Investments (Commercial Mortgage and Other Loans) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 1,355,375	$ 1,389,662
Commercial mortgage loans, Percentage	100.00%	100.00%
Valuation allowance	$ (2,972)	$ (2,650)
Total commercial mortgage and other loans	1,352,403	1,387,012
Apartments and multi-family
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 306,807	$ 348,718
Commercial mortgage loans, Percentage	22.60%	25.00%
Hospitality
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 3,671	$ 3,782
Commercial mortgage loans, Percentage	0.30%	0.30%
Industrial
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 358,883	$ 327,987
Commercial mortgage loans, Percentage	26.50%	23.60%
Office
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 299,216	$ 294,072
Commercial mortgage loans, Percentage	22.10%	21.20%
Other
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 135,790	$ 139,362
Commercial mortgage loans, Percentage	10.00%	10.00%
Retail
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 195,520	$ 216,544
Commercial mortgage loans, Percentage	14.40%	15.60%
Commercial Mortgage Loans
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 1,299,887	$ 1,330,465
Commercial mortgage loans, Percentage	95.90%	95.70%
Agricultural property loans
Commercial Mortgage and Other Loans [Line Items]
Commercial mortgage and agricultural property loans	$ 55,488	$ 59,197
Commercial mortgage loans, Percentage	4.10%	4.30%

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://fasb.org/us-gaap/role/ref/legacyRef
-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://fasb.org/us-gaap/role/ref/legacyRef
-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://fasb.org/us-gaap/role/ref/legacyRef
-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://fasb.org/us-gaap/role/ref/legacyRef
-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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