Investments (Allowance for Credit Losses and Recorded Investment in Commercial Mortgage and Other Loans) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Allowance for Credit Losses:
Individually evaluated for impairment	$ 0	$ 0
Collectively evaluated for impairment (less than for Agricultural loans)	395	482
Total ending balance	395	482
Recorded Investment:
Gross of reserves: individually evaluated for impairment	0	0
Gross of reserves: collectively evaluated for impairment	407,313	423,045
Total ending balance, gross of reserves	407,313	423,045
Agricultural Property Loans
Allowance for Credit Losses:
Collectively evaluated for impairment (less than for Agricultural loans)	100	100
Recorded Investment:
Gross of reserves: collectively evaluated for impairment	52,000	54,000
Uncollateralized loans
Recorded Investment:
Gross of reserves: collectively evaluated for impairment	$ 3,000	$ 3,000