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SCHEDULE V - VALUATION AND QUALIFYING ACCOUNTS | 12 Months Ended
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Dec. 31, 2025
SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract] |
SCHEDULE V - VALUATION AND QUALIFYING ACCOUNTS | WHITE MOUNTAINS INSURANCE GROUP, LTD. VALUATION AND QUALIFYING ACCOUNTS
Column A |  | Column B |  | Column C |  | Column D |  | Column E
|  |  |  | Additions (subtractions) |  |  |  |
Millions |  | Balance at beginning of period |  | Charged to costs and expenses |  | Charged to other accounts |  | Deductions described (1) |  | Balance at end of period
Years ended: |  |  |  |  |  |  |  |  |  |
Ark/WM Outrigger |  |  |  |  |  |  |  |  |  |
December 31, 2025 |  |  |  |  |  |  |  |  |  |
Reinsurance recoverables: |  |  |  |  |  |  |  |  |  |
Allowance for uncollectible balances |  | $ | 10.2 |  |  | $ | 1.4 |  |  | $ | — |  |  | $ | — |  |  | $ | 11.6 |
December 31, 2024 |  |  |  |  |  |  |  |  |  |
Reinsurance recoverables: |  |  |  |  |  |  |  |  |  |
Allowance for uncollectible balances |  | 7.7 |  |  | 2.5 |  |  | — |  |  | — |  |  | 10.2 |
December 31, 2023 |  |  |  |  |  |  |  |  |  |
Reinsurance recoverables: |  |  |  |  |  |  |  |  |  |
Allowance for uncollectible balances |  | 7.8 |  |  | (.2) |  |  | — |  |  | .1 |  |  | 7.7 |
(1)Represents net collections (charge-offs) of balances receivable and foreign currency translation.

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- Definition The entire disclosure for valuation and qualifying accounts and reserves. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 09 -Publisher SEC Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480738/235-10-S50-5 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 235 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 4 -Subparagraph (SX 210.12-09) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480678/235-10-S99-4 + Details
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- References No definition available. + Details
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