Investments (Allowance for Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning of year	$ 4,154	$ 8,904	$ 6,028
Addition to (release of) allowance for losses	(1,503)	(1,832)	2,876
Charge-offs, net of recoveries	0	(2,918)	0
Allowance for credit losses, total ending balance	2,651	4,154	8,904
Agricultural Property Loans
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for credit losses, beginning of year	100	300
Allowance for credit losses, total ending balance	$ 100	$ 100	$ 300