v2.4.0.8

Acquisitions (Detail) (USD $) In Millions, unless otherwise specified | 1 Months Ended |  | 1 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Apr. 30, 2013 Fianzas Monterrey [Member] | Apr. 02, 2013 Fianzas Monterrey [Member] | May 31, 2013 ABA Seguros [Member] | May 02, 2013 ABA Seguros [Member] | Jun. 17, 2014 The Siam Commercial Samaggi Insurance PCL [Member] | Apr. 28, 2014 The Siam Commercial Samaggi Insurance PCL [Member] | Oct. 31, 2014 Large Corporate P&C Business Of Itau Seguros [Member] Subsequent Event [Member]
Business Acquisition [Line Items] |  |  |  |  |  |  |
Acquisition purchase price | $ 293 |  | $ 690 |  |  |  |
Business Acquisition, Percentage of Voting Interests Acquired |  |  |  |  |  | 60.86% |
Business Combination, Step Acquisition, Equity Interest in Acquiree, Percentage |  |  |  |  | 32.17% |  |
Business Acquisition, Purchase Price Allocation, Goodwill Amount |  | 137 |  | 285 |  | 46 |
Business Acquisition, Purchase Price Allocation, Intangible Assets Other than Goodwill |  | 73 |  | 140 |  | 80 |
Business Acquisition, Cost of Acquired Entity, Expected Cash Consideration |  |  |  |  |  | $ 176 | $ 630
Business Combination Total Ownership Percentage |  |  |  |  | 93.03% |  |

X
- Definition Business Acquisition, Cost of Acquired Entity, Expected Cash Consideration + References No definition available. + Details
Name: | ace_BusinessAcquisitionCostOfAcquiredEntityExpectedCashConsideration
Namespace Prefix: | ace_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_BusinessAcquisitionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of voting equity interests acquired at the acquisition date in the business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463 + Details
Name: | us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of voting equity interests acquired in a business combination achieved in stages, including equity interests in the acquiree held by the acquirer immediately before the acquisition date and acquired at the acquisition date. + References No definition available. + Details
Name: | us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireeIncludingSubsequentAcquisitionPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of equity in the acquiree held by the acquirer immediately before the acquisition date in a business combination. + References No definition available. + Details
Name: | us-gaap_BusinessCombinationStepAcquisitionEquityInterestInAcquireePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266 + Details
Name: | us-gaap_Goodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16212-109274 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph ((a)(1),(b)) -URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275 + Details
Name: | us-gaap_IntangibleAssetsNetExcludingGoodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 + Details
Name: | us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration