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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 | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | $ (228) | $ (585) | $ (330)
Foreign currency forward contracts [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | 65 | (79) | 3
Interest Rate Swap [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | 0 | (270) | (115)
All Other Futures Contracts And Options [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | 16 | (88) | 39
Convertible Securities [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | [1] | 0 | 2 | (2)
Investment And Embedded Derivative Instruments [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | 81 | (435) | (75)
GLB |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | (202) | (4) | (248)
Futures contracts on equities |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | [2] | (108) | (138) | (4)
Other Derivatives |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | 1 | (8) | (3)
Guaranteed Living Benefit And Other Derivative Instruments [Member] |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | $ (309) | $ (150) | $ (255)
[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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