Derivative Instruments and Hedging Activities Open Foreign Currency Contracts (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Net Unrealized Gain (Loss)	$ (1,685)	$ 298
Cash Flow Hedging | Foreign Exchange Contract
Derivative [Line Items]
Notional Amounts (in U.S. Dollars)	169,274
Net Unrealized Gain (Loss)	(1,685)
Cash Flow Hedging | Foreign Exchange Contract | Australian Dollar
Derivative [Line Items]
Notional Amounts (in U.S. Dollars)	27,947
Net Unrealized Gain (Loss)	(308)
Cash Flow Hedging | Foreign Exchange Contract | Canadian Dollar
Derivative [Line Items]
Notional Amounts (in U.S. Dollars)	136,019
Net Unrealized Gain (Loss)	(1,697)
Cash Flow Hedging | Foreign Exchange Contract | Japanese Yen
Derivative [Line Items]
Notional Amounts (in U.S. Dollars)	907
Net Unrealized Gain (Loss)	(18)
Cash Flow Hedging | Foreign Exchange Contract | Mexican Peso
Derivative [Line Items]
Notional Amounts (in U.S. Dollars)	4,401
Net Unrealized Gain (Loss)	$ 338