Income Taxes (Summary of Operating Loss Carryforwards and Tax Credit Carryforwards) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Net deferred tax asset, net operating loss	$ 19,058	$ 22,035
Total net deferred tax asset	22,472	25,591
Total valuation allowance	15,522	14,492
Foreign tax authority
Operating Loss Carryforwards [Line Items]
Net deferred tax asset, net operating loss	2,340	1,438
Valuation allowance, net operating loss	2,340	1,438
State and local jurisdiction
Operating Loss Carryforwards [Line Items]
Net deferred tax asset, net operating loss	16,624	16,948
Valuation allowance, net operating loss	13,182	13,054
Net deferred tax asset, tax credit carryforwards, research	1,198	1,870
Net deferred tax asset, alternative minimum tax credit	2,310	5,335
Valuation allowance, tax credit	$ 0	$ 0