Segment Information - Results (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Segment Reporting Information
Total net sales	$ 4,341,615	$ 4,587,057	$ 13,668,252	$ 14,561,893
Operating income (loss)	395,437	733,550	1,705,535	2,632,645
Income (loss) before income taxes	408,025	754,599	1,738,918	2,676,704
Depreciation and amortization	121,052	107,418	353,357	326,082
Capital expenditures	621,355	558,361	1,414,831	1,142,960
Assets	15,659,821		15,659,821		$ 14,908,420
U.S.
Segment Reporting Information
Total net sales	3,989,100	4,116,294	12,510,524	13,098,688
Non-U.S.
Segment Reporting Information
Total net sales	352,515	470,763	1,157,728	1,463,205
Operating Segment | Steel Operations
Segment Reporting Information
Total net sales	3,024,008	3,293,356	9,786,498	10,060,497
Operating income (loss)	301,254	478,740	1,410,805	1,520,367
Income (loss) before income taxes	302,442	481,047	1,416,794	1,525,805
Depreciation and amortization	91,114	81,600	266,118	246,833
Capital expenditures	121,037	111,843	348,532	334,340
Assets	8,722,673		8,722,673
Operating Segment | Steel Operations | Other segments
Segment Reporting Information
Total net sales	106,987	106,175	371,008	335,271
Operating Segment | Steel Operations | U.S.
Segment Reporting Information
Total net sales	2,745,491	2,904,204	8,817,086	8,874,964
Operating Segment | Steel Operations | Non-U.S.
Segment Reporting Information
Total net sales	171,530	282,977	598,404	850,262
Operating Segment | Metals Recycling Operations
Segment Reporting Information
Total net sales	1,092,562	1,052,305	3,358,809	3,382,357
Operating income (loss)	7,709	13,981	54,662	86,674
Income (loss) before income taxes	6,578	15,319	50,649	99,093
Depreciation and amortization	19,216	17,195	57,113	52,321
Capital expenditures	18,601	83,858	66,659	128,814
Assets	1,554,249		1,554,249
Operating Segment | Metals Recycling Operations | Other segments
Segment Reporting Information
Total net sales	526,966	531,559	1,637,308	1,685,770
Operating Segment | Metals Recycling Operations | U.S.
Segment Reporting Information
Total net sales	394,656	334,922	1,178,276	1,086,286
Operating Segment | Metals Recycling Operations | Non-U.S.
Segment Reporting Information
Total net sales	170,940	185,824	543,225	610,301
Operating Segment | Steel Fabrication Operations
Segment Reporting Information
Total net sales	449,803	633,207	1,375,302	2,281,609
Operating income (loss)	165,592	330,020	524,672	1,343,372
Income (loss) before income taxes	165,153	329,554	523,384	1,343,173
Depreciation and amortization	2,829	2,448	8,288	7,201
Capital expenditures	5,379	5,581	18,524	17,215
Assets	718,199		718,199
Operating Segment | Steel Fabrication Operations | Other segments
Segment Reporting Information
Total net sales	2,538	3,023	8,026	3,248
Operating Segment | Steel Fabrication Operations | U.S.
Segment Reporting Information
Total net sales	446,663	630,045	1,365,549	2,278,121
Operating Segment | Steel Fabrication Operations | Non-U.S.
Segment Reporting Information
Total net sales	602	139	1,727	240
Operating Segment | Aluminum Operations
Segment Reporting Information
Total net sales	4,169		6,034
Operating income (loss)	(23,593)	(7,172)	(56,372)	(13,004)
Income (loss) before income taxes	(25,616)	(7,142)	(60,256)	(12,935)
Depreciation and amortization	655	3	1,182	3
Capital expenditures	475,886	342,969	985,484	636,887
Assets	2,358,956		2,358,956
Operating Segment | Aluminum Operations | Other segments
Segment Reporting Information
Total net sales	4,169		6,034
Operating Segment | Other
Segment Reporting Information
Total net sales	411,733	249,118	1,163,985	862,160
Operating income (loss)	(60,154)	(90,441)	(231,961)	(308,077)
Income (loss) before income taxes	(24,653)	(72,224)	(151,269)	(280,602)
Depreciation and amortization	7,238	6,172	20,656	19,724
Capital expenditures	20,518	14,110	38,462	25,704
Assets	3,861,117		3,861,117
Operating Segment | Other | Other segments
Segment Reporting Information
Total net sales		172		441
Operating Segment | Other | U.S.
Segment Reporting Information
Total net sales	402,290	247,123	1,149,613	859,317
Operating Segment | Other | Non-U.S.
Segment Reporting Information
Total net sales	9,443	1,823	14,372	2,402
Eliminations
Segment Reporting Information
Total net sales	(640,660)	(640,929)	(2,022,376)	(2,024,730)
Operating income (loss)	4,629	8,422	3,729	3,313
Income (loss) before income taxes	(15,879)	8,045	(40,384)	2,170
Capital expenditures	(20,066)		(42,830)
Assets	(1,555,373)		(1,555,373)
Eliminations | Other segments
Segment Reporting Information
Total net sales	$ (640,660)	$ (640,929)	$ (2,022,376)	$ (2,024,730)