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Investments (Net Realized Gains (Losses) And Losses Included In Net Realized Gains (Losses) And Other Comprehensive Income) (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Gain (Loss) on Securities [Line Items] |  |  |  |
Other-than-temporary impairment (OTTI) losses gross |  | $ (90) | $ (52) |
OTTI on Fixed Maturities |  | (58) | (49) |
Debt Securities, Available-for-sale, Allowance for Credit Loss, Period Increase (Decrease) | $ 188 |  |  |
Debt Securities, Available-For-Sale, Credit Impairment Charges Intent to Sell | (170) | 0 | 0 |
Foreign exchange gains( losses) | (483) | 7 | 131 |
Fair Value adjustment on insurance derivative | (202) | (4) | (248) |
Derivative, Gain (Loss) on Derivative, Net | (228) | (585) | (330) |
Realized Investment Gains (Losses) | (498) | (530) | (652) |
Unrealized Gain (Loss) on Investments | 2,130 | 3,088 | (1,699) |
Other Comprehensive Income (Loss), Securities, Available-for-sale, Tax | (462) | (647) | 297 |
Other derivative instruments |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | 1 | (8) | (3) |
Investment and embedded derivative instruments |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | 81 | (435) | (75) |
S&P Options and Futures |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | (108) | (138) | (4) |
Equity Securities [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) | 586 | 104 | (59) | [1]
Fixed maturities held to maturity |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Unrealized Gain (Loss) on Investments | (24) | (31) | (38) |
Other Investments [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Realized Investment Gains (Losses) | (32) | (20) | (5) |
Available-for-sale Securities [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Unrealized Gain (Loss) on Investments | 2,628 | 3,769 | (1,958) |
Debt Securities [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Other-than-temporary impairment (OTTI) losses gross |  | (90) | (52) |
OTTI on fixed maturities recognized in OCI (pre-tax) | 0 | 32 | 3 |
OTTI on Fixed Maturities |  | (58) | (49) |
Fixed Maturities [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment | 244 | 203 | 334 |
Debt Securities, Available-for-sale, Realized Loss, Excluding Other-than-temporary Impairment | (366) | (176) | (587) |
Debt Securities, Available-for-sale, Realized Gain (Loss) | (281) | (31) | (302) |
Other [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Gain (Loss) on Sale of Other Investments | (60) | (5) | (87) |
Unrealized Gain (Loss) on Investments | (12) | (3) | 0 |
Accounting Standards Update 2016-01 [Member] | Equity Securities [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Equity Securities, FV-NI, Realized Gain (Loss) | 586 | 104 | (59) |
Unrealized Gain (Loss) on Investments | 131 | 46 | (129) |
Gain (Loss) on Sale of Investments | 455 | 58 | 70 |
Accounting Standards Update 2016-01 [Member] | Other Investments [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Realized Investment Gains (Losses) | (32) | (20) | (5) |
Unrealized Gain (Loss) on Investments | (32) | (15) | (126) |
Gain (Loss) on Sale of Investments | 0 | (5) | 121 |
Accounting Standards Update 2016-01 [Member] | Equity securities and other investments [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Realized Investment Gains (Losses) | 554 | 84 | (64) |
Unrealized Gain (Loss) on Investments | 99 | 31 | (255) |
Gain (Loss) on Sale of Investments | 455 | 53 | 191 |
Accounting Standards Update 2016-13 [Member] |  |  |  |
Gain (Loss) on Securities [Line Items] |  |  |  |
Debt Securities, Available-for-sale, Allowance for Credit Loss, Period Increase (Decrease) | $ 11 | $ 0 | $ 0 |
[1] | Relates to certain securities we intended to sell and securities written to market entering default.

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