SOI Mortgage provision allowance rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Activity in the allowance for commercial mortgage loans credit losses
Beginning balance	$ 2,890	$ 2,890	$ 2,890
Provision increases	536	0	0
Provision decreases	(544)	0	0
Ending balance	2,882	2,890	2,890
Allowance ending balance by basis of impairment method:
Individually evaluated for impairment	536	0	0
Collectively evaluated for impairment	2,346	2,890	2,890
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:	3,561,708	3,250,594	3,366,460
Individually evaluated for impairment	1,465	14,031	12,986
Collectively evaluated for impairment	$ 3,560,243	$ 3,236,563	$ 3,353,474

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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- 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=6873192&loc=d3e21338-158488

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- Definition

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

+ References

No definition available.

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- References

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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- Definition

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

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- Definition

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

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
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-Paragraph 11B
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The balance of financing receivables that were individually evaluated for impairment.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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- Definition

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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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- References

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Amount of expense related to estimated loss from loan and lease transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

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-Name Accounting Standards Codification
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-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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