Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenues	$ 23,515	$ 23,855	$ 21,387
Operating expenses:
Compensation and benefits	5,347	5,394	5,023
Fuel	2,944	3,346	2,518
Purchased services	2,700	2,870	2,514
Depreciation and amortization	2,403	2,317	2,352
Equipment rents	758	732	784
Materials and other	1,292	1,396	903
Total operating expenses	15,444	16,055	14,094
Operating income	8,071	7,800	7,293
Interest expense	1,070	1,041	1,016
Other (income) expense, net	(249)	(104)	(51)
Income before income taxes	7,250	6,863	6,328
Income tax expense (benefit)	1,769	1,644	(4,972)
Net income	$ 5,481	$ 5,219	$ 11,300