Employee Benefits - Costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Pension Benefits
Net Periodic Benefit Cost
Net Periodic Other Benefit Costs	$ 242	$ 216
Pension Benefits | United States
Net Periodic Benefit Cost
Service cost	124	101
Interest cost	88	99
Expected return on plan assets	(162)	(141)
Amortization of prior service costs (credits)	1	0
Amortization of actuarial losses (gains)	96	60
Settlement losses	60	60
Net Periodic Other Benefit Costs	207	179
Pension Benefits | International
Net Periodic Benefit Cost
Service cost	32	35
Interest cost	43	51
Expected return on plan assets	(52)	(58)
Amortization of prior service costs (credits)	2	3
Amortization of actuarial losses (gains)	10	5
Settlement losses	0	1
Net Periodic Other Benefit Costs	35	37
Other Benefits
Net Periodic Benefit Cost
Service cost	9	9
Interest cost	18	24
Amortization of prior service costs (credits)	(6)	(7)
Amortization of actuarial losses (gains)	0	(1)
Net Periodic Other Benefit Costs	$ 21	$ 25