Segments - Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 03, 2021	Jul. 04, 2020	Jul. 03, 2021	Jul. 04, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net sales	$ 8,789,164	$ 4,327,306	$ 15,806,304	$ 9,951,643
Earnings (loss) before income taxes and noncontrolling interests	2,025,748	181,057	3,323,994	327,354
Total assets	22,995,582		22,995,582		$ 20,125,394
Operating Segments [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	5,909,909	2,513,961	10,518,686	6,033,231
Earnings (loss) before income taxes and noncontrolling interests	2,174,807	150,424	3,489,781	306,930
Total assets	11,734,231		11,734,231		9,708,260
Operating Segments [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	2,241,107	1,523,168	4,051,162	3,250,022
Earnings (loss) before income taxes and noncontrolling interests	259,330	152,874	471,142	315,433
Total assets	5,342,505		5,342,505		4,461,042
Operating Segments [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	638,148	290,177	1,236,456	668,390
Earnings (loss) before income taxes and noncontrolling interests	120,143	(1,389)	343,378	(9,300)
Total assets	3,876,540		3,876,540		3,324,489
Intercompany Eliminations [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	1,496,298	663,244	2,721,411	1,532,336
Intercompany Eliminations [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	80,394	63,205	151,613	146,574
Intercompany Eliminations [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	4,009,808	1,484,982	7,656,003	3,908,787
Corporate and Eliminations Items [Member]
Segment Reporting Information [Line Items]
Net sales	(5,586,500)	(2,211,431)	(10,529,027)	(5,587,697)
Earnings (loss) before income taxes and noncontrolling interests	(528,532)	$ (120,852)	(980,307)	$ (285,709)
Total assets	$ 2,042,306		$ 2,042,306		$ 2,631,603