XL (XLGLF) 10-Q 11 May 15 2015 Q1 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	3 Months Ended
	Mar. 31, 2015	6-May-15
Document and Entity Information [Abstract]
Entity Registrant Name	XL GROUP PLC
Entity Central Index Key	875159
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding		306,635,642

UNAUDITED_CONSOLIDATED_BALANCE

UNAUDITED CONSOLIDATED BALANCE SHEETS (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Investments:
Fixed maturities, at fair value (amortized cost: 2015, $27,370,101; 2014, $27,728,771)	$29,110,400	$29,359,034
Equity securities, at fair value (cost: 2015, $665,682; 2014, $763,833)	783,471	868,292
Short-term investments, at fair value (amortized cost: 2015, $169,903; 2014, $257,221)	168,862	256,727
Total investments available for sale	30,062,733	30,484,053
Fixed maturities, trading at fair value (amortized cost: 2015, $138,647; 2014, $1,180)	139,377	1,171
Investments in affiliates	1,655,394	1,637,620
Other investments	1,328,935	1,248,439
Total investments	33,186,439	33,371,283
Cash and cash equivalents	3,209,934	2,521,814
Accrued investment income	278,714	315,964
Deferred acquisition costs	417,275	354,533
Ceded unearned premiums	1,078,575	952,525
Premiums receivable	2,898,739	2,473,736
Reinsurance balances receivable	118,384	131,519
Unpaid losses and loss expenses recoverable	3,529,331	3,429,368
Receivable from investments sold	19,627	92,762
Goodwill and other intangible assets	442,431	447,952
Deferred tax asset	192,286	204,491
Other assets	708,821	750,872
Total assets	46,080,556	45,046,819
Liabilities:
Unpaid losses and loss expenses	18,965,264	19,353,243
Deposit liabilities	1,211,203	1,245,367
Future policy benefit reserves	4,375,863	4,707,199
Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable: 2015, $3,933,589; 2014, 4,265,678)	1,138,652	1,155,016
Unearned premiums	4,532,022	3,973,132
Notes payable and debt	2,643,561	1,662,580
Reinsurance balances payable	558,952	493,230
Payable for investments purchased	75,145	42,291
Deferred tax liability	66,115	66,246
Other liabilities	867,356	912,749
Total liabilities	34,434,133	33,611,053
Commitments and Contingencies
Shareholders' Equity:
Ordinary shares, 999,990,000 authorized, par value $0.01; issued and outstanding (2015, 256,683,621; 2014, 255,182,955)	2,567	2,552
Additional paid in capital	7,361,138	7,359,102
Accumulated other comprehensive income	1,705,170	1,484,458
Retained earnings	1,175,182	1,187,639
Shareholders' equity attributable to XL Group plc	10,244,057	10,033,751
Non-controlling interest in equity of consolidated subsidiaries	1,402,366	1,402,015
Total shareholders' equity	11,646,423	11,435,766
Total liabilities and shareholders' equity	$46,080,556	$45,046,819

UNAUDITED_CONSOLIDATED_BALANCE1

UNAUDITED CONSOLIDATED BALANCE SHEETS (Parentheticals) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, except Share data, unless otherwise specified
Amortized cost of fixed maturities, available for sale	$27,370,101	$27,728,771
Cost of equity securities, available for sale	665,682	763,833
Amortized cost of short-term investments, available for sale	169,903	257,221
Amortized cost of fixed maturities, trading	138,647	1,180
Future policy benefit reserves recoverable	$3,933,589	$4,265,678
Ordinary shares, shares authorized (in shares)	999,990,000	999,990,000
Ordinary shares, par value (in dollars per share)	$0.01	$0.01
Ordinary shares, shares issued (in shares)	256,683,621	255,182,955
Ordinary shares, shares outstanding (in shares)	256,683,621	255,182,955

UNAUDITED_CONSOLIDATED_STATEME

UNAUDITED CONSOLIDATED STATEMENTS OF INCOME (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenues:
Net premiums earned	$1,334,000	$1,488,839
Net investment income	208,513	233,189
Realized investment gains (losses):
Total net realized gains (losses) on investments, and net unrealized gains (losses) on investments Trading - Life Funds Withheld Assets	52,891	19,229
Net realized and unrealized gains (losses) on derivative instruments	16,521	1,810
Income (loss) from investment fund affiliates	35,329	33,303
Fee income and other	4,728	11,454
Total revenues	1,422,615	1,787,824
Expenses:
Net losses and loss expenses incurred	769,827	831,505
Claims and policy benefits	19,387	113,587
Acquisition costs	153,696	199,414
Operating expenses	325,656	310,424
Foreign exchange (gains) losses	27,390	10,441
Interest expense	51,438	42,941
Total expenses	1,347,394	1,508,312
Income (loss) before income tax and income (loss) from operating affiliates	75,221	279,512
Income (loss) from operating affiliates	22,668	46,285
Provision (benefit) for income tax	24,218	34,321
Net income (loss)	73,671	291,476
Non-controlling interests	37,390	35,759
Net income (loss) attributable to ordinary shareholders	36,281	255,717
Weighted average ordinary shares outstanding - basic	255,724	276,337
Weighted average ordinary shares outstanding - diluted	260,704	280,458
Earnings (loss) per ordinary share and ordinary share equivalent - basic (in dollars per share)	$0.14	$0.93
Earnings (loss) per ordinary share and ordinary share equivalent - diluted (in dollars per share)	$0.14	$0.91
Excluding Life Funds Withheld Assets
Revenues:
Net investment income	158,094	233,189
Realized investment gains (losses):
Net realized gains (losses) on investments sold	15,178	22,956
Other-than-temporary impairments on investments	-10,515	-2,276
Other-than-temporary impairments on investments transferred to (from) other comprehensive income	-61	-1,451
Life Funds Withheld Assets
Revenues:
Net investment income	50,419	0
Realized investment gains (losses):
Net realized gains (losses) on investments sold	52,738	0
Other-than-temporary impairments on investments	-5,209	0
Net unrealized gains (losses) on investments, trading securities	760	0
Net realized and unrealized gains (losses) on derivative instruments	($229,367)	$0

UNAUDITED_CONSOLIDATED_STATEME1

UNAUDITED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Net income (loss) attributable to ordinary shareholders	$36,281	$255,717
Change in adjustments related to future policy benefit reserves, net of tax	60,356	-34,004
Change in net unrealized gains (losses) on affiliate and other investments, net of tax	15,865	3,123
Change in OTTI losses recognized in other comprehensive income, net of tax	9,858	3,296
Change in underfunded pension liability, net of tax	975	-31
Change in value of cash flow hedge	95	110
Foreign currency translation adjustments, net of tax	36,103	-3,880
Comprehensive income (loss)	256,993	465,721
Excluding Life Funds Withheld Assets
Change in net unrealized gains (losses) on investments, net of tax	60,345	241,390
Life Funds Withheld Assets
Change in net unrealized gains (losses) on investments, net of tax	$37,115	$0

UNAUDITED_CONSOLIDATED_STATEME2

UNAUDITED CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $)	Total	Excluding Life Funds Withheld Assets	Life Funds Withheld Assets	Ordinary Shares	Additional Paid in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Deficit)	Non-controlling Interest in Equity of Consolidated Subsidiaries
In Thousands							Excluding Life Funds Withheld Assets	Life Funds Withheld Assets
Balance, beginning of year at Dec. 31, 2013				$2,783	$7,994,100	$736,657			$1,264,093	$1,351,665
Issuance of ordinary shares				10	7
Buybacks of ordinary shares				-58	-168,144				-8,293
Exercise of stock options				1
Exercise of stock options					1,309
Share-based compensation expense					1,396				0
Change in net unrealized gains (losses) on investments, net of tax		241,390	0				241,390	0
Change in adjustments related to future policy benefit reserves, net of tax	-34,004					-34,004
Change in net unrealized gains (losses) on affiliate and other investments, net of tax	3,123					3,123
Change in OTTI losses recognized in other comprehensive income, net of tax	3,296					3,296
Change in underfunded pension liability, net of tax	-31					-31
Change in value of cash flow hedge	110					110
Foreign currency translation adjustments, net of tax	-3,880					-3,880
Net income (loss) attributable to ordinary shareholders	255,717								255,717
Dividends on ordinary shares									-44,620
Non-controlling interests - contributions										7,001
Non-controlling interests - distributions										0
Non-controlling interests										346
Balance, end of year at Mar. 31, 2014	11,603,974			2,736	7,828,668	946,661			1,466,897	1,359,012
Balance, beginning of year at Dec. 31, 2014	11,435,766			2,552	7,359,102	1,484,458			1,187,639	1,402,015
Issuance of ordinary shares				15	6
Buybacks of ordinary shares				-1	-1,573				-393
Exercise of stock options				1
Exercise of stock options					1,771
Share-based compensation expense					1,832				-6,746
Change in net unrealized gains (losses) on investments, net of tax		60,345	37,115				60,345	37,115
Change in adjustments related to future policy benefit reserves, net of tax	60,356					60,356
Change in net unrealized gains (losses) on affiliate and other investments, net of tax	15,865					15,865
Change in OTTI losses recognized in other comprehensive income, net of tax	9,858					9,858
Change in underfunded pension liability, net of tax	975					975
Change in value of cash flow hedge	95					95
Foreign currency translation adjustments, net of tax	36,103					36,103
Net income (loss) attributable to ordinary shareholders	36,281								36,281
Dividends on ordinary shares									-41,599
Non-controlling interests - contributions										2,569
Non-controlling interests - distributions										-4,175
Non-controlling interests										1,957
Balance, end of year at Mar. 31, 2015	$11,646,423			$2,567	$7,361,138	$1,705,170			$1,175,182	$1,402,366

UNAUDITED_CONSOLIDATED_STATEME3

UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash flows provided by (used in) operating activities:
Net income (loss)	$73,671	$291,476
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Total net realized (gains) losses on investments and net unrealized (gains) losses on investments, Trading - Life Funds Withheld Assets	-52,891	-19,229
Net realized and unrealized (gains) losses on derivative instruments	-16,521	-1,810
Amortization of premiums (discounts) on fixed maturities	35,998	39,488
(Income) loss from investment and operating affiliates	-45,467	-31,999
Share-based compensation	18,295	15,974
Depreciation	10,907	14,961
Accretion of deposit liabilities	10,044	10,477
Changes in:
Unpaid losses and loss expenses	77,832	-72,058
Future policy benefit reserves	-49,279	-49,780
Funds withheld on life retrocession agreements, net	-169,569	0
Unearned premiums	655,733	621,009
Premiums receivable	-517,881	-594,243
Unpaid losses and loss expenses recoverable	-148,962	28,747
Ceded unearned premiums	-146,049	-110,310
Reinsurance balances receivable	10,057	-60,224
Deferred acquisition costs	-72,340	-56,937
Reinsurance balances payable	84,261	269,717
Deferred tax asset - net	14,119	-598
Derivatives	141,754	-12,277
Other assets	-31,407	-25,731
Other liabilities	-94,545	-77,037
Other	17,851	20,452
Total adjustments	-38,693	-91,408
Net cash provided by (used in) operating activities	34,978	200,068
Cash flows provided by (used in) investing activities:
Proceeds from sale of fixed maturities and short-term investments	1,473,941	1,106,926
Proceeds from redemption of fixed maturities and short-term investments	1,053,739	1,056,358
Proceeds from sale of equity securities	189,473	76,382
Purchases of fixed maturities and short term investments	-2,835,304	-1,411,447
Purchases of equity securities	-94,141	-80,833
Proceeds from sale of affiliates	77,916	145,174
Purchases of affiliates	-29,037	-86,205
Other, net	-32,141	-106,075
Net cash provided by (used in) investing activities	-195,554	700,280
Cash flows provided by (used in) financing activities:
Proceeds from issuance of ordinary shares and exercise of stock options	1,772	1,310
Buybacks of ordinary shares	-1,966	-176,496
Dividends paid on ordinary shares	-40,922	-43,847
Distributions to non-controlling interests	-7,172	-3,008
Contributions from non-controlling interests	2,569	7,001
Proceeds from the issuance of debt	980,600	0
Deposit liabilities	-38,788	-17,270
Net cash provided by (used in) financing activities	896,093	-232,310
Effects of exchange rate changes on foreign currency cash	-47,397	7,177
Increase (decrease) in cash and cash equivalents	688,120	675,215
Cash and cash equivalents beginning of year	2,521,814	1,800,832
Cash and cash equivalents end of year	3,209,934	2,476,047
Life Funds Withheld Assets
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Net realized and unrealized (gains) losses on derivative instruments	$229,367	$0

Basis_of_Preparation_and_Conso

Basis of Preparation and Consolidation	3 Months Ended
	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Preparation and Consolidation	Basis of Preparation and Consolidation
	Unless the context otherwise indicates, references herein to the “Company” include XL Group plc, an Irish public limited company ("XL-Ireland"), and its consolidated subsidiaries.
	These unaudited consolidated financial statements include the accounts of the Company and all of its subsidiaries and have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by GAAP for complete financial statements. In addition, the year-end balance sheet data was derived from audited financial statements but do not include all disclosures required by GAAP. In the opinion of management, these unaudited financial statements reflect all adjustments considered necessary for a fair statement of financial position and results of operations at the end of and 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 preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure about contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ materially from these estimates. For further information, see Item 8, Note 2(a), “Significant Accounting Policies – Basis of Preparation and Consolidation,” to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014.
	To facilitate period-to-period comparisons, certain reclassifications have been made to prior period consolidated financial statement amounts to conform to current period presentation.

Significant_Accounting_Policie

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies
	(a) Recent Accounting Pronouncements
	In February 2015, the Financial Accounting Standards Board ("FASB") issued an accounting standards update concerning consolidation of certain legal entities. Under this new guidance, all legal entities are required to evaluate whether they should consolidate certain legal entities. The guidance: (1) modifies the evaluation of whether limited partnerships and similar legal entities are variable interest entities ("VIEs") or voting interest entities; (2) eliminates the presumption that a general partner should consolidate a limited partnership; (3) affects the consolidation analysis of reporting entities that are involved with VIEs, particularly those that have fee arrangements and related party relationships; and (4) provides a scope exception from consolidation guidance for certain reporting entities. Upon adoption of the new guidance, differing requirements for performing a consolidation analysis under existing GAAP will be eliminated, and all reporting entities will now fall within the scope of the Accounting Standards Codification Subtopic 810-10, Consolidation-Overall, unless a specific exception applies. Under this Subtopic, there are only two primary models for determining whether consolidation is appropriate - a voting interest entity model, and a variable interest entity model. The guidance is effective for public business entities for annual periods ending after December 15, 2015, and interim and annual periods thereafter, with early adoption permitted. The Company is currently evaluating the impact of this guidance.
	In April 2015, the FASB issued an accounting standards update concerning the presentation of deferred debt issuance costs in an entity's balance sheet. Under this new guidance, which is part of the FASB's initiative to reduce complexity in accounting standards while maintaining or improving the usefulness of the information provided to users of financial statements, it is required that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. In addition, the guidance also requires that the amortization of such costs be reported as interest expense. The guidance is effective for public business entities for annual periods beginning after December 31, 2015, and interim periods within those fiscal years, with early adoption permitted for financial statements that have not been previously issued. This guidance is not expected to have a material impact on the Company's financial condition, results of operations or cash flows.

Acquisition_and_Disposals

Acquisition and Disposals	3 Months Ended
	Mar. 31, 2015
Acquisition and Disposal [Abstract]
Acquisition and Disposals	Acquisition and Disposals
	(a)    Catlin Acquisition
	On May 1, 2015 (the "Acquisition Date"), the Company completed its acquisition (the "Acquisition") of the entire issued share capital of Catlin Group Limited ("Catlin") as contemplated by that certain Implementation Agreement, dated January 9, 2015 (the “Implementation Agreement”), by and among XL-Ireland, Green Holdings Limited, a direct, wholly-owned subsidiary of the Company (“Green Holdings”), and Catlin.
	Pursuant to the terms of the Implementation Agreement, the Acquisition was implemented by way of a scheme of arrangement (the “Scheme”) under Section 99 of the Companies Act 1981 of Bermuda, as amended (the “Companies Act”), and sanctioned by the Supreme Court of Bermuda (the “Court”), immediately after which Catlin was merged with and into Green Holdings under Section 104H of the Companies Act, with Green Holdings as the surviving company, pursuant to the terms of that certain Merger Agreement, dated January 9, 2015 (the “Merger Agreement”), among XL-Ireland, Green Holdings and Catlin. The XL Shares issued in connection with the Acquisition were issued in reliance upon an exemption from registration under U.S. federal securities laws provided by Section 3(a)(10) of the Securities Act of 1933, as amended (the “Securities Act”).
	Pursuant to the terms of the Implementation Agreement, XL-Ireland acquired each ordinary share of Catlin, par value $0.01 per share (“Catlin Shares”), for consideration per Catlin Share (the “Acquisition Consideration”) equal to 388 pence in cash and 0.130 of an XL-Ireland ordinary share, par value $0.01 per share (“XL Shares”), subject to the mix and match facility set forth in the Implementation Agreement. The newly-issued XL Shares are listed on the New York Stock Exchange.
	XL-Ireland issued approximately 49.9 million XL Shares and paid approximately £1.49 billion in cash to the holders of Catlin Shares as Acquisition Consideration pursuant to the terms of the Scheme.
	The foregoing description of the Implementation Agreement and the Merger Agreement is qualified in its entirety by reference to the full text of the Implementation Agreement and Merger Agreement, copies of which were filed on Form 8-K on January 9, 2015.
	In connection with the Acquisition, on January 9, 2015, the Company announced that it was able to rely on £1.6 billion of debt to be provided under a bridge facility entered into by XLIT Ltd., a wholly-owned subsidiary of the Company ("XL-Cayman"), and arranged by Morgan Stanley Senior Funding, Inc. and Goldman Sachs Bank USA (the "Bridge Facility") for the purposes of discharging the cash component of the Acquisition consideration.
	In addition, on January 9, 2015, the Company entered into deal contingent deliverable foreign exchange forwards ("FX Forwards") with Morgan Stanley Capital Services LLC and Goldman Sachs International. The purpose of the FX Forwards was to mitigate risk of foreign currency exposure related to the Acquisition. Following the close of the Acquisition, the FX Forwards were settled.
	The calculation of the consideration transferred to acquire Catlin Shares is as follows:
	(In thousands, except per share data)
	Catlin Shares outstanding as of April 30, 2015 that will receive share consideration (including the dilutive effect of warrants)	384,118
	Exchange ratio per the merger agreement	0.13
	Share issuance to Catlin shareholders	49,935
	Closing price per share on April 30, 2015 (1)	$	37.08
	Share issuance consideration	$	1,851,601
	Shares of Catlin common stock outstanding as of April 30, 2015 that will receive cash consideration (including the dilutive effect of warrants)	384,118
	Cash price component, per share in GBP	£	3.88
	Cash consideration, in GBP	£	1,490,377
	Foreign exchange rate: GBP/USD on April 30, 2015	$	1.5349
	Cash consideration	$	2,287,579
	Total acquisition consideration	$	4,139,180
	____________
	-1	The closing market price of XL's common stock on the acquisition date represents the fair value of shares issued as part of the consideration transferred.
	The Company financed the $2.29 billion cash consideration portion of the Acquisition by issuing $1.0 billion of subordinated debt, net proceeds of which were $980.6 million, and the remaining $1.31 billion by using cash and cash equivalents on hand. See Note 10, "Notes Payable and Debt and Financing Arrangements," for further information on the debt issuance. The Company terminated the commitments under the Bridge Facility as of April 8, 2015, due to a sufficient amount in escrow to discharge the cash consideration payable to Catlin shareholders in respect of the Acquisition.
	Due to the limited time subsequent to the Acquisition Date, the accounting for the Acquisition is not yet complete. The Company will file an amendment to its current report on Form 8-K filed on May 4, 2015 to provide pro forma financial statements and intends to include amounts recognized as of the Acquisition Date for the major classes of assets and liabilities assumed, pre-acquisition contingencies and goodwill in the Company's Quarterly Report on Form 10-Q for the second quarter of 2015.
	The Company incurred certain acquisition, integration and financing costs associated with the transaction prior to the Acquisition Date. The Company has recorded $25.5 million of these costs for the three months ended March 31, 2015, of which $10.5 million has been included in Operating expenses and $15.0 million has been included in Interest expense. However, the assets acquired and the liabilities assumed from Catlin, the consideration paid to acquire Catlin, as well as the results of Catlin's operations are not reflected in the Unaudited Consolidated Financial Statements as of and for the three months ended March 31, 2015.
	(b)    Sale of Strategic Operating Affiliate
	On April 1, 2015, XL Re Ltd ("XL Re"), an indirect wholly-owned subsidiary of the Company, completed the previously announced sale of all of its shares in ARX Holding Corp. ("ARX") to The Progressive Corporation ("Progressive") pursuant to the terms of the Stock Purchase Agreement with Progressive. XL Re's shares in ARX represented approximately 40.6% of ARX's outstanding capital stock on a fully diluted basis at the time of the announcement. As of March 31, 2015, the Company recorded XL Re's shares in ARX as $222.6 million, included within Investments in Affiliates.
	XL Re received approximately $560 million in proceeds from the transaction, which was based upon the consolidated tangible net book value of ARX and its subsidiaries as of December 31, 2014, and certain other factors. The Company will record a gain of approximately $337 million in the second quarter as a result of this transaction.
	(c)    Sale of Life Reinsurance Subsidiary
	On May 1, 2014, a wholly owned subsidiary of the Company, XL Insurance (Bermuda) Ltd (“XLIB”), entered into a sale and purchase agreement with GreyCastle Holdings Ltd. (“GreyCastle”) providing for the sale of 100% of the common shares of XLIB's wholly-owned subsidiary, XL Life Reinsurance (SAC) Ltd (“XLLR”), to GreyCastle for $570 million in cash (subsequent to the transaction, XLLR changed its name to GreyCastle Life Reinsurance (SAC) Ltd ("GCLR")). This transaction closed on May 30, 2014. As a result of the transaction, the Company ceded the majority of its life reinsurance business to GCLR via 100% quota share reinsurance (the "Life Retro Arrangements"). This transaction covered a substantial portion of our life reinsurance reserves. The Company ceased writing new life reinsurance contracts in 2009 and since that time has been managing the run-off of its life reinsurance operations ("Run-Off Life Operations"). The designated investments that support the Life Retro Arrangements on a funds withheld basis ("Life Funds Withheld Assets") are managed pursuant to agreed investment guidelines that meet the contractual commitments of the Company's ceding subsidiaries and applicable laws and regulations. All of the investment results associated with the Life Funds Withheld Assets ultimately accrue to GCLR.
	The Run-Off Life Operations business, including the business subject to the transaction with GreyCastle, was previously reported within the Company’s Life operations segment. Subsequent to the transaction, the Company no longer considers the Life operations to be a separate operating segment and the results of the Run-Off Life Operations are reported within “Corporate and Other.” See Note 5, "Segment Information," for further information. In addition, certain securities within fixed maturities were reclassified from held to maturity to available for sale in conjunction with this transaction. See Note 6, "Investments," for further information.
	All of the reclassified securities are included within Life Funds Withheld Assets, along with certain other available for sale securities as defined in the sale and purchase agreement. The Life Funds Withheld Assets are managed pursuant to agreed investment guidelines that meet the contractual commitments of the XL ceding companies and applicable laws and regulations. All of the investment results associated with the Life Funds Withheld Assets ultimately accrue to GCLR. Because the Company no longer shares in the risks and rewards of the underlying performance of the supporting invested assets, disclosures within the financial statement notes included herein separate the Life Funds Withheld Assets from the rest of the Company's investments.
	As of May 30, 2014, gross future policy benefit reserves relating to the Life operations were approximately $5.2 billion. Subsequent to the completion of the GreyCastle transaction, the Company retained approximately $0.4 billion of these reserves, and recorded a reinsurance recoverable from GCLR of $4.8 billion. Under the terms of the transaction, the Company continues to own, on a funds withheld basis, assets supporting the Life Retro Arrangements consisting of cash, fixed maturity securities and accrued interest. Based upon the right of offset, the funds withheld liability owing to GCLR is recorded net of future policy benefit reserves recoverable, and is included within “Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable)" on the unaudited consolidated balance sheets. The transaction resulted in an overall after-tax U.S. GAAP net loss of $621.3 million.
	As of March 31, 2015, gross future policy benefit reserves relating to the Run-Off Life Operations were approximately $4.4 billion, of which the Company retained approximately $0.4 billion, after consideration of its future policy benefit reserves recoverable from GCLR of approximately $3.9 billion. The net funds withheld liability included within “Funds withheld on life retrocession arrangements, net of future policy benefit reserves recoverable" was $1.1 billion. The Company continued to own $5.1 billion of assets supporting the Life Retro Arrangements.
	The impact of the Life Retro Arrangements on the Company's results was as follows:
	Impact of Life Retro Arrangements	Three months ended March 31,
	(U.S. dollars in thousands)	2015
	Underwriting profit (loss) (1)	$	603
	Net investment income - Life Funds Withheld Assets	50,419
	Net realized gains (losses) on investments sold - Life Funds Withheld Assets	52,738
	Net unrealized gains (losses) on investments, Trading - Life Funds Withheld Assets	760
	OTTI on investments - Life Funds Withheld Assets	(5,209		)
	Exchange (gains) losses	3,684
	Other income and expenses	(1,298		)
	Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets	(229,367		)
	Net income (loss)	$	(127,670	)
	Change in net unrealized gains (losses) on investments - Life Funds Withheld Assets, net of tax	37,115
	Change in adjustments related to future policy benefit reserves, net of tax	60,356
	Change in cumulative translation adjustment - Life Funds Withheld Assets, net of tax	30,802
	Total changes to other comprehensive income as a result of Life Retro Arrangements	$	128,273
	Comprehensive income (loss)	$	603
	____________
	-1	The underwriting profit of $0.6 million relates to a premium adjustment during the three months ended March 31, 2015 relating to the Life Retro Arrangements transaction which was completed on May 30, 2014. Excluding this transaction, the impact to comprehensive income relating to the Life Retro Arrangements was nil for the three months ended March 31, 2015.
	As shown in the table above, although the Company's net income (loss) is subject to variability related to the Life Retro Arrangements, there is minimal net impact on the Company's comprehensive income in any period. The life retrocession embedded derivative value includes the interest income, unrealized gains and losses, and realized gains and losses from sales on the Life Funds Withheld Assets subsequent to May 30, 2014.

