Investments (Mortgage Loans - Narrative) (Details) (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Significant Purchases	$ 1,400,000,000	$ 597,000,000
Percentage of Mortgage Loans Classified as Performing	99.00%		99.00%
Commercial
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, Average Recorded Investment	171,000,000	507,000,000
Agricultural
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, Average Recorded Investment	63,000,000	100,000,000
Estimated fair value of mortgage loans held-for-investment	12,800,000,000		12,800,000,000
Residential
Financing Receivable, Recorded Investment [Line Items]
Impaired Financing Receivable, Average Recorded Investment	47,000,000	13,000,000
Estimated fair value of mortgage loans held-for-investment	$ 7,700,000,000		6,600,000,000

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=35738203&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=35738203&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=35738203&loc=d3e5258-111524

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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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 3

-Article 5

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