Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (loss)	$ 38,341,000	$ (118,697,000)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities
Depreciation, depletion and amortization	51,341,000	36,062,000
Exploration expense	9,192,000	18,722,000
Stock-based compensation	4,429,000	3,701,000
Impairment of proved oil and gas properties		17,665,000
Accretion of asset retirement obligations	252,000	175,000
(Gain) loss on derivative instruments	(43,274,000)	19,046,000
Net cash receipts (payments) on settled derivatives	(6,633,000)	31,258,000
(Gain) loss on sale of assets	1,000	(1,046,000)
(Gain) loss on early extinguishment of debt		(14,489,000)
Deferred income taxes	0	540,000
Amortization of deferred financing costs	1,035,000	972,000
Amortization of debt discount	661,000	691,000
Changes in operating assets and liabilities:
Accounts receivable	3,992,000	(1,595,000)
Other assets	308,000	(2,586,000)
Accounts payable and accrued liabilities	5,796,000	(7,670,000)
Net cash provided by (used in) operating activities	65,441,000	(17,251,000)
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures for oil and gas properties	(166,012,000)	(42,913,000)
Capital expenditures for other property and equipment	(537,000)	(416,000)
Proceeds from sale of assets	544,000	14,094,000
Net cash used in investing activities	(166,005,000)	(29,235,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Debt issuance costs	(1,296,000)	261,000
Repayments of long-term debt	(222,000)	(23,786,000)
Equity issuance costs	(40,000)	(277,000)
Employee tax withholding for settlement of equity compensation awards	(2,032,000)	(61,000)
Net cash used in financing activities	(3,590,000)	(23,863,000)
Net decrease in cash and cash equivalents	(104,154,000)	(70,349,000)
Cash and cash equivalents at beginning of period	201,229,000	184,405,000
Cash and cash equivalents at end of period	97,075,000	114,056,000
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash paid for interest	23,502,000	25,175,000
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES
Asset retirement obligations incurred, including changes in estimate	540,000	63,000
Additions to oil and natural gas properties - changes in accounts payable, accrued liabilities, and accrued capital expenditures	$ 11,674,000	$ 123,000