Revenue from Contracts with Customers Disaggregation of oil, gas, and NGL production revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 1,636,357	[1]	$ 1,253,783	[2]	$ 1,178,426	[3]
Concentration Risk, Percentage	100.00%	[1]	100.00%	[2]	100.00%	[3]
Revenue, Remaining Performance Obligation, Amount	$ 0
Permian Region [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,064,607	[1]	$ 482,060	[2]	$ 134,806	[3]
South Texas & Gulf Coast [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	514,514	[1]	610,485	[2]	723,963	[3]
Rocky Mountain Region [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 57,236	[1]	$ 161,238	[2]	$ 319,657	[3]
Sales Revenue, Net [Member] | Geographic Concentration Risk [Member] | Permian Region [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	65.00%	[1]	38.00%	[2]	11.00%	[3]
Sales Revenue, Net [Member] | Geographic Concentration Risk [Member] | South Texas & Gulf Coast [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	32.00%	[1]	49.00%	[2]	62.00%	[3]
Sales Revenue, Net [Member] | Geographic Concentration Risk [Member] | Rocky Mountain Region [Member]
Segment Reporting Information [Line Items]
Concentration Risk, Percentage	3.00%	[1]	13.00%	[2]	27.00%	[3]
Oil production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 1,065,676	[1]	$ 654,250	[2]	$ 611,838	[3]
Oil production revenue [Member] | Permian Region [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	938,004		419,732		117,399
Oil production revenue [Member] | South Texas & Gulf Coast [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	72,821		82,674		189,313
Oil production revenue [Member] | Rocky Mountain Region [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	54,851		151,844		305,126
Gas production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	354,450	[1]	369,410	[2]	337,288	[3]
Gas production revenue [Member] | Permian Region [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	125,603		61,781		17,315
Gas production revenue [Member] | South Texas & Gulf Coast [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	227,252		301,780		308,829
Gas production revenue [Member] | Rocky Mountain Region [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,595		5,849		11,144
NGL production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	216,231	[1]	230,123	[2]	229,300	[3]
NGL production revenue [Member] | Permian Region [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,000		547		92
NGL production revenue [Member] | South Texas & Gulf Coast [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	214,441		226,031		225,821
NGL production revenue [Member] | Rocky Mountain Region [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 790		$ 3,545		$ 3,387

[1] Note: Amounts may not calculate due to rounding.

[2] Note: Amounts may not calculate due to rounding.

[3] Note: Amounts may not calculate due to rounding.