Investments (Net Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net Investment Income [Line Items]
Less: Investment expenses	$ 362	$ 333	$ 1,079	$ 950
Net investment income	4,623	4,486	14,224	12,704
Fixed Maturity Securities
Net Investment Income [Line Items]
Gross Investment Income, Operating	2,924	3,056	8,887	8,966
Equity Securities
Net Investment Income [Line Items]
Gross Investment Income, Operating	13	15	45	46
FVO Securities
Net Investment Income [Line Items]
Gross Investment Income, Operating	59	11	152	25
Mortgage loans
Net Investment Income [Line Items]
Gross Investment Income, Operating	930	859	2,785	2,466
Policy loans
Net Investment Income [Line Items]
Gross Investment Income, Operating	129	130	386	381
Real Estate and Real Estate Joint Ventures
Net Investment Income [Line Items]
Gross Investment Income, Operating	181	175	490	538
Other limited partnership interests
Net Investment Income [Line Items]
Gross Investment Income, Operating	277	227	643	554
Cash, cash equivalents and short-term investments
Net Investment Income [Line Items]
Gross Investment Income, Operating	117	112	358	279
Operating joint ventures
Net Investment Income [Line Items]
Gross Investment Income, Operating	10	2	66	34
Other
Net Investment Income [Line Items]
Gross Investment Income, Operating	95	83	244	283
Securities Investment
Net Investment Income [Line Items]
Gross Investment Income, Operating	4,735	4,670	14,056	13,572
Net investment income	4,373	4,337	12,977	12,622
FVO contractholder-directed unit-linked investments
Net Investment Income [Line Items]
Net investment income	250	149	1,247	82
Changes in estimated fair value included in net investment income	$ 185	$ 109	$ 850	$ (59)

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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