Long-Term Debt And Capital Lease Obligation (Book Value And Principal Amounts Of Long-Term Debt (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Book value	$ 790,000,000	$ 790,000,000
Principal amount	793,000,000	793,000,000
Senior Debentures 6.900 Percent Due 2028 [Member]
Debt Instrument [Line Items]
Interest rate	6.90%
Debt issuance year	1998
Book value	28,000,000	28,000,000
Principal amount	28,000,000	28,000,000
Senior Debentures 6.920 Percent Due 2028 [Member]
Debt Instrument [Line Items]
Interest rate	6.92%
Debt issuance year	2005
Book value	391,000,000	391,000,000
Principal amount	391,000,000	391,000,000
Senior Notes 6.125 Percent Due 2034 [Member]
Debt Instrument [Line Items]
Interest rate	6.125%
Debt issuance year	2004
Book value	371,000,000	371,000,000
Principal amount	374,000,000	374,000,000
Cincinnati Financial Corporation [Member]
Debt Instrument [Line Items]
Book value	$ 790,000,000	$ 790,000,000