Benefit Plans - Changes in Fair Value of Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	$ 14,352
Fair value of plan assets, ending balance	15,824	$ 14,352
Qualified Plan
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	14,635	12,398
Actual return on plan assets	1,679	2,164
Employer contributions	403	373
Benefits paid	(318)	(300)
Fair value of plan assets, ending balance	16,399	14,635
Funded status, end of year	5,938	4,358
Nonqualified Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, beginning balance	0	0
Actual return on plan assets	0	0
Employer contributions	20	22
Benefits paid	(20)	(22)
Fair value of plan assets, ending balance	0	0
Funded status, end of year	$ (740)	$ (661)