Debt (Summary Of Notes Payable) (Details) - USD ($)						6 Months Ended		12 Months Ended
		Jun. 26, 2017	Dec. 29, 2016	Dec. 13, 2016	Mar. 03, 2016	Jun. 30, 2018		Dec. 31, 2017
Debt Instrument [Line Items]
Contractual facility						$ 270,746,000		$ 271,732,000
Balance Gross						161,763,000		134,501,000
Balance Net						158,267,000	[1]	130,525,000	[2]
Deferred financing costs, net						$ 3,500,000		$ 4,000,000
Trust Preferred Securities [Member]
Debt Instrument [Line Items]
Maturity date						Apr. 30, 2027		Apr. 30, 2027
Contractual facility						$ 27,913,000		$ 27,913,000
Balance Gross						27,913,000		27,913,000
Balance Net						$ 27,574,000	[1]	$ 27,554,000	[2]
Stated interest rate						6.36%		5.38%
Effective interest rate						6.36%	[3]	5.38%	[4]
US Bank Of America Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date						Nov. 28, 2019		Nov. 28, 2019
Contractual facility					$ 55,000,000	$ 55,000,000		$ 55,000,000
Balance Gross						31,000,000		31,000,000
Balance Net						$ 31,000,000	[1]	$ 31,000,000	[2]
Stated interest rate						5.09%		4.57%
Effective interest rate						5.09%	[3]	4.57%	[4]
US Bank Of America Line Of Credit [Member]
Debt Instrument [Line Items]
Maturity date						Oct. 31, 2019		Oct. 31, 2019
Contractual facility						$ 5,000,000		$ 5,000,000
Stated interest rate						5.08%		4.57%
Effective interest rate						5.08%	[3]	4.57%	[4]
US Bank Of America Digital Projector Loan [Member]
Debt Instrument [Line Items]
Maturity date						Dec. 28, 2019
Contractual facility						$ 3,830,000
Balance Gross						3,830,000
Balance Net	[1]					$ 3,830,000
Stated interest rate						5.00%
Effective interest rate	[3]					5.00%
US Cinema 1, 2, 3 Term Loan [Member]
Debt Instrument [Line Items]
Maturity date						Sep. 01, 2019	[5]	Sep. 01, 2019	[6]
Contractual facility						$ 19,294,000	[5]	$ 19,500,000	[6]
Balance Gross						19,294,000	[5]	19,500,000	[6]
Balance Net						$ 18,975,000	[1],[5]	$ 19,105,000	[2],[6]
Stated interest rate						3.25%	[5]	3.25%	[6]
Effective interest rate						3.25%	[3],[5]	3.25%	[4],[6]
Minetta And Orpheum Theatres Loan [Member]
Debt Instrument [Line Items]
Maturity date						Nov. 01, 2018	[5]	Jun. 01, 2018	[6]
Contractual facility						$ 7,500,000	[5]	$ 7,500,000	[6]
Balance Gross						7,500,000	[5]	7,500,000	[6]
Balance Net						$ 7,476,000	[1],[5]	$ 7,470,000	[2],[6]
Stated interest rate						4.75%	[5]	4.13%	[6]
Effective interest rate						4.75%	[3],[5]	4.13%	[4],[6]
U.S. Corporate Office Term Loan [Member]
Debt Instrument [Line Items]
Maturity date						Jan. 01, 2027	[5]	Jan. 01, 2027	[6]
Contractual facility				$ 8,400,000		$ 9,609,000	[5]	$ 9,719,000	[6]
Balance Gross						9,609,000	[5]	9,719,000	[6]
Balance Net						$ 9,479,000	[1],[5]	$ 9,582,000	[2],[6]
Effective interest rate						4.61%	[3],[5]	4.61%	[4],[6]
Debt increase		$ 1,500,000
Additional amount borrowed								$ 0
Union Square Construction Financing [Member]
Debt Instrument [Line Items]
Maturity date						Dec. 29, 2019	[5]	Dec. 29, 2019	[6]
Contractual facility			$ 57,500,000			$ 57,500,000	[5]	$ 57,500,000	[6]
Balance Gross						19,888,000	[5]	8,000,000	[6]
Balance Net						$ 17,263,000	[1],[5]	$ 5,033,000	[2],[6]
Stated interest rate	[6]							5.81%
Effective interest rate						8.52%	[3],[5]	5.81%	[4],[6]
Additional amount borrowed						$ 11,900,000
NAB Corporate Term Loan [Member]
Debt Instrument [Line Items]
Maturity date	[7]					Dec. 31, 2019
Contractual facility	[7]					$ 49,203,000
Balance Gross	[7]					42,729,000
Balance Net	[1],[7]					$ 42,670,000
Stated interest rate	[7]					3.02%
Effective interest rate	[3],[7]					3.02%
NAB Corporate Loan Facility [Member]
Debt Instrument [Line Items]
Maturity date	[8]							Jun. 30, 2019
Contractual facility	[8]							$ 51,970,000
Balance Gross	[8]							30,869,000
Balance Net	[2],[8]							$ 30,781,000
Stated interest rate	[8]							3.66%
Effective interest rate	[4],[8]							3.66%
Westpac Bank Corporate (General/Non-construction) Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date						Dec. 31, 2019	[7]	Dec. 31, 2019	[8]
Contractual facility						$ 23,706,000	[7]	$ 24,850,000	[8]
Stated interest rate						3.70%	[7]	3.70%	[8]
Effective interest rate						3.70%	[3],[7]	3.70%	[4],[8]
Westpac Bank Corporate (Construction) Credit Facility [Member]
Debt Instrument [Line Items]
Maturity date						Dec. 31, 2018	[7]	Dec. 31, 2018	[8]
Contractual facility						$ 12,191,000	[7]	$ 12,780,000	[8]
Stated interest rate						3.70%	[7]	3.70%	[8]
Effective interest rate						3.70%	[3],[7]	3.70%	[4],[8]
Minimum [Member] | U.S. Corporate Office Term Loan [Member]
Debt Instrument [Line Items]
Stated interest rate						4.44%		4.44%
Minimum [Member] | Union Square Construction Financing [Member]
Debt Instrument [Line Items]
Stated interest rate						6.06%
Maximum [Member] | U.S. Corporate Office Term Loan [Member]
Debt Instrument [Line Items]
Stated interest rate						4.64%		4.64%
Maximum [Member] | Union Square Construction Financing [Member]
Debt Instrument [Line Items]
Stated interest rate						12.10%

