Policyholder Account Balances, Future Policy Benefits and Claims - Amounts Recognized in Statement of Operations (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022	Dec. 31, 2021
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	$ 490	$ 530	$ 528
Interest Expense	290	390	398
Life contingent payout annuities
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	134	45	39
Interest Expense	36	49	53
Term and whole life insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	126	169	166
Interest Expense	27	39	41
Disability insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	93	127	131
Interest Expense	24	31	30
Long term care insurance
Liability for Future Policy Benefit, Activity [Line Items]
Gross Premiums	137	189	192
Interest Expense	$ 203	$ 271	$ 274