Investments - Maturities of Fixed Maturities (Details) - USD ($) $ in Millions |
6 Months Ended | |
|---|---|---|
Jun. 30, 2026 |
Dec. 31, 2025 |
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| Amortized Cost, net | ||
| Due in 1 year or less | $ 277.8 | |
| Due after 1 year through 5 years | 1,264.2 | |
| Due after 5 years through 10 years | 1,602.1 | |
| Due after 10 years through 20 years | 1,711.8 | |
| Due after 20 years | 1,269.6 | |
| Amortized Cost, net | 6,125.5 | $ 6,026.7 |
| Fair Value | ||
| Due in 1 year or less | 276.1 | |
| Due after 1 year through 5 years | 1,240.8 | |
| Due after 5 years through 10 years | 1,556.5 | |
| Due after 10 years through 20 years | 1,574.0 | |
| Due after 20 years | 1,119.6 | |
| Total | $ 5,767.0 | $ 5,714.6 |
| Percent of Total Fair Value | ||
| Due in 1 year Or less | 4.80% | |
| Due after 1 year through 5 years | 21.50% | |
| Due after 5 years through 10 years | 27.00% | |
| Due after 10 years through 20 years | 27.30% | |
| Due after 20 years | 19.40% | |
| Total | 100.00% | |
| Average option-adjusted duration, in years | 5 years 10 months 24 days |
| X | ||||||||||
- Definition Investment debt securities average option adjusted duration expressed in number of years. No definition available.
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- Definition Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the eleventh rolling twelve months through the twentieth rolling twelve months following the latest balance sheet presented. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments. No definition available.
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- Definition Amount of available-for-sale debt securities at fair value maturing in the eleventh rolling twelve months through the twentieth rolling twelve months following the latest balance sheet presented. No definition available.
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- Definition Percentage of fair value of available for sale debt securities maturing in the eleventh rolling twelve months through the twentieth rolling twelve months following the latest balance sheet presented. No definition available.
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- Definition Percentage of fair value of available for sale debt securities maturing in the second rolling twelve months through the fifth rolling twelve months following the latest balance sheet presented. No definition available.
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- Definition Percentage of fair value of available for sale debt securities maturing after the twentieth rolling twelve months following the latest balance sheet presented. No definition available.
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- Definition Percentage of fair value of available for sale debt securities maturing in the sixth rolling twelve months through the tenth rolling twelve months following the latest balance sheet presented. No definition available.
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- Definition Percentage of fair value of available for sale debt securities maturing during the next rolling twelve months following the latest balance sheet presented. No definition available.
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- Definition Percentage of Total Fair Value [Abstract] No definition available.
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- Definition Available for sale securities debt maturities a percentage of fair value. No definition available.
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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), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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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), with single maturity date and allocated without single maturity date, maturing in remainder of current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in remainder of current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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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), with single maturity date and allocated without single maturity date, maturing in rolling sixth through tenth fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in rolling sixth through tenth fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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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), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year through fifth year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition Fair value of investment in debt security, measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year through fifth year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- References No definition available.
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- References No definition available.
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- 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
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- Definition Amount excluding accrued interest, 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
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