LIABILITIES FOR FUTURE POLICYHOLDER BENEFITS - Policyholder Account Balance (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	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	$ 15,929		$ 15,935
Less: Reinsurance recoverable					$ (2,209)
Net liability for future policy benefits, after reinsurance recoverable					6,252
Term
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Net liability for future policy benefits	1,258		1,359
Term | Protection Solutions
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Less: Reinsurance recoverable					(372)
Net liability for future policy benefits, after reinsurance recoverable					$ 1,602
Payout - Non-Legacy
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Net liability for future policy benefits	789		828
Payout - Legacy
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Net liability for future policy benefits	3,192		2,689
Group Pension
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Net liability for future policy benefits	475		523
Health
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Net liability for future policy benefits	1,437		1,560
Operating Segments | Term | Protection Solutions
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Balance, beginning of period	2,090	$ 2,472
Beginning balance at original discount rate	2,069	1,854
Effect of changes in cash flow assumptions			32	$ 204
Effect of actual variances from expected experience			(13)	37
Adjusted beginning of period balance			2,088	2,095
Issuances	49	63
Interest accrual	75	72
Net premiums collected	(147)	(143)
Ending Balance at original discount rate	2,065	2,087
Effect of changes in discount rate assumptions	(82)	(6)
Balance, end of period	1,983	2,081
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance, beginning of period	3,449	4,274
Beginning balance of original discount rate	3,376	3,225
Effect of changes in cash flow assumptions	40	222
Effect of actual variances from expected	(15)	40
Adjusted beginning of period balance	3,401	3,487
Issuances	53	67
Interest accrual	126	124
Benefit payments	(253)	(280)
Ending balance at original discount rate	3,327	3,398
Effect of changes in discount rate assumptions	(85)	36
Balance, end of period	3,242	3,434
Net liability for future policy benefits	1,258	1,353
Less: Reinsurance recoverable	(193)	(210)
Net liability for future policy benefits, after reinsurance recoverable	$ 1,065	$ 1,143
Weighted-average duration of liability for future policyholder benefits (years)	7 years 1 month 6 days	7 years 1 month 6 days
Operating Segments | Payout - Non-Legacy | Non-Legacy
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Balance, beginning of period	$ 0	$ 0
Beginning balance at original discount rate	0	0
Effect of changes in cash flow assumptions			0	0
Effect of actual variances from expected experience			0	0
Adjusted beginning of period balance			0	0
Issuances	0	0
Interest accrual	0	0
Net premiums collected	0	0
Ending Balance at original discount rate	0	0
Effect of changes in discount rate assumptions	0	0
Balance, end of period	0	0
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance, beginning of period	828	1,114
Beginning balance of original discount rate	845	883
Effect of changes in cash flow assumptions	0	(2)
Effect of actual variances from expected	0	0
Adjusted beginning of period balance	845	881
Issuances	38	19
Interest accrual	29	30
Benefit payments	(69)	(74)
Ending balance at original discount rate	843	856
Effect of changes in discount rate assumptions	(54)	(26)
Balance, end of period	789	830
Net liability for future policy benefits	789	830
Less: Reinsurance recoverable	(19)	0
Net liability for future policy benefits, after reinsurance recoverable	$ 770	$ 830
Weighted-average duration of liability for future policyholder benefits (years)	9 years 3 months 18 days	9 years 6 months
Operating Segments | Payout - Legacy | Legacy
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Balance, beginning of period	$ 0	$ 0
Beginning balance at original discount rate	0	0
Effect of changes in cash flow assumptions			0	0
Effect of actual variances from expected experience			0	0
Adjusted beginning of period balance			0	0
Issuances	0	0
Interest accrual	0	0
Net premiums collected	0	0
Ending Balance at original discount rate	0	0
Effect of changes in discount rate assumptions	0	0
Balance, end of period	0	0
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance, beginning of period	2,689	2,547
Beginning balance of original discount rate	3,024	2,400
Effect of changes in cash flow assumptions	0	(2)
Effect of actual variances from expected	1	(2)
Adjusted beginning of period balance	3,025	2,396
Issuances	733	556
Interest accrual	65	47
Benefit payments	(199)	(143)
Ending balance at original discount rate	3,624	2,856
Effect of changes in discount rate assumptions	(432)	(373)
Balance, end of period	3,192	2,483
Net liability for future policy benefits	3,192	2,483
Less: Reinsurance recoverable	(999)	(365)
Net liability for future policy benefits, after reinsurance recoverable	$ 2,193	$ 2,118
Weighted-average duration of liability for future policyholder benefits (years)	7 years 8 months 12 days	8 years 2 months 12 days
Corporate and Other | Group Pension
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Balance, beginning of period	$ 0	$ 0
Beginning balance at original discount rate	0	0
Effect of changes in cash flow assumptions			0	0
Effect of actual variances from expected experience			0	0
Adjusted beginning of period balance			0	0
Issuances	0	0
Interest accrual	0	0
Net premiums collected	0	0
Ending Balance at original discount rate	0	0
Effect of changes in discount rate assumptions	0	0
Balance, end of period	0	0
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance, beginning of period	523	683
Beginning balance of original discount rate	583	632
Effect of changes in cash flow assumptions	0	0
Effect of actual variances from expected	0	0
Adjusted beginning of period balance	583	632
Issuances	0	0
Interest accrual	15	16
Benefit payments	(50)	(54)
Ending balance at original discount rate	548	594
Effect of changes in discount rate assumptions	(73)	(65)
Balance, end of period	475	529
Net liability for future policy benefits	475	529
Less: Reinsurance recoverable	0	0
Net liability for future policy benefits, after reinsurance recoverable	$ 475	$ 529
Weighted-average duration of liability for future policyholder benefits (years)	7 years 1 month 6 days	7 years 2 months 12 days
Corporate and Other | Health
Liability for Future Policy Benefit, Expected Net Premium [Roll Forward]
Balance, beginning of period	$ (6)	$ 22
Beginning balance at original discount rate	(6)	19
Effect of changes in cash flow assumptions			(8)	(10)
Effect of actual variances from expected experience			(5)	(12)
Adjusted beginning of period balance			$ (19)	$ (3)
Issuances	0	0
Interest accrual	(1)	0
Net premiums collected	2	1
Ending Balance at original discount rate	(18)	(2)
Effect of changes in discount rate assumptions	1	0
Balance, end of period	(17)	(2)
Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward]
Balance, beginning of period	1,554	2,092
Beginning balance of original discount rate	1,795	1,915
Effect of changes in cash flow assumptions	(12)	(5)
Effect of actual variances from expected	(5)	(10)
Adjusted beginning of period balance	1,778	1,900
Issuances	0	0
Interest accrual	43	46
Benefit payments	(111)	(124)
Ending balance at original discount rate	1,710	1,822
Effect of changes in discount rate assumptions	(290)	(264)
Balance, end of period	1,420	1,558
Net liability for future policy benefits	1,437	1,560
Less: Reinsurance recoverable	(1,145)	(1,248)
Net liability for future policy benefits, after reinsurance recoverable	$ 292	$ 312
Weighted-average duration of liability for future policyholder benefits (years)	8 years 8 months 12 days	8 years 9 months 18 days