Other Liabilities (Summary Of Other Liabilities Including Pension) (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Aug. 29, 2014
Other Liabilities [Abstract]
Liability for demolition costs	$ 2,840	$ 2,928
Accrued pension	684	684
Security deposit payable	52	132
Finance lease liabilities	49	49
Other	33	33
Other current liabilities	3,658	3,826
Lease make-good provision	7,670	7,408
Accrued pension	3,829	4,048	$ 7,500
Deferred rent liability	2,035	2,897
Environmental reserve	1,656	1,656
Lease liability	5,900	5,900
Acquired leases	26	31
Finance lease liabilities	44	69
Other	1	8
Other non-current liabilities	$ 21,161	$ 22,017