Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
OPERATING ACTIVITIES:
Net income	$ 37,138	$ 28,693
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion, and amortization	178,976	151,545
Amortization of debt issuance costs and debt discount (Note 6)	1,645	1,616
(Gain) loss on derivatives (Note 10)	25,608	(21,019)
Cash payments on derivatives settled, net (Note 10)	(18,040)	(729)
Deferred tax expense	12,380	22,084
Gain on disposition of assets	(575)	(1,153)
Stock compensation plans	17,397	12,478
Contract assets and liabilities, net (Note 2)	(3,671)	0
Other, net	2,835	1,397
Changes in operating assets and liabilities increasing (decreasing) cash:
Accounts receivable	(15,558)	(36,381)
Accounts payable	(14,867)	4,873
Material and supplies	0	17
Income taxes	0	(15)
Accrued liabilities	16,242	20,280
Other, net	(2,975)	1,106
Net cash provided by operating activities	236,535	184,792
INVESTING ACTIVITIES:
Capital expenditures	(304,054)	(167,392)
Producing properties and other acquisitions	(769)	(55,429)
Proceeds from disposition of assets	25,316	20,137
Other	0	(1,500)
Net cash used in investing activities	(279,507)	(204,184)
FINANCING ACTIVITIES:
Borrowings under credit agreement	71,200	251,401
Payments under credit agreement	(249,200)	(250,100)
Payments on capitalized leases	(2,869)	(2,967)
Proceeds from common stock issued, net of issue costs (Note 14)	0	18,623
Proceeds from investments of non-controlling interests	300,000	0
Transaction costs associated with non-controlling interests	(2,303)	0
Book overdrafts	17,000	2,364
Net cash provided by financing activities	133,828	19,321
Net increase (decrease) in cash and cash equivalents	90,856	(71)
Cash and cash equivalents, beginning of period	701	893
Cash and cash equivalents, end of period	91,557	822
Cash paid during the year for:
Interest paid (net of capitalized)	14,418	14,601
Income taxes	3,600	0
Changes in accounts payable and accrued liabilities related to purchases of property, plant, and equipment	(28,770)	(20,122)
Non-cash (addition) reduction to oil and natural gas properties related to asset retirement obligations	$ 8,546	$ (3,203)