Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2018-12 [Member]
Anticipated amounts due from insureds related to losses under deductible policies	$ 1,200	$ 1,100
Structured settlement annuities, interest rate, low end	6.40%	6.40%
Discounted reserves for unfunded structured settlements	$ 465	$ 485
Discounted reserves for unfunded structure settlements, discount amount	559	590
Amount of interest recognized on the discounted reserves of unfunded structured settlements	$ 34	$ 36	$ 36
Interest rates at which workers' compensation lifetime claim reserves are discounted at	3.50%	3.50%
Workers' compensation liability	$ 196	$ 211
Amount of interest accretion recognized on the discounted reserves of workers’ compensation lifetime claim reserves	$ 9	9	$ 12
Future policy benefit reserves, cash flows projected to occur beyond tenor with market-observable rates available, grading period	10 years
Liability balance for guaranty fund	$ 84	$ 74
Percentage of billed receivables compared to total reinsurance receivable	5.00%
Policyholder dividends, rate on policy earnings	2.00%	2.00%	1.00%
Foreign currency transaction gain (loss), before tax	$ 9	$ (22)	$ (1)
Operating lease, right-of-use asset, statement of financial position [Extensible List]	Other assets	Other assets
Operating lease, liability, statement of financial position [Extensible List]	Other liabilities	Other liabilities
Weighted average number diluted shares outstanding adjustment (in shares)	1,000	1,000	1,000
Interest paid, net	$ 124	$ 109	$ 110
Income taxes paid	282	277	$ 278
Workers' Compensation Insurance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Short-duration contracts, discounted liabilities, amount	$ 88	$ 93
Furniture and Fixtures
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, useful life	7 years
Office Equipment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, useful life	5 years
Computer Software, Intangible Asset
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, useful life	10 years
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Warranty coverage term	1 month
Requisite service period for stock- based compensation expense	3 years
Minimum | Computer Software, Intangible Asset
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, useful life	3 years
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Warranty coverage term	10 years
Maximum | Computer Software, Intangible Asset
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property, plant and equipment, useful life	5 years
CNAF Consolidated | Loews
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Noncontrolling interest, ownership percentage by parent	92.00%