Reinsurance (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021	Feb. 05, 2021
Ceded Credit Risk [Line Items]
Funds held under reinsurance agreements, liability	$ 3,600	$ 3,700			$ 690
Largest recoverable from single reinsurer	5,412	5,416	[1]
Reinsurance recoveries reported in insurance claims and policyholders' benefits reported on the Consolidated Statement of Operations	2,772	2,631		$ 3,058
Subsidiaries of Berkshire Hathaway Group
Ceded Credit Risk [Line Items]
Largest recoverable from single reinsurer	1,800
Cavello Bay Reinsurance Limited
Ceded Credit Risk [Line Items]
Largest recoverable from single reinsurer	576
Swiss Reinsurance Group
Ceded Credit Risk [Line Items]
Largest recoverable from single reinsurer	410
Significant Captive Program
Ceded Credit Risk [Line Items]
Direct and ceded earned premiums	2,907	3,270		3,638
Reinsurance recoveries reported in insurance claims and policyholders' benefits reported on the Consolidated Statement of Operations	$ 1,512	$ 1,796		$ 2,003

[1] As of January 1, 2023, the Company adopted ASU 2018-12, Financial Services-Insurance (Topic 944): Targeted Improvements to the Accounting for Long-Duration Contracts (ASU 2018-12) using the modified retrospective method applied as of the transition date of January 1, 2021. Prior period amounts in the financial statements have been adjusted to reflect application of the new guidance. See Note A to the Consolidated Financial Statements for additional information.