Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plans - Level 3 Fair Value Measurements (Details)

v3.20.4
Employee Benefit Plans - Level 3 Fair Value Measurements (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Change in fair value of plan assets      
Fair value, January 1 $ 25,836    
Fair value, December 31 27,786 $ 25,836  
U.S. government and agency securities      
Change in fair value of plan assets      
Fair value, January 1 5,301    
Fair value, December 31 5,835 5,301  
Real estate commingled/mutual funds      
Change in fair value of plan assets      
Fair value, January 1 945    
Fair value, December 31 963 945  
Limited partnerships      
Change in fair value of plan assets      
Fair value, January 1 263    
Fair value, December 31 267 263  
Other investments      
Change in fair value of plan assets      
Fair value, January 1 1,037    
Fair value, December 31 1,097 1,037  
Level 3      
Change in fair value of plan assets      
Fair value, January 1 1,661 1,569 $ 1,092
Actual Return on Plan Assets Still Held at the Reporting Date 4 39 33
Purchases, Sales and Settlements 59 53 444
Fair value, December 31 1,724 1,661 1,569
Level 3 | U.S. government and agency securities      
Change in fair value of plan assets      
Fair value, January 1 8 9 9
Actual Return on Plan Assets Still Held at the Reporting Date 0 0 0
Purchases, Sales and Settlements (1) (1) 0
Fair value, December 31 7 8 9
Level 3 | Private real estate      
Change in fair value of plan assets      
Fair value, January 1 0 5 93
Actual Return on Plan Assets Still Held at the Reporting Date   0 (7)
Purchases, Sales and Settlements   (5) (81)
Fair value, December 31   0 5
Level 3 | Real estate commingled/mutual funds      
Change in fair value of plan assets      
Fair value, January 1 927 885 831
Actual Return on Plan Assets Still Held at the Reporting Date (4) 33 52
Purchases, Sales and Settlements 20 9 2
Fair value, December 31 943 927 885
Level 3 | Limited partnerships      
Change in fair value of plan assets      
Fair value, January 1 90 82 85
Actual Return on Plan Assets Still Held at the Reporting Date 2 0 (12)
Purchases, Sales and Settlements (9) 8 9
Fair value, December 31 83 90 82
Level 3 | Other investments      
Change in fair value of plan assets      
Fair value, January 1 636 588 74
Actual Return on Plan Assets Still Held at the Reporting Date 6 6 0
Purchases, Sales and Settlements 49 42 514
Fair value, December 31 $ 691 $ 636 $ 588