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Derivative Financial Instruments and Hedging Activities - Offsetting of Assets (Details) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Interest rate swap | Other assets |  |
Offsetting Assets [Line Items] |  |
Accrued interest on derivative asset interest rate swaps | $ 1 | $ 1
Counterparty A |  |
Offsetting Assets [Line Items] |  |
Gross Amounts of Recognized Assets | 436 | 74
Gross Amounts Offset in the Statements of Condition | 0 | 0
Net Amounts of Assets Presented in the Statements of Condition | 436 | 74
Gross Amounts Not Offset in the Statements of Condition, Financial Instruments | (163) | (74)
Gross Amounts Not Offset in the Statements of Condition, Cash Collateral Received | 0 | 0
Net Amount | $ 273 | $ 0

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