Income Taxes (Schedule Of Deferred Tax Assets And Deferred Tax Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Abstract]
Accounts receivable	$ 144	$ 68
Accrued expenses and other current liabilities	743	886
Unearned revenue	51	198
Stock-based compensation	1,060	744
Other	62	89
Net operating loss carry forwards	37,464	34,758
Gross deferred tax assets	39,524	36,743
Net deferred tax assets	39,524	36,743
Depreciation and amortization	68,859	65,609
Foreign deferred tax liabilities	1,047	943
Intangible assets	1,425	1,734
Deferred subpart F income	6,512	4,310
Gross deferred tax liabilities	77,843	72,596
Net deferred tax liability	$ 38,319	$ 35,853