XML 87 R60.htm IDEA: XBRL DOCUMENT
v3.20.4

Retirement Plans (Other Retirement Programs) (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items] |  |  |
401(k)/Thrift plan description | For non-union employees hired prior to January 1, 2018, and eligible union employees for whom we make matching contributions, we provide a defined contribution plan (401(k)/thrift plan). |  |
401(k)/Thrift plan contributions | $ 19 | $ 20 | $ 18
Defined Contribution Plan, Employer Matching Contribution, Percent of Match | 50.00% |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay | 6.00% |  |
Railroad Retirement System [Abstract] |  |  |
Railroad Retirement System description | All Railroad employees are covered by the Railroad Retirement System (the System). |  |
Railroad Retirement System contributions | $ 569 | 654 | 710
401(k)/ Thrift Plan 2018 or later [Member] |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
401(k)/Thrift plan description | January 1, 2018 |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Match | 100.00% |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay | 6.00% |  |
Defined contribution plan, additional annual employer contribution, percent of employee's gross pay | 3.00% |  |
Collective Bargaining Agreements [Member] |  |  |
Collective Bargaining Agreements [Abstract] |  |  |
Collective bargaining agreements description | Under collective bargaining agreements, we participate in multi-employer benefit plans that provide certain postretirement health care and life insurance benefits for eligible union employees |  |
Collective bargaining agreements premiums | $ 30 | $ 42 | $ 50

X
- Definition Percentage of employees' gross pay for which the employer contributes anannual contribution to a defined contribution plan in addition to the matching contributions. + References No definition available. + Details
Name: | unp_DefinedContributionPlanAdditionalAnnualEmployerContributionPercentOfEmployeeSGrossPay
Namespace Prefix: | unp_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Contribution made to the railroad retirement system for the benefit of the employee. + References No definition available. + Details
Name: | unp_RailroadRetirementSystemContributions
Namespace Prefix: | unp_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Retirement System that provides retirement benefits for railroad employees. + References No definition available. + Details
Name: | unp_RailroadRetirementSystemDescription
Namespace Prefix: | unp_
Data Type: | xbrli:stringItemType
Balance Type: | na
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 cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
Name: | us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage employer matches of the employee's percentage contribution matched. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Description of defined contribution pension and other postretirement plans. + References No definition available. + Details
Name: | us-gaap_DescriptionOfDefinedContributionPensionAndOtherPostretirementPlans
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Description of the nature of multiemployer plan benefits as well as who is covered by the benefits. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 7 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450678-114947 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450702-114947 + Details
Name: | us-gaap_MultiemployerPlansPlanBenefitsDescription
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of contributions made by entity participating in defined benefit plan, defined as multiple-employer plan but accounted for as multiemployer plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 55 -Paragraph 64 -URI http://asc.fasb.org/extlink&oid=65881987&loc=d3e16414-114935 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Section 55 -Paragraph 63 -URI http://asc.fasb.org/extlink&oid=65881987&loc=d3e16378-114935 + Details
Name: | us-gaap_MultipleEmployerPlanAccountedForAsMultiemployerPlanContributionByParticipatingEntity
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Details
Name: | us-gaap_RetirementPlanNameAxis=unp_FourZeroOneThriftPlan2018BeyondMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CollectiveBargainingArrangementAxis=us-gaap_CollectiveBargainingArrangementOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |