Income Taxes (Schedule Of Deferred Tax Assets And Deferred Tax Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Abstract]
Accounts receivable	$ 357	$ 144
Accrued expenses and other current liabilities	422	743
Unearned revenue	33	51
Stock-based compensation	1,026	1,060
Other	53	62
Net operating loss carry forwards	21,087	37,464
Gross deferred tax assets	22,978	39,524
Net deferred tax assets	22,978	39,524
Depreciation and amortization	46,180	68,859
Foreign deferred tax liabilities	953	1,047
Intangible assets	1,167	1,425
Deferred subpart F income	10,054	6,512
Gross deferred tax liabilities	58,354	77,843
Net deferred tax liability	$ 35,376	$ 38,319