Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) shares in Thousands, $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings			$ 9,663	$ 9,081
Mortgage loans on real estate commercial and consumer allowance for credit loss			16	26
Deferred income taxes			142	66
Marketable securities fixed maturities allowance for credit loss			18	40
Anticipated amounts due from insureds related to losses under deductible policies			$ 1,100	$ 1,200
Structured settlement annuities, interest rate, low end			6.40%
Structured settlement annuities, interest rate, high end				6.50%
Discounted reserves for unfunded structured settlements			$ 503	$ 520
Discounted reserves for unfunded structure settlements, discount amount			621	657
Amount of interest recognized on the discounted reserves of unfunded structured settlements			$ 36	$ 35	$ 36
Interest rates at which workers' compensation lifetime claim reserves are discounted at			3.50%	3.50%
Workers' compensation liability			$ 228	$ 258
Discounted reserves for workers’ compensation lifetime claim reserves, discount amount			97	113
Amount of interest accretion recognized on the discounted reserves of workers’ compensation lifetime claim reserves			$ 12	$ 15	$ 21
Long term care claim reserves weighted average discounted interest rate			5.80%	5.80%
Discounted reserves for long term care claim reserves			$ 2,700	$ 2,700
Premium deficiency			$ 428	$ 439
Liability for future policy benefits, gross premium valuation, pretax margin	$ 72	$ 72
Minimum interest rate used to calculate reserves for long term care products			5.30%	5.40%
Liability balance for guaranty fund			$ 79	$ 82
Percentage of billed receivables compared to total reinsurance receivable			5.00%
Policyholder dividends, rate on policy earnings			1.00%	1.00%	1.00%
Increase (decrease) in shadow adjustment, net of tax			$ (296)	$ 575
Reduction of net unrealized gains on investments included in AOCI due to shadow adjustments			2,477	2,773
Foreign currency transaction gain (loss), before tax			$ (1)	$ 13	$ 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	770	960
Antidilutive securities excluded from computation of earnings per share, amount			1	8	1
Interest paid, net			$ 110	$ 124	$ 136
Income taxes paid			$ 278	$ 108	$ 255
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
ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings						$ (5)
Mortgage loans on real estate commercial and consumer allowance for credit loss						7
Deferred income taxes						2
Marketable securities fixed maturities allowance for credit loss						$ 6
CNAF Consolidated | Loews
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Noncontrolling interest, ownership percentage by parent			89.60%