Significant Accounting Policies, Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Components of accumulated other comprehensive loss [Roll Forward]
Balance, beginning of period			$ 57,308
Current-period other comprehensive income	$ 21	$ (15)	193	$ 69
Balance, end of period	56,601		56,601
Accumulated Other Comprehensive Loss [Member]
Components of accumulated other comprehensive loss [Roll Forward]
Balance, beginning of period			(2,329)
Balance, end of period	(2,136)		(2,136)
Foreign Currency Translation Losses [Member]
Components of accumulated other comprehensive loss [Roll Forward]
Balance, beginning of period			(2,288)
Current-period other comprehensive income			175
Balance, end of period	(2,113)		(2,113)
Unrealized Losses on Investments [Member]
Components of accumulated other comprehensive loss [Roll Forward]
Balance, beginning of period			(41)
Current-period other comprehensive income			18
Balance, end of period	$ (23)		$ (23)