Insurance Liabilities - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Liability for Future Policy Benefit, by Product Segment [Line Items]
Contractual deductible recoverable amount	$ 12,100	$ 12,100
Collateral held for deductible recoverable amounts	8,700	8,600
Liability for unpaid losses and loss adjustment expenses, allowance for credit losses	14	14
Prior years, excluding discount and amortization of deferred gain	392	530	$ 171
Net loss reserve discount	$ 1,233	1,278
Tabular discount rate (as a percent)	45.00%
Workers compensation tabular discount amount	$ 294	314
Workers compensation non tabular discount amount	939	964
Net loss reserve discount benefit (charge)	(195)	703	193
Net borrowing capacity under FHLB	3,700
Borrowings pledged as collateral to FHLB	$ 8,700
New York
Liability for Future Policy Benefit, by Product Segment [Line Items]
Nontabular discount rate (as a percent)	5.00%
NICO
Liability for Future Policy Benefit, by Product Segment [Line Items]
Amortization of deferred gain on retroactive reinsurance	$ 48	$ 189	$ 137
Participating Life business | Reinsurance Recoverable for Paid and Unpaid Claims and Claims Adjustments | Reinsurer Concentration Risk [Member]
Liability for Future Policy Benefit, by Product Segment [Line Items]
Concentration risk (as a percent)	0.50%	0.70%
Participating Life business | Reinsurance Recoverable Including Reinsurance Premium Paid | Reinsurer Concentration Risk [Member]
Liability for Future Policy Benefit, by Product Segment [Line Items]
Concentration risk (as a percent)	0.90%	1.30%	1.70%
Term Life Insurance
Liability for Future Policy Benefit, by Product Segment [Line Items]
Increase in reserves	$ (1)	$ 26	$ 15