Investments Investments - Equity Investments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Schedule of Equity Method Investments [Line Items]
Equity Securities Excluded From Fair Value Table	$ 13		$ 13
Equity Securities, FV-NI, Realized Gain (Loss)	0	$ 2
Debt Securities, Available-for-sale, Allowance for Credit Loss	2	1	3
Net Realized and Unrealized Gain (Loss) on Trading Securities		$ 7
Debt Securities, Trading, Realized Gain (Loss)	7
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	115		112
Illiquid Investments [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	85		84
Insurance Linked [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	0		1
Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	75		70
Equity investments in pooled funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	546		463
Equity Securities Excluded From Fair Value
Schedule of Equity Method Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0		0
Convertibles and Bonds with Warrants Attached
Schedule of Equity Method Investments [Line Items]
Other investments	16		0
Fixed Income Funds
Schedule of Equity Method Investments [Line Items]
Other investments	52		52
Equity Funds
Schedule of Equity Method Investments [Line Items]
Other investments	40		38
Real Estate Funds
Schedule of Equity Method Investments [Line Items]
Other investments	20
High Yield Fund
Schedule of Equity Method Investments [Line Items]
Other investments	142		85
Priced Through Pricing Vendors [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	152		77
Priced Through Pricing Vendors [Member] | Interest Rate Contract [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	95		39
Priced Through Pricing Vendors [Member] | Equity [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	40		38
Priced Through Pricing Vendors [Member] | Convertibles and Bonds with Warrants Attached
Schedule of Equity Method Investments [Line Items]
Other investments	16		$ 0
Commitments [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	$ 35