Summary Of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) subsidiary reporting_locations independent_insurance_agency state $ / shares	Dec. 31, 2022 USD ($) $ / shares	Dec. 31, 2021 USD ($) $ / shares	Dec. 31, 2008	Dec. 31, 2020 USD ($)
Significant Accounting Policies
Income Tax Examination, Penalties Expense	$ 0
Number of operating subsidaries | subsidiary	2
Number of independent insurance agencies | independent_insurance_agency	2,080
Number of reporting locations | reporting_locations	3,116
Number of states in which entity operates | state	46
Excess (deficit) of Separate Account Fair Value over (under) Contract Holder Account Value	$ (43,000,000)	$ (64,000,000)
Other invested assets	577,000,000	452,000,000
Depreciation expense	30,000,000	33,000,000	$ 33,000,000
Land, building and equipment impairments	0	0	0
Premium Receivable, Allowance for Credit Loss	16,000,000	13,000,000	14,000,000
Minimum participant age to elect				40 years
Reinsurance recoverable	651,000,000	665,000,000
Prepaid reinsurance premiums	55,000,000	51,000,000
Deferred policy acquisition costs	1,093,000,000	1,013,000,000	916,000,000		$ 838,000,000
Total assets	32,769,000,000	29,732,000,000
Life policy and investment contract reserves	3,068,000,000	3,015,000,000
Deferred federal income tax	1,324,000,000	1,054,000,000
Total liabilities	20,671,000,000	19,170,000,000
Retained earnings	13,084,000,000	11,711,000,000
Accumulated other comprehensive income	(435,000,000)	(614,000,000)
Total shareholders' equity	12,098,000,000	10,562,000,000	12,764,000,000
Total liabilities and shareholders' equity	32,769,000,000	29,732,000,000
Earned premiums	7,958,000,000	7,225,000,000	6,478,000,000
Insurance losses and contract holders' benefits	5,274,000,000	5,019,000,000	3,909,000,000
Underwriting, acquisition and insurance expenses	2,384,000,000	2,162,000,000	1,946,000,000
Deferred	223,000,000	(355,000,000)	483,000,000
Net Income (Loss)	1,843,000,000	(487,000,000)	2,968,000,000
Change in life policy reserves, reinsurance recoverable and other, net of tax (benefit) of $(8), $99 and $24, respectively	(34,000,000)	374,000,000	92,000,000
Other Comprehensive Income (Loss), Net of Tax	179,000,000	(911,000,000)	(38,000,000)
Comprehensive Income (Loss)	$ 2,022,000,000	$ (1,398,000,000)	$ 2,930,000,000
Net income (loss)—basic | $ / shares	$ 11.74	$ (3.06)	$ 18.43
Net income (loss)—diluted | $ / shares	$ 11.66	$ (3.06)	$ 18.24
Accounting Standards Update 2018-12
Significant Accounting Policies
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest		$ 31,000,000
Reinsurance recoverable		665,000,000			287,000,000
Prepaid reinsurance premiums		51,000,000
Deferred policy acquisition costs		1,013,000,000			296,000,000
Total assets		29,732,000,000
Life policy and investment contract reserves		3,015,000,000
Deferred federal income tax		1,054,000,000
Total liabilities		19,170,000,000
Retained earnings		11,711,000,000
Accumulated other comprehensive income		(614,000,000)
Total shareholders' equity		10,562,000,000
Total liabilities and shareholders' equity		29,732,000,000
Earned premiums		7,225,000,000	$ 6,478,000,000
Insurance losses and contract holders' benefits		5,019,000,000	3,909,000,000
Underwriting, acquisition and insurance expenses		2,162,000,000	1,946,000,000
Deferred		(355,000,000)	483,000,000
Net Income (Loss)		(487,000,000)	2,968,000,000
Change in life policy reserves, reinsurance recoverable and other, net of tax (benefit) of $(8), $99 and $24, respectively		374,000,000	92,000,000
Other Comprehensive Income (Loss), Net of Tax		(911,000,000)	(38,000,000)
Comprehensive Income (Loss)		$ (1,398,000,000)	$ 2,930,000,000
Net income (loss)—basic | $ / shares		$ (3.06)	$ 18.43
Net income (loss)—diluted | $ / shares		$ (3.06)	$ 18.24
Accounting Standards Update 2018-12 | Previously Reported
Significant Accounting Policies
Reinsurance recoverable		$ 640,000,000			217,000,000
Prepaid reinsurance premiums		79,000,000
Deferred policy acquisition costs		1,014,000,000			263,000,000
Total assets		29,736,000,000
Life policy and investment contract reserves		3,059,000,000
Deferred federal income tax		1,045,000,000
Total liabilities		19,205,000,000
