Significant Transactions	12 Months Ended
Dec. 31, 2013
Significant Transactions [Abstract]
Significant Transactions	Significant Transactions Sale of Essentia Insurance Company Effective January 1, 2013, OneBeacon completed the sale of Essentia Insurance Company (“Essentia”), an indirect wholly-owned subsidiary which wrote the collector cars and boats business, to Markel Corporation. Concurrently therewith, OneBeacon and Hagerty Insurance Agency (“Hagerty”) terminated their underwriting arrangement with respect to the collector cars and boats business. OneBeacon recognized a pre-tax gain on sale of $23.0 million ($15.0 million after tax) in the first quarter of 2013. The business associated with this agreement generated net written premiums of $179.7 million and $166.6 million for December 31, 2012 and 2011, or 8.0% of White Mountains’ net written premiums for both periods. Formation of HG Global and BAM In 2012, White Mountains capitalized HG Global with $594.5 million to fund BAM, a newly formed mutual municipal bond insurer. As of December 31, 2013, White Mountains owned 97.3% of HG Global’s preferred equity and 88.7% of its common equity. HG Global, together with its subsidiaries, provided the initial capitalization of BAM through the purchase of $503.0 million of BAM Surplus Notes. HG Global provides first loss reinsurance protection for policies underwritten by BAM of up to 15% of par outstanding on a per policy basis through HG Re, which had statutory capital of $436.9 million and $412.0 million at December 31, 2013 and 2012. HG Re’s obligations to BAM are collateralized in trusts, and there is an aggregate loss limit that is equal to the total assets in the collateral trusts at any point in time. Sale of OneBeacon Runoff Business On October 17, 2012, one of OneBeacon’s indirect wholly-owned subsidiaries, OneBeacon Insurance Group LLC, entered into a definitive agreement (as amended, the “Runoff SPA”) with Trebuchet US Holdings, Inc. (“Trebuchet”), a wholly-owned subsidiary of Armour Group Holdings Limited (together with Trebuchet, “Armour”), to sell the Runoff Business (the “Runoff Transaction”). Pursuant to the terms of the Runoff SPA, at closing OneBeacon will transfer to Trebuchet all of the issued and outstanding shares of common stock of certain legal entities that will contain the assets, liabilities (including gross and ceded loss reserves) and capital supporting the Runoff Business as well as certain elements of the Runoff Business infrastructure, including staff and office space. The transaction is subject to regulatory approvals and is expected to close in mid-2014 (see Note 21). WM Solutions On October 15, 2013, WM Solutions acquired Empire Insurance Company (“Empire”), a runoff insurance subsidiary of Leucadia National Corporation. The transaction resulted in a gain of $7.3 million recorded in other revenue. In the first quarter of 2013, WM Solutions acquired Ashmere Insurance Company (“Ashmere”, formerly known as American Fuji Fire and Marine Insurance Company), an American International Group, Inc. (“AIG”) runoff subsidiary. The transaction resulted in a gain of $6.9 million recorded in other revenue. On December 3, 2012, WM Solutions acquired four runoff entities including Physicians Insurance Company of Ohio (“PICO”) and Citation Insurance Company (“Citation”) from PICO Holdings and two AIG runoff subsidiaries, Woodridge Insurance Company (“Woodridge”, formerly known as American General Indemnity Company) and Oakwood Insurance Company (“Oakwood”, formerly known as American General Property Insurance Company). The transactions resulted in a gain of $14.5 million recorded in other revenue. On December 30, 2011, WM Solutions acquired the runoff loss reserve portfolio of Old Lyme, a Bermuda-based reinsurer in runoff, for $6.0 million in cash and a purchase note for $2.1 million (see Note 6). The transaction resulted in a gain of $7.2 million recorded in other revenue. Sale of AutoOne On August 30, 2011, OneBeacon entered into a definitive agreement (the “Purchase Agreement”) to sell the AutoOne business to Interboro Holdings, Inc. (“Interboro”). On February 22, 2012, OneBeacon completed the sale of AutoOne to Interboro Holdings, Inc. (“Interboro”). OneBeacon formed AutoOne in 2001 to provide products and services to automobile assigned risk markets primarily in New York and New Jersey. OneBeacon transferred to the buyer AutoOne Insurance Company (“AOIC”) and AutoOne Select Insurance Company (“AOSIC”), which contained the assets, liabilities (including loss reserves and unearned premiums), and the capital of the AutoOne business, and transferred substantially all of the AutoOne infrastructure including systems and office space as well as certain staff. As a result of the sale, AutoOne is reported as discontinued operations (see Note 21). Sale of Esurance On October 7, 2011, White Mountains completed the sale of Esurance Insurance and AFI to The Allstate Corporation (“Allstate”) for $700.0 million in excess of tangible book value. White Mountains recorded a gain on the sale of $677.5 million in discontinued operations (see Note 21). The transaction is subject to a true-up of the estimated tangible book value of the entities sold through the date of closing and certain other contingencies (see Note 20).

