Revenue - Schedule of Net Sales Disaggregates by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2024	Sep. 30, 2023	Sep. 28, 2024	Sep. 30, 2023
Revenue from Contract with Customers [Line Items]
Revenues	$ 7,444,160	$ 8,775,734	$ 23,658,415	$ 27,008,970
Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,196,380	2,351,705	7,302,649	7,100,216
Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,263,897	1,448,433	3,960,110	4,646,285
Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	534,931	626,633	1,704,945	1,846,892
Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	464,301	664,708	1,518,788	2,043,115
Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	291,425	370,472	1,004,884	1,246,006
Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	487,093	604,684	1,361,759	1,718,615
Joist [Member]
Revenue from Contract with Customers [Line Items]
Revenues	274,903	528,018	944,227	1,802,809
Deck [Member]
Revenue from Contract with Customers [Line Items]
Revenues	242,356	411,352	770,423	1,370,570
Building Systems [Member]
Revenue from Contract with Customers [Line Items]
Revenues	341,965	392,658	1,016,497	1,017,706
Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	858,418	928,785	2,618,014	2,799,122
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	488,491	448,286	1,456,119	1,417,634
Steel Mills [Member]
Revenue from Contract with Customers [Line Items]
Revenues	4,459,509	5,091,479	14,486,492	15,636,508
Steel Mills [Member] | Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,196,380	2,351,705	7,302,649	7,100,216
Steel Mills [Member] | Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,263,897	1,448,433	3,960,110	4,646,285
Steel Mills [Member] | Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	534,931	626,633	1,704,945	1,846,892
Steel Mills [Member] | Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	464,301	664,708	1,518,788	2,043,115
Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,496,160	3,235,969	7,715,804	9,954,828
Steel Products [Member] | Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	291,425	370,472	1,004,884	1,246,006
Steel Products [Member] | Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	487,093	604,684	1,361,759	1,718,615
Steel Products [Member] | Joist [Member]
Revenue from Contract with Customers [Line Items]
Revenues	274,903	528,018	944,227	1,802,809
Steel Products [Member] | Deck [Member]
Revenue from Contract with Customers [Line Items]
Revenues	242,356	411,352	770,423	1,370,570
Steel Products [Member] | Building Systems [Member]
Revenue from Contract with Customers [Line Items]
Revenues	341,965	392,658	1,016,497	1,017,706
Steel Products [Member] | Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	858,418	928,785	2,618,014	2,799,122
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	488,491	448,286	1,456,119	1,417,634
Raw Materials [Member] | Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	$ 488,491	$ 448,286	$ 1,456,119	$ 1,417,634