Investments Investments - Equity Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Equity Securities Excluded From Fair Value Table	$ 12		$ 12		$ 12
Equity Securities, FV-NI, Realized Gain (Loss)	0	$ (1)
Debt Securities, Available-for-sale, Allowance for Credit Loss	2	0	2	$ 0	0
Net Realized and Unrealized Gain (Loss) on Trading Securities	0	$ (7)
Real Estate [Member]
Schedule of Equity Method Investments [Line Items]
Other investments					22
Hedge Funds, Multi-strategy [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	109		109		186
Illiquid Investments [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	85		85		84
Insurance Linked [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	1		1		1
Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	62		62		47
Equity investments in pooled funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	449		449		556
Equity Securities Excluded From Fair Value
Schedule of Equity Method Investments [Line Items]
Debt Securities, Available-for-sale, Allowance for Credit Loss	0		0		0
Convertibles and Bonds with Warrants Attached
Schedule of Equity Method Investments [Line Items]
Other investments	0		0		8
Fixed Income Funds
Schedule of Equity Method Investments [Line Items]
Other investments	40		40		63
Equity Funds
Schedule of Equity Method Investments [Line Items]
Other investments	53		53		64
Real Estate Funds
Schedule of Equity Method Investments [Line Items]
Other investments	21		21
High Yield Fund
Schedule of Equity Method Investments [Line Items]
Other investments	78		78		80
Priced Through Pricing Vendors [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	87		87		61
Priced Through Pricing Vendors [Member] | Interest Rate Contract [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	35		35		0
Priced Through Pricing Vendors [Member] | Equity [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	53		53		53
Priced Through Pricing Vendors [Member] | Convertibles and Bonds with Warrants Attached
Schedule of Equity Method Investments [Line Items]
Other investments	$ 0		0		$ 8
Gains (losses) on securities held as of reporting date [Member]
Schedule of Equity Method Investments [Line Items]
Equity Securities, FV-NI, Realized Gain (Loss)			10	(27)
Net Realized and Unrealized Gain (Loss) on Trading Securities			$ 16	$ (49)