Commitments and Contingencies (Narrative) (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2017 shareholder	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)
Operating Leased Assets [Line Items]
Rent expense		$ 900	$ 900
Settlement costs from litigation			4,700
Number of shareholders in litigation | shareholder	2
Termination costs		$ 13,071	$ 15,662
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