Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Fixed income securities, amortized cost	$ 2,197	$ 2,041
Short-term investments, amortized cost	426	507
Other Investment Not Readily Marketable, Fair Value	463	556
Debt Securities, Available-for-sale, Allowance for Credit Loss	3	0
Uncollectable premium receivables	4	5
Reinsurance Recoverable, Allowance for Credit Loss	$ 0	$ 0
Preferred stock, par value	$ 0.01
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred Stock, Shares Outstanding	0	0
Common stock, shares authorized	130,000,000	130,000,000
Common stock, shares issued	46,659,144	46,658,990
Common Stock, Shares, Outstanding	45,195,370
Treasury Stock, Common, Shares	1,463,774	1,685,233
Collateral Pledged [Member]
Short-term investments, amortized cost	$ 27	$ 64
Short-term Investments [Member]
Fixed income securities, amortized cost	426	507
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Short-term Investments [Member] | Collateral Pledged [Member]
Fixed income securities, amortized cost	27	64
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Variable Interest Entity, Primary Beneficiary [Member]
Long-term Debt	2,710	2,788
Parent Company [Member]
Fixed income securities, amortized cost	14	13
Short-term investments, amortized cost	156	175
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Parent Company [Member] | Short-term Investments [Member]
Fixed income securities, amortized cost	$ 156	$ 175