Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2023	Feb. 02, 2024	Jun. 30, 2023
Document Information [Line Items]
Entity Central Index Key	0000100885
Entity Registrant Name	UNION PACIFIC CORP
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2023
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	1-6075
Entity Incorporation, State or Country Code	UT
Entity Tax Identification Number	13-2626465
Entity Address, Postal Zip Code	68179
Entity Address, Address Line One	1400 Douglas Street
Entity Address, City or Town	Omaha
Entity Address, State or Province	NE
City Area Code	402
Local Phone Number	544-5000
Title of 12(b) Security	Common Stock (Par Value $2.50 per share)
Trading Symbol	UNP
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 123,000,000,000
Entity Common Stock, Shares Outstanding		609,777,914
Auditor Firm ID	34
Auditor Name	Deloitte & Touche LLP
Auditor Location	Omaha, Nebraska