Fair_Value_Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements
	Fair value is defined as the amount that would be received for the sale of an asset or paid to transfer a liability (an exit price), in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants as of the measurement date. Applicable accounting guidance provides an established hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs that market participants would use in valuing the asset or liability and are developed based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the factors that market participants would use in valuing the asset or liability. Assets and liabilities are classified based on the lowest level of input that is significant to the fair value measurements. The Company reviews the fair value hierarchy classification on a quarterly basis. Changes in the observability of valuation inputs may result in a reclassification of levels for certain securities within the fair value hierarchy.
	The fair values for available for sale investments are generally sourced from third parties. The fair value of fixed income securities is based upon quoted market values where available, “evaluated bid” prices provided by third party pricing services (“pricing services”) where quoted market values are not available, or by reference to broker quotes where pricing services do not provide coverage for a particular security. While the Company receives values for the majority of the investment securities it holds from pricing services, it is ultimately management’s responsibility to determine whether the values received and recorded in the financial statements are representative of appropriate fair value measurements.
	The Company performs regular reviews of the prices received from its third party valuation sources to assess if the prices represent a reasonable estimate of the fair value. This process is completed by investment and accounting personnel who are independent of those responsible for obtaining the valuations. The approaches taken by the Company include, but are not limited to, annual reviews of the controls of the external parties responsible for sourcing valuations, which are subjected to automated tolerance checks, quarterly reviews of the valuation sources and dates, and monthly reconciliations between the valuations provided by our external parties and valuations provided by our third party investment managers at a portfolio level.
	Where broker quotes are the primary source of the valuations, sufficient information regarding the specific inputs utilized by the brokers is generally not available to support a Level 2 classification. The Company obtains the majority of broker quoted values from third party investment managers who perform independent verifications of these valuations using pricing matrices based upon information gathered by market traders. In addition, for the majority of these securities, the Company compares the broker quotes to independent valuations obtained from third party pricing vendors, which may also consist of broker quotes, to assess if the prices received represent a reasonable estimate of the fair value.
	As discussed in Note 3(c), “Acquisition and Disposals - Sale of Life Reinsurance Subsidiary,” under the Life Retro Arrangements, all of the investment results associated with the Life Funds Withheld Assets ultimately accrue to GCLR. Because the Company no longer shares in the risks and rewards of the underlying performance of the Life Funds Withheld Assets, the financial statements and accompanying notes included herein separately report the Life Funds Withheld Assets from the rest of the Company's investments.
	For further information about the Company's fair value measurements, see Item 8, Note 2(b), “Significant Accounting Policies - Fair Value Measurements,” to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014.
	(a) Fair Value Summary
	The following tables set forth the Company’s assets and liabilities that were accounted for at fair value as of March 31, 2015 and December 31, 2014 by level within the fair value hierarchy:
	31-Mar-15	Quoted Prices			Significant			Significant			Collateral			Balance at
	(U.S. dollars in thousands)	in Active			Other			Other			and			31-Mar-15
		Markets for			Observable			Unobservable			Counterparty
		Identical Assets			Inputs			Inputs			Netting
		(Level 1)			(Level 2)			(Level 3)
	Assets
	Fixed maturities - Available for Sale ("AFS") - Excluding Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	—		$	3,378,342		$	—		$	—		$	3,378,342
	Corporate (1)	—			8,148,777			5,861			—			8,154,638
	Residential mortgage-backed securities – Agency (“RMBS - Agency”)	—			3,709,514			1,820			—			3,711,334
	Residential mortgage-backed securities – Non-Agency (“RMBS - Non-Agency”)	—			380,135			—			—			380,135
	Commercial mortgage-backed securities (“CMBS”)	—			1,032,720			—			—			1,032,720
	Collateralized debt obligations (“CDO”)	—			4,051			496,923			—			500,974
	Other asset-backed securities	—			1,165,123			2,244			—			1,167,367
	U.S. States and political subdivisions of the States	—			1,973,140			—			—			1,973,140
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	—			4,093,771			—			—			4,093,771
	Total fixed maturities - AFS - Excluding Funds Withheld Assets, at fair value	$	—		$	23,885,573		$	506,848		$	—		$	24,392,421
	Equity securities, at fair value	497,496			285,975			—			—			783,471
	Short-term investments, at fair value (1)(2)	—			168,862			—			—			168,862
	Total investments AFS - Excluding Funds Withheld Assets	$	497,496		$	24,340,410		$	506,848		$	—		$	25,344,754
	Fixed maturities - Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	—		$	17,613		$	—		$	—		$	17,613
	Corporate	—			2,746,226			—			—			2,746,226
	RMBS – Agency	—			2,130			—			—			2,130
	RMBS – Non-Agency	—			38,808			—			—			38,808
	CMBS	—			159,257			—			—			159,257
	Other asset-backed securities	—			244,140			—			—			244,140
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	—			1,509,805			—			—			1,509,805
	Total fixed maturities - AFS - Life Funds Withheld Assets, at fair value	$	—		$	4,717,979		$	—		$	—		$	4,717,979
	Total investments - AFS, at fair value	$	497,496		$	29,058,389		$	506,848		$	—		$	30,062,733
	Fixed maturities - trading securities ("Trading")
	Corporate	—			137,438			—			—			137,438
	Other asset-backed securities	—			1,939			—			—			1,939
	Total fixed maturities - Trading, at fair value	$	—		$	139,377		$	—		$	—		$	139,377
	Cash equivalents (3)	1,835,344			393,154			—			—			2,228,498
	Cash equivalents - Life Funds Withheld Assets (3)	788			120,721			—			—			121,509
	Other investments (4)	—			784,486			190,097			—			974,583
	Other assets (5)	—			244,900			12,980			(587		)	257,293
	Total assets accounted for at fair value	$	2,333,628		$	30,741,027		$	709,925		$	(587	)	$	33,783,993
	Liabilities
	Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable) (6)	$	—		$	654,561		$	—		$	—		$	654,561
	Financial instruments sold, but not yet purchased (7)	1,572			5,660			—			—			7,232
	Other liabilities (5)	—			99,649			22,586			(587		)	121,648
	Total liabilities accounted for at fair value	$	1,572		$	759,870		$	22,586		$	(587	)	$	783,441
	31-Dec-14	Quoted Prices			Significant			Significant			Collateral			Balance at
	(U.S. dollars in thousands)	in Active			Other			Other			and			December 31,
		Markets for			Observable			Unobservable			Counterparty			2014
		Identical Assets			Inputs			Inputs			Netting
		(Level 1)			(Level 2)			(Level 3)
	Assets
	Fixed maturities - AFS - Excluding Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	—		$	2,171,953		$	—		$	—		$	2,171,953
	Corporate (1)	—			8,772,479			5,894			—			$	8,778,373
	Residential mortgage-backed securities – RMBS - Agency	—			3,726,666			1,910			—			$	3,728,576
	Residential mortgage-backed securities – RMBS - Non-Agency	—			427,351			—			—			$	427,351
CMBS	—			1,052,544			—			—			$	1,052,544
CDO	—			4,076			687,958			—			$	692,034
Other asset-backed securities	—			1,060,005			5,288			—			$	1,065,293
U.S. States and political subdivisions of the States	—			2,021,272			—			—			$	2,021,272
Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	—			4,240,073			—			—			$	4,240,073
Total fixed maturities - AFS - Excluding Funds Withheld Assets, at fair value	$	—		$	23,476,419		$	701,050		$	—		$	24,177,469
Equity securities, at fair value	502,284			366,008			—			—			868,292
Short-term investments, at fair value (1)(2)	—			256,727			—			—			256,727
Total investments AFS - Excluding Funds Withheld Assets	$	502,284		$	24,099,154		$	701,050		$	—		$	25,302,488
Fixed maturities - Life Funds Withheld Assets
U.S. Government and Government-Related/Supported	$	—		$	18,724		$	—		$	—		$	18,724
Corporate	—			2,817,980			—			—			$	2,817,980
RMBS – Agency	—			3,782			—			—			$	3,782
RMBS – Non-Agency	—			85,335			—			—			$	85,335
CMBS	—			193,167			—			—			$	193,167
Other asset-backed securities	—			273,541			—			—			$	273,541
Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	—			1,789,036			—			—			$	1,789,036
Total fixed maturities - AFS - Life Funds Withheld Assets, at fair value	$	—		$	5,181,565		$	—		$	—		$	5,181,565
Total investments - AFS, at fair value	$	502,284		$	29,280,719		$	701,050		$	—		$	30,484,053
Fixed maturities - Trading
Corporate	—			1,171			—			—			$	1,171
Total fixed maturities - Trading, at fair value	$	—		$	1,171		$	—		$	—		$	1,171
Cash equivalents (3)	1,103,877			397,955			—			—			$	1,501,832
Cash equivalents - Life Funds Withheld Assets (3)	460			132,738			—			—			$	133,198
Other investments (4)	—			708,974			185,083			—			$	894,057
Other assets (5)	—			122,996			13,663			(696		)	$	135,963
Total assets accounted for at fair value	$	1,606,621		$	30,644,553		$	899,796		$	(696	)	$	33,150,274
Liabilities
Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable) (6)	$	—		$	450,831		$	—		$	—		$	450,831
Financial instruments sold, but not yet purchased (7)	4,737			25,669			—			—			$	30,406
Other liabilities (5)	—			7,757			23,427			(696		)	$	30,488
Total liabilities accounted for at fair value	$	4,737		$	484,257		$	23,427		$	(696	)	$	511,725
____________
-1	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes had a fair value of $74.8 million and $79.9 million and an amortized cost of $63.8 million and $68.4 million as of March 31, 2015 and December 31, 2014, respectively. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.
-2	Short-term investments consist primarily of Corporate securities and U.S. and Non-U.S. Government and Government-Related/Supported securities.
-3	Cash equivalents balances subject to fair value measurement include certificates of deposit and money market funds. Operating cash balances are not subject to recurring fair value measurement guidance.
-4	The Other investments balance excludes certain structured transactions including certain investments in project finance transactions, a payment obligation and liquidity financing provided to a structured credit vehicle as a part of a third party medium term note facility. These investments, which totaled $354.4 million as of March 31, 2015 and $354.4 million at December 31, 2014, are carried at amortized cost. For further information, see Item 8, Note 8, “Other Investments,” to the Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2014.
-5	Other assets and other liabilities include derivative instruments. The derivative balances included in each category are reported on a gross basis by level with a netting adjustment presented separately in the Collateral and Counterparty Netting column. The fair values of the individual derivative contracts are reported gross in their respective levels based on the fair value hierarchy. For further details regarding derivative fair values and associated collateral received or paid see Note 7, “Derivative Instruments,” to the Unaudited Consolidated Financial Statements.
-6	Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable) include balances related to the life retrocession embedded derivative, under which all investment results associated with the Life Funds Withheld Assets related to the Life Retro Arrangements described in Note 3(c), ”Acquisition and Disposals - Sale of Life Reinsurance Subsidiary," accrue to the benefit of GCLR.
-7	Financial instruments sold, but not yet purchased, represent “short sales” and are included within “Payable for investments purchased” on the balance sheets.
(b) Level 3 Assets and Liabilities
The tables below present additional information about assets and liabilities measured at fair value on a recurring basis and for which Level 3 inputs were utilized to determine fair value. The tables present a reconciliation of the beginning and ending balances for the three months ended March 31, 2015 and 2014 for all financial assets and liabilities measured at fair value using significant unobservable inputs (Level 3) at March 31, 2015 and 2014, respectively. The tables do not include gains or losses that were reported in Level 3 in prior periods for assets that were transferred out of Level 3 prior to March 31, 2015 and 2014, respectively. Gains and losses for assets and liabilities classified within Level 3 in the table below may include changes in fair value that are attributable to both observable inputs (Levels 1 and 2) and unobservable inputs (Level 3). Further, it should be noted that the following tables do not take into consideration the effect of offsetting Level 1 and 2 financial instruments entered into by the Company that are either economically hedged by certain exposures to the Level 3 positions or that hedge the exposures in Level 3 positions.
In general, Level 3 assets include securities for which values were obtained from brokers where either significant inputs were utilized in determining the values that were difficult to corroborate with observable market data, or sufficient information regarding the specific inputs utilized by the broker was not available to support a Level 2 classification. Transfers into or out of Level 3 primarily arise as a result of the valuations utilized by the Company changing between either those provided by independent pricing services that do not contain significant unobservable inputs and other valuations sourced from brokers that are considered Level 3.
There were no significant transfers between Level 1 and Level 2 during each of the three months ended March 31, 2015 and 2014.
	Level 3 Assets and Liabilities -Three Months Ended March 31, 2015
(U.S. dollars in thousands)	Corporate			RMBS - Agency			RMBS - Non			CMBS			CDO
							Agency
Balance, beginning of period	$	5,894		$	1,910		$	—		$	—		$	687,958
Realized gains (losses)	(1		)	—			—			—			36
Movement in unrealized gains (losses)	48			(1		)	—			—			5,555
Purchases and issuances	—			—			—			—			—
Sales	—			—			—			—			(155,085		)
Settlements	(80		)	(89		)	—			—			(41,541		)
Transfers into Level 3				—			—			—			—
Transfers out of Level 3	—			—			—			—			—
Fixed maturities to short-term investments classification change	—			—			—			—			—
Balance, end of period	$	5,861		$	1,820		$	—		$	—		$	496,923
Movement in total gains (losses) above relating to instruments still held at the reporting date	$	48		$	(1	)	$	—		$	—		$	2,668
	Level 3 Assets and Liabilities -Three Months Ended March 31, 2015
(U.S. dollars in thousands)	Other asset-			Non-US Sovereign			Short-term			Other investments			Derivative Contracts
	backed			Government,			investments						- Net
	securities			Provincial,
				Supranational and
				Government
				Related/Supported
Balance, beginning of period	$	5,288		$	—		$	—		$	185,083		$	(9,764	)
Realized gains (losses)	(1		)	—			—			1,302			—
Movement in unrealized gains (losses)	2			—			—			(1,827		)	158
Purchases and issuances	—			—			—			6,793			—
Sales	—			—			—			—
Settlements	(3,045		)	—			—			(1,254		)	—
Transfers into Level 3	—			—			—			—			—
Transfers out of Level 3	—			—			—			—			—
Fixed maturities to short-term investments classification change	—			—			—			—			—
Balance, end of period	$	2,244		$	—		$	—		$	190,097		$	(9,606	)
Movement in total gains (losses) above relating to instruments still held at the reporting date	$	—		$	—		$	—		$	(524	)	$	158
	Level 3 Assets and Liabilities -Three Months Ended March 31, 2014
(U.S. dollars in thousands)	Corporate			RMBS - Agency			RMBS - Non			CMBS			CDO
							Agency
Balance, beginning of period	$	31,573		$	10,473		$	9		$	12,533		$	710,253
Realized gains (losses)	120			(1		)	—			2			1,581
Movement in unrealized gains (losses)	(2		)	1			2			(3		)	3,681
Purchases and issuances	1,434			—			—			—			27,814
Sales	—			—			—			—			(9,931		)
Settlements	(5,114		)	(573		)	—			(6,606		)	(14,571		)
Transfers into Level 3	—			—			—			—			—
Transfers out of Level 3	(23,629		)	(972		)	—			—			—
Fixed maturities to short-term investments classification change	—			—			—			—			—
Balance, end of period	$	4,382		$	8,928		$	11		$	5,926		$	718,827
Movement in total gains (losses) above relating to instruments still held at the reporting date	$	148		$	—		$	2		$	—		$	4,969
	Level 3 Assets and Liabilities -Three Months Ended March 31, 2014
(U.S. dollars in thousands)	Other asset-			Non-US Sovereign			Short-term			Other investments			Derivative Contracts
	backed			Government,			investments						- Net
	securities			Provincial,
				Supranational and
				Government
				Related/Supported
Balance, beginning of period	$	11,877		$	—		$	2,015		$	113,472		$	(29,110	)
Realized gains (losses)	(15		)	—			—			3,566			—
Movement in unrealized gains (losses)	62			—			(15		)	1,494			(3,386		)
Purchases and issuances	—			—			—			11,089			—
Sales	—			—			—			—			—
Settlements	(1,251		)	—			(2,000		)	(13,203		)	—
Transfers into Level 3	—			—			—			—			—
Transfers out of Level 3	—			—			—			—			—
Fixed maturities to short-term investments classification change	—			—			—			—			—
Balance, end of period	$	10,673		$	—		$	—		$	116,418		$	(32,496	)
Movement in total gains (losses) above relating to instruments still held at the reporting date	$	46		$	—		$	—		$	5,061		$	(3,386	)
(c) Fixed maturities and short-term investments
The Company’s Level 3 assets consist primarily of CDOs, for which non-binding broker quotes are the primary source of the valuations. Sufficient information regarding the specific inputs utilized by the brokers was not available to support a Level 2 classification. The Company obtains the majority of broker quotes for these CDOs from third party investment managers who perform independent verifications of these valuations using pricing matrices based upon information gathered by market traders. In addition, for the majority of these securities, the Company compares the broker quotes to independent valuations obtained from third party pricing vendors, which may also consist of broker quotes, to assess if the prices received represent a reasonable estimate of the fair value. Although the Company does not have access to the specific unobservable inputs that may have been used in the fair value measurements of the CDO securities provided by brokers, we would expect that the significant inputs considered are prepayment rates, probability of default, loss severity in the event of default, recovery rates, liquidity premium and reinvestment rates. Significant increases (decreases) in any of those inputs in isolation could result in a significantly different fair value measurement. Generally, a change in the assumption used for the probability of default is accompanied by a directionally similar change in the assumption used for the loss severity and a directionally opposite change in the assumption used for prepayment rates.
The remainder of the Level 3 assets relate primarily to private investment funds and certain derivative positions as described below.
(d) Other investments
Included within the Other investments component of the Company’s Level 3 valuations are private investments and alternative fund investments where the Company is not deemed to have significant influence over the investee. The fair value of these investments is based upon net asset values received from the investment manager or general partner of the respective entity. The nature of the underlying investments held by the investee that form the basis of the net asset value include assets such as private business ventures and are such that significant Level 3 inputs are utilized in the determination of the individual underlying holding values and, accordingly, the fair value of the Company’s investment in each entity is classified within Level 3. The Company has not adjusted the net asset values received; however, management incorporates factors such as the most recent financial information received, annual audited financial statements and the values at which capital transactions with the investee take place when applying judgment regarding whether any adjustments should be made to the net asset value in recording the fair value of each position. Investments in alternative funds included in Other investments utilize strategies including arbitrage, directional, event driven and multi-style. These funds potentially have lockup and gate provisions which may limit redemption liquidity. For further details regarding the nature of Other investments and related features see Item 8, Note 8, “Other Investments,” to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014.
(e) Derivative instruments
Derivative instruments recorded within Other liabilities and classified within Level 3 include credit derivatives sold providing protection on senior tranches of structured finance transactions where the value is obtained directly from the investment bank counterparty and sufficient information regarding the inputs utilized in such valuation was not obtained to support a Level 2 classification and guaranteed minimum income benefits embedded within one reinsurance contract. The majority of inputs utilized in the valuations of these types of derivative contracts are considered Level 1 or Level 2; however, each valuation includes at least one Level 3 input that was significant to the valuation and, accordingly, the values are disclosed within Level 3.
The calculation of the change in fair value of the embedded derivative associated with the Life Retro Arrangements includes the interest income, realized and unrealized gains and losses on Life Funds Withheld Assets and certain related expenses related to the Life Funds Withheld Assets. The fair value of the embedded derivative is included in “Funds withheld on life retrocession arrangements, net of future policy benefit reserves recoverable” on the consolidated balance sheets. The fair value of the embedded derivative is considered a Level 2 valuation.
(f) Financial Instruments Not Carried at Fair Value
Authoritative guidance over disclosures about the fair value of financial instruments requires additional disclosure of fair value information for financial instruments not carried at fair value in both interim and annual reporting periods. Certain financial instruments, particularly insurance contracts, are excluded from these fair value disclosure requirements. The carrying values of cash and cash equivalents, accrued investment income, net receivable from investments sold, other assets, net payable for investments purchased, other liabilities and other financial instruments not included below approximated their fair values. The following table includes financial instruments for which the carrying value differs from the estimated fair values as of March 31, 2015 and December 31, 2014. All of these fair value estimates are considered Level 2 fair value measurements. The fair values for fixed maturities held to maturity are provided by third party pricing vendors and significant valuation inputs for all other items included were based upon market data obtained from sources independent of the Company, and are subject to the same control environment previously described.
	March 31, 2015						December 31, 2014
(U.S. dollars in thousands)	Carrying			Fair			Carrying			Fair
	Value			Value			Value			Value
Financial Assets - Other investments, structured transactions	$	354,352		$	367,491		$	354,382		$	371,625
Deposit liabilities	$	1,211,203		$	1,528,570		$	1,245,367		$	1,543,761
Notes payable and debt	2,643,561			2,957,605			1,662,580			1,897,854
Financial Liabilities	$	3,854,764		$	4,486,175		$	2,907,947		$	3,441,615
The Company historically participated in structured transactions. Remaining structured transactions include cash loans supporting project finance transactions, a liquidity facility financing provided to structured project deals and an investment in a payment obligation with an insurance company. These transactions are carried at amortized cost. The fair value of these investments held by the Company is determined through use of internal models utilizing reported trades, benchmark yields, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers and reference data.
Deposit liabilities include obligations under structured insurance and reinsurance transactions. For purposes of fair value disclosures, the Company determined the estimated fair value of the deposit liabilities by assuming a discount rate equal to the appropriate U.S. Treasury rate plus 33.4 basis points and 29.5 basis points as of March 31, 2015 and December 31, 2014, respectively. The discount rate incorporates the Company’s own credit risk into the determination of estimated fair value.
The fair values of the Company’s notes payable and debt outstanding were determined based on quoted market prices.
There are no significant concentrations of credit risk within the Company’s financial instruments as defined in the authoritative guidance over disclosures of fair value of financial instruments not carried at fair value, which excludes certain financial instruments, particularly insurance contracts.

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Segment Information	Segment Information
	The Company is organized into two operating segments: Insurance and Reinsurance. Subsequent to the transaction as described in Note 3(c), "Acquisition and Disposals - Sale of Life Reinsurance Subsidiary," GCLR reinsures the majority of the Company's life reinsurance business through the Life Retro Arrangements. The Company no longer considers the Life Operations to be a separate operating segment and the results of the Run-Off Life Operations are reported within “Corporate and Other.” The Company’s general investment and financing operations are also reflected in Corporate and Other. The run-off business subject to the Life Retro Arrangements was, prior to June 30, 2014, reported within the Company’s Life operations segment. Prior period information has been recast to reflect the current presentation.
	The Company evaluates the performance of both the Insurance and Reinsurance segments based on underwriting profit. Other items of revenue and expenditure of the Company are not evaluated at the segment level. In addition, the Company does not allocate investment assets used to support its Property and Casualty (“P&C”) operations to the individual segments, except as noted below. Investment assets related to the Company’s Run-Off Life Operations and certain structured products included in the Insurance and Reinsurance segments are held in separately identified portfolios. As such, net investment income from these assets is included in the contribution from the applicable segment or in Corporate and Other. The following tables summarize the segment results for the three months ended March 31, 2015 and 2014:
	Three Months Ended March 31, 2015	Insurance			Reinsurance			Total P&C			Corporate			Total
	(U.S. dollars in thousands, except ratios)										and Other (1)
	Gross premiums written	$	1,654,747		$	825,662		$	2,480,409		$	74,951		$	2,555,360
	Net premiums written	1,089,108			747,635			1,836,743			14,506			1,851,249
	Net premiums earned	962,306			357,188			1,319,494			14,506			1,334,000
	Net losses and loss expenses	616,947			152,880			769,827			19,387			789,214
	Acquisition costs	80,387			71,492			151,879			1,817			153,696
	Operating expenses (2)	208,457			42,495			250,952			931			251,883
	Underwriting profit (loss)	$	56,515		$	90,321		$	146,836		$	(7,629	)	$	139,207
	Net investment income - excluding Life Funds Withheld Assets (3)							132,808			10,210			143,018
	Net investment income - Life Funds Withheld Assets										50,419			50,419
	Net results from structured products (4)	2,905			2,120			5,025			—			5,025
	Net fee income and other (5)	(7,465		)	825			(6,640		)	132			(6,508		)
	Net realized gains (losses) on investments - excluding Life Funds Withheld Assets							5,807			(1,205		)	4,602
	Net realized gains (losses) on investments and net unrealized gains (losses) on investments, Trading - Life Funds Withheld Assets							—			48,289			48,289
	Net realized and unrealized gains (losses) on derivative instruments							—			16,521			16,521
	Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets							—			(229,367		)	(229,367		)
	Net income (loss) from investment fund affiliates and operating affiliates (6)							—			57,997			57,997
	Exchange (gains) losses							—			27,390			27,390
	Corporate operating expenses							—			62,443			62,443
	Contribution from P&C and Corporate and Other							283,836			(144,466		)	139,370
	Interest expense (7)										41,481			41,481
	Non-controlling interests										37,390			37,390
	Income tax expense										24,218			24,218
	Net income (loss) attributable to ordinary shareholders													$	36,281
	Ratios – P&C operations: (8)
	Loss and loss expense ratio	64.1		%	42.8		%	58.3		%
	Underwriting expense ratio	30		%	31.9		%	30.6		%
	Combined ratio	94.1		%	74.7		%	88.9		%
	____________
	-1	Corporate and Other includes other items of our revenue and expenditures that are not evaluated at the segment level for reporting purposes, as well as the Company's Run-Off Life Operations.
	-2	Operating expenses of the segments exclude Corporate operating expenses, shown separately.
	-3	Net investment income - excluding Life Funds Withheld Assets does not include net investment income related to the net results from structured products.
	-4	The net results from P&C structured products include net investment income and interest expense of $15.1 million and $10.0 million, respectively.
	-5	Net fee income and other includes operating expenses from the Company's loss prevention consulting services business.
	-6	The Company generally records the income related to the alternative funds and to the private investment and operating fund affiliates on a one-month and three-month lag, respectively.
	-7	Interest expense excludes interest expense related to deposit liabilities recorded in the Insurance and Reinsurance segments.
	-8	Ratios are based on net premiums earned from P&C operations.
	Three Months Ended March 31, 2014	Insurance			Reinsurance			Total P&C			Corporate			Total
	(U.S. dollars in thousands, except ratios)										and Other (1)
	Gross premiums written	$	1,570,926		$	857,713		$	2,428,639		$	84,297		$	2,512,936
	Net premiums written	1,127,367			792,173			1,919,540			76,311			1,995,851
	Net premiums earned	992,440			420,088			1,412,528			76,311			1,488,839
	Net losses and loss expenses	639,193			192,312			831,505			113,587			945,092
	Acquisition costs	105,000			87,235			192,235			7,179			199,414
	Operating expenses (2)	203,053			40,861			243,914			3,188			247,102
	Underwriting profit (loss)	$	45,194		$	99,680		$	144,874		$	(47,643	)	$	97,231
	Net investment income - excluding Life Funds Withheld Assets (3)							143,527			70,892			214,419
	Net results from structured products (4)	4,890			3,063			7,953			—			7,953
	Net fee income and other (5)	(1,212		)	673			(539		)	45			(494		)
	Net realized gains (losses) on investments - excluding Life Funds Withheld Assets							17,666			1,563			19,229
	Net realized and unrealized gains (losses) on derivative instruments							—			1,810			1,810
	Net income (loss) from investment fund affiliates and operating affiliates (6)							—			79,588			79,588
	Exchange (gains) losses							—			10,441			10,441
	Corporate operating expenses							—			51,338			51,338
	Contribution from P&C and Corporate and Other							313,481			44,476			357,957
	Interest expense (7)										32,160			32,160
	Non-controlling interests										35,759			35,759
	Income tax expense										34,321			34,321
	Net income (loss) attributable to ordinary shareholders													$	255,717
	Ratios – P&C operations: (8)
Loss and loss expense ratio	64.4		%	45.8		%	58.9		%
Underwriting expense ratio	31		%	30.5		%	30.8		%
Combined ratio	95.4		%	76.3		%	89.7		%
____________
-1	Corporate and Other includes other items of our revenue and expenditures that are not evaluated at the segment level for reporting purposes, as well as the Company's Run-Off Life Operations and Life Funds Withheld Assets since the sale of XLLR did not occur until May 1, 2014.
-2	Operating expenses of the segments exclude Corporate operating expenses, shown separately.
-3	Net investment income does not include net investment income related to the net results from structured products.
-4	The net results from P&C structured products include net investment income and interest expense of $18.8 million and $10.8 million, respectively.
-5	Net fee income and other includes operating expenses from the Company's loss prevention consulting services business.
-6	The Company generally records the income related to the alternative funds and to the private investment and operating fund affiliates on a one-month and three-month lag, respectively.
-7	Interest expense excludes interest expense related to deposit liabilities recorded in the Insurance and Reinsurance segments.
-8	Ratios are based on net premiums earned from P&C operations.
The following tables summarize the Company’s net premiums earned by line of business for the three months ended March 31, 2015 and 2014:
Three Months Ended March 31, 2015	Insurance			Reinsurance			Corporate			Total
(U.S. dollars in thousands)							and Other
P&C Operations:
Professional	$	266,411		$	35,008		$	—		$	301,419
Casualty	309,335			58,208			—			367,543
Property catastrophe	—			94,073			—			94,073
Property	128,241			131,224			—			259,465
Marine, energy, aviation and satellite	—			18,075			—			18,075
Specialty	184,724			—			—			184,724
Other (1)	73,595			20,600			—			94,195
Total P&C Operations	$	962,306		$	357,188		$	—		$	1,319,494
Corporate and Other:
Run-off Life operations - Annuity	$	—		$	—		$	(1	)	$	(1	)
Run-off Life operations - Other Life	—			—			14,507			14,507
Total Corporate and Other	$	—		$	—		$	14,506		$	14,506
Total	$	962,306		$	357,188		$	14,506		$	1,334,000
Three Months Ended March 31, 2014	Insurance			Reinsurance			Corporate			Total
(U.S. dollars in thousands)							and Other
P&C Operations:
Professional	$	275,427		$	50,104		$	—		$	325,531
Casualty	344,004			76,721			—			420,725
Property catastrophe	—			108,437			—			108,437
Property	139,733			135,239			—			274,972
Marine, energy, aviation and satellite	—			23,514			—			23,514
Specialty	176,909			—			—			176,909
Other (1)	56,367			26,073			—			82,440
Total P&C Operations	$	992,440		$	420,088		$	—		$	1,412,528
Corporate and Other:
Run-off Life operations - Annuity	$	—		$	—		$	31,797		$	31,797
Run-off Life operations - Other Life	—			—			44,514			44,514
Total Corporate and Other	$	—		$	—		$	76,311		$	76,311
Total	$	992,440		$	420,088		$	76,311		$	1,488,839
____________
-1	Other within the Insurance segment includes: excess and surplus, programs, surety, structured indemnity and certain discontinued lines. Other within the Reinsurance segment includes: whole account contracts, accident and health and other lines.

