations	(50,797)	(56,089)	(106,834)	(92,642)
Income (loss) from continuing operations before income tax	(44,830)	(45,267)	(91,217)	(76,720)
Assets:	48,756		48,756		59,572
Metal Coatings | Operating Segments
Operations and assets by segment
Sales	169,837	165,849	338,631	329,293
Cost of sales	119,471	116,437	237,328	230,018
Gross margin	50,366	49,412	101,303	99,275
Selling, general and administrative	5,285	4,416	10,751	9,009
Operating income (loss)	45,081	44,996	90,552	90,266
Assets:	575,330		575,330		588,337
Precoat Metals | Operating Segments
Operations and assets by segment
Sales	228,705	240,861	450,784	284,551
Cost of sales	181,825	188,718	357,822	222,218
Gross margin	46,880	52,143	92,962	62,333
Selling, general and administrative	7,874	15,930	16,266	19,472
Operating income (loss)	39,006	36,213	76,696	42,861
Assets:	1,504,940		1,504,940		1,488,810
Infrastructure Solutions | Operating Segments
Operations and assets by segment
Sales	0	0	0	0
Cost of sales	0	0	0	0
Gross margin	0	0	0	0
Selling, general and administrative	5,932	0	5,954	0
Operating income (loss)	(5,932)	0	(5,954)	0
Interest expense	0	0	0	0
Equity in (earnings) loss of unconsolidated subsidiaries	(974)		(2,394)
Other (income) expense	0	0	0	0
Income (loss) from continuing operations before income tax	(4,958)	$ 0	(3,560)	$ 0
Assets:	$ 85,535		$ 85,535		$ 84,760