Condensed Financial Statements Of Parent Company Condensed Statements Of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flows From Operating Activities
Net Income	$ 100	$ 180	$ 123	$ 188	$ 156	$ 174	$ 176	$ 128	$ 591	$ 634	$ 525
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									48	52	51
Realized investment gains, net									(124)	(70)	(133)
Changes in:
Investment income receivable									(5)	(6)	(2)
Current income tax receivable/payable									(35)	(18)	2
Other assets									34	(39)	19
Other liabilities									49	44	(11)
Net cash provided by operating activities									1,103	1,064	873
Cash Flows From Investing Activities
Sale of fixed maturities									15	43	26
Call or maturity of fixed maturities									1,511	1,199	1,019
Sale of equity securities									465	342	335
Purchase of fixed maturities									(1,994)	(1,722)	(1,312)
Purchase of equity securities									(439)	(493)	(392)
Investment in buildings and equipment, net									(13)	(10)	(9)
Change in other invested assets, net									(14)	1	9
Net cash used by investing activities									(456)	(624)	(311)
Cash Flows From Financing Activities
Payments of note payable									(15)	(14)	(55)
Payment of cash dividends to shareholders									(306)	(366)	(278)
Shares acquired - share repurchase authorization									(39)	(53)	(21)
Proceeds from stock options exercised									21	24	22
Other									(20)	(17)	(17)
Net cash used in financing activities									(414)	(487)	(404)
Net change in cash and cash equivalents									233	(47)	158
Cash and cash equivalents at beginning of year				544				591	544	591	433
Cash and cash equivalents at end of year	777				544				777	544	591
Cincinnati Financial Corporation
Cash Flows From Operating Activities
Net Income									591	634	525
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									6	7	7
Realized investment gains, net									(27)	19	(34)
Dividends from subsidiaries									475	447	400
Changes in:
Increase in equity of subsidiaries									(566)	(642)	(504)
Investment income receivable									(2)	0	(1)
Current federal income taxes									(4)	(7)	3
Current income tax receivable/payable									8	(10)	(6)
Other assets									(4)	(3)	20
Other liabilities									(1)	13	(14)
Intercompany receivable for operations									20	16	22
Net cash provided by operating activities									496	474	418
Cash Flows From Investing Activities
Call or maturity of fixed maturities									5	8	4
Sale of equity securities									135	54	112
Purchase of equity securities									(175)	(110)	(225)
Investment in buildings and equipment, net									(2)	0	(2)
Change in other invested assets, net									6	1	4
Net cash used by investing activities									(31)	(47)	(107)
Cash Flows From Financing Activities
Payments of note payable									0	0	(55)
Payment of cash dividends to shareholders									(306)	(366)	(278)
Shares acquired - share repurchase authorization									(39)	(53)	(21)
Proceeds from stock options exercised									21	24	22
Other									1	2	2
Net cash used in financing activities									(323)	(393)	(330)
Net change in cash and cash equivalents									142	34	(19)
Cash and cash equivalents at beginning of year				$ 106				$ 72	106	72	91
Cash and cash equivalents at end of year	$ 248				$ 106				$ 248	$ 106	$ 72