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Compensation Plans (Stock Based Award Activities) (Details) - Restricted Stock Units (RSUs) - USD ($)
$ / shares in Units, $ in Billions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Number of Shares      
Unvested at beginning of period (in shares) 18,467,678    
Granted (in shares) 13,934,041    
Vested (in shares) (11,576,766)    
Forfeited/canceled (in shares) (1,430,717)    
Unvested at end of period (in shares) 19,394,236 18,467,678  
Weighted- Average Grant-Date Fair Value      
Unvested at beginning of period (in dollars per share) $ 936.96    
Granted (in dollars per share) 1,092.36 $ 1,095.89 $ 845.06
Vested (in dollars per share) 919.28    
Forfeited/canceled (in dollars per share) 990.56    
Unvested at end of period (in dollars per share) $ 1,055.22 $ 936.96  
Fair value of vested awards $ 15.2 $ 14.1 $ 11.3
Unrecognized compensation cost $ 19.1    
Period for recognized of unrecognized compensation cost 2 years 7 months 6 days