Significant Transactions

Sale of Essentia Insurance Company

Effective January 1, 2013, OneBeacon completed the sale of Essentia Insurance Company (“Essentia”), an indirect wholly-owned subsidiary which wrote the collector cars and boats business, to Markel Corporation. Concurrently therewith, OneBeacon and Hagerty Insurance Agency (“Hagerty”) terminated their underwriting arrangement with respect to the collector cars and boats business. OneBeacon recognized a pre-tax gain on sale of $23.0 million ($15.0 million after tax) in the first quarter of 2013. The business associated with this agreement generated net written premiums of $179.7 million and $166.6 million for December 31, 2012 and 2011, or 8.0% of White Mountains’ net written premiums for both periods.

Formation of HG Global and BAM

In 2012, White Mountains capitalized HG Global with $594.5 million to fund BAM, a newly formed mutual municipal bond insurer. As of December 31, 2013, White Mountains owned 97.3% of HG Global’s preferred equity and 88.7% of its common equity. HG Global, together with its subsidiaries, provided the initial capitalization of BAM through the purchase of $503.0 million of BAM Surplus Notes. HG Global provides first loss reinsurance protection for policies underwritten by BAM of up to 15% of par outstanding on a per policy basis through HG Re, which had statutory capital of $436.9 million and $412.0 million at December 31, 2013 and 2012. HG Re’s obligations to BAM are collateralized in trusts, and there is an aggregate loss limit that is equal to the total assets in the collateral trusts at any point in time.

Sale of OneBeacon Runoff Business

On October 17, 2012, one of OneBeacon’s indirect wholly-owned subsidiaries, OneBeacon Insurance Group LLC, entered into a definitive agreement (as amended, the “Runoff SPA”) with Trebuchet US Holdings, Inc. (“Trebuchet”), a wholly-owned subsidiary of Armour Group Holdings Limited (together with Trebuchet, “Armour”), to sell the Runoff Business (the “Runoff Transaction”). Pursuant to the terms of the Runoff SPA, at closing OneBeacon will transfer to Trebuchet all of the issued and outstanding shares of common stock of certain legal entities that will contain the assets, liabilities (including gross and ceded loss reserves) and capital supporting the Runoff Business as well as certain elements of the Runoff Business infrastructure, including staff and office space. The transaction is subject to regulatory approvals and is expected to close in mid-2014 (see Note 21).

WM Solutions

On October 15, 2013, WM Solutions acquired Empire Insurance Company (“Empire”), a runoff insurance subsidiary of Leucadia National Corporation. The transaction resulted in a gain of $7.3 million recorded in other revenue.

In the first quarter of 2013, WM Solutions acquired Ashmere Insurance Company (“Ashmere”, formerly known as American Fuji Fire and Marine Insurance Company), an American International Group, Inc. (“AIG”) runoff subsidiary. The transaction resulted in a gain of $6.9 million recorded in other revenue.

On December 3, 2012, WM Solutions acquired four runoff entities including Physicians Insurance Company of Ohio (“PICO”) and Citation Insurance Company (“Citation”) from PICO Holdings and two AIG runoff subsidiaries, Woodridge Insurance Company (“Woodridge”, formerly known as American General Indemnity Company) and Oakwood Insurance Company (“Oakwood”, formerly known as American General Property Insurance Company). The transactions resulted in a gain of $14.5 million recorded in other revenue.

On December 30, 2011, WM Solutions acquired the runoff loss reserve portfolio of Old Lyme, a Bermuda-based reinsurer in runoff, for $6.0 million in cash and a purchase note for $2.1 million (see Note 6). The transaction resulted in a gain of $7.2 million recorded in other revenue.

Sale of AutoOne

On August 30, 2011, OneBeacon entered into a definitive agreement (the “Purchase Agreement”) to sell the AutoOne business to Interboro Holdings, Inc. (“Interboro”). On February 22, 2012, OneBeacon completed the sale of AutoOne to Interboro Holdings, Inc. (“Interboro”). OneBeacon formed AutoOne in 2001 to provide products and services to automobile assigned risk markets primarily in New York and New Jersey. OneBeacon transferred to the buyer AutoOne Insurance Company (“AOIC”) and AutoOne Select Insurance Company (“AOSIC”), which contained the assets, liabilities (including loss reserves and unearned premiums), and the capital of the AutoOne business, and transferred substantially all of the AutoOne infrastructure including systems and office space as well as certain staff. As a result of the sale, AutoOne is reported as discontinued operations (see Note 21).

Sale of Esurance

On October 7, 2011, White Mountains completed the sale of Esurance Insurance and AFI to The Allstate Corporation (“Allstate”) for $700.0 million in excess of tangible book value. White Mountains recorded a gain on the sale of $677.5 million in discontinued operations (see Note 21). The transaction is subject to a true-up of the estimated tangible book value of the entities sold through the date of closing and certain other contingencies (see Note 20).