Consolidated statements of operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenues:
Total revenues	$ 259,696	$ 189,006
Costs and expenses:
Lease operating expenses	21,951	16,992
Production and ad valorem taxes	11,812	8,781
General and administrative	24,725	25,597
Depletion, depreciation and amortization	45,553	34,112
Other operating expenses	1,106	1,026
Total costs and expenses	166,504	137,680
Operating income	93,192	51,326
Non-operating income (expense):
Gain on derivatives, net	9,010	36,671
Income from equity method investee (see Note 3.a)	0	3,068
Interest expense	(13,518)	(22,720)
Interest and other income	453	145
Loss on disposal of assets, net	(2,617)	(214)
Non-operating income (expense), net	(6,672)	16,950
Income before income taxes	86,520	68,276
Income tax:
Deferred	0	0
Total income tax	0	0
Net income	$ 86,520	$ 68,276
Net income per common share:
Basic (in dollars per share)	$ 0.36	$ 0.29
Diluted (in dollars per share)	$ 0.36	$ 0.28
Weighted-average common shares outstanding:
Basic (in shares)	238,228	238,505
Diluted (in shares)	239,319	244,379
Oil sales
Revenues:
Total revenues	$ 150,914	$ 99,467
NGL sales
Revenues:
Total revenues	28,360	20,828
Natural gas sales
Revenues:
Total revenues	18,160	18,441
Midstream service revenues
Revenues:
Total revenues	2,359	2,999
Costs and expenses:
Cost of Goods and Services Sold	693	916
Sales of purchased oil
Revenues:
Total revenues	59,903	47,271
Costs and expenses:
Cost of Goods and Services Sold	$ 60,664	$ 50,256