Derivative Financial Instruments Gains and Losses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, (Gain) Loss [Line Items]
Derivative settlement gain or loss	$ (70,305)	$ (24,722)	$ (286,270)	$ (23,843)
Net derivative (gain) loss	63,871	(100,889)	(314,269)	(3,463)
Oil Contracts [Member]
Derivative Instruments, (Gain) Loss [Line Items]
Derivative settlement gain or loss	(68,907)	2,246	(261,095)	14,304
Net derivative (gain) loss	30,641	(83,984)	(360,649)	67,261
Gas Contracts [Member]
Derivative Instruments, (Gain) Loss [Line Items]
Derivative settlement gain or loss	(896)	(12,210)	(16,575)	(13,744)
Net derivative (gain) loss	31,548	(4,228)	46,537	(36,337)
NGL Contracts [Member]
Derivative Instruments, (Gain) Loss [Line Items]
Derivative settlement gain or loss	(502)	(14,758)	(8,600)	(24,403)
Net derivative (gain) loss	$ 1,682	$ (12,677)	$ (157)	$ (34,387)