Retirement Plans - Amounts Recognized in Consolidated Balance Sheet (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Funded Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	$ 71	$ 76
Current liabilities	0	0
Noncurrent liabilities	(6)	0
Pension assets / (accrued benefit liability)	65	76
Unrecognized Net Actuarial (Gains) Losses	756	778
Postretirement Medical Plan
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	0	0
Current liabilities	(8)	(9)
Noncurrent liabilities	(67)	(50)
Pension assets / (accrued benefit liability)	(75)	(59)
Unrecognized Net Actuarial (Gains) Losses	(12)	(32)
Unfunded Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Noncurrent assets	0	0
Current liabilities	(32)	(30)
Noncurrent liabilities	(210)	(186)
Pension assets / (accrued benefit liability)	(242)	(216)
Unrecognized Net Actuarial (Gains) Losses	$ 65	$ 47