Property and Equipment, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 70,940	$ 67,380
Accumulated Depreciation and Amortization	8,627	6,130
Property and Equipment, Net	62,313	61,250
Interest Costs Capitalized	22	26	$ 34
Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	6,088	6,063
Track Structure [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	23,217	22,287
Other Roadway [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	28,103	25,990
Locomotives [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	8,528	8,338
Freight Cars and Other Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	2,940	2,755
Computer Hardware, Software and Other [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	1,075	982
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	989	965
Property and Equipment under Capital Lease [Member]
Property, Plant and Equipment [Line Items]
Accumulated Depreciation and Amortization	382	333
Capital Leased Asset, Net	$ 687	$ 738
Minimum [Member] | Track Structure [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	15 years
Minimum [Member] | Other Roadway [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	9 years
Minimum [Member] | Locomotives [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	7 years
Minimum [Member] | Freight Cars and Other Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	8 years
Minimum [Member] | Computer Hardware, Software and Other [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	6 years
Maximum [Member] | Track Structure [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	50 years
Maximum [Member] | Other Roadway [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	100 years
Maximum [Member] | Locomotives [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	35 years
Maximum [Member] | Freight Cars and Other Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	41 years
Maximum [Member] | Computer Hardware, Software and Other [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	15 years