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Investments (Details) $ in Millions	3 Months Ended		12 Months Ended
Investments (Details) $ in Millions	Mar. 31, 2021 USD ($) railroad	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Schedule of Investments [Line Items]
Number of North American railroads \| railroad	8
Equity Method Investee
Schedule of Investments [Line Items]
Equity method investment, ownership percentage	58.00%
Conrail Voting
Schedule of Investments [Line Items]
Equity method investment, ownership percentage	50.00%
Conrail Inc
Schedule of Investments [Line Items]
Equity method investments	$ 1,500		$ 1,400
Expenses from transactions with related party	34	$ 35
Equity in the earnings of investee	14	9
Due to affiliate, noncurrent	$ 534		$ 534
Due to affiliate, average interest rate	1.31%		1.31%
TTX Company
Schedule of Investments [Line Items]
Equity method investment, ownership percentage	19.65%
Expenses from transactions with related party	$ 63	60
Equity in the earnings of investee	$ 17	$ 4