Investments (Net Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Net Investment Income [Line Items]
Less: Investment expenses	$ 302	$ 261
Subtotal	3,745	4,421
Securities Investment
Net Investment Income [Line Items]
Subtotal	4,400	4,266
Subtotal	4,098	4,005
Fixed maturity securities
Net Investment Income [Line Items]
Subtotal	2,896	2,825
Equity Securities
Net Investment Income [Line Items]
Subtotal	16	31
Actively traded securities and FVO general account securities
Net Investment Income [Line Items]
Subtotal	6	29
Mortgage loans
Net Investment Income [Line Items]
Subtotal	792	736
Policy loans
Net Investment Income [Line Items]
Subtotal	124	127
Real estate and real estate joint ventures
Net Investment Income [Line Items]
Subtotal	168	153
Other limited partnership interests
Net Investment Income [Line Items]
Subtotal	207	240
Cash, cash equivalents and short-term investments
Net Investment Income [Line Items]
Subtotal	72	51
Operating joint ventures
Net Investment Income [Line Items]
Subtotal	13	2
Other
Net Investment Income [Line Items]
Subtotal	106	72
FVO contractholder-directed unit-linked investments
Net Investment Income [Line Items]
Subtotal	$ (353)	$ 416

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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No definition available.

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