AXIS Capital Holdings Limited (AXS) 10-Q 4 May 15 2015 Q1 Quarterly report Financial data

DOCUMENT_AND_ENTITY_INFORMATIO

DOCUMENT AND ENTITY INFORMATION	3 Months Ended
	Mar. 31, 2015	Apr. 24, 2015
DOCUMENT AND ENTITY INFORMATION [ABSTRACT]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Entity Registrant Name	AXIS CAPITAL HOLDINGS LTD
Entity Central Index Key	1214816
Current Fiscal Year End Date	-19
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		100,928,728

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Assets
Fixed maturities, available for sale, at fair value (Amortized cost 2015: $12,012,633; 2014: $12,185,973)	$12,012,894	$12,129,273
Equity securities, available for sale, at fair value (Cost 2015: $572,317; 2014: $531,648)	601,329	567,707
Other investments, at fair value	939,006	965,465
Short-term investments, at fair value and amortized cost	38,373	107,534
Total investments	13,591,602	13,769,979
Cash and cash equivalents	996,596	921,830
Restricted cash and cash equivalents	273,496	287,865
Accrued interest receivable	79,706	83,070
Insurance and reinsurance premium balances receivable	2,241,875	1,808,620
Reinsurance recoverable on unpaid and paid losses	1,921,311	1,926,145
Deferred acquisition costs	616,966	466,987
Prepaid reinsurance premiums	357,042	351,441
Receivable for investments sold	13,432	169
Goodwill and intangible assets	88,508	88,960
Other assets	278,285	250,670
Total assets	20,458,819	19,955,736
Liabilities
Reserve for losses and loss expenses	9,443,222	9,596,797
Unearned premiums	3,293,952	2,735,376
Insurance and reinsurance balances payable	266,789	249,186
Senior notes	991,045	990,790
Payable for investments purchased	196,526	188,176
Other liabilities	221,050	315,471
Total liabilities	14,412,584	14,075,796
Shareholders’ equity
Preferred shares	627,843	627,843
Common shares (2015: 176,190; 2014: 175,478 shares issued and 2015: 100,219; 2014: 99,426 shares outstanding)	2,200	2,191
Additional paid-in capital	2,287,065	2,285,016
Accumulated other comprehensive loss	-17,070	-45,574
Retained earnings	5,842,239	5,715,504
Treasury shares, at cost (2015: 75,971; 2014: 76,052 shares)	-2,765,114	-2,763,859
Total shareholders’ equity attributable to AXIS Capital	5,977,163	5,821,121
Noncontrolling interests	69,072	58,819
Total shareholders’ equity	6,046,235	5,879,940
Total liabilities and shareholders’ equity	$20,458,819	$19,955,736

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Statement of Financial Position [Abstract]
Fixed maturities, available for sale, amortized cost	$12,012,633	$12,185,973
Equity securities, available for sale, cost	572,317	531,648
Short term investments, amortized cost	$38,373	$107,534
Common shares, shares issued	176,190	175,478
Common shares, shares outstanding	100,219	99,426
Treasury shares, shares	75,971	76,052

CONSOLIDATED_STATEMENTS_OF_OPE

CONSOLIDATED STATEMENTS OF OPERATIONS (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenues
Net premiums earned	$906,222	$945,949
Net investment income	92,110	82,744
Other insurance related income	7,676	3,082
Net realized investment gains (losses):
Other-than-temporary impairment (OTTI) losses	-17,568	-786
Other realized investment gains (losses)	-24,985	11,406
Total net realized investment gains (losses)	-42,553	10,620
Total revenues	963,455	1,042,395
Expenses
Net losses and loss expenses	518,937	544,207
Acquisition costs	171,702	172,036
General and administrative expenses	163,517	152,729
Foreign exchange losses (gains)	-63,220	4,233
Interest expense and financing costs	12,257	16,594
Total expenses	803,193	889,799
Income before income taxes	160,262	152,596
Income tax expense (benefit)	-690	4,125
Net income	160,952	148,471
Amounts attributable to (from) noncontrolling interests	-4,873	1,222
Net income attributable to AXIS Capital	165,825	147,249
Preferred share dividends	10,022	10,022
Net income available to common shareholders	$155,803	$137,227
Net income per common share:
Basic net income	$1.56	$1.26
Diluted net income	$1.54	$1.24
Weighted average number of common shares outstanding - basic	99,910	109,053
Weighted average number of common shares outstanding - diluted	101,139	110,391
Cash dividends declared per common share	$0.29	$0.27

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$160,952	$148,471
Other comprehensive income, net of tax:
Unrealized gains (losses) arising during the period	-5,187	71,383
Adjustment for reclassification of net realized investment gains (losses) and OTTI losses recognized in net income	45,104	-9,613
Unrealized gains arising during the period, net of reclassification adjustment	39,917	61,770
Foreign currency translation adjustment	-13,278	2,659
Total other comprehensive income, net of tax	26,639	64,429
Comprehensive income	187,591	212,900
Amounts attributable (to) from noncontrolling interests	6,738	-1,222
Comprehensive income attributable to AXIS Capital	$194,329	$211,678

CONSOLIDATED_STATEMENTS_OF_CHA

CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY (USD $)	Total	Parent [Member]	Preferred shares [Member]	Common shares (par value) [Member]	Additional paid-in capital [Member]	Unrealized gains (losses) on available for sale investments, net of tax [Member]	Cumulative foreign currency translation adjustments, net of tax [Member]	Accumulated other comprehensive income [Member]	Retained earnings [Member]	Treasury shares, at cost [Member]	Noncontrolling interest [Member]
In Thousands, unless otherwise specified
Total shareholders' equity at Dec. 31, 2013			$627,843	$2,174	$2,240,125	$124,945	($7,120)	$117,825	$5,062,706	($2,232,711)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued				14	1,861
Cost of treasury shares reissued					-8,128					8,128
Stock options exercised					392
Share-based compensation expense					12,852
Unrealized gains arising during the period, net of reclassification adjustment	61,770					61,770
Non-credit portion of OTTI losses	0					0
Foreign currency translation adjustments	2,659						2,659
Amounts attributable from noncontrolling interests	0						0
Net income	148,471								148,471
Amounts attributable (to) from noncontrolling interests	-1,222								-1,222
Preferred share dividends									-10,022
Common share dividends									-28,985
Shares repurchased for treasury										-178,703
Total shareholders' equity at Mar. 31, 2014	5,878,271	5,827,049	627,843	2,188	2,247,102	186,715	-4,461	182,254	5,170,948	-2,403,286	51,222
Total shareholders' equity at Dec. 31, 2014	5,879,940		627,843	2,191	2,285,016	-28,192	-17,382	-45,574	5,715,504	-2,763,859
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued				9	2,294
Cost of treasury shares reissued					-13,517					13,517
Stock options exercised					560
Share-based compensation expense					12,712
Unrealized gains arising during the period, net of reclassification adjustment	39,917					39,917
Non-credit portion of OTTI losses	0					0
Foreign currency translation adjustments	-13,278						-13,278
Amounts attributable from noncontrolling interests	1,865						1,865
Net income	160,952								160,952
Amounts attributable (to) from noncontrolling interests	4,873								4,873
Preferred share dividends									-10,022
Common share dividends									-29,068
Shares repurchased for treasury										-14,772
Total shareholders' equity at Mar. 31, 2015	$6,046,235	$5,977,163	$627,843	$2,200	$2,287,065	$11,725	($28,795)	($17,070)	$5,842,239	($2,765,114)	$69,072

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net income	$160,952	$148,471
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Net realized investment losses (gains)	42,553	-10,620
Net realized and unrealized gains on other investments	-30,935	-16,759
Amortization of fixed maturities	31,372	30,919
Other amortization and depreciation	6,581	15,889
Share-based compensation expense, net of cash payments	4,834	8,700
Changes in:
Accrued interest receivable	3,101	7,626
Reinsurance recoverable balances	-10,133	18,305
Deferred acquisition costs	-149,947	-178,170
Prepaid reinsurance premiums	-6,926	31,308
Reserve for loss and loss expenses	-127,224	85,312
Unearned premiums	559,479	685,778
Insurance and reinsurance balances, net	-415,909	-630,861
Other items	-95,778	-44,630
Net cash provided by (used in) operating activities	-27,980	151,268
Cash flows from investing activities:
Fixed maturities	-3,036,497	-3,298,375
Equity securities	-41,239	-73,197
Other investments	-21,418	-19,850
Short-term investments	-14,513	-420,115
Proceeds from the sale of:
Fixed maturities	2,823,044	3,092,006
Equity securities	522	73,694
Other investments	78,812	76,657
Short-term investments	79,657	154,603
Proceeds from redemption of fixed maturities	280,864	279,815
Proceeds from redemption of short-term investments	4,632	14,548
Purchase of other assets	-4,647	-19,152
Change in restricted cash and cash equivalents	14,369	-24,405
Net cash provided by (used in) investing activities	163,586	-163,771
Cash flows from financing activities:
Sales of shares to noncontrolling interests	56,991	0
Return of capital to noncontrolling interests	-40,000	0
Dividends paid - common shares	-30,103	-29,562
Repurchase of common shares	-22,581	-162,536
Dividends paid - preferred shares	-10,022	-10,022
Proceeds from issuance of common shares	2,863	2,266
Net proceeds from issuance of senior notes	0	494,344
Net cash provided by (used in) financing activities	-42,852	294,490
Effect of exchange rate changes on foreign currency cash and cash equivalents	-17,988	441
Increase in cash and cash equivalents	74,766	282,428
Cash and cash equivalents - beginning of period	921,830	923,326
Cash and cash equivalents - end of period	$996,596	$1,205,754

BASIS_OF_PRESENTATION_AND_ACCO

BASIS OF PRESENTATION AND ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
BASIS OF PRESENTATION AND ACCOUNTING POLICIES	Basis of Presentation
	These interim consolidated financial statements include the accounts of AXIS Capital Holdings Limited (“AXIS Capital”) and its subsidiaries (herein referred to as “we,” “us,” “our,” or the “Company”).
	The consolidated balance sheet at March 31, 2015 and the consolidated statements of operations, comprehensive income, shareholders' equity and cash flows for the periods ended March 31, 2015 and 2014 have not been audited. The balance sheet at December 31, 2014 is derived from our audited financial statements.
	These financial statements have been prepared in accordance with U.S. Generally Accepted Accounting Principles (“U.S. GAAP”) for interim financial information and with the Securities and Exchange Commission's (“SEC”) instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the opinion of management, these financial statements reflect all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation of our financial position and results of operations for the periods presented. The results of operations for any interim period are not necessarily indicative of the results for a full year. All inter-company accounts and transactions have been eliminated.
	The following information should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2014. Tabular dollar and share amounts are in thousands, except per share amounts. All amounts are reported in U.S. dollars.
	Significant Accounting Policies
	There were no notable changes in our significant accounting policies subsequent to our Annual Report on Form 10-K for the year ended December 31, 2014.

SEGMENT_INFORMATION

SEGMENT INFORMATION	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
SEGMENT INFORMATION	Our underwriting operations are organized around our global underwriting platforms, AXIS Insurance and AXIS Re. Therefore we have determined that we have two reportable segments, insurance and reinsurance. We do not allocate our assets by segment, with the exception of goodwill and intangible assets, as we evaluate the underwriting results of each segment separately from the results of our investment portfolio.
	The following tables summarize the underwriting results of our reportable segments, as well as the carrying values of allocated goodwill and intangible assets:
			2015									2014
		Three months ended and at March 31,	Insurance			Reinsurance			Total			Insurance			Reinsurance			Total
		Gross premiums written	$	602,724		$	1,076,208		$	1,678,932		$	601,721		$	1,219,678		$	1,821,399
		Net premiums written	436,740			1,026,812			1,463,552			456,692			1,207,892			1,664,584
		Net premiums earned	447,467			458,755			906,222			449,214			496,735			945,949
		Other insurance related income	—			7,676			7,676			—			3,082			3,082
		Net losses and loss expenses	(285,773		)	(233,164		)	(518,937		)	(279,423		)	(264,784		)	(544,207		)
		Acquisition costs	(64,455		)	(107,247		)	(171,702		)	(65,057		)	(106,979		)	(172,036		)
		General and administrative expenses	(87,689		)	(39,656		)	(127,345		)	(87,946		)	(36,076		)	(124,022		)
		Underwriting income	$	9,550		$	86,364		95,914			$	16,788		$	91,978		108,766
		Corporate expenses							(36,172		)							(28,707		)
		Net investment income							92,110									82,744
		Net realized investment gains (losses)							(42,553		)							10,620
		Foreign exchange (losses) gains							63,220									(4,233		)
		Interest expense and financing costs							(12,257		)							(16,594		)
		Income before income taxes							$	160,262								$	152,596
		Net loss and loss expense ratio	63.9		%	50.8		%	57.3		%	62.2		%	53.3		%	57.5		%
		Acquisition cost ratio	14.4		%	23.4		%	18.9		%	14.5		%	21.5		%	18.2		%
		General and administrative expense ratio	19.6		%	8.6		%	18.1		%	19.6		%	7.3		%	16.2		%
		Combined ratio	97.9		%	82.8		%	94.3		%	96.3		%	82.1		%	91.9		%
		Goodwill and intangible assets	$	88,508		$	—		$	88,508		$	90,350		$	—		$	90,350

