Variable Interest Entities	12 Months Ended
Dec. 31, 2014
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. 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 16, “Derivative Instruments,” and Note 19(h), “Commitments and Contingencies – Financial Guarantee Exposures.” During the third quarter of 2013, the Company, along with other investors, formed a new Bermuda-based company, New Ocean Capital Management Limited (“New Ocean”), to act as an investment manager that focuses 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 current year. The equity interest attributable to third party investors in New Ocean recorded in the Company’s Consolidated Balance Sheets as "Non-controlling interest in equity of consolidated subsidiaries" was $0.2 million and $0.3 million at December 31, 2014 and December 31, 2013, respectively. During the fourth quarter of 2013, the Company, along with other investors, formed a new Bermuda-based investment company, New Ocean Focus Cat Fund Ltd. ("New Ocean FCFL"), which is considered a VIE under GAAP. During the year ended December 31, 2014, New Ocean FCFL invested in a special purpose 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. Most of Vector Re’s current underwriting activity relates to reinsurance business assumed from XL subsidiaries. Underwriting administration and claims services are provided to Vector Re by XL 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 Vector Re. Accordingly, included in the consolidated financial statements of the Company are New Ocean FCFL's and Vector Re's total net assets of $93.9 million and $46.5 million at December 31, 2014 and December 31, 2013, respectively. The Company’s share of revenue and net income in these VIEs was not material to the Company for the twelve months ended December 31, 2014. All inter-company transactions between XL entities have been eliminated in consolidation. The equity interest attributable to third party investors in New Ocean FCFL and Vector Re recorded in the Company’s Consolidated Balance Sheets as "Non-controlling interest in equity of consolidated subsidiaries" was $57.4 million and $6.9 million at December 31, 2014 and December 31, 2013, respectively. 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 invests in insurance-linked securities, with a current primary focus on catastrophe bonds. An additional investor joined New Ocean MVCFL in the fourth quarter of 2014, but the Company still holds a majority equity interest which is considered to be the controlling financial interest. Accordingly, included in the consolidated financial statements of the Company are New Ocean MVCFL's total net assets of $46.1 million at December 31, 2014. The Company's share of revenue and net income in New Ocean MVCFL was not material for the twelve months ended December 31, 2014. The equity interest attributable to the third party investor in New Ocean MVCFL recorded in the Company’s Consolidated Balance Sheets as "Non-controlling interest in equity of consolidated subsidiaries" was $1.0 million at December 31, 2014.

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. 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 16, “Derivative Instruments,” and Note 19(h), “Commitments and Contingencies – Financial Guarantee Exposures.”

During the third quarter of 2013, the Company, along with other investors, formed a new Bermuda-based company, New Ocean Capital Management Limited (“New Ocean”), to act as an investment manager that focuses 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 current year. The equity interest attributable to third party investors in New Ocean recorded in the Company’s Consolidated Balance Sheets as "Non-controlling interest in equity of consolidated subsidiaries" was $0.2 million and $0.3 million at December 31, 2014 and December 31, 2013, respectively.

During the fourth quarter of 2013, the Company, along with other investors, formed a new Bermuda-based investment company, New Ocean Focus Cat Fund Ltd. ("New Ocean FCFL"), which is considered a VIE under GAAP. During the year ended December 31, 2014, New Ocean FCFL invested in a special purpose 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. Most of Vector Re’s current underwriting activity relates to reinsurance business assumed from XL subsidiaries. Underwriting administration and claims services are provided to Vector Re by XL 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 Vector Re. Accordingly, included in the consolidated financial statements of the Company are New Ocean FCFL's and Vector Re's total net assets of $93.9 million and $46.5 million at December 31, 2014 and December 31, 2013, respectively. The Company’s share of revenue and net income in these VIEs was not material to the Company for the twelve months ended December 31, 2014. All inter-company transactions between XL entities have been eliminated in consolidation. The equity interest attributable to third party investors in New Ocean FCFL and Vector Re recorded in the Company’s Consolidated Balance Sheets as "Non-controlling interest in equity of consolidated subsidiaries" was $57.4 million and $6.9 million at December 31, 2014 and December 31, 2013, respectively.

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 invests in insurance-linked securities, with a current primary focus on catastrophe bonds. An additional investor joined New Ocean MVCFL in the fourth quarter of 2014, but the Company still holds a majority equity interest which is considered to be the controlling financial interest. Accordingly, included in the consolidated financial statements of the Company are New Ocean MVCFL's total net assets of $46.1 million at December 31, 2014. The Company's share of revenue and net income in New Ocean MVCFL was not material for the twelve months ended December 31, 2014. The equity interest attributable to the third party investor in New Ocean MVCFL recorded in the Company’s Consolidated Balance Sheets as "Non-controlling interest in equity of consolidated subsidiaries" was $1.0 million at December 31, 2014.