Revenues - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Payment period after invoice date	15 days
Expected period to recognized unearned portion of revenue for freight services in transit	The Company expects to recognize the unearned portion of revenue for freight services in transit within one week of the reporting date.
Non-Freight Receivables
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Amount related to conveyance of an easement included in non-freight receivables	$ 402	$ 224
Non-Freight Receivables | Virginia Line Segments
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Amount related to conveyance of an easement included in non-freight receivables	$ 168
Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Average transit time to complete a rail shipment	2 days
Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Average transit time to complete a rail shipment	8 days