Segments - Segments (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jul. 04, 2020	Jun. 29, 2019	Jul. 04, 2020	Jun. 29, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net sales	$ 4,327,306	$ 5,895,986	$ 9,951,643	$ 11,992,610
Earnings (loss) before income taxes and noncontrolling interests	181,057	534,622	327,354	1,224,238
Total assets	18,765,965		18,765,965		$ 18,344,666
Operating Segments [Member] \| Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	2,513,961	3,703,447	6,033,231	7,652,849
Earnings (loss) before income taxes and noncontrolling interests	150,424	578,920	306,930	1,268,318
Total assets	9,011,588		9,011,588		9,283,216
Operating Segments [Member] \| Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	1,523,168	1,750,183	3,250,022	3,404,705
Earnings (loss) before income taxes and noncontrolling interests	152,874	116,084	315,433	193,517
Total assets	4,414,063		4,414,063		4,610,628
Operating Segments [Member] \| Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	290,177	442,356	668,390	935,056
Earnings (loss) before income taxes and noncontrolling interests	(1,389)	21,709	(9,300)	74,932
Total assets	3,125,590		3,125,590		3,316,479
Intercompany Eliminations [Member] \| Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	663,244	814,548	1,532,336	1,716,771
Intercompany Eliminations [Member] \| Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	63,205	54,396	146,574	117,201
Intercompany Eliminations [Member] \| Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	1,484,982	2,430,487	3,908,787	4,854,356
Corporate and Eliminations Items [Member]
Segment Reporting Information [Line Items]
Net sales	(2,211,431)	(3,299,431)	(5,587,697)	(6,688,328)
Earnings (loss) before income taxes and noncontrolling interests	(120,852)	$ (182,091)	(285,709)	$ (312,529)
Total assets	$ 2,214,724		$ 2,214,724		$ 1,134,343

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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