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Summary Of Significant Accounting Policies (Narrative) (Details)		12 Months Ended
	Feb. 28, 2019	Dec. 31, 2019 USD ($) state subsidiary independent_insurance_agency reporting_locations	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2008
Significant Accounting Policies
Unrealized gains reclassified to retained earnings for ASU 2016-01, after tax			$ 2,503,000,000
Income Tax Examination, Penalties Expense		$ 0
Number of operating subsidaries \| subsidiary		2
Number of independent insurance agencies \| independent_insurance_agency		1,796
Number of reporting locations \| reporting_locations		2,458
Number of states in which entity operates \| state		45
Excess (deficit) of Separate Account Fair Value over (under) Contract Holder Account Value		$ 52,000,000	(3,000,000)
Defined Benefit Plan Qualifying Age					40 years
Other invested assets		296,000,000	123,000,000
Depreciation expense		25,000,000	31,000,000	$ 28,000,000
Land, building and equipment impairments		0	0	0
Total		$ (1,650,000,000)	402,000,000	$ (148,000,000)
Unrealized Gain (Loss) on Investments			404,000,000
Minimum
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		$ 32,000,000	33,000,000
Venture Capital Funds
Significant Accounting Policies
Other invested assets		71,000,000	60,000,000
Real Estate Investment
Significant Accounting Policies
Other invested assets		29,000,000	$ 30,000,000
Other than Securities Investment
Significant Accounting Policies
Other invested assets		$ 164,000,000
10 Largest States
Significant Accounting Policies
Generated percentage of total earned premiums		54.80%	58.40%
Ohio, Largest State
Significant Accounting Policies
Generated percentage of total earned premiums		15.10%	15.90%
Illinois, Georgia, North Carolina, Indiana and Pennsylvania \| Minimum
Significant Accounting Policies
Generated percentage of total earned premiums		4.00%
Illinois, Georgia, North Carolina, Indiana and Pennsylvania \| Maximum
Significant Accounting Policies
Generated percentage of total earned premiums		6.00%
Largest Single Agency Relationship
Significant Accounting Policies
Generated percentage of total earned premiums		1.30%
All Other \| Maximum
Significant Accounting Policies
Generated percentage of total earned premiums		4.00%
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
Broker Relationships and Internally developed technology \| Cincinnati Global \| Minimum
Significant Accounting Policies
Useful life	5 years
Broker Relationships and Internally developed technology \| Cincinnati Global \| Maximum
Significant Accounting Policies
Useful life	15 years