v2.4.0.8

INVESTMENTS (DETAILS) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 11,687,387	$ 11,605,672
Gross Unrealized Gains (fixed maturities)	151,190	340,862
Gross Unrealized Losses (fixed maturities)	(193,665)	(18,485)
Fair Value (fixed maturities)	11,644,912	11,928,049
Non-credit OTTI in AOCI	(818)	(884)
Cost	546,531	608,306
Gross Unrealized Gains (equities)	80,614	65,640
Gross Unrealized Losses (equities)	(8,350)	(7,398)
Fair Value (equities)	618,795	666,548
US Government and Agency [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,369,338	1,413,520
Gross Unrealized Gains (fixed maturities)	1,944	9,484
Gross Unrealized Losses (fixed maturities)	(32,468)	(119)
Fair Value (fixed maturities)	1,338,814	1,422,885
Non-credit OTTI in AOCI	0	0
Non-US Government [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,212,124	1,076,501
Gross Unrealized Gains (fixed maturities)	7,444	30,276
Gross Unrealized Losses (fixed maturities)	(42,619)	(2,201)
Fair Value (fixed maturities)	1,176,949	1,104,576
Non-credit OTTI in AOCI	0	0
Corporate Debt [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	3,458,874	3,746,616
Gross Unrealized Gains (fixed maturities)	65,487	135,658
Gross Unrealized Losses (fixed maturities)	(44,445)	(5,892)
Fair Value (fixed maturities)	3,479,916	3,876,382
Non-credit OTTI in AOCI	0	0
Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	2,353,080	2,594,180
Gross Unrealized Gains (fixed maturities)	23,441	67,398
Gross Unrealized Losses (fixed maturities)	(42,897)	(1,670)
Fair Value (fixed maturities)	2,333,624	2,659,908
Non-credit OTTI in AOCI	0	0
CMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	769,422	814,211
Gross Unrealized Gains (fixed maturities)	11,964	25,999
Gross Unrealized Losses (fixed maturities)	(6,736)	(126)
Fair Value (fixed maturities)	774,650	840,084
Non-credit OTTI in AOCI	0	0
Non-Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	87,243	93,266
Gross Unrealized Gains (fixed maturities)	2,395	2,503
Gross Unrealized Losses (fixed maturities)	(772)	(570)
Fair Value (fixed maturities)	88,866	95,199
Non-credit OTTI in AOCI	(818)	(884)
ABS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	912,073	639,614
Gross Unrealized Gains (fixed maturities)	6,150	10,774
Gross Unrealized Losses (fixed maturities)	(6,542)	(7,182)
Fair Value (fixed maturities)	911,681	643,206
Non-credit OTTI in AOCI	0	0
Municipals [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,525,233	1,227,764
Gross Unrealized Gains (fixed maturities)	32,365	58,770
Gross Unrealized Losses (fixed maturities)	(17,186)	(725)
Fair Value (fixed maturities)	1,540,412	1,285,809
Non-credit OTTI in AOCI	0	0
Common Stock [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	334,809	398,975
Gross Unrealized Gains (equities)	63,721	51,821
Gross Unrealized Losses (equities)	(8,350)	(7,398)
Fair Value (equities)	390,180	443,398
Exchange-Traded Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	105,396	109,434
Gross Unrealized Gains (equities)	13,840	9,727
Gross Unrealized Losses (equities)	0	0
Fair Value (equities)	119,236	119,161
Non-U.S. Bond Mutual Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	106,326	99,897
Gross Unrealized Gains (equities)	3,053	4,092
Gross Unrealized Losses (equities)	0	0
Fair Value (equities)	$ 109,379	$ 103,989

X

- Definition

Accumulated other comprehensive loss related to portion of other than temporary impairment (OTTI) due to factors other than credit losses on debt securities categorized as available-for-sale that an entity does not intend to sell and which it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis of the debt security.

+ References

No definition available.

+ Details

Name:	axs_AccumulatedOtherComprehensiveIncomeLossOtherThanTemporaryImpairmentNotCreditLossAvailableForSaleDebtSecurities
Namespace Prefix:	axs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of accumulated pre-tax unrealized gain before deducting pre-tax unrealized loss on investments in available-for-sale debt securities impacting investments.

+ References

No definition available.

+ Details

Name:	axs_AvailableForSaleDebtSecuritiesGrossUnrealizedGainAccumulatedInInvestments
Namespace Prefix:	axs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of accumulated pre-tax unrealized loss before deducting pre-tax unrealized gain on investments in available-for-sale debt securities impacting investments.

+ References

No definition available.

+ Details

Name:	axs_AvailableForSaleDebtSecuritiesGrossUnrealizedLossAccumulatedInInvestments
Namespace Prefix:	axs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount of accumulated pre-tax unrealized gain before deducting pre-tax unrealized loss on investments in available-for-sale equity securities impacting investments.

+ References

No definition available.

+ Details

Name:	axs_AvailableForSaleEquitySecuritiesGrossUnrealizedGainAccumulatedInInvestments
Namespace Prefix:	axs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of accumulated pre-tax unrealized loss before deducting pre-tax unrealized gain on investments in available-for-sale equity securities impacting investments.

+ References

No definition available.

+ Details

Name:	axs_AvailableForSaleEquitySecuritiesGrossUnrealizedLossAccumulatedInInvestments
Namespace Prefix:	axs_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

This item represents the cost of equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments for other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

No definition available.

+ Details

Name:	us-gaap_AvailableForSaleEquitySecuritiesAmortizedCostBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of available-for-sale debt securities at cost, net of adjustments, which include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of debt securities categorized neither as held-to-maturity nor trading.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 2

-Subparagraph (b)-(g)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesDebtSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of equity securities categorized neither as held-to-maturity nor as trading.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26610-111562



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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesEquitySecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration