Employee Benefit Plans (Schedule of Plan with ABO in Excess of Plan Assets) (Details) - Pension Plan [Member] - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	$ 37,215	$ 37,941
Accumulated benefit obligation	36,150	37,559
Fair value of plan assets	$ 27,854	$ 36,120