Investments

Investments	3 Months Ended
	Mar. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Investments	Investments
	(a) Fixed Maturities, Short-Term Investments and Equity Securities
	Classification of Fixed Income Securities
	During the second quarter of 2014, fixed maturities with a carrying value of $2.8 billion were reclassified from held to maturity ("HTM") to AFS in conjunction with the sale of XLLR as discussed in Note 3(c), “Acquisition and Disposals - Sale of Life Reinsurance Subsidiary." As a result, the Company no longer holds HTM securities. Gross unrealized gains and gross unrealized losses, net of tax, of $424.9 million and nil, respectively, related to these securities were recognized in other comprehensive income on the date of transfer. For certain annuity contracts that are subject to the Life Retro Arrangements, policy benefit reserves were historically increased for the impact of changes in unrealized gains on investments supporting such contracts as if the gains had been realized, with a corresponding entry to other comprehensive income ("Shadow Adjustments"). In conjunction with the sale of XLLR and the related reclassification of securities from HTM to AFS, the Company recorded an additional gross charge of $440.5 million, net of tax, as a reduction of comprehensive income for such Shadow Adjustments on the date of the transfer. See Note 15, "Accumulated Other Comprehensive Income (Loss)," for further information.
	All of the reclassified securities are included within the Life Funds Withheld Assets, along with certain other available for sale securities as defined in the sale and purchase agreement. The Life Funds Withheld Assets are managed pursuant to agreed investment guidelines that meet the contractual commitments of the XL ceding companies and applicable laws and regulations. All of the investment results associated with the Life Funds Withheld Assets ultimately accrue to GCLR. Because the Company no longer shares in the risks and rewards of the underlying performance of the Life Funds Withheld Assets, disclosures within the financial statements and accompanying notes included herein separate the Life Funds Withheld Assets from the rest of the Company's investments.
	Amortized Cost and Fair Value Summary
	The cost (amortized cost for fixed maturities and short-term investments), fair value, gross unrealized gains and gross unrealized (losses), including OTTI recorded in accumulated other comprehensive income (“AOCI”) of the Company’s AFS investments as of March 31, 2015 and December 31, 2014, were as follows:
	31-Mar-15	Cost or			Gross			Gross Unrealized Losses			Fair Value			Non-credit Related OTTI (1)
	(U.S. dollars in thousands)	Amortized			Unrealized
		Cost			Gains
	Fixed maturities - AFS - Excluding Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	3,299,458		$	87,025		$	(8,141	)	$	3,378,342		$	—
	Corporate (2)	7,806,607			398,357			(50,326		)	8,154,638			(3,309		)
	RMBS – Agency	3,585,638			131,468			(5,772		)	3,711,334			—
	RMBS – Non-Agency	368,317			29,770			(17,952		)	380,135			(58,364		)
	CMBS	1,010,518			25,603			(3,401		)	1,032,720			(1,801		)
	CDO	520,929			1,675			(21,630		)	500,974			(1,648		)
	Other asset-backed securities (2)	1,134,928			41,386			(8,947		)	1,167,367			(1,662		)
	U.S. States and political subdivisions of the States	1,842,561			131,843			(1,264		)	1,973,140			—
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	4,010,656			154,829			(71,714		)	4,093,771			—
	Total fixed maturities - AFS - Excluding Life Funds Withheld Assets	$	23,579,612		$	1,001,956		$	(189,147	)	$	24,392,421		$	(66,784	)
	Total short-term investments - Excluding Life Funds Withheld Assets	$	169,903		$	149		$	(1,190	)	$	168,862		$	—
	Total equity securities - Excluding Life Funds Withheld Assets	$	665,682		$	132,731		$	(14,942	)	$	783,471		$	—
	Total investments - AFS - Excluding Life Funds Withheld Assets	$	24,415,197		$	1,134,836		$	(205,279	)	$	25,344,754		$	(66,784	)
	Fixed maturities - AFS - Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	13,163		$	4,450		$	—		$	17,613		$	—
	Corporate (2)	2,277,295			468,931			—			2,746,226			—
	RMBS – Agency	1,641			489			—			2,130			—
	RMBS – Non-Agency	32,880			5,928			—			38,808			—
	CMBS	131,830			27,427			—			159,257			—
	Other asset-backed securities	209,714			34,426			—			244,140			—
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	1,123,966			385,839			—			1,509,805			—
	Total fixed maturities - AFS - Life Funds Withheld Assets	$	3,790,489		$	927,490		$	—		$	4,717,979		$	—
	Total investments - AFS	$	28,205,686		$	2,062,326		$	(205,279	)	$	30,062,733		$	(66,784	)
	Fixed maturities - Trading - Life Funds Withheld Assets										Amortized Cost			Fair Value
	Corporate										$	136,681		$	137,438
	Other asset-backed securities										1,966			1,939
	Total investments - Trading - Life Funds Withheld Assets										$	138,647		$	139,377
	___________
	-1	Represents the non-credit component of OTTI losses, adjusted for subsequent sales of securities. It does not include the change in fair value subsequent to the date an impairment was recorded.
	-2	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes have a fair value of $74.8 million and an amortized cost of $63.8 million. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.
	31-Dec-14	Cost or			Gross			Gross Unrealized Losses			Fair Value			Non-credit Related OTTI (1)
	(U.S. dollars in thousands)	Amortized			Unrealized
		Cost			Gains
	Fixed maturities - AFS - Excluding Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	2,100,851		$	77,889		$	(6,787	)	$	2,171,953		$	—
	Corporate (2)	8,462,130			365,805			(49,562		)	8,778,373			(3,309		)
	RMBS – Agency	3,625,171			114,188			(10,783		)	3,728,576			—
	RMBS – Non-Agency	404,398			41,108			(18,155		)	427,351			(67,918		)
	CMBS	1,033,819			23,987			(5,262		)	1,052,544			(2,033		)
	CDO	717,544			1,659			(27,169		)	692,034			(1,663		)
	Other asset-backed securities (2)	1,028,528			42,810			(6,045		)	1,065,293			(1,797		)
	U.S. States and political subdivisions of the States	1,892,566			129,910			(1,204		)	2,021,272			—
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	4,162,425			139,484			(61,836		)	4,240,073			—
	Total fixed maturities - AFS - Excluding Life Funds Withheld Assets	$	23,427,432		$	936,840		$	(186,803	)	$	24,177,469		$	(76,720	)
	Total short-term investments - Excluding Life Funds Withheld Assets	$	257,221		$	49		$	(543	)	$	256,727		$	—
	Total equity securities - Excluding Life Funds Withheld Assets	$	763,833		$	130,689		$	(26,230	)	$	868,292		$	—
	Total investments - AFS - Excluding Life Funds Withheld Assets	$	24,448,486		$	1,067,578		$	(213,576	)	$	25,302,488		$	(76,720	)
	Fixed maturities - AFS - Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	14,866		$	3,858		$	—		$	18,724		$	—
	Corporate (2)	2,407,849			410,131			—			2,817,980			—
	RMBS – Agency	3,301			481			—			3,782			—
	RMBS – Non-Agency	71,075			14,260			—			85,335			—
	CMBS	168,886			24,281			—			193,167			—
Other asset-backed securities	238,168			35,373			—			273,541			—
Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	1,397,194			391,842			—			1,789,036			—
Total fixed maturities - AFS - Life Funds Withheld Assets	$	4,301,339		$	880,226		$	—		$	5,181,565		$	—
Total investments - AFS	$	28,749,825		$	1,947,804		$	(213,576	)	$	30,484,053		$	(76,720	)
Fixed maturities - Trading - Life Funds Withheld Assets										Amortized Cost			Fair Value
Corporate										$	1,180		$	1,171
Total investments - Trading - Life Funds Withheld Assets										$	1,180		$	1,171
____________
-1	Represents the non-credit component of OTTI losses, adjusted for subsequent sales of securities. It does not include the change in fair value subsequent to the date an impairment was recorded.
-2	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes have a fair value of $79.9 million and an amortized cost of $68.4 million. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.
As of March 31, 2015 and December 31, 2014, approximately 2.8% and 3.0%, respectively, of the Company's fixed income investment portfolio at fair value, excluding Life Funds Withheld Assets, was invested in securities that were below investment grade or not rated. Approximately 23.1% and 24.9% of the gross unrealized losses in the Company's fixed income investment portfolio, excluding Life Funds Withheld Assets, as of March 31, 2015 and December 31, 2014, respectively, related to securities that were below investment grade or not rated.
Contractual Maturities Summary
The contractual maturities of AFS fixed income securities at March 31, 2015 and December 31, 2014 are shown below. Actual maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.
	31-Mar-15						31-Dec-14
(U.S. dollars in thousands)	Amortized			Fair			Amortized			Fair
	Cost			Value			Cost			Value
Fixed maturities - AFS - Excluding Life Funds Withheld Assets
Due less than one year	$	1,770,647		$	1,781,224		$	1,972,224		$	1,980,429
Due after 1 through 5 years	9,698,659			9,923,517			8,919,037			9,113,651
Due after 5 through 10 years	4,049,907			4,226,001			4,232,396			4,412,569
Due after 10 years	1,440,069			1,669,149			1,494,315			1,705,022
	$	16,959,282		$	17,599,891		$	16,617,972		$	17,211,671
RMBS – Agency	3,585,638			3,711,334			3,625,171			3,728,576
RMBS – Non-Agency	368,317			380,135			404,398			427,351
CMBS	1,010,518			1,032,720			1,033,819			1,052,544
CDO	520,929			500,974			717,544			692,034
Other asset-backed securities	1,134,928			1,167,367			1,028,528			1,065,293
Total mortgage and asset-backed securities	$	6,620,330		$	6,792,530		$	6,809,460		$	6,965,798
Total fixed maturities - AFS - Excluding Life Funds Withheld Assets	$	23,579,612		$	24,392,421		$	23,427,432		$	24,177,469
Fixed maturities - AFS - Life Funds Withheld Assets
Due less than one year	$	97,637		$	107,530		$	117,048		$	125,326
Due after 1 through 5 years	626,869			676,507			638,526			685,787
Due after 5 through 10 years	798,923			933,986			1,004,698			1,165,348
Due after 10 years	1,890,995			2,555,621			2,059,637			2,649,279
	$	3,414,424		$	4,273,644		$	3,819,909		$	4,625,740
RMBS – Agency	1,641			2,130			3,301			3,782
RMBS – Non-Agency	32,880			38,808			71,075			85,335
CMBS	131,830			159,257			168,886			193,167
Other asset-backed securities	209,714			244,140			238,168			273,541
Total mortgage and asset-backed securities	$	376,065		$	444,335		$	481,430		$	555,825
Total fixed maturities - AFS - Life Funds Withheld Assets	$	3,790,489		$	4,717,979		$	4,301,339		$	5,181,565
Total fixed maturities - AFS	$	27,370,101		$	29,110,400		$	27,728,771		$	29,359,034
Fixed maturities - Trading - Life Funds Withheld Assets
Due less than one year	$	—		$	—		$	—		$	—
Due after 1 through 5 years	64,739			64,733			—			—
Due after 5 through 10 years	5,188			5,131			1,180			1,171
Due after 10 years	66,754			67,574			—			—
	$	136,681		$	137,438		$	1,180		$	1,171
Other asset-backed securities	1,966			1,939			—			—
Total mortgage and asset-backed securities	$	1,966		$	1,939		$	—		$	—
Total fixed maturities - Trading - Life Funds Withheld Assets	$	138,647		$	139,377		$	1,180		$	1,171
OTTI Considerations
Under final authoritative accounting guidance, a debt security for which amortized cost exceeds fair value is deemed to be other-than-temporarily impaired if it meets either of the following conditions: (a) the Company intends to sell, or it is more likely than not that the Company will be required to sell, the security before a recovery in value, or (b) the Company does not expect to recover the entire amortized cost basis of the security. Other than in a situation in which the Company has the intent to sell a debt security or more likely than not will be required to sell a debt security, the amount of the OTTI related to a credit loss on the security is recognized in earnings, and the amount of the OTTI related to other factors (e.g., interest rates, market conditions, etc.) is recorded as a component of OCI. The net amount recognized in earnings (“credit loss impairment”) represents the difference between the amortized cost of the security and the net present value of its projected future cash flows discounted at the effective interest rate implicit in the debt security prior to impairment (“NPV”). The remaining difference between the security's NPV and its fair value is recognized in OCI. Subsequent changes in the fair value of these securities are included in OCI unless a further impairment is deemed to have occurred.
In the scenario where the Company has the intent to sell a security in which its amortized cost exceeds its fair value, or it is more likely than not that it will be required to sell such a security, the entire difference between the security's amortized cost and its fair value is recognized in earnings.
The determination of credit loss impairment is based on detailed analyses of underlying cash flows and other considerations. Such analyses require the use of certain assumptions to develop the estimated performance of underlying collateral. Key assumptions used include, but are not limited to, items such as RMBS default rates based on collateral duration in arrears, severity of losses on default by collateral class, collateral reinvestment rates and expected future general corporate default rates.
Factors considered for all securities on a quarterly basis in determining that a gross unrealized loss is not other-than-temporarily impaired include management's consideration of current and near term liquidity needs and other available sources of funds, an evaluation of the factors and time necessary for recovery and an assessment of whether the Company has the intention to sell or considers it more likely than not that it will be forced to sell a security.
Pledged Assets
Certain of the Company's invested assets are held in trust and pledged in support of insurance and reinsurance liabilities as well as credit facilities. Such pledges are largely required by the Company's operating subsidiaries that are “non-admitted” under U.S. state insurance regulations, in order for the U.S. cedant to receive statutory credit for reinsurance. Also, certain deposit liabilities and annuity contracts require the use of pledged assets. As of March 31, 2015, the Company had $15.4 billion in pledged assets which includes $1.0 billion of cash, cash equivalents and U.S. government securities held in escrow in relation to the Acquisition and the associated Bridge Facility. See "Note 3(a), "Acquisition and Disposals - Catlin Acquisition," for further information on the Bridge Facility. At December 31, 2014, the Company had $15.2 billion in pledged assets.
(b) Gross Unrealized Losses
The following is an analysis of how long the AFS securities as of March 31, 2015 and December 31, 2014 had been in a continual unrealized loss position:
	Less than 12 months						Equal to or greater
							than 12 months
31-Mar-15	Fair			Gross			Fair			Gross
(U.S. dollars in thousands)	Value			Unrealized			Value			Unrealized
				Losses						Losses
Fixed maturities and short-term investments - AFS
U.S. Government and Government-Related/Supported	$	249,646		$	(3,541	)	$	143,891		$	(4,619	)
Corporate	688,725			(40,874		)	190,397			(9,730		)
RMBS – Agency	177,627			(914		)	279,354			(4,858		)
RMBS – Non-Agency	51,876			(1,815		)	188,932			(16,137		)
CMBS	120,862			(393		)	109,324			(3,008		)
CDO	92,517			(294		)	346,372			(21,336		)
Other asset-backed securities	92,193			(6,219		)	37,357			(2,728		)
U.S. States and political subdivisions of the States	55,707			(695		)	15,310			(569		)
Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	681,300			(39,085		)	322,974			(33,522		)
Total fixed maturities and short-term investments - AFS	$	2,210,453		$	(93,830	)	$	1,633,911		$	(96,507	)
Total equity securities	$	119,625		$	(14,942	)	$	—		$	—
	Less than 12 months						Equal to or greater
							than 12 months
31-Dec-14	Fair			Gross			Fair			Gross
(U.S. dollars in thousands)	Value			Unrealized			Value			Unrealized
				Losses						Losses
Fixed maturities and short-term investments - AFS
U.S. Government and Government-Related/Supported	$	251,091		$	(1,196	)	$	342,890		$	(5,603	)
Corporate	1,337,470			(33,881		)	424,221			(15,754		)
RMBS – Agency	134,535			(220		)	512,652			(10,563		)
RMBS – Non-Agency	45,378			(1,358		)	202,700			(16,797		)
CMBS	78,356			(385		)	169,065			(4,877		)
CDO	249,803			(2,666		)	414,516			(24,503		)
Other asset-backed securities	143,044			(2,813		)	57,544			(3,232		)
U.S. States and political subdivisions of the States	32,187			(210		)	63,695			(994		)
Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	624,346			(19,043		)	558,422			(43,251		)
Total fixed maturities and short-term investments - AFS	$	2,896,210		$	(61,772	)	$	2,745,705		$	(125,574	)
Total equity securities	$	191,193		$	(26,230	)	$	—		$	—
The Company had gross unrealized losses totaling $205.3 million on 1,347 securities out of a total of 7,586 held as of March 31, 2015 in its AFS - Excluding Life Funds Withheld Assets portfolio, which either it considers to be temporarily impaired or with respect to which it reflects non-credit losses on other-than-temporarily impaired assets. Individual security positions comprising this balance have been evaluated by management to determine the severity of these impairments and whether they should be considered other-than-temporary. Management believes it is more likely than not that the issuer will be able to fund sufficient principal and interest payments to support the current amortized cost.
Management, in its assessment of whether securities in a gross unrealized loss position are temporarily impaired, as described above, considers the significance of the impairments. As of March 31, 2015, the AFS - Excluding Life Funds Withheld Assets portfolio included structured credit securities with gross unrealized losses of $9.0 million, which had a fair value of $6.1 million, and a cumulative fair value decline of greater than 50% of amortized cost. All of these securities are mortgage and asset-backed securities.
(c) Net Realized Gains (Losses)
The following represents an analysis of net realized gains (losses) on investments:
Net Realized Gains (Losses) on Investments	Three months ended March 31,
(U.S. dollars in thousands)	2015			2014
Net realized gains (losses) on investments - excluding Life Funds Withheld Assets:
Gross realized gains	$	62,300		$	51,213
Gross realized losses on investments sold	(47,122		)	(28,257		)
OTTI on investments, net of amounts transferred to other comprehensive income	(10,576		)	(3,727		)
	$	4,602		$	19,229
Net realized gains (losses) on investments and net unrealized gains (losses) on investments, Trading - Life Funds Withheld Assets:
Gross realized gains	$	53,128		$	—
Gross realized losses on investments sold	(390		)	—
OTTI on investments, net of amounts transferred to other comprehensive income	(5,209		)	—
Net unrealized gains (losses) on trading securities	$	760		$	—
	$	48,289		$	—
Total net realized gains (losses) on investments	$	52,891		$	19,229
The significant components of the net impairment charges of $10.6 million for investments excluding Life Funds Withheld Assets for the three months ended March 31, 2015 were:
▪	$7.6 million related to certain high yield securities which we no longer intend to hold for a period sufficient to recover their fair value to amortized cost.
•	$0.3 million related to certain equities that were in a loss position for more than 11 months.
•	$0.1 million for structured securities, principally non-Agency RMBS, where we determined that the likely recovery on these securities was below the carrying value and, accordingly, recorded an impairment of the securities to the discounted value of the cash flows expected to be received on these securities.
•	$2.6 million related to foreign exchange losses.
The following table sets forth the amount of credit loss impairments on fixed income securities held by the Company for which a portion of the OTTI loss was recognized in OCI, as of the dates or for the periods indicated and the corresponding changes in such amounts.
Credit Loss Impairments	Three months ended March 31,
(U.S. dollars in thousands)	2015			2014
Opening balance as of beginning of indicated period	$	131,942		$	174,805
Credit loss impairment recognized in the current period on securities not previously impaired	7,560			12
Credit loss impairments previously recognized on securities which matured, paid down, prepaid or were sold during the period	(28,539		)	(3,348		)
Additional credit loss impairments recognized in the current period on securities previously impaired	141			2,261
Accretion of credit loss impairments previously recognized due to an increase in cash flows expected to be collected	(2,646		)	(2,347		)
Balance as of March 31,	$	108,458		$	171,383
During the three months ended March 31, 2015 and 2014, the $28.5 million and $3.3 million, respectively, credit loss impairments previously recognized on securities that matured, or were paid down, prepaid or sold, included $27.3 million and $2.7 million, respectively, of non-Agency RMBS.

Derivative_Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments
	The Company enters into derivative instruments for both risk management and investment purposes. The Company is exposed to potential loss from various market risks, and manages its market risks based on guidelines established by management and the Risk and Finance Committee of the Company's Board of Directors. The Company recognizes all derivatives as either assets or liabilities on the balance sheets and measures those instruments at fair value, with the changes in fair value of derivatives shown in the consolidated statement of income as “Net realized and unrealized gains (losses) on derivative instruments” unless the derivatives are designated as hedging instruments. The accounting for derivatives that are designated as hedging instruments is described in Item 8, Note 2(h), “Significant Accounting Policies - Derivative Instruments,” to the Consolidated Financial Statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2014.
	The following table summarizes information on the location and gross amounts of derivative fair values contained in the consolidated balance sheets as of March 31, 2015 and December 31, 2014:
		March 31, 2015											December 31, 2014
	(U.S. dollars in thousands)	Asset				Asset			Liability		Liability		Asset		Asset		Liability		Liability
		Derivative				Derivative			Derivative		Derivative		Derivative		Derivative		Derivative		Derivative
		Notional				Fair Value			Notional		Fair Value		Notional		Fair Value		Notional		Fair Value
		Amount				-1			Amount		-1		Amount		-1		Amount		-1
	Derivatives designated as hedging instruments:
	Foreign exchange contracts	$	204,811			$	38,376		$	204,811	$	26,505	$	2,300,609	$	121,862	$	302,211	$	2,936
	Total derivatives designated as hedging instruments	$	204,811			$	38,376		$	204,811	$	26,505	$	2,300,609	$	121,862	$	302,211	$	2,936
	Derivatives not designated as hedging instruments:
	Investment Related Derivatives:
	Interest rate exposure	$	264,527			$	224		$	13,033	$	65	$	394,597	$	206	$	20,782	$	51
	Foreign exchange exposure	23,400				498			190,368		7,709		7,385		403		288,376		4,724
	Credit exposure	2,408				205			14,270		9,836		2,408		165		14,270		9,836
	Financial market exposure	33,362				513			33,136		63		46,145		360		33,670		34
	Other Non-Investment Derivatives:
	Foreign exchange contracts	2,304,633				205,083			2,366,968		65,294		—		—		—		—
	Credit exposure	31,060				218			—		—		31,060		60		—		—
	Guaranteed minimum income benefit contract	45,658				12,763			45,658		12,763		46,249		13,603		46,249		13,603
	Modified coinsurance funds withheld contracts (2)	65,530				—			5,045,540		—		64,947		—		5,401,278		—
	Total derivatives not designated as hedging instruments	$	2,770,578			$	219,504		$	7,708,973	$	95,730	$	592,791	$	14,797	$	5,804,625	$	28,248
	____________
	-1	Derivative instruments in an asset or liability position are included within Other assets or Other liabilities, respectively, in the balance sheets on a net basis where the Company has both a legal right of offset and the intention to settle the contracts on a net basis.
	-2	The fair value movements in derivative assets and liabilities relating to modified coinsurance funds withheld contracts are included within the associated asset or liability at each period end on the face of the balance sheets. Notional amounts associated with reinsurance agreements under which the Company assumes reinsurance risk are recorded as asset derivative notional amounts. Notional amounts associated with the Life Retro Arrangements under which the Company cedes reinsurance risk are recorded as liability derivative notional amounts. Included in the liability derivative notional amount as of March 31, 2015 is the cumulative net realized and unrealized loss on life retrocession embedded derivative of $654.6 million.
	The following table summarizes information on the gross and net amounts of derivative fair values and associated collateral received related to derivative assets, or paid related to derivative liabilities, reported in other assets and or other liabilities within our consolidated balance sheets as of March 31, 2015 and December 31, 2014:
											Gross Amounts Not Offset in the Balance Sheets
	31-Mar-15	Gross Amounts Recognized in the Balance Sheets				Gross Amounts Offset in the Balance Sheets			Net Amounts in the Balance Sheets		Financial Instruments		Cash Collateral		Net Amounts
	(U.S. dollars in thousands)
	Derivative Assets	$	257,880			$	587		$	257,293	$	—	$	183,675	$	73,618
	Derivative Liabilities	$	122,235			$	587		$	121,648	$	—	$	—	$	121,648
	31-Dec-14
	(U.S. dollars in thousands)
	Derivative Assets	$	136,659			$	696		$	135,963	$	—	$	78,580	$	57,383
	Derivative Liabilities	$	31,184			$	696		$	30,488	$	—	$	—	$	30,488
	Derivative instruments in an asset or liability position are included within Other assets or Other liabilities, respectively, in the balance sheets on a net basis where the Company has both a legal right of offset and the intention to settle the contracts on a net basis. The Company often enters into different types of derivative contracts with a single counterparty and these contracts are covered under netting agreements. As of March 31, 2015 and December 31, 2014, the Company held cash collateral related to foreign currency derivative positions and certain other derivative positions of $183.7 million and $78.6 million, respectively. The assets and liabilities related to the net collateral paid or held were recorded as Other assets and Other liabilities within the balance sheets as the collateral and derivative positions are not intended to be settled on a net basis.
	(a) Derivative Instruments Designated as Fair Value Hedges
	The Company designates certain of its derivative instruments as fair value hedges or cash flow hedges and formally and contemporaneously documents all relationships between the hedging instruments and hedged items and links the hedging derivative to specific assets and liabilities. The Company assesses the effectiveness of the hedge both at inception and on an on-going basis, and determines whether the hedge is highly effective in offsetting changes in fair value or cash flows of the linked hedged item.
	The Company may use foreign exchange contracts to hedge the fair value of certain fixed income securities as well as to hedge certain net investments in foreign operations. In connection with the Acquisition and the FX Forward (defined below), certain foreign exchange contracts utilized to hedge the fair value of certain net investments in foreign operations were de-designated as hedging instruments during the quarter.
	The following table provides the total impact on earnings relating to derivative instruments formally designated as fair value hedges along with the impacts of the related hedged items for the three months ended March 31, 2015 and 2014:
					Hedged Items - Amount of Gain/(Loss) Recognized in Income Attributable to Risk
	Derivatives Designated as Fair Value Hedges:	Gain/(Loss)				Fixed Maturity			Ineffective
	Three Months Ended March 31, 2015	Recognized				Investments			Portion of
	(U.S. dollars in thousands)	in Income on							Hedging
		Derivative							Relationship -
									Gain/(Loss)
	Interest rate exposure	$	—
	Foreign exchange exposure	—
	Total	$	—			$	—		$	—
	Three Months Ended March 31, 2014
	(U.S. dollars in thousands)
	Interest rate exposure	$	—
	Foreign exchange exposure	(6,531		)
	Total	$	(6,531	)		$	8,325		$	1,794
	The gains (losses) recorded on both the derivative instruments and specific items designated as being hedged as part of the fair value hedging relationships outlined above along with any associated ineffectiveness in the relationships are recorded through Net realized and unrealized gains (losses) on derivative instruments in the income statement.
	Settlement of Fair Value Hedges
	A summary of the fair value hedges that have been settled and their impact on results during the indicated periods as well as the remaining balance of fair value hedges and average years remaining to maturity as of March 31, 2015 and 2014 are shown below:
	Settlement of Fair Value Hedges - Summary	Fair Value Hedges -
		Deposit Liabilities
		March 31,
	(U.S. dollars in thousands, except years)	2015				2014
	Cumulative reduction to interest expense	$	97,705			$	41,270
	Remaining balance	$	135,490			$	191,925
Weighted average years remaining to maturity	22.7				22.2
During the second quarter of 2014, the Company negotiated the termination of one of its larger structured indemnity contracts. This contract had previously been designated as a fair value hedge that was settled. The remaining fair value adjustment of $47.0 million that was being amortized as a reduction of interest expense over the remaining term of the contract was recorded as an adjustment to interest expense at the termination date. As a result of the termination, a net decrease of $28.7 million was recorded to interest expense reflecting the realization of the remaining balance of the fair value hedge adjustment, partially offset by an accretion rate adjustment due to changes in cash flows.
(b) Derivative Instruments Designated as Hedges of the Net Investment in a Foreign Operation
The Company utilizes foreign exchange contracts to hedge the fair value of certain net investments in foreign operations. During the three months ended March 31, 2015 and 2014, the Company entered into foreign exchange contracts that were formally designated as hedges of investments in foreign subsidiaries, the majority of which have functional currencies of either U.K. sterling or the Euro. There was no ineffectiveness in these transactions.
The following table provides the weighted average U.S. dollar equivalent of foreign denominated net assets that were hedged and the resulting derivative gain (loss) that was recorded in the Foreign currency translation adjustment, net of tax, account within AOCI for the three months ended March 31, 2015 and 2014:
Derivative Instruments Designated as Hedges of the	Three months ended March 31,
Net Investment in a Foreign Operation - Summary
(U.S. dollars in thousands)	2015				2014
Weighted average of U.S. dollar equivalent of foreign denominated net assets	$	628,941			$	2,687,455
Derivative gains (losses) (1)	$	66,770			$	960
____________
-1	Derivative gains (losses) from derivative instruments designated as hedges of the net investment in a foreign operation are recorded in the cumulative translation adjustment account within AOCI for each period.
(c) Derivative Instruments Not Formally Designated As Hedging Instruments
The following table provides the total impact on earnings relating to derivative instruments not formally designated as hedging instruments under authoritative accounting guidance and from the ineffective portion of fair value hedges. The impacts are all recorded through Net realized and unrealized gains (losses) on derivatives in the income statement for the three months ended March 31, 2015 and 2014:
Net Realized and Unrealized Gains (Losses) on Derivative Instruments	Three months ended March 31,
(U.S. dollars in thousands)	2015				2014
Investment Related Derivatives:
Interest rate exposure	$	9,637			$	348
Foreign exchange exposure	(1,362		)		3,288
Credit exposure	82				(404		)
Financial market exposure	3,041				871
Financial Operations Derivatives:
Credit exposure	—				(4,800		)
Other Non-Investment Derivatives:
Foreign exchange contracts	2,059				—
Credit exposure	1,346				—
Guaranteed minimum income benefit contract	—				1,624
Modified coinsurance funds withheld contract	1,718				(911		)
Total gain (loss) recognized in income from derivatives not designated as hedging instruments	$	16,521			$	16
Amount of gain (loss) recognized in income from ineffective	—				1,794
portion of fair value hedges
Net realized and unrealized gains (losses) on derivative instruments	$	16,521			$	1,810
Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets	$	(229,367	)		$	—
The Company’s objectives in using these derivatives are explained below.
(d)(i) Investment Related Derivatives
The Company, either directly or through its investment managers, may use derivative instruments within its investment portfolio, including interest rate swaps, inflation swaps, commodity contracts, credit derivatives (single name and index credit default swaps), options, forward contracts and financial futures (foreign exchange, bond and stock index futures), primarily as a means of economically hedging exposures to interest rate, credit spread, equity price changes and foreign currency risk or, in limited instances, for investment purposes. When using cleared (exchange traded) derivatives, the Company is exposed to the credit risk of the applicable clearing house and of the Company's future commissions merchant. When using uncleared (over-the-counter) derivatives, the Company is exposed to credit risk in the event of non-performance by the counterparties under any derivative contracts, although the Company generally seeks to use credit support arrangements with counterparties to help manage this risk.
Investment Related Derivatives – Interest Rate Exposure
The Company utilizes risk management and overlay strategies that incorporate the use of derivative financial instruments, primarily to manage its fixed income portfolio duration and net economic exposure to interest rate risks. The Company may also use interest rate swaps to convert certain liabilities from a fixed rate to a variable rate of interest or use them to convert a variable rate of interest from one basis to another.
Investment Related Derivatives – Foreign Exchange Exposure
The Company has exposure to foreign currency exchange rate fluctuations through its operations and in its investment portfolio. The Company uses foreign exchange contracts to manage its exposure to the effects of fluctuating foreign currencies on the value of certain of its foreign currency fixed maturities. These contracts are not designated as specific hedges for financial reporting purposes and, therefore, realized and unrealized gains and losses on these contracts are recorded in income in the period in which they occur. These contracts generally have maturities of twelve months or less.
In addition, certain of the Company's investment managers may, subject to investment guidelines, enter into forward contracts.
Investment Related Derivatives – Credit Exposure
Credit derivatives may be purchased within the Company's investment portfolio in the form of single name, basket or index credit default swaps, which are used to mitigate credit exposure through a reduction in credit spread duration (i.e., macro credit strategies rather than single-name credit hedging) or exposure to securities of selected issuers, including issuers that are not held in the underlying fixed income portfolio.
Investment Related Derivatives – Financial Market Exposure
Stock index futures may be purchased within the Company's investment portfolio in order to create synthetic equity exposure and to add value to the portfolio with overlay strategies where market inefficiencies are believed to exist. From time to time, the Company may enter into other financial market exposure derivative contracts on various indices including, but not limited to, inflation and commodity contracts.
(d)(ii) Financial Operations Derivatives – Credit Exposure
During the fourth quarter of 2014, the remaining financial operations credit derivative exposure, which was written as part of the Company's previous financial lines business and is outside of the Company's investment portfolio, was terminated. The Company has no continuing financial operations derivative credit exposures.
(d)(iii) Other Non-Investment Derivatives
Foreign Exchange Contracts
On January 9, 2015, the Company entered into deal contingent deliverable foreign exchange forwards ("FX Forwards") with Morgan Stanley Capital Services LLC and Goldman Sachs International. The purpose of the FX Forwards was to mitigate risk of foreign currency exposure related to the Acquisition. Following the close of the Acquisition, the FX Forwards were settled.
In connection with the Acquisition and the FX Forward, during the quarter, certain foreign exchange contracts utilized to hedge the fair value of certain net investments in foreign operations were de-designated as hedging instruments.
Credit Exposure
During the year ended December 31, 2014, the Company entered into a non-investment related credit derivative relating to a number of reference pool mortgage tranches associated with actual mortgage loans that were securitized into agency mortgage-backed securities and sold as Structured Agency Credit Risk Notes. As of March 31, 2015, there was no reported event of default on this obligation. As of March 31, 2015 and December 31, 2014, the notional amount outstanding related to the derivative was $31.1 million and the Company had recorded a derivative asset of $0.2 million and $0.1 million, respectively. During the three months ended March 31, 2015, the Company recorded Net realized and unrealized gains of $0.1 million relating to this credit derivative. The credit derivative is recorded at fair value based upon models developed by the Company. Significant unobservable inputs considered in the valuation include the impact of changes in interest rates, future default, delinquency and prepayment rates, credit spreads, changes in credit quality, and other market factors.
Guaranteed Minimum Income Benefit Contract
The Company also has derivatives embedded in certain reinsurance contracts. For a certain life reinsurance contract, the Company pays the ceding company a fixed amount equal to the estimated present value of the excess of the guaranteed benefit over the account balance upon the policyholder's election to take the income benefit. The fair value of this derivative is determined based on the present value of expected cash flows.
Modified Coinsurance Funds Withheld Contract
The Company has modified coinsurance and funds withheld reinsurance agreements that provide for a return to be paid to the Company based on a portfolio of fixed income securities. As such, the agreements contain an embedded derivative. The embedded derivative is bifurcated from the funds withheld balance and recorded at fair value with changes in fair value recognized in earnings through Net realized and unrealized gains (losses) on derivative instruments.
Modified Coinsurance Funds Withheld Reinsurance Agreements - Life Retrocession Embedded Derivative
In addition, the Company has entered into Life Retro Arrangements, as described in Note 3(c), "Acquisition and Disposals - Sale of Life Reinsurance Subsidiary." The embedded derivative related to the Life Retro Arrangements is recorded at fair value with changes in fair value recognized in earnings through Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets.
The value of the life retrocession embedded derivative includes the interest income, realized and unrealized gains and losses on Life Funds Withheld Assets and certain related expenses subsequent to May 30, 2014 as follows:
Components of Life Retrocession Embedded Derivative and Derivative Instruments - Life Funds Withheld Assets:	Three months ended March 31,
(U.S. dollars in thousands)	2015				2014
Interest income - Life Funds Withheld Assets	$	(50,996	)		—
Realized and unrealized gains (losses) - Life Funds Withheld Assets	(152,830		)		—
Other	96				—
Net realized and unrealized gains (losses) on life retrocession embedded derivative	$	(203,730	)		$	—
Net adjustments related to future policy benefit reserves, net of tax	$	(11,954	)		$	—
Net realized and unrealized gains (losses) on derivative instruments - Life Funds Withheld Assets	$	(13,683	)		$	—
Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets	$	(229,367	)		$	—
(e) Contingent Credit Features
Certain derivative agreements entered into by the Company or its subsidiaries contain credit rating downgrade provisions that permit early termination of the agreements by the counterparty if collateral is not posted following failure to maintain certain credit ratings from one or more of the principal credit rating agencies. If the Company were required to early terminate such agreements due to a credit rating downgrade, it could potentially be in a net liability position at the time of settlement of such agreements. The aggregate fair value of all derivative agreements containing such rating downgrade provisions that were in a liability position and any collateral posted under these agreements as of March 31, 2015 and December 31, 2014 were as follows:
Contingent Credit Features - Summary:	31-Mar-15				31-Dec-14
(U.S. dollars in thousands)
Aggregate fair value of derivative agreements with downgrade provisions in a net liability position	$	5,598			$	5,770
Collateral posted to counterparty	$	—			$	—

Goodwill_and_Other_Intangible_

Goodwill and Other Intangible Assets	3 Months Ended
	Mar. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and other Intangible Assets	Goodwill and Other Intangible Assets
	During the first quarter of 2014, goodwill and intangible assets increased as a result of the completion of an acquisition. The transaction was accounted for using the acquisition method under which the Company recorded the identifiable assets and liabilities at their acquisition date fair values, and recorded the excess of consideration transferred over the net assets acquired as goodwill and intangible assets. The fair value of identifiable assets and liabilities acquired, as well as amounts recorded in the Company’s consolidated results since the acquisition date, are not material. The Company has goodwill and intangible assets of $442.4 million and $448.0 million at March 31, 2015 and December 31, 2014, respectively, predominantly related to the Reinsurance segment. The movement of this balance during the year to date is a result of the amortization of intangible assets with definite lives, and the impact of foreign currency translation.

Share_Capital

Share Capital	3 Months Ended
	Mar. 31, 2015
Stockholders' Equity Note [Abstract]
Share Capital	Share Capital
	(a) Authorized and Issued
	Buybacks of Ordinary Shares
	On February 21, 2014, XL-Ireland announced that its Board of Directors approved an increase to the Share Buyback Program, authorizing the purchase of up to $1.0 billion of our ordinary shares, which included the amounts that remained under the previous Share Buyback Program. The Company suspended active share buybacks during the quarter ended March 31, 2015 through the close of the Acquisition; however, with the close of the Acquisition, the Company continues to see share buybacks as a valuable capital management tool. As of March 31, 2015, $267.6 million remained available for purchase under the Share Buyback Program.
	(b) Stock Plans
	The Company's performance incentive programs provide for grants of stock options, restricted stock, restricted stock units, performance units and stock appreciation rights. Share-based compensation granted by the Company generally contains a vesting period of three or four years, and certain awards also contain performance conditions. The Company records compensation expense related to each award over its vesting period, incorporating the best estimate of the expected outcome of performance conditions where applicable. Compensation expense is generally recorded on a straight line basis over the vesting period of an award. See Item 8, Note 20, “Share Capital,” to the Consolidated Financial Statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2014 for further information on the Company's performance incentive programs and associated accounting.
	During the three months ended March 31, 2015, the Company granted approximately 1.3 million stock options with a weighted-average grant date fair value of $6.57 per option. The fair value of the options issued was estimated on the date of grant using the Black-Scholes option pricing model using the following weighted average assumptions:
	Dividend yield	2	%
	Risk free interest rate	1.7	%
	Volatility	21.9	%
	Expected lives	6.0 years
	During the three months ended March 31, 2015, the Company granted approximately 1.5 million restricted stock units to certain employees of the Company and its subsidiaries with an aggregate grant date fair value of approximately $55.1 million. Each restricted stock unit represents the Company's obligation to deliver to the holder one ordinary share, and grants vest in three equal installments upon the first, second and third anniversaries of the date of grant. Restricted stock units are granted at the closing market price on the day of grant and entitle the holder to receive dividends declared and paid in the form of additional ordinary shares contingent upon vesting.

