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 (£)
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