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Derivative Instruments - Summary of Location and Amount of Gains and Losses of Derivative Contracts (Detail) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Unrealized gains (losses) |  |  | $ 598 | $ (760)
Derivative, Gain (Loss) on Derivative, Net | $ (35,412) | $ 8,932 | (51,571) | 34,123
Derivative, Gain (Loss) on Derivatives, Total Net | (68,069) | 186,304 | (161,143) | 252,687
Net gains (losses) on derivative contracts [Domain] | Credit Derivatives [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | 310 | (217) |  |
Net gains (losses) on derivative contracts [Domain] | Interest Rate Swap [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | (7,377) | 1,620 |  |
Net gains (losses) on derivative contracts [Domain] | Futures Contracts [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | (28,345) | 7,529 |  |
Derivative Products [Member] | Interest Rate Swap [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  |  | (10,109) | 6,163
Derivative Products [Member] | Other Contracts [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  |  | (42,245) | 28,523
Net Change In Fair Value Of Credit Derivatives [Member] | Credit Derivatives [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net |  |  | 783 | (563)
Income Loss On Variable Interest Entities [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | (32,657) | 177,372 | (109,572) | 218,564
Income Loss On Variable Interest Entities [Member] | Interest Rate Swap [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | (36,370) | 163,229 | (106,211) | 213,038
Income Loss On Variable Interest Entities [Member] | Currency Swaps [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |
Debt and Equity Securities, FV-NI [Line Items] |  |  |  |
Derivative, Gain (Loss) on Derivative, Net | $ 3,713 | $ 14,143 | $ (3,361) | $ 5,526

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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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