Investments (Mortgage Loans by Portfolio Segment) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Company-held mortgage loans held-for-investment, net
Commercial Mortgage Loans	$ 7,011	$ 6,497
Percentage of loans receivable on commercial mortgage loans	67.80%	69.90%
Agricultural Mortgage Loans	$ 2,144	$ 1,830
Percentage of loans receivable on agricultural mortgage loans	20.80%	19.70%
Residential Mortgage Loans	$ 1,098	$ 867
Percentage of loans receivable on residential mortgage loans	10.60%	9.30%
Subtotal (1)	$ 10,253	$ 9,194
Percentage of loans receivable on subtotal	99.20%	98.90%
Valuation allowances	$ (44)	$ (40)	$ (42)	$ (36)
Percentage of loans receivable on valuation allowances	(0.40%)	(0.40%)
Subtotal mortgage loans, net	$ 10,209	$ 9,154
Percentage of loans receivable on subtotal mortgage loans held-for-investment, net	98.80%	98.50%
Total mortgage loans, net	$ 10,328	$ 9,290
Percentage of loans receivable on commercial mortgage loans held by consolidated securitization entities - fair value option	1.20%	1.50%
Percentage of loans held for sale on total mortgage loans, net	100.00%	100.00%
Consolidated Securitization Entities
Company-held mortgage loans held-for-investment, net
Total mortgage loans, net	$ 119	$ 136

The balance represents the amount of loans that are secured by real estate mortgages.

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- Definition

Percentage of Allowance For Loan And Lease Losses on Real Estate to total Mortgage Loans on Real Estate.

+ References

No definition available.

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- Definition

Percentage of Commercial Mortgage Loans Held By Consolidated Securitization Entities Fair Value Option to total Mortgage Loans on Real Estate.

+ References

No definition available.

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- Definition

Percentage of Consumer Mortgage Loans and Leases Receivable to total Mortgage Loans on Real Estate.

+ References

No definition available.

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- Definition

Percentage of Commercial Agricultural Loans Receivable to total Mortgage Loans on Real Estate.

+ References

No definition available.

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- Definition

Percentage of Commercial Mortgage Loans Receivable to total Mortgage Loans on Real Estate.

+ References

No definition available.

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- Definition

Percentage of Mortgage Loans Held-for-investment, net to total Mortgage Loans on Real Estate.

+ References

No definition available.

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- Definition

Percentage of Mortgage Loans Held For Investment to total Mortgage Loans on Real Estate.

+ References

No definition available.

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- Definition

Percentage of Mortgage Loans On Real Estate to total Mortgage Loans on Real Estate.

+ References

No definition available.

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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

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Amount before allowance of consumer mortgage. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes subordinated loans such as home equity lines of credit and loans and leases covered under loss sharing agreements.

+ References

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-Publisher FASB
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-Topic 310
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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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. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

+ 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=82891408&loc=d3e4428-111522

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- Definition

Amount before allowance of loans issued to agricultural institutions. 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 942
-SubTopic 210
-Section S99
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-Subparagraph (SX 210.9-03.7(a)(1))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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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

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

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-Name Accounting Standards Codification
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