Costs Incurred for Property Acquisition, Exploration and Development (Tables)

6 Months Ended

Jun. 30, 2018

Extractive Industries [Abstract]

Costs Incurred for Property Acquisition, Exploration and Development

	Six Months Ended June 30, 2018		Year Ended December 31, 2017
	(in thousands)
Acquisitions:
Acreage purchases	$	28,300	$	62,075
Oil and gas properties		1,683		18,269
Development		484,186		1,177,526
Exploration:
Drilling		2,235		2,030
Expense		14,096		50,920
Stock-based compensation expense		1,122		2,742
Gas gathering facilities:
Development		4,599		15,097
Subtotal		536,221		1,328,659
Asset retirement obligations		19,561		20,245
Total costs incurred	$	555,782	$	1,348,904

^(a) Includes costs incurred whether capitalized or expensed.