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Derivative Instruments and Hedging Activities - Value of Derivative Assets and Derivative Liabilities (Details) - Not Designated as Hedging Instruments - USD ($) $ in Thousands | Jun. 30, 2018 | Dec. 31, 2017
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Other Assets |  |
Derivatives not Designated as Hedging Instruments |  |
Fair value, Derivatives (included in Other Assets) | $ 6,157 | $ 3,074
Other Assets | Interest rate swap contracts—commercial loans |  |
Derivatives not Designated as Hedging Instruments |  |
Fair value, Derivatives (included in Other Assets) | 6,157 | 3,074
Notional amount, Derivatives (included in Other Assets) | 246,494 | 263,841
Net collateral received/posted, Derivatives | 2,560 | 0
Other Assets | Interest rate lock commitments—mortgage loans |  |
Derivatives not Designated as Hedging Instruments |  |
Fair value, Derivatives (included in Other Assets) | 398 | 226
Notional amount, Derivatives (included in Other Assets) | 12,711 | 6,860
Other Assets | Forward sale contracts—mortgage loans |  |
Derivatives not Designated as Hedging Instruments |  |
Fair value, Derivatives (included in Other Assets) | 0 | 0
Notional amount, Derivatives (included in Other Assets) | 0 | 0
Other Liabilities |  |
Derivatives not Designated as Hedging Instruments |  |
Fair value, Derivatives (included in Other Liabilities) | 6,223 | 3,055
Other Liabilities | Interest rate swap contracts—commercial loans |  |
Derivatives not Designated as Hedging Instruments |  |
Fair value, Derivatives (included in Other Liabilities) | 6,223 | 3,055
Notional amount, Derivatives (included in Other Liabilities) | 246,494 | 263,841
Net collateral received/posted, Derivatives | 0 | 1,448
Other Liabilities | Interest rate lock commitments—mortgage loans |  |
Derivatives not Designated as Hedging Instruments |  |
Fair value, Derivatives (included in Other Liabilities) | 0 | 0
Notional amount, Derivatives (included in Other Liabilities) | 0 | 0
Other Liabilities | Forward sale contracts—mortgage loans |  |
Derivatives not Designated as Hedging Instruments |  |
Fair value, Derivatives (included in Other Liabilities) | 39 | 5
Notional amount, Derivatives (included in Other Liabilities) | $ 12,250 | $ 6,580

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