Segments - Schedule of Net Sale by Product to External Customers (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 04, 2026	Jul. 05, 2025	Jul. 04, 2026	Jul. 05, 2025
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 10,397	$ 8,456	$ 19,893	$ 16,286
Sheet [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,916	2,476	5,707	4,685
Bar [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,862	1,397	3,551	2,889
Structural [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	847	694	1,700	1,338
Plate [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	856	686	1,559	1,248
Tubular Products [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	599	380	1,127	744
Rebar Fabrication [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	569	487	1,048	895
Joist & Deck [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	483	564	938	1,062
Building Systems [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	352	337	688	615
Other Steel Products [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,102	889	2,090	1,746
Raw Materials [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 811	$ 546	$ 1,485	$ 1,064