v2.4.1.9
Income Taxes (Details 1) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Current Income Tax Expense [Abstract]      
Current federal income tax expense $ 2,029us-gaap_CurrentFederalTaxExpenseBenefit $ 1,738us-gaap_CurrentFederalTaxExpenseBenefit $ 1,335us-gaap_CurrentFederalTaxExpenseBenefit
Current state income tax expense 239us-gaap_CurrentStateAndLocalTaxExpenseBenefit 199us-gaap_CurrentStateAndLocalTaxExpenseBenefit 153us-gaap_CurrentStateAndLocalTaxExpenseBenefit
Total current income tax expense 2,268us-gaap_CurrentIncomeTaxExpenseBenefit 1,937us-gaap_CurrentIncomeTaxExpenseBenefit 1,488us-gaap_CurrentIncomeTaxExpenseBenefit
Deferred Income Tax Expense [Abstract]      
Deferred federal income tax expense 667us-gaap_DeferredFederalIncomeTaxExpenseBenefit 659us-gaap_DeferredFederalIncomeTaxExpenseBenefit 760us-gaap_DeferredFederalIncomeTaxExpenseBenefit
Deferred state income tax expense 136us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit 119us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit 120us-gaap_DeferredStateAndLocalIncomeTaxExpenseBenefit
Total deferred income tax expense 803us-gaap_DeferredIncomeTaxExpenseBenefit 778us-gaap_DeferredIncomeTaxExpenseBenefit 880us-gaap_DeferredIncomeTaxExpenseBenefit
Unrecognized Tax Benefits [Abstract]      
Unrecognized federal tax benefits expense / (benefits) 86unp_UnrecognizedFederalTaxBenefitsExpenseBenefit (54)unp_UnrecognizedFederalTaxBenefitsExpenseBenefit 5unp_UnrecognizedFederalTaxBenefitsExpenseBenefit
Unrecognized state tax benefits expense / (benefits) 6unp_UnrecognizedStateAndLocalTaxBenefitsExpenseBenefit (1)unp_UnrecognizedStateAndLocalTaxBenefitsExpenseBenefit 2unp_UnrecognizedStateAndLocalTaxBenefitsExpenseBenefit
Unrecognized tax benefits expense / (benefits) 92unp_UnrecognizedTaxBenefitsExpenseBenefit (55)unp_UnrecognizedTaxBenefitsExpenseBenefit 7unp_UnrecognizedTaxBenefitsExpenseBenefit
Total income tax expense $ 3,163us-gaap_IncomeTaxExpenseBenefit $ 2,660us-gaap_IncomeTaxExpenseBenefit $ 2,375us-gaap_IncomeTaxExpenseBenefit