Summary Of Significant Accounting Policies (Effect Of The Adoption Of ASC 606 On Financial Statements) (Details) - USD ($) $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	[2]	Jan. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 74,990	[1]	$ 74,261	$ 84,262	$ 75,872	$ 71,841	[1]	$ 66,116	$ 72,440	$ 69,481	$ 309,385	$ 279,879	$ 270,866
Income tax expense											(3,420)	(3,380)	(4,138)
Net income	6,006	[1]	$ 1,259	$ 4,129	$ 3,104	7,503	[1]	$ 1,478	$ 19,071	$ 3,060	14,498	31,112	9,692
Deferred income taxes	26,235					24,746					26,235	24,746			$ 24,585
Deferred current revenue	9,264					9,850					9,264	9,850			9,495
Retained earnings	47,616					$ 33,056					47,616	33,056			$ 33,250
Balances Without Adoption of ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Income tax expense											(3,356)
Net income											14,641
Deferred income taxes	26,299										26,299
Deferred current revenue	9,471										9,471
Retained earnings	47,473										47,473
Effect Of Change Higher/(Lower) [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Income tax expense											64
Net income											143
Deferred income taxes	(64)										(64)
Deferred current revenue	(207)										(207)
Retained earnings	$ 143										143
Cinema [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue											294,177	$ 263,464	$ 256,922
Cinema [Member] | Balances Without Adoption of ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue											293,970
Cinema [Member] | Effect Of Change Higher/(Lower) [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue											$ 207

[1] Net income for the 4th quarter of 2017 includes approximately $2.5 million net tax benefit from non-recurring items of tax benefit and expense related to the Tax Cuts and Jobs Act enacted December 2017 and dissolution of a non-operating foreign subsidiary.

[2] Certain prior year balances have been reclassified to conform to the 2017 presentation (see Note 2 - Summary of Significant Accounting Policies - Reclassifications).