[1] Net of deferred financing costs amounting to $3.5 million.

[2] Net of deferred financing costs amounting to $4.0 million.

[3] Both interest rate derivatives associated with the Trust Preferred Securities and Bank of America Credit Facility expired in October 2017 so the effective interest rate no longer applies as of June 30, 2018.

[4] Both interest rate derivatives associated with the Trust Preferred Securities and Bank of America Credit Facility expired in October 2017 so the effective interest rate no longer applies as of December 31, 2017.

[5] The term loan for our Cinema 1,2,3 Theatre was refinanced during the third quarter of 2016 with Valley National Bank. The term loan, which is collateralized by our new U.S Corporate Headquarters office building, was obtained with Citizens Asset Finance Inc. The loan for our Minetta and Orpheum Theatres was obtained from Santander Bank. In December 2016, we completed the negotiation of the construction financing for our Union Square redevelopment project, $8.0 million of which was advanced from the total construction loan limit of $57.5 million on December 29, 2016. As of June 30, 2018 an additional $11.9 million had been advanced.

[6] The term loan for our Cinema 1,2,3 Theatre was refinanced during the third quarter of 2016 with Valley National Bank. The term loan, which is collateralized by our new U.S Corporate Headquarters office building, was obtained with Citizens Asset Finance, Inc.. The loan for our Minetta & Orpheum Theatres was obtained from Santander Bank. In December 2016, we completed the negotiation of the construction financing for our Union Square redevelopment project, $8.0 million of which was advanced from the total construction loan limit of $57.5 million on December 29, 2016. As of December 31, 2017 no further advances had been made under this financing agreement.

[7] The contractual facilities and outstanding balances of the FC-denominated borrowings were translated into U.S. dollars based on the applicable exchange rates as of June 30, 2018.

[8] The contractual facilities and outstanding balances of the FC-denominated borrowings were translated into U.S. dollars based on the applicable exchange rates as of December 31, 2017.