Available-for-Sale Debt Securities - Gross Unrealized Losses and Fair Value Available-for-Sale Debt Securities in Unrealized Loss Position (Details) - USD ($) $ in Millions |
Dec. 31, 2025 |
Dec. 31, 2024 |
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| Corporate debt securities | ||
| Debt Securities, Available-for-sale [Line Items] | ||
| Less Than 12 Months, Fair Value | $ 298.2 | $ 334.9 |
| Less Than 12 Months, Unrealized Losses | (0.5) | (1.1) |
| 12 Months or Longer, Fair Value | 0.0 | 0.0 |
| 12 Months or Longer, Unrealized Loss | 0.0 | 0.0 |
| Total Fair Value | 298.2 | 334.9 |
| Total Unrealized Losses | $ (0.5) | (1.1) |
| Securities of government-sponsored entities | ||
| Debt Securities, Available-for-sale [Line Items] | ||
| Less Than 12 Months, Fair Value | 123.8 | |
| Less Than 12 Months, Unrealized Losses | (0.6) | |
| 12 Months or Longer, Fair Value | 0.0 | |
| 12 Months or Longer, Unrealized Loss | 0.0 | |
| Total Fair Value | 123.8 | |
| Total Unrealized Losses | $ (0.6) |
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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 Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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