Investments (Securities Lending Remaining Tenor - Narrative) (Details) $ in Billions	Dec. 31, 2017 USD ($)
U.S. government and agency
Securities Financing Transaction [Line Items]
Percentage Of US Treasury And Agency Securities At Estimated Fair Value Of Securities On Loan Relating To Cash Collateral On Open	100.00%
Securities Investment
Securities Financing Transaction [Line Items]
Percentage of Reinvestment Portfolio in Fixed Maturity Securities	59.00%
Estimated fair value
Securities Financing Transaction [Line Items]
Cash collateral on deposit from counterparties	$ 1.6

The percentage of US Treasury and agency securities at estimated fair value of securities on loan relating to cash collateral on open.

No definition available.

+ Details

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- Definition

The percentage of the reinvestment portfolio acquired with the cash collateral consists mainly of Fixed maturities.

+ References

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.

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- Definition

Amount of securities loaned to entities in exchange for collateral, not subject to a master netting arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226052-175313

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