This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities, the change in fair value of investment-related derivatives not designated as hedges and any hedge ineffectiveness recognized in earnings in relation to investment portfolio-related fair value hedges.

No definition available.

SEGMENT INFORMATION (DETAILS) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014 reportable_segment	Dec. 31, 2013	Dec. 31, 2012
Segment Information [Line Items]
Number of reportable segments									2us-gaap_NumberOfReportableSegments
Gross premiums written									$ 4,711,519us-gaap_PremiumsWrittenGross	$ 4,697,041us-gaap_PremiumsWrittenGross	$ 4,139,643us-gaap_PremiumsWrittenGross
Net premiums written									3,906,975us-gaap_PremiumsWrittenNet	3,928,200us-gaap_PremiumsWrittenNet	3,337,456us-gaap_PremiumsWrittenNet
Net premiums earned	958,517us-gaap_PremiumsEarnedNet	966,138us-gaap_PremiumsEarnedNet	1,000,400us-gaap_PremiumsEarnedNet	945,949us-gaap_PremiumsEarnedNet	941,911us-gaap_PremiumsEarnedNet	945,242us-gaap_PremiumsEarnedNet	945,873us-gaap_PremiumsEarnedNet	874,039us-gaap_PremiumsEarnedNet	3,870,999us-gaap_PremiumsEarnedNet	3,707,065us-gaap_PremiumsEarnedNet	3,415,463us-gaap_PremiumsEarnedNet
Other insurance related income (loss)									650us-gaap_OtherOperatingIncome	4,424us-gaap_OtherOperatingIncome	2,676us-gaap_OtherOperatingIncome
Net losses and loss expenses									(2,186,722)	(2,134,195)	(2,096,028)
Acquisition costs									(737,197)	(664,191)	(627,653)
General and administrative expenses									(621,876)	(575,390)	(560,981)
Underwriting income	112,720axs_UnderwritingIncomeLossNet	113,464axs_UnderwritingIncomeLossNet	126,581axs_UnderwritingIncomeLossNet	108,766axs_UnderwritingIncomeLossNet	94,159axs_UnderwritingIncomeLossNet	153,088axs_UnderwritingIncomeLossNet	9,921axs_UnderwritingIncomeLossNet	170,799axs_UnderwritingIncomeLossNet
Net investment income	78,595	66,562	114,867	82,744	113,863	103,429	83,112	108,908	342,766	409,312	380,957
Net realized investment gains	10,779	77,448	33,261	10,620	19,558	(4,708)	16,235	44,478	132,108	75,564	127,469
Foreign exchange (losses) gains									104,439	(26,143)	(29,512)
Interest expense and financing costs									(74,695)us-gaap_InterestExpense	(61,979)us-gaap_InterestExpense	(61,863)us-gaap_InterestExpense
Income before income taxes									830,472	734,467	550,528
Net loss and loss expense ratio									56.50%us-gaap_LossRatio	57.60%us-gaap_LossRatio	61.40%us-gaap_LossRatio
Acquisition cost ratio									19.00%us-gaap_AcquisitionCostRatio	17.90%us-gaap_AcquisitionCostRatio	18.40%us-gaap_AcquisitionCostRatio
General and administrative expense ratio									16.10%	15.50%	16.40%
Combined ratio									91.60%us-gaap_CombinedRatio	91.00%us-gaap_CombinedRatio	96.20%us-gaap_CombinedRatio
Goodwill and intangible assets	88,960				89,528				88,960	89,528	97,493
Insurance [Member]
Segment Information [Line Items]
Net premiums earned									1,830,544	1,722,762	1,558,058
Reinsurance [Member]
Segment Information [Line Items]
Net premiums earned									2,040,455	1,984,303	1,857,405
Operating Segments [Member]
Segment Information [Line Items]
Gross premiums written									4,711,519	4,697,041	4,139,643
Net premiums written									3,906,975	3,928,200	3,337,456
Net premiums earned									3,870,999	3,707,065	3,415,463
Other insurance related income (loss)									650	4,424	2,676
Net losses and loss expenses									(2,186,722)	(2,134,195)	(2,096,028)
Acquisition costs									(737,197)	(664,191)	(627,653)
General and administrative expenses									(486,201)	(485,134)	(431,321)
Underwriting income									461,529	427,969	263,137
Operating Segments [Member] \| Insurance [Member]
Segment Information [Line Items]
Gross premiums written									2,535,415	2,559,138	2,309,481
Net premiums written									1,779,501	1,813,538	1,522,245
Net premiums earned									1,830,544	1,722,762	1,558,058
Other insurance related income (loss)									(11)	2,436	2,676
Net losses and loss expenses									(1,131,880)	(1,050,402)	(953,564)
Acquisition costs									(278,804)	(242,363)	(226,859)
General and administrative expenses									(341,214)	(347,684)	(314,834)
Underwriting income									78,635	84,749	65,477
Net loss and loss expense ratio									61.80%	61.00%	61.20%
Acquisition cost ratio									15.20%	14.10%	14.60%
General and administrative expense ratio									18.70%	20.10%	20.20%
Combined ratio									95.70%	95.20%	96.00%
Goodwill and intangible assets	88,960				89,528				88,960	89,528	97,493
Operating Segments [Member] \| Reinsurance [Member]
Segment Information [Line Items]
Gross premiums written									2,176,104	2,137,903	1,830,162
Net premiums written									2,127,474	2,114,662	1,815,211
Net premiums earned									2,040,455	1,984,303	1,857,405
Other insurance related income (loss)									661	1,988	0
Net losses and loss expenses									(1,054,842)	(1,083,793)	(1,142,464)
Acquisition costs									(458,393)	(421,828)	(400,794)
General and administrative expenses									(144,987)	(137,450)	(116,487)
Underwriting income									382,894	343,220	197,660
Net loss and loss expense ratio									51.70%	54.60%	61.50%
Acquisition cost ratio									22.50%	21.30%	21.60%
General and administrative expense ratio									7.10%	6.90%	6.30%
Combined ratio									81.30%	82.80%	89.40%
Goodwill and intangible assets	0				0				0	0	0
Corporate, Non-Segment [Member]
Segment Information [Line Items]
General and administrative expenses									(135,675)	(90,256)	(129,660)
Significant Reconciling Items [Member]
Segment Information [Line Items]
Net investment income									342,766	409,312	380,957
Net realized investment gains									132,108	75,564	127,469
Foreign exchange (losses) gains									104,439	(26,143)	(29,512)
Interest expense and financing costs									$ (74,695)	$ (61,979)	$ (61,863)