Statutory Accounting Information (Schedule Of Statutory Net Income And Statutory Surplus (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
The Cincinnati Insurance Company
Statutory Accounting Practices
SAP net income (loss)	$ 534	$ 436	$ 418
Capital and surplus	4,412	4,472
The Cincinnati Casualty Company
Statutory Accounting Practices
SAP net income (loss)	12	12	10
Capital and surplus	337	330
The Cincinnati Indemnity Company
Statutory Accounting Practices
SAP net income (loss)	3	3	2
Capital and surplus	88	86
The Cincinnati Specialty Underwriters Insurance Company
Statutory Accounting Practices
SAP net income (loss)	49	32	18
Capital and surplus	306	266
The Cincinnati Life Insurance Company
Statutory Accounting Practices
SAP net income (loss)	(11)	(19)	$ (20)
Capital and surplus	$ 208	$ 223