Segment Information - Results (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Segment Reporting Information
Net sales	$ 4,369,195	$ 4,694,003
Costs of goods sold	3,882,651	3,713,205
Other segment items	211,400	229,823
Operating income (loss)	275,144	750,975
Interest expense, net of capitalized interest	12,131	11,978
Other (income) expense, net	(17,641)	(26,784)
Income before income taxes	280,654	765,781
Depreciation and amortization	133,756	115,252
Capital expenditures	305,506	374,310
Total Assets	15,930,428		$ 14,935,233
U.S.
Segment Reporting Information
Net sales	4,041,920	4,278,488
Non-U.S.
Segment Reporting Information
Net sales	327,275	415,515
Operating Segment | Steel Operations
Segment Reporting Information
Net sales	3,154,430	3,514,528
Costs of goods sold	2,870,498	2,790,211
Other segment items	55,070	53,386
Operating income (loss)	228,862	670,931
Depreciation and amortization	98,930	87,507
Capital expenditures	92,007	95,833
Total Assets	8,884,302
Operating Segment | Steel Operations | U.S.
Segment Reporting Information
Net sales	2,904,540	3,133,610
Operating Segment | Steel Operations | Non-U.S.
Segment Reporting Information
Net sales	162,476	232,627
Operating Segment | Steel Operations | Other segments
Segment Reporting Information
Net sales	87,414	148,291
Operating Segment | Metals Recycling Operations
Segment Reporting Information
Net sales	1,072,507	1,041,693
Costs of goods sold	1,020,144	993,262
Other segment items	26,653	35,679
Operating income (loss)	25,710	12,752
Depreciation and amortization	14,970	17,263
Capital expenditures	27,180	30,720
Total Assets	1,484,448
Operating Segment | Metals Recycling Operations | U.S.
Segment Reporting Information
Net sales	371,876	329,844
Operating Segment | Metals Recycling Operations | Non-U.S.
Segment Reporting Information
Net sales	163,019	177,426
Operating Segment | Metals Recycling Operations | Other segments
Segment Reporting Information
Net sales	537,612	534,423
Operating Segment | Steel Fabrication Operations
Segment Reporting Information
Net sales	352,463	451,763
Costs of goods sold	211,828	249,541
Other segment items	23,889	23,882
Operating income (loss)	116,746	178,340
Depreciation and amortization	2,956	2,682
Capital expenditures	5,244	5,436
Total Assets	623,582
Operating Segment | Steel Fabrication Operations | U.S.
Segment Reporting Information
Net sales	351,859	446,096
Operating Segment | Steel Fabrication Operations | Non-U.S.
Segment Reporting Information
Net sales	448	1,083
Operating Segment | Steel Fabrication Operations | Other segments
Segment Reporting Information
Net sales	156	4,584
Operating Segment | Aluminum Operations
Segment Reporting Information
Net sales	100,647	72,156
Costs of goods sold	91,471	64,576
Other segment items	37,911	15,135
Operating income (loss)	(28,735)	(7,555)
Depreciation and amortization	2,647	1,227
Capital expenditures	208,591	238,472
Total Assets	3,106,134
Operating Segment | Aluminum Operations | U.S.
Segment Reporting Information
Net sales	66,576	61,079
Operating Segment | Aluminum Operations | Non-U.S.
Segment Reporting Information
Net sales		1,124
Operating Segment | Aluminum Operations | Other segments
Segment Reporting Information
Net sales	34,071	9,953
Operating Segment | Other
Segment Reporting Information
Net sales	348,401	311,114
Costs of goods sold	346,588	306,920
Other segment items	68,246	102,066
Operating income (loss)	(66,433)	(97,872)
Depreciation and amortization	14,253	6,573
Capital expenditures	5,495	3,849
Total Assets	4,165,063
Operating Segment | Other | U.S.
Segment Reporting Information
Net sales	347,069	307,859
Operating Segment | Other | Non-U.S.
Segment Reporting Information
Net sales	1,332	3,255
Eliminations
Segment Reporting Information
Net sales	(659,253)	(697,251)
Costs of goods sold	(657,878)	(691,305)
Other segment items	(369)	(325)
Operating income (loss)	(1,006)	(5,621)
Capital expenditures	(33,011)
Total Assets	(2,333,101)
Eliminations | Other segments
Segment Reporting Information
Net sales	$ (659,253)	$ (697,251)