Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 17, 2015
Document and Entity Information [Abstract]
Document type	10-Q
Document period end date	Mar. 31, 2015
Amendment flag	false
Entity registrant name	UNION PACIFIC CORP
Entity central index key	0000100885
Entity current reporting status	Yes
Entity voluntary filers	No
Current fiscal year end date	--12-31
Entity filer category	Large Accelerated Filer
Entity well known seasoned issuer	Yes
Document fiscal year focus	2015
Document fiscal period focus	Q1
Trading Symbol	unp
Entity common stock shares outstanding		875,590,576