Segments - Schedule of Segment Reporting (Details) - USD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Segment Reporting Information, Profit (Loss)                      
Operating revenue $ 11,439 $ 12,560 $ 12,536 $ 10,472 $ 10,742 $ 11,953 $ 11,775 $ 9,968 $ 47,007 $ 44,438 $ 41,138
Operating income (loss) 1,399 $ 2,071 $ 2,128 $ 1,020 1,090 $ 1,645 $ 1,684 $ 844 6,618 5,264 5,966
Interest expense (income), net                 301 311 396
Depreciation and amortization                 2,581 2,329 2,222
Total assets 64,532       60,266       64,532 60,266 53,671
Capital expenditures                 4,936 5,168 3,891
Operating Segments | Airline                      
Segment Reporting Information, Profit (Loss)                      
Operating revenue                 46,910 43,890 40,636
Operating income (loss)                 6,542 5,206 5,856
Interest expense (income), net                 327 334 403
Depreciation and amortization                 2,581 2,329 2,222
Total assets 62,793       58,561       62,793 58,561 51,544
Capital expenditures                 4,880 5,005 3,743
Operating Segments | Refinery                      
Segment Reporting Information, Profit (Loss)                      
Operating revenue                 5,558 5,458 5,039
Operating income (loss)                 76 58 110
Interest expense (income), net                 (26) (23) (7)
Depreciation and amortization                 99 67 47
Total assets $ 1,739       $ 1,705       1,739 1,705 2,127
Capital expenditures                 56 163 148
Intersegment Sales/Other                      
Segment Reporting Information, Profit (Loss)                      
Depreciation and amortization                 (99) (67) (47)
Intersegment Sales/Other | Sales to airline segment                      
Segment Reporting Information, Profit (Loss)                      
Operating revenue                 (1,103) (962) (886)
Intersegment Sales/Other | Exchanged products                      
Segment Reporting Information, Profit (Loss)                      
Operating revenue                 (3,963) (3,596) (3,240)
Intersegment Sales/Other | Sales of refined products                      
Segment Reporting Information, Profit (Loss)                      
Operating revenue                 $ (395) $ (352) $ (411)