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Fair Value Measurements - Additional Information - Narrative (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024 USD ($) quotesPerInvestment	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) quotesPerInvestment	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($) quotesPerInvestment	Dec. 31, 2022 USD ($) quotesPerInvestment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Quotes per fixed income investment | quotesPerInvestment	3.3		3.3		2.9	2.9
Assets | Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers in/(out)	$ 0.0	$ 0.0	$ 0.0	$ 0.0	$ 5.3	$ 0.0
Settlements and sales	$ (114.5)	$ (76.4)	$ (166.9)	$ (134.8)	$ (137.2)	$ (147.4)

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Fair value inputs offered quotes per fixed income investment.

+ References

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
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Amount of settlement 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.

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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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