Retirement Plans (Other Retirement Programs) (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
401(k)/Thrift Plan [Abstract]
401(k)/Thrift plan description	For non-union employees hired prior to January 1, 2018, and eligible union employees for whom we make matching contributions, we provide a defined contribution plan (401(k)/thrift plan).
401(k)/Thrift plan contributions	$ 20	$ 18	$ 19
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	50.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Railroad Retirement System [Abstract]
Railroad Retirement System description	All Railroad employees are covered by the Railroad Retirement System (the System).
Railroad Retirement System contributions	$ 654	710	672
401(k)/ Thrift Plan 2018 or later [Member]
401(k)/Thrift Plan [Abstract]
401(k)/Thrift plan description	January 1, 2018
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	100.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6.00%
Defined contribution plan, additional annual employer contribution, percent of employee's gross pay	3.00%
Collective Bargaining Agreements [Member]
Collective Bargaining Agreements [Abstract]
Collective bargaining agreements description	Under collective bargaining agreements, we participate in multi-employer benefit plans that provide certain postretirement health care and life insurance benefits for eligible union employees.
Collective bargaining agreements premiums	$ 42	$ 50	$ 60