Summary of Significant Accounting Policies Derivative Instruments, Gain (Loss) by Hedging Relationship, by Income Statement Location (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$ 58	$ 100
Change in unrealized loss on hedge contracts	0	0	$ (40)
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	40
Foreign Exchange Contract [Member] | Interest and Other Income (Expense), Net [Member] | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (220)	$ 110