Acquisitions and Divestitures - Additional Information (Detail) $ / shares in Units, $ in Thousands			1 Months Ended		3 Months Ended				9 Months Ended	12 Months Ended
	Jul. 31, 2018 USD ($)	Mar. 01, 2018 USD ($)	Jul. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)		Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares		Feb. 28, 2018 USD ($)	Nov. 01, 2017 USD ($)	Sep. 29, 2017 USD ($) a	Dec. 31, 2016 USD ($)	Sep. 12, 2016 USD ($)
Significant Acquisitions and Disposals
Capitalized Costs, Proved Properties						$ 2,400				$ 3,700	$ 2,400
Escrow Amount Transferred															$ 7,100
Second Lien Facility						200,000				200,000	200,000
Escrow Deposit Remaining						3,210	[1]			0	3,210	[1]
Property, Plant and Equipment, Gross						590,375				1,121,860	590,375
Asset Retirement Obligation						3,286				4,314	3,286					$ 2,459	$ 2,700
Cash Received for Suspended Revenues Attributable to Acquired Properties		$ 355
Mid-Continent Divestiture [Member]
Significant Acquisitions and Disposals
Proceeds from Sale of Oil and Gas Property and Equipment	$ 6,200									6,000
Cash Paid to Buyer in Connection with Final Settlement										500
Cash Paid for Suspended Revenues in Connection with FInal Settlement										200
Asset Retirement Obligation										300
Working Capital Adjustments, Net	1,300		$ 1,300
Pre-Tax Operating Income Attributable to Assets Sold					$ (1,600)			$ (2,200)
Undeveloped Acreage [Member]
Significant Acquisitions and Disposals
Proceeds from Sale of Oil and Gas Property and Equipment										1,700
Hunt Acquisition [Domain]
Significant Acquisitions and Disposals
Other Payments to Acquire Businesses										86,000
Hunt Acquisition [Member]
Significant Acquisitions and Disposals
Capitalized Costs, Proved Properties		82,443
Cash Paid on Date of Acquisition		84,400
Accumulated Costs, net of suspended revenues, for wells in which Hunt elected not to participate		13,778
Business Acquisition, Transaction Costs		96,978		$ 400		100				500	100
Capitalized Costs, Proved Properties		16,339
Asset Retirement Obligation		356
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		96,978
Working Capital Adjustments, Net	$ (245)		(245)
Cash Received for Suspended Revenues Attributable to Acquired Properties			$ 1,448
Net Cash Paid on Date of Acquisition		82,955
Devon Acquisition [Member]
Significant Acquisitions and Disposals
Business Acquisition, Revenue Reported by Acquired Entity since Acquisition Date				0		9,000
Business Acquisition, Pro Forma Revenue										446,077	209,015
Capitalized Costs, Proved Properties		42,866
Acreage, Net | a															19,600
Other Payments to Acquire Businesses										205,000
Escrow Deposit															$ 10,300
Cash Paid on Date of Acquisition		190,277													$ 189,900
Additional working interests														$ 700
Amount Transferred from Escrow Account		9,519											$ 2,500
Business Acquisition, Transaction Costs										1,300
Escrow Deposit Remaining						3,200					3,200
Capitalized Costs, Proved Properties		146,686
Property, Plant and Equipment, Gross		8,642
Asset Retirement Obligation		494
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		197,345
Working Capital Adjustments, Net		(2,451)
Preliminary Purchase Price		$ 197,345
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax										$ 227,930	$ 30,861
Business Acquisition, Pro Forma Earnings Per Share, Basic | $ / shares										$ 15.14	$ 0
Business Acquisition, Pro Forma Earnings Per Share, Diluted | $ / shares										$ 14.91	$ 0
Escrow Distributed													$ 700
Cash Received for Suspended Revenues Attributable to Acquired Properties									$ 400
Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual				$ 0		$ 4,000

[1] 1 The December 31, 2017 amount represents amounts that had remained in the Escrow Account for the Devon Acquisition which fully funded the remaining liability due to Devon for the final settlement (see Note 5).