Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Capital in Excess of Par Value	Retained Earnings (Deficit)	Non-controlling Interest in Consolidated Subsidiaries
Stockholders' equity, beginning balance at Dec. 31, 2020	$ 425,593	$ 120	$ 0	$ 197,242	$ (18,140)	$ 246,371
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(591)				(1,937)	1,346
Activity in stock-based compensation plans	90			74		16
Stockholders' equity, ending balance at Mar. 31, 2021	425,092	120	0	197,316	(20,077)	247,733
Stockholders' equity, beginning balance at Dec. 31, 2021	399,668	120	(51,965)	198,171	41,071	212,271
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(52,705)				(46,877)	(5,828)
Distributions to non-controlling interests	(9,479)					(9,479)
Deconsolidation of Superior	(196,964)					(196,964)
Activity in stock-based compensation plans	1,038			1,038
Stockholders' equity, ending balance at Mar. 31, 2022	$ 141,558	$ 120	$ (51,965)	$ 199,209	$ (5,806)	$ 0