Derivative Financial Instruments Gains and Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative Instruments, (Gain) Loss [Line Items]
Derivative settlement (gain) loss	$ 4,969	$ 24,528
Net derivative (gain) loss	177,081	7,529
Oil Contracts [Member]
Derivative Instruments, (Gain) Loss [Line Items]
Derivative settlement (gain) loss	1,369	20,748
Net derivative (gain) loss	185,797	13,966
Gas Contracts [Member]
Derivative Instruments, (Gain) Loss [Line Items]
Derivative settlement (gain) loss	4,134	(6,410)
Net derivative (gain) loss	(6,113)	9,990
NGL Contracts [Member]
Derivative Instruments, (Gain) Loss [Line Items]
Derivative settlement (gain) loss	(534)	10,190
Net derivative (gain) loss	$ (2,603)	$ (16,427)