Investments - Realized Investment Gains and Losses and Change in Unrealized Investment Gains and Losses and Other Items (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Investment income:
Interest	$ 117	$ 114	$ 235	$ 226
Dividends	60	53	118	106
Other	1	2	3	5
Total	178	169	356	337
Less investment expenses	3	3	7	6
Total	175	166	349	331
Gain (Loss) on Sale of Investments			1,011	(669)
Investment gains and losses, net:
Investment gains and losses, net	520	1,060	1,024	(665)
Equity securities
Investment income:
Gain (Loss) on Sale of Investments	0	24	6	17
Unrealized Gain (Loss) on Investments	489	1,044	974	(602)
Investment gains and losses, net:
Other	22	(8)	32	(5)
Investment gains and losses, net	489	1,068	980	(585)
Fixed maturities
Investment gains and losses, net:
Gross realized gains	11	3	14	5
Writedown of Impaired Securities Intended to be Sold	0	0	0	(77)
Investment gains and losses, net	9	0	12	(75)
Available-for-sale Securities, Gross Realized Losses	$ (2)	$ (3)	$ (2)	$ (3)

Income derived from those other than interest and dividends.

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This item represents realized investment gains (losses) included in earnings for the period excluding those relating to other than temporary impairment losses on investments in debt securities. Includes realized investment gains and losses generated from the sale of debt securities, equity securities, investments in joint ventures and limited partnerships and from other than temporary impairments on investments other than debt securities. Also includes realized investment gains and losses are generated from prepayment premiums, recoveries of principal on previously impaired securities, provisions for losses on commercial mortgage and other loans, and fair value changes on embedded derivatives and derivatives that do not qualify for hedge accounting treatment, except those derivatives used in the Company's capacity as a broker or dealer.

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Writedown of impaired available-for-sale debt securities to fair value due to intent to sell

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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities.

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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 dividend income on nonoperating securities.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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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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Amount of realized gain (loss) on investment.

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Amount of unrealized gain (loss) on investment.

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