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Financial Instruments (Details) (USD $)
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12 Months Ended | ||
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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| Earnings Impact [Abstract] | |||
| Increase in pre-tax income | $ 0us-gaap_DerivativeGainLossOnDerivativeNet | $ 0us-gaap_DerivativeGainLossOnDerivativeNet | $ 0us-gaap_DerivativeGainLossOnDerivativeNet |
| Fair Value of Debt Instruments [Abstract] | |||
| Fair value of total debt | 13,000,000,000us-gaap_DebtInstrumentFairValue | 10,200,000,000us-gaap_DebtInstrumentFairValue | |
| Fair value of total debt in excess of carrying value | 1,500,000,000unp_FairValueOfTotalDebtInExcessOfCarryingValue | 600,000,000unp_FairValueOfTotalDebtInExcessOfCarryingValue | |
| Fixed rate debt securities containing call provisions | 163,000,000unp_FixedRateDebtSecuritiesContainingCallProvisions | 163,000,000unp_FixedRateDebtSecuritiesContainingCallProvisions | |
| Interest Rate Cash Flow Hedges [Abstract] | |||
| Change in fair value of cash flow hedges as reported in accumulated other comprehensive loss | 0us-gaap_UnrealizedGainLossOnInterestRateCashFlowHedgesPretaxAccumulatedOtherComprehensiveIncomeLoss | 1,000,000us-gaap_UnrealizedGainLossOnInterestRateCashFlowHedgesPretaxAccumulatedOtherComprehensiveIncomeLoss | |
| Interest rate cash flow hedges outstanding | 0us-gaap_InterestRateCashFlowHedgeDerivativeAtFairValueNet | 0us-gaap_InterestRateCashFlowHedgeDerivativeAtFairValueNet | |
| Interest Rate Derivatives [Abstract] | |||
| Interest rate fair value hedges outstanding | 0us-gaap_InterestRateFairValueHedgeDerivativeAtFairValueNet | 0us-gaap_InterestRateFairValueHedgeDerivativeAtFairValueNet | |
| Market and Credit Risk [Abstract] | |||
| Collateral for hedging activity | $ 0us-gaap_CollateralAlreadyPostedAggregateFairValue | $ 0us-gaap_CollateralAlreadyPostedAggregateFairValue | |
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- Definition
Fair value of total debt in excess of carrying value. No definition available.
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- Definition
Amount of debt securities that contain a provision to retire the debt instrument prior to final maturity, with the payment of fixed call premiums, or in certain cases, at par. No definition available.
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- Definition
The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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- Definition
Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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- Details
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- Definition
Fair value as of the balance sheet date of all interest rate derivatives designated as cash flow hedging instruments. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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- Definition
Fair value of all derivatives designated as interest rate fair value hedging instruments. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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- Definition
Amount of unrealized gain (loss) related to the increase or decrease in fair value of interest rate derivatives designated as cash flow hedging instruments, which was recorded in accumulated other comprehensive income to the extent that the cash flow hedge was determined to be effective. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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