Commitments and Contingencies (Narrative) (Details) $ in Thousands				3 Months Ended		9 Months Ended
	Feb. 24, 2018 USD ($)	Jan. 09, 2017 shareholder	Mar. 17, 2016 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Operating Leased Assets [Line Items]
Rent expense				$ 900	$ 600	$ 2,600	$ 2,500
Settlement awarded to other party	$ 750		$ 4,700
Number of shareholders in litigation | shareholder		2
Minimum
Operating Leased Assets [Line Items]
Severance payment, prior to change in control						6 months
Severance payment, period following change in control						18 months
Maximum
Operating Leased Assets [Line Items]
Severance payment, prior to change in control						24 months
Severance payment, period following change in control						24 months