v3.20.4
Pension And Postretirement Benefits (Narrative) (Details) - USD ($)
1 Months Ended 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]            
Combined net pension and postretirement cost       $ 711,000,000 $ 2,762,000,000 $ (4,251,000,000)
Increase (decrease) in plan benefit obligations due to change in assumed rates       $ (2,992,000,000) $ (2,002,000,000) (1,148,000,000)
Composite rate of compensation increase for determining benefit obligation 3.00% 3.00%   3.00% 3.00%  
Discretionary contributions to postretirement plan $ 425,000,000 $ 200,000,000        
Debt-financed shares held by ESOPs (allocated or unallocated) 0     $ 0    
Benefit cost of the contributory savings plans       814,000,000 $ 793,000,000 724,000,000
Forecast            
Defined Benefit Plan Disclosure [Line Items]            
Increase (decrease) in plan benefit obligations due to change in assumed rates     $ 277,000,000      
Assumptions used, percentage change in weighted-average interest crediting rate that would impact pension benefit obligation     (0.50%)      
Pension Benefits            
Defined Benefit Plan Disclosure [Line Items]            
Special termination benefits       0 81,000,000  
Accumulated benefit obligation for pension plans $ 60,848,000,000 $ 58,150,000,000   60,848,000,000 58,150,000,000  
Combined net pension and postretirement cost       $ 1,450,000,000 $ 2,393,000,000 $ (909,000,000)
Discount rate for determining projected benefit obligation 2.70% 3.40%   2.70% 3.40% 4.50%
Decrease in discount rate over prior year       0.70% 1.10%  
Increase (decrease) in plan benefit obligations due to change in assumed rates       $ 5,594,000,000 $ 8,018,000,000  
Long-term rate of return on plan assets       7.00% 7.00% 7.00%
Composite rate of compensation increase for determining benefit obligation 3.00% 3.00%   3.00% 3.00% 3.00%
Preferred equity interest value $ 54,606,000,000 $ 53,530,000,000   $ 54,606,000,000 $ 53,530,000,000 $ 51,681,000,000
Aggregate percentage of the fair value of investments to the fair value of total plan assets held as of the measurement date 11.00%     11.00%    
Pension Benefits | Level 3            
Defined Benefit Plan Disclosure [Line Items]            
Preferred equity interest value $ 8,390,000,000 11,639,000,000   $ 8,390,000,000 11,639,000,000 11,333,000,000
Pension Benefits | Preferred interest            
Defined Benefit Plan Disclosure [Line Items]            
Preferred equity interest value 5,771,000,000 8,806,000,000   5,771,000,000 8,806,000,000  
Pension Benefits | Preferred interest | Level 3            
Defined Benefit Plan Disclosure [Line Items]            
Preferred equity interest value $ 5,771,000,000 8,806,000,000   5,771,000,000 8,806,000,000  
Pension Benefits | Mobility II, LLC | Preferred interest            
Defined Benefit Plan Disclosure [Line Items]            
Preferred equity interest value held by pension trust   $ 8,806,000,000     8,806,000,000  
Value of portion of preferred interest sold to third party investors       2,885,000,000    
Pension Benefits | Forecast            
Defined Benefit Plan Disclosure [Line Items]            
Long-term rate of return on plan assets     6.75%      
Downward adjustment to expected long-term rate of return on plan assets     0.25%      
Postretirement Benefits            
Defined Benefit Plan Disclosure [Line Items]            
Special termination benefits       0 0  
Combined net pension and postretirement cost       $ (739,000,000) $ 369,000,000 $ (3,342,000,000)
Discount rate for determining projected benefit obligation 2.40% 3.20%   2.40% 3.20% 4.40%
Decrease in discount rate over prior year       0.80% 1.20%  
Increase (decrease) in plan benefit obligations due to change in assumed rates       $ 1,311,000,000 $ 2,399,000,000  
Long-term rate of return on plan assets       4.75% 5.75% 5.75%
Composite rate of compensation increase for determining benefit obligation 3.00% 3.00%   3.00% 3.00% 3.00%
Preferred equity interest value $ 3,843,000,000 $ 4,145,000,000   $ 3,843,000,000 $ 4,145,000,000 $ 4,277,000,000
Aggregate percentage of the fair value of investments to the fair value of total plan assets held as of the measurement date 1.00%     1.00%    
Postretirement Benefits | Level 3            
Defined Benefit Plan Disclosure [Line Items]            
Preferred equity interest value $ 4,000,000 $ 32,000,000   $ 4,000,000 32,000,000 13,000,000
Postretirement Benefits | Forecast            
Defined Benefit Plan Disclosure [Line Items]            
Long-term rate of return on plan assets     4.50%      
Downward adjustment to expected long-term rate of return on plan assets     0.25%      
Healthcare Benefits | Prescription Drug Cost - Eligible Participants            
Defined Benefit Plan Disclosure [Line Items]            
Increase (decrease) in plan benefit obligations due to change in assumed rates         $ (102,000,000)  
Assumed annual and ultimate health care cost trend rate for next fiscal year 4.00%     4.00%    
Estimated annual growth rate for health care cost 4.00% 4.50%   4.00% 4.50%  
Healthcare Benefits | Medical Cost - Eligible Participants            
Defined Benefit Plan Disclosure [Line Items]            
Increase (decrease) in plan benefit obligations due to change in assumed rates         $ (102,000,000)  
Assumed annual and ultimate health care cost trend rate for next fiscal year 4.00%     4.00%    
Estimated annual growth rate for health care cost 4.00% 4.50%   4.00% 4.50%  
Healthcare Benefits | Administrative Expense            
Defined Benefit Plan Disclosure [Line Items]            
Percent of growth assumed       2.50%    
Healthcare Benefits | Administrative Expense | Forecast            
Defined Benefit Plan Disclosure [Line Items]            
Percent of growth assumed     2.50%      
Healthcare Benefits | Dental Claims            
Defined Benefit Plan Disclosure [Line Items]            
Percent of growth assumed       3.00%    
Healthcare Benefits | Dental Claims | Forecast            
Defined Benefit Plan Disclosure [Line Items]            
Percent of growth assumed     3.00%      
Supplemental Employee Retirement Plan            
Defined Benefit Plan Disclosure [Line Items]            
Combined net pension and postretirement cost       $ 330,000,000 $ 438,000,000  
Discount rate for determining projected benefit obligation 2.30% 3.20%   2.30% 3.20%  
Projected benefit obligation $ 2,687,000,000 $ 2,605,000,000   $ 2,687,000,000 $ 2,605,000,000  
Deferred compensation expense       $ 183,000,000 $ 199,000,000 $ 128,000,000