Fair Value Measurements (Details) - Fair Value Hierarchy - Recurring basis [Member] - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	$ 75,285	$ 78,726
Other liabilities measured on a recurring basis	3	3
Fixed maturities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	74,386	77,810
U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	3,173	3,562
Obligations of U.S. states, municipalities and political subdivisions [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	35,288	36,862
Debt securities issued by foreign governments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	1,041	1,041
Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	1,760	1,817
Corporate and all other bonds [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	33,124	34,528
Equity securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	880	893
Common stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	816	827
Non-redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	64	66
Other Investments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	19	23
Level 1 [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	3,708	4,110
Other liabilities measured on a recurring basis	0	0
Level 1 [Member] | Fixed maturities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	3,176	3,562
Level 1 [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	3,173	3,562
Level 1 [Member] | Obligations of U.S. states, municipalities and political subdivisions [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 1 [Member] | Debt securities issued by foreign governments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 1 [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 1 [Member] | Corporate and all other bonds [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	3	0
Level 1 [Member] | Equity securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	515	530
Level 1 [Member] | Common stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	497	509
Level 1 [Member] | Non-redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	18	21
Level 1 [Member] | Other Investments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	17	18
Level 2 [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	70,954	74,020
Other liabilities measured on a recurring basis	0	0
Level 2 [Member] | Fixed maturities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	70,934	74,000
Level 2 [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 2 [Member] | Obligations of U.S. states, municipalities and political subdivisions [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	35,284	36,858
Level 2 [Member] | Debt securities issued by foreign governments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	1,041	1,041
Level 2 [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	1,712	1,762
Level 2 [Member] | Corporate and all other bonds [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	32,897	34,339
Level 2 [Member] | Equity securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	20	20
Level 2 [Member] | Common stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 2 [Member] | Non-redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	20	20
Level 2 [Member] | Other Investments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 3 [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	623	596
Other liabilities measured on a recurring basis	3	3
Estimated fair value of put/call option reported in other liabilities	3	3
Level 3 [Member] | Fixed maturities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	276	248
Level 3 [Member] | U.S. Treasury securities and obligations of U.S. government and government agencies and authorities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 3 [Member] | Obligations of U.S. states, municipalities and political subdivisions [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	4	4
Level 3 [Member] | Debt securities issued by foreign governments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	0	0
Level 3 [Member] | Mortgage-backed securities, collateralized mortgage obligations and pass-through securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	48	55
Level 3 [Member] | Corporate and all other bonds [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	224	189
Level 3 [Member] | Equity securities [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	345	343
Level 3 [Member] | Common stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	319	318
Level 3 [Member] | Non-redeemable preferred stock [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	26	25
Level 3 [Member] | Investment in non-public common and preferred equity securities where the fair value estimate is determined either internally or by an external fund manager [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	345	343
Level 3 [Member] | Other Investments [Member]
Level within the fair value hierarchy at which the Company's financial assets and financial liabilities are measured
Total invested assets measured on a recurring basis	$ 2	$ 5