Condensed Financial Statements of Parent Company Condensed Balance Sheets (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Investments
Fixed maturities, at fair value	$ 8,779	$ 8,383
Equity securities, at fair value	2,956	3,041
Other invested assets	66	84
Cash and cash equivalents	438	385	557	1,009
Investment income receivable	119	119
Land, building and equipment, net, for company use (accumulated depreciation: 2011-$94; 2010-$77)	227	229
Other assets	93	67
Total assets	15,668	15,095
LIABILITIES
Deferred federal income tax	314	260
Long-term debt	790	790
Other liabilities	517	539
Total liabilities	10,613	10,063
SHAREHOLDERS' EQUITY
Common stock	393	393
Paid-in capital	1,096	1,091
Retained earnings	3,885	3,980
Accumulated other comprehensive income	901	769	624	347
Treasury stock at cost	(1,220)	(1,201)
Total shareholders' equity	5,055	5,032	4,760	4,182
Total liabilities and shareholders' equity	15,668	15,095
Cincinnati Financial Corporation
Investments
Fixed maturities, at fair value	225	241
Equity securities, at fair value	806	763
Investment real estate, net		5
Other invested assets	29	39
Cash and cash equivalents	20	38	54	344
Equity in net assets of subsidiaries	4,798	4,695
Investment income receivable	4	5
Land, building and equipment, net, for company use (accumulated depreciation: 2011-$94; 2010-$77)	158	159
Prepaid income tax		15
Other assets	13	15
Due from subsidiaries	65	54
Total assets	6,118	6,029
LIABILITIES
Dividends declared but unpaid	65	65
Deferred federal income tax	40	42
Long-term debt	790	790
Other liabilities	168	100
Total liabilities	1,063	997
SHAREHOLDERS' EQUITY
Common stock	393	393
Paid-in capital	1,096	1,091
Retained earnings	3,885	3,980
Accumulated other comprehensive income	901	769
Treasury stock at cost	(1,220)	(1,201)
Total shareholders' equity	5,055	5,032
Total liabilities and shareholders' equity	$ 6,118	$ 6,029