v2.4.1.9
Properties (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Property, Plant and Equipment [Line Items]      
Cost $ 63,214,000,000us-gaap_PropertyPlantAndEquipmentGross $ 59,812,000,000us-gaap_PropertyPlantAndEquipmentGross  
Accumulated depreciation 16,942,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment 16,063,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment  
Net book value 46,272,000,000us-gaap_PropertyPlantAndEquipmentNet 43,749,000,000us-gaap_PropertyPlantAndEquipmentNet  
Properties - Additional Disclosures [Abstract]      
Depreciable asset classes description We currently have more than 60 depreciable asset classes, and we may increase or decrease the number of asset classes due to changes in technology, asset strategies, or other factors.    
Total repairs and maintenance expense 2,400,000,000us-gaap_CostOfPropertyRepairsAndMaintenance 2,300,000,000us-gaap_CostOfPropertyRepairsAndMaintenance 2,100,000,000us-gaap_CostOfPropertyRepairsAndMaintenance
Land [Member]      
Property, Plant and Equipment [Line Items]      
Cost 5,194,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_LandMember		 5,120,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_LandMember		  
Net book value 5,194,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_LandMember		 5,120,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_LandMember		  
Road: Rail and Other Track Material [Member]      
Property, Plant and Equipment [Line Items]      
Cost 14,588,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadrailAndOtherTrackMaterialMemberMember		 13,861,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadrailAndOtherTrackMaterialMemberMember		  
Accumulated depreciation 5,241,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadrailAndOtherTrackMaterialMemberMember		 4,970,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadrailAndOtherTrackMaterialMemberMember		  
Net book value 9,347,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadrailAndOtherTrackMaterialMemberMember		 8,891,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadrailAndOtherTrackMaterialMemberMember		  
Estimated useful life 33 years 35 years  
Road: Ties [Member]      
Property, Plant and Equipment [Line Items]      
Cost 9,102,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadTiesMember		 8,785,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadTiesMember		  
Accumulated depreciation 2,450,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadTiesMember		 2,310,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadTiesMember		  
Net book value 6,652,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadTiesMember		 6,475,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadTiesMember		  
Estimated useful life 33 years 33 years  
Road: Ballast [Member]      
Property, Plant and Equipment [Line Items]      
Cost 4,826,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadBallastMember		 4,621,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadBallastMember		  
Accumulated depreciation 1,264,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadBallastMember		 1,171,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadBallastMember		  
Net book value 3,562,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadBallastMember		 3,450,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadBallastMember		  
Estimated useful life 34 years 34 years  
Road: Other Roadway [Member]      
Property, Plant and Equipment [Line Items]      
Cost 16,476,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadOtherMember		 [1] 15,596,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadOtherMember		 [1]  
Accumulated depreciation 2,852,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadOtherMember		 [1] 2,726,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadOtherMember		 [1]  
Net book value 13,624,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadOtherMember		 [1] 12,870,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_RoadOtherMember		 [1]  
Estimated useful life 47 years [1] 48 years [1]  
Total Road [Member]      
Property, Plant and Equipment [Line Items]      
Cost 44,992,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_TotalRoadMember		 42,863,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_TotalRoadMember		  
Accumulated depreciation 11,807,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_TotalRoadMember		 11,177,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_TotalRoadMember		  
Net book value 33,185,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_TotalRoadMember		 31,686,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_TotalRoadMember		  
Equipment: Locomotives [Member]      
Property, Plant and Equipment [Line Items]      
Cost 8,276,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentLocomotivesMember		 7,518,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentLocomotivesMember		  
Accumulated depreciation 3,694,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentLocomotivesMember		 3,481,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentLocomotivesMember		  
Net book value 4,582,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentLocomotivesMember		 4,037,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentLocomotivesMember		  
Estimated useful life 20 years 20 years  
Equipment: Freight Cars [Member]      
Property, Plant and Equipment [Line Items]      
Cost 2,116,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentFreightCarsMember		 2,085,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentFreightCarsMember		  
Accumulated depreciation 968,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentFreightCarsMember		 1,000,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentFreightCarsMember		  
Net book value 1,148,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentFreightCarsMember		 1,085,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentFreightCarsMember		  
Estimated useful life 25 years 25 years  
Equipment: Work Equipment and Other [Member]      
Property, Plant and Equipment [Line Items]      
Cost 684,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentWorkEquipmentAndOtherMember		 561,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentWorkEquipmentAndOtherMember		  
Accumulated depreciation 153,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentWorkEquipmentAndOtherMember		 119,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentWorkEquipmentAndOtherMember		  
Net book value 531,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentWorkEquipmentAndOtherMember		 442,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_EquipmentWorkEquipmentAndOtherMember		  
Estimated useful life 18 years 18 years  
Total Equipment [Member]      
Property, Plant and Equipment [Line Items]      
Cost 11,076,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_TotalEquipmentMember		 10,164,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_TotalEquipmentMember		  
Accumulated depreciation 4,815,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_TotalEquipmentMember		 4,600,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_TotalEquipmentMember		  
Net book value 6,261,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_TotalEquipmentMember		 5,564,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= unp_TotalEquipmentMember		  
Technology and Other [Member]      
Property, Plant and Equipment [Line Items]      
Cost 872,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_TechnologyEquipmentMember		 711,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_TechnologyEquipmentMember		  
Accumulated depreciation 320,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_TechnologyEquipmentMember		 286,000,000us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_TechnologyEquipmentMember		  
Net book value 552,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_TechnologyEquipmentMember		 425,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_TechnologyEquipmentMember		  
Estimated useful life 10 years 10 years  
Construction in Progress [Member]      
Property, Plant and Equipment [Line Items]      
Cost 1,080,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_ConstructionInProgressMember		 954,000,000us-gaap_PropertyPlantAndEquipmentGross
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_ConstructionInProgressMember		  
Accumulated depreciation 0us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_ConstructionInProgressMember		 0us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_ConstructionInProgressMember		  
Net book value $ 1,080,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_ConstructionInProgressMember		 $ 954,000,000us-gaap_PropertyPlantAndEquipmentNet
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_ConstructionInProgressMember		  
[1] Other roadway includes grading, bridges and tunnels, signals, buildings, and other road assets.