CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings (Accumulated Deficit)	Treasury Stock
Balance at Dec. 31, 2018	$ 1,212,098	$ 210	$ 1,771,730	$ (559,842)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock activity and shares exchanged for tax withholding	(1,506)				(1,506)
Stock-based compensation	3,940		3,940
Retirement of treasury stock	0		(1,506)		1,506
Net income (loss)	(98,139)			(98,139)
Balance at Jun. 30, 2019	1,116,393	210	1,774,164	(657,981)	0
Balance at Mar. 31, 2019	1,116,475	210	1,772,336	(656,071)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock activity and shares exchanged for tax withholding	(22)				(22)
Stock-based compensation	1,850		1,850
Retirement of treasury stock	0		(22)		22
Net income (loss)	(1,910)			(1,910)
Balance at Jun. 30, 2019	1,116,393	210	1,774,164	(657,981)	0
Balance at Dec. 31, 2019	1,083,318	211	1,777,779	(694,672)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock activity and shares exchanged for tax withholding	(653)	1			(654)
Stock-based compensation	2,781		2,781
Retirement of treasury stock	0		(654)		654
Net income (loss)	(1,083,267)			(1,083,267)
Balance at Jun. 30, 2020	2,179	212	1,779,906	(1,777,939)	0
Balance at Mar. 31, 2020	68,472	212	1,778,571	(1,710,311)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock activity and shares exchanged for tax withholding	(18)				(18)
Stock-based compensation	1,353		1,353
Retirement of treasury stock	0		(18)		18
Net income (loss)	(67,628)			(67,628)
Balance at Jun. 30, 2020	$ 2,179	$ 212	$ 1,779,906	$ (1,777,939)	$ 0