Investments Investments - Equity Investments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 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)	6	$ (14)
Debt Securities, Available-for-sale, Allowance for Credit Loss	1	0	1	$ 0	0
Net Realized and Unrealized Gain (Loss) on Trading Securities	9	$ (29)
Real Estate [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	23		23		22
Hedge Funds, Multi-strategy [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	172		172		186
Interest Rate Contract [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	74		74		80
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
Equity [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	56		56		64
Credit Index Product [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	41		41		63
Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	53		53		47
Equity investments in pooled funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	518		518		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	13		13
Priced Through Pricing Vendors [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	69		69		61
Priced Through Pricing Vendors [Member] | Equity [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	56		56		53
Priced Through Pricing Vendors [Member] | Convertibles and Bonds with Warrants Attached
Schedule of Equity Method Investments [Line Items]
Other investments	$ 13		13		$ 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	(25)
Net Realized and Unrealized Gain (Loss) on Trading Securities			$ 16	$ (42)