Annual report pursuant to Section 13 and 15(d)

SHAREHOLDERS' EQUITY (Details 2)

v2.4.1.9
SHAREHOLDERS' EQUITY (Details 2) (USD $)
In Millions, except Per Share data, unless otherwise specified
 12 Months Ended 3 Months Ended
Dec. 31, 2014
Dec. 31, 2014
Sep. 28, 2014
Jun. 29, 2014
Mar. 30, 2014
Share repurchase program          
Shares acquired 4.8us-gaap_TreasuryStockSharesAcquired        
Average Cost Per Share (in dollars per share) $ 139.12us-gaap_TreasuryStockAcquiredAverageCostPerShare        
Total Cost of Repurchases $ 670cmi_StockRepurchaseProgramRepurchaseCost        
Remaining Authorized Capacity 174us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1 [1] 174us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1 [1]      
1 billion repurchase program 2012          
Share repurchase program          
Shares acquired   0.5us-gaap_TreasuryStockSharesAcquired
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		1.2us-gaap_TreasuryStockSharesAcquired
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		0.1us-gaap_TreasuryStockSharesAcquired
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		3.0us-gaap_TreasuryStockSharesAcquired
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member
Average Cost Per Share (in dollars per share)   $ 132.66us-gaap_TreasuryStockAcquiredAverageCostPerShare
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		$ 139.76us-gaap_TreasuryStockAcquiredAverageCostPerShare
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		$ 148.11us-gaap_TreasuryStockAcquiredAverageCostPerShare
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		$ 139.70us-gaap_TreasuryStockAcquiredAverageCostPerShare
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member
Total Cost of Repurchases   65cmi_StockRepurchaseProgramRepurchaseCost
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		175cmi_StockRepurchaseProgramRepurchaseCost
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		11cmi_StockRepurchaseProgramRepurchaseCost
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		419cmi_StockRepurchaseProgramRepurchaseCost
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member
Remaining Authorized Capacity $ 174us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		[1] $ 174us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		[1] $ 240us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		[1] $ 415us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		[1] $ 425us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
/ us-gaap_ShareRepurchaseProgramAxis
= cmi_ShareRepurchaseProgram2012Member 		[1]
[1] The remaining authorized capacity is calculated based on the cost to purchase the shares, but excludes commission expenses according to the Board of Directors authorization.