Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net income (loss)	$ 19,348	$ (43,485)
Adjustments to reconcile net income (loss) to net cash provided by operating activities
Depreciation, depletion and amortization	83,582	56,957
Stock-based compensation	1,707	1,629
Stock-based payments	(601)	0
Deferred taxes	7,601	(29,191)
(Gain) loss on derivative financial instruments	(22,744)	14,080
Settlements of derivative financial instruments	(22,623)	5,207
Impairment of oil and natural gas properties	12,169	33,413
Loss on abandonment of property and equipment	170	0
Non-cash interest expense	5,194	4,571
Unrealized gain on warrants	(416)	(3,088)
Changes in operating assets and liabilities
Accounts receivable	(5,391)	(6,851)
Prepaid expenses and other assets	(3,296)	833
Accounts payable and accrued expenses	13,372	9,371
Net cash provided by operating activities	88,072	43,446
Cash flows from investing activities
Acquisition of oil and gas properties	(45,539)	(113,726)
Development of oil and gas properties	(171,413)	(81,875)
Purchases of other property and equipment	(2,518)	(13,142)
Net cash used in investing activities	(219,470)	(208,743)
Cash flows from financing activities
Proceeds from borrowings	423,745	123,968
Payments on borrowings	(289,520)	(34,017)
Proceeds from sale of preferred stock	0	77,800
Repurchase and retirement of Class B Common Stock	(10)	0
Cost to issue equity	0	(3,296)
Payments of debt issuance costs and other	0	(2,688)
Net cash provided by financing activities	134,215	161,767
Increase (decrease) in cash and cash equivalents	2,817	(3,530)
Cash and cash equivalents, beginning of the period	2,538	6,068
Cash and cash equivalents, end of the period	5,355	2,538
Supplemental information:
Cash paid for taxes	1,242	2,474
Cash paid for interest	24,395	20,389
Non-cash investing and financing activities:
Asset retirement obligation	1,331	2,827
(Decrease) increase in liabilities for capital expenditures	(4,603)	8,379
Preferred stock issued for business acquisitions	$ 0	$ 10,795