Summary of Investments - SOI Mortgage provision allowance rollforward (Details 4) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2017	Dec. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 2,882	$ 2,890
Provision increases	0	536
Provision decreases	(1,573)	(544)
Ending balance	1,309	2,882
Allowance ending balance by basis of impairment method:
Individually evaluated for impairment	536	536
Collectively evaluated for impairment	773	2,346
Mortgage Loans on Real Estate
Recorded investment balance in the mortgage loan portfolio, gross of allowance, by basis of impairment method:
Recorded investment balance in the mortgage loan portfolio, gross of allowance, by basis of impairment method:	3,846,240	3,561,708
Individually evaluated for impairment	1,465	1,465
Collectively evaluated for impairment	3,844,775	3,560,243
Mortgage Loans on Real Estate
Recorded investment balance in the mortgage loan portfolio, gross of allowance, by basis of impairment method:
Recorded investment balance in the mortgage loan portfolio, gross of allowance, by basis of impairment method:	$ 3,846,240	$ 3,561,708

Amount of increase (decrease) of allowance reserve for credit loss.

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(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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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
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-SubTopic 310
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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Amount before allowance and after 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. Excludes loans and leases covered under loss sharing agreements.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Amount of expense related to estimated loss from loan and lease transactions.

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-SubTopic 225
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