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Investments (Aggregate Fair Value And Gross Unrealized Loss By Length Of Time Security Has Continuously Been In Unrealized Loss Position) (Detail) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Investment [Line Items]    
Investment securities, Unrealized loss position, 0-12 Months, Fair Value $ 8,559us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue $ 18,228us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss (244)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2 (652)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
Investment securities, Unrealized loss position, Over 12 Months, Fair Value 3,932us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue 894us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss (79)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2 (63)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
Investment securities, Unrealized loss position, Total Fair Value 12,491us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue 19,122us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
Investment securities, Unrealized loss position, Total Gross Unrealized Loss (323)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2 (715)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
U.S. Treasury and agency    
Investment [Line Items]    
Investment securities, Unrealized loss position, 0-12 Months, Fair Value 350us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USTreasuryAndGovernmentMember
1,794us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USTreasuryAndGovernmentMember
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss (1)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USTreasuryAndGovernmentMember
(57)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USTreasuryAndGovernmentMember
Investment securities, Unrealized loss position, Over 12 Months, Fair Value 666us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USTreasuryAndGovernmentMember
31us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USTreasuryAndGovernmentMember
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss (9)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USTreasuryAndGovernmentMember
(6)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USTreasuryAndGovernmentMember
Investment securities, Unrealized loss position, Total Fair Value 1,016us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USTreasuryAndGovernmentMember
1,825us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USTreasuryAndGovernmentMember
Investment securities, Unrealized loss position, Total Gross Unrealized Loss (10)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USTreasuryAndGovernmentMember
(63)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USTreasuryAndGovernmentMember
Foreign    
Investment [Line Items]    
Investment securities, Unrealized loss position, 0-12 Months, Fair Value 2,262us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
4,621us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss (75)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
(114)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
Investment securities, Unrealized loss position, Over 12 Months, Fair Value 375us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
201us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss (15)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
(8)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
Investment securities, Unrealized loss position, Total Fair Value 2,637us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
4,822us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
Investment securities, Unrealized loss position, Total Gross Unrealized Loss (90)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
(122)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_ForeignGovernmentDebtSecuritiesMember
Corporate securities    
Investment [Line Items]    
Investment securities, Unrealized loss position, 0-12 Months, Fair Value 4,684us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
3,836us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss (150)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
(118)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
Investment securities, Unrealized loss position, Over 12 Months, Fair Value 738us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
194us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss (22)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
(14)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
Investment securities, Unrealized loss position, Total Fair Value 5,422us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
4,030us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
Investment securities, Unrealized loss position, Total Gross Unrealized Loss (172)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
(132)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_CorporateDebtSecuritiesMember
Mortgage backed-securities    
Investment [Line Items]    
Investment securities, Unrealized loss position, 0-12 Months, Fair Value 704us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_MortgageBackedSecuritiesMember
5,248us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_MortgageBackedSecuritiesMember
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss (2)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_MortgageBackedSecuritiesMember
(197)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_MortgageBackedSecuritiesMember
Investment securities, Unrealized loss position, Over 12 Months, Fair Value 1,663us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_MortgageBackedSecuritiesMember
384us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_MortgageBackedSecuritiesMember
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss (28)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_MortgageBackedSecuritiesMember
(31)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_MortgageBackedSecuritiesMember
Investment securities, Unrealized loss position, Total Fair Value 2,367us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_MortgageBackedSecuritiesMember
5,632us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_MortgageBackedSecuritiesMember
Investment securities, Unrealized loss position, Total Gross Unrealized Loss (30)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_MortgageBackedSecuritiesMember
(228)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_MortgageBackedSecuritiesMember
States, municipalities, and political subdivisions    
Investment [Line Items]    
Investment securities, Unrealized loss position, 0-12 Months, Fair Value 458us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
2,164us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss (3)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
(90)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Investment securities, Unrealized loss position, Over 12 Months, Fair Value 490us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
84us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss (5)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
(4)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Investment securities, Unrealized loss position, Total Fair Value 948us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
2,248us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Investment securities, Unrealized loss position, Total Gross Unrealized Loss (8)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
(94)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Total fixed maturities    
Investment [Line Items]    
Investment securities, Unrealized loss position, 0-12 Months, Fair Value 8,458us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_FixedMaturitiesMember
17,663us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_FixedMaturitiesMember
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss (231)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_FixedMaturitiesMember
(576)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_FixedMaturitiesMember
Investment securities, Unrealized loss position, Over 12 Months, Fair Value 3,932us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_FixedMaturitiesMember
894us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_FixedMaturitiesMember
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss (79)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_FixedMaturitiesMember
(63)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_FixedMaturitiesMember
Investment securities, Unrealized loss position, Total Fair Value 12,390us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_FixedMaturitiesMember
18,557us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_FixedMaturitiesMember
Investment securities, Unrealized loss position, Total Gross Unrealized Loss (310)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_FixedMaturitiesMember
(639)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_FixedMaturitiesMember
Equity securities    
Investment [Line Items]    
Investment securities, Unrealized loss position, 0-12 Months, Fair Value 101us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_EquitySecuritiesMember
498us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_EquitySecuritiesMember
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss (13)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_EquitySecuritiesMember
(67)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_EquitySecuritiesMember
Investment securities, Unrealized loss position, Over 12 Months, Fair Value 0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionTwelveMonthsOrLongerFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_EquitySecuritiesMember
 
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss 0ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_EquitySecuritiesMember
0ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_EquitySecuritiesMember
Investment securities, Unrealized loss position, Total Fair Value 101us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_EquitySecuritiesMember
498us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_EquitySecuritiesMember
Investment securities, Unrealized loss position, Total Gross Unrealized Loss (13)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_EquitySecuritiesMember
(67)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_EquitySecuritiesMember
Other investments    
Investment [Line Items]    
Investment securities, Unrealized loss position, 0-12 Months, Fair Value   67us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThanTwelveMonthsFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_OtherLongTermInvestmentsMember
Investment securities, Unrealized loss position, 0-12 Months, Gross Unrealized Loss   (9)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionLessthan12MonthsAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_OtherLongTermInvestmentsMember
Investment securities, Unrealized loss position, Over 12 Months, Gross Unrealized Loss   0ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPosition12MonthsorLongerAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_OtherLongTermInvestmentsMember
Investment securities, Unrealized loss position, Total Fair Value   67us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionFairValue
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_OtherLongTermInvestmentsMember
Investment securities, Unrealized loss position, Total Gross Unrealized Loss   $ (9)ace_AvailableforsaleSecuritiesContinuousUnrealizedLossPositionAggregateLoss2
/ ace_GrossUnrealizedLossSecurityTypeAxis
= us-gaap_OtherLongTermInvestmentsMember