Operating Segments (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Feb. 14, 2024	Feb. 28, 2026	Feb. 28, 2026	Feb. 28, 2025	Feb. 29, 2024	Aug. 31, 2025
Segment Reporting Information [Line Items]
Number of reportable segments not disclosed			Segment Information
Operations and assets by segment
Sales			$ 1,650,080	$ 1,577,744	$ 1,537,589
Cost of sales			1,255,125	1,195,064	1,174,128
Selling, general and administrative			130,338	146,316	141,861
Operating income (loss)			264,617	236,364	221,600
Equity in earnings of unconsolidated subsidiaries			209,733	16,163	15,407
Interest expense, net			(55,650)	(81,282)	(107,065)
Other income			1,615	(562)	161
Income before income taxes			420,315	170,683	130,103
Legal matter	$ 1,000
Income taxes			103,055	41,850	28,496
Net income			317,260	128,833	101,607
Depreciation			90,056	82,205	79,423
Assets:		$ 2,213,474	2,213,474	2,227,101
Legal matter expense		500
Restructuring charges			3,744	0	0
Stock-based compensation			2,200
Distribution on investment in AVAIL joint venture			273,223	12,565	3,113
Payments To Acquire Property, Plant, Equipment And Acquire Businesses, Net Of Cash			80,776	115,883	95,119
Intangible Assets, Net (Excluding Goodwill)		409,738	409,738	421,850
AIS Joint Venture
Operations and assets by segment
Equity in earnings of unconsolidated subsidiaries			209,700
Equity Method Investment, Aggregate Cost						$ (13,600)
Distribution on investment in AVAIL joint venture			204,500
United States
Operations and assets by segment
Sales			1,603,851	1,537,215	1,498,397
Canada
Operations and assets by segment
Sales			46,229	40,529	39,192
Operating Segments
Operations and assets by segment
Sales			1,650,080	1,577,744	1,537,589
Cost of sales			1,255,125	1,195,064	1,174,128
Selling, general and administrative			53,363	63,114	65,408
Operating income (loss)			341,592	319,566	298,053
Equity in earnings of unconsolidated subsidiaries			209,733	16,163	15,407
Income before income taxes			551,325	335,729	313,460
Depreciation			65,782	57,825	54,293
Assets:		2,187,061	2,187,061	2,202,851
Stock-based compensation			2,200
Payments To Acquire Property, Plant, Equipment And Acquire Businesses, Net Of Cash			78,990	114,495	93,293
Reconciliation to consolidated income before income taxes
Operations and assets by segment
Selling, general and administrative			(76,975)	(83,202)	(76,453)
Interest expense, net			(55,650)	(81,282)	(107,065)
Other income			1,615	(562)	161
Depreciation			24,274	24,380	25,130
Assets:		26,413	26,413	24,250
Stock-based compensation			1,800
Payments To Acquire Property, Plant, Equipment And Acquire Businesses, Net Of Cash			1,786	1,388	1,826
Metal Coatings | Operating Segments
Operations and assets by segment
Sales			758,709	665,107	656,189
Cost of sales			531,089	464,260	465,147
Selling, general and administrative			23,982	22,372	26,314
Operating income (loss)			203,638	178,475	164,728
Legal matter					5,500
Depreciation			27,723	26,640	26,353
Assets:		604,107	604,107	555,095
Restructuring charges			3,800
Stock-based compensation			400
Payments To Acquire Property, Plant, Equipment And Acquire Businesses, Net Of Cash			30,937	29,958	25,484
Intangible Assets, Net (Excluding Goodwill)		35,000	35,000	28,500
Precoat Metals | Operating Segments
Operations and assets by segment
Sales			891,371	912,637	881,400
Cost of sales			724,036	730,804	708,981
Selling, general and administrative			29,251	34,005	32,848
Operating income (loss)			138,084	147,828	139,571
Depreciation			38,059	31,185	27,940
Assets:		1,562,994	1,562,994	1,548,377
Payments To Acquire Property, Plant, Equipment And Acquire Businesses, Net Of Cash			48,053	84,537	67,809
Intangible Assets, Net (Excluding Goodwill)		374,800	374,800	393,300
Infrastructure Solutions | Operating Segments
Operations and assets by segment
Sales			0	0	0
Cost of sales			0	0	0
Selling, general and administrative			130	6,737	6,246
Operating income (loss)			(130)	(6,737)	(6,246)
Equity in earnings of unconsolidated subsidiaries			209,733	16,163	15,407
Income before income taxes			209,603	9,426	9,161
Legal matter				6,500	$ 5,800
Assets:		$ 19,960	$ 19,960	$ 99,379