Summary Of Significant Accounting Policies (Effect Of The Adoption Of ASC 606 On Financial Statements) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 74,261	$ 66,116	$ 234,395	$ 208,037
Income tax expense	(1,482)	(750)	(4,618)	(8,316)
Net income	1,297	1,577	9,405	23,677
Deferred income taxes	25,285		25,285		$ 24,585	$ 24,746
Deferred current revenue	6,796		6,796		9,495	9,850
Retained earnings	42,655		42,655		$ 33,250	$ 33,056
Balances Without Adoption of ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Income tax expense	(1,637)		(4,704)
Net income	1,656		9,582
Deferred income taxes	25,199		25,199
Deferred current revenue	6,533		6,533
Retained earnings	42,832		42,832
Effect Of Change Higher/(Lower) [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Income tax expense	(155)		(86)
Net income	(359)		(177)
Deferred income taxes	86		86
Deferred current revenue	263		263
Retained earnings	(177)		(177)
Cinema [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	70,671	$ 62,059	223,109	$ 196,062
Cinema [Member] | Balances Without Adoption of ASC 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	71,185		223,372
Cinema [Member] | Effect Of Change Higher/(Lower) [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ (514)		$ (263)