INVESTMENTS

INVESTMENTS	3 Months Ended
	Mar. 31, 2015
Investments, Debt and Equity Securities [Abstract]
INVESTMENTS	a)     Fixed Maturities and Equities
	The amortized cost or cost and fair values of our fixed maturities and equities were as follows:
			Amortized			Gross				Gross			Fair			Non-credit
			Cost or			Unrealized				Unrealized			Value			OTTI
			Cost			Gains				Losses						in AOCI(5)
		At March 31, 2015
		Fixed maturities
		U.S. government and agency	$	1,490,502		$	9,183			$	(5,528	)	$	1,494,157		$	—
		Non-U.S. government	932,741			7,041				(66,685		)	873,097			—
		Corporate debt	4,549,974			58,133				(73,829		)	4,534,278			—
		Agency RMBS(1)	2,150,598			51,061				(1,416		)	2,200,243			—
		CMBS(2)	1,111,327			21,219				(1,223		)	1,131,323			—
		Non-Agency RMBS	77,185			2,560				(1,744		)	78,001			(865		)
		ABS(3)	1,500,493			3,438				(8,102		)	1,495,829			—
		Municipals(4)	199,813			6,649				(496		)	205,966			—
		Total fixed maturities	$	12,012,633		$	159,284			$	(159,023	)	$	12,012,894		$	(865	)
		Equity securities
		Exchange-traded funds	453,978			46,224				(2,155		)	498,047
		Non-U.S. bond mutual funds	118,339			—				(15,057		)	103,282
		Total equity securities	$	572,317		$	46,224			$	(17,212	)	$	601,329
		At December 31, 2014
		Fixed maturities
		U.S. government and agency	$	1,645,068		$	3,337			$	(28,328	)	$	1,620,077		$	—
		Non-U.S. government	1,080,601			7,383				(54,441		)	1,033,543			—
		Corporate debt	4,386,432			40,972				(66,280		)	4,361,124			—
		Agency RMBS(1)	2,241,581			40,762				(4,235		)	2,278,108			—
		CMBS(2)	1,085,618			13,289				(2,019		)	1,096,888			—
		Non-Agency RMBS	71,236			2,765				(915		)	73,086			(889		)
		ABS(3)	1,475,026			2,748				(16,188		)	1,461,586			—
		Municipals(4)	200,411			5,282				(832		)	204,861			—
		Total fixed maturities	$	12,185,973		$	116,538			$	(173,238	)	$	12,129,273		$	(889	)
		Equity securities
		Exchange-traded funds	416,063			43,583				(4,756		)	454,890
		Non-U.S. bond mutual funds	115,585			—				(2,768		)	112,817
		Total equity securities	$	531,648		$	43,583			$	(7,524	)	$	567,707
	-1	Residential mortgage-backed securities (RMBS) originated by U.S. agencies.
	-2	Commercial mortgage-backed securities (CMBS).
	-3	Asset-backed securities (ABS) include debt tranched securities collateralized primarily by auto loans, student loans, credit cards, and other asset types. This asset class also includes collateralized loan obligations (CLOs) and collateralized debt obligations (CDOs).
	-4	Municipals include bonds issued by states, municipalities and political subdivisions.
	-5	Represents the non-credit component of the other-than-temporary impairment (OTTI) losses, adjusted for subsequent sales of securities. It does not include the change in fair value subsequent to the impairment measurement date.
	In the normal course of investing activities, we actively manage allocations to non-controlling tranches of structured securities (variable interests) issued by VIEs. These structured securities include RMBS, CMBS and ABS and are included in the above table. Additionally, within our other investments portfolio, we also invest in limited partnerships (hedge funds) and CLO equity tranched securities, which are all variable interests issued by VIEs (see Note 3(b)). For these variable interests, we do not have the power to direct the activities that are most significant to the economic performance of the VIEs and accordingly we are not the primary beneficiary for any of these VIEs. Our maximum exposure to loss on these interests is limited to the amount of our investment. We have not provided financial or other support with respect to these structured securities other than our original investment.
	Contractual Maturities
	The contractual maturities of fixed maturities are shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.
			Amortized			Fair				% of Total
			Cost			Value				Fair Value
		At March 31, 2015
		Maturity
		Due in one year or less	$	508,448		$	503,179			4.2	%
		Due after one year through five years	4,387,194			4,349,800				36.2	%
		Due after five years through ten years	2,042,045			2,016,713				16.8	%
		Due after ten years	235,343			237,806				2	%
			7,173,030			7,107,498				59.2	%
		Agency RMBS	2,150,598			2,200,243				18.3	%
		CMBS	1,111,327			1,131,323				9.4	%
		Non-Agency RMBS	77,185			78,001				0.6	%
		ABS	1,500,493			1,495,829				12.5	%
		Total	$	12,012,633		$	12,012,894			100	%
		At December 31, 2014
		Maturity
		Due in one year or less	$	424,077		$	423,265			3.5	%
		Due after one year through five years	4,925,780			4,892,411				40.3	%
		Due after five years through ten years	1,755,248			1,695,641				14	%
		Due after ten years	207,407			208,288				1.7	%
			7,312,512			7,219,605				59.5	%
	Agency RMBS	2,241,581			2,278,108				18.8	%
	CMBS	1,085,618			1,096,888				9	%
	Non-Agency RMBS	71,236			73,086				0.6	%
	ABS	1,475,026			1,461,586				12.1	%
	Total	$	12,185,973		$	12,129,273			100	%
Gross Unrealized Losses
The following table summarizes fixed maturities and equities in an unrealized loss position and the aggregate fair value and gross unrealized loss by length of time the security has continuously been in an unrealized loss position:
		12 months or greater							Less than 12 months						Total
		Fair			Unrealized				Fair			Unrealized			Fair			Unrealized
		Value			Losses				Value			Losses			Value			Losses
	At March 31, 2015
	Fixed maturities
	U.S. government and agency	$	94,248		$	(4,525	)		$	329,487		$	(1,003	)	$	423,735		$	(5,528	)
	Non-U.S. government	112,581			(31,924		)		349,284			(34,761		)	461,865			(66,685		)
	Corporate debt	53,901			(5,679		)		1,263,181			(68,150		)	1,317,082			(73,829		)
	Agency RMBS	55,492			(748		)		208,699			(668		)	264,191			(1,416		)
	CMBS	54,293			(719		)		145,716			(504		)	200,009			(1,223		)
	Non-Agency RMBS	5,685			(762		)		17,917			(982		)	23,602			(1,744		)
	ABS	449,335			(6,367		)		544,239			(1,735		)	993,574			(8,102		)
	Municipals	14,528			(139		)		16,297			(357		)	30,825			(496		)
	Total fixed maturities	$	840,063		$	(50,863	)		$	2,874,820		$	(108,160	)	$	3,714,883		$	(159,023	)
	Equity securities
	Exchange-traded funds	—			—				80,230			(2,155		)	80,230			(2,155		)
	Non-U.S. bond mutual funds	—			—				103,282			(15,057		)	103,282			(15,057		)
	Total equity securities	$	—		$	—			$	183,512		$	(17,212	)	$	183,512		$	(17,212	)
	At December 31, 2014
	Fixed maturities
	U.S. government and agency	$	388,551		$	(24,319	)		$	786,850		$	(4,009	)	$	1,175,401		$	(28,328	)
	Non-U.S. government	143,602			(29,171		)		435,670			(25,270		)	579,272			(54,441		)
	Corporate debt	26,708			(2,221		)		2,199,672			(64,059		)	2,226,380			(66,280		)
	Agency RMBS	259,914			(3,084		)		333,288			(1,151		)	593,202			(4,235		)
	CMBS	68,624			(925		)		256,225			(1,094		)	324,849			(2,019		)
	Non-Agency RMBS	6,689			(613		)		13,442			(302		)	20,131			(915		)
	ABS	425,663			(10,325		)		750,679			(5,863		)	1,176,342			(16,188		)
	Municipals	34,462			(644		)		25,284			(188		)	59,746			(832		)
	Total fixed maturities	$	1,354,213		$	(71,302	)		$	4,801,110		$	(101,936	)	$	6,155,323		$	(173,238	)
	Equity securities
	Exchange-traded funds	—			—				91,275			(4,756		)	91,275			(4,756		)
	Non-U.S. bond mutual funds	—			—				112,817			(2,768		)	112,817			(2,768		)
	Total equity securities	$	—		$	—			$	204,092		$	(7,524	)	$	204,092		$	(7,524	)
Fixed Maturities
At March 31, 2015, 1,004 fixed maturities (2014: 1,388) were in an unrealized loss position of $159 million (2014: $173 million), of which $17 million (2014: $36 million) was related to securities below investment grade or not rated.
At March 31, 2015, 180 (2014: 223) securities had been in a continuous unrealized loss position for 12 months or greater and had a fair value of $840 million (2014: $1,354 million). Following our credit impairment review, we concluded that these securities as well as the remaining securities in an unrealized loss position in the above table were temporarily impaired at March 31, 2015, and were expected to recover in value as the securities approach maturity. Further, at March 31, 2015, we did not intend to sell these securities in an unrealized loss position and it is more likely than not that we will not be required to sell these securities before the anticipated recovery of their amortized costs.
Equity Securities
At March 31, 2015, 8 securities (2014: 9) were in an unrealized loss position of $17 million (2014: $8 million).
At March 31, 2015 and December 31, 2014, there were no securities that had been in a continuous unrealized loss position for 12 months or greater. Based on our impairment review process and our ability and intent to hold these securities for a reasonable period of time sufficient for a full recovery, we concluded that the above equities in an unrealized loss position were temporarily impaired at March 31, 2015.
b) Other Investments
The following table provides a breakdown of our investments in hedge funds, direct lending funds and CLO Equities, together with additional information relating to the liquidity of each category:
		Fair Value						Redemption Frequency		Redemption
								(if currently eligible)		Notice Period
	At March 31, 2015
	Long/short equity funds	$	242,096		26	%		Quarterly, Semi-annually		30-60 days
	Multi-strategy funds	336,342			36	%		Quarterly, Semi-annually		60-95 days
	Event-driven funds	189,212			20	%		Quarterly, Annually		45-60 days
	Leveraged bank loan funds	9,616			1	%		Quarterly		65 days
	Direct lending funds	69,682			7	%		n/a		n/a
	CLO - Equities	92,058			10	%		n/a		n/a
	Total other investments	$	939,006		100	%
	At December 31, 2014
	Long/short equity funds	$	298,907		31	%		Quarterly, Semi-annually		30-60 days
	Multi-strategy funds	324,020			34	%		Quarterly, Semi-annually		60-95 days
	Event-driven funds	185,899			19	%		Quarterly, Annually		45-60 days
	Leveraged bank loan funds	9,713			1	%		Quarterly		65 days
	Direct lending funds	54,438			6	%		n/a		n/a
	CLO - Equities	92,488			9	%		n/a		n/a
	Total other investments	$	965,465		100	%
n/a - not applicable
The investment strategies for the above funds are as follows:
•	Long/short equity funds: Seek to achieve attractive returns primarily by executing an equity trading strategy involving both long and short investments in publicly-traded equities.
•	Multi-strategy funds: Seek to achieve above-market returns by pursuing multiple investment strategies to diversify risks and reduce volatility. This category includes funds of hedge funds which invest in a large pool of hedge funds across a diversified range of hedge fund strategies.
•	Event-driven funds: Seek to achieve attractive returns by exploiting situations where announced or anticipated events create opportunities.
•	Leveraged bank loan funds: Seek to achieve attractive returns by investing primarily in bank loan collateral that has limited interest rate risk exposure.
•	Direct lending funds: Seek to achieve attractive risk-adjusted returns, including current income generation, by investing in funds which provide financing directly to borrowers.
Two common redemption restrictions which may impact our ability to redeem our hedge funds are gates and lockups. A gate is a suspension of redemptions which may be implemented by the general partner or investment manager of the fund in order to defer, in whole or in part, the redemption request in the event the aggregate amount of redemption requests exceeds a predetermined percentage of the fund's net assets which may otherwise hinder the general partner or investment manager's ability to liquidate holdings in an orderly fashion in order to generate the cash necessary to fund extraordinarily large redemption payouts. A lockup period is the initial amount of time an investor is contractually required to hold the security before having the ability to redeem. During 2015 and 2014, neither of these restrictions impacted our redemption requests. At March 31, 2015, $95 million (2014: $87 million), representing 12% (2014: 11%) of our total hedge funds, relate to holdings where we are still within the lockup period. The expiration of these lockup periods range from June 2015 to March 2016.
At March 31, 2015, $6 million (2014: $6 million) was invested in hedge funds that are not accepting redemption requests. Of this amount, substantially all relates to a leveraged bank loan fund in a period of planned principal distributions. Based on market conditions and payments made to date, management's current expectation is that the distribution process will be completed in 2015.
At March 31, 2015, we have $72 million (2014: $88 million) of unfunded commitments within our other investments portfolio relating to our future investments in direct lending funds. Once the full amount of committed capital has been called by the General Partner of each of these funds, the assets will not be fully returned until the completion of the fund's investment term. These funds have investment terms ranging from 5-10 years and the General Partners of certain funds have the option to extend the term by up to three years.
During 2013, we made a $60 million commitment as a limited partner in a multi-strategy hedge fund. Once the full amount of committed capital has been called by the General Partner, the assets will not be fully returned until the completion of the fund's investment term which ends in December, 2018. The General Partner then has the option to extend the term by up to three years. At March 31, 2015, $29 million of our commitment remains unfunded and the current fair value of the funds called to date are included in the multi-strategy funds line of the table above.
During 2015, we made a $100 million commitment as a limited partner in a fund which invests in real estate and real estate securities and businesses. The fund is subject to a 3 year commitment period and a total fund life of 8 years during which time we are not eligible to redeem our investment. At March 31, 2015 our commitment remains unfunded.
c) Net Investment Income
Net investment income was derived from the following sources:
		Three months ended March 31,
		2015			2014
	Fixed maturities	$	66,101		$	72,957
	Other investments	30,935			16,760
	Equity securities	1,676			2,286
	Cash and cash equivalents	1,102			863
	Short-term investments	69			214
	Gross investment income	99,883			93,080
	Investment expenses	(7,773		)	(10,336		)
	Net investment income	$	92,110		$	82,744
d) Net Realized Investment Gains (Losses)
The following table provides an analysis of net realized investment gains (losses):
		Three months ended March 31,
		2015			2014
	Gross realized gains
	Fixed maturities and short-term investments	$	15,661		$	33,770
	Equities	38			19,267
	Gross realized gains	15,699			53,037
	Gross realized losses
	Fixed maturities and short-term investments	(43,091		)	(33,704		)
	Equities	(124		)	(2,438		)
	Gross realized losses	(43,215		)	(36,142		)
	Net OTTI recognized in earnings	(17,568		)	(786		)
	Change in fair value of investment derivatives(1)	2,531			(5,489		)
	Net realized investment gains (losses)	$	(42,553	)	$	10,620
(1) Refer to Note 5 – Derivative Instruments
The following table summarizes the OTTI recognized in earnings by asset class:
		Three months ended March 31,
		2015			2014
	Fixed maturities:
	Non-U.S. government	$	1,422		$	38
	Corporate debt	16,120			15
	Non-Agency RMBS	4			—
	ABS	22			56
		17,568			109
	Equity Securities
	Common stocks	—			677
		—			677
	Total OTTI recognized in earnings	$	17,568		$	786
The following table provides a roll forward of the credit losses, before income taxes, for which a portion of the OTTI was recognized in AOCI:
		Three months ended March 31,
		2015			2014
	Balance at beginning of period	$	1,531		$	1,594
	Credit impairments recognized on securities not previously impaired	—			—
	Additional credit impairments recognized on securities previously impaired	10			—
	Change in timing of future cash flows on securities previously impaired	—			—
	Intent to sell of securities previously impaired	—			—
	Securities sold/redeemed/matured	—			(4		)
	Balance at end of period	$	1,541		$	1,590
e) Reverse Repurchase Agreements
At March 31, 2015, we held $123 million (2014: $110 million) of reverse repurchase agreements. These loans are fully collateralized, are generally outstanding for a short period of time and are presented on a gross basis as part of cash and cash equivalents on our consolidated balance sheet. The required collateral for these loans is either cash or U.S. Treasuries at a minimum rate of 102% of the loan principal. Upon maturity, we receive principal and interest income.

