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Derivatives - Derivatives Associated with Fixed Income Trading Activities (Details) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
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Customer interest rate contracts |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | $ 2,200,080 | $ 2,026,753
Assets | 7,861 | 22,097
Liabilities | 55,392 | 18,323
Offsetting upstream interest rate contracts |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | 2,200,080 | 2,026,753
Assets | 7,904 | 17,931
Liabilities | 8,244 | 20,720
Option contracts purchased | Long |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | 30,000 | 20,000
Assets | 32 | 15
Liabilities | 0 | 0
Forwards and futures purchased |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | 5,425,631 | 6,257,140
Assets | 4,915 | 4,354
Liabilities | 14,002 | 5,526
Forwards and futures sold |  |
Derivative Instruments, Gain (Loss) [Line Items] |  |
Notional | 5,701,595 | 6,292,012
Assets | 15,098 | 5,806
Liabilities | $ 4,768 | $ 4,010

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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Article 12 -Section 13 -Sentence Column B + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets. + References No definition available. + Details
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- Definition Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities. + References No definition available. + Details
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