Debt (Long-term Debt) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Notes Payable, less current maturities and unamortized debt discount	$ 155,757
Less current maturities	(3,290)	$ (2,301)
Total long-term debt	155,757	108,843
Less unamortized debt discount	2,890	2,700
Senior Secured Notes [Member]
Debt Instrument [Line Items]
Notes Payable, less current maturities and unamortized debt discount	159,047	111,144
Less unamortized debt discount	$ 2,890	$ 2,668
Implied interest rate	7.00%	7.70%