Fair Value (Narrative) (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|---|
Sep. 30, 2026 |
Jun. 30, 2026 |
Sep. 30, 2026 |
Sep. 30, 2025 |
Dec. 31, 2025 |
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| Fair Value Disclosure [Line Items] | |||||
| Transfers between Fair Value Hierarchies | $ 0.0 | $ 0.0 | |||
| Fair Value | $ 166.1 | 166.1 | $ 146.1 | ||
| Debt Securities, Available-for-Sale, Realized Gain (Loss) | 0.1 | 0.2 | $ 0.1 | ||
| Debt and Equity Securities, FV-NI [Line Items] | |||||
| Equity Securities, FV-NI, Cost | 7.9 | 7.9 | 7.9 | ||
| Debt and Equity Securities, Unrealized Gain (Loss) | $ 0.7 | 1.4 | |||
| Equity Securities, FV-NI | 9.2 | 9.2 | 8.5 | ||
| Net Assets | 19.1 | 19.1 | 17.9 | ||
| Net Assets | 19.1 | 19.1 | 17.9 | ||
| U.S. Treasury debt securities | |||||
| Fair Value Disclosure [Line Items] | |||||
| Fair Value | 6.8 | 6.8 | 9.5 | ||
| Corporate/Other debt securities | |||||
| Fair Value Disclosure [Line Items] | |||||
| Available-for-sale Securities, Maturities, Next Twelve Months, Fair Value | 8.5 | 8.5 | |||
| Fair Value | 159.3 | 159.3 | $ 136.6 | ||
| US Treasury Securities | |||||
| Fair Value Disclosure [Line Items] | |||||
| Fair Value | $ 4.0 | $ 4.0 | |||
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- Definition Fair Value Disclosure [Line Items] No definition available.
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- Definition Transfers between Fair Value Hierarchies No definition available.
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- Definition Amount of net assets (liabilities). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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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 next fiscal year following 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/2003/role/disclosureRef
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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). Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount of unrealized gain (loss) on investment in debt and equity securities. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition Amount of realized gain (loss) on 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 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 Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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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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