Employee Benefit Plans - Net Periodic (Benefit) Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Defined Benefit Plan Disclosure
Service cost	$ 0	$ 0	$ 0
Interest cost	582	700	833
Expected return on plan assets	(1,522)	(1,373)	(1,186)
Amortization of prior service credit	0	0	0
Recognized net actuarial loss	354	300	291
Settlements	2	38	5
Special termination benefits	0	0	0
Net periodic (benefit) cost	(584)	(335)	(57)
Other Postretirement and Postemployment Benefits
Defined Benefit Plan Disclosure
Service cost	86	96	83
Interest cost	117	120	137
Expected return on plan assets	(34)	(44)	(47)
Amortization of prior service credit	(6)	(9)	(9)
Recognized net actuarial loss	55	44	37
Settlements	0	0	0
Special termination benefits	0	1,260	0
Net periodic (benefit) cost	$ 218	$ 1,467	$ 201