Investment in Affiliates and Related-Party Transactions - Equity-method Investments in Affiliates (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Related Party Transaction [Line Items]
Total	$ 2,099	$ 1,985
Corporate Joint Venture | Conrail
Related Party Transaction [Line Items]
Total	1,083	1,025
Affiliated Entity
Related Party Transaction [Line Items]
Total	2,099	1,985
Affiliated Entity | TTX
Related Party Transaction [Line Items]
Total	849	796
Affiliated Entity | Other
Related Party Transaction [Line Items]
Total	$ 167	$ 164