Derivative Financial Instruments Gains and Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative Instruments, (Gain) Loss [Line Items]
Derivative settlement (gain) loss	$ (4,090)	$ 36,665	$ 879	$ 61,193
Net derivative (gain) loss	(79,655)	63,749	97,426	71,278
Oil Contracts [Member]
Derivative Instruments, (Gain) Loss [Line Items]
Derivative settlement (gain) loss	10,689	24,430	12,058	45,178
Net derivative (gain) loss	(34,552)	22,402	151,245	36,368
Gas Contracts [Member]
Derivative Instruments, (Gain) Loss [Line Items]
Derivative settlement (gain) loss	(5,668)	757	(1,534)	(5,653)
Net derivative (gain) loss	(25,996)	7,000	(32,109)	16,990
NGL Contracts [Member]
Derivative Instruments, (Gain) Loss [Line Items]
Derivative settlement (gain) loss	(9,111)	11,478	(9,645)	21,668
Net derivative (gain) loss	$ (19,107)	$ 34,347	$ (21,710)	$ 17,920