Condensed Financial Statements of Parent Company Condensed Statements of Cash Flows (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 166	$ 377	$ 432
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	42	41	38
Total realized investment gains (losses), net	(70)	(159)	(336)
Changes in:
Investment income receivable		(1)	(20)
Deferred income taxes	(25)	(73)	5
Other assets	2	3	10
Other liabilities	(49)	(18)	5
Net cash (used in) provided by operating activities	247	531	525
CASH FLOWS FROM INVESTING ACTIVITIES
Sale of fixed-maturities	71	199	187
Call or maturity of fixed maturities	808	886	659
Sale of equity securities	539	273	1,247
Purchase of fixed maturities	(1,087)	(1,483)	(2,135)
Purchase of equity securities	(337)	(396)	(796)
Change in short-term investments, net		7	78
Investment in buildings and equipment, net	(7)	(17)	(42)
Change in other invested assets, net	7		(9)
Net cash provided by investing activities	(8)	(529)	(815)
CASH FLOWS FROM FINANCING ACTIVITIES
Increase in notes payable	55
Payment of cash dividends to shareholders	(255)	(252)	(249)
Proceeds from stock options exercised	1
Other	(11)	(10)	(9)
Net cash used in financing activities	(186)	(174)	(162)
Net decrease in cash and cash equivalents	53	(172)	(452)
Cash and cash equivalents at beginning of year	385	557	1,009
Cash and cash equivalents at end of period	438	385	557
Cincinnati Financial Corporation
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	166	377	432
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7	7	8
Total realized investment gains (losses), net	(15)	(17)	(135)
Dividends from subsidiaries	180	220	50
Changes in:
Increase in equity of subsidiaries	(165)	(374)	(352)
Investment income receivable	1		(1)
Current federal income taxes	25	3	(104)
Deferred income taxes	(10)	2	24
Other assets	2		(2)
Other liabilities	(23)	(12)	(22)
Net cash (used in) provided by operating activities	168	206	(102)
CASH FLOWS FROM INVESTING ACTIVITIES
Sale of fixed-maturities	5	32	22
Call or maturity of fixed maturities	13	21	15
Sale of equity securities	101	85	408
Purchase of fixed maturities		(27)	(206)
Purchase of equity securities	(78)	(92)	(246)
Change in short-term investments, net			65
Investment in buildings and equipment, net	(1)		(1)
Change in other invested assets, net	5		(5)
Net cash provided by investing activities	45	19	52
CASH FLOWS FROM FINANCING ACTIVITIES
Increase in notes payable	55
Payment of cash dividends to shareholders	(255)	(252)	(249)
Purchase of treasury shares	(32)	(10)	1
Proceeds from stock options exercised	(4)	(2)
Net transfers to subsidiaries	2	21	8
Other	3	2
Net cash used in financing activities	(231)	(241)	(240)
Net decrease in cash and cash equivalents	(18)	(16)	(290)
Cash and cash equivalents at beginning of year	38	54	344
Cash and cash equivalents at end of period	$ 20	$ 38	$ 54