Derivatives (Fair Value Hedges) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Net Derivative Gains (Losses) Recognized for Derivatives	$ (12)	$ (23)	$ 52	$ 744
Net Derivative Gains (Losses) Recognized for Hedged Items	11	20	40	(736)
Ineffectiveness Recognized in Net Derivative Gains (Losses)	(1)	(3)	92	8
Interest rate swaps \| Fixed Maturity Securities
Derivative Instruments, Gain (Loss) [Line Items]
Net Derivative Gains (Losses) Recognized for Derivatives	1	5	2	(3)
Net Derivative Gains (Losses) Recognized for Hedged Items	0	(4)	(2)	1
Ineffectiveness Recognized in Net Derivative Gains (Losses)	1	1	0	(2)
Interest rate swaps \| Policyholder account balances
Derivative Instruments, Gain (Loss) [Line Items]
Net Derivative Gains (Losses) Recognized for Derivatives	(14)	(47)	(16)	472
Net Derivative Gains (Losses) Recognized for Hedged Items	13	42	84	(482)
Ineffectiveness Recognized in Net Derivative Gains (Losses)	(1)	(5)	68	(10)
Foreign currency swaps \| Foreign-denominated fixed maturity securities
Derivative Instruments, Gain (Loss) [Line Items]
Net Derivative Gains (Losses) Recognized for Derivatives	(10)	1	(15)	7
Net Derivative Gains (Losses) Recognized for Hedged Items	10	(1)	16	(7)
Ineffectiveness Recognized in Net Derivative Gains (Losses)	0	0	1	0
Foreign currency swaps \| Foreign-denominated policyholder account balances [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Net Derivative Gains (Losses) Recognized for Derivatives	15	(1)	61	(27)
Net Derivative Gains (Losses) Recognized for Hedged Items	(16)	1	(40)	24
Ineffectiveness Recognized in Net Derivative Gains (Losses)	(1)	0	21	(3)
Foreign currency forwards \| Foreign-denominated fixed maturity securities
Derivative Instruments, Gain (Loss) [Line Items]
Net Derivative Gains (Losses) Recognized for Derivatives	(4)	19	20	295
Net Derivative Gains (Losses) Recognized for Hedged Items	4	(18)	(18)	(272)
Ineffectiveness Recognized in Net Derivative Gains (Losses)	$ 0	$ 1	$ 2	$ 23

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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Amount of gain (loss)recognized in the income statement from the hedging ineffectiveness of a fair value hedge.

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