For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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- Definition

Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Disaggregation of oil, gas, and NGL production revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 389,419	$ 458,382	$ 1,136,749	$ 1,243,826
Revenue, Remaining Performance Obligation, Amount	0		0
Oil production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	292,857	287,522	836,062	814,732
Gas production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	64,047	96,810	194,384	259,983
NGL production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	32,515	74,050	106,303	169,111
Midland Basin [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	295,265	311,013	840,978	801,306
Midland Basin [Member] \| Oil production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	277,361	270,086	791,055	703,516
Midland Basin [Member] \| Gas production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	17,780	40,364	49,821	96,974
Midland Basin [Member] \| NGL production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	124	563	102	816
South Texas [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	94,154	147,369	295,771	385,284
South Texas [Member] \| Oil production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	15,496	17,436	45,007	56,365
South Texas [Member] \| Gas production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	46,267	56,446	144,563	161,414
South Texas [Member] \| NGL production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 32,391	$ 73,487	106,201	167,505
Rocky Mountain [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax			0	57,236
Rocky Mountain [Member] \| Oil production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax			0	54,851
Rocky Mountain [Member] \| Gas production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax			0	1,595
Rocky Mountain [Member] \| NGL production revenue [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Including Assessed Tax			$ 0	$ 790
Revenue Benchmark [Member] \| Geographic Concentration Risk [Member]
Segment Reporting Information [Line Items]
Relative percentage	100.00%	100.00%	100.00%	100.00%
Revenue Benchmark [Member] \| Geographic Concentration Risk [Member] \| Midland Basin [Member]
Segment Reporting Information [Line Items]
Relative percentage	76.00%	68.00%	74.00%	64.00%
Revenue Benchmark [Member] \| Geographic Concentration Risk [Member] \| South Texas [Member]
Segment Reporting Information [Line Items]
Relative percentage	24.00%	32.00%	26.00%	31.00%
Revenue Benchmark [Member] \| Geographic Concentration Risk [Member] \| Rocky Mountain [Member]
Segment Reporting Information [Line Items]
Relative percentage			0.00%	5.00%