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v3.20.4

Debt (Equipment Encumbrances) (Narrative) (Details) - USD ($) $ in Billions | Dec. 31, 2020 | Dec. 31, 2019
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Debt [Abstract] |  |
Carrying value of equipment serving as collateral for finance leases and other types of equipment obligations | $ 1.3 | $ 1.6

X
- Definition Carrying value of equipment serving as collateral for finance leases and other types of equipment obligations. + References No definition available. + Details
Name: | unp_CarryingValueOfEquipmentServingAsCollateralForFinanceLeasesAndOtherTypesOfEquipmentObligations
Namespace Prefix: | unp_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_DebtDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration