Costs Incurred for Property Acquisition, Exploration and Development (Detail) - USD ($) $ in Thousands		6 Months Ended			12 Months Ended
		Jun. 30, 2020		Jun. 30, 2019	Dec. 31, 2019
Acquisitions:
Acreage purchases	[1]	$ 8,736			$ 57,324
Development	[1]	223,401			666,984
Gas gathering facilities:
Development	[1]	2,386			3,583
Subtotal	[1]	249,627			764,574
Asset retirement obligations		4,247	[1]	$ 2,326	11,193	[1]
Total costs incurred	[1]	253,874			775,767
Expense
Exploration:
Exploration costs incurred	[1]	14,402			35,117
Stock-based compensation expense	[1]	$ 702			$ 1,566

[1] Includes costs incurred whether capitalized or expensed.