Average debt service coverage ratio.

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- Definition

Current weighted average loan to value ratio of commercial mortgage loan.

+ References

No definition available.

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- Definition

Original weighted average loan to value ratio of commercial mortgage loan.

+ References

No definition available.

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- Definition

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

+ 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(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

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Percent of net assets at close of period. For schedules of investments that are categorized, each category has a percent of net assets for the aggregated value of the Investments in the category.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
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- Definition

Total carrying amount of mortgage loans as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
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- Definition

The carrying amount of the outstanding balance due under the mortgage loan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
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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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- Definition

Amount of principal due on loans that have been delinquent, which may exclude loans having interest delinquent for three months or less, as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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- Definition

Amount of reserve for write-down of a mortgage loan on real estate.

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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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- 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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Investment Holding Level 4 Mortgage Loans (Details)	9 Months Ended
Investment Holding Level 4 Mortgage Loans (Details)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 2,880,000,000		$ 2,811,000,000
Movement in Mortgage Loans on Real Estate [Roll Forward]
Current Weighted Average Loan to Value Ratio of Commercial Mortgage Loan	48.00%
Original Weighted Average Loan to Value Ratio of Commercial Mortgage loan	63.00%
Commercial Loan [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate	$ 2,900,000,000		2,800,000,000
Allowance for Loan and Lease Losses, Real Estate	(1,000,000)	$ (19,000,000)	(19,000,000)	$ (19,000,000)
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	2,880,000,000		$ 2,811,000,000
Movement in Mortgage Loans on Real Estate [Roll Forward]
Allowance for Loan and Lease Losses, Period Increase (Decrease)	1,000,000	0
Allowance for Loan and Lease Losses, Write-offs	$ 19,000,000	$ 0
Average Debt Service Coverage Ratio	2.52		2.55
Nonperforming Financial Instruments [Member] \| Commercial Loan [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate, Principal Amount of Delinquent Loans	$ 0		$ 1
Mortgages [Member] \| Commercial Loan [Member]
Movement in Mortgage Loans on Real Estate [Roll Forward]
Mortgage Loans on Real Estate, Principal Amount of Delinquent Loans			15,000,000
Mortgage Loans on Real Estate, Write-down or Reserve, Amount			16,000,000
LTV 80 to 100 Percent [Member] \| Commercial Loan [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 6,000,000		$ 20,000,000
Movement in Mortgage Loans on Real Estate [Roll Forward]
Average Debt Service Coverage Ratio	1.36		0.59
LTV Between 65 to 80 Percent [Member] \| Commercial Loan [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 41,000,000		$ 182,000,000
Movement in Mortgage Loans on Real Estate [Roll Forward]
Average Debt Service Coverage Ratio	2.31		2.17
LTV Less than 65 Percent [Member] \| Commercial Loan [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 2,833,000,000		$ 2,609,000,000
Movement in Mortgage Loans on Real Estate [Roll Forward]
Average Debt Service Coverage Ratio	2.53		2.61
Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	100.00%		100.00%
East North Central [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 53,000,000		$ 54,000,000
East North Central [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	1.80%		1.90%
East South Central [Member] [Domain]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 14,000,000		$ 14,000,000
East South Central [Member] [Domain] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	0.50%		0.50%
Middle Atlantic [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 292,000,000		$ 237,000,000
Middle Atlantic [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	10.10%		8.40%
New England [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 92,000,000		$ 93,000,000
New England [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	3.20%		3.30%
Pacific [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 841,000,000		$ 814,000,000
Pacific [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	29.30%		29.00%
South Atlantic [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 616,000,000		$ 613,000,000
South Atlantic [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	21.40%		21.80%
West South Central [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 196,000,000		$ 128,000,000
West South Central [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	6.80%		4.60%
Region Others [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 776,000,000		$ 858,000,000
Region Others [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	26.90%		30.50%
Industrial Property [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 728,000,000		$ 793,000,000
Industrial Property [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	25.30%		28.20%
Hotel [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 25,000,000		$ 25,000,000
Hotel [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	0.90%		0.90%
Multifamily [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 664,000,000		$ 535,000,000
Multifamily [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	23.00%		19.00%
Office Building [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 683,000,000		$ 605,000,000
Office Building [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	23.70%		21.50%
Retail Site [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 578,000,000		$ 611,000,000
Retail Site [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	20.10%		21.80%
Other Property [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 202,000,000		$ 242,000,000
Other Property [Member] \| Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Investment Owned, Percent of Net Assets	7.00%		8.60%
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 0		$ 0
Allowance for Loan and Lease Losses [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgage Loans on Real Estate, Carrying Amount of Mortgages	$ 18,000,000		$ 31,000,000