Investments (Allowance for Credit Losses and Recorded Investment in Commercial Mortgage and Other Loans) (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Allowance for Credit Losses:
Individually evaluated for impairment	$ 0	$ 940,000
Collectively evaluated for impairment	2,651,000	3,214,000
Total ending balance	2,651,000	4,154,000
Recorded Investment:
Gross of reserves: individually evaluated for impairment	287,000	15,875,000
Gross of reserves: collectively evaluated for impairment	1,660,599,000	1,669,832,000
Total ending balance, gross of reserves	1,660,886,000	1,685,707,000
Impaired Financing Receivable, Recorded Investment	0	15,900,000
Class Of Financing Receivable | Agricultural Loan
Recorded Investment:
Gross of reserves: individually evaluated for impairment	300,000	0
Impaired Financing Receivable, Recorded Investment	107,000,000	115,000,000
Class Of Financing Receivable | Uncollateralized loans
Recorded Investment:
Gross of reserves: individually evaluated for impairment	0	0
Agricultural Property Loans
Allowance for Credit Losses:
Collectively evaluated for impairment	100,000	100,000
Uncollateralized loans
Recorded Investment:
Gross of reserves: collectively evaluated for impairment	$ 8,000,000	$ 8,000,000