Notes_Payable_and_Debt_and_Fin

Notes Payable and Debt and Financing Arrangements	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Notes Payable and Debt and Financing Arrangements	Notes Payable and Debt and Financing Arrangements
	(a) Notes Payable and Debt
	All outstanding debt of the Company as of March 31, 2015 and December 31, 2014 was issued by XL-Cayman, a 100% owned subsidiary of XL-Ireland. XL-Ireland does not have significant assets or operations independent of XL-Cayman. XL-Cayman's outstanding debt is fully and unconditionally guaranteed by XL-Ireland. The ability of XL-Cayman, like that of the Company, to obtain funds from its subsidiaries to satisfy any of its obligations under guarantees is subject to certain contractual restrictions, applicable laws and statutory requirements of the various countries in which the subsidiaries operate, including, among others, Bermuda, the United States, Ireland, Switzerland and the United Kingdom. For details of the required statutory capital and surplus for the principal operating subsidiaries of the Company, see Item 8, Note 25, “Statutory Financial Data,” to the Consolidated Financial Statements included in the Company's Annual Report on Form 10-K for the year ended December 31, 2014.
	On March 30, 2015, XL-Cayman issued $500 million of subordinated notes due March 2025, with a fixed coupon of 4.45%, that are guaranteed by XL-Ireland. The notes are listed on the New York Stock Exchange. The notes were issued at 99.633% of the face amount and net proceeds were $492.2 million. Related expenses of the offering amounted to approximately $5.9 million. These costs were deferred and will be amortized over the term of the subordinated notes.
	On March 30, 2015, XL-Cayman issued $500 million of subordinated notes due March 2045, with a fixed coupon of 5.5%, that are guaranteed by XL-Ireland. The notes are listed on the New York Stock Exchange. The notes were issued at 99.115% of the face amount and net proceeds were $488.4 million. Related expenses of the offering amounted to approximately $7.2 million. These costs were deferred and will be amortized over the term of the subordinated notes.
	XL-Cayman and the Company were in compliance with all covenants by significant margins as of March 31, 2015, and XL-Cayman and the Company currently remain in compliance with all covenants.
	(b) Letter of Credit Facilities and Other Sources of Collateral
	The Company has several letter of credit facilities provided on both syndicated and bilateral bases from commercial banks. These facilities are utilized primarily to support non-admitted insurance and reinsurance operations in the U.S. and capital requirements at Lloyd’s. The Company’s letter of credit facilities and revolving credit facilities at March 31, 2015 and December 31, 2014 were as follows:
	Letter of Credit Summary:	March 31, 2015 (1)			December 31, 2014 (1)
	(U.S. dollars in thousands except percentages)
	Revolving credit facility (2)	$	1,000,000		$	1,000,000
	Available letter of credit facilities - commitments (3)	$	3,575,000		$	3,575,000
	Available letter of credit facilities - in use	$	1,743,230		$	1,790,561
	Collateralized by certain assets of the Company’s investment portfolio	65.7		%	66.2		%
	____________
	-1	As of March 31, 2015 and December 31, 2014, there were eight available letter of credit facilities.
	-2	As of March 31, 2015 and December 31, 2014, the $1 billion of revolving credit available under the November 2013 unsecured credit agreements, which currently provide an aggregate amount for issuance of letters of credit and revolving credit loans up to $2 billion, was unutilized. The credit agreements entered into with Citicorp USA, Inc. in May through November 2013 (the "Citi Agreements") provide for issuance of letters of credit and revolving credit loans up to an aggregate amount of $575.0 million. As of March 31, 2015, $575.0 million of letters of credit were issued under these agreements and therefore such amount is not included in this line.
	-3	The available letter of credit facilities include $1 billion that is also included in the "revolving credit facility" line in this table, as part of the November 2013 credit agreements, which currently provide an aggregate amount of outstanding letters of credit and revolving credit loans of up to $2 billion. The Company has the option to increase the size of the facilities under these agreements by an additional $500 million across such facilities. The Company also has the option to increase the maximum amount of the letters of credit and revolving credit loans available under the 2013 credit agreements with Citicorp USA, Inc. with the lender's and issuing lender's consent.
	For details regarding these facilities see Item 8, Note 15(b), “Notes Payable and Debt and Financing Arrangements - Letter of Credit Facilities and Other Sources of Collateral,” to the Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2014.

Related_Party_Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2015
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions
	At each of March 31, 2015 and 2014, the Company owned minority stakes in six and five independent investment management companies (“Investment Manager Affiliates”) that are actively managing client capital and seeking growth opportunities, respectively. The Company seeks to develop relationships with specialty investment management organizations, generally acquiring an equity interest in the business. The Company also invests in certain of the funds and limited partnerships and other legal entities managed by these affiliates, and, through these funds and partnerships, pays management and performance fees to the Company's Investment Manager Affiliates. See Item 8, Note 7, “Investments in Affiliates,” to the Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2014.
	In the normal course of business, the Company enters into assumed reinsurance contracts with certain of its other strategic affiliates, or their subsidiaries. Management believes that these transactions are conducted at market rates consistent with negotiated arm's-length contracts. During the three months ended March 31, 2015 and 2014, these contracts resulted in reported net premiums written, net reported claims and reported acquisition costs as summarized below.
	(U.S. dollars in thousands)	Three months ended March 31,
		2015		2014
	Reported net premiums written	$	27,076	$	16,240
	Net losses and loss expenses incurred	$	9,100	$	6,138
	Reported acquisition costs	$	9,012	$	7,629
	Commencing in 2014, several of the Company’s wholly-owned subsidiaries retrocede assumed reinsurance business to special purpose reinsurers that receive capital from funds managed by the Company's subsidiary, New Ocean Capital Management Limited, a Bermuda based company, (“New Ocean”), as discussed in Note 12, “Variable Interest Entities”. Underwriting administration services are provided to the special purpose reinsurers by other subsidiaries of the Company under service fee agreements negotiated at arm's-length, while investment advisory services are provided by New Ocean.
	During the three months ended March 31, 2015, ceded premiums earned, ceded losses and loss expenses incurred, ceding commission income, and other fee income related to these retrocessional contracts were not material to the Company. Management believes that these transactions are conducted at market rates consistent with negotiated arm's-length contracts.

Variable_Interest_Entities

Variable Interest Entities	3 Months Ended
	Mar. 31, 2015
Variable Interest Entities Disclosure [Abstract]
Variable Interest Entities	Variable Interest Entities
	At times, the Company has utilized variable interest entities (“VIEs”) both indirectly and directly in the ordinary course of the Company's business.
	The Company invests in CDOs and other investment vehicles that are issued through VIEs as part of the Company's investment portfolio. The activities of these VIEs are generally limited to holding the underlying collateral used to service investments therein. The Company's involvement in these entities is passive in nature and we are not the arranger of these entities. In addition, the Company has not been involved in establishing these entities and is not the primary beneficiary of these VIEs as contemplated in current authoritative accounting guidance.
	The Company has a limited number of remaining outstanding credit enhancement exposures, including written financial guarantee and credit default swap contracts. The obligations related to these transactions are often securitized through VIEs. The Company is not the primary beneficiary of these VIEs as contemplated in current authoritative accounting guidance on the basis that management does not believe that the Company has the power to direct the activities, such as asset selection and collateral management, which most significantly impact each entity's economic performance. For further details on the nature of the obligations and the size of the Company's maximum exposure, see Note 7, “Derivative Instruments,” and Note 14(a), “Commitments and Contingencies - Financial Guarantee Exposures.”
	During the third quarter of 2013, the Company, along with other investors, formed New Ocean to act as an investment manager focused on providing third-party investors access to insurance-linked securities and other insurance and reinsurance capital markets products. The Company holds a majority voting interest in New Ocean through its ownership of common shares and, accordingly, the financial statements of New Ocean have been included in the consolidated financial statements of the Company. None of the assets, liabilities, revenues or net income of New Ocean was material to the Company during the three months ended March 31, 2015. The equity interest attributable to third party investors in New Ocean recorded in the Company’s Unaudited Consolidated Balance Sheets as "Non-controlling interest in equity of consolidated subsidiaries" was $0.2 million and $0.2 million as of March 31, 2015 and December 31, 2014, respectively.
	During the fourth quarter of 2013, the Company, along with other investors, invested in a new Bermuda-based company, New Ocean Focus Cat Fund Ltd. ("New Ocean FCFL"), which is considered a VIE under GAAP. During the second quarter of 2014, the Company formed another new Bermuda-based investment company, New Ocean Market Value Cat Fund, Ltd. ("New Ocean MVCFL"), which is also considered a VIE under GAAP. New Ocean MVCFL primarily invests in insurance-linked securities, with a current focus on catastrophe bonds.
	During the year ended December 31, 2014, New Ocean FCFL invested in a special purpose Bermuda reinsurer, Vector Reinsurance Ltd (“Vector Re”), formed for the purpose of underwriting collateralized excess of loss reinsurance with a focus on global property catastrophe risks. During the first quarter of 2015, New Ocean MVCFL also invested in Vector Re. Most of Vector Re’s current underwriting activity relates to reinsurance business assumed from the Company's subsidiaries. Underwriting administration and claims services are provided to Vector Re by the Company under service fee contracts which management believes were negotiated at arm's-length, while investment advisory services are provided by New Ocean.
	The Company currently holds majority equity interests, which are considered to be the controlling financial interests, in New Ocean FCFL and New Ocean MVCFL, and by extension, Vector Re. Accordingly, included in the consolidated financial statements of the Company are the total net assets of New Ocean FCFL, New Ocean MVCFL and Vector Re of $141.3 million and $139.9 million as of March 31, 2015 and December 31, 2014, respectively. The Company’s share of revenue and net income in these VIEs was not material to the Company for three months ended March 31, 2015. All inter-company transactions between the Company's entities have been eliminated in consolidation. The equity interest attributable to third party investors in New Ocean FCFL, New Ocean MVCFL and Vector Re recorded in the Company’s Consolidated Balance Sheets as "Non-controlling interest in equity of consolidated subsidiaries" was $58.8 million and $58.4 million as of March 31, 2015 and December 31, 2014, respectively.

Computation_of_Earnings_Per_Or

Computation of Earnings Per Ordinary Share and Ordinary Share Equivalent	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Computation of Earnings Per Ordinary Share and Ordinary Share Equivalent	Computation of Earnings Per Ordinary Share and Ordinary Share Equivalent
	The following table sets forth the computation of basic and diluted earnings per ordinary share for the three months ended March 31, 2015 and 2014:
		Three Months Ended March 31,
	(U.S. dollars in thousands, except per share amounts)	2015		2014
	Basic earnings per ordinary share & ordinary share equivalents outstanding:
	Net income (loss) attributable to ordinary shareholders	$	36,281	$	255,717
	Weighted average ordinary shares outstanding, in thousands - basic	255,724		276,337
	Basic earnings per ordinary share & ordinary share equivalents outstanding	$	0.14	$	0.93
	Diluted earnings per ordinary share & ordinary share equivalents outstanding:
	Weighted average ordinary shares outstanding, in thousands - basic	255,724		276,337
	Impact of share-based compensation and certain conversion features, in thousands	4,980		4,121
	Weighted average ordinary shares outstanding, in thousands - diluted	260,704		280,458
	Diluted earnings per ordinary share & ordinary share equivalents outstanding	$	0.14	$	0.91
	Dividends per ordinary share	$	0.16	$	0.16
	For the three months ended March 31, 2015 and 2014, ordinary shares available for issuance under share-based compensation plans of 5.0 million and 6.1 million, respectively, were not included in the calculation of diluted earnings per ordinary share because the assumed exercise or issuance of such shares would be anti-dilutive.

Commitments_and_Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies
	(a) Financial Guarantee Exposures
	The Company's outstanding financial guarantee contracts as of March 31, 2015 provide credit support for a variety of collateral types with the exposures comprised of an aggregate amount of $80.8 million notional financial guarantee on two notes backed by zero coupon long dated bonds and bank perpetual securities, including some issued by European financial institutions. As of March 31, 2015 and December 31, 2014, the total gross claim liability recorded was nil and the contracts had a weighted average contractual term to maturity of 25.0 years and 25.2 years, respectively.
	Surveillance procedures to track and monitor credit deteriorations in the insured financial obligations are performed by the primary obligors for each transaction on the Company's behalf. Information regarding the performance status and updated exposure values is provided to the Company on a quarterly basis and evaluated by management in recording claims reserves. As of March 31, 2015, there were no reported events of default on these obligations.
	(b) Litigation
	The Company and its subsidiaries are subject to litigation and arbitration in the normal course of business. These lawsuits and arbitrations principally involve claims on policies of insurance and contracts of reinsurance and are typical for the Company and for the property and casualty insurance and reinsurance industry in general. Such claims proceedings are considered in connection with the Company's loss and loss expense reserves. Reserves in varying amounts may or may not be established in respect of particular claims proceedings based on many factors, including the legal merits thereof. In addition to litigation relating to insurance and reinsurance claims, the Company and its subsidiaries are subject to lawsuits and regulatory actions in the normal course of business that do not arise from or directly relate to claims on insurance or reinsurance policies. This category of business litigation typically involves, among other things, allegations of underwriting errors or misconduct, employment claims, regulatory activity, shareholder disputes or disputes arising from business ventures. The status of these legal actions is actively monitored by management.
	Legal actions are subject to inherent uncertainties, and future events could change management's assessment of the probability or estimated amount of potential losses from pending or threatened legal actions. Based on available information, it is the opinion of management that the ultimate resolution of pending or threatened legal actions other than claims proceedings, both individually and in the aggregate, will not result in losses having a material adverse effect on the Company's financial position or liquidity as of March 31, 2015.
	If management believes that, based on available information, it is at least reasonably possible that a material loss (or additional material loss in excess of any accrual) will be incurred in connection with any legal actions, the Company discloses an estimate of the possible loss or range of loss, either individually or in the aggregate, as appropriate, if such an estimate can be made, or discloses that an estimate cannot be made. Based on the Company's assessment as of March 31, 2015, no such disclosures were considered necessary.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2015
Comprehensive Income Loss Note [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss)
	The changes in AOCI, net of tax, by component for the three months ended March 31, 2015 and 2014 are as follows:
	Three months ended March 31, 2015	Unrealized Gains (Losses) on Investments (1)			OTTI Losses Recognized in AOCI			Foreign Currency Translation Adjustments			Underfunded Pension Liability			Cash Flow Hedge		Total
	(U.S. dollars in thousands)
	Balance, beginning of period, net of tax	$	1,590,114		$	(76,047	)	$	(11,188	)	$	(20,789	)	$	2,368	$	1,484,458
	OCI before reclassifications	254,267			—			32,404			975			—		287,646
	Amounts reclassified from AOCI	(74,781		)	9,936			—			—			95		(64,750		)
	Tax benefit (expense)	(5,805		)	(78		)	3,699			—			—		(2,184		)
	Net current period OCI - net of tax	173,681			9,858			36,103			975			95		220,712
	Balance, end of period, net of tax	$	1,763,795		$	(66,189	)	$	24,915		$	(19,814	)	$	2,463	$	1,705,170
	Three months ended March 31, 2014
	(U.S. dollars in thousands)
	Balance, beginning of period, net of tax	$	822,432		$	(89,190	)	$	14,541		$	(13,239	)	$	2,113	$	736,657
	OCI before reclassifications	265,250			—			(5,900		)	(31		)	—		259,319
	Amounts reclassified from AOCI	(22,638		)	3,409			—			—			110		(19,119		)
	Tax benefit (expense)	(32,103		)	(113		)	2,020			—			—		(30,196		)
	Net current period OCI - net of tax	210,509			3,296			(3,880		)	(31		)	110		210,004
	Balance, end of period, net of tax	$	1,032,941		$	(85,894	)	$	10,661		$	(13,270	)	$	2,223	$	946,661
	____________
	-1	Included in these amounts is the impact of Shadow Adjustments. As of December 31, 2014 the cumulative impact of these adjustments was $445.1 million. During the three months ended March 31, 2015, net movements of $(60.4) million were recorded, resulting in a total cumulative net impact of Shadow Adjustments on future policy benefit reserves of $384.8 million as of March 31, 2015.
	The reclassifications out of AOCI along with the associated income statement line items affected by component, and the total related tax (expense) benefit for the three months ended March 31, 2015 and 2014 are as follows:
	Gross Amount Reclassified From AOCI
	Details About AOCI Components	Three months ended March 31, 2015			Three months ended March 31, 2014			Affected Line Item in the Statement of Income
	(U.S. dollars in thousands)
	Unrealized gains and losses on investments:
		$	(78,551	)	$	(24,914	)	Net realized gains (losses) on investments sold
		15,724			2,276			OTTI on investments
		$	(11,954	)	$	—		Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets
		$	(74,781	)	$	(22,638	)	Total before tax
		87			453			Provision (benefit) for income tax
		$	(74,694	)	$	(22,185	)	Net of tax
	OTTI losses recognized in OCI:
		$	9,875		$	1,958		Net realized gains (losses) on investments sold
		61			1,451			OTTI on investments transferred to (from) OCI
		$	9,936		$	3,409		Total before tax
		(3		)	(113		)	Provision (benefit) for income tax
		$	9,933		$	3,296		Net of tax
	Gains and losses on cash flow hedges:
	Interest rate contracts	$	95		$	110		Interest Expense
		—			—			Provision (benefit) for income tax
		$	95		$	110		Net of tax
	Total reclassifications for the period, gross of tax	$	(64,750	)	$	(19,119	)
	Tax benefit (expense)	84			340
	Total reclassifications for the period, net of tax	$	(64,666	)	$	(18,779	)

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Recent accounting pronouncements	Recent Accounting Pronouncements
	In February 2015, the Financial Accounting Standards Board ("FASB") issued an accounting standards update concerning consolidation of certain legal entities. Under this new guidance, all legal entities are required to evaluate whether they should consolidate certain legal entities. The guidance: (1) modifies the evaluation of whether limited partnerships and similar legal entities are variable interest entities ("VIEs") or voting interest entities; (2) eliminates the presumption that a general partner should consolidate a limited partnership; (3) affects the consolidation analysis of reporting entities that are involved with VIEs, particularly those that have fee arrangements and related party relationships; and (4) provides a scope exception from consolidation guidance for certain reporting entities. Upon adoption of the new guidance, differing requirements for performing a consolidation analysis under existing GAAP will be eliminated, and all reporting entities will now fall within the scope of the Accounting Standards Codification Subtopic 810-10, Consolidation-Overall, unless a specific exception applies. Under this Subtopic, there are only two primary models for determining whether consolidation is appropriate - a voting interest entity model, and a variable interest entity model. The guidance is effective for public business entities for annual periods ending after December 15, 2015, and interim and annual periods thereafter, with early adoption permitted. The Company is currently evaluating the impact of this guidance.
	In April 2015, the FASB issued an accounting standards update concerning the presentation of deferred debt issuance costs in an entity's balance sheet. Under this new guidance, which is part of the FASB's initiative to reduce complexity in accounting standards while maintaining or improving the usefulness of the information provided to users of financial statements, it is required that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. In addition, the guidance also requires that the amortization of such costs be reported as interest expense. The guidance is effective for public business entities for annual periods beginning after December 31, 2015, and interim periods within those fiscal years, with early adoption permitted for financial statements that have not been previously issued. This guidance is not expected to have a material impact on the Company's financial condition, results of operations or cash flows.

Acquisition_and_Disposals_Tabl

Acquisition and Disposals (Tables)	3 Months Ended
	Mar. 31, 2015
Acquisition and Disposal [Abstract]
Calculation of consideration transferred	The calculation of the consideration transferred to acquire Catlin Shares is as follows:
	(In thousands, except per share data)
	Catlin Shares outstanding as of April 30, 2015 that will receive share consideration (including the dilutive effect of warrants)	384,118
	Exchange ratio per the merger agreement	0.13
	Share issuance to Catlin shareholders	49,935
	Closing price per share on April 30, 2015 (1)	$	37.08
	Share issuance consideration	$	1,851,601
	Shares of Catlin common stock outstanding as of April 30, 2015 that will receive cash consideration (including the dilutive effect of warrants)	384,118
	Cash price component, per share in GBP	£	3.88
	Cash consideration, in GBP	£	1,490,377
	Foreign exchange rate: GBP/USD on April 30, 2015	$	1.5349
	Cash consideration	$	2,287,579
	Total acquisition consideration	$	4,139,180
	____________
	-1	The closing market price of XL's common stock on the acquisition date represents the fair value of shares issued as part of the consideration transferred.
Impact of Life Retro Arrangements	The impact of the Life Retro Arrangements on the Company's results was as follows:
	Impact of Life Retro Arrangements	Three months ended March 31,
	(U.S. dollars in thousands)	2015
	Underwriting profit (loss) (1)	$	603
	Net investment income - Life Funds Withheld Assets	50,419
	Net realized gains (losses) on investments sold - Life Funds Withheld Assets	52,738
	Net unrealized gains (losses) on investments, Trading - Life Funds Withheld Assets	760
	OTTI on investments - Life Funds Withheld Assets	(5,209		)
	Exchange (gains) losses	3,684
	Other income and expenses	(1,298		)
	Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets	(229,367		)
	Net income (loss)	$	(127,670	)
	Change in net unrealized gains (losses) on investments - Life Funds Withheld Assets, net of tax	37,115
	Change in adjustments related to future policy benefit reserves, net of tax	60,356
	Change in cumulative translation adjustment - Life Funds Withheld Assets, net of tax	30,802
	Total changes to other comprehensive income as a result of Life Retro Arrangements	$	128,273
	Comprehensive income (loss)	$	603
	____________
	-1	The underwriting profit of $0.6 million relates to a premium adjustment during the three months ended March 31, 2015 relating to the Life Retro Arrangements transaction which was completed on May 30, 2014. Excluding this transaction, the impact to comprehensive income relating to the Life Retro Arrangements was nil for the three months ended March 31, 2015.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Hierarchy	The following tables set forth the Company’s assets and liabilities that were accounted for at fair value as of March 31, 2015 and December 31, 2014 by level within the fair value hierarchy:
	31-Mar-15	Quoted Prices			Significant			Significant			Collateral			Balance at
	(U.S. dollars in thousands)	in Active			Other			Other			and			31-Mar-15
		Markets for			Observable			Unobservable			Counterparty
		Identical Assets			Inputs			Inputs			Netting
		(Level 1)			(Level 2)			(Level 3)
	Assets
	Fixed maturities - Available for Sale ("AFS") - Excluding Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	—		$	3,378,342		$	—		$	—		$	3,378,342
	Corporate (1)	—			8,148,777			5,861			—			8,154,638
	Residential mortgage-backed securities – Agency (“RMBS - Agency”)	—			3,709,514			1,820			—			3,711,334
	Residential mortgage-backed securities – Non-Agency (“RMBS - Non-Agency”)	—			380,135			—			—			380,135
	Commercial mortgage-backed securities (“CMBS”)	—			1,032,720			—			—			1,032,720
	Collateralized debt obligations (“CDO”)	—			4,051			496,923			—			500,974
	Other asset-backed securities	—			1,165,123			2,244			—			1,167,367
	U.S. States and political subdivisions of the States	—			1,973,140			—			—			1,973,140
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	—			4,093,771			—			—			4,093,771
	Total fixed maturities - AFS - Excluding Funds Withheld Assets, at fair value	$	—		$	23,885,573		$	506,848		$	—		$	24,392,421
	Equity securities, at fair value	497,496			285,975			—			—			783,471
	Short-term investments, at fair value (1)(2)	—			168,862			—			—			168,862
	Total investments AFS - Excluding Funds Withheld Assets	$	497,496		$	24,340,410		$	506,848		$	—		$	25,344,754
	Fixed maturities - Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	—		$	17,613		$	—		$	—		$	17,613
	Corporate	—			2,746,226			—			—			2,746,226
	RMBS – Agency	—			2,130			—			—			2,130
	RMBS – Non-Agency	—			38,808			—			—			38,808
	CMBS	—			159,257			—			—			159,257
	Other asset-backed securities	—			244,140			—			—			244,140
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	—			1,509,805			—			—			1,509,805
	Total fixed maturities - AFS - Life Funds Withheld Assets, at fair value	$	—		$	4,717,979		$	—		$	—		$	4,717,979
	Total investments - AFS, at fair value	$	497,496		$	29,058,389		$	506,848		$	—		$	30,062,733
	Fixed maturities - trading securities ("Trading")
	Corporate	—			137,438			—			—			137,438
	Other asset-backed securities	—			1,939			—			—			1,939
	Total fixed maturities - Trading, at fair value	$	—		$	139,377		$	—		$	—		$	139,377
	Cash equivalents (3)	1,835,344			393,154			—			—			2,228,498
	Cash equivalents - Life Funds Withheld Assets (3)	788			120,721			—			—			121,509
	Other investments (4)	—			784,486			190,097			—			974,583
	Other assets (5)	—			244,900			12,980			(587		)	257,293
	Total assets accounted for at fair value	$	2,333,628		$	30,741,027		$	709,925		$	(587	)	$	33,783,993
	Liabilities
	Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable) (6)	$	—		$	654,561		$	—		$	—		$	654,561
	Financial instruments sold, but not yet purchased (7)	1,572			5,660			—			—			7,232
	Other liabilities (5)	—			99,649			22,586			(587		)	121,648
	Total liabilities accounted for at fair value	$	1,572		$	759,870		$	22,586		$	(587	)	$	783,441
	31-Dec-14	Quoted Prices			Significant			Significant			Collateral			Balance at
	(U.S. dollars in thousands)	in Active			Other			Other			and			December 31,
		Markets for			Observable			Unobservable			Counterparty			2014
		Identical Assets			Inputs			Inputs			Netting
		(Level 1)			(Level 2)			(Level 3)
	Assets
	Fixed maturities - AFS - Excluding Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	—		$	2,171,953		$	—		$	—		$	2,171,953
	Corporate (1)	—			8,772,479			5,894			—			$	8,778,373
	Residential mortgage-backed securities – RMBS - Agency	—			3,726,666			1,910			—			$	3,728,576
	Residential mortgage-backed securities – RMBS - Non-Agency	—			427,351			—			—			$	427,351
	CMBS	—			1,052,544			—			—			$	1,052,544
	CDO	—			4,076			687,958			—			$	692,034
	Other asset-backed securities	—			1,060,005			5,288			—			$	1,065,293
	U.S. States and political subdivisions of the States	—			2,021,272			—			—			$	2,021,272
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	—			4,240,073			—			—			$	4,240,073
	Total fixed maturities - AFS - Excluding Funds Withheld Assets, at fair value	$	—		$	23,476,419		$	701,050		$	—		$	24,177,469
	Equity securities, at fair value	502,284			366,008			—			—			868,292
	Short-term investments, at fair value (1)(2)	—			256,727			—			—			256,727
Total investments AFS - Excluding Funds Withheld Assets	$	502,284		$	24,099,154		$	701,050		$	—		$	25,302,488
Fixed maturities - Life Funds Withheld Assets
U.S. Government and Government-Related/Supported	$	—		$	18,724		$	—		$	—		$	18,724
Corporate	—			2,817,980			—			—			$	2,817,980
RMBS – Agency	—			3,782			—			—			$	3,782
RMBS – Non-Agency	—			85,335			—			—			$	85,335
CMBS	—			193,167			—			—			$	193,167
Other asset-backed securities	—			273,541			—			—			$	273,541
Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	—			1,789,036			—			—			$	1,789,036
Total fixed maturities - AFS - Life Funds Withheld Assets, at fair value	$	—		$	5,181,565		$	—		$	—		$	5,181,565
Total investments - AFS, at fair value	$	502,284		$	29,280,719		$	701,050		$	—		$	30,484,053
Fixed maturities - Trading
Corporate	—			1,171			—			—			$	1,171
Total fixed maturities - Trading, at fair value	$	—		$	1,171		$	—		$	—		$	1,171
Cash equivalents (3)	1,103,877			397,955			—			—			$	1,501,832
Cash equivalents - Life Funds Withheld Assets (3)	460			132,738			—			—			$	133,198
Other investments (4)	—			708,974			185,083			—			$	894,057
Other assets (5)	—			122,996			13,663			(696		)	$	135,963
Total assets accounted for at fair value	$	1,606,621		$	30,644,553		$	899,796		$	(696	)	$	33,150,274
Liabilities
Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable) (6)	$	—		$	450,831		$	—		$	—		$	450,831
Financial instruments sold, but not yet purchased (7)	4,737			25,669			—			—			$	30,406
Other liabilities (5)	—			7,757			23,427			(696		)	$	30,488
Total liabilities accounted for at fair value	$	4,737		$	484,257		$	23,427		$	(696	)	$	511,725
____________
-1	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes had a fair value of $74.8 million and $79.9 million and an amortized cost of $63.8 million and $68.4 million as of March 31, 2015 and December 31, 2014, respectively. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.
-2	Short-term investments consist primarily of Corporate securities and U.S. and Non-U.S. Government and Government-Related/Supported securities.
-3	Cash equivalents balances subject to fair value measurement include certificates of deposit and money market funds. Operating cash balances are not subject to recurring fair value measurement guidance.
-4	The Other investments balance excludes certain structured transactions including certain investments in project finance transactions, a payment obligation and liquidity financing provided to a structured credit vehicle as a part of a third party medium term note facility. These investments, which totaled $354.4 million as of March 31, 2015 and $354.4 million at December 31, 2014, are carried at amortized cost. For further information, see Item 8, Note 8, “Other Investments,” to the Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2014.
-5	Other assets and other liabilities include derivative instruments. The derivative balances included in each category are reported on a gross basis by level with a netting adjustment presented separately in the Collateral and Counterparty Netting column. The fair values of the individual derivative contracts are reported gross in their respective levels based on the fair value hierarchy. For further details regarding derivative fair values and associated collateral received or paid see Note 7, “Derivative Instruments,” to the Unaudited Consolidated Financial Statements.
-6	Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable) include balances related to the life retrocession embedded derivative, under which all investment results associated with the Life Funds Withheld Assets related to the Life Retro Arrangements described in Note 3(c), ”Acquisition and Disposals - Sale of Life Reinsurance Subsidiary," accrue to the benefit of GCLR.
-7	Financial instruments sold, but not yet purchased, represent “short sales” and are included within “Payable for investments purchased” on the balance sheets.
Level 3 Roll Forward
		Level 3 Assets and Liabilities -Three Months Ended March 31, 2015
	(U.S. dollars in thousands)	Corporate			RMBS - Agency			RMBS - Non			CMBS			CDO
								Agency
	Balance, beginning of period	$	5,894		$	1,910		$	—		$	—		$	687,958
	Realized gains (losses)	(1		)	—			—			—			36
	Movement in unrealized gains (losses)	48			(1		)	—			—			5,555
	Purchases and issuances	—			—			—			—			—
	Sales	—			—			—			—			(155,085		)
	Settlements	(80		)	(89		)	—			—			(41,541		)
	Transfers into Level 3				—			—			—			—
	Transfers out of Level 3	—			—			—			—			—
	Fixed maturities to short-term investments classification change	—			—			—			—			—
	Balance, end of period	$	5,861		$	1,820		$	—		$	—		$	496,923
	Movement in total gains (losses) above relating to instruments still held at the reporting date	$	48		$	(1	)	$	—		$	—		$	2,668
		Level 3 Assets and Liabilities -Three Months Ended March 31, 2015
	(U.S. dollars in thousands)	Other asset-			Non-US Sovereign			Short-term			Other investments			Derivative Contracts
		backed			Government,			investments						- Net
		securities			Provincial,
					Supranational and
					Government
					Related/Supported
	Balance, beginning of period	$	5,288		$	—		$	—		$	185,083		$	(9,764	)
	Realized gains (losses)	(1		)	—			—			1,302			—
	Movement in unrealized gains (losses)	2			—			—			(1,827		)	158
	Purchases and issuances	—			—			—			6,793			—
	Sales	—			—			—			—
	Settlements	(3,045		)	—			—			(1,254		)	—
	Transfers into Level 3	—			—			—			—			—
	Transfers out of Level 3	—			—			—			—			—
	Fixed maturities to short-term investments classification change	—			—			—			—			—
	Balance, end of period	$	2,244		$	—		$	—		$	190,097		$	(9,606	)
	Movement in total gains (losses) above relating to instruments still held at the reporting date	$	—		$	—		$	—		$	(524	)	$	158
		Level 3 Assets and Liabilities -Three Months Ended March 31, 2014
	(U.S. dollars in thousands)	Corporate			RMBS - Agency			RMBS - Non			CMBS			CDO
								Agency
	Balance, beginning of period	$	31,573		$	10,473		$	9		$	12,533		$	710,253
	Realized gains (losses)	120			(1		)	—			2			1,581
	Movement in unrealized gains (losses)	(2		)	1			2			(3		)	3,681
	Purchases and issuances	1,434			—			—			—			27,814
	Sales	—			—			—			—			(9,931		)
	Settlements	(5,114		)	(573		)	—			(6,606		)	(14,571		)
	Transfers into Level 3	—			—			—			—			—
	Transfers out of Level 3	(23,629		)	(972		)	—			—			—
	Fixed maturities to short-term investments classification change	—			—			—			—			—
	Balance, end of period	$	4,382		$	8,928		$	11		$	5,926		$	718,827
	Movement in total gains (losses) above relating to instruments still held at the reporting date	$	148		$	—		$	2		$	—		$	4,969
		Level 3 Assets and Liabilities -Three Months Ended March 31, 2014
	(U.S. dollars in thousands)	Other asset-			Non-US Sovereign			Short-term			Other investments			Derivative Contracts
		backed			Government,			investments						- Net
		securities			Provincial,
					Supranational and
					Government
					Related/Supported
	Balance, beginning of period	$	11,877		$	—		$	2,015		$	113,472		$	(29,110	)
	Realized gains (losses)	(15		)	—			—			3,566			—
	Movement in unrealized gains (losses)	62			—			(15		)	1,494			(3,386		)
	Purchases and issuances	—			—			—			11,089			—
	Sales	—			—			—			—			—
	Settlements	(1,251		)	—			(2,000		)	(13,203		)	—
	Transfers into Level 3	—			—			—			—			—
	Transfers out of Level 3	—			—			—			—			—
	Fixed maturities to short-term investments classification change	—			—			—			—			—
	Balance, end of period	$	10,673		$	—		$	—		$	116,418		$	(32,496	)
Movement in total gains (losses) above relating to instruments still held at the reporting date	$	46		$	—		$	—		$	5,061		$	(3,386	)
Financial Instruments Not Carried at Fair Value
		March 31, 2015						December 31, 2014
	(U.S. dollars in thousands)	Carrying			Fair			Carrying			Fair
		Value			Value			Value			Value
	Financial Assets - Other investments, structured transactions	$	354,352		$	367,491		$	354,382		$	371,625
	Deposit liabilities	$	1,211,203		$	1,528,570		$	1,245,367		$	1,543,761
	Notes payable and debt	2,643,561			2,957,605			1,662,580			1,897,854
	Financial Liabilities	$	3,854,764		$	4,486,175		$	2,907,947		$	3,441,615