FAIR_VALUE_MEASUREMENTS

FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	Fair Value Hierarchy
	Fair value is defined as the price to sell an asset or transfer a liability (i.e. the “exit price”) in an orderly transaction between market participants. We use a fair value hierarchy that gives the highest priority to quoted prices in active markets and the lowest priority to unobservable data. The hierarchy is broken down into three levels as follows:
	•	Level 1 - Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that we have the ability to access.
	•	Level 2 - Valuations based on quoted prices in active markets for similar assets or liabilities, quoted prices for identical assets or liabilities in inactive markets, or for which significant inputs are observable (e.g. interest rates, yield curves, prepayment speeds, default rates, loss severities, etc.) or can be corroborated by observable market data.
	•	Level 3 - Valuations based on inputs that are unobservable and significant to the overall fair value measurement. The unobservable inputs reflect our own judgments about assumptions that market participants might use.
	The availability of observable inputs can vary from financial instrument to financial instrument and is affected by a wide variety of factors including, for example, the type of financial instrument, whether the financial instrument is new and not yet established in the marketplace, and other characteristics particular to the transaction. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires significantly more judgment.
	Accordingly, the degree of judgment exercised by management in determining fair value is greatest for instruments categorized in Level 3. In periods of market dislocation, the observability of prices and inputs may be reduced for many instruments. This may lead us to change the selection of our valuation technique (from market to cash flow approach) or may cause us to use multiple valuation techniques to estimate the fair value of a financial instrument. This circumstance could cause an instrument to be reclassified between levels within the fair value hierarchy.
	We used the following valuation techniques and assumptions in estimating the fair value of our financial instruments as well as the general classification of such financial instruments pursuant to the above fair value hierarchy.
	Fixed Maturities
	At each valuation date, we use the market approach valuation technique to estimate the fair value of our fixed maturities portfolio, when possible. This market approach includes, but is not limited to, prices obtained from third party pricing services for identical or comparable securities and the use of “pricing matrix models” using observable market inputs such as yield curves, credit risks and spreads, measures of volatility, and prepayment speeds. Pricing from third party pricing services is sourced from multiple vendors, when available, and we maintain a vendor hierarchy by asset type based on historical pricing experience and vendor expertise. When prices are unavailable from pricing services, we obtain non-binding quotes from broker-dealers who are active in the corresponding markets.
	The following describes the significant inputs generally used to determine the fair value of our fixed maturities by asset class.
	U.S. government and agency
	U.S. government and agency securities consist primarily of bonds issued by the U.S. Treasury and mortgage pass-through agencies such as the Federal National Mortgage Association, the Federal Home Loan Mortgage Corporation and the Government National Mortgage Association. As the fair values of our U.S. Treasury securities are based on unadjusted market prices in active markets, they are classified within Level 1. The fair values of U.S. government agency securities are priced using the spread above the risk-free yield curve. As the yields for the risk-free yield curve and the spreads for these securities are observable market inputs, the fair values of U.S. government agency securities are classified within Level 2.
	Non-U.S. government
	Non-U.S. government securities comprise bonds issued by non-U.S. governments and their agencies along with supranational organizations (collectively also known as sovereign debt securities). The fair value of these securities is based on prices obtained from international indices or a valuation model that includes the following inputs: interest rate yield curves, cross-currency basis index spreads, and country credit spreads for structures similar to the sovereign bond in terms of issuer, maturity and seniority. As the significant inputs are observable market inputs, the fair value of non-U.S. government securities are classified within Level 2.
	Corporate debt
	Corporate debt securities consist primarily of investment-grade debt of a wide variety of corporate issuers and industries. The fair values of these securities are generally determined using the spread above the risk-free yield curve. These spreads are generally obtained from the new issue market, secondary trading and broker-dealer quotes. As these spreads and the yields for the risk-free yield curve are observable market inputs, the fair values of our corporate debt securities are classified within Level 2. Where pricing is unavailable from pricing services, we obtain non-binding quotes from broker-dealers to estimate fair value. This is generally the case when there is a low volume of trading activity and current transactions are not orderly. In this event, securities are classified within Level 3.
	MBS
	Our portfolio of RMBS and CMBS are originated by both agencies and non-agencies. The fair values of these securities are determined through the use of a pricing model (including Option Adjusted Spread) which uses prepayment speeds and spreads to determine the appropriate average life of the MBS. These spreads are generally obtained from the new issue market, secondary trading and broker-dealer quotes. As the significant inputs used to price MBS are observable market inputs, the fair values of the MBS are classified within Level 2. Where pricing is unavailable from pricing services, we obtain non-binding quotes from broker-dealers to estimate fair value. This is generally the case when there is a low volume of trading activity and current transactions are not orderly. These securities are classified within Level 3.
	ABS
	ABS include mostly investment-grade bonds backed by pools of loans with a variety of underlying collateral, including automobile loan receivables, student loans, credit card receivables, and CLO Debt originated by a variety of financial institutions. Similarly to MBS, the fair values of ABS are priced through the use of a model which uses prepayment speeds and spreads sourced primarily from the new issue market. As the significant inputs used to price ABS are observable market inputs, the fair values of ABS are classified within Level 2. Where pricing is unavailable from pricing services, we obtain non-binding quotes from broker-dealers. These securities are classified within Level 3.
	Municipals
	Our municipal portfolio comprises revenue and general obligation bonds issued by U.S. domiciled state and municipal entities. The fair value of these securities is determined using spreads obtained from broker-dealers, trade prices and the new issue market. As the significant inputs used to price the municipals are observable market inputs, municipals are classified within Level 2.
	Equity Securities
	Equity securities include exchange-traded funds and non-U.S. bond mutual funds. For exchange-traded funds, we classified these within Level 1 as their fair values are based on unadjusted quoted market prices in active markets. Our investments in non-U.S. bond mutual funds have daily liquidity, with redemption based on the net asset value ("NAV") of the funds. Accordingly, we have classified these investments as Level 2.
	Other Investments
	As a practical expedient, we estimate fair values for hedge funds, direct lending funds and the CLO fund using NAVs as advised by external fund managers or third party administrators. For each of these funds, the NAV is based on the manager's or administrator's valuation of the underlying holdings in accordance with the fund's governing documents and in accordance with U.S. GAAP. For any funds for which we have not yet received a NAV concurrent with our period end date, we record an estimate of the change in fair value for the period subsequent to the most recent NAV. Such estimates are based on return estimates for the period between the most recently issued NAV and the period end date; these estimates are obtained from the relevant fund managers. Accordingly, we do not typically have a reporting lag in our fair value measurements for these funds. Historically, our valuation estimates incorporating these return estimates have not significantly diverged from the subsequent NAVs.
	Within the hedge fund, direct lending fund and CLO fund industries, there is a general lack of transparency necessary to facilitate a detailed independent assessment of the values placed on the securities underlying the NAV provided by the fund manager or fund administrator. To address this, on a quarterly basis, we perform a number of monitoring procedures designed to assist us in the assessment of the quality of the information provided by managers and administrators. These procedures include, but are not limited to, regular review and discussion of each fund's performance with its manager, regular evaluation of fund performance against applicable benchmarks and the backtesting of our fair value estimates against subsequently received NAVs. Backtesting involves comparing our previously reported values for each individual fund against NAVs per audited financial statements (for year-end values) and final NAVs from fund managers and fund administrators (for interim values).
	For our hedge fund investments with liquidity terms allowing us to fully redeem our holdings at the applicable NAV in the near term, we have classified these investments as Level 2. Certain investments in hedge funds, all of our direct lending funds and our CLO fund have redemption restrictions (see Note 3(b) for further details) that prevent us from redeeming in the near term and therefore we have classified these investments as Level 3.
	At March 31, 2015, our direct investments in CLO - Equities were classified within Level 3 as we estimated the fair value for these securities using an income approach valuation technique (discounted cash flow model) due to the lack of observable and relevant trades in the secondary markets.
	Short-Term Investments
	Short-term investments primarily comprise highly liquid securities with maturities greater than three months but less than one year from the date of purchase. These securities are classified within Level 2 because these securities are typically not actively traded due to their approaching maturity and, as such, their amortized cost approximates fair value.
	Derivative Instruments
	Our foreign currency forward contracts and interest rate swaps are customized to our economic hedging strategies and trade in the over-the-counter derivative market. We use the market approach valuation technique to estimate the fair value for these derivatives based on significant observable market inputs from third party pricing vendors, non-binding broker-dealer quotes and/or recent trading activity. Accordingly, we classified these derivatives within Level 2.
	We also participate in non-exchange traded derivative-based risk management products addressing weather risks. We use observable market inputs and unobservable inputs in combination with industry or internally-developed valuation and forecasting techniques to determine fair value. We classify these instruments within Level 3.
	Insurance-linked Securities
	Insurance-linked securities comprise investment in a catastrophe bond. We obtain non-binding quotes from broker-dealers to estimate fair value. This is generally the case when there is a low volume of trading activity and current transactions are not orderly. These securities are classified within Level 3.
	Cash Settled Awards
	Cash settled awards comprise restricted stock units that form part of our compensation program. Although the fair value of these awards is determined using observable quoted market prices in active markets, the stock units themselves are not actively traded. Accordingly, we have classified these liabilities within Level 2.
	The table below presents the financial instruments measured at fair value on a recurring basis:
			Quoted Prices in				Significant			Significant		Total Fair
			Active Markets for				Other Observable			Unobservable		Value
			Identical Assets				Inputs			Inputs
			(Level 1)				(Level 2)			(Level 3)
		At March 31, 2015
		Assets
		Fixed maturities
		U.S. government and agency	$	1,400,810			$	93,347		$	—	$	1,494,157
		Non-U.S. government	—				873,097			—		873,097
		Corporate debt	—				4,507,421			26,857		4,534,278
		Agency RMBS	—				2,200,243			—		2,200,243
		CMBS	—				1,114,262			17,061		1,131,323
		Non-Agency RMBS	—				78,001			—		78,001
		ABS	—				1,455,908			39,921		1,495,829
		Municipals	—				205,966			—		205,966
			1,400,810				10,528,245			83,839		12,012,894
		Equity securities
		Exchange-traded funds	498,047				—			—		498,047
		Non-U.S. bond mutual funds	—				103,282			—		103,282
			498,047				103,282			—		601,329
		Other investments
		Hedge funds	—				281,417			495,849		777,266
		Direct lending funds	—				—			69,682		69,682
		CLO - Equities	—				—			92,058		92,058
		—				281,417			657,589		939,006
	Short-term investments	—				38,373			—		38,373
	Derivative instruments (see Note 5)	—				4,250			—		4,250
	Insurance-linked securities	—				—			25,000		25,000
	Total Assets	$	1,898,857			$	10,955,567		$	766,428	$	13,620,852
	Liabilities
	Derivative instruments (see Note 5)	$	—			$	10,312		$	7,308	$	17,620
	Cash settled awards (see Note 7)	—				12,641			—		12,641
	Total Liabilities	$	—			$	22,953		$	7,308	$	30,261
	At December 31, 2014
	Assets
	Fixed maturities
	U.S. government and agency	$	1,497,922			$	122,155		$	—	$	1,620,077
	Non-U.S. government	—				1,033,543			—		1,033,543
	Corporate debt	—				4,345,287			15,837		4,361,124
	Agency RMBS	—				2,278,108			—		2,278,108
	CMBS	—				1,079,125			17,763		1,096,888
	Non-Agency RMBS	—				73,086			—		73,086
	ABS	—				1,421,555			40,031		1,461,586
	Municipals	—				204,861			—		204,861
		1,497,922				10,557,720			73,631		12,129,273
	Equity securities
	Exchange-traded funds	454,890				—			—		454,890
	Non-U.S. bond mutual funds	—				112,817			—		112,817
		454,890				112,817			—		567,707
	Other investments
	Hedge funds	—				347,621			470,918		818,539
	Direct lending funds	—				—			54,438		54,438
	CLO - Equities	—				—			92,488		92,488
		—				347,621			617,844		965,465
	Short-term investments	—				107,534			—		107,534
	Derivative instruments (see Note 5)	—				7,153			111		7,264
	Insurance-linked securities	—				—			—		—
	Total Assets	$	1,952,812			$	11,132,845		$	691,586	$	13,777,243
	Liabilities
	Derivative instruments (see Note 5)	$	—			$	3,041		$	15,288	$	18,329
	Cash settled awards (see Note 7)	—				20,518			—		20,518
	Total Liabilities	$	—			$	23,559		$	15,288	$	38,847
During 2015 and 2014, we had no transfers between Levels 1 and 2.
Level 3 Fair Value Measurements
Except for hedge funds, direct lending funds and our CLO fund priced using NAV as a practical expedient and certain fixed maturities and insurance-linked securities priced using broker-dealer quotes (underlying inputs are not available), the following table quantifies the significant unobservable inputs we have used in estimating fair value at March 31, 2015 for our investments classified as Level 3 in the fair value hierarchy. These significant unobservable inputs have not changed significantly from December 31, 2014.
		Fair Value			Valuation Technique	Unobservable Input	Range	Weighted
								Average
	Other investments - CLO - Equities	$	36,960		Discounted cash flow	Default rates	4.0% - 5.0%	4.30%
						Loss severity rate	53.50%	53.50%
						Collateral spreads	3.0% - 3.5%	3.30%
						Estimated maturity dates	2.9 - 4.1 years	3.6 years
	Derivatives - Weather derivatives, net	$	(7,308	)	Simulation model	Weather curve	632 - 2161(1)	n/a (2)
						Weather standard deviation	59 - 250(1)	n/a (2)
(1) Measured in Heating Degree Days ("HDD") which is the number of degrees the daily temperature is below a reference temperature. The cumulative HDD for the duration of the derivatives contract is compared to the strike value to determine the necessary settlement.
-2	Due to the diversity of the portfolio, the range of unobservable inputs can be widespread; therefore, presentation of a weighted average is not useful. Weather parameters may include various temperature and/or precipitation measures that will naturally vary by geographic location of each counterparty's operations.
The CLO - Equities market continues to be mostly inactive with only a small number of transactions being observed in the market and fewer still involving transactions in our CLO - Equities. Accordingly, we continue to rely on the use of our internal discounted cash flow model (income approach) to estimate fair value of our direct investments in CLO - Equities. Of the significant inputs into this model, the default and loss severity rates are the most judgmental unobservable market inputs to which the valuation of CLO - Equities is most sensitive. A significant increase (decrease) in either of these significant inputs in isolation would result in lower (higher) fair value estimates for direct investments in our CLO - Equities and, in general, a change in default rate assumptions will be accompanied by a directionally similar change in loss severity rate assumptions. Collateral spreads and estimated maturity dates are less judgmental inputs as they are based on the historical average of actual spreads and the weighted average life of the current underlying portfolios, respectively.  A significant increase (decrease) in either of these significant inputs in isolation would result in higher (lower) fair value estimates for direct investments in our CLO - Equities.  In general, these inputs have no significant interrelationship with each other or with default and loss severity rates.
On a quarterly basis, our valuation processes for CLO - Equities includes a review of the underlying cash flows and key assumptions used in the discounted cash flow model. We review and update the above significant unobservable inputs based on information obtained from secondary markets, including from the managers of the CLOs we hold. These inputs are the responsibility of management and, in order to ensure fair value measurement is applied consistently and in accordance with U.S. GAAP, we update our assumptions through regular communication with industry participants and ongoing monitoring of the deals in which we participate (e.g. default and loss severity rate trends), we maintain a current understanding of the market conditions, historical results, as well as emerging trends that may impact future cash flows. By maintaining this current understanding, we are able to assess the reasonableness of the inputs we ultimately use in our model.
Weather derivatives relate to non-exchange traded risk management products addressing weather risks. We use observable market inputs and unobservable inputs in combination with industry or internally-developed simulation models to determine fair value; these models may reference market price information for similar instruments. The pricing models are internally reviewed by Risk Management personnel prior to implementation and are reviewed periodically thereafter.
Observable and unobservable inputs to these models vary by contract type and would typically include the following:
•	Observable inputs: market prices for similar instruments, notional, option strike, term to expiry, contractual limits;
•	Unobservable inputs: correlation; and
•	Both observable and unobservable inputs: weather curves, weather standard deviation.
In general, weather curves are the most significant contributing input to fair value determination; changes in this variable can result in higher or lower fair value depending on the underlying position. In addition, changes in any or all of the unobservable inputs identified above may contribute positively or negatively to overall portfolio value. The correlation input will quantify the interrelationship, if any, amongst the other variables.
The following tables present changes in Level 3 for financial instruments measured at fair value on a recurring basis for the periods indicated:
		Opening				Transfers			Transfers		Included in			Included			Purchases		Sales		Settlements/			Closing		Change in
		Balance				into			out of		earnings (1)			in OCI (2)							Distributions			Balance		unrealized
						Level 3			Level 3																	investment
																										gain/(loss) (3)
	Three months ended March 31, 2015
	Fixed maturities
	Corporate debt	$	15,837			$	—		$	—	$	—		$	180		$	10,910	$	—	$	(70	)	$	26,857	$	—
	CMBS	17,763				—			—		—			(204		)	—		—		(498		)	17,061		—
	ABS	40,031				—			—		—			62			—		—		(172		)	39,921		—
		73,631				—			—		—			38			10,910		—		(740		)	83,839		—
	Other investments
	Hedge funds	470,918				—			—		18,931			—			6,000		—		—			495,849		18,931
	Direct lending funds	54,438				—			—		667			—			15,418		—		(841		)	69,682		667
	CLO - Equities	92,488				—			—		6,087			—			—		—		(6,517		)	92,058		6,087
		617,844				—			—		25,685			—			21,418		—		(7,358		)	657,589		25,685
	Other assets
	Derivative instruments	111				—			—		(1,067		)	—			—		—		956			—		—
	Insurance-linked securities	—				—			—		—			—			25,000		—		—			25,000		—
		111				—			—		(1,067		)	—			25,000		—		956			25,000		—
	Total assets	$	691,586			$	—		$	—	$	24,618		$	38		$	57,328	$	—	$	(7,142	)	$	766,428	$	25,685
	Other liabilities
	Derivative instruments	$	15,288			$	—		$	—	$	(8,551	)	$	—		$	1,082	$	—	$	(511	)	$	7,308	$	(2,058	)
	Total liabilities	$	15,288			$	—		$	—	$	(8,551	)	$	—		$	1,082	$	—	$	(511	)	$	7,308	$	(2,058	)
		Opening				Transfers			Transfers		Included in			Included			Purchases		Sales		Settlements/			Closing		Change in
		Balance				into			out of		earnings (1)			in OCI (2)							Distributions			Balance		unrealized
						Level 3			Level 3																	investment
																										gain/(loss) (3)
	Three months ended March 31, 2014
	Fixed maturities
	Corporate debt	$	—			$	—		$	—	$	—		$	—		$	—	$	—	$	—		$	—	$	—
	CMBS	4,018				—			—		—			(20		)	—		—		(29		)	3,969		—
	ABS	30,799				128			—		—			(95		)	—		—		(108		)	30,724		—
		34,817				128			—		—			(115		)	—		—		(137		)	34,693		—
	Other investments
	Hedge funds	461,055				—			—		8,177			—			4,500		—		(9,066		)	464,666		8,177
	Direct lending funds	22,134				—			—		552			—			3,445		—		(128		)	26,003		552
	CLO - Equities	73,866				—			—		6,150			—			12,845		—		(6,682		)	86,179		6,150
		557,055				—			—		14,879			—			20,790		—		(15,876		)	576,848		14,879
	Other assets
	Derivative instruments	984				—			—		4,718			—			—		—		(3,995		)	1,707		1,540
	Insurance-linked securities	—				—			—		—			—			—		—		—			—		—
		984				—			—		4,718			—			—		—		(3,995		)	1,707		1,540
	Total assets	$	592,856			$	128		$	—	$	19,597		$	(115	)	$	20,790	$	—	$	(20,008	)	$	613,248	$	16,419
	Other liabilities
	Derivative instruments	$	815			$	—		$	—	$	986		$	—		$	—	$	—	$	(1,801	)	$	—	$	—
	Total liabilities	$	815			$	—		$	—	$	986		$	—		$	—	$	—	$	(1,801	)	$	—	$	—
-1	Gains and losses included in earnings on fixed maturities are included in net realized investment gains (losses). Gains and (losses) included in earnings on other investments are included in net investment income. Gains (losses) on weather derivatives included in earnings are included in other insurance-related income.
-2	Gains and losses included in other comprehensive income (“OCI”) on fixed maturities are included in unrealized gains (losses) arising during the period.
-3	Change in unrealized investment gain (loss) relating to assets held at the reporting date.
The transfers into and out of fair value hierarchy levels reflect the fair value of the securities at the end of the reporting period.
Transfers into Level 3 from Level 2
There were no transfers to Level 3 from Level 2 made during the three months ended March 31, 2015. The transfers to Level 3 from Level 2 made during the three months ended March 31, 2014 were primarily due to the lack of observable market inputs and multiple quotes from pricing vendors and broker-dealers for certain fixed maturities.
Transfers out of Level 3 into Level 2
There were no transfers to Level 2 from Level 3 made during the three months ended March 31, 2015 and 2014.
Financial Instruments Not Carried at Fair Value
U.S. GAAP guidance over disclosures about the fair value of financial instruments are also applicable to financial instruments not carried at fair value, except for certain financial instruments, including insurance contracts.
The carrying values of cash equivalents (including restricted amounts), accrued investment income, receivable for investments sold, certain other assets, payable for investments purchased and certain other liabilities approximated their fair values at March 31, 2015, due to their respective short maturities. As these financial instruments are not actively traded, their respective fair values are classified within Level 2.
At March 31, 2015, our senior notes are recorded at amortized cost with a carrying value of $991 million (2014: $991 million) and have a fair value of $1,133 million (2014: $1,089 million). The fair values of these securities were obtained from a third party pricing service and pricing was based on the spread above the risk-free yield curve. These spreads are generally obtained from the new issue market, secondary trading and broker-dealer quotes. As these spreads and the yields for the risk-free yield curve are observable market inputs, the fair values of our senior notes are classified within Level 2.

DERIVATIVE_INSTRUMENTS

DERIVATIVE INSTRUMENTS	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVE INSTRUMENTS	The following table summarizes the balance sheet classification of derivatives recorded at fair values. The notional amount of derivative contracts represents the basis upon which pay or receive amounts are calculated and is presented in the table to quantify the volume of our derivative activities. Notional amounts are not reflective of credit risk.
			March 31, 2015												December 31, 2014
			Derivative				Derivative				Derivative				Derivative				Derivative		Derivative
			Notional				Asset				Liability				Notional				Asset		Liability
			Amount				Fair				Fair				Amount				Fair		Fair
							Value(1)				Value(1)								Value(1)		Value(1)
		Derivatives not designated as hedging instruments
		Relating to investment portfolio:
		Foreign exchange forward contracts	$	235,623			$	3,607			$	40			$	161,678			$	3,925	$	12
		Interest rate swaps	—				—				—				140,000				—		248
		Relating to underwriting portfolio:
		Foreign exchange forward contracts	664,621				643				10,272				577,836				3,228		2,781
		Weather-related contracts	20,995				—				7,308				58,124				111		15,288
		Total derivatives					$	4,250			$	17,620							$	7,264	$	18,329
	-1	Asset and liability derivatives are classified within other assets and other liabilities in the Consolidated Balance Sheets.
	Offsetting Assets and Liabilities
	Our derivative instruments are generally traded under International Swaps and Derivatives Association master netting agreements, which establish terms that apply to all transactions. In the event of a bankruptcy or other stipulated event, master netting agreements provide that individual positions be replaced with a new amount, usually referred to as the termination amount, determined by taking into account market prices and converting into a single currency. Effectively, this contractual close-out netting reduces credit exposure from gross to net exposure. The table below presents a reconciliation of our gross derivative assets and liabilities to the net amounts presented in our Consolidated Balance Sheets, with the difference being attributable to the impact of master netting agreements.
			March 31, 2015										December 31, 2014
			Gross Amounts			Gross Amounts Offset			Net				Gross Amounts			Gross Amounts Offset			Net
									Amounts(1)										Amounts(1)
		Derivative assets	$	11,974		$	(7,724	)	$	4,250			$	15,125		$	(7,861	)	$	7,264
		Derivative liabilities	$	25,344		$	(7,724	)	$	17,620			$	26,190		$	(7,861	)	$	18,329
	-1	Net asset and liability derivatives are classified within other assets and other liabilities in the Consolidated Balance Sheets.
	Refer to Note 3 - Investments for information on reverse repurchase agreements.
	Derivative Instruments not Designated as Hedging Instruments
	a) Relating to Investment Portfolio
	Foreign Currency Risk
	Within our investment portfolio we are exposed to foreign currency risk. Accordingly, the fair values for our investment portfolio are partially influenced by the change in foreign exchange rates. We may enter into foreign exchange forward contracts to manage the effect of this foreign currency risk. These foreign currency hedging activities are not designated as specific hedges for financial reporting purposes.
	The increase in the notional amount of investment-related derivatives since December 31, 2014 was due to an increase in Australian dollar-denominated fixed maturities being hedged.
	Interest Rate Risk
	Our investment portfolio contains a large percentage of fixed maturities which exposes us to significant interest rate risk. As part of our overall management of this risk, we may use interest rate swaps. During the quarter all interest rate swaps were closed.
	b) Relating to Underwriting Portfolio
	Foreign Currency Risk
	Our (re)insurance subsidiaries and branches operate in various foreign countries. Consequently, some of our business is written in currencies other than the U.S. dollar and, therefore, our underwriting portfolio is exposed to significant foreign currency risk. We manage foreign currency risk by seeking to match our foreign-denominated net liabilities under (re)insurance contracts with cash and investments that are denominated in such currencies. We may also use derivative instruments, specifically forward contracts and currency options, to economically hedge foreign currency exposures.
	The increase in the notional amount of underwriting related derivatives since December 31, 2014, was primarily due to new business written during the quarter.
	Weather Risk
	During 2013, we began to write derivative-based risk management products designed to address weather risks with the objective of generating profits on a portfolio basis. The majority of this business consists of receiving a payment at contract inception in exchange for bearing the risk of variations in a quantifiable weather-related phenomenon, such as temperature. Where a client wishes to minimize the upfront payment, these transactions may be structured as swaps or collars. In general, our portfolio of such derivative contracts is of short duration, with contracts being predominantly seasonal in nature. In order to economically hedge a portion of this portfolio, we may also purchase weather derivatives.
	The total unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges were as follows:
			Location of Gain (Loss) Recognized in Income on Derivative	Three months ended March 31,
				2015				2014
		Derivatives not designated as hedging instruments
		Relating to investment portfolio:
		Foreign exchange forward contracts	Net realized investment gains (losses)	$	6,537			$	(1,328	)
		Interest rate swaps	Net realized investment gains (losses)	(4,006		)		(4,161		)
		Relating to underwriting portfolio:
		Foreign exchange forward contracts	Foreign exchange losses (gains)	(15,273		)		12,074
		Weather-related contracts	Other insurance related income	7,342				3,678
		Total		$	(5,400	)		$	10,263

RESERVE_FOR_LOSSES_AND_LOSS_EX

RESERVE FOR LOSSES AND LOSS EXPENSES	3 Months Ended
	Mar. 31, 2015
Insurance Loss Reserves [Abstract]
RESERVE FOR LOSSES AND LOSS EXPENSES	The following table presents a reconciliation of our beginning and ending gross reserve for losses and loss expenses and net reserve for unpaid losses and loss expenses for the periods indicated:
		Three months ended March 31,	2015			2014
		Gross reserve for losses and loss expenses, beginning of period	$	9,596,797		$	9,582,140
		Less reinsurance recoverable on unpaid losses, beginning of period	(1,890,280		)	(1,900,112		)
		Net reserve for unpaid losses and loss expenses, beginning of period	7,706,517			7,682,028
		Net incurred losses and loss expenses related to:
		Current year	568,988			587,700
		Prior years	(50,051		)	(43,493		)
			518,937			544,207
		Net paid losses and loss expenses related to:
		Current year	(23,527		)	(13,249		)
		Prior years	(485,315		)	(444,466		)
			(508,842		)	(457,715		)
		Foreign exchange and other	(162,969		)	14,501
		Net reserve for unpaid losses and loss expenses, end of period	7,553,643			7,783,021
		Reinsurance recoverable on unpaid losses, end of period	1,889,579			1,884,820
		Gross reserve for losses and loss expenses, end of period	$	9,443,222		$	9,667,841
	Prior year reserve development arises from changes to loss and loss expense estimates recognized in the current year but relating to losses incurred in previous calendar years. Such development is summarized by segment in the following table:
			Three months ended March 31,
			2015			2014
		Insurance	$	3,361		$	11,608
		Reinsurance	46,690			31,885
		Total	$	50,051		$	43,493
	The majority of the net favorable prior year reserve development in each period related to short-tail lines of business. Net favorable prior year reserve development for professional and liability reinsurance lines in the three months ended March 31, 2015 and 2014, also contributed. The net favorable prior year development in the liability reinsurance lines in the three months ended March 31, 2015, was offset by net adverse development in the liability insurance lines.
	The underlying exposures in the property, marine and aviation reserving classes within our insurance segment and the property reserving class within our reinsurance segment largely relate to short-tail business. Development from these classes contributed $28 million and $29 million of the total net favorable prior year reserve development for the three months ended March 31, 2015 and 2014, respectively. The net favorable development for these classes primarily reflected the recognition of better than expected loss emergence.
	Our medium-tail business consists primarily of professional insurance and reinsurance lines, credit and political risk insurance lines and credit and surety reinsurance business. Our professional lines reinsurance business contributed further net favorable prior year reserve development of $20 million and $6 million in the three months ended March 31, 2015, and 2014, respectively. This prior year reserve development was driven by increased weight being given to experience based actuarial methods in selecting our ultimate loss estimates for accident years 2010 and prior. As our loss experience has generally been better than expected, this resulted in the recognition of favorable development. In the three months ended March 31, 2015, we recorded adverse prior year reserve development of $11 million in our insurance credit and political risk lines relating primarily to an increase in loss estimates for one specific claim.
	Our liability lines reinsurance business contributed additional favorable development of $12 million and $6 million in the three months ended March 31, 2015, and 2014, respectively, primarily reflecting the greater weight management is giving to experience based indications and our experience which has been favorable for the 2005 through 2009 accident years.
	In the three months ended March 31, 2015, we recorded adverse prior year reserve development of $11 million in our insurance liability lines relating primarily to an increase in loss estimates for one specific claim.
	The frequency and severity of natural catastrophe and weather activity was high in recent years and our March 31, 2015 net reserve for losses and loss expenses continues to include estimated amounts for numerous events. We caution that the magnitude and/or complexity of losses arising from certain of these events, in particular Storm Sandy, the Japanese earthquake and tsunami and the three New Zealand earthquakes, inherently increases the level of uncertainty and, therefore, the level of management judgment involved in arriving at our estimated net reserves for losses and loss expenses. As a result, our actual losses for these events may ultimately differ materially from our current estimates.

