Net Investment Income And Gains Losses On Trading Securities Before Investment Expenses.

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Amount of realized and unrealized gain (loss) on investment.

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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.

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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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Investments - Net Investment Income and Investment Gains (Losses) (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Investment Income [Line Items]
Total investment income		$ 2,430	$ 1,878	$ 2,241
Investment expenses		(75)	(61)	(59)
Investment gains (losses)		49	(57)	122
Net investment income	$ 116	2,355	1,817	2,182
Fixed Maturity Securities [Member]
Net Investment Income [Line Items]
Total investment income		1,817	1,795	1,812
Investment gains (losses)		(6)	4	122
Limited Partnership Investments [Member]
Net Investment Income [Line Items]
Total investment income		204	22	277
Short term investments and other [Member]
Net Investment Income [Line Items]
Total investment income		52	43	18
Investment gains (losses)			4	4
Equity Securities [Member]
Net Investment Income [Line Items]
Total investment income		85	18	12
Investment gains (losses)		66	(74)
Income (loss) From Trading Portfolio [Member]
Net Investment Income [Line Items]
Total investment income		216	(54)	87
Other [Member]
Net Investment Income [Line Items]
Total investment income		56	54	35
Derivative Instruments [Member]
Net Investment Income [Line Items]
Investment gains (losses)		$ (11)	$ 9	$ (4)