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Schedule of segment reporting, by segment	The following tables summarize the segment results for the three months ended March 31, 2015 and 2014:
	Three Months Ended March 31, 2015	Insurance			Reinsurance			Total P&C			Corporate			Total
	(U.S. dollars in thousands, except ratios)										and Other (1)
	Gross premiums written	$	1,654,747		$	825,662		$	2,480,409		$	74,951		$	2,555,360
	Net premiums written	1,089,108			747,635			1,836,743			14,506			1,851,249
	Net premiums earned	962,306			357,188			1,319,494			14,506			1,334,000
	Net losses and loss expenses	616,947			152,880			769,827			19,387			789,214
	Acquisition costs	80,387			71,492			151,879			1,817			153,696
	Operating expenses (2)	208,457			42,495			250,952			931			251,883
	Underwriting profit (loss)	$	56,515		$	90,321		$	146,836		$	(7,629	)	$	139,207
	Net investment income - excluding Life Funds Withheld Assets (3)							132,808			10,210			143,018
	Net investment income - Life Funds Withheld Assets										50,419			50,419
	Net results from structured products (4)	2,905			2,120			5,025			—			5,025
	Net fee income and other (5)	(7,465		)	825			(6,640		)	132			(6,508		)
	Net realized gains (losses) on investments - excluding Life Funds Withheld Assets							5,807			(1,205		)	4,602
	Net realized gains (losses) on investments and net unrealized gains (losses) on investments, Trading - Life Funds Withheld Assets							—			48,289			48,289
	Net realized and unrealized gains (losses) on derivative instruments							—			16,521			16,521
	Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets							—			(229,367		)	(229,367		)
	Net income (loss) from investment fund affiliates and operating affiliates (6)							—			57,997			57,997
	Exchange (gains) losses							—			27,390			27,390
	Corporate operating expenses							—			62,443			62,443
	Contribution from P&C and Corporate and Other							283,836			(144,466		)	139,370
	Interest expense (7)										41,481			41,481
	Non-controlling interests										37,390			37,390
	Income tax expense										24,218			24,218
	Net income (loss) attributable to ordinary shareholders													$	36,281
	Ratios – P&C operations: (8)
	Loss and loss expense ratio	64.1		%	42.8		%	58.3		%
	Underwriting expense ratio	30		%	31.9		%	30.6		%
	Combined ratio	94.1		%	74.7		%	88.9		%
	____________
	-1	Corporate and Other includes other items of our revenue and expenditures that are not evaluated at the segment level for reporting purposes, as well as the Company's Run-Off Life Operations.
	-2	Operating expenses of the segments exclude Corporate operating expenses, shown separately.
	-3	Net investment income - excluding Life Funds Withheld Assets does not include net investment income related to the net results from structured products.
	-4	The net results from P&C structured products include net investment income and interest expense of $15.1 million and $10.0 million, respectively.
	-5	Net fee income and other includes operating expenses from the Company's loss prevention consulting services business.
	-6	The Company generally records the income related to the alternative funds and to the private investment and operating fund affiliates on a one-month and three-month lag, respectively.
	-7	Interest expense excludes interest expense related to deposit liabilities recorded in the Insurance and Reinsurance segments.
	-8	Ratios are based on net premiums earned from P&C operations.
	Three Months Ended March 31, 2014	Insurance			Reinsurance			Total P&C			Corporate			Total
	(U.S. dollars in thousands, except ratios)										and Other (1)
	Gross premiums written	$	1,570,926		$	857,713		$	2,428,639		$	84,297		$	2,512,936
	Net premiums written	1,127,367			792,173			1,919,540			76,311			1,995,851
	Net premiums earned	992,440			420,088			1,412,528			76,311			1,488,839
	Net losses and loss expenses	639,193			192,312			831,505			113,587			945,092
	Acquisition costs	105,000			87,235			192,235			7,179			199,414
	Operating expenses (2)	203,053			40,861			243,914			3,188			247,102
	Underwriting profit (loss)	$	45,194		$	99,680		$	144,874		$	(47,643	)	$	97,231
	Net investment income - excluding Life Funds Withheld Assets (3)							143,527			70,892			214,419
	Net results from structured products (4)	4,890			3,063			7,953			—			7,953
	Net fee income and other (5)	(1,212		)	673			(539		)	45			(494		)
	Net realized gains (losses) on investments - excluding Life Funds Withheld Assets							17,666			1,563			19,229
	Net realized and unrealized gains (losses) on derivative instruments							—			1,810			1,810
	Net income (loss) from investment fund affiliates and operating affiliates (6)							—			79,588			79,588
	Exchange (gains) losses							—			10,441			10,441
	Corporate operating expenses							—			51,338			51,338
	Contribution from P&C and Corporate and Other							313,481			44,476			357,957
	Interest expense (7)										32,160			32,160
	Non-controlling interests										35,759			35,759
	Income tax expense										34,321			34,321
	Net income (loss) attributable to ordinary shareholders													$	255,717
	Ratios – P&C operations: (8)
	Loss and loss expense ratio	64.4		%	45.8		%	58.9		%
	Underwriting expense ratio	31		%	30.5		%	30.8		%
Combined ratio	95.4		%	76.3		%	89.7		%
____________
-1	Corporate and Other includes other items of our revenue and expenditures that are not evaluated at the segment level for reporting purposes, as well as the Company's Run-Off Life Operations and Life Funds Withheld Assets since the sale of XLLR did not occur until May 1, 2014.
-2	Operating expenses of the segments exclude Corporate operating expenses, shown separately.
-3	Net investment income does not include net investment income related to the net results from structured products.
-4	The net results from P&C structured products include net investment income and interest expense of $18.8 million and $10.8 million, respectively.
-5	Net fee income and other includes operating expenses from the Company's loss prevention consulting services business.
-6	The Company generally records the income related to the alternative funds and to the private investment and operating fund affiliates on a one-month and three-month lag, respectively.
-7	Interest expense excludes interest expense related to deposit liabilities recorded in the Insurance and Reinsurance segments.
-8	Ratios are based on net premiums earned from P&C operations.
Schedule of net premiums earned by line of business	The following tables summarize the Company’s net premiums earned by line of business for the three months ended March 31, 2015 and 2014:
	Three Months Ended March 31, 2015	Insurance			Reinsurance			Corporate			Total
	(U.S. dollars in thousands)							and Other
	P&C Operations:
	Professional	$	266,411		$	35,008		$	—		$	301,419
	Casualty	309,335			58,208			—			367,543
	Property catastrophe	—			94,073			—			94,073
	Property	128,241			131,224			—			259,465
	Marine, energy, aviation and satellite	—			18,075			—			18,075
	Specialty	184,724			—			—			184,724
	Other (1)	73,595			20,600			—			94,195
	Total P&C Operations	$	962,306		$	357,188		$	—		$	1,319,494
	Corporate and Other:
	Run-off Life operations - Annuity	$	—		$	—		$	(1	)	$	(1	)
	Run-off Life operations - Other Life	—			—			14,507			14,507
	Total Corporate and Other	$	—		$	—		$	14,506		$	14,506
	Total	$	962,306		$	357,188		$	14,506		$	1,334,000
	Three Months Ended March 31, 2014	Insurance			Reinsurance			Corporate			Total
	(U.S. dollars in thousands)							and Other
	P&C Operations:
	Professional	$	275,427		$	50,104		$	—		$	325,531
	Casualty	344,004			76,721			—			420,725
	Property catastrophe	—			108,437			—			108,437
	Property	139,733			135,239			—			274,972
	Marine, energy, aviation and satellite	—			23,514			—			23,514
	Specialty	176,909			—			—			176,909
	Other (1)	56,367			26,073			—			82,440
	Total P&C Operations	$	992,440		$	420,088		$	—		$	1,412,528
	Corporate and Other:
	Run-off Life operations - Annuity	$	—		$	—		$	31,797		$	31,797
	Run-off Life operations - Other Life	—			—			44,514			44,514
	Total Corporate and Other	$	—		$	—		$	76,311		$	76,311
	Total	$	992,440		$	420,088		$	76,311		$	1,488,839
	____________
	-1	Other within the Insurance segment includes: excess and surplus, programs, surety, structured indemnity and certain discontinued lines. Other within the Reinsurance segment includes: whole account contracts, accident and health and other lines.

Investments_Tables

Investments (Tables)	3 Months Ended
	Mar. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Amortized cost and fair value summary	The cost (amortized cost for fixed maturities and short-term investments), fair value, gross unrealized gains and gross unrealized (losses), including OTTI recorded in accumulated other comprehensive income (“AOCI”) of the Company’s AFS investments as of March 31, 2015 and December 31, 2014, were as follows:
	31-Mar-15	Cost or			Gross			Gross Unrealized Losses			Fair Value			Non-credit Related OTTI (1)
	(U.S. dollars in thousands)	Amortized			Unrealized
		Cost			Gains
	Fixed maturities - AFS - Excluding Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	3,299,458		$	87,025		$	(8,141	)	$	3,378,342		$	—
	Corporate (2)	7,806,607			398,357			(50,326		)	8,154,638			(3,309		)
	RMBS – Agency	3,585,638			131,468			(5,772		)	3,711,334			—
	RMBS – Non-Agency	368,317			29,770			(17,952		)	380,135			(58,364		)
	CMBS	1,010,518			25,603			(3,401		)	1,032,720			(1,801		)
	CDO	520,929			1,675			(21,630		)	500,974			(1,648		)
	Other asset-backed securities (2)	1,134,928			41,386			(8,947		)	1,167,367			(1,662		)
	U.S. States and political subdivisions of the States	1,842,561			131,843			(1,264		)	1,973,140			—
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	4,010,656			154,829			(71,714		)	4,093,771			—
	Total fixed maturities - AFS - Excluding Life Funds Withheld Assets	$	23,579,612		$	1,001,956		$	(189,147	)	$	24,392,421		$	(66,784	)
	Total short-term investments - Excluding Life Funds Withheld Assets	$	169,903		$	149		$	(1,190	)	$	168,862		$	—
	Total equity securities - Excluding Life Funds Withheld Assets	$	665,682		$	132,731		$	(14,942	)	$	783,471		$	—
	Total investments - AFS - Excluding Life Funds Withheld Assets	$	24,415,197		$	1,134,836		$	(205,279	)	$	25,344,754		$	(66,784	)
	Fixed maturities - AFS - Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	13,163		$	4,450		$	—		$	17,613		$	—
	Corporate (2)	2,277,295			468,931			—			2,746,226			—
	RMBS – Agency	1,641			489			—			2,130			—
	RMBS – Non-Agency	32,880			5,928			—			38,808			—
	CMBS	131,830			27,427			—			159,257			—
	Other asset-backed securities	209,714			34,426			—			244,140			—
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	1,123,966			385,839			—			1,509,805			—
	Total fixed maturities - AFS - Life Funds Withheld Assets	$	3,790,489		$	927,490		$	—		$	4,717,979		$	—
	Total investments - AFS	$	28,205,686		$	2,062,326		$	(205,279	)	$	30,062,733		$	(66,784	)
	Fixed maturities - Trading - Life Funds Withheld Assets										Amortized Cost			Fair Value
	Corporate										$	136,681		$	137,438
	Other asset-backed securities										1,966			1,939
	Total investments - Trading - Life Funds Withheld Assets										$	138,647		$	139,377
	___________
	-1	Represents the non-credit component of OTTI losses, adjusted for subsequent sales of securities. It does not include the change in fair value subsequent to the date an impairment was recorded.
	-2	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes have a fair value of $74.8 million and an amortized cost of $63.8 million. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.
	31-Dec-14	Cost or			Gross			Gross Unrealized Losses			Fair Value			Non-credit Related OTTI (1)
	(U.S. dollars in thousands)	Amortized			Unrealized
		Cost			Gains
	Fixed maturities - AFS - Excluding Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	2,100,851		$	77,889		$	(6,787	)	$	2,171,953		$	—
	Corporate (2)	8,462,130			365,805			(49,562		)	8,778,373			(3,309		)
	RMBS – Agency	3,625,171			114,188			(10,783		)	3,728,576			—
	RMBS – Non-Agency	404,398			41,108			(18,155		)	427,351			(67,918		)
	CMBS	1,033,819			23,987			(5,262		)	1,052,544			(2,033		)
	CDO	717,544			1,659			(27,169		)	692,034			(1,663		)
	Other asset-backed securities (2)	1,028,528			42,810			(6,045		)	1,065,293			(1,797		)
	U.S. States and political subdivisions of the States	1,892,566			129,910			(1,204		)	2,021,272			—
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	4,162,425			139,484			(61,836		)	4,240,073			—
	Total fixed maturities - AFS - Excluding Life Funds Withheld Assets	$	23,427,432		$	936,840		$	(186,803	)	$	24,177,469		$	(76,720	)
	Total short-term investments - Excluding Life Funds Withheld Assets	$	257,221		$	49		$	(543	)	$	256,727		$	—
	Total equity securities - Excluding Life Funds Withheld Assets	$	763,833		$	130,689		$	(26,230	)	$	868,292		$	—
	Total investments - AFS - Excluding Life Funds Withheld Assets	$	24,448,486		$	1,067,578		$	(213,576	)	$	25,302,488		$	(76,720	)
	Fixed maturities - AFS - Life Funds Withheld Assets
	U.S. Government and Government-Related/Supported	$	14,866		$	3,858		$	—		$	18,724		$	—
	Corporate (2)	2,407,849			410,131			—			2,817,980			—
	RMBS – Agency	3,301			481			—			3,782			—
	RMBS – Non-Agency	71,075			14,260			—			85,335			—
	CMBS	168,886			24,281			—			193,167			—
	Other asset-backed securities	238,168			35,373			—			273,541			—
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	1,397,194			391,842			—			1,789,036			—
	Total fixed maturities - AFS - Life Funds Withheld Assets	$	4,301,339		$	880,226		$	—		$	5,181,565		$	—
	Total investments - AFS	$	28,749,825		$	1,947,804		$	(213,576	)	$	30,484,053		$	(76,720	)
	Fixed maturities - Trading - Life Funds Withheld Assets										Amortized Cost			Fair Value
	Corporate										$	1,180		$	1,171
Total investments - Trading - Life Funds Withheld Assets										$	1,180		$	1,171
____________
-1	Represents the non-credit component of OTTI losses, adjusted for subsequent sales of securities. It does not include the change in fair value subsequent to the date an impairment was recorded.
-2	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes have a fair value of $79.9 million and an amortized cost of $68.4 million. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.
Contractual maturities summary	The contractual maturities of AFS fixed income securities at March 31, 2015 and December 31, 2014 are shown below. Actual maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties.
		31-Mar-15						31-Dec-14
	(U.S. dollars in thousands)	Amortized			Fair			Amortized			Fair
		Cost			Value			Cost			Value
	Fixed maturities - AFS - Excluding Life Funds Withheld Assets
	Due less than one year	$	1,770,647		$	1,781,224		$	1,972,224		$	1,980,429
	Due after 1 through 5 years	9,698,659			9,923,517			8,919,037			9,113,651
	Due after 5 through 10 years	4,049,907			4,226,001			4,232,396			4,412,569
	Due after 10 years	1,440,069			1,669,149			1,494,315			1,705,022
		$	16,959,282		$	17,599,891		$	16,617,972		$	17,211,671
	RMBS – Agency	3,585,638			3,711,334			3,625,171			3,728,576
	RMBS – Non-Agency	368,317			380,135			404,398			427,351
	CMBS	1,010,518			1,032,720			1,033,819			1,052,544
	CDO	520,929			500,974			717,544			692,034
	Other asset-backed securities	1,134,928			1,167,367			1,028,528			1,065,293
	Total mortgage and asset-backed securities	$	6,620,330		$	6,792,530		$	6,809,460		$	6,965,798
	Total fixed maturities - AFS - Excluding Life Funds Withheld Assets	$	23,579,612		$	24,392,421		$	23,427,432		$	24,177,469
	Fixed maturities - AFS - Life Funds Withheld Assets
	Due less than one year	$	97,637		$	107,530		$	117,048		$	125,326
	Due after 1 through 5 years	626,869			676,507			638,526			685,787
	Due after 5 through 10 years	798,923			933,986			1,004,698			1,165,348
	Due after 10 years	1,890,995			2,555,621			2,059,637			2,649,279
		$	3,414,424		$	4,273,644		$	3,819,909		$	4,625,740
	RMBS – Agency	1,641			2,130			3,301			3,782
	RMBS – Non-Agency	32,880			38,808			71,075			85,335
	CMBS	131,830			159,257			168,886			193,167
	Other asset-backed securities	209,714			244,140			238,168			273,541
	Total mortgage and asset-backed securities	$	376,065		$	444,335		$	481,430		$	555,825
	Total fixed maturities - AFS - Life Funds Withheld Assets	$	3,790,489		$	4,717,979		$	4,301,339		$	5,181,565
	Total fixed maturities - AFS	$	27,370,101		$	29,110,400		$	27,728,771		$	29,359,034
	Fixed maturities - Trading - Life Funds Withheld Assets
	Due less than one year	$	—		$	—		$	—		$	—
	Due after 1 through 5 years	64,739			64,733			—			—
	Due after 5 through 10 years	5,188			5,131			1,180			1,171
	Due after 10 years	66,754			67,574			—			—
		$	136,681		$	137,438		$	1,180		$	1,171
	Other asset-backed securities	1,966			1,939			—			—
	Total mortgage and asset-backed securities	$	1,966		$	1,939		$	—		$	—
	Total fixed maturities - Trading - Life Funds Withheld Assets	$	138,647		$	139,377		$	1,180		$	1,171
Summary of unrealized losses	The following is an analysis of how long the AFS securities as of March 31, 2015 and December 31, 2014 had been in a continual unrealized loss position:
		Less than 12 months						Equal to or greater
								than 12 months
	31-Mar-15	Fair			Gross			Fair			Gross
	(U.S. dollars in thousands)	Value			Unrealized			Value			Unrealized
					Losses						Losses
	Fixed maturities and short-term investments - AFS
	U.S. Government and Government-Related/Supported	$	249,646		$	(3,541	)	$	143,891		$	(4,619	)
	Corporate	688,725			(40,874		)	190,397			(9,730		)
	RMBS – Agency	177,627			(914		)	279,354			(4,858		)
	RMBS – Non-Agency	51,876			(1,815		)	188,932			(16,137		)
	CMBS	120,862			(393		)	109,324			(3,008		)
	CDO	92,517			(294		)	346,372			(21,336		)
	Other asset-backed securities	92,193			(6,219		)	37,357			(2,728		)
	U.S. States and political subdivisions of the States	55,707			(695		)	15,310			(569		)
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	681,300			(39,085		)	322,974			(33,522		)
	Total fixed maturities and short-term investments - AFS	$	2,210,453		$	(93,830	)	$	1,633,911		$	(96,507	)
	Total equity securities	$	119,625		$	(14,942	)	$	—		$	—
		Less than 12 months						Equal to or greater
								than 12 months
	31-Dec-14	Fair			Gross			Fair			Gross
	(U.S. dollars in thousands)	Value			Unrealized			Value			Unrealized
					Losses						Losses
	Fixed maturities and short-term investments - AFS
	U.S. Government and Government-Related/Supported	$	251,091		$	(1,196	)	$	342,890		$	(5,603	)
	Corporate	1,337,470			(33,881		)	424,221			(15,754		)
	RMBS – Agency	134,535			(220		)	512,652			(10,563		)
	RMBS – Non-Agency	45,378			(1,358		)	202,700			(16,797		)
	CMBS	78,356			(385		)	169,065			(4,877		)
	CDO	249,803			(2,666		)	414,516			(24,503		)
	Other asset-backed securities	143,044			(2,813		)	57,544			(3,232		)
	U.S. States and political subdivisions of the States	32,187			(210		)	63,695			(994		)
	Non-U.S. Sovereign Government, Provincial, Supranational and Government-Related/Supported	624,346			(19,043		)	558,422			(43,251		)
	Total fixed maturities and short-term investments - AFS	$	2,896,210		$	(61,772	)	$	2,745,705		$	(125,574	)
	Total equity securities	$	191,193		$	(26,230	)	$	—		$	—
Analysis of net realized gains (losses) on investments	The following represents an analysis of net realized gains (losses) on investments:
	Net Realized Gains (Losses) on Investments	Three months ended March 31,
	(U.S. dollars in thousands)	2015			2014
	Net realized gains (losses) on investments - excluding Life Funds Withheld Assets:
	Gross realized gains	$	62,300		$	51,213
	Gross realized losses on investments sold	(47,122		)	(28,257		)
	OTTI on investments, net of amounts transferred to other comprehensive income	(10,576		)	(3,727		)
		$	4,602		$	19,229
	Net realized gains (losses) on investments and net unrealized gains (losses) on investments, Trading - Life Funds Withheld Assets:
	Gross realized gains	$	53,128		$	—
	Gross realized losses on investments sold	(390		)	—
	OTTI on investments, net of amounts transferred to other comprehensive income	(5,209		)	—
	Net unrealized gains (losses) on trading securities	$	760		$	—
		$	48,289		$	—
	Total net realized gains (losses) on investments	$	52,891		$	19,229
Credit loss impairments on fixed inmcome securities rollforward	The following table sets forth the amount of credit loss impairments on fixed income securities held by the Company for which a portion of the OTTI loss was recognized in OCI, as of the dates or for the periods indicated and the corresponding changes in such amounts.
	Credit Loss Impairments	Three months ended March 31,
	(U.S. dollars in thousands)	2015			2014
	Opening balance as of beginning of indicated period	$	131,942		$	174,805
	Credit loss impairment recognized in the current period on securities not previously impaired	7,560			12
	Credit loss impairments previously recognized on securities which matured, paid down, prepaid or were sold during the period	(28,539		)	(3,348		)
	Additional credit loss impairments recognized in the current period on securities previously impaired	141			2,261
	Accretion of credit loss impairments previously recognized due to an increase in cash flows expected to be collected	(2,646		)	(2,347		)
	Balance as of March 31,	$	108,458		$	171,383

Derivative_Instruments_Tables

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Summary of location and gross amounts of derivative fair values	The following table summarizes information on the location and gross amounts of derivative fair values contained in the consolidated balance sheets as of March 31, 2015 and December 31, 2014:
		March 31, 2015											December 31, 2014
	(U.S. dollars in thousands)	Asset				Asset			Liability		Liability		Asset		Asset		Liability		Liability
		Derivative				Derivative			Derivative		Derivative		Derivative		Derivative		Derivative		Derivative
		Notional				Fair Value			Notional		Fair Value		Notional		Fair Value		Notional		Fair Value
		Amount				-1			Amount		-1		Amount		-1		Amount		-1
	Derivatives designated as hedging instruments:
	Foreign exchange contracts	$	204,811			$	38,376		$	204,811	$	26,505	$	2,300,609	$	121,862	$	302,211	$	2,936
	Total derivatives designated as hedging instruments	$	204,811			$	38,376		$	204,811	$	26,505	$	2,300,609	$	121,862	$	302,211	$	2,936
	Derivatives not designated as hedging instruments:
	Investment Related Derivatives:
	Interest rate exposure	$	264,527			$	224		$	13,033	$	65	$	394,597	$	206	$	20,782	$	51
	Foreign exchange exposure	23,400				498			190,368		7,709		7,385		403		288,376		4,724
	Credit exposure	2,408				205			14,270		9,836		2,408		165		14,270		9,836
	Financial market exposure	33,362				513			33,136		63		46,145		360		33,670		34
	Other Non-Investment Derivatives:
	Foreign exchange contracts	2,304,633				205,083			2,366,968		65,294		—		—		—		—
	Credit exposure	31,060				218			—		—		31,060		60		—		—
	Guaranteed minimum income benefit contract	45,658				12,763			45,658		12,763		46,249		13,603		46,249		13,603
	Modified coinsurance funds withheld contracts (2)	65,530				—			5,045,540		—		64,947		—		5,401,278		—
	Total derivatives not designated as hedging instruments	$	2,770,578			$	219,504		$	7,708,973	$	95,730	$	592,791	$	14,797	$	5,804,625	$	28,248
	____________
	-1	Derivative instruments in an asset or liability position are included within Other assets or Other liabilities, respectively, in the balance sheets on a net basis where the Company has both a legal right of offset and the intention to settle the contracts on a net basis.
	-2	The fair value movements in derivative assets and liabilities relating to modified coinsurance funds withheld contracts are included within the associated asset or liability at each period end on the face of the balance sheets. Notional amounts associated with reinsurance agreements under which the Company assumes reinsurance risk are recorded as asset derivative notional amounts. Notional amounts associated with the Life Retro Arrangements under which the Company cedes reinsurance risk are recorded as liability derivative notional amounts. Included in the liability derivative notional amount as of March 31, 2015 is the cumulative net realized and unrealized loss on life retrocession embedded derivative of $654.6 million.
Summary of gross and net amounts of derivative fair values and associated collateral received or paid	The following table summarizes information on the gross and net amounts of derivative fair values and associated collateral received related to derivative assets, or paid related to derivative liabilities, reported in other assets and or other liabilities within our consolidated balance sheets as of March 31, 2015 and December 31, 2014:
											Gross Amounts Not Offset in the Balance Sheets
	31-Mar-15	Gross Amounts Recognized in the Balance Sheets				Gross Amounts Offset in the Balance Sheets			Net Amounts in the Balance Sheets		Financial Instruments		Cash Collateral		Net Amounts
	(U.S. dollars in thousands)
	Derivative Assets	$	257,880			$	587		$	257,293	$	—	$	183,675	$	73,618
	Derivative Liabilities	$	122,235			$	587		$	121,648	$	—	$	—	$	121,648
	31-Dec-14
	(U.S. dollars in thousands)
	Derivative Assets	$	136,659			$	696		$	135,963	$	—	$	78,580	$	57,383
	Derivative Liabilities	$	31,184			$	696		$	30,488	$	—	$	—	$	30,488
Gain (loss) recognized in income attributable to risk of hedged items	The following table provides the total impact on earnings relating to derivative instruments formally designated as fair value hedges along with the impacts of the related hedged items for the three months ended March 31, 2015 and 2014:
					Hedged Items - Amount of Gain/(Loss) Recognized in Income Attributable to Risk
	Derivatives Designated as Fair Value Hedges:	Gain/(Loss)				Fixed Maturity			Ineffective
	Three Months Ended March 31, 2015	Recognized				Investments			Portion of
	(U.S. dollars in thousands)	in Income on							Hedging
		Derivative							Relationship -
									Gain/(Loss)
	Interest rate exposure	$	—
	Foreign exchange exposure	—
	Total	$	—			$	—		$	—
	Three Months Ended March 31, 2014
	(U.S. dollars in thousands)
	Interest rate exposure	$	—
	Foreign exchange exposure	(6,531		)
	Total	$	(6,531	)		$	8,325		$	1,794
Summary of fair value hedges that have been settled and their impact on results	A summary of the fair value hedges that have been settled and their impact on results during the indicated periods as well as the remaining balance of fair value hedges and average years remaining to maturity as of March 31, 2015 and 2014 are shown below:
	Settlement of Fair Value Hedges - Summary	Fair Value Hedges -
		Deposit Liabilities
		March 31,
	(U.S. dollars in thousands, except years)	2015				2014
	Cumulative reduction to interest expense	$	97,705			$	41,270
	Remaining balance	$	135,490			$	191,925
	Weighted average years remaining to maturity	22.7				22.2
Summary of hedges of net investment in foreign operation	The following table provides the weighted average U.S. dollar equivalent of foreign denominated net assets that were hedged and the resulting derivative gain (loss) that was recorded in the Foreign currency translation adjustment, net of tax, account within AOCI for the three months ended March 31, 2015 and 2014:
	Derivative Instruments Designated as Hedges of the	Three months ended March 31,
	Net Investment in a Foreign Operation - Summary
	(U.S. dollars in thousands)	2015				2014
	Weighted average of U.S. dollar equivalent of foreign denominated net assets	$	628,941			$	2,687,455
	Derivative gains (losses) (1)	$	66,770			$	960
	____________
	-1	Derivative gains (losses) from derivative instruments designated as hedges of the net investment in a foreign operation are recorded in the cumulative translation adjustment account within AOCI for each period.
Summary of net realized and unrealized gains (losses) on derivative instruments	The following table provides the total impact on earnings relating to derivative instruments not formally designated as hedging instruments under authoritative accounting guidance and from the ineffective portion of fair value hedges. The impacts are all recorded through Net realized and unrealized gains (losses) on derivatives in the income statement for the three months ended March 31, 2015 and 2014:
	Net Realized and Unrealized Gains (Losses) on Derivative Instruments	Three months ended March 31,
	(U.S. dollars in thousands)	2015				2014
	Investment Related Derivatives:
	Interest rate exposure	$	9,637			$	348
	Foreign exchange exposure	(1,362		)		3,288
	Credit exposure	82				(404		)
	Financial market exposure	3,041				871
	Financial Operations Derivatives:
	Credit exposure	—				(4,800		)
	Other Non-Investment Derivatives:
	Foreign exchange contracts	2,059				—
	Credit exposure	1,346				—
	Guaranteed minimum income benefit contract	—				1,624
	Modified coinsurance funds withheld contract	1,718				(911		)
	Total gain (loss) recognized in income from derivatives not designated as hedging instruments	$	16,521			$	16
	Amount of gain (loss) recognized in income from ineffective	—				1,794
	portion of fair value hedges
	Net realized and unrealized gains (losses) on derivative instruments	$	16,521			$	1,810
	Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets	$	(229,367	)		$	—
Components of life retrocession embedded derivatives	The value of the life retrocession embedded derivative includes the interest income, realized and unrealized gains and losses on Life Funds Withheld Assets and certain related expenses subsequent to May 30, 2014 as follows:
	Components of Life Retrocession Embedded Derivative and Derivative Instruments - Life Funds Withheld Assets:	Three months ended March 31,
	(U.S. dollars in thousands)	2015				2014
	Interest income - Life Funds Withheld Assets	$	(50,996	)		—
	Realized and unrealized gains (losses) - Life Funds Withheld Assets	(152,830		)		—
	Other	96				—
	Net realized and unrealized gains (losses) on life retrocession embedded derivative	$	(203,730	)		$	—
	Net adjustments related to future policy benefit reserves, net of tax	$	(11,954	)		$	—
	Net realized and unrealized gains (losses) on derivative instruments - Life Funds Withheld Assets	$	(13,683	)		$	—
	Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets	$	(229,367	)		$	—
Summary of contingent credit features	The aggregate fair value of all derivative agreements containing such rating downgrade provisions that were in a liability position and any collateral posted under these agreements as of March 31, 2015 and December 31, 2014 were as follows:
	Contingent Credit Features - Summary:	31-Mar-15				31-Dec-14
	(U.S. dollars in thousands)
	Aggregate fair value of derivative agreements with downgrade provisions in a net liability position	$	5,598			$	5,770
	Collateral posted to counterparty	$	—			$	—

Share_Capital_Tables

Share Capital (Tables)	3 Months Ended
	Mar. 31, 2015
Stockholders' Equity Note [Abstract]
Schedule of Valuation Assumptions - Stock Options	The fair value of the options issued was estimated on the date of grant using the Black-Scholes option pricing model using the following weighted average assumptions:
	Dividend yield	2	%
	Risk free interest rate	1.7	%
	Volatility	21.9	%
	Expected lives	6.0 years

Notes_Payable_and_Debt_and_Fin1

Notes Payable and Debt and Financing Arrangements (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Letter of Credit Summary	The Company’s letter of credit facilities and revolving credit facilities at March 31, 2015 and December 31, 2014 were as follows:
	Letter of Credit Summary:	March 31, 2015 (1)			December 31, 2014 (1)
	(U.S. dollars in thousands except percentages)
	Revolving credit facility (2)	$	1,000,000		$	1,000,000
	Available letter of credit facilities - commitments (3)	$	3,575,000		$	3,575,000
	Available letter of credit facilities - in use	$	1,743,230		$	1,790,561
	Collateralized by certain assets of the Company’s investment portfolio	65.7		%	66.2		%
	____________
	-1	As of March 31, 2015 and December 31, 2014, there were eight available letter of credit facilities.
	-2	As of March 31, 2015 and December 31, 2014, the $1 billion of revolving credit available under the November 2013 unsecured credit agreements, which currently provide an aggregate amount for issuance of letters of credit and revolving credit loans up to $2 billion, was unutilized. The credit agreements entered into with Citicorp USA, Inc. in May through November 2013 (the "Citi Agreements") provide for issuance of letters of credit and revolving credit loans up to an aggregate amount of $575.0 million. As of March 31, 2015, $575.0 million of letters of credit were issued under these agreements and therefore such amount is not included in this line.
	-3	The available letter of credit facilities include $1 billion that is also included in the "revolving credit facility" line in this table, as part of the November 2013 credit agreements, which currently provide an aggregate amount of outstanding letters of credit and revolving credit loans of up to $2 billion. The Company has the option to increase the size of the facilities under these agreements by an additional $500 million across such facilities. The Company also has the option to increase the maximum amount of the letters of credit and revolving credit loans available under the 2013 credit agreements with Citicorp USA, Inc. with the lender's and issuing lender's consent.

