Post-Employment Benefits - Benefit Plan Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair value of plan assets
Beginning of period	$ 5,637
End of period	7,116	$ 5,637
Amounts recognized on the consolidated balance sheets
Other long-term liabilities	(2,949)	(1,840)
Defined benefit plans
Projected benefit obligations
Beginning of period	6,618	6,985
Service cost	269	285	$ 236
Interest cost	259	227	204
Employee contributions	2	2
Actuarial (gain) loss	1,703	(614)
Benefits paid	(206)	(191)
Other, primarily foreign currency translation adjustments	1	(76)
End of period	8,646	6,618	6,985
Fair value of plan assets
Beginning of period	5,637	5,399
Actual return on plan assets	946	(384)
Company contributions	727	873
Employee contributions	2	2
Benefits paid	(206)	(191)
Other, primarily foreign currency translation adjustments	10	(62)
End of period	7,116	5,637	5,399
Funded status, end of period	(1,530)	(981)
Amounts recognized on the consolidated balance sheets
Other assets	395	321
Accounts payable and accrued liabilities	(8)	(8)
Other long-term liabilities	(1,917)	(1,294)
Net obligation	(1,530)	(981)
Actuarial loss, net	3,633	2,516
Prior service cost (credit)	10	11
Accumulated other comprehensive loss	3,643	2,527
Other post-employment plans
Projected benefit obligations
Beginning of period	561	813
Service cost	25	26	26
Interest cost	29	25	24
Actuarial (gain) loss	451	(287)
Benefits paid	(17)	(16)
Other, primarily foreign currency translation adjustments	1	0
End of period	1,050	561	$ 813
Fair value of plan assets
Company contributions	17	16
Benefits paid	(17)	(16)
Funded status, end of period	(1,050)	(561)
Amounts recognized on the consolidated balance sheets
Accounts payable and accrued liabilities	(18)	(15)
Other long-term liabilities	(1,032)	(546)
Net obligation	(1,050)	(561)
Actuarial loss, net	469	25
Prior service cost (credit)	(16)	(22)
Accumulated other comprehensive loss	$ 453	$ 3