v2.4.1.9
Retirement Plans (Details 9) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
401(k)/Thrift Plan [Abstract]      
401(k)/Thrift plan description We provide a defined contribution plan (401(k)/thrift plan) to eligible non-union and union employees for whom we make matching contributions. We match 50 cents for each dollar contributed by employees up to the first six percent of compensation contributed.    
401(k)/Thrift plan contributions $ 19us-gaap_DefinedContributionPlanCostRecognized $ 18us-gaap_DefinedContributionPlanCostRecognized $ 15us-gaap_DefinedContributionPlanCostRecognized
Railroad Retirement System [Abstract]      
Railroad Retirement System description All Railroad employees are covered by the Railroad Retirement System (the System).    
Railroad Retirement System contributions 711unp_RailroadRetirementSystemContributions 670unp_RailroadRetirementSystemContributions 644unp_RailroadRetirementSystemContributions
Collective Bargaining Agreements [Abstract]      
Collective bargaining agreements description Under collective bargaining agreements, we participate in multi-employer benefit plans that provide certain postretirement health care and life insurance benefits for eligible union employees.    
Collective bargaining agreements premiums $ 52us-gaap_MultiemployerPlanPeriodContributions $ 57us-gaap_MultiemployerPlanPeriodContributions $ 62us-gaap_MultiemployerPlanPeriodContributions