Significant Transactions	9 Months Ended
Sep. 30, 2014
Significant Transactions [Abstract]
Significant Transactions	Significant Transactions durchblicker.at In July 2014, White Mountains acquired 45% of the outstanding common shares of durchblicker.at, Austria's first independent price comparison portal for insurance, gas/electricity and financial services, for EUR 8.5 million (approximately $11.7 million based upon the foreign exchange spot rate at the date of acquisition). PassportCard In June 2014, White Mountains committed $21.0 million to fund a 50/50 joint venture with DavidShield Group (“DavidShield”) for the development, marketing and distribution of PassportCard travel insurance. The transaction is expected to close in the fourth quarter of 2014, subject to regulatory approvals. QuoteLab On March 14, 2014, White Mountains acquired 60% of the outstanding Class A common units of QuoteLab. As of September 30, 2014, White Mountains owned 58.4% of the equity of QuoteLab. QuoteLab is an advertising technology company that operates a transparent online advertising exchange that facilitates transactions between buyers and sellers of insurance media, including advertising inventory on QuoteLab’s owned and operated websites. White Mountains paid an initial purchase price of $28.1 million and will pay additional consideration to the sellers equal to 62.5% of the 2015 gross profit in excess of the 2013 gross profit. At acquisition, QuoteLab had total assets of $56.9 million, including $43.7 million of intangible assets, and total liabilities of $10.0 million. Wobi On February 19, 2014, White Mountains acquired 54% of the outstanding common shares of Wobi for NIS 14.4 million (approximately $4.1 million based upon the foreign exchange spot rate at the date of acquisition). In addition to the common shares, White Mountains also purchased NIS 12.7 million (approximately $3.6 million based upon the foreign exchange spot rate at the date of acquisition) of newly-issued convertible preferred shares of Wobi. Wobi is the only price comparison/aggregation business in Israel, with an insurance carrier panel that represents 85% of the premiums written in the Israeli insurance market. Wobi sells four lines of business, primarily personal auto, and operates as an agency, charging upfront commissions on all policy sales. As of September 30, 2014, on a fully converted basis, White Mountains owned 60.7% of Wobi. At acquisition, Wobi had total assets of $13.4 million, including $8.4 million of intangible assets, and total liabilities of $0.7 million. Star & Shield On January 31, 2014, White Mountains acquired certain assets and liabilities of Star & Shield Holdings LLC, including SSRM, the attorney-in-fact for SSIE, for a purchase price of $1.8 million. White Mountains also purchased $17.0 million of surplus notes issued by SSIE. Principal and interest on the surplus notes are payable to White Mountains only with approval from the Florida Office of Insurance Regulation. SSIE is a Florida-domiciled reciprocal insurance exchange providing private passenger auto insurance to the public safety community and their families. SSIE is a variable interest entity (“VIE”). As a result of SSRM’s role as the attorney-in-fact to SSIE and the investment in SSIE’s surplus notes, White Mountains is required to consolidate SSIE. At September 30, 2014, consolidated amounts included total assets of $11.8 million and total liabilities of $22.8 million of SSIE. For the three and nine months ended September 30, 2014, SSIE had pre-tax losses of $1.4 million and $11.1 million that were recorded in net loss attributable to non-controlling interests. WM Solutions In the first quarter of 2014, WM Solutions completed the shell sale of Citation Insurance Company, which resulted in a gain of $0.7 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. 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 car and boat business, to Markel Corporation. Concurrently, OneBeacon and Hagerty Insurance Agency (“Hagerty”) terminated their underwriting arrangement with respect to the collector car and boat business. OneBeacon recognized a pre-tax gain on sale of $23.0 million ($15.0 million after tax) in the first quarter of 2013. 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. Pursuant to the terms of the agreement, 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 approval. As a result of the agreement, the OneBeacon Runoff Business is reported as discontinued operations (see Note 15). Common Shares Repurchased and Retired During the past several years, White Mountains's board of directors has authorized the Company to repurchase its common shares, from time to time, subject to market conditions. The repurchase authorizations do not have a stated expiration date. As of September 30, 2014, White Mountains may repurchase an additional 382,118 shares under these board authorizations. In addition, from time to time White Mountains has also repurchased its common shares through tender offers that were separately approved by its board of directors. During the three months ended September 30, 2014, the Company repurchased 122,264 common shares for $76.5 million at an average share price of $626.13, all of which were repurchased under the board authorization. During the nine months ended September 30, 2014, the Company repurchased 173,853 common shares for $106.9 million at an average share price of $614.78, which was comprised of 163,378 common shares repurchased under the board authorization and 10,475 common shares repurchased pursuant to employee benefit plans. Shares repurchased pursuant to employee benefit plans do not reduce the board authorizations referred to above. During the three months ended September 30, 2013, no shares were purchased. During the nine months ended September 30, 2013, the Company repurchased 141,535 common shares for $79.8 million at an average share price of $564, which was comprised of 140,000 common shares repurchased under the board authorization and 1,535 common shares repurchased pursuant to employee benefit plans.

