Summary of Significant Accounting Policies - Adoption on Consolidated Condensed Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets	$ 4,147	$ 4,014
Total assets	79,197	75,567
Claim and claim adjustment expense	23,304	22,120	$ 21,269	$ 19,862
Future policy benefits	13,959	13,480	18,010	19,132
Total liabilities	62,672	60,366
Retained earnings	15,617	14,931
Accumulated other comprehensive loss	(2,497)	(3,320)
Noncontrolling interests	821	852
Total equity	$ 16,525	15,201	$ 17,471	16,835
As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets		3,941
Total assets		75,494
Claim and claim adjustment expense		25,099
Future policy benefits		10,151		13,318
Total liabilities		60,016
Retained earnings		15,144
Accumulated other comprehensive loss		(3,284)
Noncontrolling interests		880
Total equity		15,478		$ 19,181
Effect of Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets		73
Total assets		73
Claim and claim adjustment expense		(2,979)
Future policy benefits		3,329
Total liabilities		350
Retained earnings		(213)
Accumulated other comprehensive loss		(36)
Noncontrolling interests		(28)
Total equity		$ (277)