v2.4.1.9
Debt (Details 3) (USD $)
12 Months Ended
Dec. 31, 2014
Jun. 30, 2014
Dec. 31, 2013
Jan. 01, 1997
Credit Facilities [Abstract]        
Line of credit facility replaced   $ 1,800,000,000unp_LineOfCreditFacilityReplaced    
Revolving credit facility available credit 1,700,000,000us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity      
Revolving credit facility withdrawals 0us-gaap_LineOfCredit      
Compliance with covenant At December 31, 2014, and December 31, 2013 (and at all times during the year), we were in compliance with this covenant.      
Allowable debt per debt-to-net-worth coverage ratio (as defined in the facility) 42,400,000,000unp_AllowableDebtPerDebtToNetWorthCoverageRatioAsDefinedFacility      
Outstanding debt (as defined by facility) 11,600,000,000unp_OutstandingDebtAsDefinedByFacility      
Cross-default provision (as defined by facility) 125,000,000unp_CrossDefaultProvisionAsDefinedByFacility      
Facility expiration date May 25, 2019      
Commercial paper outstanding 0us-gaap_CommercialPaper 0us-gaap_CommercialPaper    
Commercial paper issued 0us-gaap_ProceedsFromIssuanceOfCommercialPaper      
Commercial paper repaid 0us-gaap_RepaymentsOfCommercialPaper      
Dividend Restrictions [Abstract]        
Retained earnings available for dividends 15,400,000,000us-gaap_RetainedEarningsUnappropriated   16,300,000,000us-gaap_RetainedEarningsUnappropriated  
Mortgaged Properties [Abstract]        
Carrying value of equipment serving as collateral for capital leases and other types of equipment obligations 2,800,000,000unp_CarryingValueOfEquipmentServingAsCollateralForCapitalLeasesAndOtherTypesOfEquipmentObligations   2,900,000,000unp_CarryingValueOfEquipmentServingAsCollateralForCapitalLeasesAndOtherTypesOfEquipmentObligations  
Value of Missouri Pacific Railroad company assets that secured mortgage bonds       $ 6,000,000,000unp_ValueOfAssetsThatSecuredMortgageBonds