Consolidated statements of cash flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income (loss)	$ 324,595	$ 548,974	$ (260,739)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Deferred income tax expense	5,056	0	0
Depletion, depreciation and amortization	212,677	158,389	148,339
Impairment expense	0	0	162,027
Gain on sale of investment in equity method investee (see Note 4.c)	0	(405,906)	0
Loss on early redemption of debt	0	23,761	0
Non-cash stock-based compensation, net	36,396	35,734	29,229
Mark-to-market on derivatives:
(Gain) loss on derivatives, net	(42,984)	(350)	87,425
Settlements received for matured derivatives, net	6,090	37,583	195,281
Settlements received for early terminations of derivatives, net	0	4,234	80,000
Change in net present value of derivative deferred premiums	694	394	232
Premiums paid for derivatives	(20,335)	(25,853)	(89,669)
Amortization of debt issuance costs	3,331	4,086	4,279
Write-off of debt issuance costs	0	0	842
Income from equity method investee (see Note 4.c)	0	(8,485)	(9,403)
Cash settlement of performance unit awards	0	0	(6,394)
Other, net	11,857	6,067	4,596
Decrease (increase) in accounts receivable	4,669	(12,124)	832
Increase in other current assets	(1,865)	(3,461)	(1,373)
Decrease (increase) in other noncurrent assets	124	(4,774)	360
Increase in accounts payable and accrued liabilities	11,163	9,137	5,432
Increase (decrease) in undistributed revenues and royalties	10,989	11,014	(7,735)
(Decrease) increase in other current liabilities	(23,799)	(2,327)	13,153
(Decrease) increase in other noncurrent liabilities	(854)	8,821	(419)
Net cash provided by operating activities	537,804	384,914	356,295
Cash flows from investing activities:
Deposit received for potential sale of oil and natural gas properties	0	0	3,000
Deposit utilized for sale of oil and natural gas properties	0	(3,000)	0
Acquisitions of oil and natural gas properties	(17,538)	0	(124,660)
Capital expenditures:
Oil and natural gas properties	(673,584)	(538,122)	(360,679)
Midstream service assets	(6,784)	(20,887)	(5,240)
Other fixed assets	(7,308)	(4,905)	(7,611)
Investment in equity method investee (see Note 4.c)	0	(31,808)	(69,609)
Proceeds from disposition of equity method investee, net of selling costs (see Note 4.c)	1,655	829,615	0
Proceeds from dispositions of capital assets, net of selling costs	12,603	64,157	397
Net cash (used in) provided by investing activities	(690,956)	295,050	(564,402)
Cash flows from financing activities:
Borrowings on Senior Secured Credit Facility	210,000	190,000	239,682
Payments on Senior Secured Credit Facility	(20,000)	(260,000)	(304,682)
Early redemption of debt	0	(518,480)	0
Proceeds from issuance of common stock, net of offering costs	0	0	276,052
Share repurchases	(97,055)	0	0
Vested stock exchanged for tax withholding	(4,418)	(7,662)	(1,635)
Proceeds from exercise of stock options	86	397	208
Payments for debt issuance costs	(2,469)	(4,732)	0
Net cash provided by (used in) financing activities	86,144	(600,477)	209,625
Net (decrease) increase in cash and cash equivalents	(67,008)	79,487	1,518
Cash and cash equivalents, beginning of period	112,159	32,672	31,154
Cash and cash equivalents, end of period	$ 45,151	$ 112,159	$ 32,672