Description Of Business And Segment Reporting (Summary Of Results Of Operations For Principal Business Segments) (Details) $ in Thousands		3 Months Ended										12 Months Ended
		Dec. 31, 2020 USD ($)	[1]	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	[1]	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue		$ 15,021		$ 10,191	$ 3,422	$ 49,228	$ 68,880		$ 70,386	$ 76,009	$ 61,493	$ 77,862	$ 276,768	$ 308,931
Depreciation and amortization												(22,317)	(22,747)	(22,275)
General and administrative expense												(16,998)	(25,395)	(27,337)
Impairment of long-lived assets												(217)
Total costs and expenses												(139,175)	(267,645)	(285,307)
Segment operating income (loss)												$ (61,313)	9,123	23,624
Number of operating segments | segment												2
Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue												$ 79,977	284,094	317,958
Total of services and products (excluding depreciation and amortization)												(101,758)	(226,829)	(244,722)
Depreciation and amortization												(21,347)	(22,333)	(21,881)
Total costs and expenses												(127,496)	(255,624)	(272,653)
Segment operating income (loss)												(47,519)	28,470	45,305
Intersegment Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	[2]											(2,115)	(7,326)	(9,027)
Total of services and products (excluding depreciation and amortization)	[2]											(2,115)	(7,326)	(9,027)
Cinema Exhibition [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Impairment of long-lived assets												(217)
Cinema Exhibition [Member] | Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue												67,014	262,189	293,723
Total of services and products (excluding depreciation and amortization)												(93,180)	(217,376)	(234,818)
Depreciation and amortization												(15,246)	(16,940)	(16,314)
Total costs and expenses												(112,070)	(238,860)	(254,856)
Segment operating income (loss)												(45,056)	23,329	38,867
Cinema Exhibition [Member] | Intersegment Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total of services and products (excluding depreciation and amortization)	[2]											(2,115)	(7,326)	(9,027)
Real Estate [Member] | Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue												12,963	21,905	24,235
Total of services and products (excluding depreciation and amortization)												(8,578)	(9,453)	(9,904)
Depreciation and amortization												(6,101)	(5,393)	(5,567)
Total costs and expenses												(15,426)	(16,764)	(17,797)
Segment operating income (loss)												(2,463)	5,141	6,438
Real Estate [Member] | Intersegment Eliminations [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue	[2]											(2,115)	(7,326)	(9,027)
Segment [Member] | Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
General and administrative expense												(4,174)	(6,462)	(6,050)
Segment [Member] | Cinema Exhibition [Member] | Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
General and administrative expense												(3,427)	(4,544)	(3,724)
Segment [Member] | Real Estate [Member] | Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
General and administrative expense												(747)	(1,918)	(2,326)
Third Party [Member] | Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue												77,862	276,768	308,931
Total of services and products (excluding depreciation and amortization)												(99,643)	(219,503)	(235,695)
Third Party [Member] | Cinema Exhibition [Member] | Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue												67,014	262,189	293,723
Total of services and products (excluding depreciation and amortization)												(91,065)	(210,050)	(225,791)
Third Party [Member] | Real Estate [Member] | Operating Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Revenue												10,848	14,579	15,208
Total of services and products (excluding depreciation and amortization)												$ (8,578)	$ (9,453)	$ (9,904)

[1] Since previously published financial statements have been corrected, there is no impact on the fourth quarter results for 2019 or for the full year of 2020 and so no data is displayed here.

[2] Inter-segment Revenues and Operating Expense relates to the internal charge between the two segments where the cinema operates within real estate owned within the group.