Condensed Financial Statements Of Parent Company Condensed Statements Of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows From Operating Activities
Net Income	$ 626	$ 248	$ 428	$ 695	$ (452)	$ 553	$ 217	$ (31)	$ 1,997	$ 287	$ 1,045
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									72	63	55
Gain (Loss) on Sale of Investments									(1,640)	408	(148)
Changes in:
Investment income receivable									(1)	2	0
Current income tax receivable/payable									92	(91)	67
Other assets									(22)	(1)	(43)
Other liabilities									74	0	24
Net cash provided by operating activities									1,208	1,181	1,052
Cash Flows From Investing Activities
Sale of fixed maturities									102	36	23
Call or maturity of fixed maturities									1,241	1,127	1,172
Sale of equity securities									203	403	523
Purchase of fixed maturities									(1,742)	(1,510)	(1,723)
Purchase of equity securities									(382)	(441)	(513)
Investment in buildings and equipment									(24)	(20)	(16)
Change in other invested assets, net									(72)	(38)	(15)
Net cash used in investing activities									(679)	(451)	(558)
Cash Flows From Financing Activities
Payment of cash dividends to shareholders									(355)	(336)	(400)
Shares acquired - share repurchase authorization									(67)	(125)	(92)
Proceeds from stock options exercised									11	9	13
Other									(54)	(60)	(54)
Net cash used in financing activities									(546)	(603)	(614)
Net change in cash and cash equivalents									(17)	127	(120)
Cash and cash equivalents at beginning of year				784				657	784	657	777
Cash and cash equivalents at end of year	767				784				767	784	657
Cincinnati Financial Corporation
Cash Flows From Operating Activities
Net Income									1,997	287	1,045
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									10	7	7
Gain (Loss) on Sale of Investments									(720)	114	(28)
Dividends from subsidiaries									625	500	465
Changes in:
Increase in equity of subsidiaries									(1,414)	(367)	(859)
Investment income receivable									(1)	2	0
Current federal income taxes									(1)	14	(5)
Current income tax receivable/payable									146	(35)	(150)
Other assets									4	(17)	(20)
Other liabilities									4	3	15
Intercompany receivable for operations									20	19	13
Net cash provided by operating activities									670	527	483
Cash Flows From Investing Activities
Sale of fixed maturities									3	1	0
Call or maturity of fixed maturities									21	19	14
Sale of equity securities									122	131	230
Purchase of fixed maturities									(39)	(17)	(2)
Purchase of equity securities									(237)	(177)	(293)
Investment in buildings and equipment									(13)	(12)	(3)
Cash paid for acquisition									63
Change in other invested assets, net									(67)	(11)	0
Net cash used in investing activities									(273)	(66)	(54)
Cash Flows From Financing Activities
Payment of cash dividends to shareholders									(355)	(336)	(400)
Shares acquired - share repurchase authorization									(67)	(125)	(92)
Proceeds from stock options exercised									11	9	13
Other									2	1	1
Net cash used in financing activities									(409)	(451)	(478)
Net change in cash and cash equivalents									(12)	10	(49)
Cash and cash equivalents at beginning of year				$ 209				$ 199	209	199	248
Cash and cash equivalents at end of year	$ 197				$ 209				$ 197	$ 209	$ 199