Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jan. 01, 2017
Accounting Policies [Abstract]
Stock-based compensation expense	$ 782	$ 1,011	$ 2,930	$ 4,334
Retained Deficit | Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effects on Equity and Net Assets					$ 2,300
Deferred income taxes | Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effects on Equity and Net Assets					$ (2,300)