Investments - Schedule of Quantitative Information about Level 3 Fair Value Measurements (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 17,940,189	$ 17,589,342
Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	14,400,162	14,171,518
States, municipalities, and political subdivisions
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	2,968,024	2,880,626
Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	472,582	395,225
Significant Unobservable Inputs (Level 3) \| Corporates
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	339,629	309,324
Significant Unobservable Inputs (Level 3) \| Corporates \| Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	339,629
Significant Unobservable Inputs (Level 3) \| States, municipalities, and political subdivisions
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	2,977	$ 0
Significant Unobservable Inputs (Level 3) \| States, municipalities, and political subdivisions \| Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	2,977
Significant Unobservable Inputs (Level 3) \| Asset- backed Securities \| Discounted Cash Flow
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 129,976

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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+ Details

- 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.

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