Exploratory Costs (Tables)

12 Months Ended

Dec. 31, 2015

Extractive Industries [Abstract]

Schedule of Capitalized Exploratory Wells

The following table sets forth capitalized exploratory well costs and includes additions pending determination of proved reserves, reclassifications to proved reserves and costs charged to expense:

Years ended December 31, (in thousands)	2015			2014			2013
Capitalized exploratory well costs at beginning of period	$	119,439		$	57,600		$	79,791
Additions pending determination of proved reserves	634,908			946,751			421,599
Reclassifications due to determination of proved reserves	(650,759		)	(882,254		)	(442,909		)
Exploratory well costs charged to expense	—			(2,658		)	(881		)
Capitalized exploratory well costs at end of period	$	103,588		$	119,439		$	57,600

The following table sets forth capitalized exploratory wells costs:

(in thousands)	December 31, 2015		December 31, 2014
Exploratory wells in progress (drilling rig not released)	$	1,760	$	18,781
Capitalized exploratory well costs for a period of one year or less	101,828		100,658
Total capitalized exploratory well costs	$	103,588	$	119,439