Pension and Other Postretirement Benefits - Additional Information (Detail) $ in Millions		3 Months Ended				9 Months Ended
	Apr. 01, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($) Employee	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Company's contribution	$ 500
Minimum required cash contribution to pension plans reminder of 2021		$ 80				$ 80
United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Minimum required cash contribution to pension plans					$ 10	49	$ 49
Non-U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Minimum required cash contribution to pension plans		6			$ 15	26	$ 34
Warrick Rolling Mill [Member] | Held for Sale [Member]
Defined Benefit Plan Disclosure [Line Items]
Sale transaction value of waste processing				$ 670
Assumption of other postretirement benefit liabilities			$ 66
Decrease in other postretirement benefit liabilities after post closing adjustment			6
Number of employees | Employee				1,150
Action# 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Decrease to accrued other postretirement benefits liability						(106)
Curtailment gain						17
Settlement charge						26
Action# 1 [Member] | Warrick Rolling Mill [Member] | Held for Sale [Member]
Defined Benefit Plan Disclosure [Line Items]
Sale transaction value of waste processing				$ 670
Assumption of other postretirement benefit liabilities			66
Decrease in other postretirement benefit liabilities after post closing adjustment			6
Number of employees | Employee				1,150
Decrease to accrued other postretirement benefits liability				$ 40
Remeasurement to accrued other postretirement benefits liability						66
Curtailment gain				17
Settlement charge				$ 26
Action# 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge						39
Increase (decrease) to accrued other pension benefits liability						(90)
Action# 2 [Member] | Warrick Rolling Mill [Member] | Held for Sale [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge			39
Increase (decrease) to accrued other pension benefits liability			$ (90)
Action# 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge		7				7
Increase (decrease) to accrued other pension benefits liability		7				7
Action# 4 [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charge		1				1
Increase (decrease) to accrued other pension benefits liability		$ (38)				$ (38)