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Derivatives - Derivatives Associated with Fixed Income Trading Activities (Details) - USD ($) $ in Thousands | Sep. 30, 2020 | Dec. 31, 2019
--- | --- | ---
Customer interest rate contracts |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | $ 3,847,085 | $ 2,697,522
Assets | 240,218 | 65,768
Liabilities | 2,444 | 6,858
Offsetting upstream interest rate contracts |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | 3,847,085 | 2,697,522
Assets | 2,317 | 2,583
Liabilities | 16,828 | 3,994
Option contracts purchased | Long |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional |  | 40,000
Assets |  | 131
Liabilities |  | 0
Forwards and futures purchased |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | 15,069,709 | 9,217,350
Assets | 41,553 | 17,029
Liabilities | 3,456 | 3,187
Forwards and futures sold |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | 15,596,324 | 9,403,112
Assets | 5,788 | 3,611
Liabilities | $ 39,018 | $ 16,620

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