Name:	unp_AllowableDebtPerDebtToNetWorthCoverageRatioAsDefinedFacility
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Data Type:	xbrli:monetaryItemType
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Amount of debt issuance authorized by Board of Directors.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of debt issuance remaining under current authority by Board of Directors.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Maximum duration of commercial paper maturities, in 'PnYnMnDTnHnMnS' format, for example, P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	unp_CommercialPaperMaturityDurationMaximum
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Data Type:	xbrli:durationItemType
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Minimum duration of commercial paper maturities, in 'PnYnMnDTnHnMnS' format, for example, P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

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Cross-default provision, as defined by facility.

No definition available.

Name:	unp_CrossDefaultProvisionAsDefinedByFacility
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Outstanding debt as defined by the credit facility.

No definition available.

Name:	unp_OutstandingDebtAsDefinedByFacility
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Data Type:	xbrli:monetaryItemType
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Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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Period Type:	instant

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Period Type:	instant

Amount of assets pledged to secure a debt instrument.

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Period Type:	instant

Contractual interest rate for funds borrowed, under the debt agreement.

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Percentage of principal amount of debt redeemed.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Fair value amount of debt instrument that was repurchased.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Date the debt instrument was repurchased, in YYYY-MM-DD format.

No definition available.

Name:	us-gaap_DebtInstrumentRepurchaseDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Date the credit facility terminates, in YYYY-MM-DD format.

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Name:	us-gaap_LineOfCreditFacilityExpirationDate1
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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Data Type:	xbrli:monetaryItemType
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The cash inflow from borrowing by issuing commercial paper.

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Data Type:	xbrli:monetaryItemType
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The cash outflow due to repaying amounts borrowed by issuing commercial paper.

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Namespace Prefix:	us-gaap_
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