Benefit Plans - Changes in Projected Benefit Obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020		Dec. 31, 2019
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 612	$ 518		$ 214
Interest cost	$ 319	$ 313		233
Weighted average assumptions used to determine projected benefit obligations:
Weighted average assumed discount rate	4.50%	3.50%
Qualified Plan
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation, beginning balance	$ 10,277	$ 8,819
Service cost	573	479
Interest cost	300	294
Actuarial (gain) loss	(371)	985
Benefits paid	(318)	(300)
Projected benefit obligation, ending balance	10,461	10,277		8,819
Accumulated benefit obligation, end of year	$ 9,231	$ 9,044
Weighted average assumptions used to determine projected benefit obligations:
Weighted average assumed discount rate	3.18%	2.94%
Assumed rate of annual compensation increases (1)	4.50%	3.50%	[1]
Nonqualified Plans
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation, beginning balance	$ 661	$ 557
Service cost	39	39
Interest cost	20	19
Actuarial (gain) loss	40	68
Benefits paid	(20)	(22)
Projected benefit obligation, ending balance	740	661		$ 557
Accumulated benefit obligation, end of year	$ 578	$ 503
Weighted average assumptions used to determine projected benefit obligations:
Weighted average assumed discount rate	3.18%	2.94%
Assumed rate of annual compensation increases (1)	4.50%	3.50%	[1]

[1] The 2020 projected benefit obligation assumed a rate for qualified and nonqualified plans of 3.50% in 2021 and 4.50% thereafter.