Employee Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ (136)	$ (120)
Contributions - Defined benefit plans	39	32
Contributions - Defined contribution plans	227	153
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	55	87
Interest cost	272	340
Expected return on plan assets	573	607
Amortization of prior service cost (credit)	13	5
Recognized actuarial net loss (gain)	(94)	(53)
Net settlement and curtailment (loss) gain	(1)	(8)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	(138)	(114)
Pension Plan [Member] | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions - Defined contribution plans	48
Other Postretirement Benefits Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	1	1
Interest cost	6	8
Expected return on plan assets	1	1
Amortization of prior service cost (credit)	(1)	(11)
Recognized actuarial net loss (gain)	3	3
Net settlement and curtailment (loss) gain	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 2	$ (6)