Investments (Analysis of Past Due Commercial Mortgage and Other Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Servicing Liabilities at Fair Value [Line Items]
Current	$ 1,643,745	$ 1,660,599
Total Commercial Mortgage and Other Loans	1,644,032	1,660,886
Non-Accrual Status	287	0
30-59 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	287
60-89 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Greater than 90 Days
Servicing Liabilities at Fair Value [Line Items]
Past Due	287	0
Commercial mortgage loans
Servicing Liabilities at Fair Value [Line Items]
Current	1,532,136	1,545,853
Total Commercial Mortgage and Other Loans	1,532,136	1,545,853
Non-Accrual Status	0	0
Commercial mortgage loans \| 30-59 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Commercial mortgage loans \| 60-89 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Commercial mortgage loans \| Greater than 90 Days
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Agricultural property loans
Servicing Liabilities at Fair Value [Line Items]
Current	103,199	106,336
Total Commercial Mortgage and Other Loans	103,486	106,623
Non-Accrual Status	287	0
Agricultural property loans \| 30-59 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	287
Agricultural property loans \| 60-89 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Agricultural property loans \| Greater than 90 Days
Servicing Liabilities at Fair Value [Line Items]
Past Due	287	0
Uncollateralized loans
Servicing Liabilities at Fair Value [Line Items]
Current	8,410	8,410
Total Commercial Mortgage and Other Loans	8,410	8,410
Non-Accrual Status	0	0
Uncollateralized loans \| 30-59 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Uncollateralized loans \| 60-89 Days Past Due
Servicing Liabilities at Fair Value [Line Items]
Past Due	0	0
Uncollateralized loans \| Greater than 90 Days
Servicing Liabilities at Fair Value [Line Items]
Past Due	$ 0	$ 0

Financing receivables that are current.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7A
-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953401-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=49124121&loc=d3e5111-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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