Investments (Net Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Net Investment Income [Line Items]
Less: Investment expenses	$ 324	$ 356
Net investment income	3,061	4,908
Securities Investment
Net Investment Income [Line Items]
Gross Investment Income, Operating	4,525	4,528
Net investment income	4,201	4,172
Fixed Maturity Securities
Net Investment Income [Line Items]
Gross Investment Income, Operating	2,875	2,939
Equity Securities
Net Investment Income [Line Items]
Gross Investment Income, Operating	14	17
FVO Securities
Net Investment Income [Line Items]
Gross Investment Income, Operating	(78)	55
Mortgage loans
Net Investment Income [Line Items]
Gross Investment Income, Operating	884	912
Policy loans
Net Investment Income [Line Items]
Gross Investment Income, Operating	126	128
Real Estate and Real Estate Joint Ventures
Net Investment Income [Line Items]
Gross Investment Income, Operating	165	130
Other limited partnership interests
Net Investment Income [Line Items]
Gross Investment Income, Operating	320	123
Cash, cash equivalents and short-term investments
Net Investment Income [Line Items]
Gross Investment Income, Operating	92	128
Operating joint ventures
Net Investment Income [Line Items]
Gross Investment Income, Operating	25	18
Other
Net Investment Income [Line Items]
Gross Investment Income, Operating	102	78
Unit-linked investments
Net Investment Income [Line Items]
Net investment income	(1,140)	736
Trading Securities, Change in Unrealized Holding Gain (Loss)	$ (1,100)	$ 648

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-SubTopic 220
-Section S99
-Paragraph 1
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Amount of expenses related to the generation of investment income.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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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.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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