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Commitments, Contingencies, And Guarantees (Net Realized Gains (Losses) Of Derivative Instrument Activity In Consolidated Statement Of Operations) (Detail) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2021 | Mar. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative |  | $ 383 | $ (547)
Foreign currency forward contracts |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative |  | (16) | 43
All Other Futures Contracts, Options and equities [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative |  | 125 | (27)
Convertible securities |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative | [1] | 0 | (1)
Total investment and embedded derivative instruments |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative |  | 109 | 15
GLB |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative |  | 319 | (685)
Futures contracts on equities |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative | [2] | (44) | 125
Other |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative |  | (1) | (2)
Guaranteed Living Benefit And Other Derivative Instruments [Member] |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |
Gain (Loss) on Derivative |  | $ 274 | $ (562)
[1] | Includes embedded derivatives.
[2] | Related to GMDB and GLB book of business.

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959 + Details
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