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Balance Sheet Offsetting - Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset (Details) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Net Amount Recognized, Derivatives, Financial Assets | $ 3,810 | $ 3,798
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets | (3,308) | (3,565)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets | (387) | (64)
Net Amount, Derivatives, Financial Assets | 115 | 169
Net Amount Recognized, Resell Agreements, Financial Assets | 9,642 | 9,642
Gross Amounts Not Offset, Financial Instruments, Resell Agreements, Financial Assets | 0 | 0
Gross Amounts Not Offset, Collateral, Resell Agreements, Financial Assets | (9,642) | (9,642)
Net Amount, Resell Agreements, Financial Assets | 0 | 0
Net Amount Recognized, Total Financial Assets | 13,452 | 13,440
Gross Amounts Not Offset, Collateral, Financial Assets | (10,029) | (9,706)
Net Amount, Financial Assets | 115 | 169
Net Amount Recognized, Derivatives, Financial Liabilities | 27,375 | 32,534
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities | (3,308) | (3,565)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities | (22,768) | (27,347)
Net Amount, Derivatives, Financial Liabilities | 1,299 | 1,622
Net Amount Recognized, Repurchase Agreements, Financial Liabilities | 1,117,199 | 963,317
Gross Amounts Not Offset, Financial Instruments, Repurchase Agreements, Financial Liabilities | 0 | 0
Gross Amounts Not Offset, Collateral, Repurchase Agreements, Financial Liabilities | (1,117,199) | (963,317)
Net Amount, Repurchase Agreements, Financial Liabilities | 0 | 0
Net Amount Recognized, Financial Liabilities | 1,144,574 | 995,851
Gross Amounts Not Offset, Collateral, Financial Liabilities | (1,139,967) | (990,664)
Net Amount, Financial Liabilities | 1,299 | 1,622
Counterparty A [Member] |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Net Amount Recognized, Derivatives, Financial Assets | 395 | 687
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets | (395) | (687)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets | 0 | 0
Net Amount, Derivatives, Financial Assets | 0 | 0
Net Amount Recognized, Derivatives, Financial Liabilities | 7,397 | 11,233
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities | (395) | (687)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities | (7,002) | (10,026)
Net Amount, Derivatives, Financial Liabilities | 0 | 520
Counterparty B [Member] |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Net Amount Recognized, Derivatives, Financial Assets | 1,028 | 223
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets | (1,028) | (223)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets | 0 | 0
Net Amount, Derivatives, Financial Assets | 0 | 0
Net Amount Recognized, Derivatives, Financial Liabilities | 4,466 | 6,867
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities | (1,028) | (223)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities | (3,101) | (6,344)
Net Amount, Derivatives, Financial Liabilities | 337 | 300
Counterparty C [Member] |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Net Amount Recognized, Derivatives, Financial Assets | 55 | 158
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets | (55) | (158)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets | 0 | 0
Net Amount, Derivatives, Financial Assets | 0 | 0
Net Amount Recognized, Derivatives, Financial Liabilities | 1,520 | 4,578
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities | (55) | (158)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities | (1,450) | (4,415)
Net Amount, Derivatives, Financial Liabilities | 15 | 5
Counterparty D [Member] |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Net Amount Recognized, Derivatives, Financial Assets | 0 | 1,820
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets | 0 | (1,820)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets | 0 | 0
Net Amount, Derivatives, Financial Assets | 0 | 0
Net Amount Recognized, Derivatives, Financial Liabilities | 0 | 7,706
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities | 0 | (1,820)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities | 0 | (5,886)
Net Amount, Derivatives, Financial Liabilities | 0 | 0
Other Counterparties [Member] |  |
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] |  |
Net Amount Recognized, Derivatives, Financial Assets | 2,332 | 910
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets | (1,830) | (677)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets | (387) | (64)
Net Amount, Derivatives, Financial Assets | 115 | 169
Net Amount Recognized, Derivatives, Financial Liabilities | 13,992 | 2,150
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities | (1,830) | (677)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities | (11,215) | (676)
Net Amount, Derivatives, Financial Liabilities | $ 947 | $ 797

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