Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Income Taxes [Abstract]
Statutory income tax benefit	21.00%	35.00%
Tax Cuts and Jobs Act of 2017, Valuation Allowance, Federal		$ 4,512
Tax Cuts and Jobs Act of 2017, Valuation Allowance, State, If Recognized		400
Gross deferred tax asset		50,732
Valuation allowance		45,811
Net deferred tax asset		4,921
Deferred tax liabilities, gross		8,587
Net operating loss carryforwards for U.S. federal income tax purposes		156,598
Research and experimentation credit carryforwards		3,452
Alternative minimum tax credit carryforwards		$ 0