Significant Transactions

durchblicker.at

In July 2014, White Mountains acquired 45% of the outstanding common shares of durchblicker.at, Austria's first independent price comparison portal for insurance, gas/electricity and financial services, for EUR 8.5 million (approximately $11.7 million based upon the foreign exchange spot rate at the date of acquisition).

PassportCard

In June 2014, White Mountains committed $21.0 million to fund a 50/50 joint venture with DavidShield Group (“DavidShield”) for the development, marketing and distribution of PassportCard travel insurance. The transaction is expected to close in the fourth quarter of 2014, subject to regulatory approvals.

QuoteLab

On March 14, 2014, White Mountains acquired 60% of the outstanding Class A common units of QuoteLab. As of September 30, 2014, White Mountains owned 58.4% of the equity of QuoteLab. QuoteLab is an advertising technology company that operates a transparent online advertising exchange that facilitates transactions between buyers and sellers of insurance media, including advertising inventory on QuoteLab’s owned and operated websites. White Mountains paid an initial purchase price of $28.1 million and will pay additional consideration to the sellers equal to 62.5% of the 2015 gross profit in excess of the 2013 gross profit. At acquisition, QuoteLab had total assets of $56.9 million, including $43.7 million of intangible assets, and total liabilities of $10.0 million.

Wobi

On February 19, 2014, White Mountains acquired 54% of the outstanding common shares of Wobi for NIS 14.4 million (approximately $4.1 million based upon the foreign exchange spot rate at the date of acquisition). In addition to the common shares, White Mountains also purchased NIS 12.7 million (approximately $3.6 million based upon the foreign exchange spot rate at the date of acquisition) of newly-issued convertible preferred shares of Wobi. Wobi is the only price comparison/aggregation business in Israel, with an insurance carrier panel that represents 85% of the premiums written in the Israeli insurance market. Wobi sells four lines of business, primarily personal auto, and operates as an agency, charging upfront commissions on all policy sales. As of September 30, 2014, on a fully converted basis, White Mountains owned 60.7% of Wobi. At acquisition, Wobi had total assets of $13.4 million, including $8.4 million of intangible assets, and total liabilities of $0.7 million.

Star & Shield

On January 31, 2014, White Mountains acquired certain assets and liabilities of Star & Shield Holdings LLC, including SSRM, the attorney-in-fact for SSIE, for a purchase price of $1.8 million.

White Mountains also purchased $17.0 million of surplus notes issued by SSIE. Principal and interest on the surplus notes are payable to White Mountains only with approval from the Florida Office of Insurance Regulation.

SSIE is a Florida-domiciled reciprocal insurance exchange providing private passenger auto insurance to the public safety community and their families. SSIE is a variable interest entity (“VIE”). As a result of SSRM’s role as the attorney-in-fact to SSIE and the investment in SSIE’s surplus notes, White Mountains is required to consolidate SSIE. At September 30, 2014, consolidated amounts included total assets of $11.8 million and total liabilities of $22.8 million of SSIE. For the three and nine months ended September 30, 2014, SSIE had pre-tax losses of $1.4 million and $11.1 million that were recorded in net loss attributable to non-controlling interests.

WM Solutions

In the first quarter of 2014, WM Solutions completed the shell sale of Citation Insurance Company, which resulted in a gain of $0.7 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.

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 car and boat business, to Markel Corporation. Concurrently, OneBeacon and Hagerty Insurance Agency (“Hagerty”) terminated their underwriting arrangement with respect to the collector car and boat business. OneBeacon recognized a pre-tax gain on sale of $23.0 million ($15.0 million after tax) in the first quarter of 2013.

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. Pursuant to the terms of the agreement, 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 approval. As a result of the agreement, the OneBeacon Runoff Business is reported as discontinued operations (see Note 15).

Common Shares Repurchased and Retired

During the past several years, White Mountains's board of directors has authorized the Company to repurchase its common shares, from time to time, subject to market conditions. The repurchase authorizations do not have a stated expiration date. As of September 30, 2014, White Mountains may repurchase an additional 382,118 shares under these board authorizations. In addition, from time to time White Mountains has also repurchased its common shares through tender offers that were separately approved by its board of directors.

During the three months ended September 30, 2014, the Company repurchased 122,264 common shares for $76.5 million at an average share price of $626.13, all of which were repurchased under the board authorization. During the nine months ended September 30, 2014, the Company repurchased 173,853 common shares for $106.9 million at an average share price of $614.78, which was comprised of 163,378 common shares repurchased under the board authorization and 10,475 common shares repurchased pursuant to employee benefit plans. Shares repurchased pursuant to employee benefit plans do not reduce the board authorizations referred to above.

During the three months ended September 30, 2013, no shares were purchased. During the nine months ended September 30, 2013, the Company repurchased 141,535 common shares for $79.8 million at an average share price of $564, which was comprised of 140,000 common shares repurchased under the board authorization and 1,535 common shares repurchased pursuant to employee benefit plans.