White Mountains Insurance Group Ltd. filings document the formal disclosures of a Bermuda-incorporated insurance and financial-services holding company with common shares listed on the New York Stock Exchange and the Bermuda Stock Exchange. The record includes 8-K reports on operating results, non-GAAP reconciliations, capital deployment, acquisitions, dispositions and reinsurance arrangements.
Filings also cover proxy governance, annual meeting matters, capital structure and shareholder actions, including share repurchase and tender-offer disclosures. Company-specific exhibits and pro forma materials describe transactions involving White Mountains Partners, Ark/WM Outrigger, Kudu, Distinguished and the completed sale of Bamboo, alongside risk and financial disclosures tied to insurance, reinsurance, investment portfolio performance and capital management.
White Mountains Insurance Group Ltd filed a Form 13F reporting its institutional equity holdings. The report lists a $313,368,520 total value across 2 reported positions and shows 0 other included managers. The filing was signed by Michaela J. Hildreth on 05-12-2026.
Neuberger Berman Group LLC and related advisers reported beneficial ownership of 121,583 shares of White Mountains Insurance Group common stock, representing 4.9% of the class. The filing attributes 110,283 shared voting power and 121,583 shared dispositive power to the reporting group.
The filing describes multiple Neuberger Berman affiliates and fiduciary capacities, notes information barriers that exclude certain subsidiaries, and includes standard disclaimers under Exchange Act Rules 13d-3 and 13d-4.
White Mountains Insurance Group reported total revenues of $517.8 million for the three months ended March 31, 2026 and a net loss attributable to common shareholders of $27.2 million, or $(12.59) per basic and diluted share, compared with earnings of $33.9 million a year earlier.
Results were heavily affected by investment performance, including $65.2 million of net realized and unrealized losses on its MediaAlpha stake and total net realized and unrealized investment losses of $54.4 million versus gains of $50.0 million in 2025. Core insurance operations at Ark/WM Outrigger generated net earned premiums of $373.8 million with $18.3 million of favorable prior-year reserve development, while cash flow from operations improved to $30.5 million from a use of $40.2 million.
White Mountains Insurance Group reported a small decline in book value per share to $2,170 as of March 31, 2026, down 0.8% for the quarter including dividends. The company posted a net loss attributable to common shareholders of $27 million versus net income of $34 million a year earlier, mainly from unrealized losses on its MediaAlpha investment.
Operating businesses were generally profitable. Ark/WM Outrigger delivered a 91% combined ratio and $1.1 billion of gross written premiums, while Kudu generated $63 million of revenue, $52 million of pre-tax income and a 12% trailing 12‑month return on equity. HG Global and Distinguished grew premiums but reported lower pre-tax income, and Other Operations reflected a $65 million unrealized loss from MediaAlpha despite positive investment results elsewhere. Excluding MediaAlpha, the total investment portfolio returned 1.0% in the quarter.
White Mountains Insurance Group Ltd was reported as having 127,993 shares beneficially owned by Vanguard Capital Management, representing 5.18% of the class as disclosed on a Schedule 13G. The filing states Vanguard Capital Management has sole dispositive power over 127,993 shares and sole voting power over 18,836 shares. The filing is signed by Ashley Grim on 04/30/2026 and includes a statement that ownership includes shares held for Vanguard funds and managed accounts.
White Mountains Insurance Group, through its operating company White Mountains Partners, has acquired a majority interest in BaseSix Systems LLC, a building systems integration and service provider. White Mountains’ equity investment in the deal was approximately $97 million, giving it control of a business focused on mission critical, low voltage systems for commercial and institutional customers across fire & life safety, network & wireless, security & access control, and audio-visual solutions.
Basesix, founded in 2018 and headquartered in Marietta, Georgia, has grown organically by delivering on-time, on-budget projects for complex integration needs and offering aftermarket service. Management from both organizations highlight plans to use the new capital partnership to support Basesix’s next growth phase, including potential new offices and strategic acquisitions.
White Mountains Insurance Group is asking shareholders to vote on three items at its 2026 annual meeting: electing four Class II directors to terms ending in 2029, approving an advisory vote on executive compensation, and ratifying PwC as independent auditor for 2026.
The proxy highlights a strong 2025, with book value per share reaching $2,188, up 25%, helped by the sale of Bamboo, which added roughly $320 per share, and about $200 million of share repurchases at accretive prices. Since its 1985 IPO, the company reports 13% annualized growth in book value per share and 12% in market value per share.
Operating businesses generally performed well, including Kudu’s 13% return on equity and HG Global’s $61 million of premiums, up 17%. The Board emphasizes governance practices such as 70% independent directors, an independent chair, 30% gender and 20% racial/ethnic diversity, and robust shareholder engagement, with outreach to holders of 75% of shares and meetings with holders of 31% of shares.
Executive pay is structured as pay-for-performance, with base salaries for named executive officers capped at $600,000 and 92% of 2025 CEO target compensation considered “at risk.” Long-term incentives are split between three-year cliff-vesting restricted shares and performance shares tied to compound growth in company value per share, with recent performance producing maximum or near-maximum payouts.
White Mountains Insurance Group Ltd — Schedule 13G/A amendment from The Vanguard Group. The filing states that, following an internal realignment effective January 12, 2026, certain Vanguard subsidiaries will report beneficial ownership separately. The Vanguard Group reports 0 shares beneficially owned and 0% of the class as of the amendment, reflecting disaggregation of holdings across affiliates.
The filing is signed by Ashley Grim, Head of Global Fund Administration, dated 03/27/2026.
WHITE MOUNTAINS INSURANCE GROUP LTD executive Robert Lawrence Seelig, EVP & General Counsel, made a bona fide gift of 50 Common Shares on 2026-03-19. The gift carried no sale proceeds. After this transfer, he directly holds 17,857 Common Shares and 2,500 restricted Common Shares, plus 4 Common Shares held indirectly by his wife and dependent children and 583 Common Shares held indirectly through the WTM Retirement Plan.