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Derivative Financial Instruments Derivative Financial Instruments (Schedule of Notional Amount and Fair Value of Open Foreign Currency Forward Contract) (Details) € in Thousands, £ in Thousands, CAD in Thousands, $ in Thousands | Dec. 31, 2017 USD ($) | Dec. 31, 2017 CAD | Dec. 31, 2017 EUR (€) | Dec. 31, 2017 GBP (£) | Dec. 31, 2016 USD ($) | Dec. 31, 2016 CAD | Dec. 31, 2016 EUR (€) | Dec. 31, 2016 GBP (£)
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Financial Institution Counterparties [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member] |  |  |  |  |  |  |  |
Derivative Counter Party [Line Items] |  |  |  |  |  |  |  |
Forward Contracts - Assets, Notional Amount |  |  | € 4,014 | £ 127 |  |  | € 0 | £ 0
Financial Institution Counterparties [Member] | Other Liabilities [Member] | Not Designated as Hedging Instrument [Member] |  |  |  |  |  |  |  |
Derivative Counter Party [Line Items] |  |  |  |  |  |  |  |
Forward Contracts Liability, Notional Amount |  | CAD 25,413 | 4,846 | 1,178 |  | CAD 2,214 | 870 | 419
Customer Counterparties [Member] | Other Assets [Member] | Not Designated as Hedging Instrument [Member] |  |  |  |  |  |  |  |
Derivative Counter Party [Line Items] |  |  |  |  |  |  |  |
Forward Contracts - Assets, Notional Amount |  | CAD 25,282 | 3,867 |  |  | CAD 2,205 | 0 |
Customer Counterparties [Member] | Other Liabilities [Member] | Not Designated as Hedging Instrument [Member] |  |  |  |  |  |  |  |
Derivative Counter Party [Line Items] |  |  |  |  |  |  |  |
Forward Contracts Liability, Notional Amount |  |  | € 4,041 | £ 127 |  |  | € 0 | £ 0
Eurodollar Future [Member] | Financial Institution Counterparties [Member] |  |  |  |  |  |  |  |
Derivative Counter Party [Line Items] |  |  |  |  |  |  |  |
Forward Contracts - Assets Estimated Fair Value | $ 77 |  |  |  | $ 0 |  |  |
Forward Contracts, Liability Estimated Fair Value | (37) |  |  |  | (9) |  |  |
Eurodollar Future [Member] | Customer Counterparties [Member] |  |  |  |  |  |  |  |
Derivative Counter Party [Line Items] |  |  |  |  |  |  |  |
Forward Contracts - Assets Estimated Fair Value | 58 |  |  |  | 0 |  |  |
Forward Contracts, Liability Estimated Fair Value | (51) |  |  |  | 0 |  |  |
Foreign Exchange Forward [Member] | Financial Institution Counterparties [Member] |  |  |  |  |  |  |  |
Derivative Counter Party [Line Items] |  |  |  |  |  |  |  |
Forward Contracts, Liability Estimated Fair Value | (142) |  |  |  | (21) |  |  |
Foreign Exchange Forward [Member] | Customer Counterparties [Member] |  |  |  |  |  |  |  |
Derivative Counter Party [Line Items] |  |  |  |  |  |  |  |
Forward Contracts - Assets Estimated Fair Value | 279 |  |  |  | 29 |  |  |
GBP Foreign Exchange Forward [Member] | Financial Institution Counterparties [Member] |  |  |  |  |  |  |  |
Derivative Counter Party [Line Items] |  |  |  |  |  |  |  |
Forward Contracts - Assets Estimated Fair Value | 1 |  |  |  | 0 |  |  |
Forward Contracts, Liability Estimated Fair Value | (9) |  |  |  | (3) |  |  |
GBP Foreign Exchange Forward [Member] | Customer Counterparties [Member] |  |  |  |  |  |  |  |
Derivative Counter Party [Line Items] |  |  |  |  |  |  |  |
Forward Contracts, Liability Estimated Fair Value | $ 0 |  |  |  | $ 0 |  |  |

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