Segment Information - Results (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Segment Reporting Information
Total net sales	$ 4,632,634	$ 5,081,630	$ 9,326,637	$ 9,974,836
Operating income (loss)	559,123	1,063,735	1,310,098	1,899,095
Income (loss) before income taxes	565,112	1,074,316	1,330,893	1,922,105
Depreciation and amortization	117,053	110,970	232,305	218,664
Capital expenditures	419,166	358,280	793,476	584,599
Assets	15,061,257		15,061,257		$ 14,908,420
U.S.
Segment Reporting Information
Total net sales	4,242,936	4,531,374	8,521,424	8,982,394
Non-U.S.
Segment Reporting Information
Total net sales	389,698	550,256	805,213	992,442
Operating Segment | Steel Operations
Segment Reporting Information
Total net sales	3,247,962	3,595,442	6,762,490	6,767,141
Operating income (loss)	438,620	699,719	1,109,551	1,041,627
Income (loss) before income taxes	439,540	701,669	1,114,352	1,044,758
Depreciation and amortization	87,497	80,701	175,004	165,233
Capital expenditures	131,662	101,869	227,495	222,497
Assets	8,870,515		8,870,515
Operating Segment | Steel Operations | Other segments
Segment Reporting Information
Total net sales	115,730	145,887	264,021	229,096
Operating Segment | Steel Operations | U.S.
Segment Reporting Information
Total net sales	2,937,985	3,123,512	6,071,595	5,970,760
Operating Segment | Steel Operations | Non-U.S.
Segment Reporting Information
Total net sales	194,247	326,043	426,874	567,285
Operating Segment | Metals Recycling Operations
Segment Reporting Information
Total net sales	1,172,206	1,168,125	2,266,247	2,330,052
Operating income (loss)	28,225	33,005	46,953	72,693
Income (loss) before income taxes	22,562	38,225	44,071	83,774
Depreciation and amortization	19,427	20,761	37,897	35,126
Capital expenditures	16,194	25,259	48,058	44,956
Assets	1,595,874		1,595,874
Operating Segment | Metals Recycling Operations | Other segments
Segment Reporting Information
Total net sales	585,774	575,752	1,110,342	1,154,211
Operating Segment | Metals Recycling Operations | U.S.
Segment Reporting Information
Total net sales	392,697	368,561	783,620	751,364
Operating Segment | Metals Recycling Operations | Non-U.S.
Segment Reporting Information
Total net sales	193,735	223,812	372,285	424,477
Operating Segment | Steel Fabrication Operations
Segment Reporting Information
Total net sales	473,736	779,598	925,499	1,648,402
Operating income (loss)	180,740	462,080	359,080	1,013,352
Income (loss) before income taxes	179,864	462,207	358,231	1,013,619
Depreciation and amortization	2,777	2,422	5,459	4,753
Capital expenditures	7,709	7,138	13,145	11,634
Assets	791,533		791,533
Operating Segment | Steel Fabrication Operations | Other segments
Segment Reporting Information
Total net sales	904	189	5,488	225
Operating Segment | Steel Fabrication Operations | U.S.
Segment Reporting Information
Total net sales	472,790	779,374	918,886	1,648,076
Operating Segment | Steel Fabrication Operations | Non-U.S.
Segment Reporting Information
Total net sales	42	35	1,125	101
Operating Segment | Aluminum Operations
Segment Reporting Information
Total net sales	1,865		1,865
Operating income (loss)	(19,248)	(3,410)	(32,779)	(5,832)
Income (loss) before income taxes	(20,829)	(3,387)	(34,640)	(5,793)
Depreciation and amortization	507		527
Capital expenditures	272,270	219,098	509,598	293,918
Assets	1,968,632		1,968,632
Operating Segment | Aluminum Operations | Other segments
Segment Reporting Information
Total net sales	1,865		1,865
Operating Segment | Other
Segment Reporting Information
Total net sales	441,138	260,562	752,252	613,042
Operating income (loss)	(73,935)	(120,970)	(171,807)	(217,636)
Income (loss) before income taxes	(37,543)	(117,299)	(126,616)	(208,378)
Depreciation and amortization	6,845	7,086	13,418	13,552
Capital expenditures	14,095	4,916	17,944	11,594
Assets	3,029,749		3,029,749
Operating Segment | Other | Other segments
Segment Reporting Information
Total net sales		269		269
Operating Segment | Other | U.S.
Segment Reporting Information
Total net sales	439,464	259,927	747,323	612,194
Operating Segment | Other | Non-U.S.
Segment Reporting Information
Total net sales	1,674	366	4,929	579
Eliminations
Segment Reporting Information
Total net sales	(704,273)	(722,097)	(1,381,716)	(1,383,801)
Operating income (loss)	4,721	(6,689)	(900)	(5,109)
Income (loss) before income taxes	(18,482)	(7,099)	(24,505)	(5,875)
Capital expenditures	(22,764)		(22,764)
Assets	(1,195,046)		(1,195,046)
Eliminations | Other segments
Segment Reporting Information
Total net sales	$ (704,273)	$ (722,097)	$ (1,381,716)	$ (1,383,801)