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Earnings Per Share (Tables) | 9 Months Ended
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Sep. 30, 2024
Earnings Per Share [Abstract] |
Computation of earnings per share | The following table presents the Company’s computation of earnings per share from continuing operations for the three and nine months ended September 30, 2024 and 2023.
|  | Three Months Ended September 30, |  | Nine Months Ended September 30,
|  | 2024 |  | 2023 |  | 2024 |  | 2023
Basic and diluted earnings per share numerators (in millions): |  |  |  |  |  |  |  |
Net income (loss) attributable to White Mountains’s common shareholders |  | $ | 179.0 |  |  | $ | 23.6 |  |  | $ | 360.8 |  |  | $ | 222.7 |
Allocation of (earnings) losses to participating restricted common shares (1) |  | (2.5) |  |  | (.3) |  |  | (4.6) |  |  | (3.1) |
Basic and diluted earnings (losses) per share numerators |  | $ | 176.5 |  |  | $ | 23.3 |  |  | $ | 356.2 |  |  | $ | 219.6 |
Basic earnings per share denominators (in thousands): |  |  |  |  |  |  |  |
Total average common shares outstanding during the period |  | 2,568.1 |  |  | 2,560.5 |  |  | 2,564.8 |  |  | 2,564.2 |
Average unvested restricted common shares (2) |  | (35.4) |  |  | (37.6) |  |  | (32.9) |  |  | (35.5) |
Basic earnings (losses) per share denominator |  | 2,532.7 |  |  | 2,522.9 |  |  | 2,531.9 |  |  | 2,528.7 |
Diluted earnings per share denominator (in thousands): |  |  |  |  |  |  |  |
Total average common shares outstanding during the period |  | 2,568.1 |  |  | 2,560.5 |  |  | 2,564.8 |  |  | 2,564.2 |
Average unvested restricted common shares (2) |  | (35.4) |  |  | (37.6) |  |  | (32.9) |  |  | (35.5) |
Diluted earnings (losses) per share denominator |  | 2,532.7 |  |  | 2,522.9 |  |  | 2,531.9 |  |  | 2,528.7 |
Basic and diluted earnings per share (in dollars): |  |  |  |  |  |  |  |
Distributed earnings - dividends declared and paid |  | $ | — |  |  | $ | — |  |  | $ | 1.00 |  |  | $ | 1.00 |
Undistributed earnings (losses) |  | 69.68 |  |  | 9.19 |  |  | 139.66 |  |  | 85.82 |
Basic and diluted earnings (losses) per share |  | $ | 69.68 |  |  | $ | 9.19 |  |  | $ | 140.66 |  |  | $ | 86.82 |
(1) Restricted shares issued by White Mountains receive dividends, and therefore, are considered participating securities. (2) Restricted shares outstanding vest upon a stated date. See Note 12 — “Employee Share-Based Incentive Compensation Plans.”
Schedule of undistributed earnings | The following table presents the undistributed net earnings (losses) for the three and nine months ended September 30, 2024 and 2023.
|  | Three Months Ended September 30, |  | Nine Months Ended September 30,
Millions |  | 2024 |  | 2023 |  | 2024 |  | 2023
Undistributed net earnings: |  |  |  |  |  |  |  |
Net income (loss) attributable to White Mountains’s common shareholders, net of restricted common share amounts |  | $ | 176.5 |  |  | $ | 23.3 |  |  | $ | 356.2 |  |  | $ | 219.6 |
Dividends declared, net of restricted common share amounts (1) |  | — |  |  | — |  |  | (2.5) |  |  | (2.5) |
Total undistributed net earnings (losses), net of restricted common share amounts |  | $ | 176.5 |  |  | $ | 23.3 |  |  | $ | 353.7 |  |  | $ | 217.1 |
(1) Restricted shares issued by White Mountains receive dividends, and therefore, are considered participating securities.

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- Definition Tabular disclosure of an entity's basic and diluted earnings per share calculations, including a reconciliation of numerators and denominators of the basic and diluted per-share computations for income from continuing operations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 260 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482662/260-10-50-1 + Details
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