SHAREBASED_COMPENSATION

SHARE-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
SHARE-BASED COMPENSATION	For the three months ended March 31, 2015, we incurred share-based compensation costs of $19 million (2014: $17 million) and recorded associated tax benefits of $4 million (2014: $3 million).
	The fair value of shares vested during the three months ended March 31, 2015 was $63 million (2014: $61 million). At March 31, 2015 there were $148 million of unrecognized share-based compensation costs, which are expected to be recognized over the weighted average period of 2.6 years.
	Awards to settle in shares
	The following table provides a reconciliation of the beginning and ending balance of nonvested restricted stock (including restricted stock units) for the three months ended March 31, 2015:
			Performance-based Stock Awards			Service-based Stock Awards
			Number of	Weighted Average		Number of		Weighted Average
			Restricted	Grant Date		Restricted		Grant Date
			Stock	Fair Value		Stock		Fair Value
		Nonvested restricted stock - beginning of period	347	$	37.34	2,768		$	38.7
		Granted	60	51.31		511		51.31
		Vested	—	—		(984	)	36.42
		Forfeited	—	—		(17	)	41.28
		Nonvested restricted stock - end of period	407	$	39.39	2,278		$	42.49
	Cash-settled awards
	During 2015 we also granted 486,508 restricted stock units that will settle in cash rather than shares when the awards ultimately vest; of which 18,659 restricted stock units are performance based and 467,849 restricted stock units are service based. At March 31, 2015, the corresponding liability for cash-settled units, included in other liabilities on the Consolidated Balance Sheet, was $13 million (2014: $5 million).

EARNINGS_PER_COMMON_SHARE

EARNINGS PER COMMON SHARE	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
EARNINGS PER COMMON SHARE	The following table sets forth the comparison of basic and diluted earnings per common share:
			Three months ended March 31,
			2015			2014
		Basic earnings per common share
		Net income	$	160,952		$	148,471
		Less: Amounts attributable to (from) noncontrolling interests	(4,873		)	1,222
		Less: preferred share dividends	10,022			10,022
		Net income available to common shareholders	155,803			137,227
		Weighted average common shares outstanding - basic	99,910			109,053
		Basic earnings per common share	$	1.56		$	1.26
		Diluted earnings per common share
		Net income available to common shareholders	$	155,803		$	137,227
		Weighted average common shares outstanding - basic	99,910			109,053
		Stock compensation plans	1,229			1,338
		Weighted average common shares outstanding - diluted	101,139			110,391
		Diluted earnings per common share	$	1.54		$	1.24
		Anti-dilutive shares excluded from the dilutive computation	569			1,051

SHAREHOLDERS_EQUITY

SHAREHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2015
Stockholders' Equity Note [Abstract]
SHAREHOLDERS' EQUITY	The following table presents our common shares issued and outstanding:
			Three months ended March 31,
			2015		2014
		Shares issued, balance at beginning of period	175,478		174,134
		Shares issued	712		1,061
		Total shares issued at end of period	176,190		175,195
		Treasury shares, balance at beginning of period	(76,052	)	(64,649	)
		Shares repurchased	(290	)	(4,036	)
		Shares reissued from treasury	371		235
		Total treasury shares at end of period	(75,971	)	(68,450	)
		Total shares outstanding	100,219		106,745
	Treasury Shares
	The following table presents our share repurchases:
			Three months ended March 31,
			2015			2014
		In the open market:
		Total shares	16			3,710
		Total cost	$	832		$	164,606
		Average price per share(1)	$	50.69		$	44.37
		From employees:
		Total shares	274			326
		Total cost	$	13,939		$	14,097
		Average price per share(1)	$	50.97		$	43.14
		Total shares repurchased:
		Total shares	290			4,036
		Total cost	$	14,771		$	178,703
		Average price per share(1)	$	50.95		$	44.27
	-1	Calculated using whole figures.

NONCONTROLLING_INTERESTS

NONCONTROLLING INTERESTS	3 Months Ended
	Mar. 31, 2015
Noncontrolling Interest [Abstract]
Noncontrolling Interests	During November 2013, the Company formed AXIS Ventures Reinsurance Limited ("Ventures Re"), a Bermuda domiciled insurer. Ventures Re was formed to write reinsurance on a fully collateralized basis.
	During the first quarter of 2015, Ventures Re repurchased $40 million of Class A non-voting redeemable preferred shares. Additionally, during the first quarter of 2015, third party investors purchased $57 million of Class C non-voting redeemable preferred share capital issued by Ventures Re. The Ventures Re Class C preferred shares are redeemable at the sole discretion of Ventures Re's Board of Directors.
	Ventures Re is considered to be a variable interest entity. The Company has concluded that it is the primary beneficiary of Ventures Re as it has the power to direct, and has more than an insignificant economic interest in, the activities of this entity. Following this determination, Ventures Re was consolidated by the Company. Shareholders' equity attributable to Ventures Re's third party investors is recorded in the Consolidated Financial Statements as noncontrolling interests.
	At March 31, 2015, total assets of Ventures Re were $120 million (2014: $97 million), consisting primarily of cash and cash equivalents and insurance receivables. Total liabilities were $50 million (2014: $38 million) consisting primarily of loss reserves and unearned premium. The assets of Ventures Re can only be used to settle its own liabilities, and there is no recourse to the Company for any liabilities incurred by this entity.
	The reconciliation of the beginning and ending balances of the noncontrolling interests in Ventures Re for the periods indicated below was as follows:
		Three months ended March 31,	2015			2014
		Balance at beginning of period	$	58,819		$	50,000
		Increase from issuance of preferred equity to noncontrolling interests	56,991			—
		Decrease from return of capital to noncontrolling interests	(40,000		)	—
		Amounts attributable to (from) noncontrolling interests	(4,873		)	1,222
		Foreign currency translation adjustment attributable to (from) noncontrolling interests	(1,865		)	—
		Balance at end of period	$	69,072		$	51,222

DEBT_AND_FINANCING_ARRANGEMENT

DEBT AND FINANCING ARRANGEMENTS	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
DEBT AND FINANCING ARRANGEMENTS	March 31, 2015, the Company entered into an amendment to reduce the maximum aggregate utilization capacity of our secured letter of credit facility with Citibank Europe plc (the "LOC Facility") from $750 million to $500 million. All other material terms and conditions remained unchanged. At March 31, 2015, letters of credit outstanding under the LOC Facility totaled $354 million.

COMMITMENTS_AND_CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	Reinsurance Agreements
	We purchase reinsurance coverage for various lines of our business. The minimum reinsurance premiums are contractually due in advance on a quarterly basis. Accordingly at March 31, 2015, we have outstanding reinsurance purchase commitments of $72 million, of which $64 million is due in 2015 while the remaining $8 million is due in 2016. Actual payments under the reinsurance contracts will depend on the underlying subject premium and may exceed the minimum premium.
	Amalgamation Agreement
	On January 25, 2015, the Company entered into an Agreement and Plan of Amalgamation (the "Amalgamation Agreement") with PartnerRe Ltd. , a Bermuda exempted company ("PartnerRe"), which agreement was thereafter amended on February 17, 2015, March 10, 2015, and March 31, 2015, and pursuant to which the Company would amalgamate with PartnerRe (the "Amalgamation"), and the two companies would continue as a single Bermuda exempted company. On May 3, 2015, the Company and PartnerRe further amended the Amalgamation Agreement (the "Amendment to the Amalgamation Agreement") to allow PartnerRe to pay a one-time special dividend of $11.50 per share to PartnerRe's common shareholders in connection with the closing of the Amalgamation.
	In accordance with the terms of the Amalgamation Agreement and the Amendment to the Amalgamation Agreement, the Company would be obligated to pay PartnerRe a no approval fee of $55 million if the Company’s shareholders do not approve the transaction. If the Amalgamation Agreement is terminated for certain other reasons described in the Amalgamation Agreement or if in certain circumstances the Company enters into a similar transaction with a third party in the 12 months following termination of the Amalgamation Agreement, the Company would be obligated to pay PartnerRe an aggregate termination fee of $280 million (less any no approval fee already paid). In all such cases, the Company would be obligated to reimburse PartnerRe for costs and expenses incurred in connection with the Amalgamation Agreement and the transactions contemplated thereby in an amount not to exceed $35 million.
	In relation to the proposed Amalgamation, the Company has entered into an agreement with a financial advisor that will require the Company to make a payment of $20 million in the event that the amalgamation transaction with PartnerRe is successfully consummated.
	Employment Agreements
	Following the signing of the Amalgamation Agreement, the Company has entered into additional agreements with certain employees. These agreements provide for the payment of a special cash retention award, which is payable in addition to normal annual compensation amounts, with the award payment being dependent on the employee maintaining an active employee status through a pre-determined future date and fulfilling certain conduct and performance-related conditions. The additional award payments are only payable in relation to, and are dependent on, the successful closing of the current amalgamation with PartnerRe.
	Investments
	At March 31, 2015 we have a $50 million commitment to purchase Commercial Mortgage Loans.
	Refer 'Note 3 - Investments' for information on commitments related to our other investments.

OTHER_COMPREHENSIVE_INCOME

OTHER COMPREHENSIVE INCOME	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
OTHER COMPREHENSIVE INCOME	The tax effects allocated to each component of other comprehensive income were as follows:
			2015											2014
			Before Tax Amount				Tax (Expense) Benefit				Net of Tax Amount			Before Tax Amount			Tax (Expense) Benefit			Net of Tax Amount
		Three months ended March 31,
		Available for sale investments:
		Unrealized gains (losses) arising during the period	$	5,063			$	(10,250	)		$	(5,187	)	$	80,560		$	(9,177	)	$	71,383
		Adjustment for reclassification of net realized investment gains (losses) and OTTI losses recognized in net income	45,098				6				45,104			(16,069		)	6,456			(9,613		)
		Unrealized gains arising during the period, net of reclassification adjustment	50,161				(10,244		)		39,917			64,491			(2,721		)	61,770
		Non-credit portion of OTTI losses	—				—				—			—			—			—
		Foreign currency translation adjustment	(13,278		)		—				(13,278		)	2,659			—			2,659
		Total other comprehensive income, net of tax	$	36,883			$	(10,244	)		$	26,639		$	67,150		$	(2,721	)	$	64,429
	Reclassifications out of AOCI into net income available to common shareholders were as follows:
				Amount Reclassified from AOCI(1)
		Details About AOCI Components	Consolidated Statement of Operations Line Item That Includes Reclassification	Three months ended March 31,
				2015				2014
		Unrealized gains (losses) on available for sale investments
			Other realized investment gains (losses)	$	(27,530	)		$	16,855
			OTTI losses	(17,568		)		(786		)
			Total before tax	(45,098		)		16,069
			Income tax expense	(6		)		(6,456		)
			Net of tax	$	(45,104	)		$	9,613
	-1	Amounts in parentheses are debits to net income available to common shareholders.

SUBSEQUENT_EVENTS

SUBSEQUENT EVENTS	3 Months Ended
	Mar. 31, 2015
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	Acquisition of Ternian
	On April 1, 2015, the Company announced that it completed the acquisition of Ternian Insurance Group LLC, a leading provider of voluntary, limited benefit, affordable health plans and other employee benefits coverage for hourly and part-time workers and their families. The Company recognized intangible assets of $13 million associated with this acquisition.
	Amendments to the Amalgamation Agreement
	On April 14, 2015, PartnerRe announced the receipt of an unsolicited proposal from a third party to acquire all of its outstanding common shares for $130.00 per share in cash.
	On May 3, 2015, the Company and PartnerRe amended the Amalgamation Agreement to allow PartnerRe to pay a one-time special dividend of $11.50 per share to PartnerRe's common shareholders in connection with the closing of the Amalgamation and to increase the termination fee from $250 million to $280 million.
	On May 4, 2015, PartnerRe's Board of Directors announced that it had terminated discussions with the third party regarding their $130.00 per share offer.

BASIS_OF_PRESENTATION_AND_ACCO1

BASIS OF PRESENTATION AND ACCOUNTING POLICIES (POLICIES)	3 Months Ended
	Mar. 31, 2015
Policy Text Block [Abstract]
Basis of Presentation	Basis of Presentation
	These interim consolidated financial statements include the accounts of AXIS Capital Holdings Limited (“AXIS Capital”) and its subsidiaries (herein referred to as “we,” “us,” “our,” or the “Company”).
	The consolidated balance sheet at March 31, 2015 and the consolidated statements of operations, comprehensive income, shareholders' equity and cash flows for the periods ended March 31, 2015 and 2014 have not been audited. The balance sheet at December 31, 2014 is derived from our audited financial statements.
	These financial statements have been prepared in accordance with U.S. Generally Accepted Accounting Principles (“U.S. GAAP”) for interim financial information and with the Securities and Exchange Commission's (“SEC”) instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and footnotes required by U.S. GAAP for complete financial statements. In the opinion of management, these financial statements reflect all adjustments (consisting of normal recurring adjustments) considered necessary for a fair presentation of our financial position and results of operations for the periods presented. The results of operations for any interim period are not necessarily indicative of the results for a full year. All inter-company accounts and transactions have been eliminated.
	The following information should be read in conjunction with our Annual Report on Form 10-K for the year ended December 31, 2014. Tabular dollar and share amounts are in thousands, except per share amounts. All amounts are reported in U.S. dollars.
	Significant Accounting Policies
	There were no notable changes in our significant accounting policies subsequent to our Annual Report on Form 10-K for the year ended December 31, 2014

SEGMENT_INFORMATION_TABLES

SEGMENT INFORMATION (TABLES)	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
UNDERWRITING RESULTS OF REPORTABLE SEGMENTS
	The following tables summarize the underwriting results of our reportable segments, as well as the carrying values of allocated goodwill and intangible assets:
			2015									2014
		Three months ended and at March 31,	Insurance			Reinsurance			Total			Insurance			Reinsurance			Total
		Gross premiums written	$	602,724		$	1,076,208		$	1,678,932		$	601,721		$	1,219,678		$	1,821,399
		Net premiums written	436,740			1,026,812			1,463,552			456,692			1,207,892			1,664,584
		Net premiums earned	447,467			458,755			906,222			449,214			496,735			945,949
		Other insurance related income	—			7,676			7,676			—			3,082			3,082
		Net losses and loss expenses	(285,773		)	(233,164		)	(518,937		)	(279,423		)	(264,784		)	(544,207		)
		Acquisition costs	(64,455		)	(107,247		)	(171,702		)	(65,057		)	(106,979		)	(172,036		)
		General and administrative expenses	(87,689		)	(39,656		)	(127,345		)	(87,946		)	(36,076		)	(124,022		)
		Underwriting income	$	9,550		$	86,364		95,914			$	16,788		$	91,978		108,766
		Corporate expenses							(36,172		)							(28,707		)
		Net investment income							92,110									82,744
		Net realized investment gains (losses)							(42,553		)							10,620
		Foreign exchange (losses) gains							63,220									(4,233		)
		Interest expense and financing costs							(12,257		)							(16,594		)
		Income before income taxes							$	160,262								$	152,596
		Net loss and loss expense ratio	63.9		%	50.8		%	57.3		%	62.2		%	53.3		%	57.5		%
		Acquisition cost ratio	14.4		%	23.4		%	18.9		%	14.5		%	21.5		%	18.2		%
		General and administrative expense ratio	19.6		%	8.6		%	18.1		%	19.6		%	7.3		%	16.2		%
		Combined ratio	97.9		%	82.8		%	94.3		%	96.3		%	82.1		%	91.9		%
		Goodwill and intangible assets	$	88,508		$	—		$	88,508		$	90,350		$	—		$	90,350

