Debt (Schedule of Construction Financing) (Details) - Union Square Construction Financing [Member] $ in Thousands		6 Months Ended		12 Months Ended
		Jun. 30, 2018 USD ($) item		Dec. 31, 2017	[2]	Dec. 29, 2016 USD ($)
Debt Instrument [Line Items]
Facility Limit		$ 57,500
Advanced-to-Date		19,888
Remaining Facility		$ 37,612
Maturity date		Dec. 29, 2019	[1]	Dec. 29, 2019
Number of extension options | item		2
Extension period		1 year
Senior Loan [Member]
Debt Instrument [Line Items]
Advanced-to-Date		$ 7,500
Tammany Mezz Investor, LLC [Member] | Mezzanine Loan [Member]
Debt Instrument [Line Items]
Facility Limit		7,500
Advanced-to-Date		$ 7,500
Spread over LIBOR		10.00%
Maturity date	[3]	Dec. 29, 2019
Bank Of The Ozarks [Member]
Debt Instrument [Line Items]
Facility Limit						$ 8,000
Advanced-to-Date						$ 8,000
Bank Of The Ozarks [Member] | Senior Loan [Member]
Debt Instrument [Line Items]
Spread over LIBOR		4.25%
Bank Of The Ozarks [Member] | Senior Loans, Including Building And Project Loan [Member]
Debt Instrument [Line Items]
Facility Limit		$ 50,000
Advanced-to-Date		12,388
Remaining Facility		$ 37,612
Maturity date	[3]	Dec. 29, 2019
Minimum [Member] | Tammany Mezz Investor, LLC [Member] | Mezzanine Loan [Member]
Debt Instrument [Line Items]
Interest rate		10.50%
Minimum [Member] | Bank Of The Ozarks [Member] | Senior Loan [Member]
Debt Instrument [Line Items]
Interest rate		4.75%
Maximum [Member] | New York State [Member]
Debt Instrument [Line Items]
Interest rate		16.00%

[1] 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.

[2] 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.

[3] Allowable for up to two (2) extension request options, one (1) year for each extension request.