Segments - Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Apr. 03, 2021	Apr. 04, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net sales	$ 7,017,140	$ 5,624,337
Earnings (loss) before income taxes and noncontrolling interests	1,298,246	146,297
Total assets	21,172,408		$ 20,125,394
Operating Segments [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	4,608,777	3,519,270
Earnings (loss) before income taxes and noncontrolling interests	1,314,974	156,506
Total assets	10,785,872		9,708,260
Operating Segments [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	1,810,055	1,726,854
Earnings (loss) before income taxes and noncontrolling interests	211,812	162,559
Total assets	4,838,456		4,461,042
Operating Segments [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	598,308	378,213
Earnings (loss) before income taxes and noncontrolling interests	223,235	(7,911)
Total assets	3,605,884		3,324,489
Intercompany Eliminations [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	1,225,113	869,092
Intercompany Eliminations [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	71,219	83,369
Intercompany Eliminations [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	3,646,195	2,423,805
Corporate and Eliminations Items [Member]
Segment Reporting Information [Line Items]
Net sales	(4,942,527)	(3,376,266)
Earnings (loss) before income taxes and noncontrolling interests	(451,775)	$ (164,857)
Total assets	$ 1,942,196		$ 2,631,603