INVESTMENTS_TABLES

INVESTMENTS (TABLES)	3 Months Ended
	Mar. 31, 2015
Investments, Debt and Equity Securities [Abstract]
AMORTIZED COST/COST AND FAIR VALUES OF FIXED MATURITIES AND EQUITIES	The amortized cost or cost and fair values of our fixed maturities and equities were as follows:
			Amortized			Gross				Gross			Fair			Non-credit
			Cost or			Unrealized				Unrealized			Value			OTTI
			Cost			Gains				Losses						in AOCI(5)
		At March 31, 2015
		Fixed maturities
		U.S. government and agency	$	1,490,502		$	9,183			$	(5,528	)	$	1,494,157		$	—
		Non-U.S. government	932,741			7,041				(66,685		)	873,097			—
		Corporate debt	4,549,974			58,133				(73,829		)	4,534,278			—
		Agency RMBS(1)	2,150,598			51,061				(1,416		)	2,200,243			—
		CMBS(2)	1,111,327			21,219				(1,223		)	1,131,323			—
		Non-Agency RMBS	77,185			2,560				(1,744		)	78,001			(865		)
		ABS(3)	1,500,493			3,438				(8,102		)	1,495,829			—
		Municipals(4)	199,813			6,649				(496		)	205,966			—
		Total fixed maturities	$	12,012,633		$	159,284			$	(159,023	)	$	12,012,894		$	(865	)
		Equity securities
		Exchange-traded funds	453,978			46,224				(2,155		)	498,047
		Non-U.S. bond mutual funds	118,339			—				(15,057		)	103,282
		Total equity securities	$	572,317		$	46,224			$	(17,212	)	$	601,329
		At December 31, 2014
		Fixed maturities
		U.S. government and agency	$	1,645,068		$	3,337			$	(28,328	)	$	1,620,077		$	—
		Non-U.S. government	1,080,601			7,383				(54,441		)	1,033,543			—
		Corporate debt	4,386,432			40,972				(66,280		)	4,361,124			—
		Agency RMBS(1)	2,241,581			40,762				(4,235		)	2,278,108			—
		CMBS(2)	1,085,618			13,289				(2,019		)	1,096,888			—
		Non-Agency RMBS	71,236			2,765				(915		)	73,086			(889		)
		ABS(3)	1,475,026			2,748				(16,188		)	1,461,586			—
		Municipals(4)	200,411			5,282				(832		)	204,861			—
		Total fixed maturities	$	12,185,973		$	116,538			$	(173,238	)	$	12,129,273		$	(889	)
		Equity securities
		Exchange-traded funds	416,063			43,583				(4,756		)	454,890
		Non-U.S. bond mutual funds	115,585			—				(2,768		)	112,817
		Total equity securities	$	531,648		$	43,583			$	(7,524	)	$	567,707
	-1	Residential mortgage-backed securities (RMBS) originated by U.S. agencies.
	-2	Commercial mortgage-backed securities (CMBS).
	-3	Asset-backed securities (ABS) include debt tranched securities collateralized primarily by auto loans, student loans, credit cards, and other asset types. This asset class also includes collateralized loan obligations (CLOs) and collateralized debt obligations (CDOs).
	-4	Municipals include bonds issued by states, municipalities and political subdivisions.
	-5	Represents the non-credit component of the other-than-temporary impairment (OTTI) losses, adjusted for subsequent sales of securities. It does not include the change in fair value subsequent to the impairment measurement date.
CONTRACTUAL MATURITIES OF FIXED MATURITIES	The contractual maturities of fixed maturities are shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.
			Amortized			Fair				% of Total
			Cost			Value				Fair Value
		At March 31, 2015
		Maturity
		Due in one year or less	$	508,448		$	503,179			4.2	%
		Due after one year through five years	4,387,194			4,349,800				36.2	%
		Due after five years through ten years	2,042,045			2,016,713				16.8	%
		Due after ten years	235,343			237,806				2	%
			7,173,030			7,107,498				59.2	%
		Agency RMBS	2,150,598			2,200,243				18.3	%
		CMBS	1,111,327			1,131,323				9.4	%
		Non-Agency RMBS	77,185			78,001				0.6	%
		ABS	1,500,493			1,495,829				12.5	%
		Total	$	12,012,633		$	12,012,894			100	%
		At December 31, 2014
		Maturity
		Due in one year or less	$	424,077		$	423,265			3.5	%
		Due after one year through five years	4,925,780			4,892,411				40.3	%
		Due after five years through ten years	1,755,248			1,695,641				14	%
		Due after ten years	207,407			208,288				1.7	%
			7,312,512			7,219,605				59.5	%
		Agency RMBS	2,241,581			2,278,108				18.8	%
		CMBS	1,085,618			1,096,888				9	%
		Non-Agency RMBS	71,236			73,086				0.6	%
		ABS	1,475,026			1,461,586				12.1	%
		Total	$	12,185,973		$	12,129,273			100	%
FIXED MATURITIES AND EQUITIES IN AN UNREALIZED LOSS POSITION	The following table summarizes fixed maturities and equities in an unrealized loss position and the aggregate fair value and gross unrealized loss by length of time the security has continuously been in an unrealized loss position:
			12 months or greater							Less than 12 months						Total
			Fair			Unrealized				Fair			Unrealized			Fair			Unrealized
			Value			Losses				Value			Losses			Value			Losses
		At March 31, 2015
		Fixed maturities
		U.S. government and agency	$	94,248		$	(4,525	)		$	329,487		$	(1,003	)	$	423,735		$	(5,528	)
		Non-U.S. government	112,581			(31,924		)		349,284			(34,761		)	461,865			(66,685		)
		Corporate debt	53,901			(5,679		)		1,263,181			(68,150		)	1,317,082			(73,829		)
		Agency RMBS	55,492			(748		)		208,699			(668		)	264,191			(1,416		)
		CMBS	54,293			(719		)		145,716			(504		)	200,009			(1,223		)
		Non-Agency RMBS	5,685			(762		)		17,917			(982		)	23,602			(1,744		)
		ABS	449,335			(6,367		)		544,239			(1,735		)	993,574			(8,102		)
		Municipals	14,528			(139		)		16,297			(357		)	30,825			(496		)
		Total fixed maturities	$	840,063		$	(50,863	)		$	2,874,820		$	(108,160	)	$	3,714,883		$	(159,023	)
		Equity securities
		Exchange-traded funds	—			—				80,230			(2,155		)	80,230			(2,155		)
		Non-U.S. bond mutual funds	—			—				103,282			(15,057		)	103,282			(15,057		)
		Total equity securities	$	—		$	—			$	183,512		$	(17,212	)	$	183,512		$	(17,212	)
		At December 31, 2014
		Fixed maturities
		U.S. government and agency	$	388,551		$	(24,319	)		$	786,850		$	(4,009	)	$	1,175,401		$	(28,328	)
		Non-U.S. government	143,602			(29,171		)		435,670			(25,270		)	579,272			(54,441		)
		Corporate debt	26,708			(2,221		)		2,199,672			(64,059		)	2,226,380			(66,280		)
		Agency RMBS	259,914			(3,084		)		333,288			(1,151		)	593,202			(4,235		)
		CMBS	68,624			(925		)		256,225			(1,094		)	324,849			(2,019		)
		Non-Agency RMBS	6,689			(613		)		13,442			(302		)	20,131			(915		)
		ABS	425,663			(10,325		)		750,679			(5,863		)	1,176,342			(16,188		)
		Municipals	34,462			(644		)		25,284			(188		)	59,746			(832		)
		Total fixed maturities	$	1,354,213		$	(71,302	)		$	4,801,110		$	(101,936	)	$	6,155,323		$	(173,238	)
		Equity securities
		Exchange-traded funds	—			—				91,275			(4,756		)	91,275			(4,756		)
		Non-U.S. bond mutual funds	—			—				112,817			(2,768		)	112,817			(2,768		)
		Total equity securities	$	—		$	—			$	204,092		$	(7,524	)	$	204,092		$	(7,524	)
PORTFOLIO OF OTHER INVESTMENTS	The following table provides a breakdown of our investments in hedge funds, direct lending funds and CLO Equities, together with additional information relating to the liquidity of each category:
			Fair Value						Redemption Frequency		Redemption
									(if currently eligible)		Notice Period
		At March 31, 2015
		Long/short equity funds	$	242,096		26	%		Quarterly, Semi-annually		30-60 days
		Multi-strategy funds	336,342			36	%		Quarterly, Semi-annually		60-95 days
		Event-driven funds	189,212			20	%		Quarterly, Annually		45-60 days
		Leveraged bank loan funds	9,616			1	%		Quarterly		65 days
		Direct lending funds	69,682			7	%		n/a		n/a
		CLO - Equities	92,058			10	%		n/a		n/a
		Total other investments	$	939,006		100	%
		At December 31, 2014
		Long/short equity funds	$	298,907		31	%		Quarterly, Semi-annually		30-60 days
		Multi-strategy funds	324,020			34	%		Quarterly, Semi-annually		60-95 days
		Event-driven funds	185,899			19	%		Quarterly, Annually		45-60 days
		Leveraged bank loan funds	9,713			1	%		Quarterly		65 days
		Direct lending funds	54,438			6	%		n/a		n/a
		CLO - Equities	92,488			9	%		n/a		n/a
		Total other investments	$	965,465		100	%
	n/a - not applicable
NET INVESTMENT INCOME	Net investment income was derived from the following sources:
			Three months ended March 31,
			2015			2014
		Fixed maturities	$	66,101		$	72,957
		Other investments	30,935			16,760
		Equity securities	1,676			2,286
		Cash and cash equivalents	1,102			863
		Short-term investments	69			214
		Gross investment income	99,883			93,080
		Investment expenses	(7,773		)	(10,336		)
		Net investment income	$	92,110		$	82,744
NET REALIZED INVESTMENT GAINS (LOSSES)	The following table provides an analysis of net realized investment gains (losses):
			Three months ended March 31,
			2015			2014
		Gross realized gains
		Fixed maturities and short-term investments	$	15,661		$	33,770
		Equities	38			19,267
		Gross realized gains	15,699			53,037
		Gross realized losses
		Fixed maturities and short-term investments	(43,091		)	(33,704		)
		Equities	(124		)	(2,438		)
		Gross realized losses	(43,215		)	(36,142		)
		Net OTTI recognized in earnings	(17,568		)	(786		)
		Change in fair value of investment derivatives(1)	2,531			(5,489		)
		Net realized investment gains (losses)	$	(42,553	)	$	10,620
	(1) Refer to Note 5 – Derivative Instruments
OTTI RECOGNIZED IN EARNINGS BY ASSET CLASS	The following table summarizes the OTTI recognized in earnings by asset class:
			Three months ended March 31,
			2015			2014
		Fixed maturities:
		Non-U.S. government	$	1,422		$	38
		Corporate debt	16,120			15
		Non-Agency RMBS	4			—
		ABS	22			56
			17,568			109
		Equity Securities
		Common stocks	—			677
			—			677
		Total OTTI recognized in earnings	$	17,568		$	786
ROLL FORWARD OF CREDIT LOSSES FOR WHICH A PORTION OF OTTI RECOGNIZED IN AOCI	The following table provides a roll forward of the credit losses, before income taxes, for which a portion of the OTTI was recognized in AOCI:
			Three months ended March 31,
			2015			2014
		Balance at beginning of period	$	1,531		$	1,594
		Credit impairments recognized on securities not previously impaired	—			—
		Additional credit impairments recognized on securities previously impaired	10			—
		Change in timing of future cash flows on securities previously impaired	—			—
		Intent to sell of securities previously impaired	—			—
		Securities sold/redeemed/matured	—			(4		)
		Balance at end of period	$	1,541		$	1,590

FAIR_VALUE_MEASUREMENTS_TABLES

FAIR VALUE MEASUREMENTS (TABLES)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
FINANCIAL INSTRUMENTS MEASURED AT FAIR VALUE ON A RECURRING BASIS	The table below presents the financial instruments measured at fair value on a recurring basis:
			Quoted Prices in				Significant			Significant		Total Fair
			Active Markets for				Other Observable			Unobservable		Value
			Identical Assets				Inputs			Inputs
			(Level 1)				(Level 2)			(Level 3)
		At March 31, 2015
		Assets
		Fixed maturities
		U.S. government and agency	$	1,400,810			$	93,347		$	—	$	1,494,157
		Non-U.S. government	—				873,097			—		873,097
		Corporate debt	—				4,507,421			26,857		4,534,278
		Agency RMBS	—				2,200,243			—		2,200,243
		CMBS	—				1,114,262			17,061		1,131,323
		Non-Agency RMBS	—				78,001			—		78,001
		ABS	—				1,455,908			39,921		1,495,829
		Municipals	—				205,966			—		205,966
			1,400,810				10,528,245			83,839		12,012,894
		Equity securities
		Exchange-traded funds	498,047				—			—		498,047
		Non-U.S. bond mutual funds	—				103,282			—		103,282
			498,047				103,282			—		601,329
		Other investments
		Hedge funds	—				281,417			495,849		777,266
		Direct lending funds	—				—			69,682		69,682
		CLO - Equities	—				—			92,058		92,058
			—				281,417			657,589		939,006
		Short-term investments	—				38,373			—		38,373
		Derivative instruments (see Note 5)	—				4,250			—		4,250
		Insurance-linked securities	—				—			25,000		25,000
		Total Assets	$	1,898,857			$	10,955,567		$	766,428	$	13,620,852
		Liabilities
		Derivative instruments (see Note 5)	$	—			$	10,312		$	7,308	$	17,620
		Cash settled awards (see Note 7)	—				12,641			—		12,641
		Total Liabilities	$	—			$	22,953		$	7,308	$	30,261
		At December 31, 2014
		Assets
		Fixed maturities
		U.S. government and agency	$	1,497,922			$	122,155		$	—	$	1,620,077
		Non-U.S. government	—				1,033,543			—		1,033,543
		Corporate debt	—				4,345,287			15,837		4,361,124
		Agency RMBS	—				2,278,108			—		2,278,108
		CMBS	—				1,079,125			17,763		1,096,888
		Non-Agency RMBS	—				73,086			—		73,086
		ABS	—				1,421,555			40,031		1,461,586
		Municipals	—				204,861			—		204,861
			1,497,922				10,557,720			73,631		12,129,273
		Equity securities
		Exchange-traded funds	454,890				—			—		454,890
		Non-U.S. bond mutual funds	—				112,817			—		112,817
			454,890				112,817			—		567,707
		Other investments
		Hedge funds	—				347,621			470,918		818,539
		Direct lending funds	—				—			54,438		54,438
		CLO - Equities	—				—			92,488		92,488
			—				347,621			617,844		965,465
		Short-term investments	—				107,534			—		107,534
		Derivative instruments (see Note 5)	—				7,153			111		7,264
		Insurance-linked securities	—				—			—		—
		Total Assets	$	1,952,812			$	11,132,845		$	691,586	$	13,777,243
		Liabilities
		Derivative instruments (see Note 5)	$	—			$	3,041		$	15,288	$	18,329
		Cash settled awards (see Note 7)	—				20,518			—		20,518
		Total Liabilities	$	—			$	23,559		$	15,288	$	38,847
LEVEL 3 FAIR VALUE MEASUREMENT INPUTS	Except for hedge funds, direct lending funds and our CLO fund priced using NAV as a practical expedient and certain fixed maturities and insurance-linked securities priced using broker-dealer quotes (underlying inputs are not available), the following table quantifies the significant unobservable inputs we have used in estimating fair value at March 31, 2015 for our investments classified as Level 3 in the fair value hierarchy. These significant unobservable inputs have not changed significantly from December 31, 2014.
			Fair Value			Valuation Technique	Unobservable Input	Range	Weighted
									Average
		Other investments - CLO - Equities	$	36,960		Discounted cash flow	Default rates	4.0% - 5.0%	4.30%
							Loss severity rate	53.50%	53.50%
							Collateral spreads	3.0% - 3.5%	3.30%
							Estimated maturity dates	2.9 - 4.1 years	3.6 years
		Derivatives - Weather derivatives, net	$	(7,308	)	Simulation model	Weather curve	632 - 2161(1)	n/a (2)
							Weather standard deviation	59 - 250(1)	n/a (2)
	(1) Measured in Heating Degree Days ("HDD") which is the number of degrees the daily temperature is below a reference temperature. The cumulative HDD for the duration of the derivatives contract is compared to the strike value to determine the necessary settlement.
	-2	Due to the diversity of the portfolio, the range of unobservable inputs can be widespread; therefore, presentation of a weighted average is not useful. Weather parameters may include various temperature and/or precipitation measures that will naturally vary by geographic location of each counterparty's operations.
CHANGES IN LEVEL 3 FINANCIAL INSTRUMENTS MEASURED AT FAIR VALUE ON A RECURRING BASIS	The following tables present changes in Level 3 for financial instruments measured at fair value on a recurring basis for the periods indicated:
			Opening				Transfers			Transfers		Included in			Included			Purchases		Sales		Settlements/			Closing		Change in
			Balance				into			out of		earnings (1)			in OCI (2)							Distributions			Balance		unrealized
							Level 3			Level 3																	investment
																											gain/(loss) (3)
		Three months ended March 31, 2015
		Fixed maturities
		Corporate debt	$	15,837			$	—		$	—	$	—		$	180		$	10,910	$	—	$	(70	)	$	26,857	$	—
		CMBS	17,763				—			—		—			(204		)	—		—		(498		)	17,061		—
		ABS	40,031				—			—		—			62			—		—		(172		)	39,921		—
			73,631				—			—		—			38			10,910		—		(740		)	83,839		—
		Other investments
		Hedge funds	470,918				—			—		18,931			—			6,000		—		—			495,849		18,931
		Direct lending funds	54,438				—			—		667			—			15,418		—		(841		)	69,682		667
		CLO - Equities	92,488				—			—		6,087			—			—		—		(6,517		)	92,058		6,087
			617,844				—			—		25,685			—			21,418		—		(7,358		)	657,589		25,685
		Other assets
		Derivative instruments	111				—			—		(1,067		)	—			—		—		956			—		—
		Insurance-linked securities	—				—			—		—			—			25,000		—		—			25,000		—
			111				—			—		(1,067		)	—			25,000		—		956			25,000		—
		Total assets	$	691,586			$	—		$	—	$	24,618		$	38		$	57,328	$	—	$	(7,142	)	$	766,428	$	25,685
		Other liabilities
		Derivative instruments	$	15,288			$	—		$	—	$	(8,551	)	$	—		$	1,082	$	—	$	(511	)	$	7,308	$	(2,058	)
		Total liabilities	$	15,288			$	—		$	—	$	(8,551	)	$	—		$	1,082	$	—	$	(511	)	$	7,308	$	(2,058	)
			Opening				Transfers			Transfers		Included in			Included			Purchases		Sales		Settlements/			Closing		Change in
			Balance				into			out of		earnings (1)			in OCI (2)							Distributions			Balance		unrealized
							Level 3			Level 3																	investment
																											gain/(loss) (3)
		Three months ended March 31, 2014
		Fixed maturities
		Corporate debt	$	—			$	—		$	—	$	—		$	—		$	—	$	—	$	—		$	—	$	—
		CMBS	4,018				—			—		—			(20		)	—		—		(29		)	3,969		—
		ABS	30,799				128			—		—			(95		)	—		—		(108		)	30,724		—
			34,817				128			—		—			(115		)	—		—		(137		)	34,693		—
		Other investments
		Hedge funds	461,055				—			—		8,177			—			4,500		—		(9,066		)	464,666		8,177
		Direct lending funds	22,134				—			—		552			—			3,445		—		(128		)	26,003		552
		CLO - Equities	73,866				—			—		6,150			—			12,845		—		(6,682		)	86,179		6,150
			557,055				—			—		14,879			—			20,790		—		(15,876		)	576,848		14,879
		Other assets
		Derivative instruments	984				—			—		4,718			—			—		—		(3,995		)	1,707		1,540
		Insurance-linked securities	—				—			—		—			—			—		—		—			—		—
			984				—			—		4,718			—			—		—		(3,995		)	1,707		1,540
		Total assets	$	592,856			$	128		$	—	$	19,597		$	(115	)	$	20,790	$	—	$	(20,008	)	$	613,248	$	16,419
		Other liabilities
		Derivative instruments	$	815			$	—		$	—	$	986		$	—		$	—	$	—	$	(1,801	)	$	—	$	—
		Total liabilities	$	815			$	—		$	—	$	986		$	—		$	—	$	—	$	(1,801	)	$	—	$	—
	-1	Gains and losses included in earnings on fixed maturities are included in net realized investment gains (losses). Gains and (losses) included in earnings on other investments are included in net investment income. Gains (losses) on weather derivatives included in earnings are included in other insurance-related income.
	-2	Gains and losses included in other comprehensive income (“OCI”) on fixed maturities are included in unrealized gains (losses) arising during the period.
	-3	Change in unrealized investment gain (loss) relating to assets held at the reporting date.

