Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Gains (Losses) [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2018	$ 3,584,653	$ 1,444	$ 2,018,143	$ 1,769,415	$ 21	$ (204,370)
Beginning Balance, shares at Dec. 31, 2018		144,383,662				6,945,309
Net loss	(282,444)			(282,444)
Stock-based compensation, net of tax	3,152	$ 4	4,529			$ (1,381)
Stock-based compensation, net of tax, shares		385,416				129,456
Net loss on investments	(32)				(32)
Net (loss) gain on derivative financial instruments	(5)				(5)
Ending Balance at Sep. 30, 2019	3,305,324	$ 1,448	2,022,672	1,486,971	(16)	$ (205,751)
Ending Balance, shares at Sep. 30, 2019		144,769,078				7,074,765
Beginning Balance at Jun. 30, 2019	3,398,897	$ 1,448	2,021,095	1,582,099	(6)	$ (205,739)
Beginning Balance, shares at Jun. 30, 2019		144,764,125				7,073,498
Net loss	(95,128)			(95,128)
Stock-based compensation, net of tax	1,565		1,577			$ (12)
Stock-based compensation, net of tax, shares		4,953				1,267
Net loss on investments	(8)				(8)
Net (loss) gain on derivative financial instruments	(2)				(2)
Ending Balance at Sep. 30, 2019	3,305,324	$ 1,448	2,022,672	1,486,971	(16)	$ (205,751)
Ending Balance, shares at Sep. 30, 2019		144,769,078				7,074,765
Beginning Balance at Dec. 31, 2019	3,232,210	$ 1,448	2,024,347	1,412,201	(18)	$ (205,768)
Beginning Balance, shares at Dec. 31, 2019		144,781,766				7,077,856
Net loss	(1,105,366)			(1,105,366)
Stock-based compensation, net of tax	5,242	$ 5	5,632			$ (395)
Stock-based compensation, net of tax, shares		482,099				131,698
Net (loss) gain on derivative financial instruments	18				18
Ending Balance at Sep. 30, 2020	2,132,104	$ 1,453	2,029,979	306,835		$ (206,163)
Ending Balance, shares at Sep. 30, 2020		145,263,865				7,209,554
Beginning Balance at Jun. 30, 2020	2,230,689	$ 1,453	2,029,978	405,441	(21)	$ (206,162)
Beginning Balance, shares at Jun. 30, 2020		145,258,536				7,208,189
Net loss	(98,606)			(98,606)
Stock-based compensation, net of tax			1			$ (1)
Stock-based compensation, net of tax, shares		5,329				1,365
Net (loss) gain on derivative financial instruments	21				$ 21
Ending Balance at Sep. 30, 2020	$ 2,132,104	$ 1,453	$ 2,029,979	$ 306,835		$ (206,163)
Ending Balance, shares at Sep. 30, 2020		145,263,865				7,209,554