Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net income	$ 39,578	$ 21,530
Adjustments to reconcile net income to cash flows from operating activities
Depletion, depreciation, and amortization	52,451	51,195
Deferred income taxes	15,052	34,909
Stock-based compensation	2,592	4,106
Commodity derivatives expense (income)	48,825	(24,602)
Payment on settlements of commodity derivatives	(33,357)	(26,940)
Debt issuance costs and discounts	1,137	1,901
Other, net	(838)	(344)
Changes in assets and liabilities, net of effects from acquisitions
Accrued production receivable	(11,510)	6,453
Trade and other receivables	348	(12,185)
Other current and long-term assets	(1,886)	643
Accounts payable and accrued liabilities	(19,817)	(23,890)
Oil and natural gas production payable	(673)	(7,335)
Other liabilities	(275)	(1,179)
Net cash provided by operating activities	91,627	24,262
Cash flows from investing activities
Oil and natural gas capital expenditures	(56,669)	(52,152)
Acquisitions of oil and natural gas properties	(35)	(16,222)
Pipelines and plants capital expenditures	(156)	(246)
Net proceeds from sales of oil and natural gas properties and equipment	1,522	415
Other	4,542	792
Net cash used in investing activities	(50,796)	(67,413)
Cash flows from financing activities
Bank repayments	(571,653)	(343,000)
Bank borrowings	546,653	397,000
Pipeline financing and capital lease debt repayments	(6,287)	(7,055)
Other	(9,291)	(3,469)
Net cash provided by (used in) financing activities	(40,578)	43,476
Net increase in cash, cash equivalents, and restricted cash	253	325
Cash, cash equivalents, and restricted cash at beginning of period	40,614	40,905
Cash, cash equivalents, and restricted cash at end of period	$ 40,867	$ 41,230