Employee Benefit Plans - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 51	$ 60
Interest cost	47	46
Expected return on plan assets	(78)	(71)
Amortization of unrecognized (gain) loss	30	43
Amortization of prior service credit	0	0
Special termination benefits	0	0
Other	1	0
Total	51	78
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	2	2
Interest cost	7	6
Expected return on plan assets	0	0
Amortization of unrecognized (gain) loss	(3)	(7)
Amortization of prior service credit	(28)	(31)
Special termination benefits	0	46
Other	0	0
Total	$ (22)	$ 16