Future Policy Benefits - Summary Balances and Changes in the Present Value of Expected Net Premiums and Present Value of FPB (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Net liability for future policy benefits	$ 5,823	$ 5,021	$ 4,918
Less: Reinsurance recoverable				$ 1,115
Traditional Life
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Balance, beginning of year	797	1,020	1,152
Beginning balance at original discount rate	974	1,045	1,131
Effect of actual variances from expected experience		6	33	25
Balance adjusted for variances from expectation		980	1,078	1,156
Interest accrual	14	20	22
Net premiums collected	(89)	(124)	(133)
Ending Balance at original discount rate	905	974	1,045
Effect of changes in discount rate assumptions	196	177	25
Balance, end of year	709	797	1,020
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance, beginning of year	2,151	2,772	3,105
Beginning balance of original discount rate	2,665	2,806	2,995
Effect of actual variances from expected experience		(16)	13	(14)
Balance adjusted for variances from expectation		2,649	2,819	2,981
Interest accrual	42	59	62
Benefits payments	(152)	(213)	(237)
Ending Balance at original discount rate	2,539	2,665	2,806
Effect of changes in discount rate assumptions	(558)	(514)	(34)
Balance, end of year	1,981	2,151	2,772
Net liability for future policy benefits	1,272	1,354	1,752
Less: Reinsurance recoverable	463	612	749	793
Net liability for future policy benefits, after reinsurance recoverable	$ 809	$ 742	$ 1,003
Weighted-average duration of liability for future policyholder benefits (years)	7 years 4 months 9 days	7 years 6 months 29 days	8 years 6 months 14 days
Immediate annuities
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance, beginning of year	$ 1,429	$ 1,954	$ 2,153
Beginning balance of original discount rate	1,858	1,935	2,040
Effect of changes in cash flow assumptions		0	0
Effect of actual variances from expected experience		(13)	(26)	(47)
Balance adjusted for variances from expectation		1,845	1,909	1,993
Issuances	17	26	18
Interest accrual	42	60	60
Benefits payments	(96)	(137)	(136)
Ending Balance at original discount rate	1,808	1,858	1,935
Effect of changes in discount rate assumptions	(495)	429	(19)
Balance, end of year	1,313	1,429	1,954
Net liability for future policy benefits	1,313	1,429	1,954
Less: Reinsurance recoverable	110	118	145	322
Net liability for future policy benefits, after reinsurance recoverable	$ 1,203	$ 1,311	$ 1,809
Weighted-average duration of liability for future policyholder benefits (years)	12 years 5 months 19 days	11 years 9 months 3 days	13 years 7 months 9 days
PRT
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance, beginning of year	$ 2,165	$ 1,148	$ 0
Beginning balance of original discount rate	2,475	1,151	0
Effect of changes in cash flow assumptions		(7)	(20)
Effect of actual variances from expected experience		4	2	0
Balance adjusted for variances from expectation		2,472	1,133	$ 0
Issuances	1,237	1,418	1,155
Interest accrual	79	50	2
Benefits payments	(183)	(126)	(6)
Ending Balance at original discount rate	3,605	2,475	1,151
Effect of changes in discount rate assumptions	(453)	310	3
Balance, end of year	3,152	2,165	1,148
Net liability for future policy benefits	3,152	2,165	1,148
Less: Reinsurance recoverable	0	0	0
Net liability for future policy benefits, after reinsurance recoverable	$ 3,152	$ 2,165	$ 1,148
Weighted-average duration of liability for future policyholder benefits (years)	8 years 2 months 23 days	8 years 1 month 2 days	8 years 9 months