Revenue - Schedule of Net Sales Disaggregates by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended
	Apr. 03, 2021	Apr. 04, 2020
Revenue from Contract with Customers [Line Items]
Revenues	$ 7,017,140	$ 5,624,337
Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,351,455	1,578,429
Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,261,042	1,062,666
Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	477,195	450,499
Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	519,085	427,676
Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	374,653	305,057
Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	386,557	423,316
Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,048,845	998,481
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	598,308	378,213
Steel Mills [Member]
Revenue from Contract with Customers [Line Items]
Revenues	4,608,777	3,519,270
Steel Mills [Member] | Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,351,455	1,578,429
Steel Mills [Member] | Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,261,042	1,062,666
Steel Mills [Member] | Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	477,195	450,499
Steel Mills [Member] | Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	519,085	427,676
Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,810,055	1,726,854
Steel Products [Member] | Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	374,653	305,057
Steel Products [Member] | Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	386,557	423,316
Steel Products [Member] | Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,048,845	998,481
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	598,308	378,213
Raw Materials [Member] | Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	$ 598,308	$ 378,213