Fair Value Measurements - Quantitative Information About Unobservable Inputs (Details) - Recurring - Significant Unobservable Inputs (Level 3) $ in Millions	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Debt securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 373
Corporate | Securities Priced by the Company
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 329
Corporate | Securities Priced by the Company | Minimum | Liquidity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable Adjustment	0.0005
Corporate | Securities Priced by the Company | Maximum | Liquidity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable Adjustment	0.1475
Corporate | Securities Priced by the Company | Weighted Average | Liquidity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable Adjustment	0.0300
Mortgage and other asset-backed securities | Securities Priced by the Company
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 44
Mortgage and other asset-backed securities | Securities Priced by the Company | Minimum | Liquidity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable Adjustment	0.0105
Mortgage and other asset-backed securities | Securities Priced by the Company | Maximum | Liquidity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable Adjustment	0.0575
Mortgage and other asset-backed securities | Securities Priced by the Company | Weighted Average | Liquidity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable Adjustment	0.0290
Other debt securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 0	$ 1