XML 55 R46.htm IDEA: XBRL DOCUMENT
v3.22.1

Note 5 - Retirement Plans (Details Textual) | 3 Months Ended
--- | ---
Mar. 31, 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