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Acquisitions (Detail) (USD $)
In Millions, unless otherwise specified
0 Months Ended
Jun. 17, 2014
Apr. 28, 2014
Oct. 31, 2014
Apr. 01, 2015
The Siam Commercial Samaggi Insurance PCL [Member]        
Business Acquisition [Line Items]        
Business Combination, Step Acquisition, Equity Interest in Acquiree, Percentage 32.17%us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage
/ us-gaap_BusinessAcquisitionAxis
= ace_TheSiamCommercialSamaggiInsurancePCLMember
60.86%us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage
/ us-gaap_BusinessAcquisitionAxis
= ace_TheSiamCommercialSamaggiInsurancePCLMember
   
Business Acquisition, Purchase Price Allocation, Goodwill Amount   $ 46us-gaap_Goodwill
/ us-gaap_BusinessAcquisitionAxis
= ace_TheSiamCommercialSamaggiInsurancePCLMember
   
Business Acquisition, Purchase Price Allocation, Intangible Assets Other than Goodwill   80us-gaap_IntangibleAssetsNetExcludingGoodwill
/ us-gaap_BusinessAcquisitionAxis
= ace_TheSiamCommercialSamaggiInsurancePCLMember
   
Business Combination Total Ownership Percentage 93.03%us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeIncludingSubsequentAcquisitionPercentage
/ us-gaap_BusinessAcquisitionAxis
= ace_TheSiamCommercialSamaggiInsurancePCLMember
     
Business Combination, Consideration Transferred 176us-gaap_BusinessCombinationConsiderationTransferred1
/ us-gaap_BusinessAcquisitionAxis
= ace_TheSiamCommercialSamaggiInsurancePCLMember
     
Large Corporate P&C Business Of Itau Seguros [Member]        
Business Acquisition [Line Items]        
Business Acquisition, Purchase Price Allocation, Goodwill Amount     449us-gaap_Goodwill
/ us-gaap_BusinessAcquisitionAxis
= ace_LargeCorporatePropertyAndCasualtyBusinessOfItauSegurosMember
 
Business Acquisition, Purchase Price Allocation, Intangible Assets Other than Goodwill     60us-gaap_IntangibleAssetsNetExcludingGoodwill
/ us-gaap_BusinessAcquisitionAxis
= ace_LargeCorporatePropertyAndCasualtyBusinessOfItauSegurosMember
 
Business Acquisition, Cost of Acquired Entity, Expected Cash Consideration     610ace_BusinessAcquisitionCostOfAcquiredEntityExpectedCashConsideration
/ us-gaap_BusinessAcquisitionAxis
= ace_LargeCorporatePropertyAndCasualtyBusinessOfItauSegurosMember
 
Fireman's Fund high net worth personal lines [Member] | Subsequent Event [Member]        
Business Acquisition [Line Items]        
Business Acquisition, Cost of Acquired Entity, Expected Cash Consideration       $ 365ace_BusinessAcquisitionCostOfAcquiredEntityExpectedCashConsideration
/ us-gaap_BusinessAcquisitionAxis
= ace_FiremansFundhighnetworthpersonallinesMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember