Segments - Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Apr. 04, 2020	Mar. 30, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net sales	$ 5,624,337	$ 6,096,624
Earnings (loss) before income taxes and noncontrolling interests	146,297	689,616
Total assets	17,866,061		$ 18,344,666
Operating Segments [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	3,519,270	3,949,402
Earnings (loss) before income taxes and noncontrolling interests	156,506	689,398
Total assets	9,405,870		9,283,216
Operating Segments [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	1,726,854	1,654,522
Earnings (loss) before income taxes and noncontrolling interests	162,559	77,433
Total assets	4,523,621		4,610,628
Operating Segments [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	378,213	492,700
Earnings (loss) before income taxes and noncontrolling interests	(7,911)	53,223
Total assets	3,311,176		3,316,479
Intercompany Eliminations [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	869,092	902,224
Intercompany Eliminations [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	83,369	62,805
Intercompany Eliminations [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	2,423,805	2,423,869
Corporate and Eliminations Items [Member]
Segment Reporting Information [Line Items]
Net sales	(3,376,266)	(3,388,898)
Earnings (loss) before income taxes and noncontrolling interests	(164,857)	$ (130,438)
Total assets	$ 625,394		$ 1,134,343