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Investments (Realized Investment Gains Losses Net) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	$ 432	$ 2,194	$ 4,025
Fixed Maturities
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	581	666	1,634
Equity securities
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	1,066	376	451
Commercial mortgage and other loans
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	70	55	37
Investment Real Estate
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	12	15	40
Joint ventures and limited partnerships
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	(23)	(94)	(122)
Derivatives
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	(1,275)	1,175	1,970
Other
Gain (Loss) on Investments [Line Items]
Realized investment gains (losses), net	$ 1	$ 1	$ 15

X

- Definition

The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.3(a))
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 325
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=75031664&loc=d3e22529-158502

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+ References

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