XML 31 R43.htm IDEA: XBRL DOCUMENT v2.4.1.9
Stock-based Compensation (Schedule of Stock Options Weight Average Assumptions) (Details) (USD $)
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Stock Options [Member]    
Assumptions For Stock Awards [Abstract]    
Risk-free interest rate 1.30%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_StockOptionMember
1.60%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_StockOptionMember
Dividend yield 1.80%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_StockOptionMember
2.10%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_StockOptionMember
Expected life (years) 5 years 1 month 6 days 5 years 2 months 12 days
Volatility 23.40%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_StockOptionMember
30.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_StockOptionMember
Weighted-average grant-date fair value of options granted $ 22.30us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_StockOptionMember
$ 20.18us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= us-gaap_StockOptionMember
Performance Retention Awards [Member]    
Assumptions For Stock Awards [Abstract]    
Dividend per share per quarter $ 0.55unp_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendPerShare
/ us-gaap_AwardTypeAxis
= unp_PerformanceRetentionAwardsMember
 
Risk-free interest rate 0.80%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= unp_PerformanceRetentionAwardsMember