Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
OPERATING ACTIVITIES:
Net income (loss)	$ 117,848	$ (135,624)	$ (1,037,361)
Adjustments to reconcile net income (loss) to net cash provided (used) by operating activities:
Depreciation, depletion, and amortization	209,257	208,353	352,742
Impairments (Note 2)	0	161,563	1,634,628
Amortization of debt issuance costs and debt discount	2,159	2,122	2,088
(Gain) loss on derivatives	(14,732)	22,813	(26,345)
Cash receipts on derivatives settled	173	9,658	46,615
(Gain) loss on disposition of assets	(327)	(3,127)	7,229
Deferred tax benefit	(57,683)	(71,209)	(606,332)
Employee stock compensation plans	17,747	13,812	21,468
Bad debt expense	348	785	1,191
ARO liability accretion	2,886	2,779	3,453
Other, net	(865)	(6,037)	(1,517)
Changes in operating assets and liabilities increasing (decreasing) cash:
Accounts receivable	(32,073)	(11,796)	105,426
Materials and supplies	2,835	225	1,507
Prepaid expenses and other	1,527	2,585	7,134
Accounts payable	21,824	27,400	(20,306)
Accrued liabilities	6,996	(4,388)	(22,920)
Income taxes	38	20,903	(21,482)
Contract advances	1,630	(687)	(274)
Net cash provided by operating activities	279,588	240,130	446,944
INVESTING ACTIVITIES:
Capital expeditures	(269,185)	(186,149)	(561,453)
Producing property and other acquisitions	(58,026)	(564)	(179)
Proceeds from disposition of property and equipment	21,713	74,823	11,854
Other	(1,500)	919	0
Net cash used in investing activities	(306,998)	(110,971)	(549,778)
FINANCING ACTIVITIES:
Borrowings under line of credit	343,900	251,398	618,500
Payments under line of credit	(326,700)	(371,600)	(503,500)
Payments on capitalized leases	(3,694)	(3,694)	(3,549)
Proceeds from common stock issued, net of issue costs (Note 15)	18,623	0	0
Tax expense from stock compensation	0	(376)	(3,207)
Decrease in book overdrafts (Note 2)	(4,911)	(4,829)	(5,624)
Net cash provided by (used in) financing activities	27,218	(129,101)	102,620
Net increase (decrease) in cash and cash equivalents	(192)	58	(214)
Cash and cash equivalents, beginning of year	893	835	1,049
Cash and cash equivalents, end of year	701	893	835
Supplemental disclosure of cash flow information:
Interest paid (net of capitalization)	33,931	35,690	30,910
Income taxes	0	42	3,540
Changes in accounts payable and accrued liabilities related to purchases of property, plant, and equipment	(6,942)	21,190	105,157
Non-cash reductions to oil and natural gas properties related to asset retirement obligations	$ 3,613	$ 30,897	$ 5,694