v2.4.1.9
Debt (Details 6) (Bonds [Member], 5.65% Notes Due 2022 [Member], USD $)
In Millions, unless otherwise specified
0 Months Ended 3 Months Ended 12 Months Ended
May 14, 2013
Jun. 30, 2013
Dec. 31, 2014
Bonds [Member] | 5.65% Notes Due 2022 [Member]
     
Extinguishment of Debt [Line Items]      
Debt redemption $ 40us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_DebtInstrumentAxis
= unp_NotesDue2022565PercentMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_LongTermDebtMember
   
Interest rate on note 5.65%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= unp_NotesDue2022565PercentMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_LongTermDebtMember
   
Due date of debt     Dec. 01, 2022
Early extinguishment of debt   $ (1)us-gaap_GainsLossesOnExtinguishmentOfDebt
/ us-gaap_DebtInstrumentAxis
= unp_NotesDue2022565PercentMember
/ us-gaap_ExtinguishmentOfDebtAxis
= us-gaap_LongTermDebtMember