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Segment Information
 9 Months Ended
Sep. 30, 2025
Segment Reporting [Abstract]  
Segment Information Segment Information
 
As of September 30, 2025, White Mountains conducted its operations through five reportable segments: (1) Ark/WM Outrigger, (2) HG Global, (3) Kudu, (4) Bamboo and (5) Distinguished, with its remaining operating businesses, holding companies and other assets included in Other Operations. White Mountains has made its segment determination based on consideration of the following criteria: (i) the nature of the business activities of each of the Company’s subsidiaries and affiliates; (ii) the manner in which the Company’s subsidiaries and affiliates are organized; (iii) the existence of primary managers responsible for specific subsidiaries and affiliates; and (iv) the organization of information provided to the Company’s CODMs and the Board of Directors. The Company’s CODMs are its Chief Executive Officer and its President and Chief Financial Officer. The CODMs utilize each segment’s pre-tax income (loss) in assessing each segment’s performance and allocating resources. Other measures of segment profitability are also reviewed by the CODMs. Significant intercompany transactions among White Mountains’s segments have been eliminated herein.
Effective September 30, 2025, as a result of the Bamboo Sale Transaction, the Bamboo Group’s assets and liabilities have been presented as held for sale in White Mountains’s consolidated balance sheet. See Note 2 - “Significant Transactions.”
Effective July 1, 2024, White Mountains no longer consolidates BAM. Through June 30, 2024, BAM’s results of operations were presented within the HG Global segment. See Note 2 — “Significant Transactions.”
The following tables present White Mountains’s pre-tax financial results by segment for the three and nine months ended September 30, 2025 and 2024:
Ark/WM OutriggerOther OperationsTotal
MillionsArkWM Outrigger ReHG Global
Kudu
Bamboo
Distinguished (1)
Three Months Ended September 30, 2025
Earned insurance premiums$498.6 $43.6 $7.5 $— $5.2 $— $2.9 $557.8 
Net investment income (2)
24.8 2.4 7.0 18.0 .6 .2 6.2 59.2 
Net realized and unrealized
   investment gains (losses) (2)
17.8 — 7.2 36.1 .2 — 14.9 76.2 
Net realized and unrealized investment
   gains (losses) from investment in
   MediaAlpha		— — — — — — 7.7 7.7 
Interest income from BAM Surplus Notes— — 7.5 — — — — 7.5 
Commission and fee revenues — — — — 63.9 14.1 4.3 82.3 
Other revenues2.3 — .1 .3 1.5 — 69.3 73.5 
     Total revenues543.5 46.0 29.3 54.4 71.4 14.3 105.3 864.2 
Loss and LAE252.4 2.2 — — 3.3 — .6 258.5 
Acquisition expenses92.4 14.4 2.0 — 2.0 — 1.0 111.8 
Cost of sales— — — — — — 55.3 55.3 
Broker commission expenses— — — — 21.5 5.5 — 27.0 
General and administrative expenses (3) (4)
61.7 — 1.0 4.7 26.8 10.2 72.4 176.8 
Change in fair value of contingent consideration36.1 — — — — — — 36.1 
Interest expense4.4 — 4.3 6.1 2.8 1.3 1.0 19.9 
     Total expenses447.0 16.6 7.3 10.8 56.4 17.0 130.3 685.4 
Pre-tax income (loss)$96.5 $29.4 $22.0 $43.6 $15.0 $(2.7)$(25.0)$178.8 
(1) Distinguished’s results are from September 2, 2025, the date of acquisition, through September 30, 2025.
(2) Net investment income and net realized and unrealized investment gains (losses) for both Bamboo and Distinguished are included in other revenues in the consolidated statement of operations.
(3) Ark’s general and administrative expenses include $33.6 of other underwriting expenses.
(4) Bamboo’s general and administrative expenses include $4.0 of amortization of other intangible assets.
Ark/WM Outrigger
MillionsArkWM Outrigger ReHG GlobalKudu
Bamboo
Other OperationsTotal
Three Months Ended September 30, 2024
Earned insurance premiums
$507.2 $45.0 $7.5 $— $10.6 $11.2 $581.5 
Net investment income (1)
21.3 3.0 6.0 17.2 .6 9.6 57.7 
Net realized and unrealized
   investment gains (losses) (1)
53.2 — 22.5 29.5 .7 29.7 135.6 
Net realized and unrealized investment
   gains (losses) from investment in
   MediaAlpha
— — — — — 88.2 88.2 
Interest income from
   BAM Surplus Notes
— — 7.9 — — — 7.9 
Change in fair value of BAM Surplus Notes— — 15.8 — — — 15.8 
Unrealized loss on deconsolidation of BAM— — (114.5)— — — (114.5)
Commission and fee revenues— — — — 42.7 4.1 46.8 
Other revenues3.7 — — .5 1.1 14.8 20.1 
     Total revenues585.4 48.0 (54.8)47.2 55.7 157.6 839.1 
Loss and LAE275.1 13.2 — — 4.4 4.2 296.9 
Acquisition expenses83.3 13.0 1.9 — 3.7 4.5 106.4 
Cost of sales— — — — — 7.6 7.6 
Broker commission expenses
— — — — 15.9 — 15.9 
General and administrative expenses (2) (3)
68.9 — .3 3.6 16.2 32.9 121.9 
Change in fair value of contingent
   consideration		34.2 — — — — — 34.2 
Interest expense4.9 — 5.8 5.7 — .3 16.7 
     Total expenses466.4 26.2 8.0 9.3 40.2 49.5 599.6 
Pre-tax income (loss)$119.0 $21.8 $(62.8)$37.9 $15.5 $108.1 $239.5 
(1) Bamboo’s net investment income and net realized and unrealized investment gains (losses) are included in other revenues in the consolidated statement of operations.
