Investments - Quantitative Information about Level 3 Fair Value Measurements (Details) $ in Thousands	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 16,503,365	$ 21,305,287
Significant Unobservable Inputs (Level 3)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	528,447
Significant Unobservable Inputs (Level 3) | Private placement fixed maturities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	395,037
Significant Unobservable Inputs (Level 3) | Other corporate bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 83,046
Significant Unobservable Inputs (Level 3) | Other corporate bonds | Discounted Cash Flows | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0635
Significant Unobservable Inputs (Level 3) | Other corporate bonds | Discounted Cash Flows | Discount rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.0635
Significant Unobservable Inputs (Level 3) | Collateralized debt obligations
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 50,364
Significant Unobservable Inputs (Level 3) | Collateralized debt obligations | Discounted Cash Flows | Discount rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1025
Significant Unobservable Inputs (Level 3) | Collateralized debt obligations | Discounted Cash Flows | Discount rate | Weighted Average
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Measurement input	0.1025