Commitments and Contingencies (Narrative) (Details) $ in Thousands			1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 24, 2018 USD ($)	Mar. 17, 2016 USD ($)	Jan. 31, 2017 shareholder	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)
Operating Leased Assets [Line Items]
Rent expense				$ 800	$ 1,000	$ 1,800	$ 1,900
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