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 (deficit) [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)	(10,299)	0	0	0	(12,013)	1,714
Other comprehensive income (loss)	(6)	0	0	(6)	0	0
Total comprehensive loss	(10,305)
Distributions to non-controlling interest	(918)	0	0	0	0	(918)
Activity in employee compensation plans	10,837	176	10,661	0	0	0
Stockholders' equity, ending balance at Jun. 30, 2019	1,593,232	10,590	638,769	(487)	741,001	203,359
Stockholders' equity, beginning balance at Mar. 31, 2019	1,595,859	10,578	633,361	(457)	749,510	202,867
Net Income (loss)	(8,017)	0	0	0	(8,509)	492
Other comprehensive income (loss)	(30)	0	0	(30)	0	0
Total comprehensive loss	(8,047)
Activity in employee compensation plans	5,420	12	5,408	0	0	0
Stockholders' equity, ending balance at Jun. 30, 2019	1,593,232	10,590	638,769	(487)	741,001	203,359
Stockholders' equity, beginning balance at Dec. 31, 2019	1,055,635	10,591	644,152	0	199,135	201,757
Net Income (loss)	(1,019,239)	0	0	0	(986,143)	(33,096)
Other comprehensive income (loss)	0
Total comprehensive loss	(1,019,239)
Activity in employee compensation plans	4,136	113	3,976	0	0	47
Stockholders' equity, ending balance at Jun. 30, 2020	40,532	10,704	648,128	0	(787,008)	168,708
Stockholders' equity, beginning balance at Mar. 31, 2020	254,486	10,694	646,543	0	(571,359)	168,608
Net Income (loss)	(215,565)	0	0	0	(215,649)	84
Other comprehensive income (loss)	0
Total comprehensive loss	(215,565)
Activity in employee compensation plans	1,611	10	1,585	0	0	16
Stockholders' equity, ending balance at Jun. 30, 2020	$ 40,532	$ 10,704	$ 648,128	$ 0	$ (787,008)	$ 168,708