Revenue - Schedule of Net Sales Disaggregates by Major Source (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 02, 2021	Oct. 03, 2020	Oct. 02, 2021	Oct. 03, 2020
Revenue from Contract with Customers [Line Items]
Revenues	$ 10,313,223	$ 4,927,960	$ 26,119,527	$ 14,879,603
Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	3,643,599	1,256,537	9,099,358	3,899,970
Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,633,641	957,216	4,409,798	2,830,936
Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	765,440	362,192	1,862,176	1,159,949
Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	819,453	266,680	2,009,487	985,001
Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	678,178	274,915	1,565,334	830,283
Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	475,861	463,286	1,343,145	1,300,518
Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,590,240	999,803	3,886,962	2,857,225
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	706,811	347,331	1,943,267	1,015,721
Steel Mills [Member]
Revenue from Contract with Customers [Line Items]
Revenues	6,862,133	2,842,625	17,380,819	8,875,856
Steel Mills [Member] | Sheet [Member]
Revenue from Contract with Customers [Line Items]
Revenues	3,643,599	1,256,537	9,099,358	3,899,970
Steel Mills [Member] | Bar [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,633,641	957,216	4,409,798	2,830,936
Steel Mills [Member] | Structural [Member]
Revenue from Contract with Customers [Line Items]
Revenues	765,440	362,192	1,862,176	1,159,949
Steel Mills [Member] | Plate [Member]
Revenue from Contract with Customers [Line Items]
Revenues	819,453	266,680	2,009,487	985,001
Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	2,744,279	1,738,004	6,795,441	4,988,026
Steel Products [Member] | Tubular Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	678,178	274,915	1,565,334	830,283
Steel Products [Member] | Rebar Fabrication [Member]
Revenue from Contract with Customers [Line Items]
Revenues	475,861	463,286	1,343,145	1,300,518
Steel Products [Member] | Other Steel Products [Member]
Revenue from Contract with Customers [Line Items]
Revenues	1,590,240	999,803	3,886,962	2,857,225
Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	706,811	347,331	1,943,267	1,015,721
Raw Materials [Member] | Raw Materials [Member]
Revenue from Contract with Customers [Line Items]
Revenues	$ 706,811	$ 347,331	$ 1,943,267	$ 1,015,721