Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (loss)	$ 26,847,000	$ (45,534,000)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities
Depreciation, depletion and amortization	26,189,000	15,113,000
Exploration expense	4,988,000	9,361,000
Stock-based compensation	2,081,000	1,473,000
Impairment of proved oil and gas properties		17,665,000
Accretion of asset retirement obligations	124,000	86,000
(Gain) loss on sale of assets	(5,000)	(22,000)
(Gain) loss on derivative instruments	(25,097,000)	(10,550,000)
Net cash receipts (payments) on settled derivatives	(3,989,000)	18,378,000
(Gain) loss on early extinguishment of debt		(8,664,000)
Deferred income taxes	0	540,000
Amortization of deferred financing costs	502,000	504,000
Amortization of debt discount	330,000	352,000
Changes in operating assets and liabilities:
Accounts receivable	10,478,000	10,447,000
Other assets	943,000	(1,201,000)
Accounts payable and accrued liabilities	(14,992,000)	(27,457,000)
Net cash provided by (used in) operating activities	28,399,000	(19,509,000)
CASH FLOWS FROM INVESTING ACTIVITIES
Capital expenditures for oil and gas properties	(66,005,000)	(23,912,000)
Capital expenditures for other property and equipment	(178,000)	(460,000)
Proceeds from sale of assets	24,000	4,800,000
Net cash used in investing activities	(66,159,000)	(19,572,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Debt issuance costs	(1,231,000)	(200,000)
Repayments of long-term debt	(74,000)	(9,252,000)
Employee tax withholding for settlement of equity compensation awards	(1,706,000)	(51,000)
Net cash used in financing activities	(3,011,000)	(9,503,000)
Net decrease in cash and cash equivalents	(40,771,000)	(48,584,000)
Cash and cash equivalents at beginning of period	201,229,000	184,405,000
Cash and cash equivalents at end of period	160,458,000	135,821,000
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash paid for interest	23,066,000	24,766,000
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES
Asset retirement obligations incurred, including changes in estimate	124,000
Additions to oil and natural gas properties - changes in accounts payable, accrued liabilities, and accrued capital expenditures	$ 13,126,000	(6,229,000)
Assets held for sale		$ (6,000)