Investments Investments - Equity Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Schedule of Equity Method Investments [Line Items]
Equity Securities Excluded From Fair Value Table	$ 26		$ 26		$ 13
Equity Securities, FV-NI, Realized Gain (Loss)	1	$ 0
Debt Securities, Available-for-sale, Allowance for Credit Loss	1	2	1	$ 2	3
Net Realized and Unrealized Gain (Loss) on Trading Securities		$ 0
Debt Securities, Trading, Realized Gain (Loss)	10
Other than Temporary Impairment Losses, Investments			1
Real Estate [Member]
Schedule of Equity Method Investments [Line Items]
Other investments					21
Hedge Funds, Multi-strategy [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	87		87		112
Illiquid Investments [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	84		84		84
Insurance Linked [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	0		0		1
Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	81		81		70
Equity investments in pooled funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	535		535		463
Convertibles and Bonds with Warrants Attached
Schedule of Equity Method Investments [Line Items]
Other investments	26		26		0
Fixed Income Funds
Schedule of Equity Method Investments [Line Items]
Other investments	57		57		52
Equity Funds
Schedule of Equity Method Investments [Line Items]
Other investments	67		67		38
Real Estate Funds
Schedule of Equity Method Investments [Line Items]
Other investments	0		0
High Yield Fund
Schedule of Equity Method Investments [Line Items]
Other investments	134		134		85
Priced Through Pricing Vendors [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	174		174		77
Priced Through Pricing Vendors [Member] | Interest Rate Contract [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	82		82		39
Priced Through Pricing Vendors [Member] | Equity [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	67		67		38
Priced Through Pricing Vendors [Member] | Convertibles and Bonds with Warrants Attached
Schedule of Equity Method Investments [Line Items]
Other investments	26		26		$ 0
Gains (losses) on securities held as of reporting date [Member]
Schedule of Equity Method Investments [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)			8	10
Net Realized and Unrealized Gain (Loss) on Trading Securities			23	$ 16
Commitments [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	$ 26		$ 26