Summary of Significant Accounting Policies Derivative Instruments and Hedging Activities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Derivative [Line Items]
Derivative, Notional Amount	$ 3,827	$ 5,423
Derivative Asset, Fair Value, Gross Asset	312
Derivative Instruments, Loss (Gain) Recognized in Income, Net	$ (417)	221	$ 150
Derivative Liability, Fair Value, Gross Asset		$ (85)
Number of Foreign Currency Derivatives Held	6,641	2,484	1,456