Investments (Mortgage Loans - Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Mortgage Loans on Real Estate [Line Items]
Financing Receivable, Significant Purchases	$ 923	$ 292
Percentage of Mortgage Loans Classified as Performing	99.00%		99.00%
Commercial
Mortgage Loans on Real Estate [Line Items]
Impaired Financing Receivable, Average Recorded Investment	$ 12	128
Agricultural
Mortgage Loans on Real Estate [Line Items]
Impaired Financing Receivable, Average Recorded Investment	28	60
Estimated fair value of mortgage loans held-for-investment	14,900		$ 14,700
Residential
Mortgage Loans on Real Estate [Line Items]
Impaired Financing Receivable, Average Recorded Investment	254	$ 147
Estimated fair value of mortgage loans held-for-investment	$ 12,600		$ 12,100

The percentage of all mortgage loans that are classified as performing.

No definition available.

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- Definition

The amount of any significant purchases of financing receivables during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5212-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5258-111524

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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

Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Details

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- Details

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