CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
REVENUE
Revenue from contracts with customers	$ 134,431	$ 142,656	$ 259,420	$ 273,483
Gain (loss) on commodity derivative instruments	29,187	(33,347)	(11,996)	(49,680)
TOTAL REVENUE	163,618	109,309	247,424	223,803
OPERATING (INCOME) EXPENSE
Lease operating expense	3,849	4,290	9,141	8,538
Production costs and ad valorem taxes	14,450	14,373	29,042	29,298
Exploration expense	304	6,745	308	6,748
Depreciation, depletion, and amortization	29,725	30,292	57,558	58,862
General and administrative	14,347	19,812	35,561	38,333
Accretion of asset retirement obligations	277	273	554	542
(Gain) loss on sale of assets, net	0	0	0	(2)
TOTAL OPERATING EXPENSE	62,952	75,785	132,164	142,319
INCOME (LOSS) FROM OPERATIONS	100,666	33,524	115,260	81,484
OTHER INCOME (EXPENSE)
Interest and investment income	47	37	93	70
Interest expense	(5,652)	(5,280)	(11,177)	(9,801)
Other income (expense)	26	409	(72)	(1,106)
TOTAL OTHER EXPENSE	(5,579)	(4,834)	(11,156)	(10,837)
NET INCOME (LOSS)	95,087	28,690	104,104	70,647
Net (income) loss attributable to noncontrolling interests	0	48	0	22
Distributions on Series A redeemable preferred units	0	0	0	(25)
Distributions on Series B cumulative convertible preferred units	(5,250)	(5,250)	(10,500)	(10,500)
NET INCOME (LOSS) ATTRIBUTABLE TO THE GENERAL PARTNER AND COMMON AND SUBORDINATED UNITS	89,837	23,488	93,604	60,144
ALLOCATION OF NET INCOME (LOSS):
General partner interest	0	0	0	0
NET INCOME (LOSS) ATTRIBUTABLE TO THE GENERAL PARTNER AND COMMON AND SUBORDINATED UNITS	89,837	23,488	93,604	60,144
Common Units
ALLOCATION OF NET INCOME (LOSS):
Allocation of net income (loss)	$ 67,718	$ 17,540	$ 69,611	$ 41,877
NET INCOME (LOSS) ATTRIBUTABLE TO LIMITED PARTNERS PER COMMON AND SUBORDINATED UNIT:
Per unit (basic) (in dollars per share)	$ 0.45	$ 0.17	$ 0.54	$ 0.40
Weighted average units outstanding (basic) (in shares)	150,101	105,250	129,873	104,516
Per unit (diluted) (in dollars per share)	$ 0.44	$ 0.17	$ 0.54	$ 0.40
Weighted average units outstanding (diluted) (in shares)	165,070	105,250	129,873	104,516
Subordinated Units
ALLOCATION OF NET INCOME (LOSS):
Allocation of net income (loss)	$ 22,119	$ 5,948	$ 23,993	$ 18,267
NET INCOME (LOSS) ATTRIBUTABLE TO LIMITED PARTNERS PER COMMON AND SUBORDINATED UNIT:
Per unit (basic) (in dollars per share)	$ 0.39	$ 0.06	$ 0.32	$ 0.19
Weighted average units outstanding (basic) (in shares)	56,104	96,329	76,105	95,864
Per unit (diluted) (in dollars per share)	$ 0.39	$ 0.06	$ 0.32	$ 0.19
Weighted average units outstanding (diluted) (in shares)	56,104	96,329	76,105	95,864
Oil and condensate sales
REVENUE
Revenue from contracts with customers	$ 74,072	$ 77,225	$ 131,776	$ 150,208
Natural gas and natural gas liquids sales
REVENUE
Revenue from contracts with customers	53,642	53,854	115,282	107,099
Lease bonus and other income
REVENUE
Revenue from contracts with customers	$ 6,717	$ 11,577	$ 12,362	$ 16,176