Claim and Claim Adjustment Expense Reserves and Future Policy Benefit Reserves (Gross and Net Carried Claim and Claim Adjustment Expense Reserves) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Liability for Claims and Claims Adjustment Expense [Line Items]
Gross Case Reserves	$ 10,387		$ 10,555
Gross IBNR Reserves	14,712	$ 107	13,619
Total Gross Carried Claim and Claim Adjustment Expense Reserves	25,099		24,174	$ 22,706	$ 21,720
Net Case Reserves	8,319		8,369
Net IBNR Reserves	11,589		10,836
Total Net Carried Claim and Claim Adjustment Expense Reserves	19,908		19,205	$ 18,701	$ 17,885
Specialty
Liability for Claims and Claims Adjustment Expense [Line Items]
Gross Case Reserves	1,529		1,578
Gross IBNR Reserves	5,349		4,855
Total Gross Carried Claim and Claim Adjustment Expense Reserves	6,878		6,433
Net Case Reserves	1,310		1,338
Net IBNR Reserves	4,253		3,927
Total Net Carried Claim and Claim Adjustment Expense Reserves	5,563		5,265
Commercial
Liability for Claims and Claims Adjustment Expense [Line Items]
Gross Case Reserves	3,156		3,184
Gross IBNR Reserves	6,239		5,706
Total Gross Carried Claim and Claim Adjustment Expense Reserves	9,395		8,890
Net Case Reserves	2,809		2,850
Net IBNR Reserves	5,621		5,215
Total Net Carried Claim and Claim Adjustment Expense Reserves	8,430		8,065
International
Liability for Claims and Claims Adjustment Expense [Line Items]
Gross Case Reserves	817		859
Gross IBNR Reserves	1,586		1,421
Total Gross Carried Claim and Claim Adjustment Expense Reserves	2,403		2,280
Net Case Reserves	686		744
Net IBNR Reserves	1,317		1,196
Total Net Carried Claim and Claim Adjustment Expense Reserves	2,003		1,940
Life & Group
Liability for Claims and Claims Adjustment Expense [Line Items]
Gross Case Reserves	3,457		3,383
Gross IBNR Reserves	217		371
Total Gross Carried Claim and Claim Adjustment Expense Reserves	3,674		3,754
Net Case Reserves	3,377		3,291
Net IBNR Reserves	196		350
Total Net Carried Claim and Claim Adjustment Expense Reserves	3,573		3,641
Corporate & Other
Liability for Claims and Claims Adjustment Expense [Line Items]
Gross Case Reserves	1,428		1,551
Gross IBNR Reserves	1,321		1,266
Total Gross Carried Claim and Claim Adjustment Expense Reserves	2,749		2,817
Net Case Reserves	137		146
Net IBNR Reserves	202		148
Total Net Carried Claim and Claim Adjustment Expense Reserves	$ 339		$ 294