DERIVATIVE_INSTRUMENTS_TABLES

DERIVATIVE INSTRUMENTS (TABLES)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
LOCATION AND AMOUNTS OF DERIVATIVE FAIR VALUES ON THE CONSOLIDATED BALANCE SHEET	The following table summarizes the balance sheet classification of derivatives recorded at fair values. The notional amount of derivative contracts represents the basis upon which pay or receive amounts are calculated and is presented in the table to quantify the volume of our derivative activities. Notional amounts are not reflective of credit risk.
			March 31, 2015												December 31, 2014
			Derivative				Derivative				Derivative				Derivative				Derivative		Derivative
			Notional				Asset				Liability				Notional				Asset		Liability
			Amount				Fair				Fair				Amount				Fair		Fair
							Value(1)				Value(1)								Value(1)		Value(1)
		Derivatives not designated as hedging instruments
		Relating to investment portfolio:
		Foreign exchange forward contracts	$	235,623			$	3,607			$	40			$	161,678			$	3,925	$	12
		Interest rate swaps	—				—				—				140,000				—		248
		Relating to underwriting portfolio:
		Foreign exchange forward contracts	664,621				643				10,272				577,836				3,228		2,781
		Weather-related contracts	20,995				—				7,308				58,124				111		15,288
		Total derivatives					$	4,250			$	17,620							$	7,264	$	18,329
	-1	Asset and liability derivatives are classified within other assets and other liabilities in the Consolidated Balance Sheets.
RECONCILIATION OF GROSS DERIVATIVE ASSETS AND LIABILITIES TO NET AMOUNTS PRESENTED IN BALANCE SHEETS	The table below presents a reconciliation of our gross derivative assets and liabilities to the net amounts presented in our Consolidated Balance Sheets, with the difference being attributable to the impact of master netting agreements.
			March 31, 2015										December 31, 2014
			Gross Amounts			Gross Amounts Offset			Net				Gross Amounts			Gross Amounts Offset			Net
									Amounts(1)										Amounts(1)
		Derivative assets	$	11,974		$	(7,724	)	$	4,250			$	15,125		$	(7,861	)	$	7,264
		Derivative liabilities	$	25,344		$	(7,724	)	$	17,620			$	26,190		$	(7,861	)	$	18,329
	-1	Net asset and liability derivatives are classified within other assets and other liabilities in the Consolidated Balance Sheets.
NET EARNINGS IMPACT OF FAIR VALUE HEDGES AND TOTAL UNREALIZED AND REALIZED GAINS (LOSSES) ON DERIVATIVES NOT DESIGNATED AS HEDGES RECORDED IN EARNINGS	The total unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges were as follows:
			Location of Gain (Loss) Recognized in Income on Derivative	Three months ended March 31,
				2015				2014
		Derivatives not designated as hedging instruments
		Relating to investment portfolio:
		Foreign exchange forward contracts	Net realized investment gains (losses)	$	6,537			$	(1,328	)
		Interest rate swaps	Net realized investment gains (losses)	(4,006		)		(4,161		)
		Relating to underwriting portfolio:
		Foreign exchange forward contracts	Foreign exchange losses (gains)	(15,273		)		12,074
		Weather-related contracts	Other insurance related income	7,342				3,678
		Total		$	(5,400	)		$	10,263

RESERVE_FOR_LOSSES_AND_LOSS_EX1

RESERVE FOR LOSSES AND LOSS EXPENSES (TABLES)	3 Months Ended
	Mar. 31, 2015
Insurance Loss Reserves [Abstract]
RECONCILIATION OF BEGINNING AND ENDING GROSS RESERVE FOR LOSSES AND LOSS EXPENSES AND NET RESERVE FOR UNPAID LOSSES AND LOSS EXPENSES	The following table presents a reconciliation of our beginning and ending gross reserve for losses and loss expenses and net reserve for unpaid losses and loss expenses for the periods indicated:
		Three months ended March 31,	2015			2014
		Gross reserve for losses and loss expenses, beginning of period	$	9,596,797		$	9,582,140
		Less reinsurance recoverable on unpaid losses, beginning of period	(1,890,280		)	(1,900,112		)
		Net reserve for unpaid losses and loss expenses, beginning of period	7,706,517			7,682,028
		Net incurred losses and loss expenses related to:
		Current year	568,988			587,700
		Prior years	(50,051		)	(43,493		)
			518,937			544,207
		Net paid losses and loss expenses related to:
		Current year	(23,527		)	(13,249		)
		Prior years	(485,315		)	(444,466		)
			(508,842		)	(457,715		)
		Foreign exchange and other	(162,969		)	14,501
		Net reserve for unpaid losses and loss expenses, end of period	7,553,643			7,783,021
		Reinsurance recoverable on unpaid losses, end of period	1,889,579			1,884,820
		Gross reserve for losses and loss expenses, end of period	$	9,443,222		$	9,667,841
NET PRIOR YEAR RESERVE DEVELOPMENT BY SEGMENT	Prior year reserve development arises from changes to loss and loss expense estimates recognized in the current year but relating to losses incurred in previous calendar years. Such development is summarized by segment in the following table:
			Three months ended March 31,
			2015			2014
		Insurance	$	3,361		$	11,608
		Reinsurance	46,690			31,885
		Total	$	50,051		$	43,493

SHAREBASED_COMPENSATION_TABLES

SHARE-BASED COMPENSATION (TABLES)	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
RECONCILIATION OF BEGINNING AND ENDING BALANCE OF NONVESTED RESTRICTED STOCK (INCLUDING RSUS) TO BE SETTLED IN SHARES	The following table provides a reconciliation of the beginning and ending balance of nonvested restricted stock (including restricted stock units) for the three months ended March 31, 2015:
			Performance-based Stock Awards			Service-based Stock Awards
			Number of	Weighted Average		Number of		Weighted Average
			Restricted	Grant Date		Restricted		Grant Date
			Stock	Fair Value		Stock		Fair Value
		Nonvested restricted stock - beginning of period	347	$	37.34	2,768		$	38.7
		Granted	60	51.31		511		51.31
		Vested	—	—		(984	)	36.42
		Forfeited	—	—		(17	)	41.28
		Nonvested restricted stock - end of period	407	$	39.39	2,278		$	42.49

EARNINGS_PER_COMMON_SHARE_TABL

EARNINGS PER COMMON SHARE (TABLES)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
BASIC AND DILUTED EARNINGS PER COMMON SHARE	The following table sets forth the comparison of basic and diluted earnings per common share:
			Three months ended March 31,
			2015			2014
		Basic earnings per common share
		Net income	$	160,952		$	148,471
		Less: Amounts attributable to (from) noncontrolling interests	(4,873		)	1,222
		Less: preferred share dividends	10,022			10,022
		Net income available to common shareholders	155,803			137,227
		Weighted average common shares outstanding - basic	99,910			109,053
		Basic earnings per common share	$	1.56		$	1.26
		Diluted earnings per common share
		Net income available to common shareholders	$	155,803		$	137,227
		Weighted average common shares outstanding - basic	99,910			109,053
		Stock compensation plans	1,229			1,338
		Weighted average common shares outstanding - diluted	101,139			110,391
		Diluted earnings per common share	$	1.54		$	1.24
		Anti-dilutive shares excluded from the dilutive computation	569			1,051

SHAREHOLDERS_EQUITY_TABLES

SHAREHOLDERS' EQUITY (TABLES)	3 Months Ended
	Mar. 31, 2015
Stockholders' Equity Note [Abstract]
COMMON SHARES ISSUED AND OUTSTANDING	The following table presents our common shares issued and outstanding:
			Three months ended March 31,
			2015		2014
		Shares issued, balance at beginning of period	175,478		174,134
		Shares issued	712		1,061
		Total shares issued at end of period	176,190		175,195
		Treasury shares, balance at beginning of period	(76,052	)	(64,649	)
		Shares repurchased	(290	)	(4,036	)
		Shares reissued from treasury	371		235
		Total treasury shares at end of period	(75,971	)	(68,450	)
		Total shares outstanding	100,219		106,745
SHARE REPURCHASES	The following table presents our share repurchases:
			Three months ended March 31,
			2015			2014
		In the open market:
		Total shares	16			3,710
		Total cost	$	832		$	164,606
		Average price per share(1)	$	50.69		$	44.37
		From employees:
		Total shares	274			326
		Total cost	$	13,939		$	14,097
		Average price per share(1)	$	50.97		$	43.14
		Total shares repurchased:
		Total shares	290			4,036
		Total cost	$	14,771		$	178,703
		Average price per share(1)	$	50.95		$	44.27
	-1	Calculated using whole figures.

NONCONTROLLING_INTERESTS_TABLE

NONCONTROLLING INTERESTS (TABLES)	3 Months Ended
	Mar. 31, 2015
Noncontrolling Interest [Abstract]
RECONCILIATION OF BEGINNING AND ENDING BALANCES OF NONCONTROLLING INTEREST	The reconciliation of the beginning and ending balances of the noncontrolling interests in Ventures Re for the periods indicated below was as follows:
		Three months ended March 31,	2015			2014
		Balance at beginning of period	$	58,819		$	50,000
		Increase from issuance of preferred equity to noncontrolling interests	56,991			—
		Decrease from return of capital to noncontrolling interests	(40,000		)	—
		Amounts attributable to (from) noncontrolling interests	(4,873		)	1,222
		Foreign currency translation adjustment attributable to (from) noncontrolling interests	(1,865		)	—
		Balance at end of period	$	69,072		$	51,222

OTHER_COMPREHENSIVE_INCOME_TAB

OTHER COMPREHENSIVE INCOME (TABLES)	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
TAX EFFECTS ALLOCATED TO EACH COMPONENT OF OTHER COMPREHENSIVE INCOME	The tax effects allocated to each component of other comprehensive income were as follows:
			2015											2014
			Before Tax Amount				Tax (Expense) Benefit				Net of Tax Amount			Before Tax Amount			Tax (Expense) Benefit			Net of Tax Amount
		Three months ended March 31,
		Available for sale investments:
		Unrealized gains (losses) arising during the period	$	5,063			$	(10,250	)		$	(5,187	)	$	80,560		$	(9,177	)	$	71,383
		Adjustment for reclassification of net realized investment gains (losses) and OTTI losses recognized in net income	45,098				6				45,104			(16,069		)	6,456			(9,613		)
		Unrealized gains arising during the period, net of reclassification adjustment	50,161				(10,244		)		39,917			64,491			(2,721		)	61,770
		Non-credit portion of OTTI losses	—				—				—			—			—			—
		Foreign currency translation adjustment	(13,278		)		—				(13,278		)	2,659			—			2,659
		Total other comprehensive income, net of tax	$	36,883			$	(10,244	)		$	26,639		$	67,150		$	(2,721	)	$	64,429
RECLASSIFICATIONS OUT OF AOCI INTO NET INCOME AVAILABLE TO COMMON SHAREHOLDERS	Reclassifications out of AOCI into net income available to common shareholders were as follows:
				Amount Reclassified from AOCI(1)
		Details About AOCI Components	Consolidated Statement of Operations Line Item That Includes Reclassification	Three months ended March 31,
				2015				2014
		Unrealized gains (losses) on available for sale investments
			Other realized investment gains (losses)	$	(27,530	)		$	16,855
			OTTI losses	(17,568		)		(786		)
			Total before tax	(45,098		)		16,069
			Income tax expense	(6		)		(6,456		)
			Net of tax	$	(45,104	)		$	9,613
	-1	Amounts in parentheses are debits to net income available to common shareholders.

SEGMENT_INFORMATION_DETAILS

SEGMENT INFORMATION (DETAILS) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
	reportable_segment
Segment Information [Line Items]
Number of reportable segments	2
Net premiums earned	$906,222	$945,949
Other insurance related income	7,676	3,082
Net losses and loss expenses	-518,937	-544,207
Acquisition costs	-171,702	-172,036
General and administrative expenses	-163,517	-152,729
Net investment income	92,110	82,744
Net realized investment gains (losses)	-42,553	10,620
Foreign exchange (losses) gains	63,220	-4,233
Interest expense and financing costs	-12,257	-16,594
Income before income taxes	160,262	152,596
Net loss and loss expense ratio	57.30%	57.50%
Acquisition cost ratio	18.90%	18.20%
General and administrative expense ratio	18.10%	16.20%
Combined ratio	94.30%	91.90%
Goodwill and intangible assets	88,508	90,350	88,960
Operating Segments [Member]
Segment Information [Line Items]
Gross premiums written	1,678,932	1,821,399
Net premiums written	1,463,552	1,664,584
Net premiums earned	906,222	945,949
Other insurance related income	7,676	3,082
Net losses and loss expenses	-518,937	-544,207
Acquisition costs	-171,702	-172,036
General and administrative expenses	-127,345	-124,022
Underwriting income	95,914	108,766
Operating Segments [Member] | Insurance [Member]
Segment Information [Line Items]
Gross premiums written	602,724	601,721
Net premiums written	436,740	456,692
Net premiums earned	447,467	449,214
Other insurance related income	0	0
Net losses and loss expenses	-285,773	-279,423
Acquisition costs	-64,455	-65,057
General and administrative expenses	-87,689	-87,946
Underwriting income	9,550	16,788
Net loss and loss expense ratio	63.90%	62.20%
Acquisition cost ratio	14.40%	14.50%
General and administrative expense ratio	19.60%	19.60%
Combined ratio	97.90%	96.30%
Goodwill and intangible assets	88,508	90,350
Operating Segments [Member] | Reinsurance [Member]
Segment Information [Line Items]
Gross premiums written	1,076,208	1,219,678
Net premiums written	1,026,812	1,207,892
Net premiums earned	458,755	496,735
Other insurance related income	7,676	3,082
Net losses and loss expenses	-233,164	-264,784
Acquisition costs	-107,247	-106,979
General and administrative expenses	-39,656	-36,076
Underwriting income	86,364	91,978
Net loss and loss expense ratio	50.80%	53.30%
Acquisition cost ratio	23.40%	21.50%
General and administrative expense ratio	8.60%	7.30%
Combined ratio	82.80%	82.10%
Goodwill and intangible assets	0	0
Corporate, Non-Segment [Member]
Segment Information [Line Items]
General and administrative expenses	-36,172	-28,707
Significant Reconciling Items [Member]
Segment Information [Line Items]
Net investment income	92,110	82,744
Net realized investment gains (losses)	-42,553	10,620
Foreign exchange (losses) gains	63,220	-4,233
Interest expense and financing costs	($12,257)	($16,594)

INVESTMENTS_DETAILS

INVESTMENTS (DETAILS) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$12,012,633	$12,185,973
Gross Unrealized Gains (fixed maturities)	159,284	116,538
Gross Unrealized Losses (fixed maturities)	-159,023	-173,238
Fair Value (fixed maturities)	12,012,894	12,129,273
Non-credit OTTI in AOCI	-865	-889
Cost	572,317	531,648
Gross Unrealized Gains (equities)	46,224	43,583
Gross Unrealized Losses (equities)	-17,212	-7,524
Fair Value (equities)	601,329	567,707
US Government and Agency [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,490,502	1,645,068
Gross Unrealized Gains (fixed maturities)	9,183	3,337
Gross Unrealized Losses (fixed maturities)	-5,528	-28,328
Fair Value (fixed maturities)	1,494,157	1,620,077
Non-credit OTTI in AOCI	0	0
Non-US Government [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	932,741	1,080,601
Gross Unrealized Gains (fixed maturities)	7,041	7,383
Gross Unrealized Losses (fixed maturities)	-66,685	-54,441
Fair Value (fixed maturities)	873,097	1,033,543
Non-credit OTTI in AOCI	0	0
Corporate Debt [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	4,549,974	4,386,432
Gross Unrealized Gains (fixed maturities)	58,133	40,972
Gross Unrealized Losses (fixed maturities)	-73,829	-66,280
Fair Value (fixed maturities)	4,534,278	4,361,124
Non-credit OTTI in AOCI	0	0
Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	2,150,598	2,241,581
Gross Unrealized Gains (fixed maturities)	51,061	40,762
Gross Unrealized Losses (fixed maturities)	-1,416	-4,235
Fair Value (fixed maturities)	2,200,243	2,278,108
Non-credit OTTI in AOCI	0	0
CMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,111,327	1,085,618
Gross Unrealized Gains (fixed maturities)	21,219	13,289
Gross Unrealized Losses (fixed maturities)	-1,223	-2,019
Fair Value (fixed maturities)	1,131,323	1,096,888
Non-credit OTTI in AOCI	0	0
Non-Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	77,185	71,236
Gross Unrealized Gains (fixed maturities)	2,560	2,765
Gross Unrealized Losses (fixed maturities)	-1,744	-915
Fair Value (fixed maturities)	78,001	73,086
Non-credit OTTI in AOCI	-865	-889
ABS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,500,493	1,475,026
Gross Unrealized Gains (fixed maturities)	3,438	2,748
Gross Unrealized Losses (fixed maturities)	-8,102	-16,188
Fair Value (fixed maturities)	1,495,829	1,461,586
Non-credit OTTI in AOCI	0	0
Municipals [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	199,813	200,411
Gross Unrealized Gains (fixed maturities)	6,649	5,282
Gross Unrealized Losses (fixed maturities)	-496	-832
Fair Value (fixed maturities)	205,966	204,861
Non-credit OTTI in AOCI	0	0
Exchange-Traded Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	453,978	416,063
Gross Unrealized Gains (equities)	46,224	43,583
Gross Unrealized Losses (equities)	-2,155	-4,756
Fair Value (equities)	498,047	454,890
Non-U.S. Bond Mutual Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	118,339	115,585
Gross Unrealized Gains (equities)	0	0
Gross Unrealized Losses (equities)	-15,057	-2,768
Fair Value (equities)	$103,282	$112,817

INVESTMENTS_DETAILS_2

INVESTMENTS (DETAILS 2) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Schedule Of Available For Sale Securities [Line Items]
Due in one year or less (amortized cost)	$508,448	$424,077
Due after one year through five years (amortized cost)	4,387,194	4,925,780
Due after five years through ten years (amortized cost)	2,042,045	1,755,248
Due after ten years (amortized cost)	235,343	207,407
Total fixed maturities with a single maturity date (amortized cost)	7,173,030	7,312,512
Total (amortized cost)	12,012,633	12,185,973
Due in one year or less (fair value)	503,179	423,265
Due after one year through five years (fair value)	4,349,800	4,892,411
Due after five years through ten years (fair value)	2,016,713	1,695,641
Due after ten years (fair value)	237,806	208,288
Total fixed maturities with a single maturity date (fair value)	7,107,498	7,219,605
Fair Value (fixed maturities)	12,012,894	12,129,273
Due in one year or less (% of total fair value)	4.20%	3.50%
Due after one year through five years (% of total fair value)	36.20%	40.30%
Due after five years through ten years (% of total fair value)	16.80%	14.00%
Due after ten years (% of total fair value)	2.00%	1.70%
Fixed maturities with a single maturity date (% of total fair value)	59.20%	59.50%
Total	100.00%	100.00%
Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities without a single maturity date (amortized cost)	2,150,598	2,241,581
Total (amortized cost)	2,150,598	2,241,581
Fixed maturities without a single maturity date (fair value)	2,200,243	2,278,108
Fair Value (fixed maturities)	2,200,243	2,278,108
Fixed maturities without a single maturity date (% of total fair value)	18.30%	18.80%
CMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities without a single maturity date (amortized cost)	1,111,327	1,085,618
Total (amortized cost)	1,111,327	1,085,618
Fixed maturities without a single maturity date (fair value)	1,131,323	1,096,888
Fair Value (fixed maturities)	1,131,323	1,096,888
Fixed maturities without a single maturity date (% of total fair value)	9.40%	9.00%
Non-Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities without a single maturity date (amortized cost)	77,185	71,236
Total (amortized cost)	77,185	71,236
Fixed maturities without a single maturity date (fair value)	78,001	73,086
Fair Value (fixed maturities)	78,001	73,086
Fixed maturities without a single maturity date (% of total fair value)	0.60%	0.60%
ABS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fixed maturities without a single maturity date (amortized cost)	1,500,493	1,475,026
Total (amortized cost)	1,500,493	1,475,026
Fixed maturities without a single maturity date (fair value)	1,495,829	1,461,586
Fair Value (fixed maturities)	$1,495,829	$1,461,586
Fixed maturities without a single maturity date (% of total fair value)	12.50%	12.10%

