Investments (Commercial Mortgage and Other Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 1,139,029	$ 1,085,213
% of Total	100.00%	100.00%
Valuation allowance	$ (1,663)	$ (1,794)
Total commercial mortgage and other loans	1,137,366	1,083,419
Apartments and multi-family
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 358,405	$ 356,694
% of Total	31.50%	32.90%
Hospitality
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 16,419	$ 16,529
% of Total	1.40%	1.50%
Industrial
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 230,050	$ 180,619
% of Total	20.20%	16.70%
Office
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 169,762	$ 159,646
% of Total	14.90%	14.70%
Other
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 93,195	$ 99,119
% of Total	8.20%	9.10%
Retail
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 204,271
% of Total	17.90%	18.90%
Commercial mortgage loans
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 1,072,102	$ 1,017,974
% of Total	94.10%	93.80%
Agricultural property loans
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 66,927	$ 67,239
% of Total	5.90%	6.20%

Commercial mortgage loans, Percentage

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- Definition

The reserve to cover probable credit losses related to specifically identified fixed maturity real estate loans as well as probable credit losses inherent in the remainder of that loan portfolio.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=82921503&loc=d3e21338-158488

+ Details

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- Definition

Amount before allowance of mortgage loans on existing land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5066-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(a)(3))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes loans held for sale. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(a))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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