Properties and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2015

Property, Plant and Equipment [Abstract]

Components of net property and equipment

Properties and equipment, net are comprised of the following:

	December 31,
(In thousands)	2015			2014
Proved oil and gas properties	$	8,821,146		$	7,984,979
Unproved oil and gas properties	390,434			492,208
Gathering and pipeline systems	243,672			241,272
Land, building and other equipment	117,848			109,758
	9,573,100			8,828,217
Accumulated depreciation, depletion and amortization	(4,596,221		)	(3,902,506		)
	$	4,976,879		$	4,925,711

Schedule of net changes in capitalized exploratory well costs

The following table reflects the net changes in capitalized exploratory well costs:

	Year Ended December 31,
(In thousands)	2015			2014		2013
Balance at beginning of period	$	10,557		$	—	$	10,390
Additions to capitalized exploratory well costs pending the determination of proved reserves	—			10,557		—
Reclassifications to wells, facilities, and equipment based on the determination of proved reserves	(10,557		)	—		(10,198		)
Capitalized exploratory well costs charged to expense	—			—		(192		)
Balance at end of period	$	—		$	10,557	$	—

Schedule of aging of capitalized exploratory well costs

The following table provides an aging of capitalized exploratory well costs based on the date the drilling was completed:

	December 31,
(In thousands)	2015		2014		2013
Capitalized exploratory well costs that have been capitalized for a period of one year or less	$	—	$	10,557	$	—
Capitalized exploratory well costs that have been capitalized for a period greater than one year	—		—		—
	$	—	$	10,557	$	—