Investments (Impaired Loans) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Recorded Investment	$ 13.7	$ 6.4
Unpaid Principal Balance Principal Balance	13.7	6.4
Related Allowance	4.2	0.4
Interest Income Recognized	0	0.5
Class Of Financing Receivable1 [Member] | Agricultural Loan [Member]
Recorded Investment	$ 74.0	$ 117.0