Summary of Significant Accounting Policies - Securities Loaned and Recognition of Premium Revenues and Contract Charges, and Related Benefits and Interest Credited (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Securities loaned
Cash collateral received as percentage of fair value of domestic securities loaned (as a percent)	102.00%
Cash collateral received as a percent of fair value of foreign securities loaned (as a percent)	105.00%
Deferred Policy Acquisition and Sales Inducement Costs
Decrease in unearned premiums	$ (2,294)	$ (2,385)	$ (2,539)
Unearned premium, year one	1,980
Unearned premium, year two	1,480
Unearned premium, thereafter	1,930
Property and casualty insurance premiums | Protection Services
Deferred Policy Acquisition and Sales Inducement Costs
Decrease in unearned premiums	$ 1,840	$ 1,740
Minimum | Personal Lines
Deferred Policy Acquisition and Sales Inducement Costs
Property and casualty insurance contract, terms	6 months
Minimum | Protection Plans and Other Contracts
Deferred Policy Acquisition and Sales Inducement Costs
Period for amortization of DAC for property-liability insurance	1 year
Maximum
Securities loaned
Securities lending transactions length (in days)	30 days
Maximum | Personal Lines
Deferred Policy Acquisition and Sales Inducement Costs
Property and casualty insurance contract, terms	12 months
Maximum | Protection Plans and Other Contracts
Deferred Policy Acquisition and Sales Inducement Costs
Period for amortization of DAC for property-liability insurance	5 years