Investments (Mortgage Loans by Portfolio Segment) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Company-held mortgage loans held-for-investment, net
Commercial mortgage loans	$ 44,375	$ 41,512
Percentage of loans receivable on commercial mortgage loans	64.60%	63.70%
Agricultural mortgage loans	$ 13,014	$ 12,564
Percentage of loans receivable on agricultural mortgage loans	18.90%	19.30%
Residential mortgage loans	$ 11,136	$ 10,829
Percentage of loans receivable on residential mortgage loans	16.20%	16.60%
Subtotal	$ 68,525	$ 64,905
Percentage of loans receivable on subtotal	99.70%	99.60%
Valuation allowances	$ (314)	$ (304)	$ (281)	$ (279)
Percentage of loans receivable on valuation allowances	0.50%	0.50%
Subtotal mortgage loans, net	$ 68,211	$ 64,601
Percentage of loans receivable on subtotal mortgage loans held-for-investment, net	99.20%	99.10%
Percentage of residential mortgage loans - FVO	0.80%	0.90%
Total mortgage loans, net	$ 68,731	$ 65,167
Percentage of loans held for sale on total mortgage loans, net	100.00%	100.00%
Residential — FVO
Company-held mortgage loans held-for-investment, net
Total mortgage loans, net	$ 520	$ 566

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

+ References

No definition available.

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- Definition

Percentage of loans and leases receivable consumer other 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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- Definition

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

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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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(a)(3),(b))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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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
-Paragraph 1
-Subparagraph (SX 210.9-03.7(a)(1))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5066-111524

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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://www.xbrl.org/2003/role/presentationRef
-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

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

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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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-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

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