INVESTMENTS_DETAILS_3

INVESTMENTS (DETAILS 3) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified	security	security
Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	$840,063	$1,354,213
Unrealized Losses - 12 months or greater	-50,863	-71,302
Fair Value - Less than 12 months	2,874,820	4,801,110
Unrealized Losses - Less than 12 months	-108,160	-101,936
Total Fair Value of Securities in Unrealized Loss Position	3,714,883	6,155,323
Total Unrealized Losses	-159,023	-173,238
Number of Available For Sale Securities In Unrealized Loss Positions	1,004	1,388
Number of Available For Sale Securities in Unrealized Loss Positions for 12 Months or Greater	180	223
Fixed Maturities [Member] | Below Investment Grade or Not Rated [Member]
Schedule Of Available For Sale Securities [Line Items]
Total Unrealized Losses	-17,000	-36,000
US Government and Agency [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	94,248	388,551
Unrealized Losses - 12 months or greater	-4,525	-24,319
Fair Value - Less than 12 months	329,487	786,850
Unrealized Losses - Less than 12 months	-1,003	-4,009
Total Fair Value of Securities in Unrealized Loss Position	423,735	1,175,401
Total Unrealized Losses	-5,528	-28,328
Non-US Government [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	112,581	143,602
Unrealized Losses - 12 months or greater	-31,924	-29,171
Fair Value - Less than 12 months	349,284	435,670
Unrealized Losses - Less than 12 months	-34,761	-25,270
Total Fair Value of Securities in Unrealized Loss Position	461,865	579,272
Total Unrealized Losses	-66,685	-54,441
Corporate Debt [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	53,901	26,708
Unrealized Losses - 12 months or greater	-5,679	-2,221
Fair Value - Less than 12 months	1,263,181	2,199,672
Unrealized Losses - Less than 12 months	-68,150	-64,059
Total Fair Value of Securities in Unrealized Loss Position	1,317,082	2,226,380
Total Unrealized Losses	-73,829	-66,280
Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	55,492	259,914
Unrealized Losses - 12 months or greater	-748	-3,084
Fair Value - Less than 12 months	208,699	333,288
Unrealized Losses - Less than 12 months	-668	-1,151
Total Fair Value of Securities in Unrealized Loss Position	264,191	593,202
Total Unrealized Losses	-1,416	-4,235
CMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	54,293	68,624
Unrealized Losses - 12 months or greater	-719	-925
Fair Value - Less than 12 months	145,716	256,225
Unrealized Losses - Less than 12 months	-504	-1,094
Total Fair Value of Securities in Unrealized Loss Position	200,009	324,849
Total Unrealized Losses	-1,223	-2,019
Non-Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	5,685	6,689
Unrealized Losses - 12 months or greater	-762	-613
Fair Value - Less than 12 months	17,917	13,442
Unrealized Losses - Less than 12 months	-982	-302
Total Fair Value of Securities in Unrealized Loss Position	23,602	20,131
Total Unrealized Losses	-1,744	-915
ABS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	449,335	425,663
Unrealized Losses - 12 months or greater	-6,367	-10,325
Fair Value - Less than 12 months	544,239	750,679
Unrealized Losses - Less than 12 months	-1,735	-5,863
Total Fair Value of Securities in Unrealized Loss Position	993,574	1,176,342
Total Unrealized Losses	-8,102	-16,188
Municipals [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	14,528	34,462
Unrealized Losses - 12 months or greater	-139	-644
Fair Value - Less than 12 months	16,297	25,284
Unrealized Losses - Less than 12 months	-357	-188
Total Fair Value of Securities in Unrealized Loss Position	30,825	59,746
Total Unrealized Losses	-496	-832
Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	0	0
Unrealized Losses - 12 months or greater	0	0
Fair Value - Less than 12 months	183,512	204,092
Unrealized Losses - Less than 12 months	-17,212	-7,524
Total Fair Value of Securities in Unrealized Loss Position	183,512	204,092
Total Unrealized Losses	-17,212	-7,524
Number of Available For Sale Securities In Unrealized Loss Positions	8	9
Number of Available For Sale Securities in Unrealized Loss Positions for 12 Months or Greater	0	0
Exchange-Traded Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	0	0
Unrealized Losses - 12 months or greater	0	0
Fair Value - Less than 12 months	80,230	91,275
Unrealized Losses - Less than 12 months	-2,155	-4,756
Total Fair Value of Securities in Unrealized Loss Position	80,230	91,275
Total Unrealized Losses	-2,155	-4,756
Non-U.S. Bond Mutual Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	0	0
Unrealized Losses - 12 months or greater	0	0
Fair Value - Less than 12 months	103,282	112,817
Unrealized Losses - Less than 12 months	-15,057	-2,768
Total Fair Value of Securities in Unrealized Loss Position	103,282	112,817
Total Unrealized Losses	($15,057)	($2,768)

INVESTMENTS_DETAILS_4

INVESTMENTS (DETAILS 4) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Investments [Line Items]
Other investments	$939,006,000	$965,465,000
Percentage of total fair value	100.00%	100.00%
Hedge Funds [Member] | Lockup Redemption Restriction [Member]
Other Investments [Line Items]
Fair value of other investments subject to redemption restrictions	95,000,000	87,000,000
Percentage of fair value of other investments subject to redemption restrictions	12.00%	11.00%
Hedge Funds [Member] | Other Redemption Restriction [Member]
Other Investments [Line Items]
Fair value of other investments subject to redemption restrictions	6,000,000	6,000,000
Long/short equity funds [Member]
Other Investments [Line Items]
Other investments	242,096,000	298,907,000
Percentage of total fair value	26.00%	31.00%
Redemption frequency	Quarterly, Semi-annually	Quarterly, Semi-annually
Long/short equity funds [Member] | Minimum [Member]
Other Investments [Line Items]
Redemption notice period	30 days	30 days
Long/short equity funds [Member] | Maximum [Member]
Other Investments [Line Items]
Redemption notice period	60 days	60 days
Multi-strategy funds [Member]
Other Investments [Line Items]
Other investments	336,342,000	324,020,000
Percentage of total fair value	36.00%	34.00%
Redemption frequency	Quarterly, Semi-annually	Quarterly, Semi-annually
Optional extension of investment term	3 years
Multi-strategy funds [Member] | Other Redemption Restriction [Member]
Other Investments [Line Items]
Unfunded commitments related to other investments	29,000,000		60,000,000
Multi-strategy funds [Member] | Minimum [Member]
Other Investments [Line Items]
Redemption notice period	60 days	60 days
Multi-strategy funds [Member] | Maximum [Member]
Other Investments [Line Items]
Redemption notice period	95 days	95 days
Event driven funds [Member]
Other Investments [Line Items]
Other investments	189,212,000	185,899,000
Percentage of total fair value	20.00%	19.00%
Redemption frequency	Quarterly, Annually	Quarterly, Annually
Event driven funds [Member] | Minimum [Member]
Other Investments [Line Items]
Redemption notice period	45 days	45 days
Event driven funds [Member] | Maximum [Member]
Other Investments [Line Items]
Redemption notice period	60 days	60 days
Leveraged bank loan funds [Member]
Other Investments [Line Items]
Other investments	9,616,000	9,713,000
Percentage of total fair value	1.00%	1.00%
Redemption frequency	Quarterly	Quarterly
Redemption notice period	65 days	65 days
Direct Lending Funds [Member]
Other Investments [Line Items]
Other investments	69,682,000	54,438,000
Percentage of total fair value	7.00%	6.00%
Optional extension of investment term	3 years
Direct Lending Funds [Member] | Other Redemption Restriction [Member]
Other Investments [Line Items]
Fair value of other investments subject to redemption restrictions	69,682,000	54,438,000
Percentage of fair value of other investments subject to redemption restrictions	7.00%	6.00%
Unfunded commitments related to other investments	72,000,000	88,000,000
Direct Lending Funds [Member] | Minimum [Member]
Other Investments [Line Items]
Investment term	5 years
Direct Lending Funds [Member] | Maximum [Member]
Other Investments [Line Items]
Investment term	10 years
CLO-Equities [Member]
Other Investments [Line Items]
Other investments	92,058,000	92,488,000
Percentage of total fair value	10.00%	9.00%
Real estate funds [Member]
Other Investments [Line Items]
Investment term	8 years
Real estate funds [Member] | Other Redemption Restriction [Member]
Other Investments [Line Items]
Unfunded commitments related to other investments	$100,000,000
Commitment period	3 years

INVESTMENTS_DETAILS_5

INVESTMENTS (DETAILS 5) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Net Investment Income [Line Items]
Gross investment income	$99,883	$93,080
Investment expenses	-7,773	-10,336
Net investment income	92,110	82,744
Fixed Maturities [Member]
Net Investment Income [Line Items]
Gross investment income	66,101	72,957
Other Investments [Member]
Net Investment Income [Line Items]
Gross investment income	30,935	16,760
Equity Securities [Member]
Net Investment Income [Line Items]
Gross investment income	1,676	2,286
Cash And Cash Equivalents [Member]
Net Investment Income [Line Items]
Gross investment income	1,102	863
Short-term Investments [Member]
Net Investment Income [Line Items]
Gross investment income	$69	$214

INVESTMENTS_DETAILS_6

INVESTMENTS (DETAILS 6) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Gross realized gains	$15,699	$53,037
Gross realized losses	-43,215	-36,142
Net OTTI recognized in earnings	-17,568	-786
Change in fair value of investment derivatives	2,531	-5,489
Total net realized investment gains (losses)	-42,553	10,620
Fixed Maturities And Short-Term Investments [Member]
Schedule Of Available For Sale Securities [Line Items]
Gross realized gains	15,661	33,770
Gross realized losses	-43,091	-33,704
Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Gross realized gains	38	19,267
Gross realized losses	($124)	($2,438)

INVESTMENTS_DETAILS_7

INVESTMENTS (DETAILS 7) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net [Line Items]
Total OTTI recognized in earnings	$17,568	$786
Fixed Maturities [Member]
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net [Line Items]
Total OTTI recognized in earnings	17,568	109
Non-US Government [Member]
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net [Line Items]
Total OTTI recognized in earnings	1,422	38
Corporate Debt [Member]
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net [Line Items]
Total OTTI recognized in earnings	16,120	15
Non-Agency RMBS [Member]
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net [Line Items]
Total OTTI recognized in earnings	4	0
ABS [Member]
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net [Line Items]
Total OTTI recognized in earnings	22	56
Equity Securities [Member]
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net [Line Items]
Total OTTI recognized in earnings	0	677
Common Stock [Member]
Other Than Temporary Impairment Losses Investments Portion Recognized In Earnings Net [Line Items]
Total OTTI recognized in earnings	$0	$677

INVESTMENTS_DETAILS_8

INVESTMENTS (DETAILS 8) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Credit Losses For Which a Portion of OTTI Was Recognized in AOCI [Roll Forward]
Balance at beginning of period	$1,531	$1,594
Credit impairments recognized on securities not previously impaired	0	0
Additional credit impairments recognized on securities previously impaired	10	0
Change in timing of future cash flows on securities previously impaired	0	0
Intent to sell of securities previously impaired	0	0
Securities sold/redeemed/matured	0	-4
Balance at end of period	$1,541	$1,590

INVESTMENTS_DETAILS_9

INVESTMENTS (DETAILS 9) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Investments, Debt and Equity Securities [Abstract]
Value of reverse repurchase agreements	$123	$110
Minimum required collateral for reverse repurchase agreements, expressed as a percentage of loan principal	102.00%

FAIR_VALUE_MEASUREMENTS_DETAIL

FAIR VALUE MEASUREMENTS (DETAILS) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	$12,012,894	$12,129,273
Equity securities	601,329	567,707
Other investments	939,006	965,465
Short-term investments	38,373	107,534
Derivative instruments (see Note 5)	4,250	7,264
Derivative instruments (see Note 5)	17,620	18,329
Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	12,012,894	12,129,273
Equity securities	601,329	567,707
Other investments	939,006	965,465
Short-term investments	38,373	107,534
Derivative instruments (see Note 5)	4,250	7,264
Insurance-linked securities	25,000	0
Total Assets	13,620,852	13,777,243
Derivative instruments (see Note 5)	17,620	18,329
Cash settled awards (see Note 7)	12,641	20,518
Total Liabilities	30,261	38,847
US Government and Agency [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	1,494,157	1,620,077
US Government and Agency [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	1,494,157	1,620,077
Non-US Government [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	873,097	1,033,543
Non-US Government [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	873,097	1,033,543
Corporate Debt [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	4,534,278	4,361,124
Corporate Debt [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	4,534,278	4,361,124
Agency RMBS [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	2,200,243	2,278,108
Agency RMBS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	2,200,243	2,278,108
CMBS [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	1,131,323	1,096,888
CMBS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	1,131,323	1,096,888
Non-Agency RMBS [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	78,001	73,086
Non-Agency RMBS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	78,001	73,086
ABS [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	1,495,829	1,461,586
ABS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	1,495,829	1,461,586
Municipals [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	205,966	204,861
Municipals [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	205,966	204,861
Exchange-Traded Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	498,047	454,890
Exchange-Traded Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	498,047	454,890
Non-U.S. Bond Mutual Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	103,282	112,817
Non-U.S. Bond Mutual Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	103,282	112,817
Hedge Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other investments	777,266	818,539
Direct Lending Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other investments	69,682	54,438
CLO-Equities [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other investments	92,058	92,488
Level 1 [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	1,400,810	1,497,922
Equity securities	498,047	454,890
Other investments	0	0
Short-term investments	0	0
Derivative instruments (see Note 5)	0	0
Insurance-linked securities	0	0
Total Assets	1,898,857	1,952,812
Derivative instruments (see Note 5)	0	0
Cash settled awards (see Note 7)	0	0
Total Liabilities	0	0
Level 1 [Member] | US Government and Agency [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	1,400,810	1,497,922
Level 1 [Member] | Non-US Government [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	0	0
Level 1 [Member] | Corporate Debt [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	0	0
Level 1 [Member] | Agency RMBS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	0	0
Level 1 [Member] | CMBS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	0	0
Level 1 [Member] | Non-Agency RMBS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	0	0
Level 1 [Member] | ABS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	0	0
Level 1 [Member] | Municipals [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	0	0
Level 1 [Member] | Exchange-Traded Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	498,047	454,890
Level 1 [Member] | Non-U.S. Bond Mutual Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	0	0
Level 1 [Member] | Hedge Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other investments	0	0
Level 1 [Member] | Direct Lending Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other investments	0	0
Level 1 [Member] | CLO-Equities [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other investments	0	0
Level 2 [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	10,528,245	10,557,720
Equity securities	103,282	112,817
Other investments	281,417	347,621
Short-term investments	38,373	107,534
Derivative instruments (see Note 5)	4,250	7,153
Insurance-linked securities	0	0
Total Assets	10,955,567	11,132,845
Derivative instruments (see Note 5)	10,312	3,041
Cash settled awards (see Note 7)	12,641	20,518
Total Liabilities	22,953	23,559
Level 2 [Member] | US Government and Agency [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	93,347	122,155
Level 2 [Member] | Non-US Government [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	873,097	1,033,543
Level 2 [Member] | Corporate Debt [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	4,507,421	4,345,287
Level 2 [Member] | Agency RMBS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	2,200,243	2,278,108
Level 2 [Member] | CMBS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	1,114,262	1,079,125
Level 2 [Member] | Non-Agency RMBS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	78,001	73,086
Level 2 [Member] | ABS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	1,455,908	1,421,555
Level 2 [Member] | Municipals [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	205,966	204,861
Level 2 [Member] | Exchange-Traded Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	0	0
Level 2 [Member] | Non-U.S. Bond Mutual Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	103,282	112,817
Level 2 [Member] | Hedge Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other investments	281,417	347,621
Level 2 [Member] | Direct Lending Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other investments	0	0
Level 2 [Member] | CLO-Equities [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other investments	0	0
Level 3 [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	83,839	73,631
Equity securities	0	0
Other investments	657,589	617,844
Short-term investments	0	0
Derivative instruments (see Note 5)	0	111
Insurance-linked securities	25,000	0
Total Assets	766,428	691,586
Derivative instruments (see Note 5)	7,308	15,288
Cash settled awards (see Note 7)	0	0
Total Liabilities	7,308	15,288
Level 3 [Member] | US Government and Agency [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	0	0
Level 3 [Member] | Non-US Government [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	0	0
Level 3 [Member] | Corporate Debt [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	26,857	15,837
Level 3 [Member] | Agency RMBS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	0	0
Level 3 [Member] | CMBS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	17,061	17,763
Level 3 [Member] | Non-Agency RMBS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	0	0
Level 3 [Member] | ABS [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	39,921	40,031
Level 3 [Member] | Municipals [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fixed maturities	0	0
Level 3 [Member] | Exchange-Traded Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	0	0
Level 3 [Member] | Non-U.S. Bond Mutual Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	0	0
Level 3 [Member] | Hedge Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other investments	495,849	470,918
Level 3 [Member] | Direct Lending Funds [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other investments	69,682	54,438
Level 3 [Member] | CLO-Equities [Member] | Fair Value Measurements Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Other investments	$92,058	$92,488

FAIR_VALUE_MEASUREMENTS_DETAIL1

FAIR VALUE MEASUREMENTS (DETAILS 2) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair Value Inputs Assets Quantitative Information [Line Items]
Fixed maturities	$12,012,894	$12,129,273
Other investments	939,006	965,465
Discounted cash flow [Member] | Level 3 [Member] | Other Investments - CLO-Equities [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Other investments	36,960
Loss severity rate	53.50%
Simulation model [Member] | Level 3 [Member] | Weather Related Derivative [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Net derivative assets	($7,308)
Minimum [Member] | Discounted cash flow [Member] | Level 3 [Member] | Other Investments - CLO-Equities [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Default rates	4.00%
Collateral spreads	3.00%
Estimated maturity dates	2 years 10 months 29 days
Minimum [Member] | Simulation model [Member] | Level 3 [Member] | Weather Related Derivative [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Weather curve	632
Weather standard deviation	59
Maximum [Member] | Discounted cash flow [Member] | Level 3 [Member] | Other Investments - CLO-Equities [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Default rates	5.00%
Collateral spreads	3.50%
Estimated maturity dates	4 years 1 month 6 days
Maximum [Member] | Simulation model [Member] | Level 3 [Member] | Weather Related Derivative [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Weather curve	2,161
Weather standard deviation	250
Weighted Average [Member] | Discounted cash flow [Member] | Level 3 [Member] | Other Investments - CLO-Equities [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Default rates	4.30%
Loss severity rate	53.50%
Collateral spreads	3.30%
Estimated maturity dates	3 years 7 months 9 days

