Statutory Accounting Information (Schedule Of Statutory Net Income And Statutory Surplus (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
The Cincinnati Insurance Company
Statutory Accounting Practices
SAP net income (loss)	$ 558	$ 626	$ 401
Capital and surplus	5,620	4,919
The Cincinnati Casualty Company
Statutory Accounting Practices
SAP net income (loss)	13	16	21
Capital and surplus	437	398
The Cincinnati Indemnity Company
Statutory Accounting Practices
SAP net income (loss)	3	5	4
Capital and surplus	111	102
The Cincinnati Specialty Underwriters Insurance Company
Statutory Accounting Practices
SAP net income (loss)	62	69	58
Capital and surplus	526	479
The Cincinnati Life Insurance Company
Statutory Accounting Practices
SAP net income (loss)	19	0	$ 12
Capital and surplus	$ 204	$ 191