Fair Value - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Payable to brokers
Assets and Liabilities Measured at Fair Value [Abstract]
Liabilities	$ (75)	$ (70)
Corporate and other bonds
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	22,325	24,845
States, municipalities and political subdivisions
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	9,638	11,943
Asset-backed
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	7,422	7,585
Fixed maturities available-for-sale
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	39,385	44,373
Fixed maturities trading
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	46	7
Fixed maturity securities
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	39,431	44,380
Equity securities
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	1,364	1,674
Short term investments and other
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	4,175	4,770
Receivables
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	12
Level 1 | Payable to brokers
Assets and Liabilities Measured at Fair Value [Abstract]
Liabilities	(75)	(70)
Level 1 | Corporate and other bonds
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	118	140
Level 1 | States, municipalities and political subdivisions
Assets and Liabilities Measured at Fair Value [Abstract]
Assets
Level 1 | Asset-backed
Assets and Liabilities Measured at Fair Value [Abstract]
Assets
Level 1 | Fixed maturities available-for-sale
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	118	140
Level 1 | Fixed maturities trading
Assets and Liabilities Measured at Fair Value [Abstract]
Assets
Level 1 | Fixed maturity securities
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	118	140
Level 1 | Equity securities
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	713	924
Level 1 | Short term investments and other
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	3,987	4,696
Level 1 | Receivables
Assets and Liabilities Measured at Fair Value [Abstract]
Assets
Level 2 | Payable to brokers
Assets and Liabilities Measured at Fair Value [Abstract]
Liabilities
Level 2 | Corporate and other bonds
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	21,361	23,768
Level 2 | States, municipalities and political subdivisions
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	9,592	11,887
Level 2 | Asset-backed
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	6,781	7,029
Level 2 | Fixed maturities available-for-sale
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	37,734	42,684
Level 2 | Fixed maturities trading
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	46	7
Level 2 | Fixed maturity securities
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	37,780	42,691
Level 2 | Equity securities
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	604	721
Level 2 | Short term investments and other
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	188	74
Level 2 | Receivables
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	12
Level 3 | Payable to brokers
Assets and Liabilities Measured at Fair Value [Abstract]
Liabilities
Level 3 | Corporate and other bonds
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	846	937
Level 3 | States, municipalities and political subdivisions
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	46	56
Level 3 | Asset-backed
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	641	556
Level 3 | Fixed maturities available-for-sale
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	1,533	1,549
Level 3 | Fixed maturities trading
Assets and Liabilities Measured at Fair Value [Abstract]
Assets
Level 3 | Fixed maturity securities
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	1,533	1,549
Level 3 | Equity securities
Assets and Liabilities Measured at Fair Value [Abstract]
Assets	47	29
Level 3 | Short term investments and other
Assets and Liabilities Measured at Fair Value [Abstract]
Assets
Level 3 | Receivables
Assets and Liabilities Measured at Fair Value [Abstract]
Assets