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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, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | $ (330) | $ 87 |  | $ (126) |
Foreign currency forward contracts [Member] |  |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | 3 | 9 |  | (31) |
Interest Rate Swap [Member] |  |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | (115) | 0 |  | 0 |
All Other Futures Contracts And Options [Member] |  |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | 39 | (21) |  | (10) |
Convertible Securities [Member] |  |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | [1] | (2) | 1 |  | 8 |
Investment And Embedded Derivative Instruments [Member] |  |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | (75) | (11) |  | (33) |
GLB |  |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | [2] | (248) | 364 |  | 53 |
Futures contracts on equities |  |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | (4) | (261) | [3] | (136) | [3]
Other Derivatives |  |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | (3) | (5) |  | (10) |
Guaranteed Living Benefit And Other Derivative Instruments [Member] |  |  |  |  |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  | $ (255) | $ 98 |  | $ (93) |
[1] | Includes embedded derivatives.
[2] | Excludes foreign exchange gains (losses) related to GLB.
[3] | Related to GMDB and GLB blocks 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=109980867&loc=SL5618551-113959 + Details
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