Retirement Plans - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Information on postretirement medical plan			Additionally, we maintain an unfunded postretirement medical plan that provides health benefits to certain qualified retirees from ages 55 through 65.
Curtailment gains included in accumulated other comprehensive income (loss)	$ 14
Budgeted contributions to funded pension plans for next year			$ 40
Expense for defined contribution plans			$ 19	$ 22	$ 25
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Current target allocations for plan assets			50.00%
Fixed Income Securities
Defined Benefit Plan Disclosure [Line Items]
Current target allocations for plan assets			30.00%
Other Types of Investments
Defined Benefit Plan Disclosure [Line Items]
Current target allocations for plan assets			20.00%
Postretirement Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain			$ 2	0	0
Service costs			2	4	4
Interest costs			3	3	3
Amortization of unrecognized net actuarial losses			(2)	0	0
Expected return on plan assets			$ 0	$ 0	$ 0
United States
Defined Benefit Plan Disclosure [Line Items]
Decrease in post retirement liabilities	$ (125)
Scenario Forecast
Defined Benefit Plan Disclosure [Line Items]
Service costs		$ 40
Net non-service pension costs		40
Interest costs		95
Amortization of unrecognized net actuarial losses		45
Expected return on plan assets		$ 180