Mergers, Acquisitions, Exchanges and Divestitures - Additional Information (Detail) $ / shares in Units, $ in Thousands		12 Months Ended
	Mar. 19, 2018 USD ($) a well	Dec. 31, 2018 USD ($) MMBoe $ / shares shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($)
Business Acquisition, Pro Forma Revenue		$ 468,949	$ 291,991
Asset retirement obligations			8,700
Non-cash impairment of oil and gas properties		0
Accumulated Depreciation Depletion Amortization And Impairment Property Plant And Equipment		654,657	444,863
Gain (Loss) on Disposition of Oil and Gas Property		(1,046)	92	$ (1,078)
Merger transaction expense		7,991	8,749	0
Business Acquisition, Pro Forma Net Income (Loss)		$ 125,281	$ (143,530)
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax, Per Share, Basic | $ / shares		$ 0.60	$ (0.81)
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax, Per Share, Diluted | $ / shares		$ 0.60	$ (0.81)
Uinta Basin [Member]
Proceeds from Divestiture of Businesses			$ 101,300	27,800
Disposal Group, Including Discontinued Operation, Liabilities				4,800
Proved Oil And Gas Properties Sold, Net Of DD&A And Impairment				30,600
Unproved Oil And Gas Properties Sold				2,000
Non-cash impairment of oil and gas properties			37,900
Unproved Oil and Gas Assets Sold			397
Proved properties			409,957
Furniture, equipment and other			1,593
Accumulated depreciation, depletion, amortization and impairment			(304,939)
Total assets			107,008
Asset retirement obligation			4,773
Total liabilities			4,773
Net assets			102,235
Gain (Loss) on Disposition of Proved Property		$ (1,000)
Proved Oil And Gas Properties [Member]
Acquisition Costs, Period Cost			9,100
Non-cash impairment of oil and gas properties		0	37,945	0
Unproved Oil And Gas Properties [Member]
Acquisition Costs, Period Cost			11,200
Non-cash impairment of oil and gas properties		0	11,153	$ 183
Level 3 [Member]
Acquisition Costs, Period Cost			11,600
Fifth Creek [Member]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual		59,400
Business Combination, Pro Forma Information, Expenses of Acquiree since Acquisition Date, Actual		$ 44,200
Fair value of common stock issued	$ 484,000
Plus: Repayment of Fifth Creek debt	53,900
Total purchase price	537,900
Accounts payable and accrued liabilities	25,782
Current unfavorable contract	2,651
Other current liabilities	13,797
Asset retirement obligations	7,361
Long-term deferred tax liability	137,707
Long-term unfavorable contract	4,449
Other noncurrent liabilities	2,354
Total purchase price plus liabilities assumed	732,001
Cash	543
Accounts receivable	7,831
Proved oil and gas properties	105,702
Unproved oil and gas properties	609,568
Asset retirement obligations	7,361
Furniture, equipment and other	931
Other noncurrent assets	65
Total asset value	$ 732,001
Net Acreage Acquired | a	81,000
Productive Oil Wells, Standard Length, Number of Wells Acquired | well	62
Productive Oil Wells, Extended Reach, Number of Wells Acquired | well	10
Proved Developed and Undeveloped Reserve, Net (Energy) | MMBoe		9.3
Proved Developed Reserves (Energy) | MMBoe		4.7
Proved Undeveloped Reserves (Energy) | MMBoe		4.6
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares		100,000,000
Acquisition-related Costs [Member] | Fifth Creek [Member]
Merger transaction expense		$ 4,000	$ 2,200