Retirement Plans - Change in Benefit Obligation, Fair Value of Plan Assets, and Funded Status of Pension Plans and Postretirement Medical Plan (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in Fair Value of Plan Assets
Beginning balance	$ 2,732
Ending balance	2,568	$ 2,732
Funded Pension Plans
Change in Benefit Obligation
Beginning balance	2,765	2,560
Service cost	30	36
Interest cost	84	93
Actuarial (gains) loss	(237)	138
Benefit payments	(110)	(113)
Plan curtailments	(10)	(3)
Plan amendments	4	0
Foreign currency exchange rate changes	(34)	54
Ending balance	2,492	2,765	$ 2,560
Change in Fair Value of Plan Assets
Beginning balance	2,732	2,284
Actual return on plan assets	(77)	351
Employer contributions	59	158
Benefit payments	(110)	(113)
Foreign currency exchange rate changes	(36)	52
Ending balance	2,568	2,732	2,284
Funded Status (Plan assets greater (less) than benefit obligations) at December 31,	76	(33)
Unrecognized Net Actuarial (Gains) Losses	778	789
Postretirement Medical Plan
Change in Benefit Obligation
Beginning balance	87	84
Service cost	2	4	4
Interest cost	3	3	3
Actuarial (gains) loss	(24)	3
Benefit payments	(7)	(7)
Plan curtailments	(2)	0
Plan amendments	0	0
Foreign currency exchange rate changes	0	0
Ending balance	59	87	84
Change in Fair Value of Plan Assets
Beginning balance	0	0
Actual return on plan assets	0	0
Employer contributions	7	7
Benefit payments	(7)	(7)
Foreign currency exchange rate changes	0	0
Ending balance	0	0	0
Funded Status (Plan assets greater (less) than benefit obligations) at December 31,	(59)	(87)
Unrecognized Net Actuarial (Gains) Losses	(32)	(10)
Unfunded Pension Plan
Change in Benefit Obligation
Beginning balance	249	256
Service cost	12	13
Interest cost	7	9
Actuarial (gains) loss	(29)	10
Benefit payments	(19)	(39)
Plan curtailments	(4)	0
Plan amendments	0	0
Foreign currency exchange rate changes	0	0
Ending balance	216	249	256
Change in Fair Value of Plan Assets
Beginning balance	0	0
Actual return on plan assets	0	0
Employer contributions	19	39
Benefit payments	(19)	(39)
Foreign currency exchange rate changes	0	0
Ending balance	0	0	$ 0
Funded Status (Plan assets greater (less) than benefit obligations) at December 31,	(216)	(249)
Unrecognized Net Actuarial (Gains) Losses	$ 47	$ 84