Fair Value of Financial Instruments - Schedule of Changes in Warrants (Details) - Level 3 - Warrants - Root Warrants - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | 12 Months Ended | ||
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Sep. 30, 2026 |
Sep. 30, 2025 |
Sep. 30, 2026 |
Sep. 30, 2025 |
Dec. 31, 2022 |
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| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] | |||||
| Opening balance | $ 11 | $ 243 | $ 56 | $ 120 | |
| Cancellation of Original Root Warrants | (11) | 0 | (11) | 0 | |
| New Root Warrants to acquire Root's Class A common stock | 19 | 0 | 19 | 0 | $ 75 |
| Unrealized (loss) gain | (5) | (120) | (50) | 3 | |
| Ending balance | $ 14 | $ 123 | $ 14 | $ 123 | |
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- Definition Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Cancellation No definition available.
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
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- Definition Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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