Investments (Credit Quality Indicators For Mortgage Loans) (Details) $ in Millions	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	$ 9,430	$ 8,678
Percentage of total mortgage loans on real estate	100.00%	100.00%
Loan-to-value ratio, less than 65% [Member]
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	$ 8,239	$ 7,718
Percentage of total mortgage loans on real estate	87.40%	88.90%
Debt-service coverage ratio	2.14	2.06
Loan-to-value ratio, 65% to 74% [Member]
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	$ 954	$ 653
Percentage of total mortgage loans on real estate	10.10%	7.50%
Debt-service coverage ratio	1.84	1.60
Loan-to-value ratio, 75% to 100% [Member]
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	$ 227	$ 301
Percentage of total mortgage loans on real estate	2.40%	3.50%
Debt-service coverage ratio	0.93	0.83
Loan-To-Value Ratio, Greater Than 100% [Member]
Mortgage Loans Credit Quality [Line Items]
Principal amount of mortgage loans on real estate	$ 10	$ 6
Percentage of total mortgage loans on real estate	0.10%	0.10%
Debt-service coverage ratio	1.10	1.05

Ratio that compares a property's net operating income to its debt-service payments.

No definition available.

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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

Reflects the percentage derived from dividing mortgage loans with a specified loan-to-value ratio by total principal amount of mortgage loans.

+ References

No definition available.

+ Details

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- Definition

Amount of the contractual principal due at the origination of the mortgage loan (face amount).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

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