Retained earnings		11,702,000,000
Accumulated other comprehensive income		(636,000,000)
Total shareholders' equity		10,531,000,000
Total liabilities and shareholders' equity		29,736,000,000
Earned premiums		7,219,000,000	$ 6,482,000,000
Insurance losses and contract holders' benefits		5,012,000,000	3,936,000,000
Underwriting, acquisition and insurance expenses		2,162,000,000	1,951,000,000
Deferred		(355,000,000)	477,000,000
Net Income (Loss)		(486,000,000)	2,946,000,000
Change in life policy reserves, reinsurance recoverable and other, net of tax (benefit) of $(8), $99 and $24, respectively		(1,000,000)	(9,000,000)
Other Comprehensive Income (Loss), Net of Tax		(1,284,000,000)	(121,000,000)
Comprehensive Income (Loss)		$ (1,770,000,000)	$ 2,825,000,000
Net income (loss)—basic | $ / shares		$ (3.06)	$ 18.29
Net income (loss)—diluted | $ / shares		$ (3.06)	$ 18.10
Accounting Standards Update 2018-12 | Effect of Modified Retrospective Application Accounting Standards Update 2018-12
Significant Accounting Policies
Reinsurance recoverable		$ 25,000,000
Prepaid reinsurance premiums		(28,000,000)
Deferred policy acquisition costs		(1,000,000)			$ 33,000,000
Total assets		(4,000,000)
Life policy and investment contract reserves		(44,000,000)
Deferred federal income tax		9,000,000
Total liabilities		(35,000,000)
Retained earnings		9,000,000
Accumulated other comprehensive income		22,000,000
Total shareholders' equity		31,000,000
Total liabilities and shareholders' equity		(4,000,000)
Earned premiums		6,000,000	$ (4,000,000)
Insurance losses and contract holders' benefits		7,000,000	(27,000,000)
Underwriting, acquisition and insurance expenses		0	(5,000,000)
Deferred		0	6,000,000
Net Income (Loss)		(1,000,000)	22,000,000
Change in life policy reserves, reinsurance recoverable and other, net of tax (benefit) of $(8), $99 and $24, respectively		(373,000,000)	(83,000,000)
Other Comprehensive Income (Loss), Net of Tax		373,000,000	83,000,000
Comprehensive Income (Loss)		$ 372,000,000	$ 105,000,000
Net income (loss)—basic | $ / shares		$ 0	$ 0.14
Net income (loss)—diluted | $ / shares		$ 0	$ 0.14
Minimum [Member]
Significant Accounting Policies
Estimated useful lives	3 years
Maximum
Significant Accounting Policies
Estimated useful lives	39 years 6 months
Life Policy Loans
Significant Accounting Policies
Other invested assets	$ 33,000,000	$ 31,000,000
Venture Capital Funds
Significant Accounting Policies
Other invested assets	434,000,000	337,000,000
Real Estate Investment
Significant Accounting Policies
Other invested assets	66,000,000	47,000,000
Other than Securities Investment
Significant Accounting Policies
Other invested assets	$ 44,000,000	$ 37,000,000
10 Largest States
Significant Accounting Policies
Percentage Of Premiums	50.10%	50.10%
Ohio, Largest State
Significant Accounting Policies
Percentage Of Premiums	13.40%	13.40%
Illinois, New York, North Carolina, Pennsylvania and Georgia | Minimum [Member]
Significant Accounting Policies
Percentage Of Premiums	4.00%
Illinois, New York, North Carolina, Pennsylvania and Georgia | Maximum
Significant Accounting Policies
Percentage Of Premiums	6.00%
Largest Single Agency Relationship
Significant Accounting Policies
Percentage Of Premiums	0.60%
All Other | Maximum
Significant Accounting Policies
Percentage Of Premiums	6.00%
Stock Options
Significant Accounting Policies
Weighted-average remaining contractual life for options expected to vest	10 years
Property Casualty Insurance Segment
Significant Accounting Policies
Number of operating subsidaries | subsidiary	2
Stock Options
Significant Accounting Policies
Awards vesting period	3 years
Restricted Stock Units (RSUs)
Significant Accounting Policies
Awards vesting period	3 years
Cincinnati Global
Significant Accounting Policies
Goodwill	$ 30,000,000	$ 30,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets	$ 31,000,000	$ 31,000,000
Broker Relationships and Internally developed technology | Cincinnati Global | Minimum [Member]
Significant Accounting Policies
Useful life	5 years
Broker Relationships and Internally developed technology | Cincinnati Global | Maximum
Significant Accounting Policies
Useful life	15 years