Goodwill and Other Intangible Assets - Schedule of Change in Net Carrying Amount of Goodwill by Segment (Detail) $ in Thousands	9 Months Ended
	Oct. 02, 2021 USD ($)
Goodwill [Line Items]
Balance, beginning of period	$ 2,229,672
Acquisitions	556,268
Other	(129)
Translation	2,181
Balance, end of period	2,787,992
Steel Mills [Member]
Goodwill [Line Items]
Balance, beginning of period	612,470
Acquisitions	705
Balance, end of period	613,175
Steel Products [Member]
Goodwill [Line Items]
Balance, beginning of period	887,625
Acquisitions	535,099
Other	(129)
Translation	2,181
Balance, end of period	1,424,776
Raw Materials [Member]
Goodwill [Line Items]
Balance, beginning of period	729,577
Acquisitions	20,464
Balance, end of period	$ 750,041