Revenue - Schedule of Net Sales Disaggregates by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2024	Jul. 01, 2023	Jun. 29, 2024	Jul. 01, 2023
Revenue from Contract with Customers [Line Items]
Revenues	$ 8,077,172	$ 9,523,256	$ 16,214,255	$ 18,233,236
Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,395,932	2,645,817	5,106,269	4,748,511
Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,361,315	1,599,724	2,696,213	3,197,852
Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	559,007	581,952	1,170,014	1,220,259
Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	541,951	738,279	1,054,487	1,378,407
Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	344,735	436,551	713,459	875,534
Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	462,325	615,814	874,666	1,113,931
Joist [Member]
Revenue from Contract with Customers [Line Items]
Revenues	338,723	638,975	669,324	1,274,791
Deck [Member]
Revenue from Contract with Customers [Line Items]
Revenues	259,437	473,775	528,067	959,218
Building Systems [Member]
Revenue from Contract with Customers [Line Items]
Revenues	360,519	343,138	674,532	625,048
Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	937,037	934,609	1,759,596	1,870,337
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	516,191	514,622	967,628	969,348
Steel Mills [Member]
Revenue from Contract with Customers [Line Items]
Revenues	4,858,205	5,565,772	10,026,983	10,545,029
Steel Mills [Member] | Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,395,932	2,645,817	5,106,269	4,748,511
Steel Mills [Member] | Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,361,315	1,599,724	2,696,213	3,197,852
Steel Mills [Member] | Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	559,007	581,952	1,170,014	1,220,259
Steel Mills [Member] | Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	541,951	738,279	1,054,487	1,378,407
Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,702,776	3,442,862	5,219,644	6,718,859
Steel Products [Member] | Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	344,735	436,551	713,459	875,534
Steel Products [Member] | Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	462,325	615,814	874,666	1,113,931
Steel Products [Member] | Joist [Member]
Revenue from Contract with Customers [Line Items]
Revenues	338,723	638,975	669,324	1,274,791
Steel Products [Member] | Deck [Member]
Revenue from Contract with Customers [Line Items]
Revenues	259,437	473,775	528,067	959,218
Steel Products [Member] | Building Systems [Member]
Revenue from Contract with Customers [Line Items]
Revenues	360,519	343,138	674,532	625,048
Steel Products [Member] | Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	937,037	934,609	1,759,596	1,870,337
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	516,191	514,622	967,628	969,348
Raw Materials [Member] | Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	$ 516,191	$ 514,622	$ 967,628	$ 969,348