Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Capital In Excess of Par Value	Accumulated Other Comprehensive Loss	Retained Earnings	Non-controlling Interest in Consolidated Subsidiaries
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment for adoption of ASUs	$ 174	$ 0	$ 0	$ 0	$ 174	$ 0
Beginning balance at Dec. 31, 2018	1,593,444	10,414	628,108	(481)	752,840	202,563
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(553,828)	0	0	0	(553,879)	51
Reclassification Adjustment from AOCI for Write-down of Securities, Tax	(47)
Other comprehensive income (loss)	481	0	0	481	0	0
Total comprehensive income (loss)	(553,347)
Distribution to non-controlling interest	(918)	0	0	0	0	(918)
Activity in employee compensation plans	16,282	177	16,044	0	0	61
Ending balance at Dec. 31, 2019	1,055,635	10,591	644,152	0	199,135	201,757
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(890,624)	0	0	0	(931,012)	40,388
Reclassification Adjustment from AOCI for Write-down of Securities, Tax	0
Total comprehensive income (loss)	(890,624)
Activity in employee compensation plans	6,169	113	6,001	0	0	55
Ending balance at Aug. 31, 2020	171,180	10,704	650,153	0	(731,877)	242,200
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Successor equity	197,323	120	197,203	0	0	0
Ending balance at Sep. 01, 2020	439,523	120	197,203	0	0	242,200
Beginning balance at Aug. 31, 2020	171,180	10,704	650,153	0	(731,877)	242,200
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(13,988)	0	0	0	(18,140)	4,152
Reclassification Adjustment from AOCI for Write-down of Securities, Tax	0
Total comprehensive income (loss)	(13,988)
Activity in employee compensation plans	58	0	39	0	0	19
Ending balance at Dec. 31, 2020	$ 425,593	$ 120	$ 197,242	$ 0	$ (18,140)	$ 246,371