Variable Interest Entities	3 Months Ended
Mar. 31, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Variable Interest Entities	Variable Interest Entities Under GAAP, White Mountains is required to consolidate any entity in which it holds a controlling financial interest. A controlling financial interest is usually in the form of an investment representing the majority of the subsidiary’s voting interests. However, a controlling financial interest may also arise from a financial interest in a variable interest entity (“VIE”) through arrangements that do not involve ownership of voting interests. A VIE is a legal entity that (i) does not have sufficient equity at risk to finance its activities without additional financial support; (ii) is structured such that equity investors, as a group, lack the power, through voting or similar rights, to direct the activities that most significantly impact the entity’s economic performance; (iii) is structured such that the equity investors lack the obligation to absorb losses of, or the right to receive returns from, the entity; or (iv) is structured with non-substantive voting rights. White Mountains determines whether an entity is a VIE at the inception of its variable interest in the entity and upon the occurrence of certain reconsideration events. White Mountains consolidates a VIE if it determines that it is the primary beneficiary. The primary beneficiary is defined as the entity that holds a variable interest that gives it both the power to direct the VIE’s activities that most significantly impact its economic performance and the obligation to absorb losses of, or the right to receive returns from, the VIE that could potentially be significant to the VIE. The identification of the primary beneficiary of a VIE may require significant assumptions and judgment. When White Mountains determines it has a variable interest in a VIE, it determines whether it is the primary beneficiary of that VIE by performing an analysis that principally considers: (i) the VIE’s purpose and design, including the risks the VIE was designed to create and pass through to its variable interest holders; (ii) the VIE’s capital structure; (iii) the identification of the activities that most significantly impact the VIE’s economic performance; (iv) the governance provisions and other contractual arrangements between the VIE and its variable interest holders and other parties involved with the VIE; and (v) related party relationships. At inception of its variable interest in the VIE as well as on an ongoing basis, White Mountains performs qualitative assessments of each VIE to determine whether White Mountains is the primary beneficiary of a VIE. WM Outrigger Re As of March 31, 2026, White Mountains owned 100.0% of WM Outrigger Re’s preferred equity. White Mountains has determined that Outrigger Re Ltd. and its segregated accounts, including WM Outrigger Re, are VIEs. White Mountains is not the primary beneficiary of Outrigger Re Ltd. or its third-party segregated accounts. White Mountains is the primary beneficiary of WM Outrigger Re, as it has both the power to direct the activities that most significantly impact WM Outrigger Re’s economic performance and the obligation to absorb losses, or the right to receive returns, that could potentially be significant to WM Outrigger Re. As a result, White Mountains consolidates WM Outrigger Re’s results in its financial statements. The assets of WM Outrigger Re can only be used to settle the liabilities of WM Outrigger Re, and there is no recourse to the Company for any creditors of WM Outrigger Re. WM Outrigger Re’s obligations under its reinsurance agreement with GAIL are subject to an aggregate limit equal to the assets in its collateral trust at any point in time. As of March 31, 2026, investments of $117.7 million were held in its collateral trust account. BAM BAM is the first and only mutual municipal bond insurance company in the United States. HG Global, together with its subsidiaries, funded the initial capitalization of BAM through the purchase of $503.0 million of BAM Surplus Notes and, through its reinsurance subsidiary HG Re, provides first-loss reinsurance protection of up to 15%-of-par outstanding for each policy assumed from BAM. As a mutual insurance company, BAM is owned by and operated for the benefit of its members, the municipalities whose debt issuances are insured by BAM. White Mountains has determined that BAM is a VIE. BAM’s underwriting process was determined to be the activity that most significantly impacts BAM’s economic performance. BAM’s underwriting guidelines define the types of credits that BAM may insure. BAM has the ability to change its underwriting guidelines without HG Re’s approval. Pursuant to the FLRT, HG Re is only required to provide reinsurance on policies that fall within a separate set of FLRT underwriting guidelines. Changes to these FLRT underwriting guidelines require HG Re’s approval. However, because BAM may amend the BAM underwriting guidelines without the consent of HG Re, White Mountains does not have the power to direct BAM’s activities that most significantly impact its economic performance and is not BAM’s primary beneficiary. Accordingly, White Mountains does not consolidate BAM. BAM’s assets can only be used to settle BAM’s