FAIR_VALUE_MEASUREMENTS_DETAIL2

FAIR VALUE MEASUREMENTS (DETAILS 3) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Fixed Maturities [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	$73,631	$34,817
Transfers into Level 3	0	128
Transfers out of Level 3	0	0
Included in earnings	0	0
Included in OCI	38	-115
Purchases	10,910	0
Sales	0	0
Settlements/ Distributions	-740	-137
Balance at end of period	83,839	34,693
Change in unrealized investment gain/loss relating to assets held at the reporting date	0	0
Other Investments [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	617,844	557,055
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in earnings	25,685	14,879
Included in OCI	0	0
Purchases	21,418	20,790
Sales	0	0
Settlements/ Distributions	-7,358	-15,876
Balance at end of period	657,589	576,848
Change in unrealized investment gain/loss relating to assets held at the reporting date	25,685	14,879
Other Assets [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	111	984
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in earnings	-1,067	4,718
Included in OCI	0	0
Purchases	25,000	0
Sales	0	0
Settlements/ Distributions	956	-3,995
Balance at end of period	25,000	1,707
Change in unrealized investment gain/loss relating to assets held at the reporting date	0	1,540
Total Assets [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	691,586	592,856
Transfers into Level 3	0	128
Transfers out of Level 3	0	0
Included in earnings	24,618	19,597
Included in OCI	38	-115
Purchases	57,328	20,790
Sales	0	0
Settlements/ Distributions	-7,142	-20,008
Balance at end of period	766,428	613,248
Change in unrealized investment gain/loss relating to assets held at the reporting date	25,685	16,419
Total Liabilities [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	15,288	815
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in earnings	-8,551	986
Included in OCI	0	0
Purchases	1,082	0
Sales	0	0
Settlements/ Distributions	-511	-1,801
Balance at end of period	7,308	0
Change in unrealized investment gain/loss relating to assets held at the reporting date	-2,058	0
Corporate Debt [Member] | Fixed Maturities [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	15,837	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in earnings	0	0
Included in OCI	180	0
Purchases	10,910	0
Sales	0	0
Settlements/ Distributions	-70	0
Balance at end of period	26,857	0
Change in unrealized investment gain/loss relating to assets held at the reporting date	0	0
CMBS [Member] | Fixed Maturities [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	17,763	4,018
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in earnings	0	0
Included in OCI	-204	-20
Purchases	0	0
Sales	0	0
Settlements/ Distributions	-498	-29
Balance at end of period	17,061	3,969
Change in unrealized investment gain/loss relating to assets held at the reporting date	0	0
ABS [Member] | Fixed Maturities [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	40,031	30,799
Transfers into Level 3	0	128
Transfers out of Level 3	0	0
Included in earnings	0	0
Included in OCI	62	-95
Purchases	0	0
Sales	0	0
Settlements/ Distributions	-172	-108
Balance at end of period	39,921	30,724
Change in unrealized investment gain/loss relating to assets held at the reporting date	0	0
Hedge Funds [Member] | Other Investments [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	470,918	461,055
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in earnings	18,931	8,177
Included in OCI	0	0
Purchases	6,000	4,500
Sales	0	0
Settlements/ Distributions	0	-9,066
Balance at end of period	495,849	464,666
Change in unrealized investment gain/loss relating to assets held at the reporting date	18,931	8,177
Direct Lending Funds [Member] | Other Investments [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	54,438	22,134
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in earnings	667	552
Included in OCI	0	0
Purchases	15,418	3,445
Sales	0	0
Settlements/ Distributions	-841	-128
Balance at end of period	69,682	26,003
Change in unrealized investment gain/loss relating to assets held at the reporting date	667	552
CLO-Equities [Member] | Other Investments [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	92,488	73,866
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in earnings	6,087	6,150
Included in OCI	0	0
Purchases	0	12,845
Sales	0	0
Settlements/ Distributions	-6,517	-6,682
Balance at end of period	92,058	86,179
Change in unrealized investment gain/loss relating to assets held at the reporting date	6,087	6,150
Derivative [Member] | Other Assets [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	111	984
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in earnings	-1,067	4,718
Included in OCI	0	0
Purchases	0	0
Sales	0	0
Settlements/ Distributions	956	-3,995
Balance at end of period	0	1,707
Change in unrealized investment gain/loss relating to assets held at the reporting date	0	1,540
Derivative [Member] | Other Liabilities [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	15,288	815
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in earnings	-8,551	986
Included in OCI	0	0
Purchases	1,082	0
Sales	0	0
Settlements/ Distributions	-511	-1,801
Balance at end of period	7,308	0
Change in unrealized investment gain/loss relating to assets held at the reporting date	-2,058	0
Insurance-linked securities [Member] | Other Assets [Member]
Changes in Level 3 Financial Instruments Measured at Fair Value on a Recurring Basis [Line Items]
Balance at beginning of period	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Included in earnings	0	0
Included in OCI	0	0
Purchases	25,000	0
Sales	0	0
Settlements/ Distributions	0	0
Balance at end of period	25,000	0
Change in unrealized investment gain/loss relating to assets held at the reporting date	$0	$0

FAIR_VALUE_MEASUREMENTS_DETAIL3

FAIR VALUE MEASUREMENTS (DETAILS 4) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Senior notes	$991,045	$990,790
Estimate Of Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Senior notes	$1,133,000	$1,089,000

DERIVATIVE_INSTRUMENTS_DETAILS

DERIVATIVE INSTRUMENTS (DETAILS) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Asset Derivative Fair Value	$4,250	$7,264
Liability Derivative Fair Value	17,620	18,329
Other Assets [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Asset Derivative Fair Value	4,250	7,264
Other Liabilities [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Liability Derivative Fair Value	17,620	18,329
Investment Portfolio [Member] | Foreign Exchange Forward Contracts [Member] | Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Notional Amount	235,623	161,678
Investment Portfolio [Member] | Foreign Exchange Forward Contracts [Member] | Other Assets [Member] | Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Asset Derivative Fair Value	3,607	3,925
Investment Portfolio [Member] | Foreign Exchange Forward Contracts [Member] | Other Liabilities [Member] | Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Liability Derivative Fair Value	40	12
Investment Portfolio [Member] | Interest Rate Swap [Member] | Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Notional Amount	0	140,000
Investment Portfolio [Member] | Interest Rate Swap [Member] | Other Assets [Member] | Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Asset Derivative Fair Value	0	0
Investment Portfolio [Member] | Interest Rate Swap [Member] | Other Liabilities [Member] | Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Liability Derivative Fair Value	0	248
Underwriting Portfolio [Member] | Foreign Exchange Forward Contracts [Member] | Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Notional Amount	664,621	577,836
Underwriting Portfolio [Member] | Foreign Exchange Forward Contracts [Member] | Other Assets [Member] | Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Asset Derivative Fair Value	643	3,228
Underwriting Portfolio [Member] | Foreign Exchange Forward Contracts [Member] | Other Liabilities [Member] | Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Liability Derivative Fair Value	10,272	2,781
Underwriting Portfolio [Member] | Weather Related Derivative [Member] | Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Derivative Notional Amount	20,995	58,124
Underwriting Portfolio [Member] | Weather Related Derivative [Member] | Other Assets [Member] | Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Asset Derivative Fair Value	0	111
Underwriting Portfolio [Member] | Weather Related Derivative [Member] | Other Liabilities [Member] | Not Designated as Hedging Instruments [Member]
Derivative Fair Values on Consolidated Balance Sheet [Line Items]
Liability Derivative Fair Value	$7,308	$15,288

DERIVATIVE_INSTRUMENTS_DETAILS1

DERIVATIVE INSTRUMENTS (DETAILS 2) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative assets - gross amounts	$11,974	$15,125
Derivative assets - gross amounts offset	-7,724	-7,861
Asset Derivative Fair Value	4,250	7,264
Derivative liabilities - gross amounts	25,344	26,190
Derivative liabilities - gross amounts offset	-7,724	-7,861
Liability Derivative Fair Value	$17,620	$18,329

DERIVATIVE_INSTRUMENTS_DETAILS2

DERIVATIVE INSTRUMENTS (DETAILS 3) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Unrealized and Realized Gains (Losses) Recognized in Earnings for Derivatives Not Designated As Hedges [Line Items]
Unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges	($5,400)	$10,263
Investment Portfolio [Member] | Foreign Exchange Forward Contracts [Member] | Net Realized Investment Gains (Losses) [Member]
Unrealized and Realized Gains (Losses) Recognized in Earnings for Derivatives Not Designated As Hedges [Line Items]
Unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges	6,537	-1,328
Investment Portfolio [Member] | Interest Rate Swap [Member] | Net Realized Investment Gains (Losses) [Member]
Unrealized and Realized Gains (Losses) Recognized in Earnings for Derivatives Not Designated As Hedges [Line Items]
Unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges	-4,006	-4,161
Underwriting Portfolio [Member] | Foreign Exchange Forward Contracts [Member] | Foreign Exchange Gains (Losses) [Member]
Unrealized and Realized Gains (Losses) Recognized in Earnings for Derivatives Not Designated As Hedges [Line Items]
Unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges	-15,273	12,074
Underwriting Portfolio [Member] | Weather Related Derivative [Member] | Other Insurance Related Income [Member]
Unrealized and Realized Gains (Losses) Recognized in Earnings for Derivatives Not Designated As Hedges [Line Items]
Unrealized and realized gains (losses) recognized in earnings for derivatives not designated as hedges	$7,342	$3,678

RESERVE_FOR_LOSSES_AND_LOSS_EX2

RESERVE FOR LOSSES AND LOSS EXPENSES (DETAILS) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Reconciliation of Beginning and Ending Gross Unpaid Losses and Loss Expenses
Gross reserve for losses and loss expenses, beginning of period	$9,596,797	$9,582,140
Less reinsurance recoverable on unpaid losses, beginning of period	-1,890,280	-1,900,112
Net reserve for unpaid losses and loss expenses, beginning of period	7,706,517	7,682,028
Net incurred losses and loss expenses related to:
Current year	568,988	587,700
Prior years	-50,051	-43,493
Net incurred losses and loss expenses	518,937	544,207
Net paid losses and loss expenses related to:
Current year	-23,527	-13,249
Prior years	-485,315	-444,466
Net paid losses and loss expenses	-508,842	-457,715
Foreign exchange and other	-162,969	14,501
Net reserve for unpaid losses and loss expenses, end of period	7,553,643	7,783,021
Reinsurance recoverable on unpaid losses, end of period	1,889,579	1,884,820
Gross reserve for losses and loss expenses, end of period	$9,443,222	$9,667,841

RESERVE_FOR_LOSSES_AND_LOSS_EX3

RESERVE FOR LOSSES AND LOSS EXPENSES (DETAILS 2) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Net Favorable Prior Year Reserve Development [Line Items]
Net favorable prior year reserve development	$50,051	$43,493
Insurance [Member]
Net Favorable Prior Year Reserve Development [Line Items]
Net favorable prior year reserve development	3,361	11,608
Reinsurance [Member]
Net Favorable Prior Year Reserve Development [Line Items]
Net favorable prior year reserve development	$46,690	$31,885

RESERVE_FOR_LOSSES_AND_LOSS_EX4

RESERVE FOR LOSSES AND LOSS EXPENSES (DETAILS 3) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	$50,051	$43,493
Short Tail Lines Insurance And Reinsurance Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	28,000	29,000
Professional Lines Reinsurance Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	20,000	6,000
Insurance Credit And Political Risk [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	-11,000
Liability Reinsurance Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	12,000	6,000
Liability Insurance Business [Member]
Additional Information Related to Net Incurred Losses [Line Items]
Net favorable (adverse) prior year reserve development	($11,000)

SHAREBASED_COMPENSATION_DETAIL

SHARE-BASED COMPENSATION (DETAILS) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Reconcilation of Beginning and Ending Balance of Nonvested Restricted Stock (including RSUs) [Abstract]
Share based compensation expense incurred	$19,000,000	$17,000,000
Tax benefit related to share-based compensation costs incurred	4,000,000	3,000,000
Fair value - vested during period	63,000,000	61,000,000
Unrecognized share-based compensation costs	148,000,000
Unrecognized share-based compensation costs - weighted average period expected to be recognized	2 years 7 months 24 days
Performance Shares [Member]
Reconcilation of Beginning and Ending Balance of Nonvested Restricted Stock (including RSUs) [Roll Forward]
Nonvested restricted stock (number) - beginning of period	347,000
Granted (number)	60,000
Vested (number)	0
Forfeited (number)	0
Nonvested restricted stock (number) - end of period	407,000
Reconcilation of Beginning and Ending Balance of Nonvested Restricted Stock (including RSUs) [Abstract]
Weighted average grant date fair value - beginning of period	$37.34
Weighted average grant date fair value - granted	$51.31
Weighted average grant date fair value - vested	$0
Weighted average grant date fair value - forfeited	$0
Weighted average grant date fair value - end of period	$39.39
Number of restricted stock and restricted stock units granted which will settle in cash	18,659
Service Based Restricted Stock And Restricted Stock Units [Member]
Reconcilation of Beginning and Ending Balance of Nonvested Restricted Stock (including RSUs) [Roll Forward]
Nonvested restricted stock (number) - beginning of period	2,768,000
Granted (number)	511,000
Vested (number)	-984,000
Forfeited (number)	-17,000
Nonvested restricted stock (number) - end of period	2,278,000
Reconcilation of Beginning and Ending Balance of Nonvested Restricted Stock (including RSUs) [Abstract]
Weighted average grant date fair value - beginning of period	$38.70
Weighted average grant date fair value - granted	$51.31
Weighted average grant date fair value - vested	$36.42
Weighted average grant date fair value - forfeited	$41.28
Weighted average grant date fair value - end of period	$42.49
Number of restricted stock and restricted stock units granted which will settle in cash	467,849
Restricted Stock And Restricted Stock Units RSU [Member]
Reconcilation of Beginning and Ending Balance of Nonvested Restricted Stock (including RSUs) [Abstract]
Number of restricted stock and restricted stock units granted which will settle in cash	486,508
Liability for cash-settled units	$13,000,000	$5,000,000

EARNINGS_PER_COMMON_SHARE_DETA

EARNINGS PER COMMON SHARE (DETAILS) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Basic earnings per common share
Net income	$160,952	$148,471
Less: Amounts attributable to (from) noncontrolling interests	-4,873	1,222
Less: preferred share dividends	10,022	10,022
Net income available to common shareholders	155,803	137,227
Weighted average common shares outstanding - basic	99,910	109,053
Basic earnings per common share	$1.56	$1.26
Diluted earnings per common share
Net income available to common shareholders	$155,803	$137,227
Weighted average common shares outstanding - basic	99,910	109,053
Stock compensation plans	1,229	1,338
Weighted average common shares outstanding - diluted	101,139	110,391
Diluted earnings per common share	$1.54	$1.24
Anti-dilutive shares excluded from the dilutive computation	569	1,051

SHAREHOLDERS_EQUITY_DETAILS

SHAREHOLDERS' EQUITY (DETAILS)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued, balance at beginning of period			175,478
Total shares issued at end of period	176,190		175,478
Treasury shares, balance at beginning of period			-76,052
Total treasury shares at end of period	-75,971		-76,052
Total shares outstanding	100,219		99,426
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued, balance at beginning of period	175,478	174,134
Shares issued	712	1,061
Total shares issued at end of period	176,190	175,195
Treasury shares, balance at beginning of period	-76,052	-64,649
Shares repurchased	-290	-4,036
Shares reissued from treasury	371	235
Total treasury shares at end of period	-75,971	-68,450
Total shares outstanding	100,219	106,745

SHAREHOLDERS_EQUITY_DETAILS_2

SHAREHOLDERS' EQUITY (DETAILS 2) (Common Stock [Member], USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Treasury Shares [Line Items]
Total shares	290	4,036
Total cost	$14,771	$178,703
Average price per share	$50.95	$44.27
In the Open Market [Member]
Treasury Shares [Line Items]
Total shares	16	3,710
Total cost	832	164,606
Average price per share	$50.69	$44.37
From Employees [Member]
Treasury Shares [Line Items]
Total shares	274	326
Total cost	$13,939	$14,097
Average price per share	$50.97	$43.14

NONCONTROLLING_INTERESTS_DETAI

NONCONTROLLING INTERESTS (DETAILS) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Noncontrolling Interest [Line Items]
Decrease from return of capital to noncontrolling interests	($40,000)	$0
Increase from issuance of preferred equity to noncontrolling interests	56,991	0
Assets	20,458,819		19,955,736
Liabilities	14,412,584		14,075,796
Change in Noncontrolling Interest [Roll Forward]
Balance at beginning of period	58,819	50,000
Increase from issuance of preferred equity to noncontrolling interests	56,991	0
Decrease from return of capital to noncontrolling interests	-40,000	0
Amounts attributable to (from) noncontrolling interests	-4,873	1,222
Foreign currency translation adjustment attributable to (from) noncontrolling interests	-1,865	0
Balance at end of period	69,072	51,222
Ventures Re [Member]
Noncontrolling Interest [Line Items]
Decrease from return of capital to noncontrolling interests	-40,000
Increase from issuance of preferred equity to noncontrolling interests	57,000
Assets	120,000		97,000
Liabilities	50,000		38,000
Change in Noncontrolling Interest [Roll Forward]
Increase from issuance of preferred equity to noncontrolling interests	57,000
Decrease from return of capital to noncontrolling interests	($40,000)

DEBT_AND_FINANCING_ARRANGEMENT1

DEBT AND FINANCING ARRANGEMENTS (Details) (Letter of Credit Facility [Member], USD $)	Mar. 31, 2015	Mar. 30, 2015
Letter of Credit Facility [Member]
Line of Credit Facility [Line Items]
Maximum capacity	$500,000,000	$750,000,000
Letters of credit outstanding	$354,000,000

COMMITMENTS_AND_CONTINGENCIES_

COMMITMENTS AND CONTINGENCIES (DETAILS) (USD $)	Mar. 31, 2015
In Millions, unless otherwise specified
Minimum reinsurance premiums [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Outstanding purchase commitment	$72
Outstanding purchase commitment, due in 2015	64
Outstanding purchase commitment, due in 2016	8
Commercial mortgage loans [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Outstanding purchase commitment	$50

COMMITMENTS_AND_CONTINGENCIES_1

COMMITMENTS AND CONTINGENCIES (DETAILS 2) (PartnerRe [Member], Subsequent Event [Member], USD $)	3-May-15	2-May-15
In Millions, except Per Share data, unless otherwise specified
Business Acquisition [Line Items]
Special Dividend	$11.50
Termination Fee	$280	$250
Scenario, Forecast [Member]
Business Acquisition [Line Items]
Special Dividend	$11.50
No Approval Fee	55
Termination Fee	280
Amalgamation Costs And Expenses Reimbursement	35
Financial advisor amalgamation fee	$20

OTHER_COMPREHENSIVE_INCOME_DET

OTHER COMPREHENSIVE INCOME (DETAILS) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Before Tax Amount
Unrealized gains (losses) arising during the period	$5,063	$80,560
Adjustment for reclassification of net realized investment gains (losses) and OTTI losses recognized in net income	45,098	-16,069
Unrealized gains arising during the period, net of reclassification adjustment	50,161	64,491
Non-credit portion of OTTI losses	0	0
Foreign currency translation adjustment	-13,278	2,659
Total other comprehensive income, net of tax	36,883	67,150
Tax (Expense) Benefit
Unrealized gains (losses) arising during the period	-10,250	-9,177
Adjustment for reclassification of net realized investment gains (losses) and OTTI losses recognized in net income	6	6,456
Unrealized gains arising during the period, net of reclassification adjustment	-10,244	-2,721
Non-credit portion of OTTI losses	0	0
Foreign currency translation adjustment	0	0
Total other comprehensive income, net of tax	-10,244	-2,721
Net of Tax Amount
Unrealized gains (losses) arising during the period	-5,187	71,383
Adjustment for reclassification of net realized investment gains and OTTI losses recognized in net income	45,104	-9,613
Unrealized gains arising during the period, net of reclassification adjustment	39,917	61,770
Non-credit portion of OTTI losses	0	0
Foreign currency translation adjustment	-13,278	2,659
Total other comprehensive income, net of tax	$26,639	$64,429

OTHER_COMPREHENSIVE_INCOME_DET1

OTHER COMPREHENSIVE INCOME (DETAILS 2) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Reclassification out of accumulated comprehensive income into net income available to common shareholders [Line Items]
Other realized investment gains (losses)	($24,985)	$11,406
OTTI losses	-17,568	-786
Income before income taxes	160,262	152,596
Income tax expense	690	-4,125
Net income attributable to AXIS Capital	165,825	147,249
Unrealized gains (losses) on available for sale investments [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of accumulated comprehensive income into net income available to common shareholders [Line Items]
Other realized investment gains (losses)	-27,530	16,855
OTTI losses	-17,568	-786
Income before income taxes	-45,098	16,069
Income tax expense	-6	-6,456
Net income attributable to AXIS Capital	($45,104)	$9,613

SUBSEQUENT_EVENTS_Details

SUBSEQUENT EVENTS (Details) (Subsequent Event [Member], USD $)	Apr. 01, 2015	3-May-15	2-May-15	Apr. 14, 2015
In Millions, except Per Share data, unless otherwise specified
Ternian [Member]
Subsequent Event [Line Items]
Acquired intangible assets	$13
PartnerRe [Member]
Subsequent Event [Line Items]
Business Acquisition, Share Price				$130
Special Dividend		$11.50
Termination Fee		$280	$250