Related_Party_Transactions_Tab

Related Party Transactions (Tables)	3 Months Ended
	Mar. 31, 2015
Related Party Transactions [Abstract]
Summary of related party transactions	During the three months ended March 31, 2015 and 2014, these contracts resulted in reported net premiums written, net reported claims and reported acquisition costs as summarized below.
	(U.S. dollars in thousands)	Three months ended March 31,
		2015		2014
	Reported net premiums written	$	27,076	$	16,240
	Net losses and loss expenses incurred	$	9,100	$	6,138
	Reported acquisition costs	$	9,012	$	7,629

Computation_of_Earnings_Per_Or1

Computation of Earnings Per Ordinary Share and Ordinary Share Equivalent (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Calculation of earnings per share	The following table sets forth the computation of basic and diluted earnings per ordinary share for the three months ended March 31, 2015 and 2014:
		Three Months Ended March 31,
	(U.S. dollars in thousands, except per share amounts)	2015		2014
	Basic earnings per ordinary share & ordinary share equivalents outstanding:
	Net income (loss) attributable to ordinary shareholders	$	36,281	$	255,717
	Weighted average ordinary shares outstanding, in thousands - basic	255,724		276,337
	Basic earnings per ordinary share & ordinary share equivalents outstanding	$	0.14	$	0.93
	Diluted earnings per ordinary share & ordinary share equivalents outstanding:
	Weighted average ordinary shares outstanding, in thousands - basic	255,724		276,337
	Impact of share-based compensation and certain conversion features, in thousands	4,980		4,121
	Weighted average ordinary shares outstanding, in thousands - diluted	260,704		280,458
	Diluted earnings per ordinary share & ordinary share equivalents outstanding	$	0.14	$	0.91
	Dividends per ordinary share	$	0.16	$	0.16

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2015
Comprehensive Income Loss Note [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The changes in AOCI, net of tax, by component for the three months ended March 31, 2015 and 2014 are as follows:
	Three months ended March 31, 2015	Unrealized Gains (Losses) on Investments (1)			OTTI Losses Recognized in AOCI			Foreign Currency Translation Adjustments			Underfunded Pension Liability			Cash Flow Hedge		Total
	(U.S. dollars in thousands)
	Balance, beginning of period, net of tax	$	1,590,114		$	(76,047	)	$	(11,188	)	$	(20,789	)	$	2,368	$	1,484,458
	OCI before reclassifications	254,267			—			32,404			975			—		287,646
	Amounts reclassified from AOCI	(74,781		)	9,936			—			—			95		(64,750		)
	Tax benefit (expense)	(5,805		)	(78		)	3,699			—			—		(2,184		)
	Net current period OCI - net of tax	173,681			9,858			36,103			975			95		220,712
	Balance, end of period, net of tax	$	1,763,795		$	(66,189	)	$	24,915		$	(19,814	)	$	2,463	$	1,705,170
	Three months ended March 31, 2014
	(U.S. dollars in thousands)
	Balance, beginning of period, net of tax	$	822,432		$	(89,190	)	$	14,541		$	(13,239	)	$	2,113	$	736,657
	OCI before reclassifications	265,250			—			(5,900		)	(31		)	—		259,319
	Amounts reclassified from AOCI	(22,638		)	3,409			—			—			110		(19,119		)
	Tax benefit (expense)	(32,103		)	(113		)	2,020			—			—		(30,196		)
	Net current period OCI - net of tax	210,509			3,296			(3,880		)	(31		)	110		210,004
	Balance, end of period, net of tax	$	1,032,941		$	(85,894	)	$	10,661		$	(13,270	)	$	2,223	$	946,661
	____________
	-1	Included in these amounts is the impact of Shadow Adjustments. As of December 31, 2014 the cumulative impact of these adjustments was $445.1 million. During the three months ended March 31, 2015, net movements of $(60.4) million were recorded, resulting in a total cumulative net impact of Shadow Adjustments on future policy benefit reserves of $384.8 million as of March 31, 2015.
Reclassification out of Accumulated Other Comprehensive Income	The reclassifications out of AOCI along with the associated income statement line items affected by component, and the total related tax (expense) benefit for the three months ended March 31, 2015 and 2014 are as follows:
	Gross Amount Reclassified From AOCI
	Details About AOCI Components	Three months ended March 31, 2015			Three months ended March 31, 2014			Affected Line Item in the Statement of Income
	(U.S. dollars in thousands)
	Unrealized gains and losses on investments:
		$	(78,551	)	$	(24,914	)	Net realized gains (losses) on investments sold
		15,724			2,276			OTTI on investments
		$	(11,954	)	$	—		Net realized and unrealized gains (losses) on life retrocession embedded derivative and derivative instruments - Life Funds Withheld Assets
		$	(74,781	)	$	(22,638	)	Total before tax
		87			453			Provision (benefit) for income tax
		$	(74,694	)	$	(22,185	)	Net of tax
	OTTI losses recognized in OCI:
		$	9,875		$	1,958		Net realized gains (losses) on investments sold
		61			1,451			OTTI on investments transferred to (from) OCI
		$	9,936		$	3,409		Total before tax
		(3		)	(113		)	Provision (benefit) for income tax
		$	9,933		$	3,296		Net of tax
	Gains and losses on cash flow hedges:
	Interest rate contracts	$	95		$	110		Interest Expense
		—			—			Provision (benefit) for income tax
		$	95		$	110		Net of tax
	Total reclassifications for the period, gross of tax	$	(64,750	)	$	(19,119	)
	Tax benefit (expense)	84			340
	Total reclassifications for the period, net of tax	$	(64,666	)	$	(18,779	)

Acquisition_and_Disposals_Acqu

Acquisition and Disposals - Acquisition Consideration (Details) (Subsequent Event, Catlin Group Limited)	0 Months Ended
In Thousands, except Share data, unless otherwise specified	1-May-15	1-May-15
	USD ($)	GBP (£)
Business Acquisition [Line Items]
Shares outstanding (including dilutive effects of warrants) that will receive cash and share consideration	384,118,000	384,118,000
Exchange ratio per the merger agreement	0.13	0.13
Share issuance to Catlin shareholders	49,935,000	49,935,000
Share Price	$37.08
Share issuance consideration	$1,851,601
Cash price component, per share in GBP		£ 3.88
Foreign exchange rate: GBP/USD	1.5349	1.5349
Cash consideration	2,287,579	1,490,377
Total acquisition consideration	$4,139,180

Acquisition_and_Disposals_Acqu1

Acquisition and Disposals - Acquisition Narrative (Details)	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2015	Mar. 30, 2015	Mar. 31, 2015	Mar. 31, 2015	Jan. 08, 2015	1-May-15	1-May-15	1-May-15	1-May-15
	USD ($)	USD ($)	Catlin Group Limited	Catlin Group Limited	Catlin Group Limited	Catlin Group Limited	Catlin Group Limited	Subsequent Event	Subsequent Event	Subsequent Event	Subsequent Event
			USD ($)	USD ($)	Operating expense	Interest expense	XL Cayman	Catlin Group Limited	Catlin Group Limited	Catlin Group Limited	Catlin Group Limited
					USD ($)	USD ($)	GBP (£)	USD ($)	GBP (£)	Cash on hand	Proceeds from debt issuance
										USD ($)	USD ($)
Business Acquisition [Line Items]
Ordinary shares, par value (in dollars per share)	$0.01	$0.01
Cash price component, per share in GBP									£ 3.88
Exchange ratio per the merger agreement								0.13	0.13
Share issuance to Catlin shareholders								49,935,000	49,935,000
Cash consideration								$2,287,579,000	£ 1,490,377,000	$1,310,000,000	$980,600,000
Available letter of credit facilities - commitments							1,600,000,000
Face value of issued notes				1,000,000,000
Acquisition, integration and financing costs			$25,500,000		$10,500,000	$15,000,000

Acquisition_and_Disposals_Sale

Acquisition and Disposals - Sale of Operating Affiliate (Details) (ARX Holding Corporation, USD $)	0 Months Ended
In Millions, unless otherwise specified	Apr. 02, 2015	Mar. 31, 2015	Apr. 01, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity method investment, ownership percentage		40.60%
Investment in affiliates		$222.60
Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration received			560
Gain on disposal	$337

Acquisition_and_Disposals_Impa

Acquisition and Disposals - Impact of Life Retro arrangements (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Underwriting profit (loss)	$139,207		$97,231
Net investment income	208,513		233,189
Exchange (gains) losses	-27,390		-10,441
Other income and expenses	-6,508	[1]	-494	[1]
Net realized and unrealized gains (losses) on life retrocession embedded derivative	16,521		1,810
Net income (loss)	73,671		291,476
Change in adjustments related to future policy benefit reserves, net of tax	60,356		-34,004
Change in cumulative translation adjustment	36,103		-3,880
Comprehensive income (loss)	220,712		210,004
XL Re Life (SAC) Ltd
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Comprehensive income (loss)	0
Life Funds Withheld Assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net investment income	50,419		0
Net realized gains (losses) on investments sold	52,738		0
Net unrealized gains (losses) on investments, trading securities	760		0
OTTI on investments	-5,209		0
Net realized and unrealized gains (losses) on life retrocession embedded derivative	-229,367		0
Change in net unrealized gains (losses) on investments, net of tax	37,115		0
Life Funds Withheld Assets | XL Re Life (SAC) Ltd
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Underwriting profit (loss)	603
Net investment income	50,419
Net realized gains (losses) on investments sold	52,738
Net unrealized gains (losses) on investments, trading securities	760
OTTI on investments	-5,209
Exchange (gains) losses	3,684
Other income and expenses	-1,298
Net realized and unrealized gains (losses) on life retrocession embedded derivative	-229,367
Net income (loss)	-127,670
Change in net unrealized gains (losses) on investments, net of tax	37,115
Change in adjustments related to future policy benefit reserves, net of tax	60,356
Change in cumulative translation adjustment	30,802
Total changes to other comprehensive income as a result of Life Retro Arrangements	128,273
Comprehensive income (loss)	$603
[1]	Net fee income and other includes operating expenses from the Company's loss prevention consulting services business.

Acquisition_and_Disposals_Sale1

Acquisition and Disposals - Sale of Life Re Narrative (Details) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	30-May-14	1-May-14	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Future policy benefit reserves	$4,375,863,000				$4,707,199,000
Future policy benefit reserves recoverable	3,933,589,000				4,265,678,000
Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable)	1,138,652,000				1,155,016,000
Underwriting profit (loss)	139,207,000	97,231,000
Comprehensive income (loss)	220,712,000	210,004,000
XL Re Life (SAC) Ltd
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of subsidiary stock, percentage			100.00%
Consideration received			570,000,000
Quota share reinsurance percentage			100.00%
Future policy benefit reserves recoverable	3,900,000,000
Loss on disposal				621,300,000
Funds withheld asset	5,100,000,000
Comprehensive income (loss)	0
Life insurance product line | XL Re Life (SAC) Ltd
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Future policy benefit reserves			5,200,000,000
Future policy benefit reserves retained			400,000,000
Future policy benefit reserves recoverable			4,800,000,000
Life Funds Withheld Assets | XL Re Life (SAC) Ltd
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Underwriting profit (loss)	603,000
Comprehensive income (loss)	$603,000

Fair_Value_Measurements_Schedu

Fair Value Measurements - Schedule of assets and liabilities that were accounted for at fair value (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, unless otherwise specified
Assets
Fixed maturities, at fair value	$29,110,400		$29,359,034
Equity securities, at fair value	783,471		868,292
Short-term investments, at fair value	168,862		256,727
Total investments available for sale	30,062,733		30,484,053
Fixed maturities, trading at fair value	139,377		1,171
Collateral and counterparty netting, assets	-587	[1]	-696	[1]
Liabilities
Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable)	1,138,652		1,155,016
Collateral and counterparty nettings, liabilities	-587	[1]	-696	[1]
Recurring
Assets
Total investments available for sale	30,062,733		30,484,053
Cash equivalents	2,228,498	[2]	1,501,832
Other investments	974,583	[3]	894,057	[3]
Other assets	257,293	[1]	135,963	[1]
Total assets accounted for at fair value	33,783,993		33,150,274
Liabilities
Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable)	654,561	[4]	450,831	[4]
Financial instruments sold, but not yet purchased	7,232	[5]	30,406	[5]
Other liabilities	121,648	[1]	30,488	[1]
Total liabilities accounted for at fair value	783,441		511,725
Recurring | Quoted prices in active markets for identical assets (Level 1)
Assets
Total investments available for sale	497,496		502,284
Cash equivalents	1,835,344	[2]	1,103,877
Other investments	0	[3]	0	[3]
Other assets	0	[1]	0	[1]
Total assets accounted for at fair value	2,333,628		1,606,621
Liabilities
Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable)	0	[4]	0	[4]
Financial instruments sold, but not yet purchased	1,572	[5]	4,737	[5]
Other liabilities	0	[1]	0	[1]
Total liabilities accounted for at fair value	1,572		4,737
Recurring | Significant other observable inputs (Level 2)
Assets
Total investments available for sale	29,058,389		29,280,719
Cash equivalents	393,154	[2]	397,955
Other investments	784,486	[3]	708,974	[3]
Other assets	244,900	[1]	122,996	[1]
Total assets accounted for at fair value	30,741,027		30,644,553
Liabilities
Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable)	654,561	[4]	450,831	[4]
Financial instruments sold, but not yet purchased	5,660	[5]	25,669	[5]
Other liabilities	99,649	[1]	7,757	[1]
Total liabilities accounted for at fair value	759,870		484,257
Recurring | Significant other unobservable inputs (Level 3)
Assets
Total investments available for sale	506,848		701,050
Cash equivalents	0	[2]	0
Other investments	190,097	[3]	185,083	[3]
Other assets	12,980	[1]	13,663	[1]
Total assets accounted for at fair value	709,925		899,796
Liabilities
Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable)	0	[4]	0	[4]
Financial instruments sold, but not yet purchased	0	[5]	0	[5]
Other liabilities	22,586	[1]	23,427	[1]
Total liabilities accounted for at fair value	22,586		23,427
Excluding Life Funds Withheld Assets
Assets
Fixed maturities, at fair value	24,392,421		24,177,469
Equity securities, at fair value	783,471		868,292
Short-term investments, at fair value	168,862		256,727
Total investments available for sale	25,344,754		25,302,488
Excluding Life Funds Withheld Assets | U.S. Government and Government - Related/Supported
Assets
Fixed maturities, at fair value	3,378,342		2,171,953
Excluding Life Funds Withheld Assets | Corporate
Assets
Fixed maturities, at fair value	8,154,638	[6]	8,778,373	[7]
Excluding Life Funds Withheld Assets | RMBS - Agency
Assets
Fixed maturities, at fair value	3,711,334		3,728,576
Excluding Life Funds Withheld Assets | RMBS - Non-Agency
Assets
Fixed maturities, at fair value	380,135		427,351
Excluding Life Funds Withheld Assets | Commercial mortgage-backed securities
Assets
Fixed maturities, at fair value	1,032,720		1,052,544
Excluding Life Funds Withheld Assets | Collateralized debt obligations
Assets
Fixed maturities, at fair value	500,974		692,034
Excluding Life Funds Withheld Assets | Other asset-backed securities
Assets
Fixed maturities, at fair value	1,167,367		1,065,293
Excluding Life Funds Withheld Assets | US States and political subdivisions of the States
Assets
Fixed maturities, at fair value	1,973,140		2,021,272
Excluding Life Funds Withheld Assets | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
Assets
Fixed maturities, at fair value	4,093,771		4,240,073
Excluding Life Funds Withheld Assets | Recurring
Assets
Fixed maturities, at fair value	24,392,421		24,177,469
Equity securities, at fair value	783,471		868,292
Short-term investments, at fair value	168,862	[8],[9]	256,727	[8],[9]
Total investments available for sale	25,344,754		25,302,488
Excluding Life Funds Withheld Assets | Recurring | U.S. Government and Government - Related/Supported
Assets
Fixed maturities, at fair value	3,378,342		2,171,953
Excluding Life Funds Withheld Assets | Recurring | Corporate
Assets
Fixed maturities, at fair value	8,154,638	[8]	8,778,373	[8]
Excluding Life Funds Withheld Assets | Recurring | RMBS - Agency
Assets
Fixed maturities, at fair value	3,711,334		3,728,576
Excluding Life Funds Withheld Assets | Recurring | RMBS - Non-Agency
Assets
Fixed maturities, at fair value	380,135		427,351
Excluding Life Funds Withheld Assets | Recurring | Commercial mortgage-backed securities
Assets
Fixed maturities, at fair value	1,032,720		1,052,544
Excluding Life Funds Withheld Assets | Recurring | Collateralized debt obligations
Assets
Fixed maturities, at fair value	500,974		692,034
Excluding Life Funds Withheld Assets | Recurring | Other asset-backed securities
Assets
Fixed maturities, at fair value	1,167,367		1,065,293
Excluding Life Funds Withheld Assets | Recurring | US States and political subdivisions of the States
Assets
Fixed maturities, at fair value	1,973,140		2,021,272
Excluding Life Funds Withheld Assets | Recurring | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
Assets
Fixed maturities, at fair value	4,093,771		4,240,073
Excluding Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1)
Assets
Fixed maturities, at fair value	0		0
Equity securities, at fair value	497,496		502,284
Short-term investments, at fair value	0	[8],[9]	0	[8],[9]
Total investments available for sale	497,496		502,284
Excluding Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | U.S. Government and Government - Related/Supported
Assets
Fixed maturities, at fair value	0		0
Excluding Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | Corporate
Assets
Fixed maturities, at fair value	0	[8]	0	[8]
Excluding Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | RMBS - Agency
Assets
Fixed maturities, at fair value	0		0
Excluding Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | RMBS - Non-Agency
Assets
Fixed maturities, at fair value	0		0
Excluding Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | Commercial mortgage-backed securities
Assets
Fixed maturities, at fair value	0		0
Excluding Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | Collateralized debt obligations
Assets
Fixed maturities, at fair value	0		0
Excluding Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | Other asset-backed securities
Assets
Fixed maturities, at fair value	0		0
Excluding Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | US States and political subdivisions of the States
Assets
Fixed maturities, at fair value	0		0
Excluding Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
Assets
Fixed maturities, at fair value	0		0
Excluding Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2)
Assets
Fixed maturities, at fair value	23,885,573		23,476,419
Equity securities, at fair value	285,975		366,008
Short-term investments, at fair value	168,862	[8],[9]	256,727	[8],[9]
Total investments available for sale	24,340,410		24,099,154
Excluding Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | U.S. Government and Government - Related/Supported
Assets
Fixed maturities, at fair value	3,378,342		2,171,953
Excluding Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | Corporate
Assets
Fixed maturities, at fair value	8,148,777	[8]	8,772,479	[8]
Excluding Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | RMBS - Agency
Assets
Fixed maturities, at fair value	3,709,514		3,726,666
Excluding Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | RMBS - Non-Agency
Assets
Fixed maturities, at fair value	380,135		427,351
Excluding Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | Commercial mortgage-backed securities
Assets
Fixed maturities, at fair value	1,032,720		1,052,544
Excluding Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | Collateralized debt obligations
Assets
Fixed maturities, at fair value	4,051		4,076
Excluding Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | Other asset-backed securities
Assets
Fixed maturities, at fair value	1,165,123		1,060,005
Excluding Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | US States and political subdivisions of the States
Assets
Fixed maturities, at fair value	1,973,140		2,021,272
Excluding Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
Assets
Fixed maturities, at fair value	4,093,771		4,240,073
Excluding Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3)
Assets
Fixed maturities, at fair value	506,848		701,050
Equity securities, at fair value	0		0
Short-term investments, at fair value	0	[8],[9]	0	[8],[9]
Total investments available for sale	506,848		701,050
Excluding Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | U.S. Government and Government - Related/Supported
Assets
Fixed maturities, at fair value	0		0
Excluding Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | Corporate
Assets
Fixed maturities, at fair value	5,861	[8]	5,894	[8]
Excluding Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | RMBS - Agency
Assets
Fixed maturities, at fair value	1,820		1,910
Excluding Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | RMBS - Non-Agency
Assets
Fixed maturities, at fair value	0		0
Excluding Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | Commercial mortgage-backed securities
Assets
Fixed maturities, at fair value	0		0
Excluding Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | Collateralized debt obligations
Assets
Fixed maturities, at fair value	496,923		687,958
Excluding Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | Other asset-backed securities
Assets
Fixed maturities, at fair value	2,244		5,288
Excluding Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | US States and political subdivisions of the States
Assets
Fixed maturities, at fair value	0		0
Excluding Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
Assets
Fixed maturities, at fair value	0		0
Life Funds Withheld Assets
Assets
Fixed maturities, at fair value	4,717,979		5,181,565
Fixed maturities, trading at fair value	139,377		1,171
Life Funds Withheld Assets | U.S. Government and Government - Related/Supported
Assets
Fixed maturities, at fair value	17,613		18,724
Life Funds Withheld Assets | Corporate
Assets
Fixed maturities, at fair value	2,746,226	[6]	2,817,980	[7]
Fixed maturities, trading at fair value	137,438		1,171
Life Funds Withheld Assets | RMBS - Agency
Assets
Fixed maturities, at fair value	2,130		3,782
Life Funds Withheld Assets | RMBS - Non-Agency
Assets
Fixed maturities, at fair value	38,808		85,335
Life Funds Withheld Assets | Commercial mortgage-backed securities
Assets
Fixed maturities, at fair value	159,257		193,167
Life Funds Withheld Assets | Other asset-backed securities
Assets
Fixed maturities, at fair value	244,140		273,541
Fixed maturities, trading at fair value	1,939
Life Funds Withheld Assets | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
Assets
Fixed maturities, at fair value	1,509,805		1,789,036
Life Funds Withheld Assets | Recurring
Assets
Fixed maturities, at fair value	4,717,979		5,181,565
Fixed maturities, trading at fair value	139,377		1,171
Cash equivalents	121,509	[2]	133,198	[2]
Life Funds Withheld Assets | Recurring | U.S. Government and Government - Related/Supported
Assets
Fixed maturities, at fair value	17,613		18,724
Life Funds Withheld Assets | Recurring | Corporate
Assets
Fixed maturities, at fair value	2,746,226		2,817,980
Fixed maturities, trading at fair value	137,438		1,171
Life Funds Withheld Assets | Recurring | RMBS - Agency
Assets
Fixed maturities, at fair value	2,130		3,782
Life Funds Withheld Assets | Recurring | RMBS - Non-Agency
Assets
Fixed maturities, at fair value	38,808		85,335
Life Funds Withheld Assets | Recurring | Commercial mortgage-backed securities
Assets
Fixed maturities, at fair value	159,257		193,167
Life Funds Withheld Assets | Recurring | Other asset-backed securities
Assets
Fixed maturities, at fair value	244,140		273,541
Fixed maturities, trading at fair value	1,939
Life Funds Withheld Assets | Recurring | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
Assets
Fixed maturities, at fair value	1,509,805		1,789,036
Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1)
Assets
Fixed maturities, at fair value	0		0
Fixed maturities, trading at fair value	0		0
Cash equivalents	788	[2]	460	[2]
Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | U.S. Government and Government - Related/Supported
Assets
Fixed maturities, at fair value	0		0
Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | Corporate
Assets
Fixed maturities, at fair value	0		0
Fixed maturities, trading at fair value	0		0
Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | RMBS - Agency
Assets
Fixed maturities, at fair value	0		0
Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | RMBS - Non-Agency
Assets
Fixed maturities, at fair value	0		0
Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | Commercial mortgage-backed securities
Assets
Fixed maturities, at fair value	0		0
Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | Other asset-backed securities
Assets
Fixed maturities, at fair value	0		0
Fixed maturities, trading at fair value	0
Life Funds Withheld Assets | Recurring | Quoted prices in active markets for identical assets (Level 1) | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
Assets
Fixed maturities, at fair value	0		0
Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2)
Assets
Fixed maturities, at fair value	4,717,979		5,181,565
Fixed maturities, trading at fair value	139,377		1,171
Cash equivalents	120,721	[2]	132,738	[2]
Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | U.S. Government and Government - Related/Supported
Assets
Fixed maturities, at fair value	17,613		18,724
Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | Corporate
Assets
Fixed maturities, at fair value	2,746,226		2,817,980
Fixed maturities, trading at fair value	137,438		1,171
Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | RMBS - Agency
Assets
Fixed maturities, at fair value	2,130		3,782
Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | RMBS - Non-Agency
Assets
Fixed maturities, at fair value	38,808		85,335
Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | Commercial mortgage-backed securities
Assets
Fixed maturities, at fair value	159,257		193,167
Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | Other asset-backed securities
Assets
Fixed maturities, at fair value	244,140		273,541
Fixed maturities, trading at fair value	1,939
Life Funds Withheld Assets | Recurring | Significant other observable inputs (Level 2) | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
Assets
Fixed maturities, at fair value	1,509,805		1,789,036
Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3)
Assets
Fixed maturities, at fair value	0		0
Fixed maturities, trading at fair value	0		0
Cash equivalents	0	[2]	0	[2]
Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | U.S. Government and Government - Related/Supported
Assets
Fixed maturities, at fair value	0		0
Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | Corporate
Assets
Fixed maturities, at fair value	0		0
Fixed maturities, trading at fair value	0		0
Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | RMBS - Agency
Assets
Fixed maturities, at fair value	0		0
Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | RMBS - Non-Agency
Assets
Fixed maturities, at fair value	0		0
Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | Commercial mortgage-backed securities
Assets
Fixed maturities, at fair value	0		0
Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | Other asset-backed securities
Assets
Fixed maturities, at fair value	0		0
Fixed maturities, trading at fair value	0
Life Funds Withheld Assets | Recurring | Significant other unobservable inputs (Level 3) | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
Assets
Fixed maturities, at fair value	$0		$0
[1]	Other assets and other liabilities include derivative instruments. The derivative balances included in each category are reported on a gross basis by level with a netting adjustment presented separately in the Collateral and Counterparty Netting column. The fair values of the individual derivative contracts are reported gross in their respective levels based on the fair value hierarchy. For further details regarding derivative fair values and associated collateral received or paid see Note 7, bDerivative Instruments,b to the Unaudited Consolidated Financial Statements.
[2]	Cash equivalents balances subject to fair value measurement include certificates of deposit and money market funds. Operating cash balances are not subject to recurring fair value measurement guidance.
[3]	The Other investments balance excludes certain structured transactions including certain investments in project finance transactions, a payment obligation and liquidity financing provided to a structured credit vehicle as a part of a third party medium term note facility. These investments, which totaled $354.4 million as of MarchB 31, 2015 and $354.4 million at DecemberB 31, 2014, are carried at amortized cost. For further information, see Item 8, Note 8, bOther Investments,b to the Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended DecemberB 31, 2014.
[4]	Funds withheld on life retrocession arrangements (net of future policy benefit reserves recoverable) include balances related to the life retrocession embedded derivative, under which all investment results associated with the Life Funds Withheld Assets related to the Life Retro Arrangements described in Note 3(c), bAcquisition and Disposals - Sale of Life Reinsurance Subsidiary," accrue to the benefit of GCLR.
[5]	Financial instruments sold, but not yet purchased, represent bshort salesb and are included within bPayable for investments purchasedb on the balance sheets.
[6]	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes have a fair value of $74.8 million and an amortized cost of $63.8 million. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.
[7]	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes have a fair value of $79.9 million and an amortized cost of $68.4 million. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.
[8]	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes had a fair value of $74.8 million and $79.9 million and an amortized cost of $63.8 million and $68.4 million as of MarchB 31, 2015 and DecemberB 31, 2014, respectively. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.
[9]	Short-term investments consist primarily of Corporate securities and U.S. and Non-U.S. Government and Government-Related/Supported securities.

