Other Liabilities (Summary Of Other Liabilities Including Pension) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Aug. 29, 2014
Other Liabilities [Abstract]
Liability for demolition costs	$ 2,808	$ 2,928
Accrued pension	684	684
Security deposit payable	72	132
Finance lease liabilities	45	49
Other	41	33
Other current liabilities	3,650	3,826
Lease make-good provision	7,611	7,408
Accrued pension	3,718	4,048	$ 7,500
Deferred rent liability	2,180	2,897
Environmental reserve	1,656	1,656
Lease liability	5,900	5,900
Acquired leases	23	31
Finance lease liabilities	36	69
Other		8
Other non-current liabilities	$ 21,124	$ 22,017