Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Anticipated amounts due from insureds related to losses under deductible policies	$ 1,300	$ 1,200
Structured settlement annuities, interest rate, low end	6.60%	6.40%
Discounted reserves for unfunded structured settlements	$ 444	$ 465
Discounted reserves for unfunded structure settlements, discount amount	535	559
Amount of interest recognized on the discounted reserves of unfunded structured settlements	$ 33	$ 34	$ 36
Interest rates at which workers' compensation lifetime claim reserves are discounted at	3.50%	3.50%
Workers' compensation liability	$ 179	$ 196
Amount of interest accretion recognized on the discounted reserves of workers’ compensation lifetime claim reserves	$ 6	9	$ 9
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	$ 86	$ 84
Percentage of billed receivables compared to total reinsurance receivable	6.00%
Policyholder dividends, rate on policy earnings	2.00%	2.00%	2.00%
Foreign currency transaction gain (loss), before tax	$ (8)	$ 9	$ (22)
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	1	1
Interest paid, net	$ 122	$ 124	$ 109
Income taxes paid	281	282	$ 277
Workers' Compensation Insurance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Short-duration contracts, discounted liabilities, amount	$ 80	$ 88
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%