Revenue - Schedule of Net Sales Disaggregates by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended
	Apr. 04, 2020	Mar. 30, 2019
Revenue from Contract with Customers [Line Items]
Revenues	$ 5,624,337	$ 6,096,624
Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,578,429	1,807,303
Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,062,666	1,115,130
Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	450,499	433,929
Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	427,676	593,040
Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	305,057	329,871
Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	423,316	342,055
Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	998,481	982,596
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	378,213	492,700
Steel Mills [Member]
Revenue from Contract with Customers [Line Items]
Revenues	3,519,270	3,949,402
Steel Mills [Member] | Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,578,429	1,807,303
Steel Mills [Member] | Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,062,666	1,115,130
Steel Mills [Member] | Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	450,499	433,929
Steel Mills [Member] | Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	427,676	593,040
Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,726,854	1,654,522
Steel Products [Member] | Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	305,057	329,871
Steel Products [Member] | Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	423,316	342,055
Steel Products [Member] | Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	998,481	982,596
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	378,213	492,700
Raw Materials [Member] | Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	$ 378,213	$ 492,700