Annual report pursuant to Section 13 and 15(d)

MARKETABLE SECURITIES (Details)

v2.4.1.9
MARKETABLE SECURITIES (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Schedule of Available-for-sale Securities      
Cost $ 92us-gaap_AvailableForSaleSecuritiesAmortizedCost $ 136us-gaap_AvailableForSaleSecuritiesAmortizedCost  
Gross Unrealized Gain (Loss) 1us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax 14us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax  
Estimated fair value 93us-gaap_AvailableForSaleSecurities 150us-gaap_AvailableForSaleSecurities  
Prior Period Reclassification Adjustment   72cmi_MarketableSecuritiesFairValuereclassifiedfromLevel1toLevel2  
Proceeds from sales and maturities of marketable securities 336us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities 525us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities 585us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities
Gross realized gains from the sale of available-for-sale securities 14us-gaap_AvailableForSaleSecuritiesGrossRealizedGains [1] 14us-gaap_AvailableForSaleSecuritiesGrossRealizedGains [1] 3us-gaap_AvailableForSaleSecuritiesGrossRealizedGains [1]
Quoted prices in active markets for identical assets (Level 1)      
Schedule of Available-for-sale Securities      
Cost   10us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member 		[2],[3]  
Gross Unrealized Gain (Loss)   13us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member 		[2],[3]  
Estimated fair value   23us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member 		[2],[3]  
Quoted prices in active markets for identical assets (Level 1) | Equity Securities      
Schedule of Available-for-sale Securities      
Cost   10us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember 		[2],[3],[4]  
Gross Unrealized Gain (Loss)   13us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember 		[2],[3],[4]  
Estimated fair value   23us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember 		[2],[3],[4]  
Gross realized gains from the sale of available-for-sale securities   9us-gaap_AvailableForSaleSecuritiesGrossRealizedGains
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember 		 
Significant other observable inputs (Level 2)      
Schedule of Available-for-sale Securities      
Cost 92us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member 		[3],[5] 126us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member 		[3],[5]  
Gross Unrealized Gain (Loss) 1us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member 		[3],[5] 1us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member 		[3],[5]  
Estimated fair value 93us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member 		[3],[5] 127us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member 		[3],[5]  
Significant other observable inputs (Level 2) | Debt mutual funds      
Schedule of Available-for-sale Securities      
Cost 75us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_FixedIncomeFundsMember 		99us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_FixedIncomeFundsMember 		[3],[5]  
Gross Unrealized Gain (Loss) 1us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_FixedIncomeFundsMember 		2us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_FixedIncomeFundsMember 		[3],[5]  
Estimated fair value 76us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_FixedIncomeFundsMember 		101us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_FixedIncomeFundsMember 		[3],[5]  
Significant other observable inputs (Level 2) | Equity Funds      
Schedule of Available-for-sale Securities      
Cost 9us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquityFundsMember 		   
Estimated fair value 9us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquityFundsMember 		   
Significant other observable inputs (Level 2) | Bank debentures      
Schedule of Available-for-sale Securities      
Cost 6us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= cmi_BankDebenturesMember 		2us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= cmi_BankDebenturesMember 		[3],[5]  
Estimated fair value 6us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= cmi_BankDebenturesMember 		2us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= cmi_BankDebenturesMember 		[3],[5]  
Significant other observable inputs (Level 2) | Certificates of deposit      
Schedule of Available-for-sale Securities      
Cost   22us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CertificatesOfDepositMember 		[3],[5]  
Estimated fair value   22us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CertificatesOfDepositMember 		[3],[5]  
Significant other observable inputs (Level 2) | Government debt securities-non-U.S.      
Schedule of Available-for-sale Securities      
Cost 2us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember 		3us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember 		[3],[5]  
Gross Unrealized Gain (Loss)   (1)us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTax
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember 		[3],[5]  
Estimated fair value $ 2us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember 		$ 2us-gaap_AvailableForSaleSecurities
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_ForeignGovernmentDebtMember 		[3],[5]  
Minimum      
Schedule of Available-for-sale Securities      
Bank debentures and certificates of deposit period of maturity 6 months    
Maximum      
Schedule of Available-for-sale Securities      
Bank debentures and certificates of deposit period of maturity 5 years    
[1] Gross realized losses from the sale of available-for-sale securities were immaterial.
[2] The fair value of Level 1 securities is estimated primarily by referencing quoted prices in active markets for identical assets.
[3] We revised 2013 balances to classify $72 million as Level 2 assets instead of Level 1.
[4] In the first quarter of 2013, we realized a $9 million gain on the sale of equity securities.(4)
[5] The fair value of Level 2 securities is estimated primarily using actively quoted prices for similar instruments from brokers and observable inputs, including market transactions and third-party pricing services. We do not currently have any Level 3 securities, and there were no transfers between Level 2 or 3 during 2014 and 2013.