Debt (U.S. Corporate Office Term Loan) (Narrative) (Details) - USD ($) $ in Thousands			3 Months Ended		12 Months Ended
	Jun. 26, 2017	Dec. 13, 2016	Mar. 31, 2018		Dec. 31, 2017
Debt Instrument [Line Items]
Contractual facility			$ 275,511		$ 271,732
U.S. Corporate Office Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument term		10 years
Contractual facility		$ 8,400	$ 9,665	[1]	$ 9,719	[2]
Interest rate	4.44%	4.64%
Debt increase	$ 1,500

[1] The loan for our Minetta & Orpheum Theatres was obtained from Santander Bank. 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. 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 March 31, 2018 an additional $1.2 million had been advanced.

[2] The loan for our Minetta & Orpheum Theatres was obtained from Santander Bank. 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.. 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.