(2) Ark’s general and administrative expenses include $40.3 of other underwriting expenses.
(3) Bamboo’s general and administrative expenses include $3.9 of amortization of other intangible assets.
Ark/WM OutriggerOther Operations
MillionsArkWM Outrigger ReHG Global
Kudu
Bamboo
Distinguished (1)
Total
Nine Months Ended September 30, 2025
Earned insurance premiums$1,201.7 $62.7 $22.8 $— $21.7 $— $19.1 $1,328.0 
Net investment income (2)
70.2 6.8 19.8 56.7 2.0 .2 24.5 180.2 
Net realized and unrealized
   investment gains (losses) (2)
98.5 (.1)20.3 80.9 .5 — 49.5 249.6 
Net realized and unrealized investment
   gains (losses) from investment in
   MediaAlpha
— — — — — — 1.6 1.6 
Interest income from BAM Surplus Notes— — 22.5 — — — — 22.5 
Commission and fee revenues — — — — 167.2 14.1 12.4 193.7 
Other revenues10.8 — .2 1.0 3.9 — 139.7 155.6 
     Total revenues1,381.2 69.4 85.6 138.6 195.3 14.3 246.8 2,131.2 
Loss and LAE628.0 24.1 — — 15.9 — 18.8 686.8 
Acquisition expenses272.0 15.5 5.9 — 8.0 — 7.0 308.4 
Cost of sales— — — — — — 105.2 105.2 
Broker commission expenses— — — — 56.8 5.5 — 62.3 
General and administrative expenses (3) (4)
154.0 .1 2.6 12.3 69.4 10.2 161.7 410.3 
Change in fair value of contingent
   consideration
74.2 — — — — — — 74.2 
Interest expense12.9 — 13.4 18.6 7.8 1.3 2.3 56.3 
     Total expenses1,141.1 39.7 21.9 30.9 157.9 17.0 295.0 1,703.5 
Pre-tax income (loss)$240.1 $29.7 $63.7 $107.7 $37.4 $(2.7)$(48.2)$427.7 
(1) Distinguished’s results are from September 2, 2025, the date of acquisition, through September 30, 2025.
(2) Net investment income and net realized and unrealized investment gains (losses) for both Bamboo and Distinguished are included in other revenues in the consolidated statement of operations.
(3) Ark’s general and administrative expenses include $108.4 of other underwriting expenses.
(4) Bamboo’s general and administrative expenses include $12.0 of amortization of other intangible assets.
Ark/WM OutriggerHG GlobalOther Operations
MillionsArkWM Outrigger ReHG Global
BAM (1) (2)
Kudu
BambooTotal
Nine Months Ended September 30, 2024
Earned insurance premiums$1,110.5 $62.8 $21.5 $2.8 $— $27.0 $19.8 $1,244.4 
Net investment income (3)
57.6 8.9 17.3 8.8 50.1 1.5 27.9 172.1 
Net realized and unrealized investment
   gains (losses) (3)
84.1 — 13.2 (5.1)77.5 .6 60.4 230.7 
Net realized and unrealized investment
   gains (losses) from investment in
   MediaAlpha
— — — — — — 159.7 159.7 
Interest income (expense) from
   BAM Surplus Notes		— — 21.1 (13.2)— — — 7.9 
Change in fair value of BAM Surplus Notes— — 15.8 — — — — 15.8 
Unrealized loss on deconsolidation of BAM— — (114.5)— — — — (114.5)
Commission and fee revenues— — — — — 97.3 11.1 108.4 
Other revenues9.6 — — 1.1 .5 2.4 43.7 57.3 
     Total revenues1,261.8 71.7 (25.6)(5.6)128.1 128.8 322.6 1,881.8 
Loss and LAE630.4 13.6 — — — 14.5 8.1 666.6 
Acquisition expenses212.9 17.9 5.9 .4 — 9.7 7.1 253.9 
Cost of sales— — — — — — 22.2 22.2 
Broker commission expenses— — — — — 37.9 — 37.9 
General and administrative expenses (4) (5)
153.9 .1 1.3 33.5 10.5 43.9 126.4 369.6 
Change in fair value of contingent
   consideration		47.5 — — — — — — 47.5 
Interest expense15.0 — 13.4 — 16.7 — 1.6 46.7 
     Total expenses1,059.7 31.6 20.6 33.9 27.2 106.0 165.4 1,444.4 
Pre-tax income (loss)$202.1 $40.1 $(46.2)$(39.5)$100.9 $22.8 $157.2 $437.4 
(1) Effective July 1, 2024 White Mountains no longer consolidates BAM. For the period from January 1, 2024 through June 30, 2024, BAM’s results of operations were presented within the HG Global segment.
