Derivatives (Fair Value Hedges) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Net Derivative Gains (Losses) Recognized for Derivatives	$ 74	$ 287	$ 65	$ 788
Net Derivative Gains (Losses) Recognized for Hedged Items	13	(286)	28	(778)
Ineffectiveness Recognized in Net Derivative Gains (Losses)	87	1	93	10
Interest rate swaps \| Fixed Maturity Securities
Derivative Instruments, Gain (Loss) [Line Items]
Net Derivative Gains (Losses) Recognized for Derivatives	0	(3)	1	(11)
Net Derivative Gains (Losses) Recognized for Hedged Items	(1)	0	(2)	7
Ineffectiveness Recognized in Net Derivative Gains (Losses)	(1)	(3)	(1)	(4)
Interest rate swaps \| Policyholder account balances [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net Derivative Gains (Losses) Recognized for Derivatives	52	197	(1)	543
Net Derivative Gains (Losses) Recognized for Hedged Items	18	(200)	70	(548)
Ineffectiveness Recognized in Net Derivative Gains (Losses)	70	(3)	69	(5)
Foreign currency swaps \| Foreign-denominated fixed maturity securities
Derivative Instruments, Gain (Loss) [Line Items]
Net Derivative Gains (Losses) Recognized for Derivatives	(2)	7	(5)	6
Net Derivative Gains (Losses) Recognized for Hedged Items	3	(8)	6	(6)
Ineffectiveness Recognized in Net Derivative Gains (Losses)	1	(1)	1	0
Foreign currency swaps \| Foreign-denominated policyholder account balances [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net Derivative Gains (Losses) Recognized for Derivatives	45	(51)	46	(26)
Net Derivative Gains (Losses) Recognized for Hedged Items	(26)	48	(24)	23
Ineffectiveness Recognized in Net Derivative Gains (Losses)	19	(3)	22	(3)
Foreign currency forwards \| Foreign-denominated fixed maturity securities
Derivative Instruments, Gain (Loss) [Line Items]
Net Derivative Gains (Losses) Recognized for Derivatives	(21)	137	24	276
Net Derivative Gains (Losses) Recognized for Hedged Items	19	(126)	(22)	(254)
Ineffectiveness Recognized in Net Derivative Gains (Losses)	$ (2)	$ 11	$ 2	$ 22

Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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