Fair_Value_Measurements_Additi

Fair Value Measurements - Additional information about assets and liabilities measured at fair value on a recurring basis (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Derivative contracts - net
Level 3 liabilities
Balance, beginning of period	($9,764)	($29,110)
Realized gains (losses)	0	0
Movement in unrealized gains (losses)	158	-3,386
Purchases and issuances	0	0
Sales		0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, end of period	-9,606	-32,496
Movement in total gains (losses) above relating to instruments still held at the reporting date	158	-3,386
Corporate
Level 3 assets
Balance, beginning of period	5,894	31,573
Realized gains (losses)	-1	120
Movement in unrealized gains (losses)	48	-2
Purchases and issuances	0	1,434
Sales	0	0
Settlements	-80	-5,114
Transfers into Level 3		0
Transfers out of Level 3	0	-23,629
Fixed maturities to short-term investments classification change	0	0
Balance, end of period	5,861	4,382
Movement in total gains (losses) above relating to instruments still held at the reporting date	48	148
RMBS - Agency
Level 3 assets
Balance, beginning of period	1,910	10,473
Realized gains (losses)	0	-1
Movement in unrealized gains (losses)	-1	1
Purchases and issuances	0	0
Sales	0	0
Settlements	-89	-573
Transfers into Level 3	0	0
Transfers out of Level 3	0	-972
Fixed maturities to short-term investments classification change	0	0
Balance, end of period	1,820	8,928
Movement in total gains (losses) above relating to instruments still held at the reporting date	-1	0
RMBS - Non-Agency
Level 3 assets
Balance, beginning of period	0	9
Realized gains (losses)	0	0
Movement in unrealized gains (losses)	0	2
Purchases and issuances	0	0
Sales	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fixed maturities to short-term investments classification change	0	0
Balance, end of period	0	11
Movement in total gains (losses) above relating to instruments still held at the reporting date	0	2
Commercial mortgage-backed securities
Level 3 assets
Balance, beginning of period	0	12,533
Realized gains (losses)	0	2
Movement in unrealized gains (losses)	0	-3
Purchases and issuances	0	0
Sales	0	0
Settlements	0	-6,606
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fixed maturities to short-term investments classification change	0	0
Balance, end of period	0	5,926
Movement in total gains (losses) above relating to instruments still held at the reporting date	0	0
Collateralized debt obligations
Level 3 assets
Balance, beginning of period	687,958	710,253
Realized gains (losses)	36	1,581
Movement in unrealized gains (losses)	5,555	3,681
Purchases and issuances	0	27,814
Sales	-155,085	-9,931
Settlements	-41,541	-14,571
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fixed maturities to short-term investments classification change	0	0
Balance, end of period	496,923	718,827
Movement in total gains (losses) above relating to instruments still held at the reporting date	2,668	4,969
Other asset-backed securities
Level 3 assets
Balance, beginning of period	5,288	11,877
Realized gains (losses)	-1	-15
Movement in unrealized gains (losses)	2	62
Purchases and issuances	0	0
Sales	0	0
Settlements	-3,045	-1,251
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fixed maturities to short-term investments classification change	0	0
Balance, end of period	2,244	10,673
Movement in total gains (losses) above relating to instruments still held at the reporting date	0	46
Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
Level 3 assets
Balance, beginning of period	0	0
Realized gains (losses)	0	0
Movement in unrealized gains (losses)	0	0
Purchases and issuances	0	0
Sales	0	0
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fixed maturities to short-term investments classification change	0	0
Balance, end of period	0	0
Movement in total gains (losses) above relating to instruments still held at the reporting date	0	0
Short-term investments
Level 3 assets
Balance, beginning of period	0	2,015
Realized gains (losses)	0	0
Movement in unrealized gains (losses)	0	-15
Purchases and issuances	0	0
Sales	0	0
Settlements	0	-2,000
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fixed maturities to short-term investments classification change	0	0
Balance, end of period	0	0
Movement in total gains (losses) above relating to instruments still held at the reporting date	0	0
Other investments
Level 3 assets
Balance, beginning of period	185,083	113,472
Realized gains (losses)	1,302	3,566
Movement in unrealized gains (losses)	-1,827	1,494
Purchases and issuances	6,793	11,089
Sales	0	0
Settlements	-1,254	-13,203
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Fixed maturities to short-term investments classification change	0	0
Balance, end of period	190,097	116,418
Movement in total gains (losses) above relating to instruments still held at the reporting date	($524)	$5,061

Fair_Value_Measurements_Financ

Fair Value Measurements - Financial instruments not carried at fair value (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Other investments - structured transactions	$354,400,000	$354,400,000
Deposit liabilities	1,211,203,000	1,245,367,000
Notes payable and debt	2,643,561,000	1,662,580,000
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Assets	354,352,000	354,382,000
Deposit liabilities	1,211,203,000	1,245,367,000
Notes payable and debt	2,643,561,000	1,662,580,000
Financial Liabilities	3,854,764,000	2,907,947,000
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial Assets	367,491,000	371,625,000
Deposit liabilities	1,528,570,000	1,543,761,000
Notes payable and debt	2,957,605,000	1,897,854,000
Financial Liabilities	$4,486,175,000	$3,441,615,000

Fair_Value_Measurements_Narrat

Fair Value Measurements - Narrative (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	$29,110,400,000	$29,359,034,000
Amortized cost of fixed maturities	27,370,101,000	27,728,771,000
Other investments - structured transactions	354,400,000	354,400,000
Spread on U.S. treasury for discounting deposit liabilities	0.33%	0.30%
Medium term notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed maturities, at fair value	74,800,000	79,900,000
Amortized cost of fixed maturities	$63,800,000	$68,400,000

Segment_Information_Statement_

Segment Information - Statement of earnings by segment (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Segment Reporting Information [Line Items]
Gross premiums written	$2,555,360		$2,512,936
Net premiums written	1,851,249		1,995,851
Net premiums earned	1,334,000		1,488,839
Net losses and loss expenses	789,214		945,092
Acquisition costs	153,696		199,414
Operating expenses	251,883	[1]	247,102	[1]
Underwriting profit (loss)	139,207		97,231
Net results from structured products	5,025	[2]	7,953	[3]
Net fee income and other	-6,508	[4]	-494	[4]
Net realized gains (losses) on investments	52,891		19,229
Net realized and unrealized gains (losses) on derivative instruments	16,521		1,810
Net income (loss) from investment fund affiliates and operating affiliates	57,997	[5]	79,588	[5]
Exchange (gains) losses	27,390		10,441
Corporate operating expenses	62,443		51,338
Contribution from P&C and Corporate and Other	139,370		357,957
Interest expense	41,481	[6]	32,160	[6]
Non-controlling interests	37,390		35,759
Income tax	24,218		34,321
Net income (loss) attributable to ordinary shareholders	36,281		255,717
Corporate and Other
Segment Reporting Information [Line Items]
Gross premiums written	74,951	[7]	84,297	[7]
Net premiums written	14,506	[7]	76,311	[7]
Net premiums earned	14,506	[7]	76,311	[7]
Net losses and loss expenses	19,387	[7]	113,587	[7]
Acquisition costs	1,817	[7]	7,179	[7]
Operating expenses	931	[1],[7]	3,188	[1],[7]
Underwriting profit (loss)	-7,629	[7]	-47,643	[7]
Net results from structured products	0	[2],[7]	0	[3],[7]
Net fee income and other	132	[4],[7]	45	[4],[7]
Net realized and unrealized gains (losses) on derivative instruments	16,521	[7]	1,810	[7]
Net income (loss) from investment fund affiliates and operating affiliates	57,997	[5],[7]	79,588	[5],[7]
Exchange (gains) losses	27,390	[7]	10,441	[7]
Corporate operating expenses	62,443	[7]	51,338	[7]
Contribution from P&C and Corporate and Other	-144,466	[7]	44,476	[7]
Interest expense	41,481	[6],[7]	32,160	[6],[7]
Non-controlling interests	37,390	[7]	35,759	[7]
Income tax	24,218	[7]	34,321	[7]
Total P&C
Segment Reporting Information [Line Items]
Gross premiums written	2,480,409		2,428,639
Net premiums written	1,836,743		1,919,540
Net premiums earned	1,319,494		1,412,528
Net losses and loss expenses	769,827		831,505
Acquisition costs	151,879		192,235
Operating expenses	250,952	[1]	243,914	[1]
Underwriting profit (loss)	146,836		144,874
Net results from structured products	5,025	[2]	7,953	[3]
Net fee income and other	-6,640	[4]	-539	[4]
Contribution from P&C and Corporate and Other	283,836		313,481
Ratios - P&C operations
Loss and loss expense ratio	58.30%	[8]	58.90%	[8]
Underwriting expense ratio	30.60%	[8]	30.80%	[8]
Combined ratio	88.90%	[8]	89.70%	[8]
Insurance Segment
Segment Reporting Information [Line Items]
Gross premiums written	1,654,747		1,570,926
Net premiums written	1,089,108		1,127,367
Net premiums earned	962,306		992,440
Net losses and loss expenses	616,947		639,193
Acquisition costs	80,387		105,000
Operating expenses	208,457	[1]	203,053	[1]
Underwriting profit (loss)	56,515		45,194
Net results from structured products	2,905	[2]	4,890	[3]
Net fee income and other	-7,465	[4]	-1,212	[4]
Ratios - P&C operations
Loss and loss expense ratio	64.10%	[8]	64.40%	[8]
Underwriting expense ratio	30.00%	[8]	31.00%	[8]
Combined ratio	94.10%	[8]	95.40%	[8]
Reinsurance Segment
Segment Reporting Information [Line Items]
Gross premiums written	825,662		857,713
Net premiums written	747,635		792,173
Net premiums earned	357,188		420,088
Net losses and loss expenses	152,880		192,312
Acquisition costs	71,492		87,235
Operating expenses	42,495	[1]	40,861	[1]
Underwriting profit (loss)	90,321		99,680
Net results from structured products	2,120	[2]	3,063	[3]
Net fee income and other	825	[4]	673	[4]
Ratios - P&C operations
Loss and loss expense ratio	42.80%	[8]	45.80%	[8]
Underwriting expense ratio	31.90%	[8]	30.50%	[8]
Combined ratio	74.70%	[8]	76.30%	[8]
Excluding Life Funds Withheld Assets
Segment Reporting Information [Line Items]
Net investment income	143,018	[9]	214,419	[9]
Net realized gains (losses) on investments	4,602		19,229
Excluding Life Funds Withheld Assets | Corporate and Other
Segment Reporting Information [Line Items]
Net investment income	10,210	[7],[9]	70,892	[7],[9]
Net realized gains (losses) on investments	-1,205	[7]	1,563	[7]
Excluding Life Funds Withheld Assets | Total P&C
Segment Reporting Information [Line Items]
Net investment income	132,808	[9]	143,527	[9]
Net realized gains (losses) on investments	5,807		17,666
Life Funds Withheld Assets
Segment Reporting Information [Line Items]
Net investment income	50,419
Net realized gains (losses) on investments	48,289		0
Net realized and unrealized gains (losses) on derivative instruments	-229,367		0
Life Funds Withheld Assets | Corporate and Other
Segment Reporting Information [Line Items]
Net investment income	50,419	[7]
Net realized gains (losses) on investments	48,289	[7]
Net realized and unrealized gains (losses) on derivative instruments	($229,367)	[7]
[1]	Operating expenses of the segments exclude Corporate operating expenses, shown separately.
[2]	The net results from P&C structured products include net investment income and interest expense of $15.1 million and $10.0 million, respectively.
[3]	The net results from P&C structured products include net investment income and interest expense of $18.8 million and $10.8 million, respectively.
[4]	Net fee income and other includes operating expenses from the Company's loss prevention consulting services business.
[5]	The Company generally records the income related to the alternative funds and to the private investment and operating fund affiliates on a one-month and three-month lag, respectively.
[6]	Interest expense excludes interest expense related to deposit liabilities recorded in the Insurance and Reinsurance segments
[7]	Corporate and Other includes other items of our revenue and expenditures that are not evaluated at the segment level for reporting purposes, as well as the Company's Run-Off Life Operations.
[8]	Ratios are based on net premiums earned from P&C operations.
[9]	Net investment income - excluding Life Funds Withheld Assets does not include net investment income related to the net results from structured products.

Segment_Information_Net_Premiu

Segment Information - Net Premiums Earned by Line of Business (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Net premiums earned by line of business:
P&C Operations	$1,319,494		$1,412,528
Life Operations	14,506		76,311
Total	1,334,000		1,488,839
Total P&C
Net premiums earned by line of business:
Total	1,319,494		1,412,528
Insurance Segment
Net premiums earned by line of business:
P&C Operations	962,306		992,440
Total	962,306		992,440
Reinsurance Segment
Net premiums earned by line of business:
P&C Operations	357,188		420,088
Total	357,188		420,088
Corporate and Other
Net premiums earned by line of business:
Life Operations	14,506		76,311
Total	14,506	[1]	76,311	[1]
Professional | Total P&C
Net premiums earned by line of business:
P&C Operations	301,419		325,531
Professional | Insurance Segment
Net premiums earned by line of business:
P&C Operations	266,411		275,427
Professional | Reinsurance Segment
Net premiums earned by line of business:
P&C Operations	35,008		50,104
Casualty | Total P&C
Net premiums earned by line of business:
P&C Operations	367,543		420,725
Casualty | Insurance Segment
Net premiums earned by line of business:
P&C Operations	309,335		344,004
Casualty | Reinsurance Segment
Net premiums earned by line of business:
P&C Operations	58,208		76,721
Property catastrophe | Total P&C
Net premiums earned by line of business:
P&C Operations	94,073		108,437
Property catastrophe | Insurance Segment
Net premiums earned by line of business:
P&C Operations	0		0
Property catastrophe | Reinsurance Segment
Net premiums earned by line of business:
P&C Operations	94,073		108,437
Property | Total P&C
Net premiums earned by line of business:
P&C Operations	259,465		274,972
Property | Insurance Segment
Net premiums earned by line of business:
P&C Operations	128,241		139,733
Property | Reinsurance Segment
Net premiums earned by line of business:
P&C Operations	131,224		135,239
Marine, energy, aviation and satellite | Total P&C
Net premiums earned by line of business:
P&C Operations	18,075		23,514
Marine, energy, aviation and satellite | Insurance Segment
Net premiums earned by line of business:
P&C Operations	0		0
Marine, energy, aviation and satellite | Reinsurance Segment
Net premiums earned by line of business:
P&C Operations	18,075		23,514
Specialty | Total P&C
Net premiums earned by line of business:
P&C Operations	184,724		176,909
Specialty | Insurance Segment
Net premiums earned by line of business:
P&C Operations	184,724		176,909
Specialty | Reinsurance Segment
Net premiums earned by line of business:
P&C Operations	0		0
Other | Total P&C
Net premiums earned by line of business:
P&C Operations	94,195	[2]	82,440	[2]
Other | Insurance Segment
Net premiums earned by line of business:
P&C Operations	73,595	[2]	56,367	[2]
Other | Reinsurance Segment
Net premiums earned by line of business:
P&C Operations	20,600	[2]	26,073	[2]
Annuity
Net premiums earned by line of business:
Life Operations	-1		31,797
Annuity | Corporate and Other
Net premiums earned by line of business:
Life Operations	-1		31,797
Other life
Net premiums earned by line of business:
Life Operations	14,507		44,514
Other life | Corporate and Other
Net premiums earned by line of business:
Life Operations	$14,507		$44,514
[1]	Corporate and Other includes other items of our revenue and expenditures that are not evaluated at the segment level for reporting purposes, as well as the Company's Run-Off Life Operations.
[2]	Other within the Insurance segment includes: excess and surplus, programs, surety, structured indemnity and certain discontinued lines. Other within the Reinsurance segment includes: whole account contracts, accident and health and other lines.

Segment_Information_Narrative_

Segment Information - Narrative (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
	segments
Segment Reporting Information [Line Items]
Number of segments	2
Net results from structured products	$5,025	[1]	$7,953	[2]
Total P&C
Segment Reporting Information [Line Items]
Net results from structured products	5,025	[1]	7,953	[2]
Net investment income | Total P&C
Segment Reporting Information [Line Items]
Net results from structured products	15,100		18,800
Interest expense | Total P&C
Segment Reporting Information [Line Items]
Net results from structured products	($10,000)		($10,800)
Alternative funds
Segment Reporting Information [Line Items]
Alternative investments, timelag for reporting	1 month
Operating affiliates
Segment Reporting Information [Line Items]
Alternative investments, timelag for reporting	3 months
[1]	The net results from P&C structured products include net investment income and interest expense of $15.1 million and $10.0 million, respectively.
[2]	The net results from P&C structured products include net investment income and interest expense of $18.8 million and $10.8 million, respectively.

Investments_Cost_amortized_cos

Investments - Cost (amortized cost for fixed maturities and short-term investments), fair value, gross unrealized gains, gross unrealized (losses), and OTTI recorded in AOCI (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, unless otherwise specified
AFS securities
Amortized cost of fixed maturities	$27,370,101		$27,728,771
Fixed maturities, at fair value	29,110,400		29,359,034
Gross Unrealized Losses Non-credit related OTTI	-66,784	[1]	-76,720	[1]
Short-term investments, amortized cost	169,903		257,221
Short-term investments, at fair value	168,862		256,727
Cost of equity securities	665,682		763,833
Equity securities, at fair value	783,471		868,292
Available for sale securities, Cost or amortized cost	28,205,686		28,749,825
Available for sale securities, Gross unrealized gains	2,062,326		1,947,804
Available for sale securities, Gross unrealized losses	-205,279		-213,576
Total investments available for sale	30,062,733		30,484,053
Trading securities
Amortized cost of fixed maturities, trading	138,647		1,180
Fixed maturities, trading at fair value	139,377		1,171
Excluding Life Funds Withheld Assets
AFS securities
Amortized cost of fixed maturities	23,579,612		23,427,432
Gross unrealized gains on Fixed maturities	1,001,956		936,840
Gross unrealized losses on Fixed maturities	-189,147		-186,803
Fixed maturities, at fair value	24,392,421		24,177,469
Gross Unrealized Losses Non-credit related OTTI	-66,784	[1]	-76,720	[1]
Short-term investments, amortized cost	169,903		257,221
Short-term investments, gross unrealized gains	149		49
Short-term investments, gross unrealized losses	-1,190		-543
Short-term investments, at fair value	168,862		256,727
Cost of equity securities	665,682		763,833
Equity securities, gross unrealized gains	132,731		130,689
Equity securities, gross unrealized losses	-14,942		-26,230
Equity securities, at fair value	783,471		868,292
Available for sale securities, Cost or amortized cost	24,415,197		24,448,486
Available for sale securities, Gross unrealized gains	1,134,836		1,067,578
Available for sale securities, Gross unrealized losses	-205,279		-213,576
Total investments available for sale	25,344,754		25,302,488
Excluding Life Funds Withheld Assets | U.S. Government and Government - Related/Supported
AFS securities
Amortized cost of fixed maturities	3,299,458		2,100,851
Gross unrealized gains on Fixed maturities	87,025		77,889
Gross unrealized losses on Fixed maturities	-8,141		-6,787
Fixed maturities, at fair value	3,378,342		2,171,953
Gross Unrealized Losses Non-credit related OTTI	0	[1]	0	[1]
Excluding Life Funds Withheld Assets | Corporate
AFS securities
Amortized cost of fixed maturities	7,806,607	[2]	8,462,130	[3]
Gross unrealized gains on Fixed maturities	398,357	[2]	365,805	[3]
Gross unrealized losses on Fixed maturities	-50,326	[2]	-49,562	[3]
Fixed maturities, at fair value	8,154,638	[2]	8,778,373	[3]
Gross Unrealized Losses Non-credit related OTTI	-3,309	[1],[2]	-3,309	[1],[3]
Excluding Life Funds Withheld Assets | RMBS - Agency
AFS securities
Amortized cost of fixed maturities	3,585,638		3,625,171
Gross unrealized gains on Fixed maturities	131,468		114,188
Gross unrealized losses on Fixed maturities	-5,772		-10,783
Fixed maturities, at fair value	3,711,334		3,728,576
Gross Unrealized Losses Non-credit related OTTI	0	[1]	0	[1]
Excluding Life Funds Withheld Assets | RMBS - Non-Agency
AFS securities
Amortized cost of fixed maturities	368,317		404,398
Gross unrealized gains on Fixed maturities	29,770		41,108
Gross unrealized losses on Fixed maturities	-17,952		-18,155
Fixed maturities, at fair value	380,135		427,351
Gross Unrealized Losses Non-credit related OTTI	-58,364	[1]	-67,918	[1]
Excluding Life Funds Withheld Assets | Commercial mortgage-backed securities
AFS securities
Amortized cost of fixed maturities	1,010,518		1,033,819
Gross unrealized gains on Fixed maturities	25,603		23,987
Gross unrealized losses on Fixed maturities	-3,401		-5,262
Fixed maturities, at fair value	1,032,720		1,052,544
Gross Unrealized Losses Non-credit related OTTI	-1,801	[1]	-2,033	[1]
Excluding Life Funds Withheld Assets | Collateralized debt obligations
AFS securities
Amortized cost of fixed maturities	520,929		717,544
Gross unrealized gains on Fixed maturities	1,675		1,659
Gross unrealized losses on Fixed maturities	-21,630		-27,169
Fixed maturities, at fair value	500,974		692,034
Gross Unrealized Losses Non-credit related OTTI	-1,648	[1]	-1,663	[1]
Excluding Life Funds Withheld Assets | Other asset-backed securities
AFS securities
Amortized cost of fixed maturities	1,134,928		1,028,528
Gross unrealized gains on Fixed maturities	41,386		42,810
Gross unrealized losses on Fixed maturities	-8,947		-6,045
Fixed maturities, at fair value	1,167,367		1,065,293
Gross Unrealized Losses Non-credit related OTTI	-1,662	[1]	-1,797	[1]
Excluding Life Funds Withheld Assets | US States and political subdivisions of the States
AFS securities
Amortized cost of fixed maturities	1,842,561		1,892,566
Gross unrealized gains on Fixed maturities	131,843		129,910
Gross unrealized losses on Fixed maturities	-1,264		-1,204
Fixed maturities, at fair value	1,973,140		2,021,272
Gross Unrealized Losses Non-credit related OTTI	0	[1]	0	[1]
Excluding Life Funds Withheld Assets | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
AFS securities
Amortized cost of fixed maturities	4,010,656		4,162,425
Gross unrealized gains on Fixed maturities	154,829		139,484
Gross unrealized losses on Fixed maturities	-71,714		-61,836
Fixed maturities, at fair value	4,093,771		4,240,073
Gross Unrealized Losses Non-credit related OTTI	0	[1]	0	[1]
Life Funds Withheld Assets
AFS securities
Amortized cost of fixed maturities	3,790,489		4,301,339
Gross unrealized gains on Fixed maturities	927,490		880,226
Gross unrealized losses on Fixed maturities	0		0
Fixed maturities, at fair value	4,717,979		5,181,565
Gross Unrealized Losses Non-credit related OTTI	0	[1]	0	[1]
Trading securities
Amortized cost of fixed maturities, trading	138,647		1,180
Fixed maturities, trading at fair value	139,377		1,171
Life Funds Withheld Assets | U.S. Government and Government - Related/Supported
AFS securities
Amortized cost of fixed maturities	13,163		14,866
Gross unrealized gains on Fixed maturities	4,450		3,858
Gross unrealized losses on Fixed maturities	0		0
Fixed maturities, at fair value	17,613		18,724
Gross Unrealized Losses Non-credit related OTTI	0	[1]	0	[1]
Life Funds Withheld Assets | Corporate
AFS securities
Amortized cost of fixed maturities	2,277,295	[2]	2,407,849	[3]
Gross unrealized gains on Fixed maturities	468,931	[2]	410,131	[3]
Gross unrealized losses on Fixed maturities	0	[2]	0	[3]
Fixed maturities, at fair value	2,746,226	[2]	2,817,980	[3]
Gross Unrealized Losses Non-credit related OTTI	0	[1],[2]	0	[1]
Trading securities
Amortized cost of fixed maturities, trading	136,681		1,180
Fixed maturities, trading at fair value	137,438		1,171
Life Funds Withheld Assets | RMBS - Agency
AFS securities
Amortized cost of fixed maturities	1,641		3,301
Gross unrealized gains on Fixed maturities	489		481
Gross unrealized losses on Fixed maturities	0		0
Fixed maturities, at fair value	2,130		3,782
Gross Unrealized Losses Non-credit related OTTI	0	[1]	0	[1]
Life Funds Withheld Assets | RMBS - Non-Agency
AFS securities
Amortized cost of fixed maturities	32,880		71,075
Gross unrealized gains on Fixed maturities	5,928		14,260
Gross unrealized losses on Fixed maturities	0		0
Fixed maturities, at fair value	38,808		85,335
Gross Unrealized Losses Non-credit related OTTI	0	[1]	0	[1]
Life Funds Withheld Assets | Commercial mortgage-backed securities
AFS securities
Amortized cost of fixed maturities	131,830		168,886
Gross unrealized gains on Fixed maturities	27,427		24,281
Gross unrealized losses on Fixed maturities	0		0
Fixed maturities, at fair value	159,257		193,167
Gross Unrealized Losses Non-credit related OTTI	0	[1]	0	[1]
Life Funds Withheld Assets | Other asset-backed securities
AFS securities
Amortized cost of fixed maturities	209,714		238,168
Gross unrealized gains on Fixed maturities	34,426		35,373
Gross unrealized losses on Fixed maturities	0		0
Fixed maturities, at fair value	244,140		273,541
Gross Unrealized Losses Non-credit related OTTI	0	[1]	0	[1]
Trading securities
Amortized cost of fixed maturities, trading	1,966
Fixed maturities, trading at fair value	1,939
Life Funds Withheld Assets | Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
AFS securities
Amortized cost of fixed maturities	1,123,966		1,397,194
Gross unrealized gains on Fixed maturities	385,839		391,842
Gross unrealized losses on Fixed maturities	0		0
Fixed maturities, at fair value	1,509,805		1,789,036
Gross Unrealized Losses Non-credit related OTTI	$0	[1]	$0	[1]
[1]	Represents the non-credit component of OTTI losses, adjusted for subsequent sales of securities. It does not include the change in fair value subsequent to the date an impairment was recorded.
[2]	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes have a fair value of $74.8 million and an amortized cost of $63.8 million. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.
[3]	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes have a fair value of $79.9 million and an amortized cost of $68.4 million. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.

Investments_Contractual_maturi

Investments - Contractual maturities of available for sale securities (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Fixed Maturities - AFS
Amortized cost of fixed maturities	$27,370,101	$27,728,771
Fixed maturities, at fair value	29,110,400	29,359,034
Trading Securities, Debt, Amortized Cost	138,647	1,180
Trading Securities Debt Maturities And Short Term Investments	139,377	1,171
Excluding Life Funds Withheld Assets
Fixed Maturities - AFS
Due less than one year, amortized cost	1,770,647	1,972,224
Due less than one year, fair value	1,781,224	1,980,429
Due after 1 through 5 years, amortized cost	9,698,659	8,919,037
Due after 1 through 5 years, fair value	9,923,517	9,113,651
Due after 5 through 10 years, amortized cost	4,049,907	4,232,396
Due after 5 through 10 years, fair value	4,226,001	4,412,569
Due after 10 years, amortized cost	1,440,069	1,494,315
Due after 10 years, fair value	1,669,149	1,705,022
Subtotal - amortized cost	16,959,282	16,617,972
Subtotal - fair value	17,599,891	17,211,671
Mortgage and asset backed securities - amortized cost	6,620,330	6,809,460
Mortgage and asset backed securities - fair value	6,792,530	6,965,798
Amortized cost of fixed maturities	23,579,612	23,427,432
Fixed maturities, at fair value	24,392,421	24,177,469
Excluding Life Funds Withheld Assets | RMBS - Agency
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	3,585,638	3,625,171
Mortgage and asset backed securities - fair value	3,711,334	3,728,576
Amortized cost of fixed maturities	3,585,638	3,625,171
Fixed maturities, at fair value	3,711,334	3,728,576
Excluding Life Funds Withheld Assets | RMBS - Non-Agency
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	368,317	404,398
Mortgage and asset backed securities - fair value	380,135	427,351
Amortized cost of fixed maturities	368,317	404,398
Fixed maturities, at fair value	380,135	427,351
Excluding Life Funds Withheld Assets | Commercial mortgage-backed securities
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	1,010,518	1,033,819
Mortgage and asset backed securities - fair value	1,032,720	1,052,544
Amortized cost of fixed maturities	1,010,518	1,033,819
Fixed maturities, at fair value	1,032,720	1,052,544
Excluding Life Funds Withheld Assets | Collateralized debt obligations
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	520,929	717,544
Mortgage and asset backed securities - fair value	500,974	692,034
Amortized cost of fixed maturities	520,929	717,544
Fixed maturities, at fair value	500,974	692,034
Excluding Life Funds Withheld Assets | Other asset-backed securities
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	1,134,928	1,028,528
Mortgage and asset backed securities - fair value	1,167,367	1,065,293
Amortized cost of fixed maturities	1,134,928	1,028,528
Fixed maturities, at fair value	1,167,367	1,065,293
Life Funds Withheld Assets
Fixed Maturities - AFS
Due less than one year, amortized cost	97,637	117,048
Due less than one year, fair value	107,530	125,326
Due after 1 through 5 years, amortized cost	626,869	638,526
Due after 1 through 5 years, fair value	676,507	685,787
Due after 5 through 10 years, amortized cost	798,923	1,004,698
Due after 5 through 10 years, fair value	933,986	1,165,348
Due after 10 years, amortized cost	1,890,995	2,059,637
Due after 10 years, fair value	2,555,621	2,649,279
Subtotal - amortized cost	3,414,424	3,819,909
Subtotal - fair value	4,273,644	4,625,740
Mortgage and asset backed securities - amortized cost	376,065	481,430
Mortgage and asset backed securities - fair value	444,335	555,825
Amortized cost of fixed maturities	3,790,489	4,301,339
Fixed maturities, at fair value	4,717,979	5,181,565
Trading Securities, Debt, Amortized Cost	138,647	1,180
Trading Securities Debt Maturities And Short Term Investments	139,377	1,171
Life Funds Withheld Assets | Cost
Fixed Maturities - AFS
Trading Securities Debt Maturities And Short Term Investments Within One Year	0	0
Trading Securities Debt Maturities After One Through Five Years	64,739	0
Trading Securities Debt Maturities After Five Through Ten Years	5,188	1,180
Trading Securities Debt Maturities After Ten Years	66,754	0
Trading Securities Debt Maturities And Short Term Investments Fixed Maturities	136,681	1,180
Trading Securities Debt Maturities Without Single Maturity Date	1,966	0
Trading Securities, Debt, Amortized Cost	138,647	1,180
Life Funds Withheld Assets | Fair value
Fixed Maturities - AFS
Trading Securities Debt Maturities And Short Term Investments Within One Year	0	0
Trading Securities Debt Maturities After One Through Five Years	64,733	0
Trading Securities Debt Maturities After Five Through Ten Years	5,131	1,171
Trading Securities Debt Maturities After Ten Years	67,574	0
Trading Securities Debt Maturities And Short Term Investments Fixed Maturities	137,438	1,171
Trading Securities Debt Maturities Without Single Maturity Date	1,939	0
Trading Securities Debt Maturities And Short Term Investments	139,377	1,171
Life Funds Withheld Assets | RMBS - Agency
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	1,641	3,301
Mortgage and asset backed securities - fair value	2,130	3,782
Amortized cost of fixed maturities	1,641	3,301
Fixed maturities, at fair value	2,130	3,782
Life Funds Withheld Assets | RMBS - Non-Agency
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	32,880	71,075
Mortgage and asset backed securities - fair value	38,808	85,335
Amortized cost of fixed maturities	32,880	71,075
Fixed maturities, at fair value	38,808	85,335
Life Funds Withheld Assets | Commercial mortgage-backed securities
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	131,830	168,886
Mortgage and asset backed securities - fair value	159,257	193,167
Amortized cost of fixed maturities	131,830	168,886
Fixed maturities, at fair value	159,257	193,167
Life Funds Withheld Assets | Other asset-backed securities
Fixed Maturities - AFS
Mortgage and asset backed securities - amortized cost	209,714	238,168
Mortgage and asset backed securities - fair value	244,140	273,541
Amortized cost of fixed maturities	209,714	238,168
Fixed maturities, at fair value	244,140	273,541
Trading Securities, Debt, Amortized Cost	1,966
Trading Securities Debt Maturities And Short Term Investments	1,939
Life Funds Withheld Assets | Other asset-backed securities | Cost
Fixed Maturities - AFS
Trading Securities Debt Maturities Without Single Maturity Date	1,966	0
Life Funds Withheld Assets | Other asset-backed securities | Fair value
Fixed Maturities - AFS
Trading Securities Debt Maturities Without Single Maturity Date	$1,939	$0

