CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions |
Sep. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Fixed maturities, available for sale, amortized cost | $ 6,149.9 | $ 6,026.7 |
| Equity securities at cost | 56.2 | 56.2 |
| Limited partnership interests (Carried Under Fair Value Option, 2026, $44.0 and 2025, $0.0) | $ 1,093.5 | $ 1,100.6 |
| Preferred stock, par value (in usd per share) | $ 0.001 | $ 0.001 |
| Preferred stock, shares authorized (in shares) | 1,000,000 | 1,000,000 |
| Preferred stock, shares issued (in shares) | 0 | 0 |
| Common stock, par value (in usd per share) | $ 0.001 | $ 0.001 |
| Common stock, shares authorized (in shares) | 75,000,000 | 75,000,000 |
| Common stock, shares issued (in shares) | 67,587,965 | 67,323,929 |
| Treasury stock (in shares) | 27,109,244 | 26,664,472 |
| Fair Value, Recurring | ||
| Limited partnership interests (Carried Under Fair Value Option, 2026, $44.0 and 2025, $0.0) | $ 44.0 | $ 0.0 |
| X | ||||||||||
- Definition Face amount or stated value per share of common stock. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- Definition Amortized cost excluding accrued interest, after allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- Definition Amount of investment in equity method investee and investment in and advance to affiliate. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- Definition Number of shares issued for nonredeemable preferred shares and preferred shares redeemable solely at option of issuer. Includes, but is not limited to, preferred shares issued, repurchased, and held as treasury shares. Excludes preferred shares classified as debt. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- 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
|
| X | ||||||||||
- Details
|