Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale, Amortized Cost	$ 2,069	$ 2,197
Debt Securities, Available-for-sale, Allowance for Credit Loss	1	3
Premium Receivable, Allowance for Credit Loss	$ 3	$ 4
Preferred stock, par value	$ 0.01
Preferred stock, shares authorized	20,000,000
Preferred Stock, Shares Issued	0	0
Common stock, par value	$ 0.01
Common stock, shares authorized	130,000,000
Common stock, shares issued	48,875,167	46,659,144
Common stock, shares outstanding	47,442,533
Equity investments in pooled funds [Member]
Other Investment Not Readily Marketable, Fair Value	$ 535	$ 463
Variable Interest Entity, Primary Beneficiary [Member]
Long-term debt	$ 2,738	$ 2,710