Insurance Liabilities - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Jan. 20, 2017
Liability for Future Policy Benefit, by Product Segment [Line Items]
Contractual deductible recoverable amount	$ 12,100		$ 12,100		$ 12,300
Collateral held for deductible recoverable amounts	8,500		8,500		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	374	$ 29	425	$ 13
Net loss reserve discount	939		$ 939		876
Tabular discount rate (as a percent)			45.00%
Workers compensation tabular discount amount	272		$ 272		260
Workers compensation non tabular discount amount	667		667		$ 616
Net loss reserve discount charge	(14)	(22)	6	10
NICO
Liability for Future Policy Benefit, by Product Segment [Line Items]
Amortization of deferred gain on retroactive reinsurance	$ (34)	$ 21	$ 4	$ 76
New York
Liability for Future Policy Benefit, by Product Segment [Line Items]
Nontabular discount rate (as a percent)			5.00%
U.S. Run-Off Long Tail Insurance Lines | Accident Years 2015 and Prior | NICO
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