v2.4.1.9
Stock Options and Other Stock Plans (Details 1)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Stock Options And Other Stock Plans Details [Abstract]      
Shares of common stock authorized and available 77,786,772us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant 79,574,896us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant 64,337,040us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
Union Pacific Corporation 1992 Restricted Stock Plan For Non-Employee Directors [Member]      
Stock Options And Other Stock Plans Details [Abstract]      
Restricted shares outstanding 7,140us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= unp_UnionPacificCorporation1992RestrictedStockPlanForNonEmployeeDirectorsMember		    
Union Pacific Corporation 2000 Directors Plan [Member]      
Stock Options And Other Stock Plans Details [Abstract]      
Stock options, shares outstanding 78,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= unp_UnionPacificCorporation2000DirectorsPlanMember		    
Restricted shares outstanding 36,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber
/ us-gaap_AwardTypeAxis
= unp_UnionPacificCorporation2000DirectorsPlanMember		    
Common stock reserved for issuance 2,200,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_AwardTypeAxis
= unp_UnionPacificCorporation2000DirectorsPlanMember		    
Initial grant of retention stock share/units description Under the Directors Plan, each non-employee director, upon his or her initial election to the Board of Directors, receives a grant of 4,000 retention shares or retention stock units. Prior to December 31, 2007, each non-employee director received annually an option to purchase at fair value a number of shares of our common stock, not to exceed 20,000 shares during any calendar year, determined by dividing 60,000 by 1/3 of the fair market value of one share of our common stock on the date of such Board of Directors meeting, with the resulting quotient rounded up or down to the nearest 50 shares.    
Union Pacific Corporation 2004 Stock Incentive Plan [Member]      
Stock Options And Other Stock Plans Details [Abstract]      
Stock options, shares outstanding 4,338,691us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= unp_UnionPacificCorporation2004StockIncentivePlanMember		    
Retention shares and stock units 3,677,642us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= unp_UnionPacificCorporation2004StockIncentivePlanMember		    
Common stock reserved for issuance 84,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_AwardTypeAxis
= unp_UnionPacificCorporation2004StockIncentivePlanMember		    
Union Pacific Corporation 2013 Stock Incentive Plan [Member]      
Stock Options And Other Stock Plans Details [Abstract]      
Stock options, shares outstanding 969,822us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= unp_UnionPacificCorporation2013StockIncentivePlanMember		    
Retention shares and stock units 1,307,905us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
/ us-gaap_AwardTypeAxis
= unp_UnionPacificCorporation2013StockIncentivePlanMember		    
Common stock reserved for issuance 78,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_AwardTypeAxis
= unp_UnionPacificCorporation2013StockIncentivePlanMember