obligations, and general creditors of BAM have no recourse to the Company or HG Global. HG Re’s obligations to BAM under the FLRT are subject to an aggregate limit equal to the assets in the Collateral Trusts at any point in time. As of March 31, 2026, the Collateral Trusts held assets of $1,008.9 million. Distinguished As of March 31, 2026, White Mountains had a 55.5% limited partnership interest in Distinguished. White Mountains has determined that Distinguished is a VIE. As a limited partnership, Distinguished is a VIE because the limited partnership interests do not have substantive kick-out rights or participating rights. White Mountains is the primary beneficiary of Distinguished, as it has both the power to direct the activities that most significantly impact Distinguished’s economic performance through its control of Distinguished’s general partner and the obligation to absorb losses, or the right to receive returns, that could potentially be significant to Distinguished through its basic units owned. As a result, White Mountains consolidates Distinguished’s results in its financial statements. The assets of Distinguished can only be used to settle the liabilities of Distinguished, and there is no recourse to the Company for any creditors of Distinguished. Bamboo SPV As of March 31, 2026, White Mountains had a 27.9% limited partnership interest in the Bamboo SPV. White Mountains has determined that the Bamboo SPV is a VIE but that White Mountains is not the primary beneficiary and therefore does not consolidate the Bamboo SPV. White Mountains’s ownership interest gives White Mountains the ability to exert significant influence over the significant financial and operating activities of the Bamboo SPV. Accordingly, the Bamboo SPV meets the criteria to be accounted for under the equity method. White Mountains has taken the fair value option for its investment in the Bamboo SPV. Changes in the fair value of the Bamboo SPV are recorded in net realized and unrealized investment gains (losses). As of March 31, 2026, White Mountains’s maximum exposure to loss on its limited partnership interest in the Bamboo SPV is the carrying value of $260.0 million. PassportCard/DavidShield As of March 31, 2026, White Mountains’s ownership interest in PassportCard/DavidShield was 53.8%. White Mountains has determined that PassportCard/DavidShield is a VIE but that White Mountains is not the primary beneficiary and therefore does not consolidate PassportCard/DavidShield. The governance structure for PassportCard/DavidShield was designed to give White Mountains and its co-investor equal power to make the decisions that most significantly impact its operations. White Mountains does not have the unilateral power to direct the operations of PassportCard/DavidShield and does not hold a controlling financial interest. White Mountains’s ownership interest gives White Mountains the ability to exert significant influence over the significant financial and operating activities of PassportCard/DavidShield. Accordingly, White Mountains’s investment in PassportCard/DavidShield meets the criteria to be accounted for under the equity method. White Mountains has taken the fair value option for its investment in PassportCard/DavidShield. Changes in the fair value of PassportCard/DavidShield are recorded in net realized and unrealized investment gains (losses). As of March 31, 2026, White Mountains’s maximum exposure to loss on its equity investment in PassportCard/DavidShield and the non-interest-bearing loan to its co-investor is the total carrying value of $179.8 million. BroadStreet As of March 31, 2026, White Mountains’s had a 10.9% limited partnership interest in the BroadStreet SPV. White Mountains has determined that the BroadStreet SPV is a VIE but that White Mountains is not the primary beneficiary and therefore does not consolidate the BroadStreet SPV. White Mountains’s ownership interest gives White Mountains the ability to exert significant influence over the significant financial and operating activities of the BroadStreet SPV. Accordingly, the BroadStreet SPV meets the criteria to be accounted for under the equity method. White Mountains has taken the fair value option for its investment in the BroadStreet SPV, which is measured at NAV as a practical expedient. Changes in the fair value of the BroadStreet SPV are recorded in net realized and unrealized investment gains (losses). As of March 31, 2026, White Mountains’s maximum exposure to loss on its limited partnership interest in the BroadStreet SPV is the carrying value of $170.1 million. Limited Partnerships White Mountains’s investments in limited partnerships are generally considered VIEs because the limited partnership interests do not have substantive kick-out rights or participating rights. White Mountains does not have the unilateral power to direct the operations of these limited partnerships, and therefore White Mountains is not the primary beneficiary and does not consolidate the limited partnerships. White Mountains has taken the fair value option for its investments in limited partnerships, which are generally measured at NAV as a practical expedient. As of March 31, 2026, White Mountains’s maximum exposure to loss on its investments in limited partnerships is the carrying value of $284.1 million.

