v2.4.0.6

RESERVE FOR LOSSES AND LOSS EXPENSES (DETAILS 4) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009
Additional Information Related to Net Incurred Losses [Line Items] |  |  |
Net favorable prior year reserve development | $ 257,461 | $ 313,055 | $ 423,172
Current year net incurred losses | 2,932,513 | 1,990,187 | 1,847,044
Short Tail Lines Insurance And Reinsurance Business [Member] |  |  |
Additional Information Related to Net Incurred Losses [Line Items] |  |  |
Percentage of net favorable prior year reserve development | 69.00% | 58.00% | 65.00%
Professional Lines Insurance And Reinsurance Business [Member] |  |  |
Additional Information Related to Net Incurred Losses [Line Items] |  |  |
Net favorable prior year reserve development | 105,000 | 117,000 | 143,000
Earthquake [Member] | New Zealand [Member] |  |  |
Additional Information Related to Net Incurred Losses [Line Items] |  |  |
Current year net incurred losses | 425,000 | 138,000 |
Earthquake [Member] | Japan [Member] |  |  |
Additional Information Related to Net Incurred Losses [Line Items] |  |  |
Current year net incurred losses | 222,000 |  |
Flood [Member] | Thailand [Member] |  |  |
Additional Information Related to Net Incurred Losses [Line Items] |  |  |
Current year net incurred losses | $ 66,000 |  |

X
- Definition Percentage of total provision in the period for claims incurred in prior reporting periods and related claims settlement costs. + References No definition available. + Details
Name: | axs_PercentageOfTotalLiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaimsPriorYears
Namespace Prefix: | axs_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Amount of provision in the period for claims incurred in the reporting period and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 94-5 -Paragraph 11 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 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_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaimsCurrentYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of provision in the period for claims incurred in prior reporting periods and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 94-5 -Paragraph 11 -Subparagraph 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 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_LiabilityForUnpaidClaimsAndClaimsAdjustmentExpenseIncurredClaimsPriorYears
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration