Segment Reporting and Significant Expenses- Narrative (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) segment	Jun. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
Segment Reporting, Asset Reconciling Item [Line Items]
Number of operating segments | segment			2
Assets	$ 42,929		$ 42,929		$ 42,764
Rail Operations
Segment Reporting, Asset Reconciling Item [Line Items]
Segment, expenditure, addition to long-lived assets	766	$ 524	1,457	$ 1,021
Assets	$ 42,700		$ 42,700		$ 42,600