Quarterly Financial Data (Unaudited)
 12 Months Ended
Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]  
Quarterly Financial Data (Unaudited) QUARTERLY FINANCIAL DATA (UNAUDITED)
The following table summarizes our unaudited results of operations on a quarterly basis. The quarterly earnings per share amounts for a year will not add to the earnings per share for that year due to the weighting of shares used in calculating per share data.
Three Months Ended,
(in millions, except per share data)March 31June 30September 30December 31
2019
Operating revenue$10,472  $12,536  $12,560  $11,439  
Operating income1,020  2,128  2,071  1,399  
Net income730  1,443  1,495  1,099  
Basic earnings per share$1.10  $2.22  $2.32  $1.71  
Diluted earnings per share$1.09  $2.21  $2.31  $1.71  
2018
Operating revenue$9,968  $11,775  $11,953  $10,742  
Operating income844  1,684  1,645  1,090  
Net income557  1,036  1,322  1,019  
Basic earnings per share$0.79  $1.49  $1.93  $1.50  
Diluted earnings per share$0.79  $1.49  $1.92  $1.49