Investments (Net realized investment gains (losses)) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net realized investment gains (losses)	$ 16	$ 0	$ (20)	$ 10
Fixed maturity securities [Member]
Gross realized gains	40	36	85	69
Gross realized losses	(24)	(48)	(86)	(69)
Net realized investment gains (losses)	16	(12)	(1)	0
Total equity securities available-for-sale [Member]
Gross realized gains	4	0	4	1
Gross realized losses	(1)	(1)	(6)	(2)
Net realized investment gains (losses)	3	(1)	(2)	(1)
Derivative [Member]
Net realized investment gains (losses)	(6)	11	(13)	10
Short term investments and other [Member]
Net realized investment gains (losses)	$ 3	$ 2	$ (4)	$ 1

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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