Annual report pursuant to Section 13 and 15(d)

Postretirement Health Care and Life Insurance Benefits (One Percentage Point Change In Assumed Health Care Cost Rates Would Have The Following Effects) (Details)

v2.4.1.9
Postretirement Health Care and Life Insurance Benefits (One Percentage Point Change In Assumed Health Care Cost Rates Would Have The Following Effects) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Jan. 31, 2015
Postretirement Medical Plans with Prescription Drug Benefits [Abstract]  
Effect on total of service and interest cost, 1 - percentage point increase $ 0us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnServiceAndInterestCostComponents
Effect on total of service and interest cost, 1 - percentage point decrease 0us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnServiceAndInterestCostComponents1
Effect on accumulated postretirement benefit obligations, 1 - percentage point increase 17us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointIncreaseOnAccumulatedPostretirementBenefitObligation
Effect on accumulated postretirement benefit obligations, 1 - percentage point decrease $ (15)us-gaap_DefinedBenefitPlanEffectOfOnePercentagePointDecreaseOnAccumulatedPostretirementBenefitObligation1