Investments - Narrative (Details)	3 Months Ended			9 Months Ended			12 Months Ended
	Sep. 30, 2023 USD ($) state	Sep. 30, 2022 USD ($)		Sep. 30, 2023 USD ($) state	Sep. 30, 2022 USD ($)		Dec. 31, 2022 USD ($)		Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Summary of Investment Holdings [Line Items]
Debt securities, rated by investment advisor	$ 422,000,000			$ 422,000,000			$ 32,000,000
Securities on deposit with regulatory authorities	99,000,000			99,000,000			90,000,000
Accrued interest written off	1,000,000	$ 0		$ 1,000,000	$ 0
Debt Securities Available For Sale Accrued Interest After Allowance For Credit Loss Statement Of Financial Position Extensible List Not Disclosed Flag				Accrued interest receivables
Aggregate fair value of securities sold at a loss	$ 756,000,000	$ 1,068,000,000		$ 2,909,000,000	$ 3,966,000,000
Aggregate fair value of securities sold at a loss, percentage of book value	88.00%	94.00%		94.00%	93.00%
Proceeds from sales of available-for-sale debt securities	$ 900,000,000	$ 1,400,000,000		$ 4,200,000,000	$ 6,300,000,000
Collateralized loan obligation							276,000,000
Estimated loss from divestiture				(93,000,000)
Unconsolidated VIEs, exposure to loss	2,908,000,000			2,908,000,000			3,285,000,000
Equity securities	277,000,000			277,000,000			393,000,000	[1]
Mortgage loans, allowance for credit loss	200,000,000	79,000,000		200,000,000	79,000,000		95,000,000		$ 162,000,000	$ 80,000,000	$ 94,000,000
Financing receivables, accrued interest receivable	45,000,000	46,000,000		$ 45,000,000	46,000,000
Deferral of interest and principal payments, repayment period, COVID-19				1 year
Deferred interest and principal payments, COVID-19	9,000,000			$ 9,000,000
Accrued interest written off	2,000,000	0		2,000,000	0
Recorded investment	23,000,000			23,000,000			15,000,000
Unpaid principal balance, no related allowance	26,000,000			26,000,000			16,000,000
Average recorded investment				17,000,000			18,000,000
Investment income				0			0
Stressed loans	16,000,000			16,000,000			3,000,000
Policy loans, fair value under fair value option	3,432,000,000			3,432,000,000			3,419,000,000
Policy loans not held as collateral for reinsurance		900,000,000			900,000,000		1,000,000,000.0
Other invested assets	3,553,000,000			3,553,000,000			3,595,000,000	[1]
Securities loaned	$ 27,000,000			$ 27,000,000			35,000,000
Securities loaned, minimum percent of fair value required as collateral	102.00%			102.00%
Securities loaned, cash collateral	$ 28,000,000			$ 28,000,000			36,000,000
Repurchase agreement balance	0			0			1,012,000,000
Interest expense	49,000,000	29,000,000	[2]	$ 150,000,000	73,000,000	[2]
Minimum
Summary of Investment Holdings [Line Items]
Deferral of interest and principal payments, period, COVID-19				6 months
Maximum
Summary of Investment Holdings [Line Items]
Deferral of interest and principal payments, period, COVID-19				14 months
Commercial mortgage loans
Summary of Investment Holdings [Line Items]
Mortgage loans, allowance for credit loss	$ 195,000,000			$ 195,000,000			91,000,000
Financing receivables, collateralized by properties, number of states | state	37			37
Residential mortgage loans
Summary of Investment Holdings [Line Items]
Mortgage loans, allowance for credit loss	$ 5,000,000			$ 5,000,000			4,000,000
Financing receivables, collateralized by properties, number of states | state	50			50
Unconsolidated VIEs
Summary of Investment Holdings [Line Items]
Equity securities	$ 19,000,000			$ 19,000,000			28,000,000
Corporate securities | Single corporate obligor
Summary of Investment Holdings [Line Items]
Debt securities, unrealized loss	$ 63,000,000			$ 63,000,000			$ 57,000,000
Corporate securities, utilities
Summary of Investment Holdings [Line Items]
Debt securities, unrealized losses, percentage	18.00%			18.00%
Corporate securities, healthcare
Summary of Investment Holdings [Line Items]
Debt securities, unrealized losses, percentage	10.00%			10.00%
Corporate securities, financial services
Summary of Investment Holdings [Line Items]
Debt securities, unrealized losses, percentage							16.00%
Corporate securities, consumer goods
Summary of Investment Holdings [Line Items]
Debt securities, unrealized losses, percentage							10.00%
Equity securities
Summary of Investment Holdings [Line Items]
Unrealized gains (losses)	$ (16,000,000)	(17,000,000)		$ (38,000,000)	(48,000,000)
Federal Home Loan Bank capital stock
Summary of Investment Holdings [Line Items]
Other invested assets	108,000,000			108,000,000			$ 146,000,000
Real estate
Summary of Investment Holdings [Line Items]
Other invested assets	224,000,000			224,000,000			237,000,000
Real estate, foreclosed properties
Summary of Investment Holdings [Line Items]
Other invested assets	2,000,000			2,000,000			0
Limited partnerships
Summary of Investment Holdings [Line Items]
Other invested assets	3,221,000,000			3,221,000,000			$ 3,212,000,000
Repurchase agreements
Summary of Investment Holdings [Line Items]
Interest expense	$ 16,000,000	$ 0		$ 41,000,000	$ 0
Below investment grade or not rated
Summary of Investment Holdings [Line Items]
Debt securities, unrealized losses, percentage	20.00%			20.00%			21.00%

[1] (1) Recast for the adoption of ASU 2018-12. See Notes 1 and 2 to the Condensed Consolidated Financial Statements.

[2] (1) Recast for the adoption of ASU 2018-12. See Notes 1 and 2 to the Condensed Consolidated Financial Statements.