Goodwill and Other Intangible Assets - Schedule of Change in Net Carrying Amount of Goodwill by Segment (Detail) $ in Thousands	9 Months Ended
	Sep. 28, 2019 USD ($)
Goodwill [Line Items]
Balance, beginning of period	$ 2,184,336
Translation	2,163
Balance, end of period	2,186,499
Steel Mills [Member]
Goodwill [Line Items]
Balance, beginning of period	591,986
Translation	0
Balance, end of period	591,986
Steel Products [Member]
Goodwill [Line Items]
Balance, beginning of period	862,773
Translation	2,163
Balance, end of period	864,936
Raw Materials [Member]
Goodwill [Line Items]
Balance, beginning of period	729,577
Translation	0
Balance, end of period	$ 729,577