Investments (Credit Quality Indicators For Commercial Mortgage Loans) (Details) - Commercial [Member] $ in Millions	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Mortgage Loans Credit Quality [Line Items]
Carrying value of total mortgage loans on real estate	$ 13,510	$ 12,942
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]
Carrying value of total mortgage loans on real estate	$ 12,307	$ 11,656
Percentage of total mortgage loans on real estate	91.10%	90.10%
Debt-service coverage ratio	2.27	2.30
Loan-to-value ratio, 65% to 74% [Member]
Mortgage Loans Credit Quality [Line Items]
Carrying value of total mortgage loans on real estate	$ 1,165	$ 1,234
Percentage of total mortgage loans on real estate	8.60%	9.50%
Debt-service coverage ratio	1.75	1.76
Loan-to-value ratio, 75% to 100% [Member]
Mortgage Loans Credit Quality [Line Items]
Carrying value of total mortgage loans on real estate	$ 38	$ 52
Percentage of total mortgage loans on real estate	0.30%	0.40%
Debt-service coverage ratio	1.20	1.03

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

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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.

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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.

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- Definition

Amount of investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate.

+ References

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

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