Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
OPERATING ACTIVITIES:
Net income	$ 16,015	$ 24,988
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion, and amortization	115,439	97,012
Amortization of debt issuance costs and debt discount (Note 6)	1,095	1,075
(Gain) loss on derivatives (Note 10)	21,223	(23,633)
Cash payments on derivatives settled, net (Note 10)	(8,928)	(1,569)
Deferred tax expense	5,636	20,315
Gain on disposition of assets	(322)	(1,072)
Stock compensation plans	12,073	8,066
Contract assets and liabilities, net (Note 2)	(2,371)	0
Other, net	1,998	299
Changes in operating assets and liabilities increasing (decreasing) cash:
Accounts receivable	(6,812)	(15,087)
Accounts payable	(403)	3,724
Material and supplies	4	49
Income taxes	0	(15)
Accrued liabilities	1,572	756
Other, net	(1,526)	2,147
Net cash provided by operating activities	154,693	117,055
INVESTING ACTIVITIES:
Capital expenditures	(189,916)	(107,933)
Producing properties and other acquisitions	(962)	(52,956)
Proceeds from disposition of assets	23,528	19,556
Other	0	(1,500)
Net cash used in investing activities	(167,350)	(142,833)
FINANCING ACTIVITIES:
Borrowings under credit agreement	71,200	160,600
Payments under credit agreement	(249,200)	(156,500)
Payments on capitalized leases	(1,901)	(1,901)
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	(2,254)	0
Book overdrafts	(1,581)	4,912
Net cash provided in financing activities	116,264	25,734
Net increase (decrease) in cash and cash equivalents	103,607	(44)
Cash and cash equivalents, beginning of period	701	893
Cash and cash equivalents, end of period	104,308	849
Cash paid during the year for:
Interest paid (net of capitalized)	(17,957)	(16,813)
Income taxes	0	0
Changes in accounts payable and accrued liabilities related to purchases of property, plant, and equipment	(3,747)	(8,771)
Non-cash (addition) reduction to oil and natural gas properties related to asset retirement obligations	$ 7,854	$ 1,579