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)	$ 95,213	$ (44,733)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Impairment of proved and unproved oil and gas properties	4,581	72,191
Depreciation, depletion and amortization	47,568	36,915
Accretion of asset retirement obligations	169	434
Gain on sale of oil and gas properties, net	(1,919)	(9,105)
Settlement of asset retirement obligations	(79)	(9)
Total (gain) loss on derivative contracts, net	(60,947)	7,986
Operating portion of net cash paid in settlement of derivative contracts	(15,090)	(708)
Stock-based compensation	7,071	6,601
Deferred income taxes	2,470	(16,388)
Write-off of deferred financing costs	0	526
Amortization of deferred financing costs	325	257
Changes in assets and liabilities:
(Increase) decrease in accounts receivable	(8,195)	444
(Increase) decrease in prepaid expenses and other current assets	(376)	(335)
Increase (decrease) in accounts payable and accrued expenses	1,132	(282)
Increase (decrease) in revenues and royalties payable	31,869	(2,888)
Increase (decrease) in advances	(1,413)	45
Net cash provided by operating activities	102,379	50,951
Cash flows from investing activities:
Acquisition of oil and gas properties	(32,551)	(55,609)
Additions to oil and gas properties	(149,999)	(65,262)
Additions to office and other equipment	(170)	(167)
Proceeds from sale of oil and gas properties	5,965	34,735
Net cash used in investing activities	(176,755)	(86,303)
Cash flows from financing activities:
Proceeds from borrowings	156,830	85,000
Repayments of borrowings	(103,002)	(74,298)
Cash paid related to the exchange and cancelation of Common Stock	(1,524)	(675)
Deferred financing costs	(507)	(1,358)
Issuance of Class A Common Stock, net of offering costs of $2.2 million	0	39,438
Net cash provided by financing activities	51,797	48,107
Net increase (decrease) in cash and cash equivalents	(22,579)	12,755
Cash at beginning of period	22,955	10,200
Cash at end of period	376	22,955
Cash paid for:
Interest	2,290	2,495
Non-cash investing and financing activities:
Accrued capital expenditures	22,801	19,883
Asset retirement obligations	252	(42)
Bold Contribution Agreement | Class B Common Stock
Non-cash investing and financing activities:
Common stock issued	0	489,842
Bold Contribution Agreement | Class A Common Stock
Non-cash investing and financing activities:
Common stock issued	$ 0	$ 2,037