Under GAAP, White Mountains is required to consolidate any entity in which it holds a controlling financial interest. A controlling financial interest is usually in the form of an investment representing the majority of the subsidiary’s voting interests. However, a controlling financial interest may also arise from a financial interest in a variable interest entity (“VIE”) through arrangements that do not involve ownership of voting interests. A VIE is a legal entity that (i) does not have sufficient equity at risk to finance its activities without additional financial support; (ii) is structured such that equity investors, as a group, lack the power, through voting or similar rights, to direct the activities that most significantly impact the entity’s economic performance; (iii) is structured such that the equity investors lack the obligation to absorb losses of, or the right to receive returns from, the entity; or (iv) is structured with non-substantive voting rights. White Mountains determines whether an entity is a VIE at the inception of its variable interest in the entity and upon the occurrence of certain reconsideration events.

White Mountains consolidates a VIE if it determines that it is the primary beneficiary. The primary beneficiary is defined as the entity that holds a variable interest that gives it both the power to direct the VIE’s activities that most significantly impact its economic performance and the obligation to absorb losses of, or the right to receive returns from, the VIE that could potentially be significant to the VIE. The identification of the primary beneficiary of a VIE may require significant assumptions and judgment. When White Mountains determines it has a variable interest in a VIE, it determines whether it is the primary beneficiary of that VIE by performing an analysis that principally considers: (i) the VIE’s purpose and design, including the risks the VIE was designed to create and pass through to its variable interest holders; (ii) the VIE’s capital structure; (iii) the identification of the activities that most significantly impact the VIE’s economic performance; (iv) the governance provisions and other contractual arrangements between the VIE and its variable interest holders and other parties involved with the VIE; and (v) related party relationships. At inception of its variable interest in the VIE as well as on an ongoing basis, White Mountains performs qualitative assessments of each VIE to determine whether White Mountains is the primary beneficiary of a VIE.

As of March 31, 2026, White Mountains owned 100.0% of WM Outrigger Re’s preferred equity. White Mountains has determined that Outrigger Re Ltd. and its segregated accounts, including WM Outrigger Re, are VIEs. White Mountains is not the primary beneficiary of Outrigger Re Ltd. or its third-party segregated accounts. White Mountains is the primary beneficiary of WM Outrigger Re, as it has both the power to direct the activities that most significantly impact WM Outrigger Re’s economic performance and the obligation to absorb losses, or the right to receive returns, that could potentially be significant to WM Outrigger Re. As a result, White Mountains consolidates WM Outrigger Re’s results in its financial statements. The assets of WM Outrigger Re can only be used to settle the liabilities of WM Outrigger Re, and there is no recourse to the Company for any creditors of WM Outrigger Re. WM Outrigger Re’s obligations under its reinsurance agreement with GAIL are subject to an aggregate limit equal to the assets in its collateral trust at any point in time. As of March 31, 2026, investments of $117.7 million were held in its collateral trust account.

BAM is the first and only mutual municipal bond insurance company in the United States. HG Global, together with its subsidiaries, funded the initial capitalization of BAM through the purchase of $503.0 million of BAM Surplus Notes and, through its reinsurance subsidiary HG Re, provides first-loss reinsurance protection of up to 15%-of-par outstanding for each policy assumed from BAM. As a mutual insurance company, BAM is owned by and operated for the benefit of its members, the municipalities whose debt issuances are insured by BAM. White Mountains has determined that BAM is a VIE.

BAM’s underwriting process was determined to be the activity that most significantly impacts BAM’s economic performance. BAM’s underwriting guidelines define the types of credits that BAM may insure. BAM has the ability to change its underwriting guidelines without HG Re’s approval. Pursuant to the FLRT, HG Re is only required to provide reinsurance on policies that fall within a separate set of FLRT underwriting guidelines. Changes to these FLRT underwriting guidelines require HG Re’s approval. However, because BAM may amend the BAM underwriting guidelines without the consent of HG Re, White Mountains does not have the power to direct BAM’s activities that most significantly impact its economic performance and is not BAM’s primary beneficiary. Accordingly, White Mountains does not consolidate BAM.

