Nature of Operations and Significant Accounting Policies (Details) $ in Millions				3 Months Ended			6 Months Ended		24 Months Ended
	Jul. 01, 2021 USD ($)	Jun. 04, 2021 USD ($) shares	Apr. 14, 2021 USD ($)	Dec. 31, 2021 USD ($)	Jun. 30, 2021 USD ($) state mi	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) state mi	Jun. 30, 2020 USD ($)	Mar. 26, 2023	May 12, 2021 terminalAndFacility	Mar. 26, 2021 USD ($) phase property	Dec. 31, 2020 USD ($)	[1]	Nov. 30, 2020 mi
Revenue from External Customer [Line Items]
Total number of rail route miles | mi					19,500		19,500
Number of states rail network serves | state					23		23
Gain recognized on property dispositions					$ 367	$ 11	$ 370	$ 29
Proceeds from property dispositions							227	$ 45
Stock split conversion ratio		3
Number of additional shares of common stock received for each share held after stock split (in shares) | shares		2
Reclassification to other capital					11,723		11,723					$ 11,259
Reclassification from retained earnings					$ 0		$ 0					$ 152
Virginia Line Segments
Revenue from External Customer [Line Items]
Number of property rights for sale | property											3
Number of phases to complete property rights sale transaction | phase											3
Total sale price											$ 525
Gain recognized on property dispositions			$ 349
Proceeds from property dispositions			$ 200
Revision of Prior Period, Reclassification, Adjustment | Stock split reclassification adjustment
Revenue from External Customer [Line Items]
Reclassification to other capital		$ (1,000)
Reclassification from retained earnings		$ 1,000
Subsequent Event | Forecast | Virginia Line Segments
Revenue from External Customer [Line Items]
Proceeds from property dispositions				$ 168
Period to complete closing on the remaining sale transaction									2 years
Acquisition of Quality Carriers | Subsequent Event
Revenue from External Customer [Line Items]
Purchase price in cash paid for acquisition	$ 546
Acquisition of Quality Carriers | Acquisition of Quality Carriers | United States, Canada and Mexico
Revenue from External Customer [Line Items]
Number of terminals and facilities (over) | terminalAndFacility										100
Acquisition of Pan-Am | Acquisition of Pan-Am
Revenue from External Customer [Line Items]
Total number of rail route miles | mi														1,200
Number of partial interests in rail route miles (more than) | mi														600

[1] Certain prior year data has been retroactively adjusted to reflect the stock split effective June 28, 2021. See accompanying notes to consolidated financial statements.