XML 96 R69.htm IDEA: XBRL DOCUMENT
v3.20.4

Retirement Plans (Cash Contributions For Qualified Pension Plan Benefit Payments For Non-Qualified OPEB Plans) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
OPEB [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Cash contribution to non-qualified OPEB plan | $ 19 | $ 22
Pension Non-qualified Plan [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Cash contributions to non-qualified pension plan | $ 31 | $ 30

X
- Definition The amount of contributions made by the employer that were non-qualified. + References No definition available. + Details
Name: | unp_DefinedBenefitPlanContributionsByEmployerNonQualified
Namespace Prefix: | unp_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of cash outflow for other postretirement benefit. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree. Excludes pension benefit. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3536-108585 + Details
Name: | us-gaap_OtherPostretirementBenefitsPayments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RetirementPlanTypeAxis=unp_PensionNonQualifiedPlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |