Other Income, Net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Other Non Operating Income Expense [Line Items]
Net gain from asset sales	$ 27	$ 177
Warrick Rolling Mill
Other Non Operating Income Expense [Line Items]
Net gain from asset sales	$ 27
Gum Springs
Other Non Operating Income Expense [Line Items]
Net gain from asset sales		$ 180