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

3 Months Ended

Mar. 31, 2016

Extractive Industries [Abstract]

Costs Incurred for Property Acquisition, Exploration and Development

	Three Months Ended March 31, 2016		Year Ended December 31, 2015
	(in thousands)
Acreage purchases	$	5,341	$	73,025
Development		120,903		708,268
Exploration:
Drilling		9,097		87,505
Expense		4,223		18,421
Stock-based compensation expense		690		2,985
Gas gathering facilities:
Development		848		13,337
Subtotal		141,102		903,541
Asset retirement obligations		1,015		22,184
Total costs incurred	$	142,117	$	925,725

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