Insurance Liabilities - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Jan. 20, 2017
Liability for Future Policy Benefit, by Product Segment [Line Items]
Contractual deductible recoverable amount	$ 12,800		$ 12,800		$ 12,100
Collateral held for deductible recoverable amounts	8,800		8,800		8,600
Liability for unpaid losses and loss adjustment expenses, allowance for credit losses	14		14		14
Prior years, excluding discount and amortization of deferred gain	246	$ 112	380	$ 537
Net loss reserve discount	1,313		$ 1,313		1,278
Tabular discount rate (as a percent)			45.00%
Workers compensation tabular discount amount	316		$ 316		314
Workers compensation non tabular discount amount	997		997		$ 964
Net loss reserve discount charge	(5)	(10)	$ (85)	(4)
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	$ (36)	$ 18	$ 36	22
U.S. Run-Off Long Tail Insurance Lines | NICO | Accident Years 2015 and Prior
Liability for Future Policy Benefit, by Product Segment [Line Items]
Risk Transferred - U.S. Commercial long-tail exposures for accident years 2015 and prior (as a percent)						80.00%
Ceded to NICO percent of paid losses (as a percent)						80.00%
Ceded to NICO net paid losses in excess						$ 25,000
Ceded to NICO net paid losses in excess, aggregate limit						25,000
NICO's limit of liability under the contract						20,000
Consideration paid, including interest						$ 10,200
Term Life Insurance
Liability for Future Policy Benefit, by Product Segment [Line Items]
Increase in reserves			$ (1)	$ 11