BAM’s assets can only be used to settle BAM’s obligations, and general creditors of BAM have no recourse to the Company or HG Global. HG Re’s obligations to BAM under the FLRT are subject to an aggregate limit equal to the assets in the Collateral Trusts at any point in time. As of March 31, 2026, the Collateral Trusts held assets of $1,008.9 million.

As of March 31, 2026, White Mountains had a 55.5% limited partnership interest in Distinguished. White Mountains has determined that Distinguished is a VIE. As a limited partnership, Distinguished is a VIE because the limited partnership interests do not have substantive kick-out rights or participating rights. White Mountains is the primary beneficiary of Distinguished, as it has both the power to direct the activities that most significantly impact Distinguished’s economic performance through its control of Distinguished’s general partner and the obligation to absorb losses, or the right to receive returns, that could potentially be significant to Distinguished through its basic units owned. As a result, White Mountains consolidates Distinguished’s results in its financial statements. The assets of Distinguished can only be used to settle the liabilities of Distinguished, and there is no recourse to the Company for any creditors of Distinguished.

As of March 31, 2026, White Mountains had a 27.9% limited partnership interest in the Bamboo SPV. White Mountains has determined that the Bamboo SPV is a VIE but that White Mountains is not the primary beneficiary and therefore does not consolidate the Bamboo SPV. White Mountains’s ownership interest gives White Mountains the ability to exert significant influence over the significant financial and operating activities of the Bamboo SPV. Accordingly, the Bamboo SPV meets the criteria to be accounted for under the equity method. White Mountains has taken the fair value option for its investment in the Bamboo SPV. Changes in the fair value of the Bamboo SPV are recorded in net realized and unrealized investment gains (losses). As of March 31, 2026, White Mountains’s maximum exposure to loss on its limited partnership interest in the Bamboo SPV is the carrying value of $260.0 million.

As of March 31, 2026, White Mountains’s ownership interest in PassportCard/DavidShield was 53.8%. White Mountains has determined that PassportCard/DavidShield is a VIE but that White Mountains is not the primary beneficiary and therefore does not consolidate PassportCard/DavidShield. The governance structure for PassportCard/DavidShield was designed to give White Mountains and its co-investor equal power to make the decisions that most significantly impact its operations. White Mountains does not have the unilateral power to direct the operations of PassportCard/DavidShield and does not hold a controlling financial interest. White Mountains’s ownership interest gives White Mountains the ability to exert significant influence over the significant financial and operating activities of PassportCard/DavidShield. Accordingly, White Mountains’s investment in PassportCard/DavidShield meets the criteria to be accounted for under the equity method. White Mountains has taken the fair value option for its investment in PassportCard/DavidShield. Changes in the fair value of PassportCard/DavidShield are recorded in net realized and unrealized investment gains (losses). As of March 31, 2026, White Mountains’s maximum exposure to loss on its equity investment in PassportCard/DavidShield and the non-interest-bearing loan to its co-investor is the total carrying value of $179.8 million.

As of March 31, 2026, White Mountains’s had a 10.9% limited partnership interest in the BroadStreet SPV. White Mountains has determined that the BroadStreet SPV is a VIE but that White Mountains is not the primary beneficiary and therefore does not consolidate the BroadStreet SPV. White Mountains’s ownership interest gives White Mountains the ability to exert significant influence over the significant financial and operating activities of the BroadStreet SPV. Accordingly, the BroadStreet SPV meets the criteria to be accounted for under the equity method. White Mountains has taken the fair value option for its investment in the BroadStreet SPV, which is measured at NAV as a practical expedient. Changes in the fair value of the BroadStreet SPV are recorded in net realized and unrealized investment gains (losses). As of March 31, 2026, White Mountains’s maximum exposure to loss on its limited partnership interest in the BroadStreet SPV is the carrying value of $170.1 million.

White Mountains’s investments in limited partnerships are generally considered VIEs because the limited partnership interests do not have substantive kick-out rights or participating rights. White Mountains does not have the unilateral power to direct the operations of these limited partnerships, and therefore White Mountains is not the primary beneficiary and does not consolidate the limited partnerships. White Mountains has taken the fair value option for its investments in limited partnerships, which are generally measured at NAV as a practical expedient. As of March 31, 2026, White Mountains’s maximum exposure to loss on its investments in limited partnerships is the carrying value of $284.1 million.