Income Taxes (Net Operating Loss Carryforwards and Tax Credits) (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Tax Credit Carryforward [Line Items]
Receivable for AMT tax credit carryforwards	$ 343
Federal [Member]
Tax Credit Carryforward [Line Items]
Operating loss carryforwards	215,326
Tax credit carryforwards, research	$ 8,962
Ownership change, percent increase in equity ownership by 5% shareholder	50.00%
Minimum percent equity ownership by shareholder for ownership change considerations	5.00%
State [Member]
Tax Credit Carryforward [Line Items]
Operating loss carryforwards	$ 11,444
Tax credit carryforwards, research	4,019
Foreign [Member]
Tax Credit Carryforward [Line Items]
Operating loss carryforwards	38,578
Tax credit carryforwards, research	27,322
General foreign tax credit	$ 1,655
China, Income tax holiday, reduced statutory rate	15.00%
China, Income tax holiday, expiration date	2018
Canada Revenue Agency [Member] | Foreign [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, research	$ 119,447