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v3.22.2

Note 5 - Retirement Plans (Details Textual) | 6 Months Ended
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Jun. 30, 2022
Defined Benefit Plan, Expected Return on Plan Assets, Changes In Fair Value, Period (Year) | 5 years

X
- Definition The expected long-term rate of return on plan assets that is applied to a calculated value of plan assets that recognizes the changes in fair value over this period. + References No definition available. + Details
Name: | unp_DefinedBenefitPlanExpectedReturnOnPlanAssetsChangesInFairValuePeriod
Namespace Prefix: | unp_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration