Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital In Excess of Par Value [Member]	Accumulated other comprehensive income (loss) [Member]	Retained earnings [Member]	Non-controlling interests in consolidated subsidiaries [Member]
Cumulative effect adjustment for adoption of ASUs	$ 174	$ 0	$ 0	$ 0	$ 174	$ 0
Stockholders' equity, beginning balance at Dec. 31, 2018	1,593,444	10,414	628,108	(481)	752,840	202,563
Net Income (loss)	(2,282)	0	0	0	(3,504)	1,222
Other comprehensive income (loss)	24	0	0	24	0	0
Total comprehensive loss	(2,258)
Distributions to non-controlling interest	(918)	0	0	0	0	(918)
Activity in employee compensation plans	5,417	164	5,253	0	0	0
Stockholders' equity, ending balance at Mar. 31, 2019	1,595,859	10,578	633,361	(457)	749,510	202,867
Stockholders' equity, beginning balance at Dec. 31, 2019	1,055,635	10,591	644,152	0	199,135	201,757
Net Income (loss)	(803,674)	0	0	0	(770,494)	(33,180)
Other comprehensive income (loss)	0
Total comprehensive loss	(803,674)
Activity in employee compensation plans	2,525	103	2,391	0	0	31
Stockholders' equity, ending balance at Mar. 31, 2020	$ 254,486	$ 10,694	$ 646,543	$ 0	$ (571,359)	$ 168,608