Statutory Accounting Information (Schedule Of Statutory Net Income And Statutory Surplus (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
The Cincinnati Insurance Company
Statutory Accounting Practices
SAP net income (loss)	$ 626	$ 401	$ 434
Capital and surplus	4,919	5,094
The Cincinnati Casualty Company
Statutory Accounting Practices
SAP net income (loss)	16	21	11
Capital and surplus	398	392
The Cincinnati Indemnity Company
Statutory Accounting Practices
SAP net income (loss)	5	4	4
Capital and surplus	102	100
The Cincinnati Specialty Underwriters Insurance Company
Statutory Accounting Practices
SAP net income (loss)	69	58	57
Capital and surplus	479	436
The Cincinnati Life Insurance Company
Statutory Accounting Practices
SAP net income (loss)	0	12	$ 2
Capital and surplus	$ 191	$ 195