Business Context and Reporting Period
Company: White Mountains Insurance Group, Ltd.
Filing Type: Form 10-K (Annual Report)
Period Ended: December 31, 2025
Business Overview: White Mountains is a Bermuda-based holding company engaged in opportunistic acquisitions in the insurance, financial services, and related sectors. As of December 31, 2025, operations are conducted through four reportable segments: Ark/WM Outrigger (property and casualty insurance/reinsurance), HG Global (municipal bond guarantee reinsurance), Kudu (capital solutions for asset/wealth managers), and Distinguished (specialty insurance distribution). The "Other Operations" segment includes holding companies, investment assets, and various non-insurance businesses.
Key Financial Metrics
| Metric | 2025 | 2024 | 2023 |
|---|---|---|---|
| Total Revenues | $3,735.0 million | $2,239.8 million | $2,166.7 million |
| Net Income (Attributable to Common Shareholders) | $1,106.4 million | $230.4 million | $509.2 million |
| Comprehensive Income (Attributable to Common Shareholders) | $1,108.9 million | $230.3 million | $511.1 million |
| Book Value Per Share | $2,187.97 | $1,745.87 | $1,656.14 |
| Total Assets | $12,306.5 million | $9,925.6 million | N/A |
| Total Debt | $837.0 million | $562.5 million | N/A |
| Debt to Total Capital Ratio | 11.8% | 9.9% | N/A |
| Ark/WM Outrigger Combined Ratio | 81.4% | 81.8% | 79.6% |
Material Changes vs. Prior Period
- Significant Transaction (Bamboo Sale): On December 5, 2025, the Company sold a controlling interest in the Bamboo Group for net cash proceeds of $848 million, recognizing a net gain of $816 million. This transaction was the primary driver of the 25% increase in book value per share and the surge in net income compared to 2024.
- Acquisitions:
- Distinguished: Acquired a controlling interest on September 2, 2025, for $225 million in cash consideration. Distinguished is a specialty insurance MGA.
- Enterprise Solutions: Acquired a controlling interest on April 1, 2025, for $58 million. This was the first acquisition by WTM Partners.
- BroadStreet: Deployed $150 million into BroadStreet (insurance brokerage) via a special purpose vehicle in July 2025.
- Deconsolidation of BAM: Effective July 1, 2024, the Company deconsolidated Build America Mutual Assurance Company (BAM). The BAM Surplus Notes were fair-valued, resulting in a $115 million unrealized loss in 2024. In 2025, the fair value of these notes declined by $38 million.
- Tax Impact: The Company recognized a net deferred tax expense of $73 million in 2025 due to the reversal of the deferred tax asset related to the Bermuda economic transition adjustment, following new Luxembourg legislation.
- Ark Performance: Ark's combined ratio remained stable at 83% in 2025 (vs. 83% in 2024). Catastrophe losses were 8 points in 2025 (driven by Hurricane Melissa and California wildfires) compared to 13 points in 2024. Gross written premiums increased 16% to $2,557 million.
Guidance, Outlook, and Risks
- Capital Deployment: Undeployed capital stands at roughly $1.0 billion (including a $128 million distribution from WM Outrigger Re received in January 2026). The Company continues to seek opportunistic acquisitions.
- Ark/WM Outrigger Outlook: Ark expects its net after-tax peak exposure for a 1-in-250 year event to approximate 20-35% of its tangible capital. WM Outrigger Re is not participating in the 2026 underwriting year but remains exposed to losses from the 2025 year until June 30, 2026.
- Key Risks:
- Catastrophe Exposure: Significant exposure to natural catastrophes (hurricanes, wildfires, earthquakes) and non-natural events (cyber, war, terrorism).
- Reserve Adequacy: Uncertainty in estimating loss and LAE reserves, particularly for long-tail casualty lines and emerging risks like social inflation.
- Valuation Volatility: Significant portions of the portfolio (BAM Surplus Notes, Kudu Participation Contracts, MediaAlpha) are valued using Level 3 inputs or market prices, subject to volatility.
- Taxation: Risks related to the OECD Pillar Two initiative and the potential loss of the Bermuda corporate income tax deferral after 2030.
Important Facts for Investor Verification
- Bamboo Sale Proceeds: Verify the utilization of the $848 million net cash proceeds from the Bamboo sale and the valuation of the retained $250 million indirect equity interest.
- BAM Surplus Notes Valuation: Review the discounted cash flow assumptions (discount rate of 8.05%) used to value the $339 million BAM Surplus Notes, which are sensitive to changes in BAM's ability to service debt.
- Ark Contingent Consideration: Monitor the $328.3 million contingent consideration liability related to the Ark acquisition, which increased by $173 million in 2025 based on tangible book value growth.
- MediaAlpha Investment: Verify the fair value of the $231.2 million investment in MediaAlpha, which is marked-to-market and impacts book value significantly ($7.00 per share impact for every $1.00 change in MediaAlpha stock price).
- Loss Reserve Development: Scrutinize the $106 million of net favorable prior year loss reserve development at Ark, which included $91 million of unfavorable development related to aviation losses from the Ukraine/Russia conflict.