Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions |
Jun. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Fixed income securities (amortized costs) | $ 12,116.5 | |
| Preferred Stock, par value (in dollars per share) | $ 0.01 | $ 0.01 |
| Preferred Stock, authorized shares (in shares) | 75,000,000 | 75,000,000 |
| Preferred Stock, outstanding shares (in shares) | 0 | 0 |
| Common Stock, par value (in dollars per share) | $ 1.00 | |
| Common Stock, authorized shares (in shares) | 500,000,000 | 500,000,000 |
| Common Stock, issued shares (in shares) | 241,432,922 | 246,355,085 |
| Treasury Stock, Common, Shares | 0 | 0 |
| Fixed Income Securities [Member] | ||
| Fixed income securities (amortized costs) | $ 12,116.5 | $ 12,478.8 |
| Equity Securities [Member] | ||
| Equity securities - cost | $ 1,318.2 | $ 1,377.7 |
| Common Class B [Member] | ||
| Common Stock, par value (in dollars per share) | $ 1.00 | $ 1.00 |
| Common Stock, authorized shares (in shares) | 100,000,000 | 100,000,000 |
| Common Stock, issued shares (in shares) | 0 | 0 |
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- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Face amount or stated value per share of common stock. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition The maximum number of common shares permitted to be issued by an entity's charter and bylaws. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Number of previously issued common shares repurchased by the issuing entity and held in treasury. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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