Fair Value Measurements - Quantitative Information About Unobservable Inputs (Details) - Recurring - Significant Unobservable Inputs (Level 3) $ in Millions	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 512	$ 765
Corporate and government debt securities | Securities Priced by the Company
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 426	$ 664
Corporate and government debt securities | Securities Priced by the Company | Minimum | Liquidity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable Adjustment	0.0060	0.0060
Corporate and government debt securities | Securities Priced by the Company | Maximum | Liquidity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable Adjustment	0.1200	0.1060
Corporate and government debt securities | Securities Priced by the Company | Weighted Average | Liquidity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable Adjustment	0.0320	0.0410
Mortgage and other asset-backed securities | Securities Priced by the Company
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 85	$ 100
Mortgage and other asset-backed securities | Securities Priced by the Company | Minimum | Liquidity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable Adjustment	0.0060	0.0060
Mortgage and other asset-backed securities | Securities Priced by the Company | Maximum | Liquidity
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Unobservable Adjustment	0.0500	0.0390
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	0.0180	0.0100
Other debt securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Fair Value	$ 1	$ 1