Investments Investments - Equity Investments (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 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)	3	$ 6
Debt Securities, Available-for-sale, Allowance for Credit Loss	3	1	3	$ 1	3
Net Realized and Unrealized Gain (Loss) on Trading Securities		$ 9
Debt Securities, Trading, Realized Gain (Loss)	5
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	117		117		112
Illiquid Investments [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	83		83		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	79		79		70
Equity investments in pooled funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	533		533		463
Convertibles and Bonds with Warrants Attached
Schedule of Equity Method Investments [Line Items]
Other investments	23		23		0
Fixed Income Funds
Schedule of Equity Method Investments [Line Items]
Other investments	53		53		52
Equity Funds
Schedule of Equity Method Investments [Line Items]
Other investments	40		40		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	137		137		85
Priced Through Pricing Vendors [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	153		153		77
Priced Through Pricing Vendors [Member] | Interest Rate Contract [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	89		89		39
Priced Through Pricing Vendors [Member] | Equity [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	40		40		38
Priced Through Pricing Vendors [Member] | Convertibles and Bonds with Warrants Attached
Schedule of Equity Method Investments [Line Items]
Other investments	23		23		$ 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)			3	10
Net Realized and Unrealized Gain (Loss) on Trading Securities			12	$ 16
Commitments [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Other investments	$ 30		$ 30