White Mountains Insurance Group Ltd
WTM- Exchange
- NYSE
- Industry
- Fire, Marine & Casualty Insurance
- SEC CIK
- 0000776867
No open-market purchases or sales by White Mountains Insurance Group Ltd insiders were filed in the last 90 days; 356 institutions reported holding it in 13F filings for Q2 2026, worth $4.57B in total; Southeastern Asset Management (Longleaf) is the only superinvestor holding it.
Q1 2026 vs. Q4 2025
How the institutions holding White Mountains Insurance Group Ltd changed between Q4 2025 and Q1 2026.
All holders in Q1 2026All holders in Q4 2025
| Measure | Q4 2025 | Of which not filed for Q1 2026 | Q1 2026 | Change |
|---|---|---|---|---|
| Holders | 353 | 8 | 368 | +23 |
| Shares | 2.25M | 272.2K | 2.21M | +232.8K (+11.8%) |
| Value | $4.67B | $565.7M | $4.86B | +$748.7M (+18.2%) |
8 institutions that held it in Q4 2025 haven't filed for Q1 2026 yet. Not filing isn't selling, so the changes leave them out.
New holders (49)
Institutions that held White Mountains Insurance Group Ltd at the end of Q1 2026 but not at the end of Q4 2025.
Sold out (26)
Institutions that held White Mountains Insurance Group Ltd at the end of Q4 2025 and filed for Q1 2026 without it.
Not filed for Q1 2026 yet (8)
Institutions that held White Mountains Insurance Group Ltd at the end of Q4 2025 and haven't filed a 13F for Q1 2026. Not filing isn't selling, so they aren't counted as sold out.
| Institution | Shares, Q4 2025 | Value, Q4 2025 |
|---|---|---|
| Vanguard Group Inc | 235,698 | $489.8M |
| Norges Bank | 32,184 | $66.9M |
| Brandywine Global Investment Management, LLC | 3,226 | $6.70M |
| Prospector Partners LLC | 490 | $1.02M |
| Global Retirement Partners, LLC | 388 | $806.3K |
| David Loasby | 230 | $474.0K |
| CIBC Private Wealth Group, LLC | 26 | $54.0K |
| Trust Co of Vermont | 3 | $6.23K |