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Derivative Instruments - Summary of Location and Amount of Gains and Losses of Derivative Contracts (Detail) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
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Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |  |  |  |  |  |  |  |
Unrealized Gain (Loss) on Derivatives |  |  |  |  |  |  |  |  | $ 1 | $ (1) | $ 15
Derivative, Gain (Loss) on Derivative, Net | $ 12 | $ (10) | $ (35) | $ (16) | $ (45) | $ 18 | $ 9 | $ 25 | (50) | 7 | 76
Derivative, Gain (Loss) on Derivatives, Total Net |  |  |  |  |  |  |  |  | (82) | 512 | (76)
Net gains (losses) on derivative contracts [Domain] | Credit Derivatives [Member] |  |  |  |  |  |  |  |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |  |  |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  |  |  |  |  |  |  |  | 2 | (1) | 16
Net gains (losses) on derivative contracts [Domain] | Interest Rate Swaps [Member] |  |  |  |  |  |  |  |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |  |  |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  |  |  |  |  |  |  |  | (6) | 1 | 49
Net gains (losses) on derivative contracts [Domain] | Futures Contracts [Member] |  |  |  |  |  |  |  |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |  |  |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  |  |  |  |  |  |  |  | (45) | 7 | 11
Income Loss On Variable Interest Entities [Member] | Variable Interest Entity [Member] |  |  |  |  |  |  |  |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |  |  |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  |  |  |  |  |  |  |  | (32) | 505 | (152)
Income Loss On Variable Interest Entities [Member] | Interest Rate Swaps [Member] | Variable Interest Entity [Member] |  |  |  |  |  |  |  |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |  |  |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  |  |  |  |  |  |  |  | (20) | 493 | (127)
Income Loss On Variable Interest Entities [Member] | Currency Swaps [Member] | Variable Interest Entity [Member] |  |  |  |  |  |  |  |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |  |  |  |  |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  |  |  |  |  |  |  |  | $ (12) | $ 11 | $ (26)

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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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- Definition The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585 + Details
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