(2) BAM manages its affairs on a statutory accounting basis. BAM’s statutory surplus includes the BAM Surplus Notes and is not reduced by accruals of interest expense on the BAM Surplus Notes. BAM’s statutory surplus is reduced only after a payment of principal or interest has been approved by the NYDFS.
(3) Bamboo’s net investment income and net realized and unrealized investment gains (losses) are included in other revenues in the consolidated statement of operations.
(4) Ark’s general and administrative expenses include $103.9 of other underwriting expenses.
(5) Bamboo’s general and administrative expenses include $12.4 of amortization of other intangible assets.

The following tables present White Mountains’s revenues from external customers by country for three and nine months ended September 30, 2025 and 2024:
Three Months Ended September 30, 2025
MillionsUnited StatesUnited KingdomBermudaOtherTotal
Earned insurance premiums$5.2 $335.2 $217.4 $— $557.8 
Commission and fee revenues78.0 — — 4.3 82.3 
Other revenues (1)
68.8 — — — 68.8 
Total$152.0 $335.2 $217.4 $4.3 $708.9 
(1) Amounts include revenues from external customers related to certain consolidated Other Operating Businesses.
Three Months Ended September 30, 2024
MillionsUnited StatesUnited KingdomBermudaOtherTotal
Earned insurance premiums$— $326.4 $255.1 $— $581.5 
Commission and fee revenues42.7 — — 4.1 46.8 
Other revenues (1)
14.1 — — — 14.1 
Total$56.8 $326.4 $255.1 $4.1 $642.4 
(1) Amounts include revenues from external customers related to certain consolidated Other Operating Businesses.
Nine Months Ended September 30, 2025
MillionsUnited StatesUnited KingdomBermudaOtherTotal
Earned insurance premiums$21.7 $779.7 $526.6 $— $1,328.0 
Commission and fee revenues181.3 — — 12.4 193.7 
Other revenues (1)
138.7 — — — 138.7 
Total$341.7 $779.7 $526.6 $12.4 $1,660.4 
(1) Amounts include revenues from external customers related to certain consolidated Other Operating Businesses.
Nine Months Ended September 30, 2024
MillionsUnited StatesUnited KingdomBermudaOtherTotal
Earned insurance premiums$2.8 $697.5 $544.1 $— $1,244.4 
Commission and fee revenues97.3 — — 11.1 108.4 
Other revenues (1)
42.3 — — — 42.3 
Total$142.4 $697.5 $544.1 $11.1 $1,395.1 
(1) Amounts include revenues from external customers related to certain consolidated Other Operating Businesses.

The following table presents White Mountains’s balance sheet information by segment as of September 30, 2025 and December 31, 2024:
Millions
Selected Balance Sheet Data		Ark/WM OutriggerHG GlobalKudu
Distinguished
Other
Operations		Total
September 30, 2025  
Total investments$3,694.1 $742.7 $1,239.0 $62.6 $1,260.2 $6,998.6 
Total assets$6,796.8 $1,266.1 $1,298.8 $713.7 $2,270.2 
(1)(2)
$12,345.6 
Total liabilities$4,948.4 $488.5 
(1)
$359.3 $276.0 $556.3 
(1)(2)
$6,628.5 
Redeemable noncontrolling interests
$— $— $— $132.4 $— $132.4 
Total White Mountains’s
   common shareholders’ equity
$1,367.7 $789.5 
(1)
$804.0 $230.0 $1,576.4 
(1)(2)
$4,767.6 
Nonredeemable noncontrolling interests
$480.7 $(11.9)$135.5 $75.3 $137.5 $817.1 
December 31, 2024
  
Total investments$3,139.7 $667.6 $1,041.9 $— $1,568.4 $6,417.6 
Total assets$5,299.0 $1,179.4 $1,108.4 $— $2,338.8 
(1)(2)
$9,925.6 
Total liabilities$3,664.8 $464.1 
(1)
$316.7 $— $349.0 
(1)(2)
$4,794.6 
Total White Mountains’s
   common shareholders’ equity
$1,223.8 $728.7 
(1)
$664.1 $— $1,867.1 
(1)(2)
$4,483.7 
Nonredeemable noncontrolling interests
$410.4 $(13.4)$127.6 $— $122.7 $647.3 
(1) HG Global preferred dividends payable to White Mountains’s subsidiaries is eliminated in White Mountains’s consolidated financial statements. For segment reporting, the HG Global preferred dividends payable to White Mountains’s subsidiaries included within the HG Global segment are eliminated against the offsetting receivable included within Other Operations and therefore added back to White Mountains’s common shareholders’ equity within the HG Global segment. As of September 30, 2025 and December 31, 2024, the HG Global preferred dividends payable to White Mountains’s subsidiaries were $510.6 and $462.1.
(2) Amounts include held for sale balances. See Note 19 — “Held for Sale.”