Revenue - Schedule of Net Sales Disaggregates by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 03, 2021	Jul. 04, 2020	Jul. 03, 2021	Jul. 04, 2020
Revenue from Contract with Customers [Line Items]
Revenues	$ 8,789,164	$ 4,327,306	$ 15,806,304	$ 9,951,643
Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	3,104,304	1,065,004	5,455,759	2,643,433
Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,515,115	811,054	2,776,157	1,873,720
Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	619,541	347,258	1,096,736	797,757
Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	670,949	290,645	1,190,034	718,321
Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	512,503	250,311	887,156	555,368
Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	480,727	413,916	867,284	837,232
Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,247,877	858,941	2,296,722	1,857,422
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	638,148	290,177	1,236,456	668,390
Steel Mills [Member]
Revenue from Contract with Customers [Line Items]
Revenues	5,909,909	2,513,961	10,518,686	6,033,231
Steel Mills [Member] | Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	3,104,304	1,065,004	5,455,759	2,643,433
Steel Mills [Member] | Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,515,115	811,054	2,776,157	1,873,720
Steel Mills [Member] | Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	619,541	347,258	1,096,736	797,757
Steel Mills [Member] | Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	670,949	290,645	1,190,034	718,321
Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,241,107	1,523,168	4,051,162	3,250,022
Steel Products [Member] | Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	512,503	250,311	887,156	555,368
Steel Products [Member] | Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	480,727	413,916	867,284	837,232
Steel Products [Member] | Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,247,877	858,941	2,296,722	1,857,422
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	638,148	290,177	1,236,456	668,390
Raw Materials [Member] | Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	$ 638,148	$ 290,177	$ 1,236,456	$ 668,390