Assumed Life Reinsurance Programs Involving Minimum Benefit Guarantees Under Annuity Contracts (Income And Expenses Relating To GMDB And GLB Reinsurance) (Details) (USD $) In Millions	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Guaranteed Minimum Benefits [Line Items]
Net premiums earned	$ 4,490	$ 3,422	$ 11,556	$ 9,932
Policy benefits and other reserve adjustments	83	93	282	267
Total net realized gains (losses)	(760)	(50)	(878)	127
Guaranteed Minimum Death Benefits [Member]
Guaranteed Minimum Benefits [Line Items]
Net premiums earned	24	26	75	82
Policy benefits and other reserve adjustments	20	26	63	72
Guaranteed Minimum Income Benefit [Member]
Guaranteed Minimum Benefits [Line Items]
Net premiums earned	40	41	122	122
Policy benefits and other reserve adjustments	7	8	19	21
Total net realized gains (losses)	(952)	25	(969)	(180)
Gain (loss) recognized in income	(919)	58	(866)	(79)
Net cash received	40	40	121	120
Net (increase) decrease in liability	$ (959)	$ 18	$ (987)	$ (199)

Guaranteed Minimum Benefits total gain (loss) recognized in income

Name:	ace_GuaranteedMinimumBenefitsGainLossRecognizedInIncome
Namespace Prefix:	ace
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Guaranteed Minimum Benefits [Line Items]

+ Details

Name:	ace_GuaranteedMinimumBenefitsLineItems
Namespace Prefix:	ace
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Guaranteed Minimum Benefits net cash received (disbursed)

+ Details

Name:	ace_GuaranteedMinimumBenefitsNetCashReceivedDisbursed
Namespace Prefix:	ace
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The net realized gains or losses on investments, derivative instruments, and foreign exchange recognized during the period.

+ Details

Name:	ace_NetRealizedGainsLosses
Namespace Prefix:	ace
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Total net amount of increases and decreases to the liability for guaranteed minimum benefits on long-duration contracts occurring during the period, for all guaranteed benefit types.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 80

-Section 50

-Paragraph 1

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6484115&loc=d3e19393-158473

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 03-1

-Paragraph 38

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 03-1

-Section Appendix C

-Paragraph 46

-Subparagraph C-1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 20

-Section 55

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=6588021&loc=d3e7104-158389

+ Details

Name:	us-gaap_GuaranteedBenefitLiabilityGrossPeriodIncreaseDecrease
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Increases and decreases to the future policy benefit reserve based on changes in actuarial calculations, catastrophes, historical results and any other factors that influence the present value of future benefits to be paid to or on behalf of policyholders.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-LHI

-Chapter 9

-Paragraph 27, 28

-IssueDate 2006-05-01

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Financial Reporting Release (FRR)

-Number 403

-Paragraph 04

-Subparagraph b

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 40

-Section 50

-Paragraph 3

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437

+ Details

Name:	us-gaap_LiabilityForFuturePolicyBenefitsPeriodExpense
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Premiums earned on the income statement for all insurance and reinsurance contracts after subtracting any amounts ceded to another insurer and adding premiums assumed from other insurers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13(c))

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 1

-Article 7

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 113

-Paragraph 27

-Subparagraph a, b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.1)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

+ Details

Name:	us-gaap_PremiumsEarnedNet
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration