Condensed Financial Statements Of Parent Company Condensed Balance Sheets (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Investments
Fixed maturities, at fair value	$ 9,093	$ 8,779
Equity securities, at fair value	3,373	2,956
Other invested assets	68	66
Cash and cash equivalents	487	438	385	557
Investment income receivable	115	119
Land, building and equipment, net, for company use (accumulated depreciation: 2011-$94; 2010-$77)	217	227
Other assets	61	93
Total assets	16,548	15,635
LIABILITIES
Deferred federal income tax	453	303
Long-term debt	790	790
Other liabilities	660	517
Total liabilities	11,095	10,602
SHAREHOLDERS' EQUITY
Common stock	394	393
Paid-in capital	1,134	1,096
Retained earnings	4,021	3,863
Accumulated other comprehensive income	1,129	901	769	624
Treasury stock at cost	(1,225)	(1,220)
Total shareholders' equity	5,453	5,033	5,012	4,760
Total liabilities and shareholders' equity	16,548	15,635
Land, building and equipment, accumulated depreciation	397	376
Cincinnati Financial Corporation [Member]
Investments
Fixed maturities, at fair value	103	225
Equity securities, at fair value	958	806
Other invested assets	31	29
Cash and cash equivalents	90	20	38	54
Equity in net assets of subsidiaries	5,103	4,776
Investment income receivable	3	4
Land, building and equipment, net, for company use (accumulated depreciation: 2011-$94; 2010-$77)	153	158
Prepaid income tax	14
Other assets	35	13
Due from subsidiaries	75	65
Total assets	6,565	6,096
LIABILITIES
Dividends declared but unpaid	66	65
Deferred federal income tax	63	40
Long-term debt	790	790
Other liabilities	193	168
Total liabilities	1,112	1,063
SHAREHOLDERS' EQUITY
Common stock	394	393
Paid-in capital	1,134	1,096
Retained earnings	4,021	3,863
Accumulated other comprehensive income	1,129	901
Treasury stock at cost	(1,225)	(1,220)
Total shareholders' equity	5,453	5,033
Total liabilities and shareholders' equity	$ 6,565	$ 6,096