Nature of Operations and Significant Accounting Policies (Details) $ in Millions	Mar. 31, 2019 USD ($) state mi	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Total number of rail route miles | mi	20,500
Number of states rail network serves | state	23
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-Use Lease Asset	$ 550		$ 0
Operating lease liability	$ 555
ASU Leases
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-Use Lease Asset		$ 534
Operating lease liability		$ 534