Investments_Analysis_of_contin

Investments - Analysis of continual unrealized loss position (Details) (Excluding Life Funds Withheld Assets, USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Total fixed maturities and short-term investments AFS
Fixed maturities and short-term investments - AFS:
Less than 12 months Fair Value	$2,210,453	$2,896,210
Less than 12 months Gross Unrealized Losses	-93,830	-61,772
Equal to or greater than 12 months Fair Value	1,633,911	2,745,705
Equal to greater than 12 months Gross Unrealized Losses	-96,507	-125,574
U.S. Government and Government - Related/Supported
Fixed maturities and short-term investments - AFS:
Less than 12 months Fair Value	249,646	251,091
Less than 12 months Gross Unrealized Losses	-3,541	-1,196
Equal to or greater than 12 months Fair Value	143,891	342,890
Equal to greater than 12 months Gross Unrealized Losses	-4,619	-5,603
Corporate
Fixed maturities and short-term investments - AFS:
Less than 12 months Fair Value	688,725	1,337,470
Less than 12 months Gross Unrealized Losses	-40,874	-33,881
Equal to or greater than 12 months Fair Value	190,397	424,221
Equal to greater than 12 months Gross Unrealized Losses	-9,730	-15,754
RMBS - Agency
Fixed maturities and short-term investments - AFS:
Less than 12 months Fair Value	177,627	134,535
Less than 12 months Gross Unrealized Losses	-914	-220
Equal to or greater than 12 months Fair Value	279,354	512,652
Equal to greater than 12 months Gross Unrealized Losses	-4,858	-10,563
RMBS - Non-Agency
Fixed maturities and short-term investments - AFS:
Less than 12 months Fair Value	51,876	45,378
Less than 12 months Gross Unrealized Losses	-1,815	-1,358
Equal to or greater than 12 months Fair Value	188,932	202,700
Equal to greater than 12 months Gross Unrealized Losses	-16,137	-16,797
Commercial mortgage-backed securities
Fixed maturities and short-term investments - AFS:
Less than 12 months Fair Value	120,862	78,356
Less than 12 months Gross Unrealized Losses	-393	-385
Equal to or greater than 12 months Fair Value	109,324	169,065
Equal to greater than 12 months Gross Unrealized Losses	-3,008	-4,877
Collateralized debt obligations
Fixed maturities and short-term investments - AFS:
Less than 12 months Fair Value	92,517	249,803
Less than 12 months Gross Unrealized Losses	-294	-2,666
Equal to or greater than 12 months Fair Value	346,372	414,516
Equal to greater than 12 months Gross Unrealized Losses	-21,336	-24,503
Other asset-backed securities
Fixed maturities and short-term investments - AFS:
Less than 12 months Fair Value	92,193	143,044
Less than 12 months Gross Unrealized Losses	-6,219	-2,813
Equal to or greater than 12 months Fair Value	37,357	57,544
Equal to greater than 12 months Gross Unrealized Losses	-2,728	-3,232
US States and political subdivisions of the States
Fixed maturities and short-term investments - AFS:
Less than 12 months Fair Value	55,707	32,187
Less than 12 months Gross Unrealized Losses	-695	-210
Equal to or greater than 12 months Fair Value	15,310	63,695
Equal to greater than 12 months Gross Unrealized Losses	-569	-994
Non-U.S. Sovereign Government, Provincial, Supranational, and Government-Related/Supported
Fixed maturities and short-term investments - AFS:
Less than 12 months Fair Value	681,300	624,346
Less than 12 months Gross Unrealized Losses	-39,085	-19,043
Equal to or greater than 12 months Fair Value	322,974	558,422
Equal to greater than 12 months Gross Unrealized Losses	-33,522	-43,251
Equities
Fixed maturities and short-term investments - AFS:
Less than 12 months Fair Value	119,625	191,193
Less than 12 months Gross Unrealized Losses	-14,942	-26,230
Equal to or greater than 12 months Fair Value	0	0
Equal to greater than 12 months Gross Unrealized Losses	$0	$0

Investments_Analysis_of_net_re

Investments - Analysis of net realized gains (losses) and the change in unrealized (losses) gains on investments (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Net realized gains (losses): [Abstract]
Net realized gains (losses) on investments	$52,891	$19,229
Excluding Life Funds Withheld Assets
Net realized gains (losses): [Abstract]
Gross realized gains	62,300	51,213
Gross realized losses on investments sold	-47,122	-28,257
OTTI on investments, net of amounts transferred to other comprehensive income	-10,576	-3,727
Net realized gains (losses) on investments	4,602	19,229
Life Funds Withheld Assets
Net realized gains (losses): [Abstract]
Gross realized gains	53,128	0
Gross realized losses on investments sold	-390	0
OTTI on investments, net of amounts transferred to other comprehensive income	-5,209	0
Net unrealized gains (losses) on investments, trading securities	760	0
Net realized gains (losses) on investments	$48,289	$0

Investments_Credit_loss_impair

Investments - Credit loss impairments on fixed income securities (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Balance, beginning of period	$131,942	$174,805
Credit loss impairment recognized in the current period on securities not previously impaired	7,560	12
Credit loss impairments previously recognized on securities which matured, paid down, prepaid or were sold during the period	-28,539	-3,348
Additional credit loss impairments recognized in the current period on securities previously impaired	141	2,261
Accretion of credit loss impairments previously recognized due to an increase in cash flows expected to be collected	-2,646	-2,347
Balance, end of period	$108,458	$171,383

Investments_Narrative_Details

Investments - Narrative (Details) (USD $)	3 Months Ended			0 Months Ended
	Mar. 31, 2015		Mar. 31, 2014	1-May-14	Dec. 31, 2014
	positions
Schedule of Available-for-sale Securities [Line Items]
Change in adjustments related to future policy benefit reserves, net of tax	($60,356,000)		$34,004,000
Fixed maturities, at fair value	29,110,400,000				29,359,034,000
Amortized cost of fixed maturities	27,370,101,000				27,728,771,000
Percentage of Fixed Income Investment portfolio invested in below investment grade or not rated	2.80%				3.00%
Percentage of Gross Unrealized losses in Fixed income securities portfolio related to securities below investment grade or not rated	23.10%				24.90%
Available for sale securities, Gross unrealized losses	205,279,000				213,576,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	1,347
Available-for-sale Securities, Qualitative Disclosure, Number of Positions	7,586
Pledged Assets Separately Reported, Other Debt Securities Available-for-sale or Held-for-investment	15,400,000,000				15,200,000,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold	28,539,000		3,348,000
Corporate
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	7,600,000
Medium term notes
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, at fair value	74,800,000				79,900,000
Amortized cost of fixed maturities	63,800,000				68,400,000
Structured Credit Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable Securities	6,100,000
Marketable Securities Unrealized Loss Other Than Temporary Impairments Amount	9,000,000
Impaired Investment Cumulative Fair Value Decline Percentage Amortized Cost	50.00%
RMBS - Non-Agency
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	100,000
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold	27,300,000		2,700,000
Foreign Currency Adjustments [Member]
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	2,600,000
Equities
Schedule of Available-for-sale Securities [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	300,000
XL Re Life (SAC) Ltd
Schedule of Available-for-sale Securities [Line Items]
Held To Maturity Securities Transferred Security Carrying Value				2,800,000,000
Unrealized gains on held to maturity investment portfolio at time of transfer to available for sale, net of tax				424,900,000
Fixed maturites held to maturity, gross unrealized losses				0
Unrealized gains (losses) on investments
Schedule of Available-for-sale Securities [Line Items]
Change in adjustments related to future policy benefit reserves, net of tax	-60,400,000
Unrealized gains (losses) on investments | XL Re Life (SAC) Ltd
Schedule of Available-for-sale Securities [Line Items]
Change in adjustments related to future policy benefit reserves, net of tax				440,500,000
Excluding Life Funds Withheld Assets
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, at fair value	24,392,421,000				24,177,469,000
Amortized cost of fixed maturities	23,579,612,000				23,427,432,000
Available for sale securities, Gross unrealized losses	205,279,000				213,576,000
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	10,576,000		3,727,000
Excluding Life Funds Withheld Assets | Corporate
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, at fair value	8,154,638,000	[1]			8,778,373,000	[2]
Amortized cost of fixed maturities	7,806,607,000	[1]			8,462,130,000	[2]
Excluding Life Funds Withheld Assets | RMBS - Non-Agency
Schedule of Available-for-sale Securities [Line Items]
Fixed maturities, at fair value	380,135,000				427,351,000
Amortized cost of fixed maturities	368,317,000				404,398,000
Catlin Group Limited
Schedule of Available-for-sale Securities [Line Items]
Pledged Assets Separately Reported, Other Debt Securities Available-for-sale or Held-for-investment	$1,000,000,000
[1]	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes have a fair value of $74.8 million and an amortized cost of $63.8 million. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.
[2]	Included are certain medium term notes supported primarily by pools of European investment grade credit with varying degrees of leverage. The notes have a fair value of $79.9 million and an amortized cost of $68.4 million. These notes allow the investor to participate in cash flows of the underlying bonds including certain residual values, which could serve to either decrease or increase the ultimate values of these notes.

Derivative_Instruments_Gross_a

Derivative Instruments - Gross amounts of derivative fair values contained in the consolidated balance sheet (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, unless otherwise specified
Derivatives, Fair Value [Line Items]
Gross amounts recognized in balance sheet	$257,880		$136,659
Asset derivative fair value	257,293		135,963
Gross amounts recognized in balance sheet	122,235		31,184
Liability derivative fair value	121,648		30,488
Derivatives designated as hedging instruments
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	204,811		2,300,609
Gross amounts recognized in balance sheet	38,376	[1]	121,862	[1]
Liability derivative notional amount	204,811		302,211
Gross amounts recognized in balance sheet	26,505	[1]	2,936	[1]
Derivatives designated as hedging instruments | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	204,811		2,300,609
Gross amounts recognized in balance sheet	38,376	[1]	121,862	[1]
Liability derivative notional amount	204,811		302,211
Gross amounts recognized in balance sheet	26,505	[1]	2,936	[1]
Derivatives not designated as hedging instruments
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	2,770,578		592,791
Gross amounts recognized in balance sheet	219,504	[1]	14,797	[1]
Liability derivative notional amount	7,708,973		5,804,625
Gross amounts recognized in balance sheet	95,730	[1]	28,248	[1]
Derivatives not designated as hedging instruments | Investment related derivatives | Interest rate exposure
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	264,527		394,597
Gross amounts recognized in balance sheet	224	[1]	206	[1]
Liability derivative notional amount	13,033		20,782
Gross amounts recognized in balance sheet	65	[1]	51	[1]
Derivatives not designated as hedging instruments | Investment related derivatives | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	23,400		7,385
Gross amounts recognized in balance sheet	498	[1]	403	[1]
Liability derivative notional amount	190,368		288,376
Gross amounts recognized in balance sheet	7,709	[1]	4,724	[1]
Derivatives not designated as hedging instruments | Investment related derivatives | Credit exposure
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	2,408		2,408
Gross amounts recognized in balance sheet	205	[1]	165	[1]
Liability derivative notional amount	14,270		14,270
Gross amounts recognized in balance sheet	9,836	[1]	9,836	[1]
Derivatives not designated as hedging instruments | Investment related derivatives | Financial market exposure
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	33,362		46,145
Gross amounts recognized in balance sheet	513	[1]	360	[1]
Liability derivative notional amount	33,136		33,670
Gross amounts recognized in balance sheet	63	[1]	34	[1]
Derivatives not designated as hedging instruments | Other non-investment derivatives | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	2,304,633		0
Gross amounts recognized in balance sheet	205,083	[1]	0	[1]
Liability derivative notional amount	2,366,968		0
Gross amounts recognized in balance sheet	65,294	[1]	0	[1]
Derivatives not designated as hedging instruments | Other non-investment derivatives | Other Credit Derivatives [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	31,060		31,060
Gross amounts recognized in balance sheet	218		60
Liability derivative notional amount	0		0
Gross amounts recognized in balance sheet	0		0
Derivatives not designated as hedging instruments | Other non-investment derivatives | Guaranteed minimum income benefit contract
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	45,658		46,249
Gross amounts recognized in balance sheet	12,763	[1]	13,603	[1]
Liability derivative notional amount	45,658		46,249
Gross amounts recognized in balance sheet	12,763	[1]	13,603	[1]
Derivatives not designated as hedging instruments | Other non-investment derivatives | Modified coinsurance funds withheld contract
Derivatives, Fair Value [Line Items]
Derivative Asset, Notional Amount	65,530	[2]	64,947	[2]
Gross amounts recognized in balance sheet	0	[1],[2]	0	[1],[2]
Liability derivative notional amount	5,045,540	[2]	5,401,278	[2]
Gross amounts recognized in balance sheet	$0	[1],[2]	$0	[1],[2]
[1]	Derivative instruments in an asset or liability position are included within Other assets or Other liabilities, respectively, in the balance sheets on a net basis where the Company has both a legal right of offset and the intention to settle the contracts on a net basis.
[2]	The fair value movements in derivative assets and liabilities relating to modified coinsurance funds withheld contracts are included within the associated asset or liability at each period end on the face of the balance sheets. Notional amounts associated with reinsurance agreements under which the Company assumes reinsurance risk are recorded as asset derivative notional amounts. Notional amounts associated with the Life Retro Arrangements under which the Company cedes reinsurance risk are recorded as liability derivative notional amounts. Included in the liability derivative notional amount as of MarchB 31, 2015 is the cumulative net realized and unrealized loss on life retrocession embedded derivative of $654.6 million

Derivative_Instruments_Balance

Derivative Instruments - Balance sheet offsetting (Details) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Thousands, unless otherwise specified
Derivative assets:
Gross amounts recognized in balance sheet	$257,880		$136,659
Derivative Asset, Fair Value, Gross Liability	587	[1]	696	[1]
Net amounts in the balance sheet	257,293		135,963
Gross amounts not offset in the balance sheet - financial instruments	0		0
Gross amounts not offset in the balance sheet - cash collateral	183,675		78,580
Derivative Asset	73,618		57,383
Derivative liabilities:
Gross amounts recognized in balance sheet	122,235		31,184
Derivative Liability, Fair Value, Gross Asset	587	[1]	696	[1]
Net amounts in the balance sheet	121,648		30,488
Gross amounts not offset in the balance sheet - financial instruments	0		0
Gross amounts not offset in the balance sheet - cash collateral	0		0
Derivative Liability	$121,648		$30,488
[1]	Other assets and other liabilities include derivative instruments. The derivative balances included in each category are reported on a gross basis by level with a netting adjustment presented separately in the Collateral and Counterparty Netting column. The fair values of the individual derivative contracts are reported gross in their respective levels based on the fair value hierarchy. For further details regarding derivative fair values and associated collateral received or paid see Note 7, bDerivative Instruments,b to the Unaudited Consolidated Financial Statements.

Derivative_Instruments_Derivat

Derivative Instruments - Derivatives Designated As Fair Value Hedges (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	$0	$1,794
Derivatives designated as hedging instruments | Fair value hedges | Net realized and unrealized gains (losses) on derivative instruments
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income	0	-6,531
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	0	1,794
Derivatives designated as hedging instruments | Fair value hedges | Net realized and unrealized gains (losses) on derivative instruments | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income	0	0
Derivatives designated as hedging instruments | Fair value hedges | Net realized and unrealized gains (losses) on derivative instruments | Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income	0	-6,531
Derivatives designated as hedging instruments | Fair value hedges | Net realized and unrealized gains (losses) on derivative instruments | Fixed maturity investments
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income	$0	$8,325

Derivative_Instruments_Schedul

Derivative Instruments - Schedule of settlement of fair value hedges (Details) (Fair value hedges, Deposit liabilities, USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Fair value hedges | Deposit liabilities
Derivative [Line Items]
Cumulative reduction to interest expense	$97,705	$41,270
Remaining balance	$135,490	$191,925
Weighted average years remaining to maturity	22 years 8 months 12 days	22 years 2 months 12 days

Derivative_Instruments_Derivat1

Derivative Instruments - Derivative Instruments Designated as Hedges of the net Investment In a Foreign Operation - Summary (Details) (Derivatives designated as hedging instruments, USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Derivatives designated as hedging instruments
Derivative [Line Items]
Weighted average of U.S. dollar equivalent of foreign denominated net assets	$628,941		$2,687,455
Derivative gains (losses)	$66,770	[1]	$960	[1]
[1]	Derivative gains (losses) from derivative instruments designated as hedges of the net investment in a foreign operation are recorded in the cumulative translation adjustment account within AOCI for each period.

Derivative_Instruments_Net_Rea

Derivative Instruments - Net Realized and unrealized gains (losses) on Derivative Instruments (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Derivative [Line Items]
Amount of gain (loss) recognized in income from ineffective portion of fair value hedges	$0	$1,794
Net realized and unrealized gains (losses) on derivative instruments	16,521	1,810
Derivatives not designated as hedging instruments
Derivative [Line Items]
Total gain (loss) recognized in income from derivatives not designated as hedging instruments	16,521	16
Derivatives not designated as hedging instruments | Investment related derivatives
Derivative [Line Items]
Interest rate exposure	9,637	348
Foreign exchange exposure	-1,362	3,288
Credit exposure	82	-404
Financial market exposure	3,041	871
Derivatives not designated as hedging instruments | Financial operations derivatives
Derivative [Line Items]
Credit exposure	0	-4,800
Derivatives not designated as hedging instruments | Other non-investment derivatives
Derivative [Line Items]
Foreign exchange exposure	2,059	0
Credit exposure	1,346	0
Guaranteed minimum income benefit contract	0	1,624
Modified coinsurance funds withheld contract	1,718	-911
Life Funds Withheld Assets
Derivative [Line Items]
Net realized and unrealized gains (losses) on derivative instruments	($229,367)	$0

Derivative_Instruments_Compone

Derivative Instruments - Components of life retrocession embedded derivative (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Derivative [Line Items]
Net realized and unrealized gains (losses) on derivative instruments	$16,521	$1,810
Life Funds Withheld Assets
Derivative [Line Items]
Net realized and unrealized gains (losses) on life retrocession embedded derivative	-203,730	0
Net adjustments related to future policy benefit reserves, net of tax	-11,954
Net realized and unrealized gains (losses) on derivative instruments - Life Funds Withheld Assets	-13,683	0
Net realized and unrealized gains (losses) on derivative instruments	-229,367	0
Life Funds Withheld Assets | Interest Income [Member]
Derivative [Line Items]
Net realized and unrealized gains (losses) on life retrocession embedded derivative	-50,996	0
Life Funds Withheld Assets | Net realized and unrealized gains (losses) on derivative instruments
Derivative [Line Items]
Net realized and unrealized gains (losses) on life retrocession embedded derivative	-152,830	0
Life Funds Withheld Assets | Other Income [Member]
Derivative [Line Items]
Net realized and unrealized gains (losses) on life retrocession embedded derivative	96	0
Life Funds Withheld Assets | Unrealized gains (losses) on investments
Derivative [Line Items]
Net adjustments related to future policy benefit reserves, net of tax		$0

Derivative_Instruments_Summary

Derivative Instruments - Summary of contingent credit features (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Derivative [Line Items]
Collateral posted to counterparty	$0	$0
Contracts with downgrade provisions [Member]
Derivative [Line Items]
Aggregate fair value of derivative agreements with downgrade provisions in a net liability position	5,598	5,770
Collateral posted to counterparty	$0	$0

Derivative_Instruments_Narrati

Derivative Instruments - Narrative (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014
Derivative [Line Items]
Cumulative net realized and unrealized loss on life retrocession embedded derivative	($654,600,000)
Gross amounts recognized in balance sheet	257,880,000				136,659,000
Net realized and unrealized gains (losses) on derivative instruments	16,521,000		1,810,000
Gross amounts not offset in the balance sheet - cash collateral	183,675,000				78,580,000
Net results from structured products	5,025,000	[1]	7,953,000	[2]
Fair value hedges | Deposit liabilities
Derivative [Line Items]
Remaining balance	135,490,000		191,925,000
Structured Indemnity [Member] | Fair value hedges | Deposit liabilities
Derivative [Line Items]
Remaining balance	47,000,000
Structured Indemnity [Member] | Interest expense
Derivative [Line Items]
Net results from structured products	28,700,000
Derivatives not designated as hedging instruments
Derivative [Line Items]
Derivative Asset, Notional Amount	2,770,578,000				592,791,000
Gross amounts recognized in balance sheet	219,504,000	[3]			14,797,000	[3]
Other non-investment derivatives | Derivatives not designated as hedging instruments | Other Credit Derivatives [Member]
Derivative [Line Items]
Derivative Asset, Notional Amount	31,060,000				31,060,000
Gross amounts recognized in balance sheet	218,000				60,000
Net realized and unrealized gains (losses) on derivative instruments	$100,000
[1]	The net results from P&C structured products include net investment income and interest expense of $15.1 million and $10.0 million, respectively.
[2]	The net results from P&C structured products include net investment income and interest expense of $18.8 million and $10.8 million, respectively.
[3]	Derivative instruments in an asset or liability position are included within Other assets or Other liabilities, respectively, in the balance sheets on a net basis where the Company has both a legal right of offset and the intention to settle the contracts on a net basis.

Goodwill_and_Other_Intangible_1

Goodwill and Other Intangible Assets (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and intangible assets, net	$442,431	$447,952

Share_Capital_Options_valuatio

Share Capital - Options valuation assumptions (Details)	3 Months Ended
	Mar. 31, 2015
Stockholders' Equity Note [Abstract]
Dividend yield	2.00%
Risk free interest rate	1.70%
Volatility	21.90%
Expected lives	6 years

Share_Capital_Narrative_Detail

Share Capital - Narrative (Details) (USD $)	3 Months Ended
Share data in Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015	Feb. 21, 2014
2014 Repurchase Authorization
Shareholders Equity Disclosure [Line Items]
Stock Repurchase Program, Authorized Amount		$1,000,000,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	267,600,000
Stock options
Shareholders Equity Disclosure [Line Items]
Weighted Average Grant Date Fair Value Per Stock Option	$6.57
Number of Stock Options Granted During the Period	1.3
Restricted stock units
Shareholders Equity Disclosure [Line Items]
Number of Awards Granted During the Period	1.5
Aggregate Grant Date Fair Value of Award	$55,100,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Minimum [Member]
Shareholders Equity Disclosure [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Maximum [Member]
Shareholders Equity Disclosure [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years

Notes_Payable_and_Debt_and_Fin2

Notes Payable and Debt and Financing Arrangements (Details) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015		Mar. 30, 2015	Dec. 31, 2014
	Credit_Facilities
Line of Credit Facility [Line Items]
Percentage Ownership Of XLIT Ltd.	100.00%
Number Of Available Letter Of Credit	8
Revolving credit facility
Line of Credit Facility [Line Items]
Available letter of credit facilities - commitments	1,000,000,000	[1],[2]		$1,000,000,000	[1],[2]
Letter of credit facilities
Line of Credit Facility [Line Items]
Available letter of credit facilities - commitments	3,575,000,000	[1],[3]		3,575,000,000	[1],[3]
Available letter of credit facilities - in use	1,743,230,000	[1]		1,790,561,000	[1]
Collateralized by certain assets of the Companybs investment portfolio	65.70%	[1]		66.20%	[1]
November 2013 unsecured credit agreement
Line of Credit Facility [Line Items]
Line Of Credit Facility Optional Increased Capacity	2,000,000,000
Two Thousand Thirteen Citi Agreements [Member] | Revolving credit facility
Line of Credit Facility [Line Items]
Available letter of credit facilities - commitments	575,000,000
Two Thousand Thirteen Citi Agreements [Member] | Letter of credit facilities
Line of Credit Facility [Line Items]
Available letter of credit facilities - in use	575,000,000
Syndicated Credit Agreements [Member]
Line of Credit Facility [Line Items]
Line Of Credit Facility Optional Increased Capacity	500,000,000
XL Cayman | 4.45% subordinated notes due 2025 | Subordinated notes
Line of Credit Facility [Line Items]
Face value of issued notes			500,000,000
Debt interest rate (percent)			4.45%
Debt issue price, as a percentage of face value			99.63%
Net proceeds on issuance of debt			492,200,000
Debt issuance cost			5,900,000
XL Cayman | 5.5% subordinated notes due 2045 | Subordinated notes
Line of Credit Facility [Line Items]
Face value of issued notes			500,000,000
Debt interest rate (percent)			5.50%
Debt issue price, as a percentage of face value			99.12%
Net proceeds on issuance of debt			488,400,000
Debt issuance cost			$7,200,000
[1]	As of MarchB 31, 2015 and DecemberB 31, 2014, there were eight available letter of credit facilities.
[2]	As of MarchB 31, 2015 and DecemberB 31, 2014, the $1 billion of revolving credit available under the November 2013 unsecured credit agreements, which currently provide an aggregate amount for issuance of letters of credit and revolving credit loans up to $2 billion, was unutilized. The credit agreements entered into with Citicorp USA, Inc. in May through November 2013 (the "Citi Agreements") provide for issuance of letters of credit and revolving credit loans up to an aggregate amount of $575.0 million. As of MarchB 31, 2015, $575.0 million of letters of credit were issued under these agreements and therefore such amount is not included in this line.
[3]	ovember 2013 credit agreements, which currently provide an aggregate amount of outstanding letters of credit and revolving credit loans of up to $2 billion. The Company has the option to increase the size of the facilities under these agreements by an additional $500 million across such facilities. The Company also has the option to increase the maximum amount of the letters of credit and revolving credit loans available under the 2013 credit agreements with Citicorp USA, Inc. with the lender's and issuing lender's consent.

Related_Party_Transactions_Sch

Related Party Transactions - Schedule of related party transactions activity (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
	management_company		management_company
Related Party Transaction [Line Items]
Reported net premiums written	$1,851,249	$1,995,851
Net losses and loss expenses incurred	769,827	831,505
Reported acquisition costs	153,696	199,414
Number of investment management companies	6		5
Investment manager affiliates
Related Party Transaction [Line Items]
Reported net premiums written	27,076	16,240
Net losses and loss expenses incurred	9,100	6,138
Reported acquisition costs	$9,012	$7,629

Variable_Interest_Entities_Det

Variable Interest Entities (Details) (Variable Interest Entity, Primary Beneficiary [Member], USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Variable Interest Entity [Line Items]
Noncontrolling Interest in Variable Interest Entity	$58.80	$58.40
Variable Interest Entity, Consolidated, Carrying Amount, Assets	141.3	139.9
New Ocean Capital Management Ltd [Member]
Variable Interest Entity [Line Items]
Noncontrolling Interest in Variable Interest Entity	$0.20	$0.20

Computation_of_Earnings_Per_Or2

Computation of Earnings Per Ordinary Share and Ordinary Share Equivalent - Computation of Basic and Diluted Earnings Per Share (Details) (USD $)	3 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Basic earnings per ordinary share & ordinary share equivalents outstanding:
Net income (loss) attributable to ordinary shareholders	$36,281	$255,717
Weighted average ordinary shares outstanding - basic	255,724	276,337
Basic earnings per ordinary share & ordinary share equivalents outstanding	$0.14	$0.93
Diluted earnings per ordinary share & ordinary share equivalents outstanding:
Impact of share-based compensation and certain conversion features	4,980	4,121
Weighted average ordinary shares outstanding - diluted	260,704	280,458
Diluted earnings per ordinary share & ordinary share equivalents outstanding	$0.14	$0.91
Dividends per ordinary share	$0.16	$0.16

Computation_of_Earnings_Per_Or3

Computation of Earnings Per Ordinary Share and Ordinary Share Equivalent - Narrative (Details) (Share-based compensation plans)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Share-based compensation plans
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (shares)	5	6.1

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Guarantor Obligations [Line Items]
Aggregate exposure outstanding	$80,800,000
Total gross claim liability recorded	$0
Financial Guarantee Insurance Contracts Outstanding Weighted Average Contract Period	25 years	25 years 2 months 12 days
Financial Guarantee Related to Securities Including Some Issued By European Financials [Member]
Guarantor Obligations [Line Items]
Closing number of financial guarantee contracts	2

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Loss) - Changes in AOCI, net of tax (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	$1,484,458,000		$736,657,000
OCI before Reclassifications	287,646,000		259,319,000
Amounts reclassified from AOCI	-64,750,000		-19,119,000
Tax benefit (expense)	-2,184,000		-30,196,000
Comprehensive income (loss)	220,712,000		210,004,000
Ending balance, net of tax	1,705,170,000		946,661,000
AOCI Other Details [Abstract]
Change in adjustments related to future policy benefit reserves, net of tax	-60,356,000		34,004,000
Unrealized gains (losses) on investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	1,590,114,000	[1]	822,432,000
OCI before Reclassifications	254,267,000	[1]	265,250,000
Amounts reclassified from AOCI	-74,781,000	[1]	-22,638,000
Tax benefit (expense)	-5,805,000	[1]	-32,103,000
Comprehensive income (loss)	173,681,000	[1]	210,509,000
Ending balance, net of tax	1,763,795,000	[1]	1,032,941,000
AOCI Other Details [Abstract]
Change in adjustments related to future policy benefit reserves, net of tax	-60,400,000
Cumulative impact on value of future policy benefit reserve, end of period	384,800,000			445,100,000
OTTI losses recognized in AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	-76,047,000		-89,190,000
OCI before Reclassifications	0		0
Amounts reclassified from AOCI	9,936,000		3,409,000
Tax benefit (expense)	-78,000		-113,000
Comprehensive income (loss)	9,858,000		3,296,000
Ending balance, net of tax	-66,189,000		-85,894,000
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	-11,188,000		14,541,000
OCI before Reclassifications	32,404,000		-5,900,000
Amounts reclassified from AOCI	0		0
Tax benefit (expense)	3,699,000		2,020,000
Comprehensive income (loss)	36,103,000		-3,880,000
Ending balance, net of tax	24,915,000		10,661,000
Underfunded pension liability
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	-20,789,000		-13,239,000
OCI before Reclassifications	975,000		-31,000
Amounts reclassified from AOCI	0		0
Tax benefit (expense)	0		0
Comprehensive income (loss)	975,000		-31,000
Ending balance, net of tax	-19,814,000		-13,270,000
Cash flow hedge
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, net of tax	2,368,000		2,113,000
OCI before Reclassifications	0		0
Amounts reclassified from AOCI	95,000		110,000
Tax benefit (expense)	0		0
Comprehensive income (loss)	95,000		110,000
Ending balance, net of tax	$2,463,000		$2,223,000
[1]	Included in these amounts is the impact of Shadow Adjustments. As of December 31, 2014 the cumulative impact of these adjustments was $445.1 million. During the three months ended March 31, 2015, net movements of $(60.4) million were recorded, resulting in a total cumulative net impact of Shadow Adjustments on future policy benefit reserves of $384.8 million as of MarchB 31, 2015.

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Income (Loss) - Details About AOCI Components (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	($64,750)		($19,119)
Operating expenses	325,656		310,424
Tax benefit (expense)	-24,218		-34,321
Unrealized gains (losses) on investments
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	-74,781	[1]	-22,638
OTTI losses recognized in AOCI
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	9,936		3,409
Underfunded pension liability
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	0		0
Cash flow hedge
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	95		110
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	-64,750		-19,119
Tax benefit (expense)	84		340
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	-64,666		-18,779
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized gains (losses) on investments
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments sold	-78,551		-24,914
OTTI on investments	15,724		2,276
Total before tax	-74,781		-22,638
Tax benefit (expense)	87		453
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	-74,694		-22,185
Reclassification out of Accumulated Other Comprehensive Income [Member] | OTTI losses recognized in AOCI
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments sold	9,875		1,958
OTTI on investments	61		1,451
Total before tax	9,936		3,409
Tax benefit (expense)	-3		-113
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	9,933		3,296
Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash flow hedge
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	95		110
Tax benefit (expense)	0		0
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	95		110
Life Funds Withheld Assets
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net realized gains (losses) on investments sold	52,738		0
OTTI on investments	-5,209		0
Change in adjustments related to future policy benefit reserves, net of tax	-11,954
Life Funds Withheld Assets | Unrealized gains (losses) on investments
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Change in adjustments related to future policy benefit reserves, net of tax			0
Life Funds Withheld Assets | Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized gains (losses) on investments
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Change in adjustments related to future policy benefit reserves, net of tax	($11,954)		$0
[1]	Included in these amounts is the impact of Shadow Adjustments. As of December 31, 2014 the cumulative impact of these adjustments was $445.1 million. During the three months ended March 31, 2015, net movements of $(60.4) million were recorded, resulting in a total cumulative net impact of Shadow Adjustments on future policy benefit reserves of $384.8 million as of MarchB 31, 2015.