13F Insight
DOSSIER · 13F Holders · Q1 2026Defensive growthQuality

WHITE MTNS INS GROUP LTD

379 institutions still hold WHITE MTNS INS GROUP LTD as of Q1 2026. Tracked across SEC 13F-HR filings, with insider and 13D/G activity surfaced alongside.

CUSIP G9618E107·379 13F holders·last filed Mar 31, 2026
Market cap
—
▼ 6.7%
vs prior quarter
13F value held
$3.4B
76.0% inst. owned
of float
Holders
379
+87 QoQ
filers reporting
Activity
+33 / −94
+858 added · −801 reduced
this quarter
Concentration
10.21%
DIMENSIONAL FUND ADVISORS LP #1
top holder share
AI Holders Summary · Q1 2026

379 institutions reported WHITE MTNS INS GROUP LTD in Q1 2026. DIMENSIONAL FUND ADVISORS LP leads at 10.2% of the visible book. +87 net new institutions vs prior quarter — accumulation reading.

Top holders

Sorted by position value. Source: SEC EDGAR 13F-HR filings.

#HolderValueShares% port.Quarter
01
DIMENSIONAL FUND ADVISORS LP
CIK 0000354204· Quasi-passive
$344M157K0.07%Q1 202602
Neuberger Berman Group LLC
CIK 0001465109
$274M125K0.21%Q1 202603
River Road Asset Management, LLC
CIK 0001341401
$265M121K3.00%Q1 202604
Vanguard Portfolio Management
CIK 0002100121
$254M116K0.01%Q1 202605
BlackRock, Inc.
CIK 0002012383
$249M113K0.00%Q1 202606
VANGUARD CAPITAL MANAGEMENT LLC
CIK 0002100119· Index
$240M109K0.01%Q1 202607
COOKE & BIELER LP
CIK 0000024386
$230M105K2.61%Q1 202608
FULLER & THALER ASSET MANAGEMENT, INC.
CIK 0001082327
$230M105K0.77%Q1 202609
FIDUCIARY MANAGEMENT INC /WI/
CIK 0000764532
$187M85K2.32%Q1 202610
Wallace Capital Management Inc.
CIK 0001459754
$173M79K19.88%Q1 202611
MORGAN STANLEY
CIK 0000895421
$130M59K0.01%Q1 202612
Boston Partners
CIK 0001386060
$126M57K0.13%Q1 202613
LONDON CO OF VIRGINIA
CIK 0001259887
$126M57K0.77%Q1 202614
STATE STREET CORP
CIK 0000093751
$108M49K0.00%Q1 202615
GEODE CAPITAL MANAGEMENT, LLC
CIK 0001214717· Index
$93M42K0.01%Q1 202616
GENDELL JEFFREY L
CIK 0001056581
$83M38K1.13%Q1 202617
REINHART PARTNERS, LLC.
CIK 0001080298
$82M37K2.36%Q1 202618
BANK OF AMERICA CORP /DE/
CIK 0000070858
$62M28K0.00%Q1 202619
Cannell & Spears LLC
CIK 0001426319
$62M28K1.21%Q1 202620
CHARLES SCHWAB INVESTMENT MANAGEMENT INC
CIK 0000884546· Index
$53M24K0.01%Q1 2026
Page 1 of 19
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