Investments (Allowance for Credit Losses and Recorded Investment in Commercial Mortgage and Other Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for Credit Losses:
Individually evaluated for impairment	$ 0	$ 0
Collectively evaluated for impairment	165	151
Total ending balance	165	151	$ 180	$ 209
Recorded Investment:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	143,263	118,787
Total ending balance	143,263	118,787
Financial Asset Acquired with Credit Deterioration
Recorded Investment:
Financing Receivable Total	0	0
Commercial Mortgage Loans
Allowance for Credit Losses:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	164	150
Total ending balance	164	150	179	207
Recorded Investment:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	139,803	113,819
Total ending balance	139,803	113,819
Agricultural Property Loans
Allowance for Credit Losses:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	1	1
Total ending balance	1	1	$ 1	$ 2
Recorded Investment:
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	3,460	4,968
Total ending balance	$ 3,460	$ 4,968