Investments - Available-for-Sale Debt Securities in Unrealized Loss Position (Details) - USD ($) $ in Millions |
Jun. 30, 2026 |
Dec. 31, 2025 |
|---|---|---|
| Fair Value | ||
| Less than 12 months | $ 1,325.2 | $ 234.6 |
| 12 months or longer | 0.0 | 3.5 |
| Total | 1,325.2 | 238.1 |
| Gross Unrealized Losses | ||
| Less than 12 months | (9.5) | (0.3) |
| 12 months or longer | 0.0 | 0.0 |
| Total | (9.5) | (0.3) |
| U.S. government and agency securities | ||
| Fair Value | ||
| Less than 12 months | 1,138.1 | 215.0 |
| 12 months or longer | 0.0 | 3.5 |
| Total | 1,138.1 | 218.5 |
| Gross Unrealized Losses | ||
| Less than 12 months | (8.2) | (0.3) |
| 12 months or longer | 0.0 | 0.0 |
| Total | (8.2) | (0.3) |
| Corporate debt securities | ||
| Fair Value | ||
| Less than 12 months | 187.1 | 19.6 |
| 12 months or longer | 0.0 | 0.0 |
| Total | 187.1 | 19.6 |
| Gross Unrealized Losses | ||
| Less than 12 months | (1.3) | 0.0 |
| 12 months or longer | 0.0 | 0.0 |
| Total | $ (1.3) | $ 0.0 |
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- References No definition available.
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset. Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset. Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
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- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset. Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
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- Definition Debt Securities, Available-For-Sale, Unrealized Loss Position, Fair Value No definition available.
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