Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Summary of Property and Equipment Including Oil and Natural Gas Properties

A summary of property and equipment including oil and natural gas properties is as follows (in thousands):

	December 31, 2018			December 31, 2017
Oil and natural gas properties:
Unproved	$	482,475		$	459,549
Proved		2,188,233			1,896,081
Gross oil and natural gas properties		2,670,708			2,355,630
Less accumulated depreciation, depletion and    amortization		(1,380,650	)		(1,248,200	)
Oil and natural gas properties, net		1,290,058			1,107,430
Other property and equipment		14,460			13,508
Less accumulated depreciation		(8,160	)		(6,566	)
Other property and equipment, net		6,300			6,942
Property and equipment, net	$	1,296,358		$	1,114,372

Schedule of Accounts Payable

A summary of accounts payable is as follows (in thousands):

	December 31, 2018		December 31, 2017
Trade payables	$	27,481	$	44,516
Royalty payables		70,019		17,483
Production & ad valorem taxes		1,811		967
Derivative payable		4,736		941
Other payables		12,688		12,267
Total accounts payable	$	116,735	$	76,174

Summary of Accrued Liabilities

A summary of accrued liabilities is as follows (in thousands):

	December 31, 2018		December 31, 2017
Ad valorem and production taxes	$	6,193	$	4,299
Employee compensation		6,595		8,667
Royalties		39,969		9,660
Short term derivatives		—		14,875
Other		4,152		4,161
Total accrued liabilities	$	56,909	$	41,662

Summary of Revenue Disaggregated by Type

The following table illustrates the revenue disaggregated by type for the periods indicated:

	For the Year Ended December 31,
	2018		2017		2016
Revenues (in thousands)
Natural gas sales	$	274,239	$	241,379	$	134,618
NGL sales		86,152		64,109		38,204
Oil sales		138,202		74,690		50,193
Brokered natural gas and marketing revenue		16,552		3,481		12,019
Total revenues	$	515,145	$	383,659	$	235,034

Changes in Company's Asset Retirement Obligation Liability

The following table sets forth the changes in the Company’s ARO liability for the periods indicated (in thousands):

	For the Year Ended December 31,
	2018		2017		2016
Asset retirement obligations, beginning of period	$	6,029	$	4,806	$	3,401
Additional liabilities incurred		418		679		1,014
Accretion		663		544		391
Asset retirement obligations, end of period	$	7,110	$	6,029	$	4,806

Summary of Reconciliation of Amounts in Previously Reported Consolidated Financial Statements

A reconciliation of the effects of the revision to amounts in the previously reported consolidated financial statements is as follows (in thousands, except per share amounts):

	As of  December 31, 2016
	As Reported			Adjustment			As Adjusted
Balance Sheet
Accounts receivable	$	43,638		$	785		$	44,423
Total current assets		249,630			785			250,415
Total assets		1,197,859			785			1,198,644
Accrued liabilities		64,150			(9,106	)		55,044
Total current liabilities		140,625			(9,106	)		131,519
Total liabilities		651,143			(9,106	)		642,037
Accumulated deficit		(1,414,561	)		9,891			(1,404,670	)
Total stockholders' equity		546,716			9,891			556,607
Total liabilities and stockholders' equity		1,197,859			785			1,198,644

	As of  December 31, 2016
	As Reported			Adjustment		As Adjusted
Statement of Stockholders' Equity
Accumulated deficit	$	(1,414,561	)	$	9,891	$	(1,404,670	)
Total stockholders' equity		546,716			9,891		556,607

	As of  December 31, 2016
	As Reported			Adjustment			As Adjusted
Statement of Operations
Production and ad valorem taxes	$	4,998		$	2,929		$	7,927
Total operating expenses		349,507			2,929			352,436
Operating loss		(114,473	)		(2,929	)		(117,402	)
Loss before income taxes		(203,260	)		(2,929	)		(206,189	)
Net loss		(203,806	)		(2,929	)		(206,735	)
Basic and diluted loss per share	$	(12.60	)	$	(0.24	)	$	(12.84	)

	As of  December 31, 2016
	As Reported			Adjustment			As Adjusted
Statement of Comprehensive Loss
Net loss	$	(203,806	)	$	(2,929	)	$	(206,735	)
Total Comprehensive loss		(203,806	)		(2,929	)		(206,735	)

	As of December 31, 2016
	As Reported			Adjustment			As Adjusted
Statement of Cash Flows
Net loss	$	(203,806	)	$	(2,929	)	$	(206,735	)
Accounts receivable		(20,563	)		(714	)		(21,277	)
Accounts payable and accrued liabilities		(2,849	)		3,643			794

Sales Revenue, Services, Net [Member] | Customer Concentration Risk [Member]

Concentration Risk

The following table sets forth the Company’s major customers and associated percentage of revenue for the periods indicated:

	For the Year Ended December 31,
	2018		2017		2016
Purchaser
Antero Resources		—		—	14%
Concord Energy		—		—	12%
Emera Energy Services		—	17%			—
EnLink Midstream		—		—	17%
Marathon Petroleum	25%		10%			—
Sequent Energy Management		—		—	20%
Total	25%		27%		63%

Accounts Receivable [Member] | Product Concentration Risk [Member]

Concentration Risk

The following table summarizes concentration of receivables, net of allowances, by product or service as of December 31, 2018 and December 31, 2017 (in thousands):

	December 31, 2018		December 31, 2017
Receivables by product or service:
Sale of oil and natural gas and related products    and services	$	94,107	$	52,908
Joint interest owners		24,830		23,154
Derivatives		372		1,528
Other		23		19
Total	$	119,332	$	77,609