Investments (Net realized investment gains (losses)) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net realized investment gains (losses)	$ 46	$ (49)	$ 26	$ (39)
Fixed maturity securities [Member]
Gross realized gains	67	22	152	91
Gross realized losses	(20)	(51)	(106)	(120)
Net realized investment gains (losses)	47	(29)	46	(29)
Total equity securities available-for-sale [Member]
Gross realized gains	1	1	5	2
Gross realized losses	(4)	(19)	(10)	(21)
Net realized investment gains (losses)	(3)	(18)	(5)	(19)
Derivative [Member]
Net realized investment gains (losses)	1	(1)	(12)	9
Short term investments and other [Member]
Net realized investment gains (losses)	$ 1	$ (1)	$ (3)	$ 0

This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563

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