Investments - Net Investment Income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Investment Income [Line Items]
Net investment income	$ 2,916	$ 2,508	$ 2,333
Consolidated Entity Excluding Variable Interest Entities (VIE)
Net Investment Income [Line Items]
Investment revenue	3,219	2,781	2,604
Investment expenses	(303)	(273)	(271)
Net investment income	2,916	2,508	2,333
Consolidated Entity Excluding Variable Interest Entities (VIE) \| AFS securities \| Total fixed maturity securities
Net Investment Income [Line Items]
Investment revenue	2,293	2,051	1,868
Consolidated Entity Excluding Variable Interest Entities (VIE) \| AFS securities \| Equity securities
Net Investment Income [Line Items]
Investment revenue	9	7	6
Consolidated Entity Excluding Variable Interest Entities (VIE) \| Trading securities
Net Investment Income [Line Items]
Investment revenue	238	196	136
Consolidated Entity Excluding Variable Interest Entities (VIE) \| Mortgage loans, net of allowances
Net Investment Income [Line Items]
Investment revenue	355	320	347
Consolidated Entity Excluding Variable Interest Entities (VIE) \| Investment funds
Net Investment Income [Line Items]
Investment revenue	180	109	177
Consolidated Entity Excluding Variable Interest Entities (VIE) \| Funds withheld at interest
Net Investment Income [Line Items]
Investment revenue	82	54	46
Consolidated Entity Excluding Variable Interest Entities (VIE) \| Other
Net Investment Income [Line Items]
Investment revenue	$ 62	$ 44	$ 24

Amount, before investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

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Amount of expenses related to the generation of investment income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.2)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

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Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

+ 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(2))
-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 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-16(Column G))
-URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574960-122915

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+ References

No definition available.

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