Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 30,892	$ 32,439
Accounts receivable (net of allowance of $512 and $551 at March 31, 2022 and December 31, 2021, respectively)	12,758	16,012
Notes receivable	22,400	22,400
Inventories	1,781	2,192
Prepaids and other current assets	4,733	3,485
Total current assets	72,564	76,528
Property, plant and equipment, at cost	312,959	312,979
Less accumulated depreciation	(304,868)	(304,157)
Property, plant and equipment, net	8,091	8,822
Operating lease right-of-use assets	16,982	17,648
Deferred income taxes, net	232	257
Other assets	2,194	2,197
Total assets	100,063	105,452
Current liabilities:
Accounts payable	5,832	7,821
Accrued compensation and benefits	5,049	4,932
Other accrued expense	4,937	4,573
Contract liabilities	10,652	10,592
Total current liabilities	26,470	27,918
Long-term pension liabilities	14,365	14,275
Long-term operating lease liabilities	18,529	19,181
Other post-employment benefits	1,337	1,349
Other liabilities	155	152
Total liabilities	60,856	62,875
Shareholders' equity:
Preferred stock, $0.01 par value; Authorized 2,000,000 shares; none issued
Treasury stock, Series A, at cost; 478,465 shares held at March 31, 2022 and December 31, 2021	(13,443)	(13,443)
Additional paid-in capital	494,563	494,563
Accumulated other comprehensive loss	(32,276)	(32,406)
Accumulated deficit	(409,695)	(406,195)
Total shareholders’ equity	39,207	42,577
Total liabilities and shareholders’ equity	100,063	105,452
Series A [Member]
Shareholders' equity:
Common stock, $0.01 par value; Authorized 31,250,000 shares	52	52
Series B [Member]
Shareholders' equity:
Common stock, $0.01 par value; Authorized 31,250,000 shares	$ 6	$ 6