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SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES | 12 Months Ended
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Dec. 31, 2024
SEC Schedule, 12-15, Insurance Companies, Summary of Investments, Other than Investments in Related Parties [Abstract] |
SCHEDULE I - SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES | WHITE MOUNTAINS INSURANCE GROUP, LTD. SUMMARY OF INVESTMENTS—OTHER THAN INVESTMENTS IN RELATED PARTIES As of December 31, 2024
Millions |  | Cost |  | Carrying Value |  | Fair Value
Fixed maturity investments: |  |  |  |  |  |
U.S. Government and agency obligations |  | $ | 461.8 |  |  | $ | 462.1 |  |  | $ | 462.1 |
Debt securities issued by corporations |  | 1,444.5 |  |  | 1,414.2 |  |  | 1,414.2 |
Municipal obligations |  | 3.2 |  |  | 3.2 |  |  | 3.2 |
Mortgage and asset-backed securities |  | 400.2 |  |  | 373.9 |  |  | 373.9 |
Collateralized loan obligations |  | 237.3 |  |  | 236.7 |  |  | 236.7 |
Foreign government and agency obligations |  | 22.2 |  |  | 21.5 |  |  | 21.5 |
Total fixed maturity investments |  | 2,569.2 |  |  | 2,511.6 |  |  | 2,511.6 |
Short-term investments |  | 964.2 |  |  | 964.2 |  |  | 964.2 |
Investment in MediaAlpha (1) |  | 59.2 |  |  | 201.6 |  |  | 201.6 |
Common equity securities: |  |  |  |  |  |
Common equity securities - Industrial, Miscellaneous and Other |  | 373.7 |  |  | 425.4 |  |  | 425.4 |
Common equity securities - Exchange traded funds |  | 163.3 |  |  | 224.6 |  |  | 224.6 |
Total common equity securities |  | 537.0 |  |  | 650.0 |  |  | 650.0 |
Other long-term investments (2) |  | 1,748.7 |  |  | 2,150.2 |  |  | 2,150.2 |
Total investments |  | $ | 5,878.3 |  |  | $ | 6,477.6 |  |  | $ | 6,477.6 |
(1) Under GAAP, equity method eligible investments are considered related parties. White Mountains’s Investment in MediaAlpha is equity method eligible. See Note 17 — “Equity Method Eligible Investments.” (2) Includes equity method eligible investments with a cost and carrying value of $1,083.8 and $1,423.3.

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- Definition The entire disclosure of information about investment held by insurance company, excluding investment in related party. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 15 -Publisher SEC Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 320 -Name Accounting Standards Codification -Section S99 -Paragraph 7 -Subparagraph (SX 210.12-15) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477271/946-320-S99-7 + Details
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